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- Front Matter: Volume 6832
- Photonics Crystals
- Digital Holography I
- Diffraction of Nanostructures
- Diffraction and Micromanipulation
- 3D Imaging and Displays
- Diffractive Optical Elements
- Grating Fabrication
- Digital Holography II
- Volume Holograms
- Applications I
- Applications II
- Poster Session
Front Matter: Volume 6832
Front Matter: Volume 6832
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This PDF file contains the front matter associated with SPIE Proceedings Volume 6832, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Photonics Crystals
Enhancement of external quantum efficiency of LEDs by fabricating photonic crystal in ITO p-contact layer
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Light-emitting diodes (LEDs) have the potential to become the main light source for the advantages of low energy
consumption, being environmental friendly and long lifetime. However so far the brightness of LEDs is not sufficient for
many applications due to low light extraction efficiency resulted from total internal reflection of the emitted light at
semiconductor/air interface. To overcome this problem, fabricating 2-dimensional photonic crystals (PhCs) on the
surfaces of LEDs is considered as one of the most effective ways. At present, the method of fabricating PhCs is primarily
through e-beam lithography and ion-beam etching. Such processes are complicated and unsuitable for low cost mass
production. In this paper we propose a novel method of using holographic and wet etching processes to fabricate PhCs in
p-contact ITO layers of LEDs. The PhC patterns are firstly fabricated in photoresist layers coated on LEDs, using
holographic approach, then acid solution are used to transfer the patterns into ITO layers. The experiments of adopting
different etching solutions and etching rates were carried out and the results were compared, in order to find out the best
etching condition. Experimental results demonstrate that solution HCl : HNO3 : H2O made less damage to photoresist
mask and can better control the etching depth in ITO. PhCs with different lattice constant and depth were fabricated to
obtain the best PhC parameters for higher light extraction. 30% increase of external quantum efficiency has been
achieved in the experiment.
Photonic bandgap properties of nanostructured materials fabricated with glancing angle deposition
Show abstract
Glancing angle deposition (GLAD) is a thin film fabrication method providing dynamic control over the
internal columnar microstructure of the deposited film. Using the GLAD technique it is possible to control the porosity
of the coating allowing precise tailoring of the optical properties. Therefore, in a single material system, the refractive
index profile of the film can be engineered to create a variety of multilayer structures. The focus of this research is on the
optical properties of these structured thin films. When the structure is periodic, incident radiation is subject to
constructive and destructive scattering which lead to photonic bandgap effects. Also of interest are the optical properties
of aperiodic systems, such as the Thue-Morse multilayer, which are deterministic but non-periodic. The complex
structural correlations in aperiodic systems lead to interesting bandgap-like properties. Applying the GLAD technique,
periodic and aperiodic optical lattices are fabricated with titanium dioxide, a dielectric material commonly used in
optical coating devices. The bandgap properties of these systems are investigated using transmittance spectroscopy and
transfer matrix calculations.
Holographic femtosecond laser processing by use of a liquid crystal spatial light modulator
Show abstract
Parallel femtosecond laser processing using a computer-generated hologram displayed on a spatial light modulator is
demonstrated. The use of a spatial light modulator enables to perform an arbitrary and variable patterning. This
holographic femtosecond laser processing has advantages of high-speed and high light-use efficiency. A critical issue is
to precisely control the intensities of the diffraction peaks of the computer-generated hologram. We demonstrated some
methods for the control of diffraction peak intensity. We also demonstrate the laser processing with two-dimensional and
three-dimensional parallelism using the Fourier hologram.
Fabrication of metallic 2D photonic crystals by holography
Show abstract
Photonic crystals are emerging as new generation devices with lots of promising applications. Holographic
fabrication of photonic crystals has become choice of many due to its associated flexibility. The paper
reports about our efforts on holographic recording of various 2-D periodic structures in photoresist material
and conversion of these to metallic structures, through electroforming. A He-Cd laser (442 nm) was used to
record the basic diffractive structures by two beam interference technique. These types of structures can
exhibit specific bandgap behavior and endurance in high power laser applications.
Digital Holography I
Improving reconstruction with optical diffraction field in Fresnel digital holography
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We present an analysis of the reconstruction through any intermediate plane by using the cascaded Fresnel diffraction
integrals. The realization of the integral with the single fast-Fourier-transform (FFT) imposes inherently the constraints
on the pixel resolution and the field of view of the computation window in the intermediate plane. On the other hand,
according to the optical diffraction field of the band-limited object, the size of the diffraction field including most
energy exhibits a change with the intermediate plane in a different way. Since the field of view of the computation
window is usually smaller than the corresponding optical diffraction field, then the simply cascaded FFT-Fresnel
diffraction integral algorithms will lose the resolution and degrade the image quality. It is proposed to improve the
reconstruction by compensating the field to be close to the optical diffraction field and using the new field as the
computation window in the intermediate plane. The numerical simulation and the experimental data-based calculation
are performed and demonstrate our proposal.
Comparison of reconstruction algorithms in lens-less Fourier transform digital holography
Show abstract
The different reconstruction algorithms are investigated and the reconstructed images are presented in lensless Fourier
transform digital holography. The most employed three algorithms, all based on the fast-Fourier-transform, are: the
convolution algorithm, the angular spectrum algorithm, and the Fresnel algorithm. With the convolution algorithm and
angular spectrum algorithm, there is an optimal reconstruction distance where the pass-band range of the transfer
function is the largest. Then the whole reconstructed image with the highest resolution can be acquired. When the
distance is different from the optimal distance, the size of the reconstructed image may vary with the distance and may
disappear from the field of view in some cases. In order to obtain the whole image, two methods are proposed. However,
at this time the resolution of the reconstructed image becomes lower. When the distance is smaller than the optimal
distance, the whole image can be obtained, but the resolution of the image also decreases. The Fresnel algorithm is
performed by using a single fast-Fourier-transform. With Fresnel algorithm, the same reconstructed images can be
obtained with the different reconstruction distances and the reconstruction is better than with the convolution algorithm
and the angular spectrum algorithm.
Study on the digital phase hologram and its wavefront reconstruction
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Based on the traditional basic theory for the making of the phase hologram, the digital phase hologram is studied in this
paper. The experimental results demonstrated that, in the forming of digital phase type hologram, there exists a
constituent parameter that corresponds to the exposure time of the traditional phase type recorded by holographic plate.
By choosing the proper constituent parameter, the object wavefield can also be reconstructed from the digital phase
hologram. In this paper, the forming of the digital phase hologram and how to choose the constituent parameter are
presented, finally, the comparison between the digital amplitude holograpy and digital phase holography in theory
simulation under the same condition and the experiment verification are given out.
A method for compressing off-axis digital hologram with spectrum shifting
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Large amounts of communication bandwidth and memory space is occupied to transmit and store digital hologram on
account of its enormous data volume. It is necessary to compress the information of digital hologram for effective
transmittance and storage. After theory of off-axis hologram is studied, it is found that at most half of the information is
useful for reconstructing image. A new method is proposed to compress the information, according to the spectrum
character of off-axis hologram. The sampling frequency is reduced by shifting the useful information of digital hologram
from high-frequency section to low-frequency section. Therefore, the information is compressed. The detailed procedure
is expressed as follows. (1) To filter the hologram with a high-pass filter, whose cut off frequency is equal to the
difference between frequency of reference beam and the highest frequency of object beam. (2) To multiply every row of
the filtered hologram by a cosine sequence, whose frequency is equal to the difference between frequency of reference
beam and the highest frequency of object beam. (3) To filter the processed hologram with a low-pass filter. (4) To
subsample the hologram with a sampling frequency as four times as the highest frequency of the object. As thus, the
digital hologram is compressed to half size of the original one at least. Moreover, higher compression rate will be
obtained if the subsampled hologram is compressed with other methods. The theoretical analysis and experimental
results are presented.
Surface contour measurement by LC-SLM digital phase-shifting holography
Show abstract
Surface contouring by digital phase-shifting holograph system based on the LC-SLM is proposed in the paper. Special phase-shift is introduced in the reference beam by changing code pattern displayed on the LC-SLM. And the reconstruction quality of complex amplitude of object wave has been improved greatly. The surface contouring measurement can be realized by means of phase change introduced by rotating the object beam.
Diffraction of Nanostructures
Study on phase characteristics of subwavelength metallic holes
Show abstract
Phase modulation characteristics of subwavelength metallic square holes are investigated for 2D imaging purpose. Based
on Maxwell equations, the transmission model of three-dimension subwavelength metallic holes is founded by a mode
expansion technique. The relationship between the widths of the holes and the phase from -π to π is established when the
thickness of metallic film is given. Then the influences of coupling electromagnetic (EM) fields as well as the incident
angle on phase retardation are investigated and calculated through varying the center distance between double holes. A
slab lens is demonstrated by using hole-array formed on a metallic film, which verifies the theoretic analysis.
Mechanism of coupling and interference in nano-slit
Show abstract
Electromagnetic diffraction of optical waves at a subwavelength aperture becomes a focus of recent research interest in
order to explain theoretically and experimentally the transmission enhancement of arrays of nano-size holes in metallic
screens. Some theories propose that the surface waves exited at a subwavelength aperture by diffraction is propagated to
the neighboring aperture and interfered with the incident optical beam at that aperture, resulting in enhancing or
suppressing of the transmitted energy through the aperture. In those theories one considers implicitly the interference of
the two waves in the exit side of the aperture. However, in the entrance side of the aperture we note that the surface
waves and the incident beam have perpendicular wavevectors and orthogonal polarizations before being coupled into a
slit. It is then important to investigate how this interference occurs with mediation of mutual conversion between the
surface waves and bulk waves at the nano-slit.
We find that a part of the surface wave energy scattered by the slit edge leaks into the slit and induces diagonal
electrical charge dipole, which radiates new bulk waves and surface waves on the slit's side-walls. Multiple reflection
Fabry-Perot resonators are formed in both horizontal and vertical directions over the slit, depending on the slit's width
and depth. We demonstrate the hypothetic interference between the fields induced by the surface waves coupled into the
slit and the normal incident wave, which induces also electric dipoles and new surface waves at the slit. Our calculation
fits well with the experimental results. The work is significant for development of the optical diffraction theory on the
metallic nano-size apertures.
Diffraction and Micromanipulation
Biochemistry nanosensor based on hybrid metallic nanostructure array
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A biochemistry nanosensor based on hybrid metallic nanostructure array was put forward in this paper. The hybrid
metallic nanostructure array consists of two types Ag nanostuctures, spherical and pyramidal structures with the same
period. A biochemistry sensor experiment is demonstrated by detecting the transmittance spectra of hybrid metallic
nanostructure using Sciencetech spectrophotometer. The wave peaks of transmittance spectra have shifts when the
metallic periods and the refractive index of Ag nanostuctures are different.
Generation of vector beams and their focal properties
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We describe a convenient way to generate arbitrary vector beams by using a spatial light modulator, based on
interferometric superposition of two orthogonally polarized beams. In our constructed optical setup, the SLM is used to
produce a computer-generated holographic grating that diffracts a linearly polarized incident light into the +1st and -1st
diffraction orders with desired wavefronts. After the two diffraction beams pass through two quarter wave-plates, the
left- and right-handed circularly polarizations are yielded, respectively. Then a Rochi grating is utilized to recombine the
two beams into single one such that any desired polarization configuration is achieved. We demonstrate the versatility of
our method through optical experiment, in which a variety of polarization beams are realized. By making use of the
incident wave with helical phase, our technique can produce both cylindrically symmetric and asymmetric polarizations.
To the best of our knowledge, the experimental realization of cylindrically asymmetric polarization is reported for first
time. We also study the focal properties of vector beam through a high numerical aperture lens. Starting from
Richards-Wolf vectorial diffraction theory we calculate the focal field distribution and obtain some interesting focal
volume structures, such as flat-topped focus, doughnut focus with special dark volume structure.
Generation of phase-shift patterns in the optical far field and its applications
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We introduce and compare two methods to produce the phase-shift patterns, which are widely generated in the near-field
lithography, in the optical far field. The key component of the two methods is a phase-only diffractive optical element, a
similar function found in the maskless lithography. The technique to produce a smaller feature size was a major
improvement beyond the diffraction limit.
Transverse optical trapping of spherical particle with strong absorption in a focused Gaussian beam
Show abstract
In this work, the transverse optical trapping of spherical particle with strong absorption is studied in geometrical optics
model by numerical simulation. In our work, the exact expressions of wave vector are used instead of traditional
approximate expressions, and the transverse optical trapping force acting on a spherical particle due to strong absorption
is calculated when the particle is illuminated by a focused Gaussian beam of TEM00 mode. The calculated results show
that stable transverse optical trapping positions only exist when the center of the spherical particle is located in front of
the focus of the beam. Our results also reveal that the trapping positions are decided by the radius of the beam waist ω0.
The magnitude of transverse optical trapping force and the stiffness of optical trapping decrease with the increase in ω0.
Evaluation of fiber coupling coefficient by a deformed cell in dual-beam optical stretcher
Show abstract
The dual-beam fiber-optic stretcher has been used for studying cell's viscoelastic properties under optical radiation pressure [1, 2]. In this paper we study the coupling from one fiber to another by a Red Blood Cell swollen to a spherical shape, and captured by the two countpropagating laser beams. First, we compute the photonics force distribution on the cell's surface using the ray optics, and then the deformation of the cell using the mechanics of the linear membrane theory of thin shell. Finally, we compute the coupling coefficient between the two fibers by the deformed ball lens of ellipsoidal shape. As the cell acts as a thick lens here, its spherical and defocus aberrations are estimated and included in the calculation of the coupling coefficient [3]. This technique could allow obtaining the visco-elasticity of a large number of cells by rapidly measuring the light coupling efficiency as a function of the laser beam power and the fiber end-to-fiber end separation, but without imaging and measuring the cells deformation.
3D Imaging and Displays
Optical scanning holography: a review of fundamentals
Show abstract
In this invited paper, I will first review some of the fundamentals of optical scanning holography. I will then include
some of the recent publications on optical scanning holography.
Color laser holographic display of virtual 3D scene
Show abstract
In this paper, a new method, which synthesizes the technology of computer graphics (CG) and holographic integral
photography, is proposed to realize the holographic display of virtual 3D scene in large size. In this method, elemental
stereographic images of 3D scene are computed by a virtual holocoder instead of using pickup process. And then, the
color of elemental stereographic images is separated by computer and three tricolor elemental image series are printed by
high graphics printer. The printed image series can be integrated into the previous 3D scene with a lens array whose
optic parameters match to the virtual holocoder. If the image series are illuminated by laser, the virtual 3D scene is
reconstructed by coherent light, and then the reconstructed scene can be recorded by single wavelength color holographic
technology in large size.
Application of bi-grating diffraction imaging on the display of ordinary transmission hologram with white light source
Show abstract
The comparison of bi-grating diffraction imaging and the displaying of ordinary transmission hologram with white light
source, shows two different imaging methods have same essence, but different characteristic. In these two processes of
imaging, the light-wave of the object has been diffracted twice, both methods have to combine the dispersed image of
different wave length, so both of them have to employ the spectral combination characteristic of grating. The bi-grating
imaging equation not only is fit for the bi-grating imaging process, but also has guidance meaning in ordinary
transmission hologram displaying with white light source and the aid of grating.
Talbot grating for color separation in color liquid crystal display
Show abstract
The backlight unit should be used to illuminate the liquid crystal display (LCD) panel, and the typical light throughput
is around 5% for the color LCDs. This insufficient light efficiency is predominantly related to the use of the color
filter. In this paper, a three-step Talbot grating based on the fractional Talbot effect to realize the color separation in
the color LCD is proposed in order to increase the light efficiency. Simulation shows that, when the incident light is a
uniform plane wave, the light efficiency of 85% is obtained, which is far higher than that of using color filter's 33%
theoretically. This design is insensitive to the displacement along the direction of the movement of color separation
plane and the change of RGB wavelengths, and it is also insensitive to the grating's steps height. In addition, the
Talbot grating is feasible for fabrication.
Diffractive Optical Elements
Scheme of real-time Dammann grating based miniaturized three-dimensional endoscopic imaging system
Show abstract
A real-time miniaturized three-dimensional endoscopic imaging system basing on Dammann
grating array illumination is proposed. The system consists of two endoscopic channels that one
channel is used to project an array structured light generated by Dammann grating on an object
and the other is used to obtain images from the object to measure its surface profile. Using the
special designed Dammann grating, it is very simple to generate an array structured light, couple it
into the endoscopic channel and project it on an object. The measured images are processed with a
standard image processing procedure and the surface profile is extracted by Fourier transform
profilometry algorithm. With the development of computer hardware and fast image processing
algorithms, the imaging system can acquire real-time data and dynamically process
three-dimensional measurements. The system was evaluated in 3-D measurements of several
objects with known geometries. The results show high accuracy of the imaging system and its
potential applications in clinic and biology research.
Transmission polarizing beam splitter of deep-etched silicon grating
Show abstract
A subwavelength transmission polarizing beam splitter (PBS) of deep-etched binary silicon grating at wavelength of
1550 nm is described, and TE-polarized and TM-polarized waves are mainly diffracted in the -1st and 0th orders,
respectively. In order to achieve high extinction ratio, the grating depth and period are optimized using the rigorous
coupled-wave analysis (RCWA). And the maximum extinction ratio of the rectangular PBS grating can reach 301.97
with the optimum grating period of 1291 nm and depth of 2.04 μm, the efficiencies of TE-polarized wave in the -1st
order and TM-polarized wave in the 0th order are 60.07% and 73.09%, respectively. Holographic recording technology
and inductively coupled plasma (ICP) etching could be used to fabricate the silicon PBS grating. Though the diffraction
efficiency of the silicon PBS grating is not so high, since the silicon material is widely-used and easy to obtain; the
grating structure is compact and the fabrication technology of this material is well established for mass production, the
deep-etched silicon transmission PBS grating should have potential applications in optical communication systems.
Study on encoding technique of phase-shifting unit based on LC-SLM
Show abstract
Phase-shifting is one of key technologies in the digital holography or interferometry. Exact and stable phase shifts play
an important role in the experimental results. Computer-generated holograph phase-shifting unit based on LC-SLM can
produce phase shift with repeatable and high stability. In the system, it is very crucial to encode the computer-generated
holograph on LC-SLM. This paper investigates phase-shifting precision and stability as well as diffraction efficiency by
using various encoding methods in theory and experiment. The work in the paper establishes foundation that
computer-generated holograph phase-shifting unit based on LC-SLM can be applied in the digital holography and
interferometry system.
Design of diffractive beam shaper for transforming a Gaussian beam to a squared uniform beam
Show abstract
In this paper, we design phase-only and quantized diffractive optical elements to transfer a field with circular Gaussian intensity distribution to an expanded squared uniform distribution based on the Fresnel diffraction theorem. The simulated annealing algorithm was used to design these elements. Many different cost functions were defined, applied and compared in this algorithm. Besides, we found that dark area expansion in the target patterns can improve the uniformity of designed results. However, there are no improvements when the bright area is smaller than an eight in one dimension of the total diffraction field. In addition, the uniformity can be improved at the expense of decreased diffraction efficiency.
Grating Fabrication
Fabrication of 200 nm period x-ray transmission gratings using electron beam lithography
Show abstract
X-ray transmission gratings (TG) have attracted much interest because of its wide use in x-ray
telescope, synchrotron radiation facilities, and target diagnostic in inertial confinement fusion, etc. In
this work, a 200 nm period master TG to diffract x-ray in the energy range 0.1-8keV has been
successfully fabricated by electron beam lithography followed by gold electroplating. In fabrication
processes, 500 nm resist was exposed by focused electron beam on polyimide free-standing-membrane
coated with a Cr/Au plating base. According to numerical simulation, the proximity effect due to
electron back-scattering from the substrate can be sharply reduced because of the thin polyimide
free-standing membrane substrates. PMMA resist was chosen due to its high resolution and good
performance in subsequent processes. After delicate dose test and shape modification of the proximity
effect caused by electron front-scattering, resist grating bars with 95 nm width and 200 nm period were
achieved. Subsequently, resist patterns were transferred to gold layer by electroplating. In future work,
with this master mask of TG, thousands of TG to diffract x-ray can be sufficiently replicated using
x-ray lithography.
A method to fabricate convex holographic gratings as master gratings for making flat-field concave gratings
Show abstract
Ion-beam etching blazed flat-field concave diffraction gratings (FFCG) to achieve high diffraction efficiency is a
difficult task. This paper presents a new method to fabricate convex holographic gratings as master gratings for making
FFCG. This method makes it convenient to fabricate blazed FFCG with corrected aberrations and uniform predetermined
blaze angle over the grating surfaces. It can also be adapted to the commercial fabrication process. This method could be
briefly described as follows: First, we make a convex grating using holographic recording method. The grooves are
determined by the interference fringes of two spherical waves, one of which is divergent coming from the back side of
the substrate, and the other is convergent coming from the front side. Leading-term aberrations can be corrected by
optimizing the center positions of the two sphere waves. Second, the exposed convex grating is etched by ion beam to
make a blazed convex grating. In this step, it is much easier to get a uniform blaze angle over the surface of a convex
grating than over the surface of a concave grating. At last, the etched convex grating is used directly as a master grating
to replicate blazed FFCG. An optimized example for a specific system structure is given in this paper. The advantages
and difficulties of the method are discussed.
Study on the fabrication of low-gradient photoresist grating masks
Show abstract
To alleviate the difficulty of ion beam etching, it is essential to acquire the low gradient holographic photoresist grating
masks as well as the high gradient ones (i.e. the rectangular holographic photoresist grating masks). According to the ion
beam etching experiments, the low gradient photoresist grating masks can effectively eliminate the redeposition. The
control of the profile of holographic photoresist grating masks is investigated in this paper. Considering the effects of
developing time and temperature of the developer on the response of photoresist and adopting the combination of
computer simulation and experiments, a low gradient photoresist grating mask: 30% duty cycle at bottom and 65°
gradient can be fabricated. The study indicates the increase of the developing time causes the diminish of the threshold
volume of exposure while the increase of the slope of the linearity of photoresist response; the rise of the temperature of
the developer leads to both the increase of the threshold volume of exposure and the slope of the linearity of photoresist
response. As a result non-1:1 interferential exposure and low-temperature development are required in the fabrication of
low gradient photoresist grating masks. The 1:7 interferential exposure and 15°C- development have been adopted in this
experiment.
The investigation of the effect of recording conditions on grating formation in a novel holographic photopolymer
Show abstract
Holographic photopolymers become promising materials for future production of holographic devices. And the
mechanism of hologram formation in photopolymers has been broadly studied. In this paper we present a simplified
model in order to describe the monomer diffusion and photopolymerization. According to this model, the main effect the
modulation of refraction index comes from the intensity of recording beams and fringe spacing during recording. So we
quantitatively analyzed the effect of recording intensity and fringe spacing on diffraction efficiency, and carried out
validating experiments with a novel blue-green sensitized photopolymer. Holographic gratings were recorded with
different recording beam intensities and different fringe spacing respectively, and corresponding diffraction efficiency
were obtained. By fitting the experimental results to the model, we obtained the material parameters, such as diffusion
time constant, polymerization coefficient. The experimental results indicated that a higher recording intensity resulted in
a faster growth of grating and lower saturated diffraction efficiency. And saturated diffraction efficiency increased with
the increasing of fringe spacing. These agreed well with theoretical expectation. This study improves the understanding
of recording process and consequently allows building more accurate holographic components in the photopolymers.
The study and application of dual-wavelength (red and blue) sensitive water-resisting photopolymer
Show abstract
The holographic storage characteristic of a new kind of water-resisting photopolymer is studied; and studied it's photoperceptivity and application in many aspects. The photopolymer is composed of two
dyes which is sensitive to red and blue wavelength. This kind of photopolymer is water-resisting and its
post retreatment is simple. The volume shrinkage mass of this material is also small. We have used this
material to make gratings successfully; we settled the problem of spreading this photopolymer to soft film for storage.
Digital Holography II
Imaging technique for three-dimensional microstructure by digital holography
Show abstract
Digital holography is a whole-field, non-contact, and highly sensitive interferometric imaging and testing technology. It
is more suitable for microscopic measurement owing to digitalization and flexibility in holograms recording, storage,
reconstruction and transmittance. This paper analyzes the factors which lead to the phase aberrations in the off-axis
lensless Fourier transform digital holography firstly. Then a method, which is obtained by borrowing ideas from T.
Colomb, is presented to correct the phase aberrations automatically during the numerical reconstruction. This is
implemented by multiplying a phase mask directly with the reconstructed wave field. The phase mask is obtained by an
iterative procedure computing automatically without the pre-knowledge of the physical parameters, such as the off-set of
the reference point source and the recording distance. This method enables one to reconstruct the relative correct and
accurate phase-contrast image, even in the presence of the noise, which is needed to be smoothed by a median filter. In
order to achieve an accurate phase image, the procedure described here is applied iteratively, starting from the initial
values provided by the first evaluation. We present and analyze the simulation results of the phase images based on a
special three-dimensional micro object. The results show that for a weak noise the above method is very effective; while
for strong noise the common phase-unwrapping method must be applied. This indicates that it is very important to record
high quality hologram and to suppress the noise in phase data.
Low-density microporous polymeric foams measurement with digital microscopic image plane holography
Show abstract
A method for the measurement of low-density microporous polymeric foams with digital microscopic image plane holography is studied. An image plane hologram of microporous foam is recorded in an optical system of a Mach-Zender interferometer by CCD sensor, and the magnified image, which contains the quantitative information of the intensity and the phase of the microporous foam, is reconstructed numerically from the captured single interference pattern by twice
fast Fourier transform and digital filter processing of frequency spectrum. And the morphometry and the pore diameter of
the microporous foam under test can be obtained. A theoretical analysis has been performed and experimental results of
the polymeric foam are also given. The experimental results show that the method presented in this paper is feasible,
easy in data processing.
A sample test on the tilt angle of object light illumination in digital holographic 3D surface shape detection
Show abstract
This paper discussed the measurement error of digital holographic 3D surface shape caused by imprecise measurement of the incident angle and the tilt angle of object light illumination in theory. The result showed that the error caused by the tilt angle is much greater than the incident angle. Then a method to accurately calculate the object light's tilt angle by detecting the interference field of reference plane is proposed based on the above discussion. Finally, the feasibility of the method is proved through a 3D surface shape detection experiment.
Lateral resolution of digital holographic system
Show abstract
Based on Fresnel diffraction theory, the point spread function (PSF) of the off-axis lensless Fourier transform digital
holographic system with pre-magnification is deduced for the first time to the best of our knowledge. The limited lateral
resolutions of the digital holographic systems with and without pre-magnification are analyzed in detail. For lensless
Fourier digital holography, the expression of the limit resolution is obtained by use of Rayleigh resolution criterion and
the PSF of this system. The obtained resolution is different from others in coefficient. Moreover, we propose new
recording conditions with which the higher resolution can be achieved. The experimental results of a USAF test target
demonstrate the correctness of the theoretical analysis about the lensless Fourier digital holography. For digital
holography with pre-magnification, the limit resolution is also analyzed in detail. The results show that the imaging
resolution is associated with the parameters of MO and CCD, the recording condition and the light wavelength. If the
imaging resolution of CCD is higher than that of MO, the resolution of the whole system is dependent on the numerical
aperture of MO. On the contrary, the resolution is dependent on the imaging resolution of the CCD. It is best to make the
imaging resolution of MO approach the resolution limitation and the imaging resolution of CCD equal to or higher than
the resolution of MO slightly, which can be implemented by decreasing the distance between the object and MO and
decreasing the recording distance properly. The simulation results indicate the correctness of the theoretical analysis.
Automatic compensation for phase aberration in digital holographic microscopy
Show abstract
Based on the point spread function of the off-axis Fresnel digital holographic system with pre-magnification, the phase
aberration introduced by microscope objective is obtained. Using a collimated light as reconstructing wave, the phase
aberration introduced by the difference between the reconstructing wave and the reference recording wave is analyzed.
This method is very simple, and it is very different from the one proposed by T. Colomb et al. The phase mask that can
be used to compensate automatically the phase aberration in the phase reconstruction is obtained. According to the
principle of digital holography, it must be pointed out that for Fresnel digital holography, the recording distance must be
determined accurately before compensating automatically the phase aberration. This is done by an automatic focusing
procedure, which is based on image-gray-entropy-method. The simulation result for a special three-dimensional micro
object, which is polluted by a random noise, is presented. The percentage error of the reconstructing distance obtained by
the focusing procedure is below 0.6 for SNR = 25. Then an automatic aberration compensation procedure, which is the
same as that one proposed by T. Colomb et al., is applied to reconstruct the phase image. The results show that for a
weak noise the above method is very effective; for a stronger noise the procedure described here is applied iteratively,
starting from the initial values provided by the first evaluation; while for a very strong noise the procedure fails at all.
Moreover, after applying a median filter to the primary reconstructed phase image, the aberration of the phase image
obtained by further iteration decreases, at the same time the noise is strengthen.
Volume Holograms
Study on water-resisting photopolymer holographic recording material
Show abstract
We explored the reaction mechanism of the dual-wavelength water-resisting photopolymer. The
photosensitive material which was sensitive to red and green light was synthesized, using the complex
photo sensitizer. The photosensitivity was improved and the scope of the photosensitive spectrum
was broaden. We also studied the influence of the ingredient on the holographic performance of the
polymeric material. Further studies on the influence of the solution preparation on the quality of the
hologram was made, too. The appropriate exposure time and disposal way were obtained through
experiments. The experimental result indicates that this hologram of the dual-wavelength water-resisting photopolymer is damp-proofing and non-active. It is easy to preserve in any
environment. It needn't chemical treatment to manufacture hologram applying this prescription. The
diffraction efficiency would be increased obviously by heating. Providing ideal storage material to the
manufacture of the holographic element, the prospect of the appplications would be more extensive.
Angle amplifier based on multiplexed volume holographic gratings
Show abstract
Angle amplifier of laser beam scanner is a widely used device in optical systems. Volume holographic optical elements
can be applied in the angle amplifier. Compared with the traditional angle amplifier, it has the advantages of high angle
resolution, high diffraction efficiency, small size, and high angle magnification and flexible design. Bragg anglewavelength-
compensating recording method is introduced. Because of the Bragg compensatory relation between angle
and wavelength, this device could be recorded at another wavelength. The design of the angle amplifier recording at the
wavelength of 514.2nm for the working wavelength of 632.8nm is described. An optical setup for recording the angle
amplifier device is designed and discussed. Experimental results in the photorefractive crystal Fe:LiNbO3 demonstrate
the feasibility of the angle amplifier scheme.
Volume holographic wavelength filters based on transmissive-writing and orthogonal-readout scheme
Show abstract
Owing to the high Bragg selectivity and capacity of multiple recording, volume holography has been widely investigated
for devices such as wavelength filters in wavelength-division multiplexing fiber communication systems in recent years.
Transmission-Writing and Orthogonal-Readout scheme (TWOR) has been proposed for making wavelength filters in
holographic media. In this paper, experiments on wavelength selectivity of volume gratings with TWOR scheme are
successfully conducted for the first time to our knowledge. Readout by wavelength-tuning showed that a 3-dB bandwidth
of 0.5nm was achieved. The experimental results agreed well with the expectation of 2-D coupled-wave theory, and
verified the feasibility of TWOR scheme.
Design and characteristic test of the KDP crystal gamma63 transversal modulator in optical communication
Show abstract
According to the theory of electric-optical effects to design the slice pattern, size and the appropriate combination of chip,
the γ63-transversal electric-optical modulator (pockells box) of KDP crystal is designed in the article. The high semiwave
voltage of KDP crystal (~8000V) will be decreased to several hundred voltages which can be used in practical
application and the temperature stability of this electric-optical modulator is improved. The experimental result shows
that the signal transfered by laser is not affected with the changing of the working temperature of this electric-optical
modulato. While the He-Ne laser (λ=0.6328μm)is used to the communication, the semi-wave voltage will be reduced
to 687.5V practically and the coefficient of eletric-optical is γ63=11.98×10-12m/V. It is consistent with the theoretical
value.
Applications I
Beam deflection measurement using Moire effect and Talbot interferometer
Show abstract
This paper introduces a new and simple concept of moire effect. A circular grating placed at Talbot planes can achieve
beam deflection measurement in real time. It is not only used for 2-D beam shift measurement at every point, but also
used to measure the angle and plane parallel degree of optical element and birefringence measurement of the optical
material.
An improved system for measuring the SNR of holographic anti-counterfeiting labels
Show abstract
This paper presents a new method to measure the characteristic parameter of the laser holographic anti-counterfeiting
label, with less dependency on the stability of source light. The He-Ne laser, having 5% relative instability, was used as
the light source. Based on the nature that one beam of light can be divided into two beams at a fixed ratio, the source
light was divided into the reflex and the transmission at the fixed ratio by a piece of glass. As the label was scanned
automatically, the intensities of the reflex and the diffraction were measured online and in real time to get the SNR. The
data table for contrast was given, which showed the differences between the real value and the calculated value of the
intensity of the transmission as the incident beam. The measurement results of the SNR of 8 different versions of labels
were also listed. The experimental data demonstrate that the relative error of the transmission intensity is not more than
0.29%, and that of the SNR is less than 2.0%, which is approximately half the error of the original method.
Encrypted Fourier holographic data storage with variable data reference wave for optical information security
Show abstract
In this work two liquid crystal spatial light modulators (LCSLMs) were applied to encode a reference beam
and holographic storage of a set of encrypted data pages that formed the object beam. The SLMs were
developed by converting two 84×48 pixels mobile phone displays and were set in transmissive mode.
Fourier holograms were recorded in a red sensitive photopolymer emulsion (SM635C of POLYGRAMA,
Brazil), coated on a glass substrate. While replay the reconstructed data page, recorded against a specific
reference beam was captured by using a CCD camera and processed in a personal computer for decryption.
The encoded reference beam forms a unique key to the individual hologram recorded through shift
multiplexing. Diffraction efficiency of holograms was calculated and was found to be about 45%. The
system offers a very cost effective solution for secure data storage and retrieval and can be used for storing
valuable software, security documents etc.
A multi-beam holographic light concentrator for solar applications
Show abstract
High efficiency solar cells are emerging as a viable tool for tapping solar energy. Such cells need cool light
to be concentrated on them for high conversion efficiency. Conventional refractive and reflective light
concentrators, with sun tracking systems, are bulky and heat the solar cell due to single focus convergence
of heat and light radiation. HOEs are emerging as an active candidate for making new generation light
concentrators. In this paper we report the design, development and characterization of a multi beam
reflection HOE for light concentration. The proposed design of single focus, multiple exposed reflection
element with wavelength selectivity can be used to avoid sun following system.
Applications II
Analysis of static coded-aperture imaging spectrometer
Show abstract
Scanning and interference imaging spectrometer are widely used in earth observing, microscope imaging, etc. Motion
mechanisms are utilized in all these simple imaging spectrometers, which make the system big, expensive and unstable.
A novel static non-imaging spectrometer is introduced specifically. 2D (two-dimension) static multi-channel spectral
measurement is realized in this spectrometer, utilizing 2D hadamard matrix code mask and 2D detector. The hadamard
matrix is different from traditional S circular code. The orthogonal property of hadamard matrix is utilized, and with
special transform negative codes in hadamard matrix are also realized. Basing on this non-imaging spectrometer static
imaging spectrometer is developed. First 2D imaging spectrometer can be divided into many 1D ones which work
independently. The 1D imaging spectrometer is obtained with position information added into the hadamard coding
system in dispersive direction. To get 2D imaging spectrometer, extend the coded aperture: put some masks together in
non-dispersive direction. According to this model, the spectrum of an image instead of a slit can be estimated at one
time. The optical system is designed to simulate the imaging spectrometer. Compared to the simple scanning imaging
spectrometer the simulated result shows the model's resolution can be compared to simple scanning spectrometer, but
the scanning time of simple scanning imaging spectrometer is about 3 times of our simulation. At last some
implementation issues are mentioned.
Polynomial phase mask for extending depth-of-field optimized by simulated annealing
Show abstract
The cubic phase mask is an approximate theoretical solution for extension of depth-of-field (DOF) in the computational opto-electronic imaging system. In the practice, it does not provide an infinite depth of field. Especially the cubic coefficient needs to be determined for a given optical system and a requested extension of the DOF. Many other approaches using a variety of masks have been proposed. In this paper we propose a polynomial phase mask, which is still separable in the Cartesian coordinate system, as the cubic mask. The phase contains 16 terms of odd powers and was optimized by the simulated annealing. The cost function was designed for invariance of the MTF curves with a full range of depth-of-field of ±200 μm in a biomedical microscope. This number of polynomial coefficients provides the optimization with a necessary number degree of freedom. We introduced a target MTF to assist the simulated annealing, which was defined iteratively from the ideal MTF to a more practical and achievable target MTF. Our result is compared with that of the recently published approaches. The experimental results with digital restoration of images using the invariant MTF are also shown.
Research on improved image reconstruction algorithms of OCT based on incomplete projection data
Show abstract
In order to improve the quality and solve the problem of low speed of image reconstruction in the traditional optical computerized tomography (OCT) when the data acquired is incomplete projection, the multiple constrained of genetic algorithm based on algebraic iterative was proposed. Generally speaking, under the condition of multiple-objective optimization, the common extreme point for all the objective functions doesn't exist. So we can achieve the preferable compromise in the contradictions of multiple objectives. In this article, there are three constrained conditions. The first one is the maximum entropy criterion which is used mostly to solve the problem of OCT image reconstruction when the data acquired is incomplete projection recently. The second one is the minimum criteria of peak value which is introduced to suppress noise effectively and ensure the gliding property of the image reconstruction, because of the first one leading to noise amplification during the iterative process. The last constrained condition is the minimum criteria of the difference between the projection again of image reconstruction and the original projection. The concept of penalize-function is introduced into the genetic algorithm, which would transform the constrained optimization problem to unconstrained. It is clearly demonstrated from the experiment results that the algorithm reconstruction technique can efficiently improve the quality of images reconstruction of the incomplete projection data.
Optics and image processing techniques of one-step holographic stereogram
Show abstract
A method for producing one-step holographic stereogram is presented. Combining computer-based digital image
processing technology, two kinds of stereogram, made of slits or dots respectively, are discussed. The
stereogram produced can offer a combination of large viewing zone and minimal image distortion, depending on
alterable parameters in the image processing program. Hologram-recording experiments are carried out, and
then process and results are given. Since the techniques described are applicable to mass produce large scale
stereogram automatically, primary designing of stereogram-printing equipment, both 'slits' and 'dots' systems
are studied.
Poster Session
Transmission-type holographic screen for displaying projected three-dimensional images with large viewing angle
Show abstract
A new type of holographic screen used to display projected 3-dimensional (3D) images with large viewing
angle and relatively high brightness is presented. The screen is 2-dimensional hexagonal lattice relief in
micron-scale lattice period, fabricated in plastic sheet using holographic technique and pattern replication
method so that the fabrication of the screen is fast and cost effective and large-size screen can be obtained.
Theoretical analysis and experimental results demonstrate that larger lattice period generates more diffracted
rays thus provides larger viewing anlge and brighter image. 45° horizontal and 30° vertical viewing anlges
have been achieved and the images with parallax have been observed. The screen has the potential of being
applied for 3D holographic movie display and 3D art exhibition.
Multi-annular phase plate for extended depth-of-field imaging system
Show abstract
Extending the depth of field (DOF) of incoherent optical systems has been an active research topic for many years, and
the extended depth of field (EDOF) system can be used in many fields. We developed a novel circular pure phase plate
to extend the DOF by a factor of 4 without decrease of optical power in image plane. The plate is divided into several
equal-area annular zones and placed in the exit pupil of a standard optical imaging system. The annular zones alternately
eliminate the influence of different defocus beside the ideal Gauss object plane. The comparisons of the MTF and PSF
curves between two systems show that the system employing the phase plate has a large DOF while preserving an
acceptable resolution. Also, the images captured by the system don't have to be restored by a digital filter before next
processing. And the simulation of imaging a spoke target in several defocused condition also confirms the EDOF of the
imaging system. The DOF can be adjusted by two parameters of the phase plate: defocus compensation parameter and
zone number. We gave the relation curves between system's performances and parameters of the plate.
Polarization-based digital holography of Fresnel-zone-plate convolution without motion
Show abstract
The polarization-based digital holography of Fresnel-zone-plate (FZP) convolution without motion is proposed. This
method focuses mainly on imaging of two-dimensional objects embedded in highly scattering media. The key of the
method is that the uniformly distributed light source is utilized to make many FZP projections superpose on an object in
a classical incoherent correlator. In this way a hologram of the object is obtained by convoluting its intensity distribution
with the FZP intensity distribution without relative motion. A method called composite hologram is applied to improve
the low signal-to-noise ratio due to extremely weak signals submerging in large backgrounds. Especially, the
configuration of this method is designed to avoid time-consuming. The polarization gating is used in order to extract the
weakly polarized light from the highly scattered light. In experiments, the degree of polarization of circularly polarized
light is maintained better than that of linearly polarized light in highly scattering media. Circularly polarized light is,
accordingly, used in practice. The experiments on a 0.4-mm-diameter metal wire embedded in Intralipid-1% phantom are
carried out. The outline of the metal wire can be still distinguished, although the reconstruced image becomes blurred as
the thickness of cuvett increases to 30 mm. An attempt to apply this method to image the metal wire embedded in
chicken tissue sections also be implemented. The reconstructed images can be distinguished in depth of 10 mm. The
experimental results demonstrate that the method has potential applications in imaging of objects embedded in highly
scattering media.
Fabrication of holographic Fresnel lens used as a solar concentrator
Show abstract
One of the more intriguing of solar collection techniques, holographic concentration, has been addressed in many ways,
but it has so far met with only limited success. The major attraction of holography is that unlike conventional
concentrators, the holographic concentrator can track the sun across the sky while remaining completely stationary. A
simple system using holographic Fresnel lenses (HFLs) was proposed in this paper. We present the theoretical analysis
and the technique for fabricating HFLs used for solar concentrator. Several HFLs fabricated using corresponding
recording geometries, resulted in a combined device that collects light at any angle, with each lens responsible for
gathering sunlight for a certain portion of the day. Three HFLs with different fringe pattern were achieved, which
operates in the morning, at noon and in the afternoon, respectively. The primary experimental results of the concentrator
were presented, which effectively concentrates the visible spectrum over a 60 degrees daily angular variation. Several
advantages of the holographic concentrator we obtained include longer lifetime, low cost, and the small size of a flat
piece of film compared to a mirror or lens. The dispersive characteristics applied to photovoltaic power generation would
offer a novel type of generator with high conversion efficiencies.
Virtual display: unidirectional diffusing image screen for extension of screen region using mirror image
Show abstract
A liquid crystal display (LCD) recently comes into common use. It is possible for this display unit to provide the
same size of displaying area as the image screen on the panel. Thus the conventional display can show only one
screen, but it is impossible to enlarge the size of a screen, for example twice. To enlarge the display area, the
authors have developed an enlarging method of display area using a mirror. Our extension method enables the
observers to show the virtual image plane and to enlarge a screen area twice. In the developed display unit, we
made use of an image separating technique using polarized glasses, a parallax barrier or a lenticular lens screen for
3D imaging. However, each technique has a defect at viewing an image. In the glasses method, an observer
needs to wear the special glasses for a viewing screen. The slit or lens sheet reduces the resolution in half. To
solve these problems, we develop a new virtual display system using a unidirectional diffusing image screen.
3D imaging on virtual display with extended screen using mirror image
Show abstract
The conventional display can show only one screen, but it is impossible to enlarge the size of a screen, for example
twice. To solve this problem, the authors presented an enlarging method of display area using a mirror. Our
extension method enables the observers to show the virtual image plane and to enlarge a screen area twice. Although
the displaying region is doubled, this virtual display could not produce 3D images. In this paper, we propose a 3D
imaging display with an extended region using an angle-controlled unidirectional 4-views display.
Reflective mirror with holographic optical element for extension of screen region using mirror image
Show abstract
The conventional display can show only one screen, but it is impossible to enlarge the size of a screen, for example twice. Meanwhile the mirror supplies us with the same image but this mirror image is usually upside down. Assume that the images on an original screen and a virtual screen in the mirror are completely different and both images can be displayed independently. It would be possible to enlarge a screen area twice. This extension method enables the observers to show the virtual image plane and to enlarge a screen area twice. To enlarge the screen region twice, it is necessary to prepare a mirror. This mirror and the imaging plane of an original display must be placed at right angles to each other. Therefore, the mirrors take up much space in front of display. To solve this problem, we have developed a new reflective mirror using a holographic optical element.
Reconstruct three-dimensional image by two- wavelength digital holographic contouring
Show abstract
The reconstruction of digital hologram is a key topic in the research of digital holography, which is maturely
developed for the reconstruction of two-dimensional image. Recently, the reconstruction of three-dimensional
image has attracted much more attention. In this paper, we apply the two-wavelength digital holographic
contouring method to obtain the three-dimensional image, the basic idea of which is to reconstruct the shape
through the phase difference that can be numerically calculated by Fresnel diffraction algorithm. Considering
the fact that the obtained phase is wrapped on the interval (-π, π], and the unwrap algorithm always fails for
the object with large height steps or spatially isolated areas, we adopt the two-wavelength digital holography to
provide an equivalent longer wavelength such that the obtained phase is continuous everywhere. The experiment
results prove the feasibility and efficiency of the method.
Near-field diffraction analysis and simulation about nanoscale of Fresnel zone plate
Show abstract
In this paper, we calculated the numeric results of diffraction field in space of X-ray (λ=4.5nm) Fresnel zone plate based
on angular spectrum method, analyzed the axial and radial distribution patterns of X-ray Fresnel zone plate. The Full
Width at Half-Maximum (FWHM), Depth Of Focus (DOF) and Strehl efficiency of focus spot were studied. Discussed
the relationships between FPZ's design parameter and focus spot properties. At the condition of λ=4.5nm and the
outmost width Wn=50nm, the size of focus spot is proportional to the outmost width, and increase slowly with the
increase of number of zones and focus length; the DOF of focus spot increase at first; when the focus length increased to
40µm, the DOF incline to a constant; the focus spot's Strehl efficiency increased slowly with the increase of number of
zones and focus length.
Optical system with off-axis holographic lens group for fabricating large-size photonic crystals
Show abstract
In this paper, we propose an improved hologrpahic technique for fabricating 2D hexagonal and 3D hexagonal packed
photonic crystals (PhCs). The key element in the fabrication system is an off-axis holographic lens group (OHLG)
consisting of three off-axis holographic lenses. Under the illumination of an expanded laser beam, three collimated
beams can be generated by the OHLG to form a uniform hexagonal lattice pattern without using a collimating lens. The
utilization of OHLG in the system eliminates the noise in the interference pattern resulted from the collimating lens so
that lattice quality is enhanced. The system is simple and stable and can be used to fabricate large-size PhCs.
Diffraction from grating surfaces of a negative index metamaterial
Show abstract
We discuss the diffraction of waves due to the periodically corrugated boundary of vacuum and a linear, homogeneous
negative refraction index metamaterials (NIM). We show by numerical simulation that the grating surfaces can give rise
to a well-defined diffracted beam in addition to the negatively refracted beam. The direction of the diffracted beam is
consistent with elementary diffraction theory; however, the coupling to this higher order beam is much larger than would
be the case for a positive index material (PIM). To explore the properties of diffracted beams in a negative-index sample,
we simulate a wave incident on the interface between a NIM grating and free space. The numerical study provides an
indication of the relative coupling of the incident wave to the zeroth and first order beams.
Image preprocessing based on spatial statistics for the optical correlation recognition of aviation photographs
Show abstract
A new method of digital image processing is developed for the correlation recognition of aviation photographs under
volume holographic correlator. The physical characteristics of semivariogram of the image are analyzed according to
spatial statistics, which suggests the principle of the image segmentation, including the dimension of the templates, the
space between each template and the image restoration. Then the residual space of each template is calculated directly
based on the 2D-images to enlarge and to scatter the differences between the correlativity. After that, the residual spaces
are reconstructed to form the final set of templates. Finally the proposed method is tested on a series of aviation photographs. The experimental results come with rather higher precision as well as rather lower computational complexity, which supports the real-time capability of the optical correlation recognition of aviation photographs under volume holographic correlator.
Research on a novel high gain model for dispersive spectrographic systems
Show abstract
Traditional dispersive spectrographic systems usually base on slit imaging. The entrance slit can ensure a remarkable
spectral resolution but a loss of system throughput and vice versa, thus this kind of instruments can't achieve Jacquinot
advantage and Fellgett advantage simultaneously and statically. To derive a high gain model for the stationary dispersive
systems with these two advantages, traditional single-slit and the multi-slit spectrographic systems were studied. A
method for single channel spectrum abstraction in a multi-slit spectrographic system was derived. This method
demonstrates that if each individual slit in a multi-slit system possesses a transformation form of orthogonal independent
column codes, the spectrum of each individual slit can be abstracted from superposed spectrum, spectral resolution of
equivalent single-slit system is obtained and the system achieves dual advantages. This high gain computational system
model is applicable for almost all kinds of existing dispersive spectrographic systems. Furthermore individual coded slits
can be integrated as a coded aperture to increase system's integration level and reduce off-axis aberration. Based on the
derivation of theoretical model, two kinds of coding forms' mathematical models were studied. To verify the derived
theory, a testing system with a specially designed flat-field holographic concave grating and a coded aperture of order 16
Hadamard matrix form was set up. The experiment indicated that although optical aberration and other system noise
were involved, this high gain system model could still achieve a high spectral resolution of 0.4nm as single-slit system,
while remarkable system etendue (8X) and SNR (4X) were also obtained, which proved the correctness of the theoretical
derivation.
Design and fabrication of multimode interference couplers based on digital micro-mirror system
Show abstract
Multimode interference (MMI) couplers, based on the self-imaging effect (SIE), are accepted popularly in integrated
optics. According to the importance of MMI devices, in this paper, we present a novel method to design and fabricate
MMI couplers. A technology of maskless lithography to make MMI couplers based on a smart digital micro-mirror
device (DMD) system is proposed. A 1×4 MMI device is designed as an example, which shows the present method is
efficient and cost-effective.
A method of implementing a light beam with arbitrary polarization phase elements
Show abstract
Polarization is one of the key features of light wave. generation of light beams with required polarization is an issue
worth studying. In this paper, we propose a new method by which arbitrarily polarized light beam can be formed in
specified output plane. Several simulated results about axial-symmetric polarization are obtained by use of our proposed
scheme and the scheme proposed by. [J. Phys. D: Appl. Phys. 38 (2005) 827-832]. It is clear that simulated results with
use of our scheme are more agreed with the ideal beam. In addition, several other polarized beams are also simulated.
From all simulated results, they are all showed that a beam with arbitrary polarization distribution can be obtained by use
of our proposed scheme.
The dispersive system of a mini-spectrometer based on binary optics
Show abstract
In this paper, we designed a single binary optical element (BOE) which can perform collimating, dispersing and
focusing. Therefore, we can use it to replace grating and focusing lens in the mini-spectrometer. With just one major
optical element, the anti-vibration ability and optical stability of portable mini-spectrometer can be improved in big scale.
At the same time, optical set-up for mini-spectrometer also becomes much easier since fewer elements are involved.
Space saving due to this BOE offers opportunities for further resolution improvement. Besides this, this binary optical
element can be produced in very low cost compared to the cost of those gratings and lenses, since binary optical
elements are much easier to be duplicated for the sake of development of optical plastics and nano technology.
The splitter grating used in the soft x-ray laser interferometer for plasma diagnosis
Show abstract
The short wavelength, high brightness and good spatial coherence of soft x-ray lasers make them ideal sources for the
diagnostics of dense plasmas. As a widely used diagnosing tool in the research of laser-produced plasma, interferometry
has many advantages in the accurate measurement of the plasma electron density because it directly gives refraction
index mapping from the interference pattern processing. The electron density gradient and electron density of larger
variety plasma will be probed by the soft X-ray diffraction grating Mach-Zehnder interferometer (DGI). At the
wavelength 13.9nm which our DGI uses, we fabricate a laminar grating used as the splitter grating. Its groove density is
1000g/mm, groove depth is 13nm, duty cycle is 0.4±10%. The zero and first diffracted order beams have an equal
metrical diffraction efficiency about 25 percent at 81.3 degrees, and the maximum of the product is 7.6 percent at 81.2
degrees. The results illustrate the laminar grating is suitable for being used as a new pattern splitter grating at the
wavelength 13.9nm.
The numerical reconstruction for three-dimensional shape using digital holograms
Show abstract
In this paper, we introduce the potentialities of the digital hologram for the three-dimensional shape measurement from
numerical reconstructed image. The image processing of the Fresnel digital hologram recorded by CCD sensor and the
algorithm for 3d shape reconstruction is taken into account. Firstly, we stitch a series of small digital holograms to obtain a
hologram with larger size. Secondly, the reconstructed image sequences of different depth planes are obtained by
numerical reconstructing hologram. Finally, the depth information of each sample point of object is gained by algorithm of
focus measure evaluation, in which the maximum focus measure of a region is found by the grey level variance of image
sequence. The basic principle of this technique and its experimental verification are presented.
Numerical simulation of beam propagation through atmospheric turbulence for laser radar
Show abstract
The multiple phase screens and Fourier-transform algorithm for numerical simulation of beam propagation through
atmospheric turbulence is important for imaging problems, lidar or laser radar. In this work Fast-Fourier-transform-based
model of phase screens are used to simulate the propagation of a radar beam. The refractive-index power spectrum used
for phase screen generation is the so-called modified atmospheric spectrum defined by L C Andrews. The standard
compensations used to correct the undersampling at low spatial frequencies are improved, and the limitations and
numerical requirements for a simulation of given accuracy are established. By using the improved algorithm, the
scintillation index of gaussian beams propagation through atmospheric turbulence is studied. Comparisons of simulations
with analytic results are presented. The on-axis theoretical scintillation index is compared with simulated results at
different ranges and good agreement is shown between numerical simulation and theoretical results.
Real-color hologram with wide viewing angle obtained by the combination of computer and optical method
Show abstract
A new technique is proposed to obtain a real color hologram with a large viewing angle by the combination of computer
and optical method. Two steps are followed to finish this technique. (1) Computer-generated hologram H1 is yielded.
According to the theory of light propagation, and taking full advantage of computer-generated hologram, object
lightwave distribution of three monochromatic Fresnel holograms with a large dimension is computed in different area of
the same plane. Object lightwave distribution is folded into smaller area based on the method of mirror images. High
density holograms H1r, H1g, H1b are generated after the holograms are exported and microfilmed. (2) A rainbow
hologram H2 is generated by optical ways. In the recording procedure, two parallel mirrors with appropriate parameters
must be matched in the experiment system. In terms of the reversibility of light path principle, an image with a wide
viewing angle is reconstructed by reversing the reconstruction lightwave. The principle of the proposed method and the
experimental result prove that the technique achieves a color reconstructed image with a wide viewing angle of 14° . It is
very clear that the stereoscopic effect of the reconstructed image is increased.
Reduction of speckle noise in the reconstructed image of digital hologram
Show abstract
A fundamental problem in optical and digital holography is the existence of speckle noise in the reconstructed image.
Many approaches have been carried out in order to overcome this problem. In this paper a new technique to reduce the
speckle noise is proposed based on the physical nature of speckle noise. The illumination direction of the object beam is
changed to provide a different phase information for the same recorded object in an off-axis digital holographic setup
and the holograms are recorded with different illumination directions. Then the intensity information of the reconstructed
images is superposed and averaged to reduce the speckle noise. The theoretical analysis and experimental results are
shown to valid our proposal. They prove that the technique can effectively reduce the speckle noise without ruining the
object information.
Holographic light-guide plate for LCD backlight system
Show abstract
A novel holographic light-guide plate (HLGP) for the illumination of liquid crystal display is proposed in this paper.
The holographic film designed for red light (632.8nm) is introduced to the top surface of the wedge-shaped light-guide
plate. The backlight system with the HLGP can achieve large gain in uniform illumination. The enhanced illumination
uniformity of the emanating light is measured in the experiments.
Resolution enhancement of photon sieve based on apodization
Show abstract
Photon sieve is a novel diffractive optical element modulating either amplitude or phase which consists of a great
number of pinholes distributed appropriately over the Fresnel zones for the focusing and imaging of light. Photon sieve
has the advantages of the diameter of pinholes beyond the limitation of the corresponding Fresnel zone width and the
minimum background in the focal plane. Furthermore, photon sieve can be fabricated on a single surface without any
supporting struts required unlike the Fresnel zone plate. Photon sieve can be used as EUV telescope for solar orbiter,
space-based surveillance telescope operating at visible light, or other imaging components. Photon sieve can also be
used as one of the promising lithographic tools for nanoscale science and engineering to obtain the lower cost, higher
flexibility and better resolution. The approaches to enhancing imaging resolution of photon sieve are presented in detail.
According to Fresnel-Kirchhoff diffraction theory, the diffractive field of photon sieve is described by means of the
discrete fast Fourier transform algorithm. The related contents include the calculation of point spread function, the
suppression of side lobes, the imaging bandwidth, the physical limit of resolution, and the diffraction efficiency. Imaging
properties of photon sieve are analyzed on the basis of precise test.
Analysis of a photopolymer sensitized by whole visible light for holographic storage
Show abstract
A novel photopolymer based on polyvinyl-alcohol for holographic storage was fabricated. The
material with riboflavin (RF), methylene bule (MB), erythrosin B (ErB) as the photosensitizers for
holographic storage has a broad absorption spectrum range (more than 500nm). The photopolymer
can be sensitized by the whole visible light, and that will improve storage capacity and density of the
holographic storage greatly, especially under the short wavelength recording. Photo-induced
reaction processes in the photopolymer and phase grating of index modulation for holographic
storage were studied. The surface structure of the grating and the images of reaction processes were
scanned by SEM (Scanning Electron Microscope). The experimental results are compared with the
kinetics theory of the polymerization and they are fitted well. Furthermore, the grating constant can
be estimated from grating images which were scanned by SEM. Some holographic characteristics of
the photopolymer were analyzed. Using a standard holographic setup, we recorded unslanted
diffraction gratings.The material has high maximum diffraction efficiency (≥68%), good sensitivity
(≥3.03×10-3 cm2/mJ), and high index modulation (≥4.58 ×10-4) when its tickness is about 300μm.
Two dimentional simulate images generated by SLM (Spatial Light Modulator) were stored in the
film, and the reconstructed data pages had good fidelity. The results show that the material has a
better potential in holographic storage.
Experimental research of CCD/LCD in holographic interferometry
Show abstract
Holography has been widely applied in industry measurement, especially in 3D non-contact testing. Combining a high
resolution charge-coupled device (CCD) with a phase modulating liquid crystal display (LCD), holographic interferogram recording and display could be realized by digital holographic technique. Digital holographic technique has a great number of important and practical applications. In the conventional holography hologram was detected and
reconstructed by the holography panchromatic plate, or the photoconductive thermoplastic film, or the BSO crystal and
etc. But in the digital holography--the numerical version of the conventional holographic technique, hologram is
digitally detected by CCD and then displayed on the computer monitor. By reconstruction, the hologram is writted into
LCD, then illuminating the LCD with the reference wave, the tested object may be reconstructed optically. In this paper
the application technique of CCD/LCD in holography is theoretically studied and the bottle techniques have been solved.
According to the resolving power of the CCD and LCD, the angle between the two interfering waves should be less than
3° for recording the interference fringes with high spatial frequency. The simple and prospective optical architecture is
perhaps Twyman-Green interferometer for easy to adjust the required small angle between reference and tested object
waves, and also optical path deference for satisfying the requirement of spatial and temporal coherence. The
disadvantages of CCD/LCD digital holographic technique is the small separation angle between zero-order and ±1-order
diffraction. In order to separate ±1-order from zero-order diffraction, the minimum fringe spacing formed by the
interference of object wave with reference wave should satisfy the sampling theorem. This decides a relationship
between the size of object and the recording distance, which will be discussed in detail in the following text. And also
discussion about the experimental research of LCD in digital holography would be included in our paper.
Fuzzy control iterative algorithm for the design of diffractive optical elements for laser beam shaping
Show abstract
This paper proposes the Fuzzy Control Iterative Algorithm (FCIA) for the design of diffractive optical elements for laser
beam shaping. Firstly, to improve the poor uniformity of output laser beam obtained by the G-S algorithm, we put
forward the Profile Smoothing Algorithm (PSA), which is effective in improving beam uniformity but slack in
controlling the Mean Square Error. Then we put forward the Fuzzy Control Iterative Algorithm, which combines PSA
and G-S algorithm by fuzzy control theory. Taking advantages of GS and PSA, FCIA can decrease both Mean Square
Error and nonuniformity of output beam simultaneously. Computer-designed result shows that an extremely ideal output
beam is derived by using FCIA. The Mean Square Error is 0.75%. The nonuniformity is 0.46%. And the energy
converting efficiency is up to 94.91%. This paper affords a novel algorithm for the design of diffractive optical elements
for laser beam shaping.
Focusing properties and focal depth of amplitude modulation Gaussian beams
Show abstract
The focusing properties and focal depth of amplitude modulation Gaussian beams are investigated. Numerical results
show that the intensity in the focus plane is circle shape in the low numerical-aperture optical system, while the intensity
distribution in the focal plane is ellipse shape in high numerical-aperture optical system due to contribution of
depolarized longitudinal component. Focal spot size and focal depth can be adjusted by changing geometrical parameters
and the modulation amplitude power n of Gaussian beams. The tunable range of the focal depth is very considerable.
Study on fiber position sensor based on wavelength encoding plane variable-line-space gratings
Show abstract
In recent years, a new fiber position sensor based on wavelength encoding plane variable-line-space gratings is
developed and has attracted more and more interest. In this paper the theoretical background to the fiber position sensor
concept is briefly described. The large slope groove density distribution variable-line-space grating with holographic
recording is used in fiber position sensor. The preliminary results obtained were quite noteworthy. Due to the unevenness
of the incident light intensity in different wavelength, the diffractive intensity of different position change quickly. The
diffraction wavelength curve of the system is given. The resolution of the position sensor is also discussed in this paper.
Fabrication for micro circular gratings and arrays based on binary optical methods with DMD system
Xingdao He,
Kaiyuan Lu,
Yongqing Gong
Show abstract
Using DMD system to make circular gratings and arrays is based on the character of Space Light Modulation (SLM)
of DMD chip which can control the reflected lights based on the input figures' gray-scale. Firstly, circular gratings
are simulated in a computer with some simulation software programmed in VC. Then, the figures are inputted in the
DMD chip. With the character of SLM of DMD chip, the reflected lights can be controlled according to the circular
gratings' gray-scale. The circular gratings can be obtained after being developed, fixed and etched. Many contrast
experiments are carried out to confirm the technique parameters of circular gratings, as well as fabricate the two
levels, four levels and array of circular grating. By use of this method, we are capable of making low-cost but useful
circular gratings easily. Their levels and radii can be controlled, which will be suited for many optical systems.
Compared with scoring mechanically, lithography and e-beam etching, binary optical methods are more convenient,
efficient and low-cost.
Methods of controlling grooves profile and the duty cycle of gold transmission phase gratings
Show abstract
It is known that rectangular grooves profile and various duty cycles (line to pitch) are required to attain maximum
efficiency. The gold transmission phase gratings have been fabricated using holography and ion-beam etching
techniques. The latent image monitoring technique and real time end-point detection technique were utilized to improve
control of the shape of grooves and duty cycle during exposure and development, respectively. It is difficult to produce
gratings with larger duty cycle in photoresist on gold for standing wave, nevertheless it is revealed in our work that the
duty cycle can be more than 0.4 for the case for photoresist on gold substrates if development is stopped where the slope
of the monitoring curve begins to drop off, not at the peak of the diffracted signal. In ion-beam milling, the influence of
redeposition on the shape of grooves and duty cycle has been overcome by using a thin mask of Chromium with a
comparatively low ion-etch rate and tilting and rotating substrates beneath the ion beam. Finally, some gold phase
gratings with the duty cycles in the range of 0.25-0.45 have been obtained, whose duty cycle value is about 0.45, and
their grooves profile is trapezoidal profile whose left and right facets are both more than 83 degrees approximately.
Replication of holographic lens used as multiplexer/demultiplexer in fiber optic communication
Show abstract
Hot embossing has become a key technique in the replication of microstructures. In particular, the hot embossing of
diffractive gratings into thermoplastic has been widely used in the mass production of holograms. The process involves
the transfer of a surface relief structure from a plate to a substrate by high temperature and pressure applied to an
intermediate film. So in this paper a novel printing process for replication of holographic lens used as
multiplexer/demultiplexer has been demonstrated. Advantages of this technique are the low cost and ease of processing.
Some analysis indicates that for WDM in fiber communication, the thermoplastic polycarbonate is a good choice. In the
primary experiments, the optimum temperature and force for embossing were 130 degrees and 5Mpa. The optimal
thickness of a nickel shim used in the mesne process was established to be 60 micron. The lens arrays were uniformly
embossed over the entire area of the thermoplastic which was typically 8×8. Minimum diffraction efficiency of the
embossed lens in thermoplastic layer is about 50% (-3dB). High quality replicas of device have been fabricated using
this process. Printing via an embossing process offers the possibility of mass production of demultiplexer easily and
cheaply compared with conventional demultiplexer.
Amending the uniformity of ion beam current density profile
Show abstract
The uniformity of ion beam current density profile has been amended by changing the flow of the gas and making a new
beam channel. The platform scanned in the horizontal orientation in this experiment, so the horizontal ion beam current
distribution had hardly any effect on the etching uniformity and amending the ion beam current density profile in the
vertical orientation was sufficient for the purpose of plat etching profile. The ratio of the ion source's working gas inputs
has some effect for the uniformity and a ratio of 6.50sccm: 8.00sccm: 9.60sccm of the three gas inputs flow1: flow2:
flow3 will lead to a more uniform profile. According to the horizontal distribution and the original vertical ion beam
current density distribution measured by Faraday Cup, a new beam channel was made. The uniformity of ion beam
current density profile is enhanced from ±4.31%to ±1.96% in this experiment.
Reactive ion beam etching of multilayer diffraction gratings with SiO2 as the top layer
Show abstract
Multilayer dielectric grating plays an important role in the laser inertial confinement fusion, which is fabricated by using
holographic lithography and ion beam etching. In this paper details the reactive ion beam etching of multilayer dielectric
grating with SiO2 as the top layer. The etching of SiO2 was carried out by a radio frequency reactive ion beam etcher
with CHF3 chemistry to increase the etch selectivity and get a high fidelity grating pattern transfer from photoresist into
SiO2 coating. The photoresist gratings with different profiles as masks were used to create SiO2 corrugations with
different profiles separately. The etching results were analyzed in detail, including the facet and redeposition effects. In
conclusion, it is essential that the photoresist grating mask should be high and steep enough to get SiO2 grating with
vertical profiles. The multilayer dielectric grating with SiO2 as the top layer exhibited an efficiency of about 95% in the - 1 order at TE polarization of 1 064 nm light at Littrow mounting.
Shift-phase code multiplexing technique for holographic memories and optical interconnection
Show abstract
Holographic technologies for optical memories and interconnection devices have been studied actively because of high
storage capacity, many wiring patterns and high transmission rate. Among multiplexing techniques such as angular,
phase code and wavelength-multiplexing, speckle multiplexing technique have gotten attention due to the simple optical
setup having an adjustable random phase filter in only one direction.
To keep simple construction and to suppress crosstalk among adjacent page data or wiring patterns for efficient
holographic memories and interconnection, we have to consider about optimum randomness of the phase filter. The high
randomness causes expanding an illumination area of reference beam on holographic media. On the other hands, the
small randomness causes the crosstalk between adjacent hologram data.
We have proposed the method of holographic multiplexing, shift-phase code multiplexing with a two-dimensional
orthogonal matrix phase filter. A lot of orthogonal phase codes can be produced by shifting the phase filter in one
direction. It is able to read and record the individual holograms with low crosstalk. We give the basic experimental
result on holographic data multiplexing and consider the phase pattern of the filter to suppress the crosstalk between
adjacent holograms sufficiently.
Multi-viewing-point 3D digital display using integral imaging
Show abstract
This paper proposed a method by using integral imaging for computationally reconstructing three-dimensional (3D)
images from different viewing points without introducing additional system complexity. In this method, the process of
3D scene sensing is accomplished by using a microlens array to obtain elemental images. The multi-viewing-points
reconstruction process is carried out by computationally simulating optical reconstruction. The prototype displays
differently directional views with a horizontal or vertical angle pitch of 3°~1°, when the depth range of object is from
150mm to 450mm. The viewing angle of one image point is about 53°. By optimizing the parameters of imaging system,
the angle pitch would satisfy the requirement of practical application. The experimental results proving the effectiveness
of the method are given.
Study of a new style holographic grating (that can be used) for wavelength-division demultiplexer
Show abstract
Holographic grating can be used widely in optical fields, especially in wavelength division multiplexer and optical fibre
network. In this paper, a new kind of water resisting photopolymer which is sensitive to the red light of 632.8nm and
green light of 514.5nm is made into double holographic grating by exposure twice. The resolution of this grating is
above 4000line/mm. The principle of manufacture and technology of the new style grating is simple; it doesn't need the
second treatment. The grating has many other merits, such as lower cost high diffraction efficiency, better stability and
so on. Based on the study, the holographic grating can be used for wavelength-division demultiplexer for it is lower loss
and narrow-band width.