Show all abstracts
View Session
- Front Matter: Volume 6831
- Near-Field Optics and Surface Plasmon Polariton
- Metamaterials
- Photonic Crystals
- Optical Characterization
- Calculation of Nanostructures
- Quantum Dots
- Poster Session
Front Matter: Volume 6831
Front Matter: Volume 6831
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 6831, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.
Near-Field Optics and Surface Plasmon Polariton
Micro-cylinder mode in photonic quasicrystal observed by near-field optical microscopy
Show abstract
We propose and realize a micro-cylinder mode in photonic quasicrystal (PQC) on the top of an edge-emitting GaN light
emitting diodes (LEDs) with 30 μm indium tin oxides (ITO) covered and 8 μm GaN exposed broad-stripe. A
well-defined hexagon-like localized state following a C6v symmetry is identified from the PQC micro-cylinder arrays.
Enhancement factor of the surface light extraction from 12-fold PQC patterns on electrical current injected GaN-based
light emitters is 2.4 times higher than non-patterned regions, which is observed by scanning near-field optical
microscopy (SNOM). According to the near-field optical images, micro-cylinders can be considered as nano-optics
sources because the electromagnetic energy is strongly concentrated due to the wave guide modes and the beaming effect
of the surface microstructures.
Large Goos-Hänchen displacement of evanescent light beam in near-field enhanced configuration
Show abstract
We report that the transmitted evanescent light beam under total reflection will experience a lateral displacement
similarly to that of the reflected beam, called Goos-Haenchen (GH) effect. By a dielectric thin film coated onto the
dielectric surface, which is usually considered as the near-field enhanced configuration in atom optics, we indicate
that the displacement of the transmitted evanescent beam can be greatly enhanced to several tens of wavelengths
at transmission resonance under total internal reflection. Numerical simulations have been performed and it is
shown that the transmitted evanescent beam maintains well the shape of the incident beam when the thickness
of the thin film is required to be of the order of wavelength. Further, it is demonstrated that the stationary-phase
approach is also applicable to transmitted evanescent beam and the GH displacement of the transmitted beam is just half the GH displacement of the reflected beam. The discussions presented here may arouse interest in atom optics and near-field microscope.
Analysis of resonant properties in surface plasmon polaritons nanocavities
Show abstract
We analyze the resonant properties in surface plasmon polaritons nanocavities and study the resonant transmission spectrum of
light through a sub-wavelength metallic nanocavity composed by two pieces of finite silver thin slabs with nanometer
configurations of periodic sinusoid profile on their inner boundary, setting by face-to-face arrangement with a separated
spacing. The boundary elements method (BEM) is adopted for analyzing the optical behavior of these metallic nanocavities.
We investigate the influence of the number of the grating period on the optical resonant behaviors of the nanocavities. The
numerical results indicate that the wavelengths of resonant peaks are well agreed with the predicted resonant wavelength.
Furthermore, the number of the resonant wavelength from the scattered resonant transmission spectrum increases as the
number of the grating period is increased, and the resonant peaks shift to the longer wavelength while the number of the
grating period is increased. It is believed that our analysis will provide important information for designing novel cavity that
can select the wavelength or realize ultra-minitune optical sources that can be easily integrated in the all-optical communication
system.
Evolution of microscopic interaction force and interpretation for major well-known optical phenomenon and experiments
Show abstract
Two formulas for microscopic interaction force have been suggested in this paper. Some interesting
results such as the invariant light speed in free space and the
πphase change or one half of wavelength delay
could be interpreted using the dynamic equations based on our suggestions although the former is the foundation
of relative theory, the latter is all-known phenomenon in optics. There is no concise or clear understanding to them
at least at present so this gap might be filled by our work. At the same time several well-known classical or
modern optical experiments are also proved or logically analyzed. This fact shown that our suggestions are not
only considerable assumptions but also revealed the interaction relation between microscopic particles.
Its' worth to note that we have tested the microscopic geometric scale (GAS) pointed a short time before by us as
well as the microscopic interaction force using Fizeau experiment.
Besides this some other interesting results, such as the possible geometrical action scale of gravitational field
particle, the new method to measure the constant of gravitation and time evolution equation for media index etc.
Near-field intensity distribution from a bow-tie aperture VCSEL with its polarization state improved
Hongfeng Gai,
Jia Wang,
Qian Tian,
et al.
Show abstract
A micro-aperture vertical-cavity surface-emitting laser (VCSEL) is a kind of active nanophotonics devices. It can
confine the optical near-field to a nanometric light spot of high intensity. The confinement effect is usually implemented
by a round aperture. A bow-tie aperture can do it better if the incident light polarizes along the line between its ridges.
However, a conventional VCSEL does not have a definite polarization state, so a bow-tie aperture VCSEL is very
difficult to be implemented. In order to solver this problem, a rectangular aperture array is employed to improve the
polarization state. Two bow-tie aperture VCSELs with and without their polarization state improved are fabricated. Their
near-field intensity distribution is measured and compared. The measurement results demonstrate that the near-field
intensity is enhanced dramatically when the polarization state is improved. So the confinement and enhancement effect
of a bow-tie aperture can be obtained on the basis of a micro-aperture VCSEL.
Metamaterials
Nanometrology based on white-light spectral interferometry in thickness measurement
Show abstract
A new white-light interferometric technique using in measurement of thickness based on the theory of spectral-domain
interference is specified in the paper. The theory of spectral-domain interference broke the limitation of coherence
length in interferometry, and gain a much longer measuring range than in time-domain. The optical fiber was applied to
Michelson interferometer with the advantage of much convenience of system design. Spectrometer is used to get the
spectral-domain signal. With a simple arithmetic, the optical path difference which is related to some parameter could
be acquired. A thickness measuring system is designed. The measuring range could be calculated, the error could be
forecasted. The simulated result indicats the error of white-light spectral interferometry can be controlled within several
nanometers.
Single-negative negative index metamaterials with broad bandwidth
Show abstract
The theoretical method to design negative refractive index metamaterials by single negative permittivity metamaterials is
presented. By designing the electric and magnetic response metamaterials separately, the complexity of the design work
can be simplified a lot. For the magnetic response metamaterials, the metallic post structure is adopted. Varying the
height of the post, the response wavelength can be adjusted linearly. For electric metamaterials, wire-mesh structure is
adopted. The effective material parameters, including refractive index, impedance, permittivity and permeability are
given. Such a structure has negative refractive index during a broad frequency band and easy to design.
Photonic Crystals
An ultracompact refractive index gas-sensor based on photonic crystal microcavity
Show abstract
An ultracompact gas-sensor based on the two-dimensional photonic crystal microcavity is presented. The sensor is
formed by a point-defect resonant cavity. The transmission spectrums of the sensor with different ambient refractive
indices ranging from 1.0 n = to 1.01 n = are calculated. The calculation results show that a change in ambient refractive
index of Δn=1×10-4is apparent, the sensitivity of the sensor (Δλ/Δn) is achieved with 433nm/RIU(when lattice
constant 520 a=520nm), where RIU means refractive index unit . The properties of the sensor are analyzed and calculated
using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method.
Using the fabry-Perot cavity mode, the performances of the refractive index sensor are analyzed theoretically. The sensor
is optimized using the photonic crystal waveguide structure and simulated using the FDTD method. As the small sensing
area (~10μm2) of the device would require only ~1fL sample analyte, these ultracompact gas sensors would be widely
used in little sample analyte in gas measurement.
Comment on properties of one-dimensional photonic crystals containing negative refraction materials
Show abstract
In this paper, by using the transfer matrix theory and the dispersion relation principle, via math tool processing numerical
value simulation get the energy band, the limited field and the dispersion characteristic of one-dimensional photonic
crystals with negative-index materials, we find there are two photonic band gap, the lower forbidden band which is
called zero-n gap remains nearly invariant under a various incident angle, while the higher one which is called Bragg
gap changes ceaselessly with the increasing incident angle. Through introducing the defect we found that the defect
mode inside the zero-n gap remains invariant with the scaling of non-defect part. Conversely, the defect mode inside the
Bragg gap shifts greatly in frequency with scaling. The studying of the dispersion relation shows that the width of the
zero-n gap enlarges, but the middle of each gap hardly changes, on the contrary the middle of a Bragg gap will shift
noticeably while the width of the gap will change a little when the ratio of the thicknesses of the two types of layers
varies and that the zero-n gap that distinguishes itself from a Bragg gap in that it is invariant with scaling. The emphasis
of this paper lies in analyzing the characteristic of this type of photonic crystals.
zero-n gap enlarges, but the middle of each gap hardly changes, on the contrary the middle of a Bragg gap will shift
noticeably while the width of the gap will change a little when the ratio of the thicknesses of the two types of layers
varies and that the zero-n gap that distinguishes itself from a Bragg gap in that it is invariant with scaling. The emphasis
of this paper lies in analyzing the characteristic of this type of photonic crystals.
Optical Characterization
Simulation of optical surfaces and their PSD study
Show abstract
The performance of a optical component is greatly dependent on its surfaces. There are many ways to measure and
evaluate a surface so far, but actually no one knows exactly what a "real" surface likes, and thus makes some
measurement unexplainable. This paper develops a way to construct various synthetic surfaces. Referred to actual AFM
measurement, regular or irregular surfaces can be created and studied. Bumps, scratches, granules, profile errors and
other construction elements can be added to form a very complicated virtual surface. The number, size and distribution
of these elements can be changed, and if necessary, the surface roughness can be controlled in a specialized range. As
these surfaces are created synthetically, we know exactly what construction these surface contain. The height data of
created virtual surfaces can be transferred into the file that AFM instrument can read and handle. As a typical example, a
very complicated surface is created step by step in this paper, and its PSD for each step are calculated. This process
mikes it very clear how the surface component element affect its PSD function, and is benefit to our better understanding
of real surface construction.
The specimen preparation methods for nanoindentation testing of biomaterials: a review
Show abstract
Nanoindenter provides an approach for assessing mechanical properties in micro-electronics devices and films based on
quantitative, controlled nanoindentation of surfaces, with the convenience of modern automation. It is also suitable to
measure mechanical properties of biomaterials. Nanoindenter for biomaterial testing in bone and dentin was widely used.
Recently some studies of nanoindentation properties in insect were carried out. While the surface roughness of natural
biomaterials problem should not to be ignored in nanoindentation testing. The surface roughness will critically affect the
precision of result of nanoindentation testing and caused error data. In this paper, the biomaterials specimen preparation
methods for nanoindentation testing will be reviewed.
Improvement on thickness uniformity of large-area DLC thin films deposited by femtosecond pulsed laser
Show abstract
A off-axis deposition method, which aligns the edge of the substrate to the normal of the plasma plume and
makes the edge of the plasma plume at the center of the substrate, is used to deposit large-area DLC films. The
distance between the target and the substrate and the deposition time are optimized to obtain uniform and large
area DLC films on the K9, fused silica glasses and ZnS with the diameter of 50 mm. It is shown that the thickness
uniformity of the films with off-axis deposition method is much better than that with the on-axis method. The
thickness uniformity for off-axis and on-axis deposition is compared, and the possibility for preparing large-area
uniform films is discussed. In addition, the transmission of ZnS with DLC coated is improved.
Investigation on the laser transmission properties of nanofluids
Show abstract
Our recent work revealed that, when nanofluids containing a modest volume fraction of nanoparticles are illuminated by
a parallel monochromatic laser beam, speckles would be formed. Therefore, it is realized that Laser Speckle Velocimetry
can be used to measure the velocities of nanoparticles in nanofluids.1 This paper aims to investigate the laser
transmission properties of nanofluids via experiments and numerical simulations, so as to determine the proper
conditions for the formation of speckles. First, experiments are performed to measure the light transmittance of
nanofluids at different laser power and different particle volume fraction. Then, Monte Carlo simulations are carried out
based on a physical model considering random collisions between photons and nanoparticles to simulate light
propagation in nanofluids. The numerical results are in good agreement with the experimental results, and a final
conclusion is drawn that the particle volume fraction and particle size are the prime factors that influence the light
transmittance.
Calculation of Nanostructures
The energy levels of a nanoring in the presence of quantum barriers
Show abstract
We have considered a two dimensional narrow semiconductor ring with sectorial barriers that is threaded by
magnetic flux. Using numerical diagonalization techniques, we have presented the diagrams of the energy spectra
versus the magnetic flux. For a constant value of the barrier height, with enhancement of the number of barriers, the
energy levels shift to higher energies and the degeneracy of the system increases. We have also investigated the
behavior of the energy levels with the magnetic flux for different values of the barrier height. The fluctuation of the
energy levels decreases, as the barriers' height increases.
High efficiency fiber to waveguide optical coupler in silicon-on-insulator based slot waveguides
Show abstract
We propose a novel optical fiber-to-waveguide coupler for integrated optical circuits. The proper materials and structural
parameters of the coupler, which is based on a slot waveguide, are carefully analyzed using a full-vectorial three
dimensional mode solver. Because the effective refractive index of the mode in a silicon-on-insulator-based slot
waveguide can be extremely close to that of the fiber, a highly efficient fiber-to-waveguide coupling application can be
realized. For a TE-like mode, the calculated minimum mismatch loss is about 1.8dB at 1550nm, and the mode
conversion loss can be less than 0.5dB. The discussion of the present state-of-the-art is also involved. The proposed
coupler can be used in chip-to-chip communication.
Confined optical fields based on surface plasmon polaritons
Qingyan Wang,
Jia Wang,
Shulian Zhang
Show abstract
A nonradiating, spatially confined optical field based on surface plasmon polaritons (SPPs) on a corrugated surface of
metal film is proposed. With the help of the surface plasmon band-gap nano-structure, SPP can be collected in a spatial
region beyond the diffraction limit and form a confined optical field, which can be used as a nano-source in near-field.
Compared with other types of near-field sources, such confined optical field provides higher intensity, and the spot size
of the nano-source can keep constant within certain distance. By using the method of Finite-Difference Time-Domain
(FDTD) is used to simulate the distributions of the confined optical field, two types of confined optical fields based on
SPPs excited by prism and by grating, respectively, are demonstrated in 2D- and 3D-space. Such confined optical field
as a nano-source, is promising to be applied to near-field imaging and optical manipulation, and has potential
applications in nano-photonics devices based on SPP.
Quantum Dots
Luminescent CdTe/CdS core-shell and CdTe/CdS/ZnS multi-layer quantum dots: synthesis and investigations for bio-application
Show abstract
Concerns on quantum dots (QDs) have been continuously increasing because of their advantages on photophysical
properties. Water soluble CdTe/CdS core-shell and CdTe/CdS/ZnS multi-layer QDs were synthysized with
mercaptopropanoic acid (MPA) as stabilizer in aqueous phase in the current research. The obtained QDs were
characterized with fluorescence spectrum (FS), and quantum yields (QYs) was calculated base on the resulting data from
FS. Comparing with CdTe core, red-shift of maximum emission wavelength (MEW) of CdTe/CdS was observed, which
indicated the growth of QDs size. To obtain high QYs of CdTe/CdS core-shell QDs, several methods and different
reaction conditions were investigated and discussed, such as dependence of Cd2+ concentration, dependence of pH,
influence of S2-:Te2-, and effect of Cd2+:S2- etc. Among all of discussed methods, QYs of core-shell CdTe/CdS is
generally degressive with refluxing time elapsing. The best QYs of 79.8% can be achieved when pH was set at 8.5,
Cd2+:S2-=1:0.1 (mol ratio). Moreover, CdTe/CdS/ZnS multi-layer QDs was prepared, and results via FS indicated a
further red-shift from 554 nm to 646 nm comparing with CdTe/CdS QDs, but QYs decreased to 14.0%. QDs currently
discussed in this research are easily synthesized, and safe to organism, i.e. biocompatible. They will be useful in
applications of biolabeling, imaging, and biosensing based on fluorescence resonance energy transfer (FRET).
Surface enhanced Raman scattering activity of core-shell Au nanoparticle film
Show abstract
Core-shell gold nanoparticles film was fabricated by using nanolithography and self-assembly monolayer technology.
The film exhibits unique optical properties and has strong surface enhanced Raman scattering activity. The relationship
between nanostructure and surface electrical field was studied by employing pyridine as the SERS probe. It was found
that particle size and interparticle space are of important factors. The enhanced ration is measured more than 104.
Mechanisms of plasmon-induced charge separation and recombination at gold nanoparticle supported on different size TiO2 film systems
Show abstract
Study of plasmon-induced charge transfer mechanism in gold-TiO2 system is crucial and promising in the solar cell
application. To investigate charge separation and recombination dynamics in gold/TiO2 nanoparticle systems, we used
ultrafast visible-pump/IR-probe femtosecond transient absorption spectroscopy method. In our experimental study,
anatase TiO2 with different particle size 9 nm and 20 nm were chosen as electron acceptors. Plasmon-induced electron
transfer from the gold nanoparticle to the conduction band of TiO2 was studied by optical excitation of the surface
plasmon band of gold nanoparticle at 550 nm. The transient absorption kinetics were studied by probing at 3440 nm to
observe intraband free electron adsorption in TiO2. In our experimental results, electron injection was found to be
completed within the apparatus time resolution (240 fs), the charge recombination decay within 1.5 ns was
nonexponential. And when laser power changed from 0.5 μJ to 1.9 μJ, the recombination decay didn't depend on the
excitation intensity. It is interesting that we found the measured back electron transfer kinetics up to 1.5 ns were strongly
dependent on the particle size of TiO2. The plasmon-induced charge transfer mechanisms will be discussed.
Electronic states in an infinite one-dimensional random binary quantum wire in the presence of electric field
Show abstract
We use a tight-binding Hamiltonian for an infinite quantum wire with substitusional disorder of A and B atoms in a
uniform electric field and calculate the density of states by coherent-potential approximation method. The electric field
produces a little oscillation on the local density of states and by increasing the strength of the electric field the amplitudes
of the oscillations grow up and they becomes more localized too. Also, by increasing the strength of the electric field, the
range of the extension of the energy spread out. The density of states at E=0 versus a parameter which depends on electric
field, is calculated and it shows oscillating pattern too. The local density of states for the different sites is calculated and all
of them are similar except a shift which is proportional to the strength of the electric field.
Poster Session
Effect of scatterers shape between coupling channels on the photonic crystal coupler
Show abstract
In the present paper, the two-dimension photonic crystal (PC) polarization coupler is mainly studied. The PC
waveguide coupler with a single row of dielectric rods in the interaction region is composed of square-arrayed dielectric
pillars in air. The photonic band gap maps are calculated by using plane wave expansion (PWE) method and the effects
of the geometrical parameters of the scatterers between two coupling channels on the property of the PC couplers are
analyzed by using the finite-difference time-domain (FDTD) method. The simulation results show that the coupling
property is sensitive to the shape variation of scatterers. The shape variation of scatterers between the two coupling
channels will reduce coupling length greatly.
Properties of ITO thin films prepared by APS-assisted EB evaporation
Show abstract
ITO thin films were prepared by oxygen ion-assisted electron beam (EB) evaporation technique onto K9 glass substrate
at low temperature and effects of substrate temperature, oxygen flux on the structure, electrical and optical properties of
ITO thin films were investigated. An advanced plasma source (APS) was used to produce high density argon and oxygen
ion flux to cause electron degeneracy in the band gap by introducing non-stoichiometry in the ITO films to improve the
conductivity of the prepared films. The structure of the ITO thin films were characterized by XRD and the results shown
that all of the ITO films deposited at the temperature above 160°C shown a polycrystalline structure. And as the
substrate temperature increased, the optical transmittance and electrical conductivity were improved. It is also found that
the increase of oxygen flux increased the optical transmittance of the deposited ITO films, however, at a given deposition
rate, the electrical conductivity showed a maximum in a certain range of oxygen flux. ITO thin films with the resistivity
of 1.65×10-4 Ω· cm and an optical transmittance of above 90% in the visible region were prepared at a temperature of
250°C by the given method.
Influence of SDBS on stability of Al2O3 nano-suspensions
Show abstract
In this paper, the stability of Al2O3 nano-particles in water were investigated at different pH values and different concentration of sodium dodecylbenzenesulfonate (SDBS) dispersant by measurement of the zeta potential and
absorbency. The experimental results show that zeta potential is relation with absorbency, and the higher magnitude of
zeta potential corresponds to the higher absorbency, and the better dispersion and good stability of the Al2O3-H2O nano-suspensions. It is also found that the concentration of SDBS can significantly affect the value of zeta potential and absorbency. The experimental results show that for SDBS there is an optimizing concentration in the nanofluids which
can induce high zeta potential and high absorbency, and that in 0.1% Al2O3 -H2O nano-suspensions the optimizing concentration of SDBS is 0.09%, which has the best disperse results of the nanofluids.
The surface treatment of silicon wafer by microwave down-stream plasma etching
Show abstract
Silicon is one of the most common materials used in optical micro-electro-mechanical systems (MEMS). For the
optical applications the surface quality plays a vital role in the performance of elements, so the control of surface
morphology, such as surface smoothing, is very important to produce optical MEMS elements with high reliability and
high quality. The most commonly used etching methods such as reactive ion etching (RIE) always left damage layer on
the etched surface leaving the surface with high roughness. In this paper 2.54GHz micro wave excited plasma was used
to treat the silicon surface, and the different etching conditions of CF4 and O2 mixture were investigated. The surface
quality after this down-stream plasma treatment was studied by atomic force microscopy (AFM) measurement.
Threshold behavior of defect modes in one-dimensional active photonic crystal
Show abstract
Based on a model of coupling Maxwell's equations with the rate equations of electronic population, the spatial-distribution
and spectrum-characteristics as well as amplified properties of defect modes such as lasing threshold,
saturated output in a single-defect active photonic crystal are investigated through finite-difference time-domain method.
Influences of the number of crystal periods and spatial profile on amplified feature are also analyzed. The results show
that the lasing threshold and saturated output depend directly on the number of crystal periods and the spatial profile of
defect modes; the defect mode with lower mode area has a low-threshold. Furthermore, the lasing threshold can be
further reduced as the saturated output increases if the number of crystal periods increase. Such a feature is important for
understanding of the interaction between optical gain and defect modes.
Dispersion-induced localized modes in weakly random media
Show abstract
Using a time-independent calculation based on self-consistent transfer matrix method, we numerically investigate
localized mode in a one-dimensional (1D) weakly disordered medium containing Lorentz dispersive material. The result
show that the random medium containing dispersive media has frequency-dependent localized modes. Such localized
modes strongly depend on dispersive parameters, such as transverse optical phonon frequency ω0, oscillator strength Χ0 and thickness of dispersive layer. The resonant frequency of such mode can be modified to shift by applying a dispersive
medium. By this study, we will acquire some knowledge of localized mode in dispersive disorder medium; furthermore,
this study suggests a method to realize tenability of localized mode, which is important for application of random laser.
Thermal treatment for tuning the lasing wavelength of quantum dot laser diodes
Show abstract
We have tuned the lasing wavelength of a quantum dot laser diode (QDLD) by a thermal treatment. The InGaAs QDLD
structure for 980 nm wavelength applications was grown by molecular beam epitaxy using the Stranski-Krastanov
growth mode. The room temperature photoluminescence (PL) of a QDLD showed the ground state (GS) and excited
state (ES) at the wavelengths at 993 and 946 nm, respectively. The 100 μm-wide and 4 mm-long broad area QDLD
showed the lasing wavelength of 963 nm attributed to the ES of QDs with higher gain. After the thermal treatment at
800 °C for 3 minutes with 300 nm-thick SiO2 capping layers, the PL intensity of the GS increased, which caused the
enhanced GS gain. The enhanced GS gain is thought to the attribution to the decreased carrier trapping due to the
defects quenching. As a result, we could control the lasing wavelength of the QDLD from a wavelength of 963 nm to a
wavelength of 980 nm. Moreover, the performances of these QDLDs have been discussed. This post-growth technique
can be used to enhance the performances of the optoelectronic devices based on quantum dot.
Accurate vibration detection of a rough surface
Show abstract
Based on the semiconductor laser whose spectral line with width is compressed to be less
than 1.2Mhz, a system was designed to measure and improve the amplitude and frequency of the
real-time microvibration with sinusoidal modulation. real-time microvibration measurement was
executed without alignment problem in the interferometry; and low-frequency disturbance of
environment could be eliminated. Suggestions were also given to consummate the system. The system
also has resistance against the low frequency disturbance of the environment.
Fabrication of InGaN quantum dots by periodically interrupted growth in MOCVD
Show abstract
Self-assembled InGaN quantum dots are fabricated in a two-flow horizontal MOCVD reactor maintained at the
pressure of 200 torr. The precursors were trimethyl-gallium (TMG) and trimethyl-indium (TMI) and ammonia (NH3),
and the carrier gas was N2 and H2. The optimum condition for periodically interrupted growth (PIG) mode was deduced
to fabricate the InGaN quantum dots. NH3 was supplied in PIG mode with the interval of 3 seconds and 5 seconds while
TMG and TMI were supplied continuously. The carrier gas was N2 in QDs growth, while H2 in nucleation and buffer
layer growth. The influence of number of periodic interrupted NH3 on the structural and optical properties of InGaN
quantum dots was investigated by AFM, FE-SEM and low temperature photoluminescence (LT-PL). The AFM images
give the size of InGaN QDs with diameter of 20 ~ 50 nm, height of 3 ~ 10 nm and density of 1010 #/cm2 ~ 1011 #/cm2. A
strong peak at 362.2 nm (3.41eV) and broad emission peak in 435 nm (2.86 eV) were evolved in the photoluminescence
measurement using Nd-YAG laser. The composition of QDs was estimated to be In0.14Ga0.86N from the relation between
peak energy and indium content. Hence. The periodic interruption growth enables the fabrication of self- assembled
InGaN QDs with high density and uniform size.
Properties of aluminum doped zinc oxide thin film by sol-gel process
Show abstract
The thin films of transparent conductive aluminum doped ZnO have been deposited by the sol-gel process. In this study,
important deposition parameters were thoroughly investigated in order to find appropriate procedures to grow large area
thin films of low resistivity and high transparency at low cost for device applications. Experimental results indicated
that the annealing temperature affected the crystal structure of the aluminum doped ZnO films considerably, but the
controlling of effective doping concentration was the key point to achieve low film resistance by sol-gel process. It was
adjusted by controlling the precursor concentration. Although the structure of our aluminum doped ZnO films did not
have the preferred orientation along (002) plane, they had a high transmittance of over 87 % in visible region. In our
experiments, the most suitable Al doped concentration was 1~4 mol%. The annealing temperature for the pre-heat
treatment was 250 °C and post-heat treatment was 400-600 °C. The Al doped and undoped ZnO films are very uniform
and compact. It is confirmed that the doping concentration and thermal treatment are important factor with electrical
conductivity of ZnO films.
Fabrication of CoFe nanostructures by holographic lithography
Show abstract
A novel process that combines interference lithography and ion beam etching is presented for fabrication of magnetic
submicron structures and nanostructures in this paper. Instead of an antireflective coating, vertical standing wave
patterns were removed using oxygen descumming process. A series of magnetic submicronmeter structures were
fabricated on Co0.9Fe0.1 films by this technique. Fabrication of magnetic nanostructures was performed by using a high
exposure dose and modifications in optimized development conditions. A thin Au film was deposited on the sidewall of
the magnetic nanostructures to avoid the oxidation of Co and Fe. The effect of this method was confirmed by X-ray
photoelectron spectroscopy (XPS). Hysteresis loops measured by a highly sensitive superconducting quantum
interference device (SQUID) technique show the different magnetic properties of the magnetic patterns with different
critical dimensions.
Light emission from controlled multilayer comprising of thin amorphous and nanocrystalline silicon carbide layers
Wei Yu,
Ligong Li,
Yachao Li,
et al.
Show abstract
The multilayer structure composed of thin amorphous and nanocrystalline silicon carbide layers (a-SiC/nc-SiC) was
prepared by the helicon wave plasma-enhanced chemical vapor deposition technique. Scanning electron microscopy and
atomic force microscopy results show that the successive layers of a-SiC/nc-SiC is reproducible and the nanocrystalline
grains can grow homogeneously for this multilayer structure. The optical emission property has been investigated by
means of photoluminescence (PL) analysis. The red-shift of PL peak energy with increasing the excitation wavelength
suggested that the optical emission originated from the quantum confinement effect of SiC nanocrystallites. A narrower
PL band and smaller PL stokes-shifts are observed from the multilayer compared with normal nc-SiC film.
Realization of super narrow pass-band and super narrow transmission-angle filters with one-dimensional defective photonic crystal hetero-structures
Show abstract
We systematically investigate realization of super narrow-pass-band and super narrow-transmission-angle filters with
one-dimensional defective photonic crystal hetero-structures through the transfer-matrix method. The structure consists
of a few different defective one-dimensional photonic crystal blocks. The influence of the relative bandwidth of the
defective layer, the number of periods, and the ratio of index of the high index material to the low index material in the
structures were studied. We find that when the relative width factor m and n of the defective layers are even numbers,
relatively narrower pass-angle will be achieved. When the number of periods of the structures increases, the pass-angle
will decrease exponentially. When the number of periods reaches 12, the pass-angle gets to be less than 0.002 degree. In
addition, higher ratio of the two indices in the structures corresponds to smaller transmission angle and narrower
wavelength pass-band.
Structural and optical properties of doped silicon nanocrystals: first-principles calculation
Show abstract
Structural and optical properties of the B doped, P doped and B-P codoped silicon nanocrystals have been investigated
using first-principles calculations. It was found that the codoped system tends to reduce structure distortion around B/P
impurities compared with B/P single doped systems and shows a decreased energy band gap compared with undoped
system due to there being electronic compensating effect. In addition, the spatial behaviors of density of states indicated
that codoping possesses a tendency of confining the electrons and holes around the B/P impurities, which suggests the
possibility of increasing electron emission transition rates between donor and acceptor. Moreover, the dielectric
functions calculation demonstrated that the optical absorption of codoped silicon nanocrystals have the characteristic of
the energy band gap being redshifted with respect to the undoped case together with peak appearing at lower energy side.
Optical modulator using silicon photonic crystals/nano-montmorillonite
Show abstract
In this paper, a novel compact optical modulator based on silicon photonic crystals /nano-montmorillonite is proposed.
The two-dimensional silicon photonic crystal with triangular lattice and a line defect waveguide formed by a missing
row of air holes in the Γ -K direction. The lattice constant is a, and the diameter of the holes is d=0.4a. The holes are
filled with the nano-montmorillonite electrorheological fluid, which is made of nanometer sized nano-montmorillonite.
The light modulation mechanism of the novel modulator is based on a dynamic shift of the photonic band gap. We have
investigated its light modulation performance by using the finite-difference time-domain method. The numerical results
show that an excellent optical modulator at a wavelength of 1550nm is achieved. The novel modulator has a high
extinction ratio (close to -40dB) and small size (around 10μm). It is very suitable for forthcoming photonic integrated
circuits.
Influence of nano-scale dimension on properties of transmission in metallic gratings with narrow slits
Show abstract
On metallic gratings with very narrow slits, the Fabry-Perot-like phenomenon has been found in the SP resonant
transmission: Transmission peaks appear periodically according to the increment of grating depth. We study the
phenomenon by setting constants of the structure to be at nanometer scale. The rigorous coupled-wave analysis method
(RCWA) has been used in this work. The grating structure we examined is composed of silver. Slits are filled with
dielectric. For silver, its plasma wavelength λp=110nm. We study the gratings with period of gratings d=3λp, the grating
depth h=2.5λp, width of slits is 0.22λp, and slits on the grating is filled with GaP which refraction index is 3.7. Under
this situation, there is no excited peak at the wavelength theory predicts. Next we have investigation on the transmission
of the SP resonant mode. Wavelength of normally incident TM-polarized plane wave equals period of gratings. It can be
seen from the zero-order SP resonant transmission versus the grating depths, that there is no Fabry-Perot-like
phenomenon upon the wavelength calculated from the theory, which appears evidently at greater geometry.
Transmission value falls quickly via grating depth increases. Fabry-Perot-like phenomenon is caused by energy
transmission in the slits, but nanometer scale slits will cut off the energy transmission in the slits. It's concluded that the
surface plasmons execute negative effect on transmission anomalies when the grating dimension is at nanometer scale.
It's useful for the fabrication of the sub-wavelength optical element.
New formalism in evaluation of the ground and few excited states of Hubbard chain nanostructures
Show abstract
A new, simple and efficient method is presented for calculation of the ground and a few excited states of Hubbard chain
nanostructures. By using this method, the photoemission spectral function for organic charge transfer salt TTF-TCNQ, is
calculated. For a chain with maximum 70 sites the result is in good agreement with the previous works but there is a
difference for further number of sites in the chain, which is discussed in the text with all the specifics. We also show that
a source of errors in density matrix renormalization group method for a one dimensional chain is the deficiency of the
matrix product scheme for generating the desired states of the linear chain.