This PDF file contains the front matter associated with SPIE Proceedings Volume 8428, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Nanoimprint is addressed as a novel technique to define nanometer-scaled patterns, in view of largely regular patterns as typical for photonic devices. The main techniques, thermal nanoimprint and ultraviolet nanoimprint, are characterized with respect to their system parameters as well as their processing parameters. Based on simple analytical equations the most important issues for these nanoimprint techniques are discussed and brought into a quantified form. A major impact is laid on the pattern size dependence and the need for anti-sticking precautions. The former, though not of basic impact for the highly regular devices in photonics, shows up when positive or negative type stamps are used. The latter is an ultimate must for successful separation of the imprinted sample from the stamp. It is aimed to assist the reader in developing its own critical view of nanoimprint, in the most positive sense possible. There is no doubt that photonic devices are one of the pattern types most suitable for successful definition by nanoimprint when the guidelines developed here are followed.

Colour filters using two-dimensional sub wavelength double-breasted rectangular hole, with a 250 nm period, were proposed and manufactured. Using low-cost, wafer scale thermal NanoImprint lithography, a thin metallic aluminium silicon alloy layer was patterned into two dimensional structures onto 200 mm wafer size. Process flow proposed in this paper is fully compatible with IC manufacturing line. A fine tuning of the manufactured design was proposed with arm widths ranging from 30 nm up to 60 nm, and arm lengths ranging from 100 nm up to 240 nm, keeping the period constant at 250 nm. Sub 20 nm resolution 200 mm silicon stamp, with aspect ratio larger than 5 were manufactured using electron beam lithography with proximity correction exposure strategy based on shape modification of the initial design. At the end 864 different patterns were manufactured and etched in thin 40 nm thick aluminium layer. The sub 30 nm resolution metallic patterns were then transfer from silicon wafer to transparent glass wafer to perform optical characterizations. Morphological characterizations and optical measurements of transmission spectra revealed that the optical response were very sensitive to the fine shape of the patterns etched in the metallic layer.

We demonstrate strong enhancements in the spontaneous emission intensity of emitters embedded in a printable polymer by coupling excitons to surface plasmon polaritons of metallic thin films or to localized surface plasmons of metallic nanoparticles. The nanocomposite materials are patterned by nanoimprint lithography with photonic crystal to enhance the light extraction of the polymer films. We finally show how NIL can be used to pattern metallic electrodes containing photonic crystals to couple the light-out of the plane and to pattern metallic electrodes containing plasmonic crystals showing extraordinary transmission to realize ITO-free OLEDs.

High efficiency volume Bragg gratings (VBGs) in photo-thermo-refractive (PTR) glass provide unmatched optical filtering capabilities with optical densities as high as 50 dB and linewidths as narrow as 1 cm^-1. In this work we review recent advances in VBG technologies that enabled key improvements of high efficiency grating properties and led to development of unique VBG based optical filters for Raman spectroscopy and other applications. Such narrow band notch and bandpass filters make ultra-low frequency Raman measurements possible with single stage spectrometers, therefore, largely improving optical throughput of high end Raman instruments while reducing complexity of the measurements. In this work we also present novel volume multiplexed ultra-narrow band VBG filters with high reflection at multiple wavelengths. Such multiband holographic optical elements are formed by overlapping of several high efficiency VBGs in a single glass plate. Raman spectra obtained with multiband VBG filters and single stage spectrometers, show unmatched capability of the filters to provide simultaneous access to Stokes and anti-Stokes Raman modes with frequencies as low as 5 cm^-1 at different wavelengths.

Fabrication of circular gratings formed of radially periodic circular lines is presented. It is a very simple fringes projection set-up based on holistic printing method using a axicon to generate the self-interferogramm of a Bessel beam using a transmissive cone. The new holographic optical interference scheme has been designed to produce circular lines based interferogram from a azimuthally polarized beam. The angle of the cone is adapted to cover a restricted periods range. The principle of the method is described and applied to the fabrication of a radial polarizer of sub-micron period.

We have implemented a Finite-Beam Rigorous Coupled-Wave Approach (FB-RCWA) to solve for guided-optics propagation in the presence of holographic slanted Bragg gratings, embedded in the core of slab waveguides and operated in Extreme Asymmetrical Scattering (EAS) configuration. In EAS a resonance condition can be established, as proceeding from the design parameters. Diffraction efficiency can be evaluated as the ratio of the flux of diffracted power P1, on a suitably defined cross-section along the propagation of diffracted beam, and input power P0. By FBRCWA, no limitation in the depth of grating modulation is assumed. The first-order diffracted field in resonant Bragg condition propagates along the waveguide. EAS in thick waveguides operating in highly multimodal regime can be investigated, as well as macroscopic volumes and widely extended illuminated regions up to a few millimeters. In thick slabs, η > 90% is demonstrated, for input illuminated apertures of length L ≥ Lc, where Lc is the optimum coupling length. The effects of detuning from Bragg condition, both in distribution and amplitude of the diffracted field, are quantified. Diffraction efficiency, i.e. optical coupling, bandwidth is evaluated.

Known since a long time in polymer banknotes and presented in the few years in paper banknotes, the principle of windowed documents has been currently extended to ID documents. We present an innovative solution which combines resonant transmission and Zero Order Device technologies and which is dedicated to improve windows in terms of the overt security level. With this R&D program, Hologram Industries targeted to obtain an overt visual security device that should be readily checked in transmission in the same manner as the established paper watermark. The proposed solution is based on the propagation of resonant modes in a thin continuous corrugated metallic layer embedded (encapsulated) between two dielectric layers of near equal refractive index. The mode of most interest is the Long Range Plasmon Mode. The coupling condition to the Long Range Mode is principally related to the corrugation, the metal layer thickness and the index of the two dielectric layers. If the condition of the mode excitation through the grating is fulfilled, a predetermined wavelength will be coupled to the Long Range Plasmon Mode. This mode will propagate at each metal/dielectric interface with a low loss and will concentrate the electric field inside the metal layer. This effect of coupling enables the transmission of a peak at this wavelength through the metallic layer. It defines the so called "extraordinary resonant transmission".

We demonstrate volume Bragg gratings inscribed in S-TIH53 glass. S-TIH53 is in the proper meaning not photosensitive; therefore we used a fs-laser system for the inscription process. The grating structure was formed in a Talbot interferometer and was investigated with help of the external Bragg reflection method. With this method we could measure the reflectivity profile and thereto the size of the grating. To ensure that the generated gratings are no surface or absorption gratings the probes were investigated by a microscope and absorption measurements and heating experiments were done.

Fiber-To-The-Home (FTTH) networks have been adopted as a potential replacement of traditional electrical connections for the 'last mile' transmission of information at bandwidths over 1Gb/s. However, the success and adoption of optical access networks critically depend on the quality and reliability of connections between optical fibers. In particular a further reduction of insertion loss of field-installable connectors must be achieved without a significant increase in component cost. This requires precise alignment of fibers that can differ in terms of ellipticity, eccentricity or diameter and seems hardly achievable using today's widespread ferrule-based alignment systems. Novel low-cost structures for bare fiber alignment with outstanding positioning accuracies are strongly desired as they would allow reducing loss beyond the level achievable with ferrule-bore systems. However, the realization of such alignment system is challenging as it should provide sufficient force to position the fiber with sub-micron accuracy required in positioning the fiber. In this contribution we propose, design and prototype a bare-fiber alignment system which makes use of deflectable/compressible micro-cantilevers. Such cantilevers behave as springs and provide self-centering functionality to the structure. Simulations of the mechanical properties of the cantilevers are carried out in order to get an analytical approximation and a mathematical model of the spring constant and stress in the structure. Elastic constants of the order of 10⁴ to 10⁵N/m are found out to be compatible with a proof stress of 70 MPa. Finally a first self-centering structure is prototyped in PMMA using our Deep Proton Writing technology. The spring constants of the fabricated cantilevers are in the range of 4 to 6 × 10⁴N/m and the stress is in the range 10 to 20 MPa. These self-centering structures have the potential to become the basic building blocks for a new generation of field-installable connectors.

In this paper details on the analysis and optimization of a flexure-based micromanipulator for the alignment of optical components will be presented. The developments are motivated by a concept for flexible precision assembly that will be described in the first section. The development of the manipulator itself is based on a systematic approach to first define suitable kinematical structure for a six-axes device. The kinematics have modeled to allow mathematical analyses of the main geometric parameters on relevant performance characteristics. A stepwise optimization procedure has been developed to define the smallest possible configuration of the mechanism for specific workspace requirements. The realized design of the manipulator will be presented which is taking into account further design aspects such as the choice of suitable actuators and the design of flexure joints. By means of interferometer measurements a motion resolution in the nanometer range could be proved as well as a high repeatability of 0,15 μm.

We report on the fabrication of the minimized conventional microoptical components out of the hybrid organic- inorganic SZ2080 and SG4060 photoresins using laser direct writing technique. An ascending laser focus multiscan approach is introduced as a method for the structuring of 2D nanolines. The diameters and heights of the nanolines are comparable to the ones written with the electron beam lithography. Using our proposed laser direct writing approach one can write 3D microstructures with the 2D nanofeatures in a single step procedure. As demonstration of this technology, microlenses with 1D, 2D and circular transmission gratings were fabricated. Additionally, for the rst time, ISO certied laser-induced damage testing was applied to determine the optical breakdown threshold of the SZ2080 photoresin used for the laser direct writing.

The pyroelectric functionality of a Lithium Niobate (LN) substrate is used for non-contact manipulation of polymeric material. In this work we introduced a novel approach for fabricating a wide variety of soft solid-like microstructures, thus leading to a new concept in 3D lithography. A relatively easy to accomplish technique has been demonstrated for curing different transient stages of polymer fluids by rapid cross-linking of PDMS. The method is twofold innovative thanks to the electrode-less configuration and to the rapid formation of a wide variety of 3D solid-like structures by exploiting polymer instabilities. This new and unique technique is named "pyro-electrohydrodynamic (PEHD) lithography", meaning the generation of structures by using forces produced by electric fields generated by the pyroelectric effect. The fabrication of polymer wires, needles, pillars, cones, or microspheres is reported, and practical proofs of their use in photonics are presented.

We report on a simple method for the collective fabrication of polymer tunable microlens arrays suitable for VCSEL active beam shaping. Its principle is based on a SU-8 suspended membrane, surmounted by a polymer microlens, and thermally actuated to achieve a vertical displacement of lens plane. SU-8 resist presents many advantages for MOEMS fabrication, as this resist allows for high aspect ratio patterns and high transparency. In addition, it exhibits a thermal expansion coefficient suitable for thermal actuation. Moreover, this kind of polymer MOEMS can be fabricated on VCSEL arrays with footprints as low as 500x500μm² enabling a rapid, low cost and wafer-scale integration technology. We have successfully fabricated this MOEMS on a glass substrate by means of a SU-8 double exposure method and we report on a vertical displacement of 8μm under an applied power of 43mW (3V). A good agreement with the theoretical thermo-mechanical behavior is found. Moreover, optical measurements of microlens focus displacement under actuation are presented. We evaluate analytically the focus properties of the system under coherent laser illumination, using the classical ABCD matrix formalism of Gaussian transformation optics. The same approach enables one to assess its tolerance to opto-geometrical parameters, such as refractive index or dioptre curvature. As a wide range of initial gaps between the membrane and the substrate can be chosen, this MOEMS technology opens new insights for dynamic control of VCSEL beam or for tunable VCSELs fabrication.

Here the pyroelectric functionality of a Lithium Niobate (LN) substrate is used for non-contact manipulation of liquids. In this work we introduced the use of a pyro-electrohydrodynamc (PEHD) dispenser for the manipulation of high viscous polymer materials leading to the fabrication of arrays of microlenses. The set-up used for the experiment is described and the fabricated microlenses are analyzed by means of the Digital Holography (DH) set-up in transmission mode and through profilometric analysis. PMMA based ink was employed for the realization of optical quality microsctructures whose geometrical properties and, hence, the focal lengths were controlled by modifying the printing configuration of the PEHD method. The profilometric results are in agreement with those calculated using the digital holography technique.

A digital holographic characterization of Bessel beams produced by polymeric microaxicons is reported. Both intensity and phase of the beam can be numerically reconstructed in whichever point starting from a single acquired hologram. Optical parameters such as the full width at half maximum, the focal length and the depth of focus of the axicon lens are experimentally measured. The Bessel beam exiting from the axicon, with a very large depth of focus with respect to that of a Gaussian beam, is successfully exploited for optical trapping of micrometric objects.

In this paper we report on the fabrication, optical properties and imaging capabilities of nanostructured gradient index microlenses with diffraction limited performance and good chromatic behaviour. We introduce a new fabrication concept for the development of large diameter nanostructured gradient index microlenses based on quantised gradient index profiles and the use of nanostructured meta-rods. We show the dependence of the quality of performance on the number of refractive index levels and the overall lens diameter. The practical limit of the proposed method for fabricating nanostructured GRIN microlenses is determined to be 120μm for 7 discrete levels of nanostructured meta-rod refractive index. The fabricated microlenses show good achromatic behaviour - the observed working distances for illumination at wavelengths of 633 nm and 850 nm are 43μm and 40μm, respectively, while the focal spot sizes remain the same for both wavelengths

We present the design and fabrication details of a customised nanostuctured form birefringent material based upon a second order effective medium theory composite composed of two mechanically and thermally matched soft glasses. The design, which shows uniform birefringence over several hundred nanometres, is fabricated using a modified stack-and-draw method to produce a final element with feature sizes in the 50-100nm range. A method for measuring the effective birefringence of the composite material is presented along with the preliminary results from the fabricated component.

This paper presents a highly effective micromachining process that can reform a section of an optical fiber into an allfiber, complex photonic microstructure. The proposed process utilizes specially designed structure forming fibers that are reformed into various complex shapes through selective etching. The control over the etching rate of the structureforming fiber sections is achieved by the introduction of dopants, particularly phosphorus pentoxide, into silica glass through the standard fiber manufacturing technology. Doping with appropriate dopants and dopant concentrations can be used to create highly-preferential etchable areas within a fiber cross-section that can be selectively removed upon exposing the fiber to the etching medium. The doped areas in the fiber cross-section can thus serve as sacrificial layers, similar to those in the case of silicon MEMS production. Thus, the shaping of fiber devices can be achieved through the design and fabrication of structure-forming fibers.

Certain spider webs are composed of several types of micro-optical elements made from transparent optical materials. The silks (radial and capture) are almost exclusively protein. The nearly cylindrical silks have diameters in the range 0.1 to several microns and cross-sectional morphology that is cylindrical-multi-layered,.as studied by transmission electron microscopy, The capture threads are coated with aqueous adhesive that also forms into nearly elliptical micro-lenses (adhesive droplets) mounted on the near cylindrical silks. The remaining elements of the web are the cement junctions tying the radial and the capture threads of the web together. These are irregularly shaped platelets. Progress to date on our research characterizing the optical properties and function of these transparent orb webs has been to interpret the reflection and transmission properties of the elements of the web, and the web as a whole, in natural lighting; to evaluate the optical finish of the surface of the silks and capture droplets; and to measure the principal refractive indices of radial silks using new immersion based methods developed for application to micron-sized, curved optical elements. Here we report the principal refractive indices, birefringence, dispersion and morphology of transparent spider silk subject to various chemical treatments. The morphology is measured using TEM. Insight into the physical origin of the refractive index properties will be discussed.

In previous research we introduced an experimental methodology in which focused-ion-beam (FIB) sectioning, followed by secondary ion (SI) and secondary electron (SE) imaging, was used for testing the internal material homogeneity of silica and chalcogenide glass microspheres. The methodology is readily applied to micro-optics with dimensions of a few microns. The use of both SI and SE imaging of the sequentially sectioned samples was shown to allow accurate assignment of inhomogeneities, voids and other imperfections as being within the footprint of the micro-optic. On larger micro-optics FIB sectioning can become prohibitively time intensive and can require the use of too much platinum in sample preparation for evaluation of the bulk of the micro-optic. However, improved sample preparation and image analysis has enabled high magnification and high sensitivity study of the glass near the surface of chalcogenide microspheres with diameter of order 70μm. The chalcogenide glass is Ga₂S₃/La₂S₃, in a 70/30 weight percent ternary (GLS) and the microspheres had been kept in air, in normal laboratory conditions, for about two years prior to testing. Evidence of an altered layer with a width of the order of 0.1μm near the surface and then an outer porous layer at the surface was found. Lower resolution studies are then reappraised in light of the high resolution measurements.

Some applications like the development of lithographic systems require a possibility to focus EUV and x-ray radiation, but for those wavelengths no transparent material exists. For that reason the use of diffractive lenses is interesting [1]. The classical Fresnel zone plate (FZP) is in theory a good solution but the individual rings need to be hold in place. An alternative is given in [2] but to keep the main structure of an FZP one can use bridges which connect the rings to each other. The resulting structure is called azimuthally structured Fresnel zone plate (aFZP) and can be described with the following parameters: The number L of rings, the number M of openings in the innermost ring and the increase of openings ▵M for each ring moving outwards. Figure 1.a) shows the classical FZP with alternating opaque and transmitting zones. Figure 1.b) shows the aFZP with bridges to hold the rings in place. A similar structure has been investigated by Mitsuishi et al. [3]. Reasonable experimental results of the diffraction characteristics were shown. The corresponding anlytical model is explained here.

A novel see-through screen is developed for automobiles which reduces the size of the head-up display (HUD) unit considerably. The screen is illuminated by a laser scanning pico-projector and a real image is formed on the screen. The screen has thousands of hexagonally packed microlenses that are partially reflective and embedded in an index matched medium which provides very good see-through capability. Light reflected from the microlenses expand and form a hexagon shaped viewing window. This system is called a direct projection HUD system as the pico projector projects directly onto the screen and forms a real image on it. The system is very compact and does not require any space under the dashboard, which saves on space for the car manufacturers, or allows it to be used immediately as an aftermarket HUD installed in any car.

We present a Fourier transform interferometer that is capable to record single short pulses and fast continuous transient spectra. This is achieved by spatially parallel instead of time serial processing by means of a micro/nanomanufactured multimirror array and a pixellated detector camera. The multimirror array is produced in excellent optical quality from poly(methyl methacrylate) by means of deep X-ray gray level lithography including multiple moving masks followed by sputter deposition of the gold reflecting surfaces. The crucial components such as the multimirror array and the pixellated camera are part of a straightforward optical system similar to a Czerny-Turner mount. Results demonstrate single shot measurements down to 320 μs, only limited by the camera shutter and the infrared source, and the time evolution of the absorption spectrum of an evaporating acetone layer that shows spectral changes during the first few seconds. While the spectral range of the multichannel Fourier transform interferometer (MC FTIR) as reported extends from near to mid infrared, multimirror arrays can be produced for spectra from visible to far infrared. Thus, the potential performance depends mostly on availability of detectors. The minimum pulse duration is determined by that photon number in the pulse which yields a sufficient signal to noise ratio, whereas the maximum acquisition rate of continuous transients is given by the frame rate of the detector.

We present micro-optical detection units for both laser-induced fluorescence and absorbance analysis. The detection systems are designed by means of non-sequential ray tracing simulations and prototyped by means of deep proton writing. In a proof-of-concept demonstration, the micro-optical unit is used for the detection of various concentrations of coumarin dyes. Several measures to increase the signal-to-noise ratio, such as automation of the sample injection, improved suppression of environmental stray light, usage of optimal detectors and simple yet effective post-processing of the raw detection signals are implemented, resulting in a concentration measurement range for fluorescence from 6pM up to 0.6mM and for absorbance from 0.6μM to 12mM. The wide measurement range and the possibility of using standard fabrication techniques to prototype and replicate this miniaturized plastic system, make it a good candidate for applications where small samples need to be characterized optically with a low-cost and portable system.

A compact twin-beam interferometer that can be adopted as a flexible diagnostic tool in microfluidic platforms is presented. The devise has two functionalities, as explained in the follow, and can be easily integrated in microfluidic chip. The configuration allows 3D tracking of micro-particles and, at same time, furnishes Quantitative Phase-Contrast maps of tracked micro-objects by interference microscopy. Experimental demonstration of its effectiveness and compatibility with biological field is given on for in vitro cells in microfluidic environment. Nowadays, several microfluidic configuration exist and many of them are commercially available, their development is due to the possibility for manipulating droplets, handling micro and nano-objects, visualize and quantify processes occurring in small volumes and, clearly, for direct applications on lab-on-a chip devices. In microfluidic research field, optical/photonics approaches are the more suitable ones because they have various advantages as to be non-contact, full-field, non-invasive and can be packaged thanks to the development of integrable optics. Moreover, phase contrast approaches, adapted to a lab-on-a-chip configurations, give the possibility to get quantitative information with remarkable lateral and vertical resolution directly in situ without the need to dye and/or kill cells. Furthermore, numerical techniques for tracking of micro-objects needs to be developed for measuring velocity fields, trajectories patterns, motility of cancer cell and so on. Here, we present a compact holographic microscope that can ensure, by the same configuration and simultaneously, accurate 3D tracking and quantitative phase-contrast analysis. The system, simple and solid, is based on twin laser beams coming from a single laser source. Through a easy conceptual design, we show how these two different functionalities can be accomplished by the same optical setup. The working principle, the optical setup and the mathematical modeling for 3D tracking is described. Finally, the experimental proof is presented and discussed for in vitro cells in microfluidic chamber.

Whispering-gallery mode (WGM) resonators are known to offer outstanding properties for applications in photonics and telecommunication. Despite their promising performance, one major obstacle for the use of WGM resonators in industrial products is the need of expensive components and high-precision setups for their operation, requiring a controlled lab environment. For industrial applications technically simpler and more robust realizations are desired. Active WGM resonators utilize an optical gain medium for light amplification within the resonator and may be operated as lasers. They offer several advantages over their passive counterparts, such as cheap pump sources, free space excitation of resonator modes, and potentially narrower line widths. However, collection of the light emitted from the resonator still bears several challenges. Emission occurs in plane of the resonator and radiation is emitted isotropically along the circumference. Thus, detectors positioned in plane of the resonator may collect only a limited angular segment of the resonator's light emission. We report on a microoptical device which is integrated on the resonator chip and redirects all in-plane emission of active WGM resonators into a defined off-plane direction. Redirected light can easily be collected using a standard detector. Contrary to other approaches our microoptical device does not decrease the quality factor (Q factor) of the resonator. As light from all angular segments of the resonator is collected, the detected signal-to-noise ratio is expected to be largely improved. Our microoptical device therefore offers a promising approach towards mass-producible integration of active WGM resonators, e. g. into a Lab-on-a-Chip, for sensor applications, where smallest possible frequency shifts need to be read out by a highly sensitive detector.

In this paper we discuss the geometrical and optical characterization of a miniaturized very wide field-of-view (FOV) motion sensor inspired by the working principle of insect facet eyes. The goal of the sensor is to detect movement in the environment and to specify where in the surroundings these changes took place. Based on the measurements of the sensor, certain actions can be taken such as sounding an alarm in security applications or turning on the light in domotic applications. The advantage of miniaturizing these sensors is that they are low-cost, compact and more esthetical compared to current motion detectors. The sensor was designed to have a very large FOV of 125° and an angular resolution of 1° or better. The micro-optics is built up of two stacked polymer plates consisting each out of a five by five lens array. In between there is a plate of absorbing material with a five by five array of baffles to create 25 optically isolated channels that each image part of the total FOV of 125° onto the detector. To geometrically characterize the lens arrays and verify the designed specifications, we made use of a coordinate measuring machine. The optical performance of the designed micro-optical system was analyzed by sending white light beams with different angles of incidence with respect to the sample through the sensor, comparing the position of the light spots visible on the detector and determining optical quality parameters such as MTF and distortion.

Low-loss polymeric optical waveguides were fabricated by UV-nanoimprinting. With this technique the waveguides are directly patterned by imprinting of the UV-curable optical polymer materials, i.e. no etching processes are needed. By properly manufactured imprinting molds, very smooth waveguide surfaces are achieved and the optical loss is dominated by the material attenuation. The advantages of the manufacturing technology include the potential scalability onto large substrate areas and applicability for fabrication on various substrate materials. For instance, printed circuit boards are interesting substrates for high-bit-rate optical interconnection applications requiring long waveguides, and glass and plastic sheets are interesting for sensor applications. The technology also promises for low overall costs, as it is a relatively simple high-throughput replication process. Both ridge-type and inverted-rib-type single-mode waveguides were fabricated using Ormocer hybrid polymer materials having low optical attenuation. Very low loss waveguides were demonstrated by fabrication long waveguides in a spiral shape. The optical attenuation was characterized of 27 cm-long inverted-rib waveguide spirals having 2 μm-wide cores. The measured average attenuation was 0.25 and 0.56 dB/cm at the wavelengths of 638 and 1310 nm, respectively.

The control of very small distances is essential for many applications and alignment procedures in the field of micro technology, e.g. micro lithography for MEMS or micro optics, where proximity lithography is often used for cost effective mass fabrication. Also in proximity lithography the requirements, especially for resolution, are increasing permanently. Recently new techniques have been developed to get sub-micron resolution even for larger distances between mask and substrate. But then also the proximity distance has to be controlled with sub-micron accuracy. A passive and an active sensor concept have been developed based on triangulation using diffractive structures. The required sensing patterns are implemented directly in the photo mask. In the passive gap alignment the distance can be reconstructed from the resist pattern obtained as a result of a lithographic step in which the diffractive sensor structure is exposed in the Mask-Aligner. In the active configuration the proximity gap can be controlled already during the alignment procedure prior to the lithographic exposure. A collimated laser beam irradiates a diffractive structure in the photo mask, which deflects the beam which will be reflected from the resist coated substrate towards the mask. A second mask structure, which is placed in a defined lateral distance to the first one, acts then as a ruler for the distance between mask and wafer and can be observed through the alignment microscope or a camera module. The design and fabrication of the diffractive structures, the measurement results for the full-wafer proximity distance distribution according to the passive method, as well as the realization of an active sensor module for mask aligners are presented in this paper.

Micro-fabricated cantilevers have been reported recently as miniaturized, rapid response, ultrasensitive sensors elements suitable for various chemical and bio-sensing applications. However, the alignment of the cantilever with the optical read-out system can be challenging and typically involves a bulky free-space optical detection system. We propose using cantilevers aligned to the core of an optical fibre during the fabrication process to address this issue. Focussed Ion Beam (FIB) machining has been demonstrated as capable of fabricating fibre-top cantilevers. Here we demonstrate techniques to design and fabricate micro-cantilevers using a combination of laser machining and FIB processing to fabricate sensing cantilevers onto the end of standard and multi-core fibres (MCF). In this way the cantilever can be aligned with the core of the fibre therefore offering stable and accurate means of optically addressing the cantilever. Use of MCF offers the potential for a single probe capable of making multiple measurements in a confined measurement volume, to determine multiple species of interest, or to provide background reference measurements for example. The optical cavity formed between the fibre and the cantilever is monitored using low-cost optical sources and fibre coupled spectrometers to demonstrate a practical measurement system. This can readily achieve <50nm resolution using analysis based upon recovering the free spectral range using the Fast Fourier Transform to calculate the final cavity length.

We investigated high efficiency organic-inorganic hybrid sub-wavelength binary diffraction gratings as partially athermalized waveguides. The performance of the grating is evaluated in terms of low spectral shifts in heating environment. The efficiency was determined to be least effective in temperature environment around room temperature. The spectral characteristics of waveguide remain thermally stable by selecting optical grade polymer materials with high thermal expansion coefficients, subsequently deposited by high index, amorphous TiO₂ thin films by atomic layer deposition (ALD) process. The spectral shifts towards longer and shorter wavelengths were investigated in terms of two main parameters, thermal expansion coefficient (TEC) and thermo-optic coefficient (TOC) respectively. Realization of partially athermalized waveguides are described by complete agreement in theoretically calculated and experimentally measured results in the temperature range of 100 °C.

The paper present the design and the construction of a novel 3-D micromirror optical scanner for use in a swept-source optical coherence tomography (SS-OCT) that is based on external-cavity tunable lasers. The 3D rotating octagonal micromirror consists of a rotary platform, onto which the micromirrors are assembled in an octagonal configuration. The 3D optical scanner was constructed in a two stage process. It was first fabricated using surface micromachining PolyMUMPs fabrication process, and then assembled using a robotic micromanipulator system. The microassembly process is a robotic-based process based on the PKMIL system.The methodology to construct the micromirror and the design of the micromirror parts, and the results of the assembly process are presented, along with examples of prototype of the 3D micromirrors.

In certain applications of MOEMS devices, it is often necessary to produce microlens array structures that concentrate optical power in semiconductor photodetectors. In this work, the design and fabrication of a low f-number cylindrical microlens array is presented. The lenses were fabricated in thick photo resist - 12 μm thick - using a contact printer exposure through a mask with a repetitive 6 μm line - 4 μm space pattern. The width of the resulting microlens array was determined to be 10 μm, with f-number of 0.5. Numerical calculations based on scalar diffraction theory were employed to model the light propagation inside the resist, determining the aerial image as a function of its thickness. Than the resist response characteristics, expressed by its contrast curve, and absorption rate were used to obtain a cross section profile. A good match between numerical and experimental results were found.

We fabricated a subwavelength-grating structure on the Y₂O₃ ceramic substrate, which has higher transparency than silicon in the mid-infrared range. After coating a photoresist on this substrate, we formed a grating pattern of 350-nm pitch by the two-beam interference of the He-Cd laser (325-nm wavelength). By using this photoresist grating as a mask, WSi was etched with reactive SF6 ions. The transmittance of the transverse magnetic (TM) polarization was greater than 70% in the 3-7-μm wavelength range without antireflection films and the extinction ratio was over 20 dB in the 2.5-5-μm wavelength range. In addition, we also fabricated near-infrared wire-grid polarizer consisting of a 230-nm pitch WSi grating on a SiO₂ substrate. The TM polarization transmittance of the fabricated polarizer exceeded 80% in the 1000-1600-nm wavelength range. The extinction ratio was higher than 20 dB in the 650-1500-nm wavelength range.

Unique industrial transfer of write on the fly technique, to produce long and large sub-micron period gratings on an industrial and commercial laser beam generator (Dilase 750 from KLOE company) has been successfully achieved. The write on the fly technique, enabling to produce stitchingless long gratings, is based on a continuous interferogram, generated by a high efficiency phase mask, illuminated with a laser beam and projected onto a photosensitive film. As the substrate is continuously moving, the technique is able to write large size gratings, limited by the displacement range of the machine. Demonstration is made on photopatternable solgel thin films (TiO₂ xerogel film) on which 600 nm period gratings, several cm long and a few mm wide were written. This demonstration opens the way to cost-effective and rapid demonstrators and extends the possibilities towards high volume products.

Direct laser writing has been already demonstrated for the fabrication of under surface "buried" 3D mid-IR waveguides in chalcogenide glasses by employing a large photo-induced refractive index change in the features formed in the path of the focused beam from a short pulse laser. In this paper, we report on direct laser writing of relief diffraction gratings with periods of 6, 14 and 24 μm into the surface of Ge₁₅Ga₃Sb₁₂S₇₀ chalcogenide glass by using a 800 nm Ti:saphire femtosecond pulse laser. The first order diffraction efficiency of the fabricated gratings was over 60 % at 650 nm. We have also fabricated a "composite" grating composed of three relief diffraction gratings inscribed in the same position, but with a mutual tilt. Composite grating provided complex multidirectional diffraction of the light in the accordance with geometrical arrangement and grating period of all the gratings inscribed. The fabrication was implemented on a computer controlled stage employing surface-to-beam alignment, laser power and raster pattern control. Pulse energies of 1.5, 3.0 and 4.5 μJ were used, resulting in channel widths of around 4, 5 and 6 μm, respectively, and depths up to 1.7 μm. We propose practical applications including surface relief diffraction micro-gratings at the ends of multimode chalcogenide optical waveguides or on the surfaces of bare core optical fibers used for chemical sensing.

We investigate application of acousto-optic cells based on a TeO₂ crystal to stabilize a microwave signal generated by an optoelectronic oscillator (OEO) based on a MgF₂ resonator. Bulk acoustic waves at two radio frequencies (RF) near 60 MHz are launched in the two identical cells providing a required locking on of a microwave signal. When quality factor of the optic resonator is typically of the order 10⁸, difference between RF signals are up to 2 MHz. We send an extraordinary polarized laser beam on ultrasound at very low Bragg angle of light incidence. It helps to perform a critical alignment of the two cells.

Optical interconnection at high-speed and large-capacity transmission of data has the advantage of conveying information at large bandwidths in free space with less crosstalk than electronics. We propose here the design of micro-optical devices based in the multi-aperture compound insect eyes that will transfer a signal as a freespace multichannel point-to-point interconnection. These designs are inspired in the configuration of the superposition refractive compound eye as Gabor superlens by means of the implementation of microlens arrays. In our configuration the design equations, simulations, and optical performance are shown.

Fluid driven devices have been widely used in many applications, such as pumping, circulating, and cooling systems in handling liquid. Their driving conditions are highly dependent on the operation purposes. Some of them work with high pressure and high flow rate without the need of flow stability. On the other hand, the steady flow with low pressure and flow rate is required for bio-applications. In a perfusion system for culturing cells, a suitable shear stress from a cultivated fluid is one of key factors to reproduce the fluid conditions of cells in a living organism. A special pump is needed to provide a steady flow rate and stress in such system. In this study, a novel design of the pump constituted by a housing and a screw-type rotor with micro-channels was proposed. To understand the flow phenomena in this design, both computational modeling and real experiment are utilized. In the experiment, a minimum rotational speed is needed to drive the fluid flow. In the modeling, the steady state with low pulsation was achieved within a short period of time. A perfusion system with 7.8% variation in flow rate could be obtained in comparison with traditional peristaltic pump with up to 29% variation in flow rate. Steady fluid flow for a perfusion system then could be obtained in this screw-type pump.

This paper reports a batch-fabrication technique based on micromachining of silicon molds to create, after replication, arrays of microlenses characterized by high fill factors. The technique for single microlens generation (compatible with various types of replication or integration so that microlenses made of plastics or glass can be generated) was reported previously and showed its potential in terms of range of shapes and cost. However, subtleties of chemical etching makes more difficult the generation of high fill factor matrices when microlenses size overcomes several tenth of microns. Thus, in this paper, we describe the analysis of the chemical etching process and the corresponding adaptation of the mask design to achieve 100% fill factors arrays of microlenses. The process to fabricate arrays of microlens, with hexagonal footprints and element sizing from 30 to 270 microns and having NA from 0.2 to 0.4, is described. The hexagonal footprint shape of the elements in the arrays leads to 100% geometrical fill factor of fabricated structures. Isotropic etching used for the molds fabrication preserves the spherical profile of the resulting microlenses.

In this paper, we have introduced a method for design and fabrication of a micro-windmill based on SU-8 photoresist that is rotated by gas flow. This device is used for measuring gas flow by assessment of rotational speed of the microwindmill. The flow-meter sensitivity is influenced by different parameters such as number of blades and dimension of the windmills. Therefore, we have tried to experimentally reduce the dimensions and increase of the number of blades to obtain the higher sensitivity in measuring gas flow. An experimental setup is arranged to measure the rotational frequency of the windmill as a function of gas flow with optical methods.

Many applications in micro and nanotechnologies require micron-sized components, capable of positioning in ranges of sub-micrometers to a few microns. This paper reports on the design, fabrication and characterization procedure of an electrostatically actuated polymeric Nano-precision micro z-stage. Due to its ease of fabrication and great variety of functionalities, polymers have become an important material in micro fabrication technology. In contrast to piezoelectric stages, polymeric micro stage has a comparatively simple and cost effective fabrication procedure. Furthermore, low Young's Modulus of polymers made them a suitable basic material in comparison with their traditional counterparts. In this paper, SU-8 photoresist was used as the construction material and the photolithography technique were used to realize the stage. SU-8 with its low Young's modulus (5 GPa), has a higher tendency for bending, compared to, for example, silicon nitride (150-350 GPa). These properties make the SU-8 polymer, suitable for various applications.

In this contribution we simulate theoretically the resulting 3D Talbot-carpets of different initial close-packed 2D mask structures. Especially, we investigate the transition from regular periodic to quasi-periodic tessellations. For the pure periodic mask structure a hexagonally tessellation was selected. The calculated field distribution adjacent to the mask still shows a lateral six-fold symmetry but also a rather complex characteristics in the propagation direction. In particular, the appearance and the repetition of self-imaging planes deviate significantly from the classical Talbot-effect. For the quasi-periodic tessellation a Penrose tapestry based on rhombus pairs was chosen. A pronounced lateral fivefold symmetry becomes visible in the field distribution. In the propagation direction dominant planes with increased intensity are observed clearly, but, instead of a simple periodicity, a complex behavior becomes obvious. The numerical algorithm used in our simulations is based on a modified angular spectrum method, in which Bluestein's fast Fourier (FFT) algorithm is applied. This approach allows to decouple the sampling points in the real space and in the spatial frequency domain so that both parameter can be chosen independently. The introduced fast and flexible algorithm requires a minimized number of numerical steps and a minimal computation time, but still offers high accuracy.

We propose and demonstrate a novel refractive index (RI) measurement by using the numerical-sample-motion based the defocus correction method in full field optical coherence tomography (FF-OCT). Overcoming the general problem in FFOCT that is the position of the focal plane is separated from the position of the image plane when imaging a deep region inside a sample, we measure the separation distance from the position of the focal plane to the position of the image plane. The RI is determined from the separation distance that is obtained by the numerically adjusted distance of a sample position. With the proposed method, the depth resolved RIs of double layer materials are determined.

This paper reports on the application of sub-wavelength structured single layer reflectors in a Fabry-Perot-Interferometer (FPI) that are used in order to replace distributed Bragg reflectors (DBR). A pair of two-dimensional arrays of ring resonators was analyzed. A 100 nm thin Al layer is regularly patterned to form a meta-surface structure. It shows high reflectance in a sufficiently wide wavelength range. This design approach has the advantage that an optimization can be done by varying geometry parameters of lateral structures only. Moreover, the material is highly compatible to standard MEMS processes. The structures used here are rings that are arranged in a two-dimensional array. Thus, parameters to be varied are the inner and the outer ring diameters and the array pitch. The optimum dimensions of the metal rings have been found iteratively. Samples were fabricated by structuring of two silicon wafers and subsequent wafer bonding. Deep dry etching of the reflector carriers from the back side in the areas of the resonator arrays results in free standing silicon nitride membranes that carry the resonators. The carrier membranes elastically suspend the reflecting ring resonators for variation of the cavity width. Finally, the substrates are assembled by a wafer bonding technique utilizing a SU-8 polymer layer with a very definite thickness. A peak transmittance of 55%, a bandwidth FWHM = 100 nm and a modulation contrast of M = 50:1 were achieved. The optical performance was measured by fourier transform infrared spectrometer and compared to the simulation results. It shows a widely good agreement of calculation and measurement.

In this paper we report on the development of diffractive and refractive micro optical components devoted to MidIR applications. As a material we use a customized heavy metal oxide glasses with high transmission in the range 0.6÷6.0μm. Optimization of the glass composition in four- and five-component oxide systems for a broadband transmission window is difficult due to their excessive crystallization susceptibility. Several metals and alloys were tested for their suitability as a stamping medium. Optimal performance was obtained for selected brass and steel stamps, as well as for pure silica stamps. As a technology testboard we have developed 1D and 2D diffractive gratings with a minimum feature size of 5μm as well as Fresnel microlenses with a diameter of 200μm. The quality of the embossed elements was verified by comparison of the master and replicated elements using a non-contact white light interferometer.

We present a novel approach to the fabrication of diffractive optical elements. Unlike traditional diffractive optical elements, the different phase shifts are obtained through a refractive index variation by using different types of glass. This approach results in a completely flat element which is easy to integrate with other optical components. For fabrication of the test DOE structures we have used the stack-and-draw technique. This method, which was originally developed for the fabrication of photonic crystal fibres, has been modified to allow the fabrication of nanostructured micro-optical components. In this paper we present the results from proof of concept periodic checkerboards fabricated on a square and hexagonal lattice with feature sizes of 8μm and 46μm. The components were fabricated from two types of rods made of the low refractive index silicate glass and the high refractive index of lead-silicate glass. The measured characteristics of the fabricated components are presented The influence of fabrication-induced structure distortions on the optical performance of the components is discussed.

We present investigations of light-scattering thermal cross-link package film based on self-assembly for liquid crystal display using light emitting diode. Thermal cross-link package films based on selfassembly indicated good nano regularly-structured patterning for light-scattering, excellent environmental stability of optical parameters, and solvent intermixing resistance after thermal cross-link reaction. The developed light-scattering thermal cross-link package film-s based on self-assembly is one of the most promising processes ready to be incorporated into the mass production of patterning light-scattering optical layer for advanced liquid crystal display, organic electroluminescent display, and solar cell devices.

Nanopatterning printability due to high sensitivity and low film thickness shrinkage of ultraviolet curing process in resist material was one of key to achieve high resolution and quality of nanoimprint lithography. The new ultraviolet curing plant-based resist material derived from biomass was investigated to achieve high quality of 100 nm line and space patterning images in the optimized conditions of ultraviolet curing nanoimprint lithography technology for the optical films containing light-emitting diodes, solar cell devices, actuators, biosensors, and micro electro mechanical systems. The newly plantbased resist material derived from biomass is expected as one of the nanoimprint lithography technology in next generation optical devices and biosensors.

A water developable, non-chemically amplified, high sensitive, and negative tone resist material in the developable process of EB lithography was investigated for environmental affair, safety, easiness of handling, and health of the working people, instead of the common developable process of trimethylphenylammonium hydroxide or resist solvents. The material design concept to use the plantbased resist material derived from biomass was proposed. A novel high-sensitive negative tone of plantbased resist material with the sugar chain structure derived from biomass on underlayer was demonstrated in EB lithography for the future production of optical and electronic devices. The 400 nm line patterning images with exposure dose of 7.0 μC/cm² were provided by specific process conditions of EB lithography for optical and electronic devices.

A deformable mirror based on the principle of total internal reflection (TIR) of light from an electrostatically deformed liquid-air interface was realized and used to perform closed-loop adaptive optical correction on a collimated laser beam aberrated by a rotating phase disk. The liquid system was characterized including open- and closed-loop frequency responses, determination of rise-times, the damping times of the liquid, and the influence of liquid surface motion in the absence of external optical aberrations. The dynamic behavior of the liquid was found to be dominated by gravity waves and the results of the experimental realization were in good agreement with the predictions of the theory. A miniaturization of the system promises to eliminate the dominant gravity waves and considerably reduce the errors introduced by ambient vibrations. Here we explore the possibilities of such a micro mirror and establish the boundary conditions and requirements for its realization.

A new approach for obtaining in short time highly efficient photorefractive holographic gratings in lithium niobate is presented. The method consists in decreasing the sample conductivity by cooling it down to liquid nitrogen temperature. In this way the initial slope of the writing curve is largely amplified, which makes possible to achieve in short time diffraction efficiencies one order of magnitude larger than at room temperature in the same conditions. Simple theoretical estimates show that in this way, provided that the proper experimental conditions are met, unit efficiency should be reachable in times much shorter than typical ones.

In this paper, we report on the design and the overall realization of micro-resonators based on the development of adequate processes on UV210 polymer. These micro-optical structures are developed by deep ultraviolet lithography allowing fabrication of nano-structured devices by mean of low cost and reproducible processes. Resonant microstructures of disk and stadium shapes with various sizes were investigated. Structural and optical characterizations have been carried out to ensure their ability as integrated resonant micro-structures. At first, scanning electron microscopy studies confirm the UV-light process resolution down to 450 nm developed on UV210 polymer. Then, optical characterizations have been performed as regards spectral properties of such micro-resonators. Field intensity measurements in visible and infrared range have been realized and validate the aptitude of the micro-structures to propagate and to allow an evanescent photonic coupling between waveguides and micro-resonators. Finally, spectral analyses on TE modes demonstrate the presence of optical resonances associated to whispering gallery modes for disk structures and chaotic modes for stadium shapes. The UV210 polymer appears appropriate for the realization of microstructures requiring a few hundred nanometers gap-scale while maintaining adequate spectral properties for versatile applications in telecommunication and metrology.

Non-linear absorption and athermal ablation effects are two of the most attractive benefits of ultrashort pulsed (USP) laser radiation for optics manufacturing. The conventional generation of complex shapes still is a challenging problem for engineers and constrains the outcome of new products and applications in combination with aspheric and freeform optical shapes. To create a process chain for these shapes based on USP is the definition of task. We accomplished experiments with a 18W lasersystem (<15ps) and analysed ablation strategies beginning from selective to three dimensional removal on different optical materials. Therefore dependent variables like roughness (RMS), irregularities (IRR) in terms of shape accuracy and sub-surface damages (SSD) give suggestions for parametrical improvements. The aim is to substitute grinding procedures by creating path-time-controlled removal functions to achieve polishable surface quality.