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Residual stress is one of the key factors that directly determines the optical quality of micro-optical devices. With the same residual stress, the larger the aperture is, the worse the optical quality is. Therefore, continuous micromirrors are more affected by residual stress than segmented micromirrors. However, due to the complexity of boundary conditions, the influence of residual stress in segmented micromirror arrays on the device performance has been widely investigated in theory and practical applications, but only a few research results about the influence of residual stress in the continuous micromirror arrays have been reported. In this work, the residual stress both in continuous and segmented micromirror arrays is analyzed and summarized, then an accurate model for continuous micromirrors is developed. Compared with the existing models, it combines two additional factors, layer plate and point supported boundary conditions. Based on the proposed model, the change of critical stress of continuous micromirrors induced by different thicknesses of residual stress compensated membrane is theoretically investigated. Finally, the compensating experiment has been carried out, and the results show that the optical quality of micromirror can be remarkably improved, almost two orders of magnitude, with the introduction of residual stress compensation.

We describe a tunable Fabry–Perot filter and grating hybrid modulator to achieve a higher spectral resolution compared with that produced by a single grating with the same period. In the hybrid modulator, a tunable Fabry–Perot filter is designed with a long cavity to accommodate a multi-order narrowband pre-filter. A grating is then utilized to separate these multi-orders spatially. Scanning the air gap of the tunable Fabry–Perot filter within 1/2 wavelength, the entire spectrogram can be achieved by compositing each group of transmitted multi-orders. Light passes first through the Fabry–Perot cavity and then into the grating. Thus, all of the light is incident on the Fabry–Perot cavity at a given angle, which can reduce the requirement for incident beam alignment and simplify the operation of the hybrid modulator. The structural matching conditions of the tunable Fabry–Perot filter and grating were presented based on the operating law of the hybrid modulator. In terms of the Rayleigh criterion, the practical spectral resolution of the hybrid modulator can be increased by at least twice that of the single grating. Experiments with a neon lamp revealed that the spectral resolution of the hybrid modulator was nearly double that of a single grating.

By investigating the transmittance and phase characteristics of the square holes on the metallic film, we find that the transmittance fluctuates with center distance between holes and appears resonant peaks, which attributes to the surface wave enhanced transmission phenomenon while the corresponding phase retardation through holes keeps constant. Based on this phenomenon, the slab lens can be optimized to a high transmittance by modulating the center distance of the holes. Design results show that the light intensity values at the focal spot of the slab lens can be enhanced from 3 to 14.5 in intensity scale when the center distance changes from 1.25 lambda to 0.95 lambda. (C) 2011 Elsevier Ltd. All rights reserved.

A structured lens with a large numerical aperture for high diffraction efficiency is proposed. This structured lens is formed by varying high-refractive-index-dielectric (HRID) square holes in a metallic film. Compared with previous structured lenses formed by varying air square holes, the modulated wavefront at the exit pupil of the structured lens is smoother and the diffraction efficiency is greatly improved. A dielectric film was introduced as a buffer layer to reduce the energy loss at the interface caused by the great impedance mismatching between air and the high refractive index dielectric. A lens with an aperture of 100 µm and a focal length of 50 µm was designed; its diffraction efficiency has been raised from 22.8% to 47.2% by the finite difference and time domain (FDTD) algorithm. This structured lens has the advantages of not only light weight and high compactness, but also large numerical aperture, high diffraction efficiency, and good imaging quality.

An integration method of grating array with different periods and Fabry-Perot (FP) resonator with an all-dielectric singlecavity is proposed. It is based on the capacity of spatial separation of spectral component by the grating and band-pass characteristics of filter to achieve the multi-pass band filtering. The filtering response can be tuned by changing the period of the grating rather than the cavity length of the filter. Theoretically, the relationship of the grating period and the peak wavelength is obtained by using the transfer matrix method (TMM). The device is analyzed by adopting the finite-difference time-domain (FDTD) method. The filter array can cover the wavelengths ranging from 850 nm to 950 nm with the full-width at half-maximum (FWHM) of 11–28 nm, and is suitable for the integration of the micro-filter array and the detectors.

We present a new design for the integration of a tunable Fabry-Perot (FP) filter and the grating etched on top of the cavity (IGFP) in the miniature spectrometer. It is based on the predispersion of the grating with the capacity of spatial separation of the spectral component and filter effect of the tunable FP filter. The free spectral range (FSR) of the IGFP is determined by the FSR of the grating, and its resolution depends on the filtering capacity of the FP filter. In the experiment, the high-resolution and wavelength scanning process of the IGFP were demonstrated with a narrowband and broadband light source, respectively. The results of the sub-nanometer resolution agree well with those from a commercial optical spectrum analyzer. Further, the IGFP provides an effective approach to solve the problem of the decrease of spectral resolution in the miniaturization process.

A graded photonic crystal formed by varying the high-refractive-index square dielectric rods is used as a structured lens to focus. This lens can realize high energy efficiency and large numerical aperture. Otherwise, the energy efficiency and the imaging quality can be greatly improved by adding a thin dielectric film on the two sides of the lens, and the energy efficiency increases as the fill factor increases. A lens with an aperture of 100µm and a focus length of 50µm is designed, the energy efficiency has achieved 48.5% in the case of fill factor as 44.7% by finite difference and time domain (FDTD) algorithm, and the spot size leads to the diffraction limit.

A multiple beams combiner based on three-dimensional (3D) isotropic near-zero index metamaterials (NZIM) is proposed. Built on the Snell's law, the combination of multiple beams can be readily realized via NZIM and further validated by numerical finite-element simulation. Our computational results show that the NZIM beam combiner has characteristics of an extremely small divergence angle of 0.08° and a high transmissivity of 88.12%. A low loss NZIM with refractive index of 0.04 is obtained by CST STUDIO SUITE at the wavelength of 775 nm via ‘fishnet’ structure. Our method opens up a new application of NZIM which could obtain high-power beam and may have potential applications in optical fiber communication, and metamaterials-based imaging system etc.

A method is brought forward for realizing polarization dependent devices by employing sub-wavelength asymmetrical hole array on a metallic film. Based on the fundamental mode approximation, the phase retardations of rectangular hole for two orthogonal polarization incident waves are analyzed and calculated. Using rectangular hole array, a bifocal-polarization lens for the infrared radiation with 10.6 mu m wavelength is designed. Its focal lengths for x- and y- polarized incident wave are examined by the finite difference time domain (FDTD) method and the Rayleigh-Sommerfeld diffraction integrals and the obtained results agree well with the designed values. (C) 2008 Optical Society of America

A method is proposed to modulate phase using variant square holes in a metallic film based on a fundamental mode approximation model. Phase retardation through square holes in a subwavelength scale in a thin metal film has been analyzed and calculated. Based on the model, a structured lens with a numerical aperture of 0.583 and a focal length of 240 microm formed by a 2D square hole array in a metallic film is designed. Numerical simulation using the finite-difference time-domain method is carried out, and the results agree with the theoretical analysis. A focal spot close to the diffraction limit can be obtained.

Phase modulation characteristics of subwavelength metallic square holes are investigated for 2D imaging purpose. Based on Maxwell equations, the transmission model of three-dime nsion subwavelength metallic holes is founded by a mode expansion technique. The relationship between the widths of the holes and the phase from - S to S is established when the thickness of metallic film is given. Then the influences of coupling electromagnetic (EM) fields as well as the incident angle on phase retardation are investig ated and calculated through varying the center distance between double holes. A slab lens is demonstrated by using hole-array formed on a metallic film, which verifies the theoretic analysis. Keywords: phase retardation; coupling electromagnetic fields; slab lens INTRODUCTION Since Ebbesen et al. found extraordinary optical transmission (EOT) through sub-wavelength holes array made in a metal film 1,2 , the study of the transmission properties of subwavelen gth aperture has become a very active research area. Subsequently, H.J.Lezec et al. reported that the micro-scaled metallic structures, a single aperture surrounded by a periodic corrugation in the metal surface, transmit light with a combination of low divergence, directionality and high efficiency

A beam shaping system (BSS) for improving the throughput of a dispersive spectrometer is presented by employing two anamorphic lenses and a prism array to segment the beam. The BSS was designed based on the inverse method of beam shaping for laser diode bars and the means of an optical slicer. In an experiment, a BSS was set up so that the incident light of a neon lamp with a circular spot from an input fiber was transformed into an elliptical spot coupled into a slit of a spectrometer without a change of divergence. Spectral measurement results demonstrate that the throughput of the dispersive spectrometer was doubled without loss of spectral resolution. The BSS can be combined with the existing dispersive spectrometer to improve the luminous flux and signal-to-noise ratio.

To collimate effectively the beam emitted from the stacked laser diode in which the lasing surfaces of the diode bars are not located in a plane, a new type of fast-axis collimator, refractive cylindrical microlens array with tunable focal lengths, is presented in this paper. Each lens of the array has the same diameter of 300μm but different focal lengths, ranged from 430μm to 540μm. By means of the mask moving lithography and replication technology, the microlens array was successfully fabricated. The measured fast-axis divergence of the stacked laser diode beam after the collimator was 25mrad, about half of the one (40mrad) for the microlens array with common focal lengths of 400μm.

A conclusion that a single conventional optical system could not realize fiber coupled high-power laser diode array is drawn based on the BPP of laser beam. According to the parameters of coupled fiber, a method to couple LDA beams into a single multi-mode fiber including beams collimating, shaping, focusing and coupling is present. The divergence angles after collimating are calculated and analyzed; the shape equation of the collimating micro-lenses array is deprived. The focusing lens is designed. A fiber coupled LDA result with the core diameter of 800 um and numeric aperture of 0.37 is gotten.

In order to form the proper aspherical microlens array profile with larger NA on photosensitive materials, a method is developed based on the characteristics of resist and processing parameters during development, for designing the exposure distribution, an experience formula has been proposed in the paper. Using the moving mask method, the exposure energy distribution function related to the photolithographic mask function can be determined by the experience formula. The profile control procedure is formed especially for the deeper relief profiles, after the binary mask data are slightly modified, the micro-structure with aspherical lens profile can be fabricated on the selected thicker resist, the micro relief profile error can be controlled in a certain range. The micro-profile is farther transferred to fused silica by ICP etching system. By our method, the fast microlens array elements with good fidelity and reasonable roughness have been fabricated and applied to the laser diode collimating system.

This paper presents basic designs and operation concepts of a novel micro-electro-mechanical-systems (MEMS) filter integrating a tunable Fabry-Perot (FP) cavity and a grating. It is based on the filtering effect of the tunable FP cavity and the spatial separation function of the grating for the different wavelengths. The combination of two devices could widen the spectral range of the traditional FP filter without affecting its spectral linewidth. A MEMS filter configuration based on the silicon-glass bonded structure has been designed. The FP cavity length depends on the thickness of the silicon wafer itself to realise the long cavity length. The T-S cantilevers could decrease the micromirror deformation, and reduce the driving voltage appropriately. Calculational results indicate that narrow linewidth and wide spectral range could be obtained simultaneously at the long cavity length.

A new method for microlens profile design was developed based on the analysis to the main parameters of microlens array, including micro profile formation, the numerical aperture ( NA ), the maximum sag depth for the refractive lens and the minimum zones width for the diffractive lens. With the relationships among the parameters, the microlens array in different profile can be determined effectively. The moving mask method[1] is used to realize the required profiles, an unique photolithography system have been built for implementing the mask moving exposure in both X and Y directions for the creation of microlens array. By modifying the binary moving mask, optimizing the photosensitive materials and the processing technique, the microlens profile error can be controlled in the range of 0.4µm~3µm depending on effective reliefdepth of the microlens. In our method, both diffractive and refractive microlens array with larger NA and higher fill factor can be fabricated for satisfying a plenty of purposes.

Performances of diffractive and refractive microlens array have been studied and compared. Besides the diffractive microlens array which can be fabricated by means of the microfabrication technologies, method for manufacturing continuous profile refractive microlens array with larger sag depth has been developed for solving the unique problems like diode laser alignment. Both diffractive and refractive microlens array with different numerical aperture and other parameters are fabricated according to the application requirements, experimental results are given.

In this paper, the process of fabrication of binary optical elements by thin film deposition has been introduced. An eight-level phase microlens array has been fabricated with 20 X 20 rectangularly shaped microlenses, focal length of 100 mm and lens size of 0.8 mm for the wavelength of 0.6328 μm. Our measurements show that all the step heights are nearly identical and the controlled precision of step heights was better than 1 nm.

Aerial images of a 0.35micrometers contact hole with the different phase shifting masks are calculated based on Hopkins model, and the optimal parameters of different phase shifters are gotten. Attenuated PSM in enhancing resolution and improving the depth of focus is of the most among them, especially when partial coherence factor is smaller. The calculated and simulated software is programmed. The software could produce all kinds masks automatically and calculate the aerial images at different illumination parameters, numeric aperture (NA), defocus conditions and add optimal phase shifter at these areas where resolution is smaller than the critical dimension (CD). At last, it could transform process old CIF format data file which is used to control E-beam exposure tool and filter it into two files by some sifting rule. The Att-PSMs is made and exposure experiments are carried out.

The structure, principle and manufacturing process of a single layer attenuated phase-shifting mask which is compatible with the traditional Cr mask fabrication technology are introduced in the paper. Partial experimental results are provided.

Attenuated phase shifting mask and that with optical proximity correction is adopted to improve resolution of photolithography based on some calculation results. The first factor k1 of the photolithography could be to 0.50, and the optimal transmission is about to 8 to approximately 10%. And a new kind of method of making attenuated phase shifting mask by encoding is put forward, and the theoretical calculation results are accordant to the conventional attenuated shifting mask.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper, the principle of two typical i-line ((lambda) equals 365 nm) and excimer laser ((lambda) equals 248 nm) uniform illumination optical systems based on Cohler illumination is reviewed, the principle and method of the calculation and simulation of intensity distribution of the illumination system for sub-micron photolithography consisting of aspherical surfaces, non-co-axial surfaces and lens array are put forward, that is ray-tracing based on the Snell theorem and spot diagram. At the same time, a program CALOSD made by us is described, two typical results of calculation and simulation of intensity distribution of illumination optical systems are given.

In this paper, a novel color -encoder which has dual functions of a beainsplitter and a beamshaper is proposed.This encoder could acquire very good uniformity of light field with high diffractive efficiency.An algorithm which combining tracing algorithm, G-S algorithm and Y-G algorithm is used to design this encoder,the result by computersimulation caculation shows:the diffraction efficiency is up to 93.3%,non-uniformity is less than O.O1%.And a newapproach to encode and make a phase element by using color-printer techniqies is proposed in this paper as well.keywords: color-encoder,binary optics,iterative algorithm 1.INTRODUCTION 2D/3D rainbow holograms have been used widely with speedy development of embossed holograms. In recording arainbow hologram, the slit is a very important element. Color-encoding different parts of an object in recording arainbow hologram, we generally use several slits as encoders, but that would lead to great energy loss.When lowsensitivity photoresist holograms are recordered by He-Cd laser that has low power, we have to prolong exposure time,that requires high stability for system.If we use a cylindrical lens as the the substitute for a slit, the efficiency of lightenergy can be improved,but only one cylindrical lens without other additional elements can not make several slits imageat the same time.We record a hologram of slits and make the reconstructive real image ofthe hologram as the substitutefor real slits,but the hologram could lead to low diffractive efficiency and the coherent noises'.Binary-Optics is a new branch of optics, it allows us to design wavefront using computer,the method is so flexiblethat we can convert any wavefront into any other desired one.In this paper,we proposed a novel color-encoder which hasdual fimctions of a beamshaper and a beamsplitter.It can convert a input circle Gaussian laser beam into three coherentuniform beams,enlarge the using areas of light field.This encoder could acquire a very good uniformity of light fieldwith high diffractive efficiency.

An off-axis type refractive/diffractive Gregorian telescopic optical system without any aspherical element and center obscuration is presented in this paper. A binary optical element is used to correct aberrations and its size is reduced to 1/3 or 1/4 of the Schmidt corrector. Using OSLO SIX4.2 (Sinclair Optics Inc.) optical design software, an off-axis infrared refractive/diffractive hybrid telescopic system is designed with the parameters: aperture (phi) equals 120 mm, effective focal length f equals -1000 mm, wavelength (lambda) equals 4.3 micrometers , the field of view 2 degree(s) X 6 degree(s), resolution Res equals 50 um, modulation transfer function >= 0.4 when the spatial frequency v

Deep etched diffractive optical elements could acquire some significant properties, for example, deep etched Fresnel lens could be used as fast lens, deep etched blazed grating has high dispersive index. So it is a new subject of binary optics. In this paper, a new kind of element, deep etched multi-phase level fractional Talbot grating is presented. Compared with common fractional Talbot grating, it has the property of high fill factor.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

To resolve the variability of the intensity distribution and the divergence of the laser diode (LD) output beam in a beam shaping system, a diffractive optical element (DOE) array is proposed in LD beam shaping. This DOE array can divide the wavefront of input beam. All light diffracted by all DOE array units is super-positioned on the output plane, and the tolerance for the input beam is improved by this means. Using the above DOE array laser shaped method, three rectangles intensity distribution are realized from Gaussian beam with the diffraction efficiency of 90.5% and the uniformity of 96%. When the half divergence angle of the LD varies from 2o to 16o in slow and fast axis directions, respectively, the diffraction efficiency maintains to be approximate 90% and its uniformity is more than 95%. When the defocus of the lens to collimate LD beam varies from -32 to 32 \mu m, numerical experiments indicate that uniformity and the diffraction efficiency of the shaped beam by the DOE array do not vary.

Double telecentric configuration of an optical projection lens with alignment through lens wafer-to-reticle and uniform illumination pinciple of optical system for micro­lithography are discribed in the paper. To meet requirement of optical transfer function (OTF) for i-line lithography, the relation between photolithographic resolution (R) and numerical aperture (NA) is discussed. As an example, we have designed a new double telecentric projection lens with NA=0.42, magnification M=-l/5, image field size 15mmx15mm (21.2mm diametre) and conjugate distance 602mm. Optical design program ZEMAX-XE is used to calculate image qualities of the i-line lens. The calculating results indicate wavefront aberrations < λ/4 and MTF >0.55 across the entire field when spatial frequency is 715 c/mn and wavelength is 365+/-3mn. This means the photolithographic resolution of 0.7um could be realized. The illumination uniformizer called the integrator consists of an array of 81 small square lens elements. The illumination non-uniformity of+/-2% could be realized by using our simulation program OPTENG to calculate light intensity distribution on tire illuminated image plane.

In this paper, a design method for a multiwavelength photon sieve is described based on a random-area-divided approach, where the whole aperture of a multiwavelength imaging photon sieve is divided into multiple discrete spaces corresponding to the number of the selected working wavelengths. The micropinhole distribution in each discrete space can be calculated for the defined wavelength with one fixed focal length in terms of the normal design for photon sieve. A three-wavelength photon sieve was designed and fabricated in the lab, and its imaging properties are analyzed in the experimental optical system with satisfactory results.

The characteristics of the phase retardations and the invariability against the incident angles are investigated when light enters the rectangular holes with different sizes perforated on metallic film. A kind of metallic structure with a great potential in imaging is brought forward. The finite difference time domain (FDTD) method and the Rayleigh-Sommerfeld diffraction integrals are used to testify the imaging ability at different incident angles by examining the electric field on focal plane. The calculation results indicate that a quite large view of field lens can be achieved by increasing the number of the holes per unit area with the mentioned structure. A metallic structured lens with a 280 microm aperture and 240 microm focal length is designed and the view angle range of +/-15 degrees can be achieved.

Dead spaces are generated in the fast-axis direction of the laser diode stack LDS because of the construction of the LDS. A new method of using a plane-parallel plate array to eliminate dead spaces between the bars of the LDS is presented. The design method of the plane-parallel plate is also investigated, and the beam parameter prod- uct is used to evaluate the quality of the beams. As an example, the plane-parallel plate array for an LDS consisting of four bars is designed and simulated. The simulation results show that the dead spaces are eliminated, the spots size is compressed from 6.5 mm10 mm to 3.5 mm10mm, and the energy loss is about 2%. © 2007 Society of Photo

A beam-shaping technique is presented for asymmetrical laser beams with different beam waists and divergences in both vertical and horizontal directions. We utilize a pair of two-dimensional micrograting arrays to equalize the beam parameter products of an asymmetrical beam in orthogonal directions by deflecting the appointed parts of the beam on the longer side of the beam and by recombining the parts on the shorter side. When combined with divergent transformation by means of collimating optical components, the beam-shaping system can produce a symmetrical beam in orthogonal directions with optimized beam waists and divergences. A beam-equalization system is designed and demonstrated for a typical asymmetrical beam of a laser diode bar. In the experiment an emission beam with dimensions of 1 microm x 10 mm and half-divergences of 148 mrad x 576 mrad in the far field is transformed into an almost-square distribution with dimensions of -12 mm x 12 mm and half-divergences of -2 mrad x 2 mrad, which confirm the effectiveness of the proposed technique.

An innovative beam-shaping method for laser diode stacking is presented by employing a pair of reflective two-wedge-angle prism arrays. Each subprism with two variable wedge angles is designed for deflecting the partial emission from different bars to the dead spaces of the stack, according to the configuration of the real laser diode (LD) stack and the requirement of the system. The formula to determine the parameters of each subprism is deduced by way of geometrical analysis. A beam-shaping system for stack laser diodes with three bars is designed and simulated, and the results show that the stack laser beam is well transformed into a required distribution efficiently. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

A profile formation and control approach has been developed for manufacturing micro-optical elements with continuous profile and deep relief depth. Based on Dill's exposure model, an effective expression for determining the exposure dose function is established by using a supposition of equivalent exposure threshold inside a resist layer. An analytical simplified formula is further deduced by taking absorbance as constant B, and the approximate condition is discussed. For evaluating the simplified formula, the profile error was calculated and analyzed by simulation. With the exposure dose function, the binary mask for manipulating the light distribution by means of a moving-mask lithographic method can be designed. Experimental results are given and show the comparative performance to the required profile and relief depth. A series of refractive microlens arrays with aspherical profiles, a wide range of numerical apertures (0.005 to 0.6), and high fill factors were accomplished in the lab and may be applied to many systems. (C) 2004 society of Photo-Optical Instrumentation Engineers.

Sichuan UniversityInformation Optics InstituteChengdu 610064, ChinaE-mail: pengqinjun@263.netChongxi ZhouChinese Academy of SciencesState Key Laboratory of Optical Technologyon MicrofabricationChengdu 610209, ChinaZheng CuiRutherford Appleton LaboratoryChilton, DidcotOxon OX11 0QXUnited KingdomAbstract. A new photolithographic technique that combines the advan-tages of a programmable digital liquid crystal display (LCD) system andprojection photolithography system to fabricate arbitrarily shaped micro-structures using LCD panels as real-time masks is reported. Its principleand design method are explained. Based on a partial coherent imagingtheory, the process to fabricate microaxicon arrays and zigzag gratings issimulated. The experiment has been set up using a color LCD as areal-time mask. Microaxicon arrays and zigzag gratings have been fab-ricated by a real-time photolithographic technique. The 3-D surface reliefstructures are made on panchromatic silver-halide sensitized gelatin(Kodak-131) with trypsinase etching. The pitch size of the zigzag gratingis 46.26 mm, and the etching depth is 0.802 mm. The caliber of theaxicon is 118.7 mm, and the etching depth is 1.332 mm.

Discrete formulas to calculate aerial imaging on the wafer for photolithography are presented, and physical fundamental of inverse Fourier transform convolution filtering to improving resolution is discussed. The larger contrast for dense L/S group with the pitch of 0.27 mum is obtained with an ArF 193 nm stepper with a numerical aperture of 0.60 and partial coherent coefficients of 0.3. (C) 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)02010-9].