This PDF file contains the front matter associated with SPIE Proceedings Volume 7717, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We explain how to design a high Q, polarization independent, angularly tolerant filter, with a "doubly periodic" resonant grating etched in a high index material. Thanks to its broad angular acceptance, the fabricated component shows a Q factor of 5600 with a 580μm diameter Gaussian beam. Performing a detailed theoretical and experimental comparative study, we identify the parameters responsible for the degradation of the performances of the filter.

Here, we address the need for fast computation of subwavelength structures. It allows fast conception of optical devices. We present a modal method based on B-splines formulation which solves Maxwell equations. The two assets of this method are to use non uniform B-splines permitting to adapt the mesh to the structure, and to produce sparse matrices which permit to speed up the computation. As an illustration, we make use of this method for the design and analysis of variously shaped infrared optical devices.

We develop the Interpolatory Fixed-Point Algorithm (IFPA) to compute efficiently the TE and TM reflectance and transmittance coefficients for arbitrary 1D structures at oblique incidence. For this purpose, we demonstrate that the semi-analytical solutions of the Helmholtz equation provided by the fixed-point method have a polynomial dependence on variables that are related to the essential electromagnetic parameters -incidence angle and wavelength-, which allows a drastic simplification of the required calculations taking the advantage of interpolation for a few parameter values. The first step to develop the IFPA consists of stating the Helmholtz equation and boundary conditions for TE and TM plane incident waves on a 1D finite slab with an arbitrary permittivity profile surrounded by two homogeneous media. The Helmholtz equation and boundary conditions are then transformed into a second-order initial value problem which is written in terms of transfer matrices. By applying the fixed-point method, the coefficients of such transfer matrices are obtained as polynomials on several variables that can be characterized by a reduced set of interpolating parameters. We apply the IFPA to specific examples of 1D diffraction gratings, optical rugate filters and quasi-periodic structures, for which precise solutions for the TE and TM modes are efficiently obtained by computing less than 20 interpolating parameters.

In this work we present an analysis of non-slanted holographic reflection gratings by using a matrix method. A transfer matrix which relates the values of the electric field and its derivatives is obtained for a permittivity which varies cosenoidally for one period. The coefficients of this matrix can be calculated in terms of Mathieu's functions and their derivatives. Then the matrix of the entire medium is obtained as the Nth power of the matrix for one period. Since the reflectance and transmittance coefficients are related to the coefficients of the medium matrix, it is possible to calculate the efficiencies of orders -1 (reflected) and 0 (transmitted) by using this method. The results obtained by using the Trensference Matrix Method are compared to those obtained using Kogelnik's expressions for the transmission and diffraction efficiency. As will be seen there is good agreement between the results obtained by the Transference Matrix Method and those of the Coupled Wave Theory.

Using advanced mathematical techniques for optical computing and combining them with advanced optical engineering techniques and understanding of physical and chemical processes in plasmonic materials we developed novel boundary integral equation based numerical simulation tool. The performances of numerical simulation tool were investigated by means of extensive numerical studies of plasmonic nanostuctures including nanostructures with periodically and aperiodically spaced nanoparticles embedded in homogenenous medium, isolated homogeneous, layered and multilayered plasmonic nanoparticles. Selecting the most pormissing particle configurations, we applied the most efficient hierarchical method to reduce the complexity of calculation schemes for each particular nanostructure configuration.

The electromagnetic backscattered response of a metallic nanoparticle located close to a dielectric microsphere illuminated by a plane wave or a focused beam is theoretically investigated. It is demonstrated that the main contribution of the microsphere consists in increasing the excitation field. Furthermore, investigation of dipolar emission close to the microsphere shows a redirection of the radiated field in the backward direction.

We present a finite integration technique (FIT) simulator for modelling light diffraction from lithographic masks with complex shapes. This method has high flexibility in geometrical modelling and treating curved boundaries. The inherent feature of FIT allows more accurate electromagnetic field simulation in complex structures. This technique is also suited for fast EMF simulations and large 3D problems because of its parallelisation potential. We applied this method to investigate the effect of complex mask shapes on the printed image. We demonstrate results for a phase-shift mask (PSM) with footing extensions and surface roughness.

This paper documents the development of a laser beam homogenizer using a large, square fiber (channel integrator, kaleidoscope). The main effort addresses the beam injection issues for a three fiber system. The purpose of using three fibers is to split the input beam into three beams for use in an industrial laser process. It has been observed by the researchers in the laser beam shaping community, that strong patterns can be observed in the output irradiance of the output irradiance of optical fibers when the laser source is focused onto the entrance face of the fiber. This is due to the fact that although the mode volume of the fiber uniformly filled, the phase is not suitably randomized. This is analogous to the fact that summing a large number of Fourier series terms with uniform amplitude and phase will approximate a delta function. If the phases are randomized, the result will be a uniform speckle pattern. The Fourier components correspond to the modes of the fiber. Further, in the case of uniform phase input, the phase of the different modes will change as the light propagates down the fiber due to the difference in mode propagation velocities. But, the phase will not assume a random distribution if the fiber is not perturbed. This problem is frequently alleviated using mode scramblers, which usually employ bends or micro-perturbations of the fiber path. The problem can also exist if the mode volume of the fiber is not uniformly filled. This will happen if the source NA does not match the NA of the fiber. This paper will compare and contrast two methods of fiber injection; a traditional focused beam approach and a lenslet array beam integrator approach. Each design will be outlined and the performance results will be discussed to determine how well each method filled the modes of the square fiber.

Liquid crystal displays (LCDs) are widely used as spatial light modulators (SLMs) in many applications (optical signal processing, holographic data storage, diffractive optics...). In particular, as an alternative microoptics recording scheme we have explored the possibility to use a LCD to display the diffractive optical element (DOE) to be recorded onto a photosensitive phase material, so as to enhance the flexibility of the recording architecture. In this application the LCD acts as an amplitude dynamic transparency. By means of an optical system we image the function addressed to the LCD onto the recording material. The element to be recorded onto the phase material can be easily changed simply by changing the function addressed to the LCD. Among the recording materials, photopolymers provide very attractive capabilities. They present a great flexibility in their composition, the recording layer can be manufactured in a wide range of possible thicknesses, and they are inexpensive. These properties make it an interesting material to generate the phase DOEs. Both the composition and the thickness need to be optimized for the application to DOEs. In this work we explore the results dealing with the calibration of the recording setup and the photopolymer material. We also analyse the performance of phase-only diffractive lenses generated onto the photopolymer. Promising results have been obtained, where the focalization of the diffractive lenses generated has been demonstrated.

With enhanced performance of computing facilities the iterative design of phase diffractive optical elements (DOEs) has become widely accepted. A great number of up-to-date technologies for DOE fabrication make use of the approximation of the commonly continous DOE phase function by a picewise continuos (quantized) function. This is the reason why constructing iterative procedures for the design of quantized DOEs (DOEs with quiantized phase function) has become topical. Designing quantized DOEs with small number of quantization levels using Fienup-type iterative algorithms (or IFTA-algorithms) is hampered by the necessity to solve the diffractive theory inverse task at every iteration. Besides, using of such algorithms cannot guarantee convergence to global optimum. The use of stochastic procedures does not make it necessary to solve the inverse task. This paper deals with application of the known genetic stochastic procedure to determine the optimum of the function of many variables to designing quantized DOEs forming pre-given intensity distribution along an axial focal zone. Computer simulation results as well as experimental results are presented.

In this paper we describe new properties of the design landscape that could lead in the future to a new way to determine good starting points for subsequent local optimization. While in optimization the focus is usually only on local minima, here we show that points selected in the vicinity of other types of critical points (i.e. points where the merit function gradient vanishes) can be very useful starting points. We study here a problem that is simple enough to be analyzed in detail, the design landscape of triplets with variable curvatures. We show here how representatives of all triplet design shapes observed in global optimization runs can be obtained in a simple and systematic way by locally optimizing for each design shape one starting point obtained with the new method. Good approximations of these special starting points are also computed analytically with two theoretical models. We have found a one-to-one correspondence between the possible triplet design shapes and the critical points resulting from a model based on third-order spherical aberration within the framework of thin-lens theory. The same number and properties of critical points are predicted by a second model, which is even simpler and mathematically more general.

Optical designers can realize the required optical functions with a large variety of different designs. In order to obtain the needed functionality at the lowest possible cost, different design and assembly options will need to be taken into account. Additionally, the complexity of the decision situation is increased by the different production technologies which are available. The EC-sponsored project Production4μ is developing solutions that help optics designers to simplify and speed up this decision process. In this article, two different tools for calculating optics production costs are presented. The first one is a simplistic tool made for calculating the production costs of plastic optical parts. The second is a more complex tool that is able to do a detailed cost analysis for a complete process chain. This versatile tool can be used to calculate the costs associated to three main optical production methods: glass grinding, glass moulding and plastic injection moulding. Design For Manufacturability (DFM) issues are emphasized by drawing conclusions on which design characteristics have the largest influence on piece part cost. Practical applications of cost models are presented by relating optical design choices and expected performance to production cost with case studies.

The aim of this paper is to present the robust design approach in micro optics. Not only functional requirements have to be considered in robust design. All aspects of the manufacturing chain as well as operational and environmental effects have to be accounted for in the design phase already. Two fundamental issues characterise this approach: ensuring manufacturability and ensuring operability. The focus of this paper will be on the latter issue of ensuring the operability of the produced subsystem. The approach will be discussed using a micro optical test case as an example.

New ultra-thin optical designs are presented that comprise discontinuous optical sections (called channels) working in parallel (multichanneling) to provide the desired optical function. Aplanatic (a particular case of SMS-design) multichannel designs are also shown and used to explain more easily the design procedure. Typically, these multichannel devices are at least formed by three optical surfaces: one of them has discontinuities in the shape, a second one may have discontinuities in its derivative while the third one is smooth. The number of discontinuities is the same in the two first surfaces: Each channel is defined by the smooth surfaces in between the discontinuities, so that the surfaces forming each separate channel are all smooth. No diffractive effects are considered.

In contrast to the spatial (luminous) intensity distribution of high power light-emitting diodes (LEDs), little effort has been made to examine the spatial colour distribution of these light sources, i.e. the values of CIE colour coordinates as a function of direction in space. The spatial colour variation is negligible for single colour emitters, but this is not the case for bichromatic white LEDs using phosphor for wavelength conversion. As the latter diode types are most often used for high colour rendering applications, a quantitative description of their colour distribution is necessary. Therefore, photogoniometer measurements have been performed on a variety of white light-emitting diodes incorporating a planar (remote) phosphor. In this paper measurement results are used to discuss and model the spatial colour distribution of phosphor-white LEDs. Such LEDs appear to show an intrinsic and inevitable spatial colour variation. Furthermore, the measurement data and constructed model allow evaluating the visibility of spatial colour differences and the relevance of colour binning measurements at the end of LED package production lines. Using insights on spatial colour distribution gathered throughout this paper, a design proposal is made to vastly decrease the colour variation of phosphor-white LEDs.

The use of a ray file to model the optical characteristics of a light source is a well-known and popular method to achieve accurate results when simulating luminous intensity distributions of luminaires, especially if the source is interacting with optical components at a close distance. However, lighting industry becomes more and more interested in the spatial luminance distribution of the luminaire itself. Luminance maps offer a tool to predict the degree of discomfort glare early in the design process, especially when developing fixtures using small and intense LED light sources. The generation of luminance maps is commonly based on the reverse ray tracing technique, requiring one or more surfaces to be defined as light sources. However, ray files can not be considered as surface sources, but as a collection of ray data that model the near field of a light source. Despite the fact that ray files are constructed from experimental data they do not explicitly contain the geometry of the light source. This excludes the use of reverse ray tracing. For this reason the implementation of brute force forward ray tracing to obtain luminance maps was investigated. To be able to compare the results of both techniques an inhomogeneous surface source was defined. Luminance maps were then generated using both the brute force ray tracing approach and the conventional reverse ray tracing approach. A good agreement was obtained. A reduction in simulation time was achieved by parallel ray tracing computation and digital enhancement techniques.

Due to the energy crisis, the issue about how to improve the efficiency of lighting gains popularity. Many researches focus on using LED to be the light source of car lamps because LED has the advantages, such as low power consumption, adjustable luminous intensity, high color rendering index, long lifetime, and short reaction time, and the car lamps will become smaller and lighter. In our design, the LED headlamp consists three parts: a double ellipsoidal reflector, an aspherical lens, and a baffle. The double ellipsoidal reflector can improve the luminous flux in front of the headlamp and provide adequate illumination; the aspherical lens can eliminate spherical aberration; and the designed location of baffle can solve the glare problems. According to the optical simulation, the design successfully fits the request of intensity distribution in the ECE regulation.

We investigate the scattering behavior of nano-textured ZnO-Air and ZnO-Silicon interfaces for the application in thin film silicon solar cells. Contrary to the common approach, the numerical solution of the Maxwell's equations, we introduce a ray tracing approach based on geometric optics and the measured interface topography. The validity of this model is discussed by means of SNOM measurements and numerical solutions of the Maxwell's equations. We show, that the ray tracing model can qualitatively describe the formation of micro lenses, which are the dominant feature of the local scattering properties of the investigated interfaces. A quantitative analysis for the ZnO-Silicon interface at λ=488 nm shows that the ray tracing model corresponds well to the numerical solution of the Maxwell's equations. At λ=780 nm, a good agreement up to distance of approximately 1.5 μm from the topography minimum is achieved. The reduced effective wavelength in silicon leads to a better description of the ZnO-Silicon interface with respect to the ZnO-Air interface by the ray tracing model.

The application of digital holographic microscopy offers quantitative phase contrast imaging of reflective and (partially) transparent samples. Low coherent light sources enable an increased resolution in phase shifting digital holography by the reduction of stray light and multiple reflections in the experimental interferometer setup. Therefore light emitting diodes (LED) are utilized. Here, the effects on the reconstruction quality by considering the whole spectrum of the light source are investigated. Furthermore, the propagation of the complex wave fronts, which are determined by digital holography, and used for re- and multifocusing, is modified to light sources with a spectral width wider than that of typical laser light sources. Therefore, the propagation algorithm using the convolution method as a solution of the Fresnel-Kirchhoff diffraction integral according to the first Rayleigh-Sommerfeld approximation is extended by an additional integral to take into account the spectral width of low coherent light sources. Numerically, in the new approach the supplementary integral is realized by a discrete sum considering a finite set of wavelengths. Specifically, the results of the modified algorithm are compared with common algorithms with respect to resolution and image sharpness.

Holography is the process where two coherent wavefields interfere resulting in an interference pattern from which whole field information can be retrieved. Digital holography is the process where the intensity of the superposition of the two waves is recorded using a light sensitive opto-electronic detector array such as a CCD or CMOS camera. From this recorded hologram it is possible to numerically reconstruct the object wavefield. When an optical beam is focused on a pinhole whose diameter is of the order of a few times the wavelength of the illumination beam, a spherically divergent wavefield is emitted. We use the emitted optical beam to illuminate weakly scattering objects resulting in a geometrically magnified diffraction pattern at the camera face. Scattered light from the object is the called the object wavefield, while unscattered light acts as the reference wavefield. The hologram is captured digitally before numerical reconstruction is applied to yield whole field information about the object. It is possible to reconstruct the objects wavefield using this method from coherent laser or incoherent LED illumination. The emitted light from the pinhole acts a pointsource of spatially coherent light enabling holography. This, in combination with the use of multiple wavelength LED's multispectral amplitude images can be reconstructed. The multispectral lensless DIHM described here can be used to holographically image biological specimens such as cells grown for use in the biopharmaceutical industry or for research purposes. In analysing cell viability based on the trypan blue assay, the outer membrane of non-viable cells is penetrated by violet blue dye. Using such a Digital In-line Holographic Microscope as described here, automatic classification of viable and non-viable cells could be performed.

The performance of a holographic data storage system depends to a great extent on the quality and the physical properties of the recording medium. The storage capabilities of photopolymer materials are under constant study and for some applications a high spatial frequency material is necessary. In this work, we focus on the study of the influence of 4,4´-Azobis(4-cyanopentanoic acid) ACPA on holographic reflection gratings recorded in a polyvinyl alcohol/acrylamide-based photopolymer with the aim of recording reflection gratings with a spatial frequency of up to 5000 lines/mm. The experimental procedure used to examine the high spatial frequency response of this material is explained and the experimental results presented.

The influence of spatial limitation femtosecond laser pulse as both on generation efficiency of difference frequency radiation by an optical rectification in periodically-poled GaAs crystal, and on a space-time profile of generated radiation in near and far zones is investigated. The difference frequency radiation features generated by spatially-limited femtosecond laser pulse with Gaussian spatial profile of intensity and the amplitude front in periodically-poled GaAs crystal are considered. As a result of Fresnel transformation application, an expression for the frequency-angular spectrum and the spectral density of difference frequency radiation in the far field is obtained. It is shown that generating the difference frequency radiation via optical rectification of spatially-limited femtosecond laser pulse in cross-section distribution of difference frequency radiation near field a certain coordinate corresponds to the appropriate spectral component.

In photopolymers knowing the rate of diffusion of the monomer is of great interest in terms of modelling the evolution of recordings and predicting material behaviour. A wide range of values have been proposed using various indirect optical measurement techniques. A method involving the recording of very large period gratings, i.e. which diffract in the Raman-Nath regime, has been proposed, the results of which have been interpreted to suggest a diffusion rate of the order of 10^-8cm²/s. Using a similar acrylamide and polyvinylalcohol based material, the experiment involves monitoring the evolution of the zeroth order diffraction efficiency, the decay of which it is assumed is solely due to diffusion of the monomer. Repeating these experiments for different periods and for coverplated and uncoverplated layers, we offer a more complete analysis of the processes taking place indicating that not only is a volume holographic grating formed but also a surface relief profile. Evolution of both the holographic and the surface relief gratings will have an impact on the estimated rate of monomer diffusion. Results illustrating the variation are demonstrated and from these we show that the rate of diffusion of monomer to be closer to the order of ~10^-10 cm²/s.

In many modern applications, there are special requirements on the spectral properties of a laser beam. If a small spectral line width is desired, a spectral narrowing module can be placed inside the resonator to select only a small part of the spectral gain profile. This can be done for example with a compressing unit containing a prism train and a grating reflector in Littrow arrangement. To get a high selectivity, the grating is used in high order. From the point of view of a physical modeling of the laser resonator, the correct consideration of the diffraction effects in the asymmetrical Littrow part is complicated, since there are quite different path lengths across the beam cross section. Here a simple but elegant solution is presented to solve this problem with high precision. With the help of this approach, the complete resonator is modeled in the spatial and spectral domain. This allows a prediction of the spatial output beam profile, the divergence and the spectral distribution of the extracted radiation. It can be seen, that the spectral properties change over the cross section. This is an effect, which is also observed in practice. With this simulation tool, a performance prediction and an optimization of the resonator output radiation is possible.

We propose a measurement approach that allows the determination of aberrations of a microlens by analyzing the through-focus intensity image it produces when the object is a point source. To simulate image formation by a microlens we apply the extended version of the Nijboer-Zernike diffraction theory (ENZ) that uses the Debye diffraction integral to compute the image point-spread function. Due to the aperture size of the microlens and the finite dimensions of the pixels of the electronic detector the Debye diffraction integral should be adapted according to the Li-Wolf scaling rules to yield correct results. In addition to this we also discuss the experimental requirements posed by this characterization approach and derive from this a suitable experimental setup.

Both theoretical and experimental analysis of a new efficient method to measure the number and type of modes propagating in optical fibers are presented. This consists in measuring the intensity of the near field image at the end of a fiber while scanning the wavelength with a laser source signal. Modes are extracted from Fourier transformation of the spectral data at each point (x,y) of the images. A novel technique which is referred to as scalar product technique is implemented in order to reconfirm real modes and exclude spurious modes. The technique is based on the orthogonality of different modes. A standard multimode fiber has been measured to verify the technique. Three real modes LP₀₁, LP₁₁, and LP₀₂ are discovered and reconfirmed by the orthogonality with the minimum values of the scalar products. One spurious mode, which comes from the dependence of the power of the laser source on the wavelength, is thus excluded as it is not orthogonal either to the LP₁₁ mode or the LP₀₂ mode.

We analyze wave propagation, bandgap structure, resonances and Gaussian beam propagation in superlattices containing Negative Index Metamaterials. We focus to resonances within non-Bragg banndgaps emerging when average refractive index is zero. We analyze influence of absorption in NIMs on the resonances inside frequency regions predicted to belong to non-Bragg bandgaps of periodic and non-periodic structures. Further, we study resonances in finite, single defect and double defect structures where defects are introduced by structural parameter change. We compare different examples of spectral transmission resonances and field profiles under oblique incidence, for different polarizations and study influence of impendence matching and defect mode coupling. Finally, we consider examples of Gaussian beam propagation in these structures.

Many researches are conducted to improve Hopfield Neural Network (HNN) performance especially for speed and memory capacity in different approaches. However, there is still a significant scope of developing HNN using Optical Logic Gates. We propose here a new model of HNN based on all-optical XNOR logic gates for real time color image recognition. Firstly, we improved HNN toward optimum learning and converging operations. We considered each unipolar image as a set of small blocks of 3-pixels as vectors for HNN. This enables to save large number of images in the net with best reaching into global minima, and because there are only eight fixed states of weights so that only single iteration performed to construct a vector with stable state at minimum energy. HNN is useless in dealing with data not in bipolar representation. Therefore, HNN failed to work with color images. In RGB bands each represents different values of brightness, for d-bit RGB image it is simply consists of d-layers of unipolar. Each layer is as a single unipolar image for HNN. In addition, the weight matrices with stability of unity at the diagonal perform clear converging in comparison with no self-connecting architecture. Synchronously, each matrix-matrix multiplication operation would run optically in the second part, since we propose an array of all-optical XOR gates, which uses Mach-Zehnder Interferometer (MZI) for neurons setup and a controlling system to distribute timely signals with inverting to achieve XNOR function. The primary operation and simulation of the proposal HNN is demonstrated.

Photopolymer materials are practical materials for use as holographic recording media due to the fact that they are inexpensive, self-processing materials with the ability to record low loss, highly diffraction efficient volume holographic gratings. Extensive studies have been carried out on the behaviour of the various chemical components in such materials, with photosensitizers in particular receiving much attention, as they are an important component in initialising the photopolymerisation reaction. However in all such analyses dye diffusion is neglected. To further develop such materials, a deeper understanding of behaviours the photosensitizer present during the formation of holographic gratings in these materials has become ever more crucial. We report on experimental results and theoretical analysis of the diffusion rate of Erythrosine B, in a Polyvinylalcohol/Acrylamide layer.

The usage of Fresnel diffraction as an approximation of the Kirchhoff formula offers a large variety of advantages concerning diverse calculations for camera systems. However, Fresnel approximations cannot be applied to arbitrary camera systems. For configurations with wide aperture, e.g., the usage of Fresnel approximation is not possible without accepting an unagreeable deviation. It is important to check in advance if a camera system allows such an approximation for the needed calculations. Assuming that focal length f and ground distance g are given quantities, investigations of the real and complex integrands lead to a formula from which the minimal F-number f_# (respectively the maximum aperture radius r) is derived, so that Fresnel approximations can still be applied to a system. The analytical results are supported by numerical calculations and audited for three camera configurations outlined for remote sensing.

Virtual reality projection systems have been used formerly to study if mammals, including humans, are able to act in or understand virtual environments. Insects have been more difficult to study in such circumstances, one of the factors being their large, almost hemispherical field of view. Designing such a projection system that is capable of fulfilling the full field of vision of an insect is a challenging task. Normally, when designing a photographic objective, one of the goals is to minimize field curvature in order to provide sharp image through the whole sensor surface. However, because the image surface in this case is a sphere, flat field is not desirable and the design task becomes an opposite of a typical camera lens. Introducing field curvature becomes mandatory. We have designed and built a system with satisfactory image quality throughout the whole spherical surface with reasonable number of lenses as an add-on for common digital projectors. The manufactured system is able to project an image to a solid angle of 11.95 steradians, and when compared to the whole sphere which is represented with a solid angle of 4π steradians, approximately 5 % of the total sphere area is not illuminated.

This paper describes the development of an innovative scuba mask, which can be flooded by water and is able to provide a correct sight both underwater and in air, thus overcoming the drawbacks of traditional diving masks. The working principle of this new flooded device corresponds to the underwater telescope. Optical design analyses have demonstrated that it is able to provide a well corrected vision in both underwater and above-water conditions. The development of the optical configuration for the mask is illustrated presenting various stages of the optical project. The device has been optically and mechanically designed and then realized. Beyond the optical requirements, the optical design takes into account compactness, low fragility, diver comfort and other practical aspects in view of a possible mass production.

In recently, many research focus on the LED applications for environmental protection so a number of LED street lamps are presented. Although LED has many advantages for environmental protection, its special optical characteristics, such as intensity distribution, always limit the advantages in many applications. Therefore, we always need to do the secondary optical design for LED street lamp to replace the traditional optical designs that are designed for high-pressure sodium lamps and mercury lamps. According to the situation, we design an optical module of LED street lamp with LEDs and secondary optical design. First, the LEDs are placed on freeform reflector for the specific illuminated conditions. We design the optical module of street lamp with the two conditions that include the uniformity and the ratio of length to width in the illuminated area and without any light pollution. According to the simulation with the designed optical module, the uniformity in the illuminated area is about 0.6 that is better than the general condition, 0.3, and the ratio of length to width in the illuminated area is 3:1 in which the length is 30 meters and the width is 10 meters. Therefore, the design could let LED street lamp fits the two conditions, uniformity and ratio in the illuminated area.

In recently, many illuminance applications use LEDs to replace the traditional light source because they have many advantages, such as longer life time, lower power consumption, smaller size, and safer. Because the optical characteristics of LEDs and traditional sources are different, we need to do secondary optical design for LED applications, such as headlamp, street lamp, and MR16 lamp. For the better optical characteristic, the optical elements of the applications often include aspherical surface. However, it would generate higher cost and lower yield. In this paper, we design a TIR lens for MR16-Compatible LED Lamp without any aspherical surface. Base on the purpose of MR16, the design conditions are high directivity for higher illumination and flat top surface to simulate the traditional MR16. In this design, the TIR surface controls the edge intensity of LED and the central curve surface controls the center intensity of LED. According to the optical simulation, the view angle of the MR16-Compatible LED Lamp is ±9.3° and the central illumination is 559 Lux in which the total flux of LED is 83 lm. Finally, we manufacture and measurement the designed TIR lens. The view angle of the manufactured MR16 is about ±7.0° and the central illumination is 581 Lux in which the total flux is 52 lm.

A theoretical analysis of a new type of bandpass fiber filter is presented in this paper, which has the favorable transmission characteristics such as low loss, high optical rejection, flat top and steep edge etc.. These parameters are very important for the Wavelength Division Multiplexing (WDM) telecommunication systems. In our structure, a continuum spectrum is achieved thanks to a resonator cavity, formed by one mirror and a Linearly Chirped Fiber Bragg Grating (LCFBG). This grating is apodized along the fiber by a Super-Gaussian window function in order to make the output curves much smoother. Furthermore, the cavity length is calculated precisely by the continuum oscillation condition and this fiber filter is mathematically modeled and resolved by Transfer Matrix Method (TMM). The more efficient transmission of filter in our structure is observed when the reflector reflectivity at the both sides of the resonant cavity is symmetrical, in that case, the maximum output is 1. So, we could vary the coupling coefficient κ to control the maximum grating reflectivity for the purpose of making it be same as that of mirror's. Rather, there are other input parameters, for instance, the chirped value C, the length of grating L_B, and the mirror reflectivity R_M, which could influence the output results such as the grating reflectivity R_B, the transmission of filter T_F, the optical rejection of filter τop, and the bandwidth of filter Δλ_F. We have firstly plotted some schematics to find out the relations between the input and output parameters, and then with the restricted conditions about the input parameters, we have found finally the preferable input and output values for our structure. Besides, we observed that the bandwidth of filter could be also changed by apodization, in other words, the Super-Gaussian apodization plays an important role not only to smoothen the curves but to vary the width of bandpass as well.

Photopolymers are useful for different applications such as in the development of holographic memories or holographic optical elements. Photopolymers have an undesirable feature, the toxicity of their components and their low environmental compatibility, particularly if we analyse the life cycle of the devices made with these materials and their interaction with the environment. In this sense the University of Alicante has patented new dry biocompatible photopolymer: Biophotopol. Initially this new photopolymer was optimized to holographic memories application. The main goal of the previous works was to achieve thick stable layers. On the other hand polyvinyl/acrylamide (PVA/AA) photopolymers have been widely studied by many research teams. The main drawback of an AA-based photopolymer as far as the environment is concerned is the acrylamide, a substance which has been known to be carcinogenic for many years. Recent investigations have characterized PVA/AA based photopolymers at very low spatial frequencies. In previous works we have proposed the application of interferometric techniques, both in transmission and in reflection, to characterize in real-time the modulation performance of the photopolymers. We used this approach to characterize the optical modulation properties of a PVA/AA photopolymer. With this scheme we mainly characterize the properties at very low spatial frequencies, which can be useful to analyze the applicability of holographic recording materials in another range of applications, such as recording of diffractive optical elements (DOEs). In this work we have compared Biophotopol to PVA/AA photopolymers.

This paper presents an approximate method of the analysis of two-dimensional triangular lattice photonic crystal laser operation above the threshold. Described approach is based on the coupled wave equations and the energy theorem. It includes gain saturation and spatial hole burning effects and takes into account surface emission losses. An expression is derived for the small signal gain coefficient for transverse magnetic modes as a function of the output power, losses, coupling strength. For the given structure parameters, obtained laser characteristics reveal optimal coupling strength, which indicates maximal power efficiency of the laser structure.

The objective of our work is to present a tool for study of the light propagation in the new generation optical fibers that is the modal approach, this last is based on hypotheses that facilitate the calculation of the solutions of the dispersion equations and the coupling coefficients between different modes propagating in the fiber. This study allow us to characterize the propagation in several types of fibers: standards fibers, photonic crystal fibers, and fiber Gratting.

Luneburg's first order optical systems consist of sections of free space, lenses, and all possible combinations of these. The linear canonical transform (LCT), a parameterised linear integral transform, may be used to model the paraxial propagation of scalar optical fields through such systems. We consider the propagation of quasi-monochromatic, coherent wave fields, though more general calculations are possible. Numerical approximation of such systems is an active area of research, of interest for system design and analysis. We consider methods for the determination of the sampling requirements for the wave fields at the input and output of such calculations, in conjunction with the discretisation of the transform. We illustrate these considerations using phase space diagrams (PSDs), making use of the LCT's simple co-ordinate transforming effect on such diagrams. We discuss the implications of the cross-terms present in the Wigner distribution function, which are ignored in such PSD-based analyses, for the accuracy of the simulations and for the selection of sampling schemes. We examine the available algorithms for performing the transformations in O(N log N) time. In particular, we consider the relative merits of algorithms which decompose the optical system into special cases for which fast algorithms are better developed and also algorithms which decompose the calculations into smaller ones iteratively.

A novel EAM/PD monolithically-integrated optical logic element is presented. 5Gb/s optical logic AND gate operations at about -2 V for non-return-to-zero (NRZ) signals with8.4dB extinction ratio and16mW absorbed optical power was demonstrated.

The rapid progress in computer performance and widespread use of broadband networks has facilitated the transmission of huge quantities of digital information, thus increasing the need for high-speed, large-capacity storage devices and leading to studies on holographic data storage (HDS). Compared with laser disks where the recording density is limited by optical diffraction, HDS provides ultrahigh capacity with multiplex recording and high-speed transfer greater than 1 Gbps; it has excellent potential for optical memory systems of the future [1]. To develop HDS, a design theory for element technologies such as signal processing, recording materials and optical systems is required. Therefore, this study examines technology for simulating the recording and reproduction for HDS. In simulations thus far, the medium for the recording process has usually been approximated as laminated layers of holographic thin films. This method is suitable for systematic evaluation because the computational cost is low and it allows simulation in the true form of data, that is, in two-dimensional digital data patterns. However, it is difficult to accurately examine the influence of film thickness with a two-dimensional lamination simulation. Therefore, in this study, a technique for analyzing thick-film holograms is examined using the beam propagation method. The results of a two-dimensional simulation assuming laminated, holographic thin films and a three-dimensional simulation using the beam propagation method are compared for cases where the medium need not be treated as a thick film.

The paper presents a proposal of multiorder varifocal moiré zone plates, which change their focal length because of the lateral displacement of their two components with transmittances described by a cubic profile. The newly introduced element turns out to be an intermediate solution of the hitherto existing elements, which are the refractive Alvarez lens and its diffractive counterpart. Some of the expected properties of multiorder varifocal moiré zone plates are discussed, as well as reasons, because of which this newly introduced set of elements can be of interest in practical applications.

Green energy issues have been concerned by people in recent years; Lots of researches focus on natural light guiding system, health lighting system, especially on solar energy applications. Natural light guiding system is divided into three parts which are part of collection, part of transmission and part of lighting. In the future, natural light guiding systems can be expected to be used in large areas. Therefore, how to collect the convergence of systems efficiently of natural light is an important topic. In the traditional structure, the connection of natural light guiding system and transmission fiber coupler efficiency is less than 50%. We have put forward a Y branch structure to be used for increasing the efficiency of convergence, we have proposed Y-branch structure of the components, Polymethylmethacrylate (PMMA), is mainly to be used to connect the natural light guiding systems and plastic optical fiber which can be transmitted efficiently up to more than 80%.This article provides a low-cost and the best efficient transmission; this Y branch structure can be regarded as a new kind of convergence device.

The rapid growth of high-power light-emitting diode (LED) technologies has gained momentum in developing accurate tools and methods to measure performances of such products. For instance, it is widely recognized that confirming the photobiological safety is extremely important since the light of the high-power products may be shone directly into people's eyes. For many years, the international standard organizations, such as CIE, and researchers have been developing guidelines and/or improving methods for measuring the LED radiation patterns, respectively. However, the difficulties in LED measurements have been still highlighted by discrepancies in the experimental results among different laboratories. In this paper, we first propose a mathematical formulation for the existing approaches, such as those using two- and three-dimensional goniometers. Then, generalization of the measurement methods is presented to improve the system measurement accuracy, through making a connection between a predicted accuracy and the parameters of the optical setups (such as aperture size and working distance). To verify the effectiveness of our approach, the experiments are conducted to evaluate and compare the performances of the proposed approach. The measurement results indicate that our approach is consistent from theory to practice.

This paper extends the area of application of the Fourier modal method from periodic structures to aperiodic ones, in particular for plane-wave illumination at arbitrary angles. This is achieved by placing perfectly matched layers at the lateral sides of the computational domain and reformulating the governing equations in terms of a contrast field which does not contain the incoming field.

Despite the physical significance of the slanted holographic gratings, most materials research presented in literature involves the use of the unslanted recording geometry. A physically accurate electromagnetic model of the slanted holographic non-uniform gratings recorded in photopolymers is necessary in order to extract key material parameters. In this paper we present derivation of a model based on a set of two coupled differential equations, which include the effects of: (i) An exponential decay of refractive index modulation in the direction of the beam propagation due to the variation of absorption with depth; (ii) Gaussian profile of refractive index modulation due to recording by finite Gaussian beams profile, and (iii) A quadratic variation in the spatial period of the grating (i.e. chirp). The model is applied to fit experimental data, i.e. angular scans, of unslanted gratings recorded in Polyvinylalcohol/Acrylamide material for different slant angles in order to extract key volume grating parameters.

In the literature, several studies of the time varying photon absorption effects, which occur during the photo-initiation process in photopolymer materials, have been presented. Three primary mechanisms have been identified: (i) The photon absorption, (ii) the regeneration or recovery of the photosensitizer, and (iii) the photosensitizer bleaching. Based on the analysis of these mechanisms, the production of primary radicals can be physically described and modelled. In free radical photo-polymerization systems, the excited dye molecules induce the production of the primary radical, R^•, which is a key factor that in determining how much monomer is polymerized. This in turn is closely related to the refractive index modulation, Δn, formed during holographic recording. In this article, by modifying the composition of a Polyvinylalcohol/Acrylamide (PVA/AA) based photopolymer material, i.e., excluding any co-initiator, the photo-kinetic behaviour of the material is greatly simplified, an experimental study is performed, which makes possible development and verification of a new model capable of accurately predicting the time varying concentration of primary radicals.

Classical optical systems with variable optical characteristics are composed of several optical elements that can be moved with respect to each other. The mechanical change of position of individual elements (or group of elements) then enables to achieve desired optical properties of these optical systems e.g. the range of focal length or magnification. The disadvantage of such systems is that individual elements of these optical systems have to move very precisely along calculated trajectories, which results in high requirements on mechanical construction of such systems. Therefore it would be advantageous to be able to build optical systems without moving parts that would have the same (or similar) properties as above mentioned classical zoom systems. Nowadays, there exist several types of tunable lenses with a variable focal length based on different principles. This fact makes possible to perform the analysis of zoom optical systems based on variable power lenses. Our work deals with the analysis of possible designs of zoom optical systems using such lenses.

A wavelength selective add-drop multiplexer utilizing a directional coupler loaded with a first order Bragg grating can be realized both in fiber and planar technologies. Specifically for the planar case, we detail a systematic design procedure leading from general assumptions concerning the functional parameters of the device down to geometrical dimensions of the resulting planar microstructure. The functional parameters include: channel spectral width and channel isolation. The resulting dimensions are: waveguides etch depth, grating etch depth and lengths of apodized-grating trenches. Grating apodization profile of the form sin^n is assumed. Design curves are presented, enabling an optimal choice of the apodization profile's exponent n considering a tradeoff between the required channel isolation and the resulting grating length.

Establishing the rate of monomer diffusion in a polyvinylalcohol and acrylamide based photopolymer holographic material is of importance in terms of modelling the processes taking place during and postrecording and in working towards improving the materials response. Many methods have been used to estimate this value, resulting in a very wide range of suggested rates from 10^-7-10^-14 cm²/s. We examine the diffusion of polymer chains formed using short low intensity exposures, recorded in a modified material composition and then use these results to provide an estimate of monomer diffusion under low viscosity conditions i.e. minimal uncrosslinked polymerisation. Our modification of the material involves removing the crosslinking agent, the purpose of which is to increase polymer chain size and complexity and so make the recorded grating more stable. Removing it, the chains should be shorter and more linear - i.e. closer to the size of the monomer and so the rate of diffusion of the polymerised chains should approach the rate of diffusion of the monomer as the exposure and duration energy are smaller.