This PDF file contains the front matter associated with SPIE Proceedings Volume 8429, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Classical spherical gradient index (GRIN) lenses (such as Maxwell Fish Eye lens, Eaton lens, Luneburg lens, etc.) design procedure using the Abel integral equation is reviewed and reorganized. Each lens is fully defined by a function called the angle of flight which describes the ray deflection through the lens. The radial refractive index distribution is obtained by applying a linear integral transformation to the angle of flight. The interest of this formulation is in the linearity of the integral transformation which allows us to derive new solutions from linear combinations of known lenses. Beside the review of the classical GRIN designs, we present a numerical method for GRIN lenses defined by the Abel integral equation with fixed limits, which is an ill-posed problem.

Expanding demands on manufacturing technology increase the requirements on necessary non-contact metrology. Several optical metrology systems are based on separated imaging (e.g. camera unit) and image generating units (e.g. projection unit). This fact limits the geometrical miniaturization of the system. We present a compact, highly integrated 3-D metrology system based on the fringe projection principle using a bi-directional OLED microdisplay. The microdisplay combines light emitting pixels based on OLED technology (projection unit) and light detecting pixels based on photo diode technology (camera unit) on one single device, realized by the OLED-on-CMOS-technology. This technology provides the opportunity for a further miniaturization of optical metrology systems. The 3-D metrology system is based on fringe projection onto the surface of the measurement object. The fringes will appear deformed when observed from a dierent angle (triangulation angle). From the deformation of the fringes the 3-D coordinates of all visible points can be calculated and thus the object shape can be determined. For the application of an 3-D Sensor and due an internal display eect, separate lenses for projection and imaging are necessary. The system principle and several optical system congurations are discussed. Due to the application of the bi-directional OLED microdisplay the fringe generating elements and the detectors will be combined into one single device. Based on this integrated device an ultra-compact and solid system concept for 3-D surface metrology is practicable.

PURPOSE: To present a commercially available optical modeling software tool to assist the development of optical instrumentation and systems that utilize and/or integrate with the human eye. METHODS: A commercially available flexible eye modeling system is presented, the Advanced Human Eye Model (AHEM). AHEM is a module that the engineer can use to perform rapid development and test scenarios on systems that integrate with the eye. Methods include merging modeled systems initially developed outside of AHEM and performing a series of wizard-type operations that relieve the user from requiring an optometric or ophthalmic background to produce a complete eye inclusive system. Scenarios consist of retinal imaging of targets and sources through integrated systems. Uses include, but are not limited to, optimization, telescopes, microscopes, spectacles, contact and intraocular lenses, ocular aberrations, cataract simulation and scattering, and twin eye model (binocular) systems. RESULTS: Metrics, graphical data, and exportable CAD geometry are generated from the various modeling scenarios.

Progressive miniaturization and mass market orientation denote a challenge to the design of dynamic optical systems such as zoom-lenses. Two working principles can be identified: mechanical actuation and application of active optical components. Mechanical actuation changes the focal length of a zoom-lens system by varying the axial positions of optical elements. These systems are limited in speed and often require complex coupled movements. However, well established optical design approaches can be applied. In contrast, active optical components change their optical properties by varying their physical structure by means of applying external electric signals. An example are liquidlenses which vary their curvatures to change the refractive power. Zoom-lenses benefit from active optical components in two ways: first, no moveable structures are required and second, fast response characteristics can be realized. The precommercial development of zoom-lenses demands simplified and cost-effective system designs. However the number of efficient optical designs for electro-optically actuated zoom-lenses is limited. In this paper, the systematic development of an electro-optically actuated zoom-lens will be discussed. The application of aberration polynomials enables a better comprehension of the primary monochromatic aberrations at the lens elements during a change in magnification. This enables an enhanced synthesis of the system behavior and leads to a simplified zoom-lens design with no moving elements. The change of focal length is achieved only by varying curvatures of targeted integrated electro-optically actuated lenses.

In this paper an expression is derived to determine influence functions for optical imaging systems. The influence function describes the wavefront change, caused by a deviation of an optical surface from its nominal shape due to any arbitrary reason. The method is derived with the help of the paraxial approximation, using the optical design prescription from software such as Code V or Zemax. The presented method can be used for diffraction limited projection systems. It helps with modelling wave front aberrations caused by desired and undesired deviations of the optical surface from its nominal shape. So it can be used for modelling mirror vibrations, thermal aberrations, the influence of manufacturing errors or Adaptive Optical systems without using optical ray-tracing programs.

In this work, a new two-dimensional analytic optics design method is presented that enables the coupling of three ray sets with two lens profiles. This method is particularly promising for optical systems designed for wide field of view and with clearly separated optical surfaces. However, this coupling can only be achieved if different ray sets will use different portions of the second lens profile. Based on a very basic example of a single thick lens, the Simultaneous Multiple Surfaces design method in two dimensions (SMS2D) will help to provide a better understanding of the practical implications on the design process by an increased lens thickness and a wider field of view. Fermat's principle is used to deduce a set of functional differential equations fully describing the entire optical system. The transformation of these functional differential equations into an algebraic linear system of equations allows the successive calculation of the Taylor series coefficients up to an arbitrary order. The evaluation of the solution space reveals the wide range of possible lens configurations covered by this analytic design method. Ray tracing analysis for calculated 20th order Taylor polynomials demonstrate excellent performance and the versatility of this new analytical optics design concept.

3D imaging systems are currently being developed using liquid lens technology for use in medical devices as well as in consumer electronics. Liquid lenses operate on the principle of electrowetting to control the curvature of a buried surface, allowing for a voltage-controlled change in focal length. Imaging systems which utilize a liquid lens allow extraction of depth information from the object field through a controlled introduction of defocus into the system. The design of such a system must be carefully considered in order to simultaneously deliver good image quality and meet the depth of field requirements for image processing. In this work a corrective model has been designed for use with the Varioptic Arctic 316 liquid lens. The design is able to be optimized for depth of field while minimizing aberrations for a 3D imaging application. The modeled performance is compared to the measured performance of the corrected system over a large range of focal lengths.

This paper presents the design of a multi-channel imaging system which has a different angular resolution and field of view in the different channels. Our aim was to design a multi-resolution imaging system that can be fabricated at wafer scale to obtain a compact and low cost imaging device. This imaging system is able to resolve fine details of a small region of interest and control the surrounding region at the same time. An interesting aspect of such a multi-channel, multi-resolution imaging system is that it allows to implement different image processing algorithms at different segments of the image sensor for several imaging functionalities. We have designed an imaging system that has three optical channels where each optical channel consists of four aspheric lens surfaces. The design was analyzed and optimized with CODE V optical design software. The three optical channels share one image sensor which has 1440×960 pixels and a pixel size of 10μm. The first optical channel has the highest angular resolution (0.0096°) and smallest field-of- view (2×3.5°).The third optical channel has the highest field of view (2×40°) and lowest angular resolution (0.078°). The second optical channel has intermediate imaging properties between the first and the third optical channels; however, it has the same image sensor segment size as the first channel. All the three optical channels have diffraction limited performance ensuring good overall image quality.

Ambilight is a unique Philips feature, where RGB LEDs are used to create a dynamic light halo around the television. This extends the screen and hence increases the viewing experience, as it draws the viewer more into the action on the screen. The feature receives very positive consumer feedback. However, implementing Ambilight in the increasingly stringent design boundary conditions of a slim and thin TV set is a challenging task. Optical simulations play a vital role in each step of the Ambilight development. Ranging from prototype to final product, we use simulations, next to prototyping, to aid the choice of LEDs, optical materials and optical systems during different phases of the design process. Each step the impact of the optical system on the mechanical design and TV set dimensions needs to be taken into account. Moreover, optical simulations are essential to guarantee the required optical performance given a big spread in LED performance, mechanical tolerances and material properties. Next to performance, optical efficiency is also an important parameter to evaluate an optical design, as it establishes the required number of LEDs and the total LED power. As such optical efficiency defines the thermal power which needs to be dissipated by the LED system. The innovation roadmap does not stop here. For future systems we see a miniaturization trend, where smaller LED packages and smaller dies are used. This evolution makes the impact of mechanical tolerances on the optical design more severe. Consequentially, this approach poses a whole new challenge to the way we use optical simulations in our design process.

For imaging design aberration theory provides solid ground for the layout and development of optical systems. Together with general design rules it will guide the optical engineer towards a valid starting point for his system. Illumination design is quite different: Often first system layouts are based on experience, rather than on a systematic approach. In addition radiometric nomenclature and definitions can be quite confusing, due to the variety of radiant performance definitions. Also at a later stage in the design, the performance evaluation usually requires extensive statistical raytracing, in order to confirm the specified energetic quantities. In general it would therefore be helpful for illumination designers, especially beginners, to have an engineering tool, which allows a fast, systematic and illustrative access to illumination design problems. We show that phase space methods can provide such a tool and moreover allow a consistent approach to radiometry. Simple illustrative methods can be used to layout and understand even complex illumination components like integrator rods and optical arrays.

LEDs have many advantages over traditional lighting, such as high brightness, small size, broad range of wavelengths being emitted and ability to be placed with high density over flat or even-shaped surface. This offers promising choice for many industrial and consumer applications and especially important for machine vision applications, where bright and homogeneous illumination offers better visibility of features of interest. This can be obtained both with multicomponent source configuration and analysis of distribution of optical energy density and color on an illuminated surface. Required illuminating properties are produced by multicomponent source with certain structure and power configuration. In this paper it is shown how to obtain required color and energy distribution on the surface of interest by varying parameters of multicomponent source (matrix dimension, the distance between elements in the matrix, the distance between the source and illuminated surface, etc.). Superposition of individual elements spectra is also taken into account. This paper has proposed technique of the RGB multicomponent source simulation, which provides homogeneous illumination on a flat surface of interest both in optical energy density and color. The ripple of luminance on the surface shouldn't exceed the value of 2%.

Thermo-optical simulation is a compulsory improvement of classical ray tracing, since many branches of optical and laser technology have to deal with thermal gradients. This paper discusses an approach for coupling FEM and ray tracing simulation tools by processing FE data using scattered data approximation techniques. The implemented interface for two space dimensions is being validated by comparing approximated data to measured values from a CO2 laser application of up to 1.75 kW. Finally, the benefits and further developments of analyzing thermal gradients in optical simulation are being discussed.

Leonhardt demonstrated (2009) that the 2D Maxwell Fish Eye lens (MFE) can focus perfectly 2D Helmholtz waves of arbitrary frequency, i.e., it can transport perfectly an outward (monopole) 2D Helmholtz wave field, generated by a point source, towards a "perfect point drain" located at the corresponding image point. Moreover, a prototype with λ/5 super-resolution (SR) property for one microwave frequency has been manufactured and tested (Ma et al, 2010). Although this prototype has been loaded with an impedance different from the "perfect point drain", it has shown super-resolution property. However, neither software simulations nor experimental measurements for a broad band of frequencies have yet been reported. Here we present steady state simulations for two cases, using perfect drain as suggested by Leonhardt and without perfect drain as in the prototype. All the simulations have been done using a device equivalent to the MFE, called the Spherical Geodesic Waveguide (SGW). The results show the super-resolution up to λ/3000, for the system loaded with the perfect drain, and up to λ /500 for a not perfect load. In both cases super-resolution only happens for discrete number of frequencies. Out of these frequencies, the SGW does not show super-resolution in the analysis carried out.

We present numerical simulations, based on elementary mode method, of field emitted by broad-area laser diodes. The near field is expressed as a superposition of modes with sinusoidal spatial amplitude inside the laser resonator and zero outside. The assumed functional form of the modes is used to find the intensity distribution in the far-zone. This information is then used to construct the elementary-mode decomposition in the near-field. The validity of the elementary-mode approach was verified by comparing the intensity and the degree of coherence at various distances from the source.

The propagation of harmonic fields through homogeneous media is an essential simulation technique in optical modeling and design by field tracing, which combines geometrical and physical optics. For paraxial fields the combination of Fresnel integral and the Spectrum of Plane Waves (SPW) integral solves the problem. For non- paraxial fields the Fresnel integral cannot be applied and SPW often suffers from a too high numerical effort. In some situations the far field integral can be used instead, but a general solution of the problem is not known. It is useful to distinguish between two basic cases of non-paraxial fields: 1) The field can be sampled without problems in the space domain but it is very divergent because of small features. A Gaussian beam with large divergence is an example. 2) The field possesses a smooth but strong phase function, which does not allow its sampling in space domain. Spherical or cylindrical waves with small radius of curvature are examples. We refer to such fields as fields with a smooth phase term. The complete phase is the sum of the smooth phase term and the residual. For both cases we present a parabasal field decomposition, in order to propagate the field. In the first case we perform the decomposition in the Fourier domain and in the second case in the space domain. For each of the resulting parabasal fields we separate a linear phase factor which has not to be sampled. In order to propagate the parabasal fields we present a rigorous semi-analytical SPW operator for parabasal fields, which can handle the linear phase factors without sampling it at any time. We show that the combination of the decomposition and this modified SPW operator enables an ecient propagation of non-paraxial fields. All simulations were done with the optics software VirtualLab™.

The propagation of harmonic fields between non-parallel planes is a challenging task in optical modeling. Many well-known methods are restricted to parallel planes. However, in various situations a tilt of the field is demanded, for instance in case of folded setups with mirrors and tolerancing with tilted components. We propose a rigorous method to calculate vectorial harmonic fields on tilted planes. The theory applies a non-equidistant sampling in the k-space of the field before rotation in order to obtain an equidistant sampling of the rotated field. That drastically simplifies the interpolation challenge of the tilt operation. The method also benefits from an analytical processing of linear phase factors in combination with parabasal field decomposition. That allows a numerically efficient rotation of any type of harmonic fields. We apply this technique to the rigorous propagation of general harmonic fields through plane interfaces. This propagation can be based on a plane wave decomposition of the field. If the field is known on the interface a fast algorithm results from the decomposition. However in general, the field is not known on the interface. Then a rotation operator must be applied first. All simulations were done with the optics software VirtualLab™.

This article deals with an optical model which describes silicon thin film solar cells with rough interfaces in a fast and easy way. In order to simulate thin layer stacks with rough interfaces diffuse scattering as well as interference effects have to be taken into account. Algorithms like the Finite-Difference Time-Domain method (FDTD) solve the Maxwell Equations and therefore fulfil these demands. Yet they take up a considerable amount of simulation time and computation capacity. To overcome these drawbacks an optical model was developed which combines the Transfer- Matrix-Method (TMM) and the Raytracer algorithm. The fraction of TMM and Raytracer in the model is determined by a separating function which can be interpreted as the integral haze. In order to verify the combined optical model a series of amorphous silicon single cells with varying intrinsic layer thicknesses was produced on two different kinds of textured substrates. The results of the combined optical model are compared to measured data as well as to the simulation results of the FDTD method. It can be shown that the combined optical model yields good results at low simulation time.

The development of photonic devices with tailor-made optical properties requires the control and the manipulation of light propagation within structures of different length scales, ranging from sub-wavelength to macroscopic dimensions. However, optical simulation at different length scales necessitates the combination of different simulation methods, which have to account properly for various effects such as polarization, interference, or diffraction: At dimensions much larger than the wavelength of light common ray-tracing (RT) techniques are conveniently employed, while in the subwavelength regime more sophisticated approaches, like the so-called finite-difference time-domain (FDTD) technique, are needed. Describing light propagation both in the sub-wavelength regime as well as at macroscopic length scales can only be achieved by bridging between these two approaches. In this contribution we present on the one hand a study aiming at the determination of the intermediate size range for which both simulation methods are applicable and on the other hand an approach for combining classical ray-tracing with FDTD simulation in order to handle optical elements of large sizes. Generally, the interface between RT and FDTD is restricted to very small sample areas. Nevertheless, many real world optical devices use e.g. diffractive optical elements (DOEs) having comparably large areas in the order of 1-2 mm² (or larger). Therefore, one has to develop strategies in order to handle the data transfer between FDTD and RT also for structures of such larger size scales. Our approach in this regard is based on the symmetries of the structures. In this way support programs like e.g. MATLAB can be used to replicate the near-field of a single structure and to merge it to the near-field of a larger area. Comparisons of RT and FDTD simulations in the far-field can be used to validate the physical correctness of this approach. With such procedure it is possible to optimize light propagation effects at both the macro- and microscale and to exploit their whole potential for the manipulation and optimization of optical and photonic devices.

The objective of this paper is to investigate nonlinear effects in Wavelength-Division Multiplex (WDM) systems in the case when different types of high-order M-PSK and M-QAM modulation formats for various structures of channel spacing are used optical signals. In general, the degradation mechanisms are caused by transmitted optical signals and their impact on each optical channel in WDM can be very different. Therefore, it is suitable to investigate possibilities for channel arrangement from the point of view of equidistant and non-equidistant channel spacing, respectively, what would lead to the suppression of nonlinear effects. In this article we investigate new types of high-order modulation formats that have ability for increasing of spectral efficiency and total improvement of performance of the transmission WDM system. The attention is put on two classes of channel spacing in WDM system, equidistant channel spacing (Δf = 100, 50, 25 and 12.5 GHz) and non-equidistant channel spacing (Δf ≠ const.), respectively. For investigation of signal propagation the numerical model is created. The model is based on mathematical method Symmetrical-Split Step Fourier Method (S-SSFM), which is utilized for solving the coupled nonlinear Schrödinger's equations (CNLSE) describing the transmission of signals in multichannel systems. The results of the created numerical model are analyzed, compared to each other and interpreted in a way that leads to the determination of suitable high-order modulation formats and we try to propose the optimal arrangement of optical channels in WDM system. The key issue is to suppress the impact of nonlinearities on modulated signals for each channel with respect to the employed types of digital modulation formats, various system parameters, different types of optical fibers and localization of reference channel in the wavelength area.

In this paper we present the experimental generation of complex beams by means of a polarization holographic technique. The interference of a reference Gaussian beam and a complex beam having opposite circular polarization states, stored on a highly polarization sensitive material, generates polarization holograms whose diffracted beams are high quality complex fields. The technique is tested with the generation of three different types of beams: a simple vortex, a Bessel and a Laguerre-Gaussian beam. This suggests an alternative method for the generation of complex beams with predetermined polarization states.

With the ever-increasing prevalence of minimally invasive procedures (MIP) in the medical world, the designing of endoscopes, essential in MIP, becomes more and more challenging. As the continuous and ubiquitous need for miniaturization is starting to outmatch the possibilities offered by the combination of conventional fibre optics and micro-optics, novel approaches are necessary in order to ensure the advancement of endoscopy and consequently of MIP. In conventional fibre bundles the phase-relation between cores is not conserved during the propagation of an electrical field and as such extra micro-optics at the distal end are necessary in order to be able to focus or scan the exiting light or achieve a certain field of view (FOV). In this paper we analyze the requirements and constraints for a multi-core optical fibre (MCF) which conserves the phase relationship between the cores. With such a phase conserving MCF, focusing and scanning light at the distal end could be done by shaping the wavefront through adaptive optics before coupling the light into the fibre therefore making extra micro-optics superfluous. Using numerical and mode solving simulations we investigate the relationship between the size, the period and the numerical aperture of the cores on the one hand and the focal point and field of view on the other hand. We show that there is a non-circumventable trade-off between intercore crosstalk and the FOV. In addition, we determine the effects on the focusing ability and on the FOV of deviations of core size and period, due to fabrication errors. Using this knowledge, we propose two designs for the phase conserving MCF. The first design allows for focusing and scanning the exiting light but is sensitive to deviations in core size and separation. The second design is less sensitive to fabrication errors but can only focus and not sweep.

In this study, a tool was developed to calculate the bulk optical properties for systems consisting of an absorbing medium and polydisperse spherical particles that can scatter and/or absorb. The developed tool is based on the Mie-theory for monodisperse-spherical absorbing and scattering particles in vacuum. First, the original Mie-theory was expanded to also include physical (real part of refractive index) and chemical (aborption, imaginary part of refractive index) information of the host medium. Secondly, the polydispersity of the spherical particles was taken into account. Since particle size distributions (PSD) are typically continuous distributions and Mie-scattering properties can only be calculated for a monodisperse system, the PSD is fractionated and Mie-scattering properties were calculated for each fraction. These Mie-scattering properties are then combined with the weight for each fraction to derive bulk optical properties. As the number of fractions is unknown and needs to be optimized for each calculation, the developed tool keeps on fractionating until the desired properties (μ_abs, μ_sca and P₁₁(cos(θ))) converge to stable values. This flexible tool allows for the simulation of the bulk optical properties for a wide range of wavelengths, particle volume fractions, complex refractive indices of both the particles and the medium and PSD's based on normal, lognormal, gamma, bimodal and custom defined functions. This code was successfully validated for the case of a lognormal PSD of scattering spheres in vacuum by comparing the simulated values to those reported in literature. The main novelties of the developed program are the extension of Mie-theory simulations to the case of polydisperse scattering particles in absorbing media and the automatic optimization of the number of PSD fractions needed to converge.

This paper presents an adaptation of the widely accepted Monte Carlo method for Multi-layered media (MCML). Its original Henyey-Greenstein phase function is an interesting approach for describing how light scattering inside biological tissues occurs. It has the important advantage of generating deflection angles in an efficient - and therefore computationally fast- manner. However, in order to allow the fast generation of the phase function, the MCML code generates a distribution for the cosine of the deflection angle instead of generating a distribution for the deflection angle, causing a bias in the phase function. Moreover, other, more elaborate phase functions are not available in the MCML code. To overcome these limitations of MCML, it was adapted to allow the use of any discretized phase function. An additional tool allows generating a numerical approximation for the phase function for every layer. This could either be a discretized version of (1) the Henyey-Greenstein phase function, (2) a modified Henyey-Greenstein phase function or (3) a phase function generated from the Mie theory. These discretized phase functions are then stored in a look-up table, which can be used by the adapted Monte Carlo code. The Monte Carlo code with flexible phase function choice (fpf-MC) was compared and validated with the original MCML code. The novelty of the developed program is the generation of a user-friendly algorithm, which allows several types of phase functions to be generated and applied into a Monte Carlo method, without compromising the computational performance.

The Talbot-Lau arrangement is an optical system using two gratings of different pitches. The gratings are placed parallel with some distance separated. By illuminating them with a broad incoherent source, we obtain high contrast grating images formed on a plane at a distance determined by the pitches. The phenomenon is called generalized grating imaging. It is used, for example, in pattern projection profilometer and as a shearing interferometer for light, X-ray and matter waves. There are many analyses on the Talbot-Lau arrangement. However, almost all of them are related to onedimensional gratings. This paper presents a rigorous analysis on the phenomenon with two-dimensional gratings using wave optics. The analytical result is applied to hexagonal gratings and the contrast is calculated by numerical calculation. The numerical results agree with experimental results. The analysis can be used to design a Talbot-Lau arrangement with two-dimensional gratings in broad fields.

The B-spline modal method is adapted for the design and analysis of nanostructured devices in conical mounting. The eigenmodes in each layer are calculated for two specific polarization states, and then combined for the calculation of the scattering matrices. We take advantage of the sparsity of the generated matrices to decrease the computation time, and adress the need for fast computation in complex systems. Moreover, we demonstrate the physical interest of computing the conical response on various classical structures.

A technique for flattening the chromatic dispersion in silicon nitride waveguides with silica cladding is proposed and numerically investigated. By modifying the transversal dimensions of the silicon nitride core and by adding several cladding layers with appropriate refractive indices and thicknesses, we demonstrate dispersion flattening over large spectral bandwidths in the near infrared. We analyze several cladding refractive index profiles that could be realistically fabricated by using existing materials and doping procedures. We show that cladding engineering allows for much more dispersion control (and flattening) in comparison with optimizing only the core transversal dimensions. For the latter case it is demonstrated that while the zero dispersion wavelength can be shifted to a great extent, the effect of the cross-section adjustment in the flatness is very limited. In sharp contrast, by adding two cladding layers and decreased refractive index values, the dispersion ripple can be strongly reduced. By further adding one more layer and by adjusting their refractive indices it is possible to obtain nearly constant chromatic dispersion (only +/- 3 ps/nm-km variation) over the spectral region from 1.8 to 2.4 microns. In our calculations, the analyzed change in the silica or silicon nitride refractive index is up to +/-3%. Our technique should open new avenues for the demonstration of high-performance nonlinear devices on a chip. Furthermore highly dispersive integrated photonic components can be envisaged for slow light applications and integrated photonics spectrographs.

The paper presents theoretical and experimental investigations of light beam self-trapping in a photorefractive medium based on Plexiglas (polymethylmethacrylate, PMMA) with photosensitive phenanthrenequinone (PQ)- molecules. It is shown that the self-trapping of a laser beam is generated due to the self-interaction of the propagating light wave under the conditions of a well balanced concurrence of the effects of light diffraction and nonlinear focusing. A new method for controlling the waveguide cross-section by changing the ratio of two competing mechanisms of the nonlinear refractive-index variation (namely the formation of the photoproducts and the heating of the medium while varying the power of the light beam) is proposed. The recording of self-trapping structures implemented in PQ-PMMA layers has been realized with two laser sources (405 nm and 514.5 nm) with an average power of several mW. It is shown that the photoattachment of the PQ-molecules to the polymeric chains and the formation of the photoproduct play the decisive role for the light-induced increase of the refractive index. Besides, the formation of the waveguide is strongly influenced by heating of the medium, which results in an additional thermal defocusing of the light beam. It has been established that the parameters of the waveguide (cross-section and length) are strongly dependent on the wavelength and the power of the laser radiation, as well as on the concentration of the PQ-molecules. Waveguiding structures with a diameter of 100 μm were recorded in samples with a high PQ-concentration (up to 4 mol.%) for the wavelength of 514.5 nm. Reducing the dye-concentration by one order requires shorter (blue) wavelengths (405 nm). The dependence of the waveguide parameters and the optimal laser wavelength on the concentration of PQ-molecules is confirmed by the numerical calculation including a 3D-model of the light self-trapping.

Speckle fields are formed when quasi-monochromatic light is scattered by an optically rough surface. These fields are usually described by reference to their first and second order statistical properties. In this paper we review and extend some of these fundamental properties and propose a novel technique for estimating the refractive index of a smooth sample. Theoretical and experimental results are presented. Separately, we also report on a preliminary experiment to determine some characteristics of speckle fields formed in free space by a rotating compound diffuser. Some initial measurements are made where we examine how the speckle intensity pattern in the output plane changes as a function of the relative rotation angle.

Recently, the development of optical setups capable of generating beams with arbitrary polarization have attracted broad interest. One possible way to implement such devices is by taking advantage of the properties of liquid crystal spatial light modulators, which act as optical phase retarders controlled by computer. In this communication we present the design of an alternative experimental setup for the generation of light beams with arbitrary spatially-variant polarization distribution. The objective is to develop a flexible optical device capable of dynamically encode any elliptical polarization state in each point of the wavefront. Our approach is based on a Mach-Zehnder setup combined with a translucent modulator in each path of the interferometer. The transverse beam components of the incident light beam are processed independently, and modified by means of their respective modulator displaying a specifically tailored computer generated phase hologram.

An exact synthesis algorithm for dielectric thin film filters with uniform optical phase thickness was first presented in 2004. This algorithm computes at least one thin film stack which realizes a given filter function. The feasibility is guaranteed by a set of necessary and sufficient conditions the filter function has to fulfill. This set of conditions only guarantees strictly positive refractive index values for all thin film layers. For a technological realization strictly positive refractive index values are insufficient since only certain refractive index values can be realized for a thin film layer. In this paper an additional condition for the location of the zeros of the filter response function is derived. Starting point is a boundary condition for the refractive index value for each of the N layers of the filter stack. Each refractive index value can be selected arbitrarily from an interval which is bounded by a lower and an upper refractive index boundary value. This additional zero location condition is necessary that at least one filter stack exists which fulfills these boundary conditions to a given filter function. Since the boundary conditions are determined by the used fabrication process for thin film filters the presented additional condition for the location of the zeros has to be calculated only once when a new process is installed.

Numerical calculations with nite-dierence time-domain (FDTD) on metallic nanostructures in a broad optical spectrum require an accurate approximation of the permittivity of dispersive materials. In this paper, we present the algorithms behind B-CALM (Belgium-California Light Machine), an open-source 3D-FDTD solver operating on Graphical Processing Units (GPUs) with multi-pole dispersion models. Our modied architecture shows a reduction in computing times for multi-pole dispersion models. We benchmark B-CALM by computing the absorption eciency of a metallic nanosphere on a broad spectral range with a six-poles Drude-Lorentz model and compare it with Mie theory.

Through numerical simulations we have shown that particle plasmon resonance wavelength is dependent mostly on the largest particle in an array of gold nanodisks. Mixing different sized nanodisks may shift the resonance peak wavelength from a few nanometers to tens of nanometers. The effect of period to the resonance peak strength was found to be dependent on the disk diameter in unexpected way. With smaller nanodisks increasing the period decreases peak absorption, but with larger still greatly sub-wavelength particles increasing the period can increase the absorption at resonance peak while decreasing absorption elsewhere on the spectrum giving great selective contrast.

Multi-dielectric coatings are designed to reach total absorption and maximum field amplification at resonances under total reflection. The design method is analytic and numerical results are given. Comparison with plasmons or thin metallic layers is discussed. Scattering from these coatings is investigated for measurements of amplification.

Recent developments in design algorithm enable to design freeform surfaces that generate intensity distributions with middle to high spatial frequency. Such freeform surfaces can generate a picture in a defined plane. In contrast to conventional imaging, the light modulation is done by a ray-optical redistribution of the incident light comparable to incoherent beam shaping. Such picture-generating freeform surfaces have various advantages. As only one single optical element is needed to generate the intensity distribution, very compact optical systems can be designed. Additionally, they are highly energy efficient, as nearly 100% of the incident light is directed into the image plane. In case of a freeform mirror, the system is wavelength independent, which offers the possibility for applications in UV or IR spectral range, as well as the polychromatic projection without any chromatic aberration. As no classical imaging is performed, conventional evaluation criteria concerning the resolution of this picturegenerating system like e.g. the Rayleigh criterion cannot be applied. In order to simulate diffraction effects in the picture plane, the wave-optical propagation has to be simulated. However, depending on the geometrical arrangement of such systems, the surface modulation of the freeform can be up to several millimeters. This leads to a violation of the thin element approximation and to significant sampling problems using conventional propagation algorithms. Therefore, we used a propagation method based on the Huygens-Fresnel principle. The physical formation of the intensity distribution of a picture-generating freeform system was simulated and the diffraction limit evaluated. We will show that such systems have a significantly lower resolution than conventional imaging systems. However, they are very well suited for middle- and low-resolution applications.

The effect of internal conical refraction in biaxial crystals is applied for transforming the lowest-order Gaussian laser beams into optical vortex beams and annular beams with radial and azimuthal polarization. The evolution of the emerging vortex beams upon propagation is analyzed and compared with the reference Laguerre-Gauss beam. The formation of beams with radial and azimuthal polarization with the aid of two biaxial crystals placed into the arms of a Mach-Zehnder interferometer is demonstrated.

A novel fly's eye homogenizer for single mode laser diodes is presented. Laser speckle has been removed and a uniform laser line illumination has been obtained for the first time with the proposed fly's eye homogenizer incorporating a single mode laser diode by introducing a staircase element and short pulse switching of the injection current. The former degrades the spatial coherence of the adjacent beamlets emanating from the microlens arrays while the latter simultaneously shortens the temporal coherence time so that the necessary optical path lengths in the staircase element become realistic in size. An average speckle contrast of 5% was achieved with the new fly's eye homogenizer whereas the standard fly's eye homogenizer at a CW driving yielded a high contrast of 87%. The diffraction theory for partial coherent light based on Wolf's formulation was extended to a simplified model of the new fly's eye homogenizer. The effect of the pulse width on the speckle contrast of the laser line illumination is experimentally shown and is discussed through a detailed analysis of the power spectrum and the fringe visibility, and a numerical study on the Dirichlet kernel based on the derived formulation for the intensity.

Low-height camera modules are demanded for such applications as cellular phones and vehicles. For designing optical lens, it has widely been recognized that a trade-off exists between reducing the number of lenses and camera resolution. The optical performance of imaging lenses has been improved by diffraction gratings, which have a peculiar inverse dispersion in the wavelength and exhibit the efficacy of correction for chromatic aberration. We can simultaneously reduce the number of lenses and maintain optical resolution using diffraction gratings. However, we have found a generation of striped flare lights under intense light sources that differ from unnecessary order diffraction lights. In this paper, we reveal the generation mechanism of these new striped diffraction lights and suggest a novel structure of diffraction gratings that can decrease them.

An InfraRed (IR) cooled camera is generally composed by an optical block (warm lenses outside a dewar) and a detection block (a cooled focal plane array inside the dewar). A minimalist approach to design a compact and robust camera consists in giving the dewar an imaging function by replacing the cold pupil by a Diffractive Optical Element (DOE). In this paper we present different DOE that can be used to design the camera. We present first a pinhole camera that validates this approach but that is limited in radiometric performances and in angular resolution. We replace then the pinhole by a continuously self-imaging DOE, such as the diffractive axicon, to improve both the radiometric performances and the angular resolution. Finally, the MALDA is introduced to improve the performances of the axicon. Diffraction effects and Talbot effect under polychromatic light are exposed for such DOE and two different design rules are derived from those effects to allow the design of a compact camera with dimensions compatible with the size of an industrial dewar. Experimental prototypes are presented and radiometric performances are compared and show the best performances for the MALDA.

We report on holographic storage of digital data pages in a thick silica nanoparticle-polymer composite film that uses step-growth thiol-ene photopolymerization at a wavelength of 532 nm. Shift-multiplexed holographic storage of 180 digital data pages with a two-dimensional 2:4 modulation code was successfully demonstrated with low symbol-error rates. This result clearly shows the feasibility of the thiol-ene based nanoparticle-polymer composite system as holographic data storage media.

We report on a statistical thermodynamic simulation of holographic photopolymerization in a holographic polymer-dispersed liquid crystal under holographic exposure. We employ the dynamic density functional theory to study the spatio-temporal evolution of monomer, polymer and liquid crystal distributions as continuous density order parameters in numerical simulations. Density-dependent mutual diffusion of monomer, polymer and liquid crystals are taken into account under the constraints of the mass conservation and the incompressibility conditions by using the Lagrange multiplier method. The autocatalytic model is employed to describe the photopolymerization kinetics. The simulation results are compared with measured results such as the average size of liquid crystal droplets and a grating-spacing dependence of the formed refractive index modulation.

The Non-local Photo-Polymerization Driven Diffusion (NPDD) model was introduced to describe the observed drop-off in the material's response for higher exposing spatial frequencies. Recent work carried out on the modeling of the mechanisms which occur in photopolymers during- and post-exposure, has led to the development of a tool, which can be used to predict the behaviour of these materials under a wide range of conditions. In this article, based on the chemical reactions of chain transfer agents, we explore this extended NPDD model, illustrating some of the useful trends, which the model predicts and we analyse their implications on the improvement of photopolymer material performance.

A new low-toxicity diacetone acrylamide-based photopolymer is developed and characterized. The environmentallycompatible photopolymer has been modified with the inclusion of glycerol. The incorporation of glycerol results in a uniform maximum refractive index modulation for recording intensities in the range of 1-20 mW/cm². This may be attributed to glycerol's nature as a plasticizer, which allows for faster diffusion of un-reacted monomer within the grating during holographic recording. An optimum recording intensity of 0.5 mW/cm² is observed for exposure energies of 20- 60 mW/cm². The modified photopolymer achieves a refractive index modulation of 2.2×10^-3, with diffraction efficiencies up to 90 % in 100 μm layers. The photopolymer layers containing glycerol have improved stability and optical quality.

An understanding of the photochemical and photo-physical processes, which occur during photo-polymerization, is of extreme importance when attempting to improve a photopolymer material's performance for a given application. Recent work carried out on the modeling of photopolymers during- and post-exposure, has led to the development of a tool, which can be used to predict the behavior of a number of photopolymers subject to a range of physical conditions. In this paper, we explore the most recent developments made to the Non-local Photo-polymerization Driven Diffusion model, and illustrate some of the useful trends, which the model predicts and then analyze their implications on photopolymer improvement.

Over the past century, monitoring of Giardia lamblia became a matter of concern for all drinking water suppliers worldwide. Indeed, this parasitic flagellated protozoan is responsible for giardiasis, a widespread diarrhoeal disease (200 million symptomatic individuals) that can lead immunocompromised individuals to death. The major difficulty raised by Giardia lamblia's cyst, its vegetative transmission form, is its ability to survive for long periods in harsh environments, including the chlorine concentrations and treatment duration used traditionally in water disinfection. Currently, there is a need for a reliable, inexpensive, and easy-to-use sensor for the identification and quantification of cysts in the incoming water. For this purpose, we investigated the use of a digital holographic microscope working with partially coherent spatial illumination that reduces the coherent noise. Digital holography allows one to numerically investigate a volume by refocusing the different plane of depth of a hologram. In this paper, we perform an automated 3D analysis that computes the complex amplitude of each hologram, detects all the particles present in the whole volume given by one hologram and refocuses them if there are out of focus using a refocusing criterion based on the integrated complex amplitude modulus and we obtain the (x,y,z) coordinates of each particle. Then the segmentation of the particles is processed and a set of morphological and textures features characteristic to Giardia lamblia cysts is computed in order to classify each particles in the right classes.

We developed a new off-axis digital holographic microscope (DHM), working in transmission with a RGB LED illumination. This partially coherent multi-wavenlenght source gives a low noise holograms and the intensity image quality is fully exploitable for microscopy purposes. We implemented a full off-axis configuration enables the recording of the holographic data in one shot. As we used for the first tests a monochromatic CCD camera, the holograms are recorded separately in each spectral channel. The holograms are individually processed by the Fourier method to obtain, in each color, the complex amplitudes and the corresponding intensities and optical phases. The color intensities are recombined to obtain a composite RGB color image. The digital holographic refocusing and the optical phase map computation are successfully demonstrated. The multi-wavelengths operation provides a significant improvement of the collected information for colored samples. The full one-shot color hologram recording should be available with a color camera.

We propose a new Iterative Fourier Transform Algorithm (IFTA) capable to suppress ghost traps and noise in Holographic Optical Tweezers (HOT), maintaining a high diffraction efficiency in a computational time comparable with the others iterative algorithms. The process consists in the planning of the suitable ideal target of optical tweezers as input of classical IFTA and we show we are able to design up to 4 real traps, in the field of view imaged by the microscope objective, using an IFTA built on fictitious phasors, located in strategic positions in the Fourier plane. The effectiveness of the proposed algorithm is evaluated both for numerical and optical reconstructions and compared with the other techniques known in literature.

We propose a new denoising algorithm in off-axis Digital Holography (DH) based on l1 norm minimization. The aim of our work is to assess a general denoising scheme of digital holograms, i.e. we do not explore prior knowledge of the statistics of the digital holograms. For this purpose, we consider different experimental conditions such as a digital holograms recorded in microscope configuration and lensless configuration. We use the inherent sparsity of the numerical reconstruction of digital holograms in order to optimize the in-focus digital reconstructions. For this reason, we call the proposed algorithm SPADEDH (SPArsity DEnoising of Digital Holograms). We perform also a display test, by using a Spatial Light Modulator (SLM) as a projection system, for the digital holograms recorded in lensless configuration. In both numerical reconstruction and display test, the improvements of the SPADEDH algorithm are computed.

The Smart X-Ray Optics (SXO) project comprises a UK-based consortium developing active/adaptive micro-structured optical arrays (MOAs). MOA devices are designed to focus X-rays using grazing incidence reflection through consecutive aligned arrays of microscopic channels. Adaptability is achieved using a combination of piezoelectric actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the edges of the chip with the active area at the centre, effectively amplifying the bend radius. The spider actuation concept, in combination with deep silicon etching stopped close to the surface, can also be used to create deformable mirrors where the curvature and tip/tilt angles of the mirror can be controlled. Finite Element Analysis (FEA) modelling, carried out for the optimization of the spider MOA device, indicates that deformable mirrors with curvature varying from flat to 5cm ROC and control over the tip/tilt angles of the mirror of +/-3mrad could be achieved. Test spider structures, manufactured using a Viscous Plastic Processing Process for the PZT piezoelectric actuators and a single wet etch step using <111> planes in a (110) silicon wafer for both the silicon channels and the spider structure, have been bent to a radius of curvature smaller than 5 cm. This paper evaluates the spider MOA's concept as a means to achieve deformable mirrors with controllable ROC and control over the tip/tilt angles. FEA modelling results are compared with obtained characterization data of prototype structures. Finally, manufacturing and integration methods and design characteristics of the device, such its scalability, are also discussed.

Digital Holographic Microscopy (DHM) is a powerful tool that strongly increases the field of investigation of classical microscopy. It allows to be used as phase contrast microscopy with the additional information of the z position over a whole experimental volume by acquiring a single frame. The use of a spatially reduced coherent source strongly reduces the coherent noise. Vesicles are close lipid membranes enclosing a sugar-water solution. Those biomimetic deformable objects are good mechanical models of living cells such as Red Blood Cells. We investigate the dynamics of a vesicle suspension in shear flow between walls (with a gap of about 200 μm). When vesicles are placed in a shear flow, they undergo a lift force that pushes them away from the wall until they reach the centre of the channel where the effects of both walls are compensated. On the other hand, hydrodynamical interactions between vesicles and segregation effects tend to push small vesicles away from the centre of the channel. The final distribution is thus a compromise between both effects that structures the distribution and has strong impact on rheology. DHM with reduced coherence and specific related algorithms (phase compensation, best focus plane determination, segmentation, ...) provide a full description of each object in the experimental volume as a function of their size and shape. Results are provided and illustrate the quantification of the lift force and the hydrodynamical interactions (shear induced diffusion).

The propagation of coherent light through a heterogeneous medium is an often-encountered problem in optics. Analytical solutions, found by solving the appropriate differential equations, usually only exist for simplified and idealized situations limiting their accuracy and applicability. A widely used approach is the Beam Propagation Method in which the electric field is determined by solving the wave equation numerically, making the method time-consuming, a drawback exacerbated by the heterogeneity of the medium. In this work we propose an alternative approach which combines, in an iterative way, optical ray-tracing simulation in the software ASAP™ with numerical simulations in Matlab in order to model the change in light distribution in a medium with anisotropic absorption, exposed to partially coherent light with high irradiance. The medium under study is a photosensitive polymer in which photochemical reactions cause the local absorption to change as a function of the local light fluence. Under continuous illumination, this results in time-varying light distributions throughout the irradiance process. In our model the fluence-absorption interaction is modelled by splitting up each iteration step into two parts. In the first part the optical ray-tracing software determines the new light distribution in the medium using the absorption from the previous iteration step. In the second part, using the new light distribution, the new absorption coefficients are calculated and expressed as a set of polynomials. The evolution of the light distribution and absorption is presented and the change in total transmission is compared with experiments.

Martian atmosphere contains a significant and rapidly changing load of suspended dust that never drops to zero. The main component of Martian aerosol is micron-sized dust thought to be a product of soil weathering. Although airborne dust plays a key role in Martian climate, the basic physical properties of these aerosols are still poorly known. The scope of Mars MetNet Mission is to deploy several tens of mini atmospheric stations on the Martian surface. MEIGA-MetNet payload is the Spanish contribution in MetNet. Infrared Laboratory of University Carlos III (LIR-UC3M) is in charge of the design and development of a micro-sensor for the characterization of airborne dust. This design must accomplish with a strict budget of mass and power, 45 g and 1 W respectively. The sensor design criteria have been obtained from a physical model specifically developed for optimizing IR local scattering. The model calculates the spectral power density scattered and detected