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X-ray imaging by means of a grating-based Talbot-Lau interferometer has become an important tool for a wide variety of application areas such as security, medical and materials analysis. Imaging modalities include attenuation, differential phase contrast, and visibility contrast (or so-called dark field). We have developed a novel modeling approach based on ray tracing with commercially available software (Zemax OpticStudio) that yields image projections for all three modalities. The results compare favorably with experimental findings. Our polychromatic ray-based model accommodates realistic 3-D CAD objects with tailored materials properties and also allows for both surface and bulk scattering. As such, the model can simulate imaging of complicated objects as well as assist in a physical understanding of experimental projection details.

Ultraviolet decontamination of personal protective equipment, particularly masks, is important in situations where mask reuse is practiced. To assist in the development of UV-C decontamination chambers, we have constructed ray tracing models in Zemax OpticStudio v20.1 for two distinct geometries, namely, a rectangular cabinet and a cylindrical can. These models provide irradiance distributions that can be used for comparison with experiment, as well as to predict local irradiance variation over the surface of a mask. In this paper we describe the model details, including: (1) a mask object in CAD format; (2) our assumptions for modeling surface properties; (3) the use of polygon object detectors for local irradiance analysis; and (4) experimental results that compare favorably to the simulations.

A grating-based Talbot-Lau X-ray interferometer provides three imaging modalities, namely attenuation, differential phase contrast, and dark field. Of these, dark-field imaging is uniquely capable of detecting and characterizing micron-scale fine structure in an object via small-angle scattering that reduces fringe visibility. In Part 1 [Opt. Express 29, 40891 (2021)10.1364/OE.447794], we formulate a statistical optics model that predicts the change in visibility, or dark-field signal, as a function of the statistical properties of the scattering object as well as its location within the interferometer. In Part 2, we demonstrate use of this model by simulating an object comprising a random collection of scattering microspheres placed in an X-ray grating interferometer designed to operate at 28 keV. The statistical optics results are validated by numerical Fourier optics simulations.

A grating-based Talbot-Lau X-ray interferometer provides three imaging modalities, namely attenuation, differential phase contrast, and dark field. Of these, dark-field imaging is uniquely capable of detecting and characterizing micron-scale fine structure in an object via small-angle scattering that reduces fringe visibility. Several empirical studies have been published showing the utility of this imaging modality for a wide range of applications. There also exists a more limited set of theoretical papers, based primarily on wave-optics formulations. In this two-part paper we present a comprehensive statistical optics model of the dark-field effect. In Part 1, we develop the theoretical underpinnings of the model with an emphasis on a scattering object comprising a random collection of microspheres, and in Part 2 [Opt. Express 29, 40917 (2021)10.1364/OE.447798], we provide a variety of example simulation results.

Typical x-ray detectors have a fundamental trade-off between resolution and quantum efficiency (QE). High quantum efficiency x-ray detection requires a thick conversion medium, but decreases the resolution due to limited pixel aspect ratios for both direct and indirect x-ray detection. We present a method for x-ray detection, holographic x-ray detection, which uses photorefractive materials to create a high resolution and high efficiency detector. The x-ray image is recorded in the volume of the photorefractive material, bypassing the aspect ratio issue of typical x-ray detectors. Holographic x-ray detection operates in three stages: recording an x-ray hologram in a photorefractive crystal, reading the hologram with visible light, and then erasing the hologram using ultraviolet light. We have experimentally demonstrated holographic x-ray detection with a resolution of 208 lp/mm (80% QE at 40 keV), an order of magnitude resolution improvement over commercially available x-ray detectors while maintaining > 80% QE.

We present evidence-based design principles for three different UV-C based decontamination systems for N95 filtering facepiece respirators (FFRs) within the context of the SARS-CoV-2 outbreak of 2019–2020. The approaches used here were created with consideration for the needs of low- and middle-income countries (LMICs) and other under-resourced facilities. As such, a particular emphasis is placed on providing cost-effective solutions that can be implemented in short order using generally available components and subsystems. We discuss three optical designs for decontamination chambers, describe experiments verifying design parameters, validate the efficacy of the decontamination for two commonly used N95 FFRs (3M, #1860 and Gerson #1730), and run mechanical and filtration tests that support FFR reuse for at least five decontamination cycles.

This Letter covers the design and implementation of a generalizable system for the precise alignment of X-ray gratings. Next-generation high-energy grating-based Differential Phase Contrast (gDPC) X-ray imaging systems require precise alignment of the X-ray gratings as low as 1 mrad in rotation and 0.5 mm in translation. In this work, we designed holographic fiducial marks, consisting of four reflective Fresnel zone plates, each placed in a separate quadrant of the mark. When illuminated with a collimated laser beam, each mark creates a predefined pattern of four points, which changes quantitatively for any misalignment in each of the three translational and three rotational degrees of freedom. We fabricated the designed fiducial marks using photolithography and etching processes. The experimental system is implemented using a HeNe laser and an optical imaging system, which includes a beam expander, a plate beam splitter, and a CMOS camera, suitable for aligning practical gratings in gDPC X-ray imaging systems. Our experimental results demonstrate the rotational precision capabilities of the reported alignment system down to 0.42 mrad around the optical axis and 0.03 mrad around the axes perpendicular to the optical axis. The translational precision of 83.64 μ m along the optical axis and 1.22 μ m along the axes perpendicular to the optical axis is also demonstrated.This Letter covers the design and implementation of a generalizable system for the precise alignment of X-ray gratings. Next-generation high-energy grating-based Differential Phase Contrast (gDPC) X-ray imaging systems require precise alignment of the X-ray gratings as low as 1 mrad in rotation and 0.5 mm in translation. In this work, we designed holographic fiducial marks, consisting of four reflective Fresnel zone plates, each placed in a separate quadrant of the mark. When illuminated with a collimated laser beam, each mark creates a predefined pattern of four points, which changes quantitatively for any misalignment in each of the three translational and three rotational degrees of freedom. We fabricated the designed fiducial marks using photolithography and etching processes. The experimental system is implemented using a HeNe laser and an optical imaging system, which includes a beam expander, a plate beam splitter, and a CMOS camera, suitable for aligning practical gratings in gDPC X-ray ...

We propose a method for peristaltic transport of nanoparticles using the optical force field over a nanostructured surface. Nanostructures may be designed to produce strong near-field hot spots when illuminated. The hot spots function as optical traps, separately addressable by their resonant wavelengths and polarizations. By activating closely packed traps sequentially, nanoparticles may be handed off between adjacent traps in a peristaltic fashion. A linear repeating structure of three separately addressable traps forms a "nano-optical conveyor belt"; a unit cell with four separately addressable traps permits controlled peristaltic transport in the plane. Using specifically designed activation sequences allows particle sorting.

Optical tweezers have been widely used to manipulate biological and colloidal material, but the diffraction limit of far-field optics makes focused beams unsuitable for manipulating nanoscale objects with dimensions much smaller than the wavelength of light. While plasmonic structures have recently been successful in trapping nanoscale objects with high positioning accuracy, using such structures for manipulation over longer range has remained a significant challenge. In this work, we introduce a conveyor belt design based on a novel plasmonic structure, the resonant C-shaped engraving (CSE). We show how long-range manipulation is made possible by means of handoff between neighboring CSEs, and we present a simple technique for controlling handoff by rotating the polarization of laser illumination. We experimentally demonstrate handoff between a pair of CSEs for polystyrene spheres 200, 390, and 500 nm in diameter. We then extend this technique and demonstrate controlled particle transport down a 4.5 μm long "nano-optical conveyor belt."

Nanoparticles trapped on resonant near-field structures engraved on a metallic substrate experience forces due to the engravings, as well as the image-like interaction with the substrate. In the case of normally incident optical excitation, the force due to the substrate is solely perpendicular to its surface. Numerical simulations are presented to demonstrate that under the combined influence of the aforementioned forces, a plasmonic nanoparticle can be repelled from the engraving along the substrate, while attracting it towards the substrate along its normal. This behavior can be achieved over a range of excitation wavelengths of the short wavelength mode of the coupled particle-substrate-trap system. To the best of our knowledge, this is the first illustration of an in-plane near-field optical barrier on a chip. The barrier is stable against resistive heating of the nanoparticle, as well as the induced non-isothermal flow. The wavelength-dependent switch between the proposed in-plane potential barrier and the stable potential well can pave the way for the gated transport of single nanoparticles, while holding them bound to the chip.

In this review, an overview of the subwavelength confinement of light with plasmonics is presented. Among the varieties of state-of-the-art technologies on this intensively-studied topic, we focus on the surface plasmon-assisted light enhancement via the single metallic aperture. Based on a systematic overview of the physical principles of light enhancement in subwavelength-sized metallic apertures, we investigate various types of apertures and discuss their characteristics.

We present a method for obtaining accurate numerical design sensitivities for metal-optical nanostructures. Adjoint design sensitivity analysis, long used in fluid mechanics and mechanical engineering for both optimization and structural analysis, is beginning to be used for nano-optics design, but it fails for sharp-cornered metal structures because the numerical error in electromagnetic simulations of metal structures is highest at sharp corners. These locations feature strong field enhancement and contribute strongly to design sensitivities. By using high-accuracy FEM calculations and rounding sharp features to a finite radius of curvature we obtain highly-accurate design sensitivities for 3D metal devices. To provide a bridge to the existing literature on adjoint methods in other fields, we derive the sensitivity equations for Maxwell’s equations in the PDE framework widely used in fluid mechanics.

CsBr photocathodes have 10 times higher quantum efficiency with only 3 times larger intrinsic transverse emittance than copper. They are robust and can withstand 80 MV/m fields without breaking down or emitting dark current. They can operate in 2×10^{−9} torr vacuum and survive exposure to air. They are well suited for generating high pulse charge in rf guns without a photocathode transfer system.

We performed a parametric study to suppress secondary phases in lithium niobate thin films by using pulsed laser deposition (PLD). By reducing the growth rate and changing the ambient gas pressure respectively, we found that the main parameter suppressing secondary phases is controlling the plume strength. For investigating the relation between film phases and the plume strength, extensive parametric studies were performed by changing the oxygen ambient pressure, the target to substrate distance, and also the Li content in the target. The surface morphologies of single phase films obtained with different deposition parameters are compared and deposition parameters to achieve lower loss single-phase films are discussed.

In the implementation of most resolution enhancement techniques for optical lithography, full 3D simulation of effects such as topography imbalance in phase masks can be successfully modeled. However, these simulators do not appear to capture the full range of effects that impact the transmission of light through conducting (or partially conducting) films. In particular, certain resonant sub-wavelength geometric shapes, such as the C-aperture in a metallic conducting film, have been shown to have transmission values that are factors of 10^3-10^5 higher than simple geometric projections would predict. Using a new finite difference time domain solver that explicitly includes internal currents and analyzes the Poynting vector behavior of the EM fields, we can better understand the complex behavior of these resonant apertures. The currents are highly dependent on the polarization of the incoming EM excitation, as is the extraordinary transmission. We have also applied this in a limited fashion to geometries such as those expected to appear on photomasks in the 45nm node, when not extraordinary transmission but extraordinary opacity is predicted. These effects are also highly polarization dependent.

In this paper, we report the effects of direct-write e-beam parameters on achieving sub-micron periodic domain structures in homoepitaxial liquid phase epitaxy (LPE) LiNbO 3 thin films. We have studied the effects of the e-beam acceleration voltage, the areal dose, and the scanning speed on the domain structure regularity, and we have obtained optimal conditions for achieving improved structures. The most regular structures appear at acceleration voltages higher than 20 kV and areal dose ranges of 350–450 μC/cm 2 with lower scanning speeds. Under these optimal conditions we have fabricated approximately 500 μm-long gratings with 1.1 μm periods consisting of ∼180 nm domains. By simulating the optical reflectance based on a transfer matrix analysis, we have shown that the grating has a reflectance close to that of a perfect grating, in spite of the existence of stitching errors. The results indicate that using this fabrication approach, a switchable Bragg filter for optical communications may be fabricated by direct-write e-beam sub-micron domain engineering in LPE LiNbO 3 .

We have demonstrated sub-micron domain (∼200 nm) structures with a period ∼750 nm and ∼1.2 μm in liquid phase epitaxy (LPE) LiNbO3 films on congruent LiNbO3 substrates by using the direct-write e-beam domain engineering method. In comparison with single crystal congruent LiNbO3 (CLN) and stoichiometric LiNbO3 (SLN), we show that LPE LiNbO3 (LPE LN) is the most promising material for producing superior domain regularities and finer domain sizes than single crystals. A physical model is presented to qualitatively explain the observed differences in structure and regularity of the induced periodic domains among the three different materials we studied. We postulate that the higher Li/Nb ratio in LPE LN than in CLN enhances domain inversion initiation. Also, we believe that the vanadium incorporation and distortion due to the lattice mismatch between films and substrates enhance electron localization, domain wall pinning and domain nucleation in LPE materials, giving rise to better structures.

We transport nano-scale objects across a distance of many microns using a repeated sequence of rotated C-shaped plasmonic resonators. Rotating the polarization angle of the overhead laser illumination drives the particles' motion.

Near-field optical data storage systems are important for ultrahigh density data storage. One type of near-field optical data storage system uses a planar nano-aperture to define the data storage resolution. However, conventional nano-apertures have a tradeoff between resolution and power throughput. Recently, we reported a novel "C"-aperture design to overcome this problem. In this paper, we present our study on the mechanisms for power throughput enhancement, based on a detailed study of nano-slits using numerical simulations. We find that generating a propagation mode is essential for high power throughput, and by optimizing the design of the aperture thickness, resonant transmission can be achieved for even higher power throughput.

A semi-analytical model is proposed to describe the force generated by a near-field optical trap. The model contains fitting parameters that can be adjusted to resemble a reference force-field. The model parameters for a plasmonic near-field trap consisting of a C-shaped engraving are determined using least squares regression. The reference values required for the regression analysis are calculated using the Maxwell stress tensor method. The speed and accuracy of the proposed model are compared with the conventional method. The model is found to be significantly faster with an acceptable level of accuracy.

Nanoparticles trapped on resonant near-field apertures/engravings carved in plasmonic films experience optical forces due to the steep intensity gradient field of the aperture/engraving as well as the image like interaction with the substrate. For non-resonant nanoparticles the contribution of the substrate interaction to the trapping force in the vicinity of the trap (aperture/engraving) mode is negligible. But, in the case of plasmonic nanoparticles, the contribution of the substrate interaction to the low frequency stable trapping mode of the coupled particle-trap system increases as their resonance is tuned to the trap resonance. The strength of the substrate interaction depends on the height of the nanoparticle above the substrate. As a result, a difference in back action mechanism arises for nanoparticle displacements perpendicular to the substrate and along it. For nanoparticle displacements perpendicular to the substrate, the self induced back action component of the trap force arises due to changing interaction with the substrate as well as the trap. On the other hand, for displacements along the substrate, it arises solely due to the changing interaction with the trap. This additional contribution of the substrate leads to more pronounced back action. Numerical simulation results are presented to illustrate these effects using a bowtie engraving as the near-field trap and a nanorod as the trapped plasmonic nanoparticle. The substrate's role may be important in manipulation of plasmonic nanoparticles between successive traps of on-chip optical conveyor belts, because they have to traverse over regions of bare substrate while being handed off between these traps.

Codoped lithium niobate of congruent and stoichiometric compositions had been successfully grown specifically for holographic data storage applications. The dopants we have selected are Mn and Ce and their role in the recording process is described. Growth methods, sample preparation, doping level measurements, holographic recording data as well as the results of optical characterization and photorefractive properties of the two-photon sensitivity are discussed. Compared to the previously grown crystals, the codoped LiNbO 3 shows a higher sensitivity and dynamic range for recording in red ( λ=632 nm ).

Lead barium niobate (Pb1−xBaxNb2O6) is a very promising material for photorefractive applications in that it has a high ferroelectric-to-paraelectric transition temperature (300–500 °C depending on composition) and simultaneously can have large electro-optic coefficients, because of the nearly vertical morphotropic phase boundary (MPB) near 1−x=0.63. Pb1−xBaxNb2O6 crystals have been grown by the vertical Bridgman method for near-MPB compositions (0.5

Lead barium niobate crystals (Pb1−xBaxNb2O6) are attractive photorefractive materials for holographic data storage. The electro-optic coefficients r33 and r13 are determined using a Mach–Zehnder interferometer setup, and are measured to be 160±20 and 32±4 pm/V, respectively. The angular dependence of the photorefractive two-beam coupling gain is also investigated, and the products of the electro-optic coefficients and the electron-hole competition factor rζ are determined and compared with the electro-optic coefficients obtained using the interferometric method. It is found that the electron-hole competition factor is at least 0.7, indicating that the photorefractive process is mostly due to electrons. The effective trap densities at several wavelengths are also determined from the gain dispersion measurements, and are found to be 1.3–2.2×1016 cm−3.

We develop a plasmonic trapping and conveyor system based on resonant C-shaped engravings driven by polarization rotation and wavelength switching.

We develop a near-field based optical trapping and conveyor belt system based on a novel plasmonic structure: C-shaped engraving. Using polarization rotation and wavelength switching, we demonstrate controlled transport of nanoparticles along different paths.

X-ray differential phase contrast imaging system with a grating-less X-ray source and grating-less detectors are effective for applications with higher X-ray photon energy by decoupling a trade-off the parameters, signal contrast and field-of-view.

New multicomponent InF 3 -based bulk glasses have been investigated. The molar composition of the base glass is 28% InF 3 –20% ZnF 2 –16.5% BaF 2 –12% GaF 3 –9% PbF 2 –6% NaCl–5% SrF 2 –3% CaF 2 –0.5% PrF 3 . A number of variations of the base glass were prepared and their refractive indices and densities measured. Resistance to crystallization allowed the preparation of large pieces of the base glass. The infrared and Raman spectra show that the base composition has a longer wavelength multiphonon edge at 10 μm and a phonon energy of 509 cm −1 , in comparison with 8 μm and 574 cm −1 for ZBLAN, which reveals that the present glasses have a lower phonon energy and a greater transparency in the infrared than ZBLAN. Reduction of PbF 2 concentration in the base composition provided glasses with smaller refractive indices than the base glass.

A transient, two-dimensional drift-diffusion model is developed for optically addressed spatial light modulators made with quantum-well materials. The transport of free and well-confined carriers is considered along with nonlinear transport effects such as velocity saturation, field-dependent carrier escape from quantum wells, and resonant absorption. In addition to full numerical solutions to the transport equations, analytical and simplified numerical solutions are developed to describe basic screening behavior and to give estimates of speed and resolution performance. In particular, a self-consistent small signal model is developed to justify the surface-charge picture often used to describe device operation. This model is also used to simulate grating formation and decay. It is found that the maximum screening rate and peak grating amplitude are achieved using vertical drift lengths much longer than the device length. A detailed analysis of resolution performance is also given in which the effects of ...

A three-color, solid-state, volumetric display based on two-step, two-frequency upconversion in rare earth-doped heavy metal fluoride glass is described. The device uses infrared laser beams that intersect inside a transparent volume of active optical material to address red, green, and blue voxels by sequential two-step resonant absorption. Three-dimensional wire-frame images, surface areas, and solids are drawn by scanning the point of intersection of the lasers around inside of the material. The prototype device is driven with laser diodes, uses conventional focusing optics and mechanical scanners, and is bright enough to be seen in ambient room lighting conditions. QuickTime movie of the three-dimensional display.

We designed, fabricated, and characterized single C-shaped apertures in an Au film, resonant in the visible regime. Our C-shaped apertures showed transmission enhancement of 13–22 times over a square aperture of the same area and suggest as high as 106 enhancement over square apertures that are designed to produce the same near-field spot size. Spectra from individual apertures demonstrate the ability to tune this resonance over 70nm by scaling the dimensions of the apertures. This shows the C aperture to be a versatile tool for gaining high-resolution, enhanced transmission through single subwavelength apertures at optical wavelengths.

We report abnormally large positive and negative lateral optical beam shifts at a metal–air interface when the surface plasmon resonance of the metal is excited. The optimal thickness for minimal resonant reflection is identified as the critical thickness above which a negative beam displacement is observed. Experimental results show good agreement with theoretical predictions and the large observed bidirectional beam displacements also indicate the existence of forward and backward surface propagating waves at the surface plasmon resonance of the metal.

A zoom objective lens for a multi-layer optical rec ording has been designed. A newly proposed optical power arrangement enables varying back focal length while focal length invariant by a linear movement of sin gle zooming component. The zoom lens is implemented into multi- layer and multi-bit holographic recording system em ploying 405 nm blue lasers. 1. INTRODUCTION Recently, multilayer micro holographic optical disc systems have been investigated to attain high capa city and high data transfer rate [1,2]. In the multilayer recordi ng, micro-holograms are recorded throughout the vol ume of recording material by changing the recording depth. For such multilayer recording systems, objective l ens accesses to multiple recording layers. The design of objecti ve lens needs to satisfy couple of constraints. Fir st, working distance, air spacing between objective lens and re cording disc, is unchanged while changing the recor ding layer. Numerical aperture (NA) must be an invariant for th e range of recording depth to equalize transverse s ize and modulation of index of refraction of the micro holo grams. Ideally, the number of moving elements shoul d be a minimum. Also, a linear relation between zooming of the element and recording depth is preferable. Typical way to design such optics is depicted in Fi g. 1. First, an intermediate image, a virtual or re al one, is formed by a movable zooming optics. Then, the inter mediate image is relayed to a final focal point ins ide a recording medium by a secondary optics consisting o f high NA objective elements. Moving the first opti cs along optical axis alters conjugate ratio between the int ermediate image and final image, therefore, the fin al image position also moves, which ends up with selection of writing depth. The approach is rather a simple one however we immediately notice several drawbacks of the approac h if we recall the design requirement for optical d ata storage applications. First, the system focal length varies as the writing depth changes. Consequently, NA va ries as selection of recording layers. As a result, a varia ble aperture and tuning of laser power is needed to equalize the transverse size and modulation of index of refracti on of the micro holograms. Second, the location of the final image nonlinearly moves with respect to the movement of t he zooming element. This would impose an additional requirement on actuators for selection of writing d epth. To overcome such issues, we propose an optica l power arrangement having constant focal length as well as linear movement of zooming element. Note that, eve n being able to implement such additional features, the pro posed optical power arrangement requires only one m oving component. Thus, our approach inherits the simple i mplementation of the conventional approach. Importa ntly, such a minimum optical power arrangement is possible onl y if specific combination of power is adopted for t he zooming optical component. In this paper, first analysis of the proposed power arrangement is described. Based on the power arrangement, we discuss design of all off-the-shelf write/read optics having a constant numerical aper ture (NA) of 0.4 for a range of writing depth of 0.2 mm. Design and implementation of multi-layer and multi-bit mic ro holographic recording system employing blue lasers will be addressed.

Plasmonic Near-Field Transducers (NFTs) find use in Energy-Assisted Magnetic Recording (EAMR) schemes, where a high-anisotropy recording medium is locally heated to the Curie temperature, allowing conventional magnetic recording heads to overcome the high coercivity of the medium. However, coupling efficiency is low, and the conditions for excitation and resonance are poorly understood. In this work, we explore the behavior of a canonical EAMR setup including rectangular dielectric waveguide, elliptic cylinder gold NFT, and conductive planar recording medium. We systematically examine the effects of polarization and angle; spacing between NFT, waveguide, and recording medium; and variations in NFT size and incident wavelength.

We report a new optical near-field transducer comprised of a metallic nano-antenna extending from the ridge of a C-shaped metallic nano-aperture. Finite-difference time domain simulations predict that the C-aperture nano-tip (CAN-Tip) provides high intensity (650x), high optical resolution (~λ/60), and background-free near-field illumination at a wavelength of 980 nm. The CAN-Tip has an aperture resonance and tip antenna resonance which may be tuned independently, so the structure can be made resonant at ultraviolet wavelengths without being unduly small. This near-field optical resolution of 16.1 nm has been experimentally confirmed by employing the CAN-Tip as an NSOM probe.

A novel optical system architecture employing local holographic recording with a pico-second pulsed fiber laser and a small page size SLM has the potential towards realizing compact, high capacity and high data transfer rate optical storage.

We present a numerical technique for design and optimization of nanometallic structures for near-field optical applications such as heat-assisted magnetic recording (HAMR). The sensitivity of the optical behavior of a nanostructure with respect to its size and shape may be efficiently obtained with a pair of “forward” and “backward” FDTD simulations. Devices may be optimized by iteratively adjusting their dimensions along direction of highest sensitivity for improvement.

We propose a nano-scale C-aperture nano-tip photo-electron source with a CsBr photo-cathode. We fabricated the structure and estimated the optical spot available in the CsBr thin film with photoresist exposure.

Conference name: Proceedings of SPIE, Three-Dimensional Imaging, Visualization, and Display 2011 Date of Conference: 27–28 April 2011 The class of two-dimensional non-separable linear canonical transforms is the most general family of linear canonical transforms, which are important in both signal/image processing and optics. Application areas include noise filtering, image encryption, design and analysis of ABCD systems, etc. To facilitate these applications, one need to obtain a digital computation method and a fast algorithm to calculate the input-output relationships of these transforms. We derive an algorithm of NlogN time, N being the space-bandwidth product. The algorithm controls the space-bandwidth products, to achieve information theoretically sufficient, but not redundant, sampling required for the reconstruction of the underlying continuous functions. © 2011 SPIE.

We propose a technique for data detection in a two-dimensional page-access optical memory. The technique combines sequence detection by the use of the Viterbi algorithm with decision feedback to improve the bit-error-rate performance in a system corrupted by intersymbol interference. It has an advantage in that it can be operated on a row-by-row basis as data are output from the optical detector. Use of the proposed scheme might ease the design tolerances of the optical components or permit the use of large data pages.

We discuss wavelength selection for true-color holography by investigating the sampling nature of the holographic process. During holographic recording the chosen wavelengths point sample the surfacereflectance functions of the objects in a scene. To understand the effect of this sampling on color perception, we study the tristimulus values of points in the reconstructed hologram. The sampling results in the holographic process being mathematically equivalent to integral approximations for the tristimulus integrals. By selecting efficient approximations, we infer wavelengths to use in color holography. Our analysis not only suggests wavelengths for the usual three-color holography but also suggests the use of four or more wavelengths to improve color reproduction in holography.

Two-dimensional velocity or displacement fields that are recorded as double-exposure speckle patterns may be measured with an anamorphic optical processor. The anamorphic optical processor measures one component of the velocity or displacement throughout a linear region of the double-exposure speckle pattern. The signal in the output plane of such a processor is a fringe pattern. An analysis to predict fringe modulation based on Fourier optics and the statistics of speckle patterns is developed. The analysis specifies the effects of both the speckle-recording optics and the anamorphic optical processor on the fringe modulation. The observed loss of modulation when the velocity or displacement component perpendicular to the measured component is increased is also described. Measurements of fringe modulations that are produced by anamorphic optical processors with and without increased tolerance to the perpendicular velocity component are compared to results of the analysis. Fringe modulation versus relative exposure in the double-exposure speckle pattern are also measured and compared to the results of this analysis. An anamorphic processor that reduces the time for digital processing of the fringe patterns by a factor of N (typically 128, 256, or 512) relative to the two-dimensional Fourier transform optical processor (with identical spatial resolution) is demonstrated.

We present a practical real-time optical pre-processor intended to enhance small defects in a smooth surface. The heart of the system is a photorefractive BSO phase conjugate mirror which reflects only the low intensity features of the object’s optical Fourier Transform. By adjusting the beam ratios so that only the low intensity, high spatial frequency image components are phase conjugated and inverse transformed, an image consisting of just the defects is produced. To our knowledge, this is the first use of this technique on opaque and non-periodic objects. We present experimental data showing enhancement of defects smaller than 0.2 μm.

This paper addresses the problem of visualizing 3-D scalar data, initially represented as an ordered set of digital images stacked parallel to each other. An observer’s ability to perceive the geometry of the structures in these data fields depends on the methods of reconstructing and displaying 3-D representations. We describe three computer-based visualization methods that share the common goal of displaying the interior structures of 3-D data, and we present the results of applying these methods to a set of fluid-flow data. Interactive peeling of smooth opaque contour surfaces is the best of the three methods: it gives excellent perception cues.

The geometrical design characteristics of multiple-image holograms are evaluated. A figure of merit expressing these characteristics as a function of the hologram diameter and the distance between the hologram and the image plane is developed. This value is then used to compare two designs which are capable of forming several hundred interconnections. The results indicate that these connections can be formed between points on the substrate separated by 2-3 cm provided that the holograms are separated from the substrate plane by 0.5-1 cm. Each hologram design is experimentally demonstrated in bleached photographic emulsions.

We report a fast and accurate algorithm for numerical computation of two-dimensional non-separable linear canonical transforms (2D-NS-LCTs). Also known as quadratic-phase integrals, this class of integral transforms represents a broad class of optical systems including Fresnel propagation in free space, propagation in graded-index media, passage through thin lenses, and arbitrary concatenations of any number of these, including anamorphic/astigmatic/non-orthogonal cases. The general two-dimensional non-separable case poses several challenges which do not exist in the one-dimensional case and the separable two-dimensional case. The algorithm takes approximately N log N time, where N is the two-dimensional space-bandwidth product of the signal. Our method properly tracks and controls the space-bandwidth products in two dimensions, in order to achieve information theoretically sufficient, but not wastefully redundant, sampling required for the reconstruction of the underlying continuous functions at any stage of the algorithm. Additionally, we provide an alternative definition of general 2D-NS-LCTs that shows its kernel explicitly in terms of its ten parameters, and relate these parameters bidirectionally to conventional ABCD matrix parameters.

A systematic comparison of the accuracies of scalar diffraction integral and angular spectrum method with respect to FDTD are done. Validity regions of the methods are derived and optimal method for each region is determined.