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Trapping and manipulation of micro and nanoparticles are essential functional elements of lab-on-a-chip and micro total analysis systems with applications ranging from single cell analysis, diagnostics, drug discovery, and chemical synthesis. Reliable optical trapping of subwavelength particles is difficult due to the diffraction limited gradient of the optical intensity. Near-field traps have emerged as excellent systems to overcome this bottleneck. Using a periodic arrangement of C-shaped apertures we demonstrate the on-chip manipulation of single sub-wavelength polystyrene beads. The wavelength and polarization sensitivity of these resonant nanostructures is exploited to expose the trapped bead to a time varying near-field force using wavelength and polarization multiplexing schemes. While optical trapping has the advantage of being contactless, dielectrophoresis provides higher forces due to the flexibility of applying larger voltages and field gradients. The RF/Microwave frequency regime where dielectrophoresis operates allows increased polarizability of certain samples due to contribution from orientational, molecular and atomic polarizations as well as particle’s electrical conductivity. Combining the above advantages of both the techniques we discuss photoinduced dielectrophoretic trapping and manipulation of nanoparticles. Using dielectrophoretic trapping we discuss the simultaneous manipulation of beads and droplets as a route for on chip chemical synthesis.

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.

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 demonstrated a record-high-intensity bowtie nano-aperture vertical-cavity surface-emitting laser (VCSEL) with near-field spot size of 65 nm. The bowtie aperture VCSEL is very promising to realize ultradense near-field optical data storage.

The Fourier transform lens consisting of an aspherical element is analyzed in terms of the supportable number of pixels by formalizing an en-squared-power ratio as a function of the Nyquist aperture ratio and aberrations.

The resonance enhanced Goos-Hanchen shifts at attenuated total internal reflection enables the possibility for highly sensitive surface plasmon resonance sensor. The observed giant displacements result from the singular phase retardation at the resonance where the phase is continuous but changes dramatically. The phenomenon is proposed for chemical sensing and the superior sensitivity is demonstrated.

For 45nm lithography and beyond, polarization and other electromagnetic effects such as surface plasmons may begin to affect the transmission through a photomask. Such phenomena are highly polarization sensitive, and may amplify the effects of line-edge roughness (LER) and variations in mask composition. A reduction in the mask material conductivity can mitigate the impact of these effects, but more accurate simulation is required to predict these effects well.

We designed and demonstrated a unique C-shaped nanoaperture (C-aperture) Vertical-Cavity Surface-Emitting Laser with an estimated maximum net power of 113 μW coming from a 70nm C-aperture. Simulation shows the near-field FWHM spot size at 30nm away from the C-aperture is 94nm and 108nm in X and Y direction. We estimate the peak near-field intensity from the C-aperture VCSEL to be as high as 13.7mW/μm 2 . This high intensity and small spot size is promising to realize high-density near-field optical data storage.

Small businesses must be extremely efficient and smartly leverage their resources, suppliers, and partners to successfully compete with larger firms. A successful small business requires a set of companies with interlocking business relationships that are dynamic and needs-based. There has been no software solution that creates a secure and flexible way to efficiently connect small business computer-based employees and partners. In this invited paper, we discuss MioNet, a secure and powerful data management platform which may provide millions of small businesses with a virtual workplace and help them to succeed.

A new holographic data storage material is currently being developed at General Electric. This material is based on a thermoplastic host doped with dyes with narrowband absorption resonances. The dye is photosensitive and irreversibly bleaches under exposure to light. The reduction in concentration of the dye in the host after exposure induces refractive index variations at wavelengths away from the dye absorption peak according to the well-known Kramers-Kronig relationship. The approach proposed here requires different recording and readout wavelengths to prevent data erasure during readout. Samples were produced using different dyes and various concentrations in a polycarbonate host. The extensive experience developed in th e past with polycarbonate for optical media promises to make the proposed material very inexpensive. These samples were characterized using holographic techniques as well as using spectroscopic transmission and ellipsometry. The results of the characterizations indicate that this material approach can offer very large dynamic range, but have thus far shown very low sensitivity. Further work is required to demonstrate materials having both sufficient dynamic range and sensitivity for holographic storage applications. We believe that if this condition can be satisfied, this new material approach will be an excellent candidate for high-density holographic media for content distribution. Keywords: holographic data storage, narrow-band material, dye-doped polycarbonate

We present theoretical calculations and experimental measurements of silicon micromachining rates, efficiency of laser pulse utilization, and morphology changes under UV nanosecond pulses with intensities ranging from 0.5 GW/cm2 to 150 GW/cm2. Three distinct irradiance regimes are identified based on laser intensity. At low intensity, proper gas dynamics and ablation vapor plume kinetics are taken into account in our theoretical modeling. At medium high intensity, we incorporate the proper plasma dynamics, and predict the effects of the laser generated vapor plasma and the electron hole plasma on the laser-matter interaction. At even higher intensity, we attribute the observed increased ablation rate to energy re-radiation from the laser heated hot plasma, the strong shock wave, and the accompanied strong shock wave heating effects. Experimentally measured data in these regimes agree well with our calculations, without changing parameters in the calculations used for the three regimes. Our results can be applied toward quantitatively characterize the behavior of ablation results under different laser parameters to achieve optimal results for micromachining of slots and vias on silicon wafers.

From the ultraviolet induced absorption, we have found a broad blue band and little involvement of Pr ions in ultraviolet illumination. Ultraviolet excited photoluminescence and the excitation spectra for visible emission were also measured in Pr:LiNbO3. We estimated photovoltaic constant and photoconductivity by measuring photovoltaic current and voltage with different boundary conditions. With ultraviolet gated short-circuit holographic recording, we have measured enhanced sensitivity and diffraction efficiency.

We discuss the design considerations of Internet Assisted Laboratories (Ilabs), their educational use for teachers and students in the classroom and for homework, and the results of several pedagogical evaluations at Stanford University of remote optics Ilabs we have used since 1998.

Very Small Aperture Laser (VSAL) system is a near field optical data storage system that utilizes a nano-aperture fabricated at the front facet of a semiconductor laser to define a nano-sized spot and hence to achieve ultra-high density storage. However, these nano-apertures typically have very poor power throughput behavior when the sizes of the apertures are much smaller than the wavelength of the incident light. In this paper, we use numerical simulation tool XFDTD, which is a three-dimensional vector electro-magnetic field simulator based on the finite difference time domain (FDTD) method, to study the behavior of the nano-apertures. We show that for square apertures, the power throughput decays as r4 (r is the size of the aperture) when the aperture size r is less than lamda/4 (lamda is the incident light wavelength). To solve the power throughput shortage problem, we present our novel nano-aperture design -'C'-aperture. Compared with a conventional 100nm square aperture, the 'C'-aperture provides 1000x higher power throughput while maintaining a comparable near field spot size. We show that the greatly enhanced power throughput is due to both the polarization and resonance effects.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Doped stoichiometric LiNbO 3 (SLN) crystals show more advantages over traditional congruent LiNbO 3 (CLN). This paper is focused on the measurement of the holographic performances of doped SLN crystals, including the sensitivity, dynamic range, and angular selectivity. The principles and methods for the measurements are first described, with more attention paid to the measurement of erasure time constants. The results show that the SLN crystal co-doped with Ce and Mn has the largest dynamic range, owing to the extremely long erasure time constants even by the multiplexing method. The SLN crystal co-doped with Tb and Fe and reduced in rich nitrogen atmosphere has the fastest response time and highest sensitivity. The oxidized and as-grown SLN crystals co-doped with Tb and Fe exhibit photochromic effect under UV illumination. With UV pre-illumination these crystals have sensitivity competitive to the heavily Fe doped CLN. The measured selective angles for most of the SLN samples of proper optical quality agree well with the theoretical calculation.

We report enhanced photorefractive sensitivity in Mn, Ce doped LiNbO3 at 514 nm and 633 nm under ultraviolet illumination at 365 nm. Without ultraviolet sensitization, the crystal showed very weak diffraction efficiency and self-erased behavior. The accumulation of charged states by ultraviolet light is observed even after the hologram is erased because of the asymmetric process of recording and reading. The concentrations of doped ions and the intensity ratio of ultraviolet and recording light are important factors to improve sensitivity in this material.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Computers have enabled the generation and acquisition of large vector and tensor data-sets. Reynolds numbers, and in data acquisition producing large data-set such as weather and ocean current databases. However, techniques for automated searching and comparison of large vector and tensor data-sets have been lacking. Many of the techniques are based on visual comparisons which do not have the quantitative rigor required for automated comparisons. Other methods which use data based comparisons require a common domain, grid alignment, and interpolation often making data- sets acquired from different sources difficult to compare. This paper provides comparison methods that are based on the topology of the vector field. These methods can be used for both 2D and 3D fields, and depending upon the complexity of the field, different levels of comparisons can be utilized to reduce search times. Topology based methods have the added benefits of describing a field that is independent of the grid, and that is based solely on topological components which have a significant compression over the original field.

The physical properties of photopolymer grating formation are, for the first time, investigated elaborately with respect to I, and (Lambda) . The dynamics of holographic recording with constant exposure energy (15mJ/cm2), are evaluated for a wide range of different I (mW/cm2 - W/cm2), and for a few typical (Lambda) (0.5 - 3.5 micrometer), in a material utilizing cationing-ring-opening polymerization (Polaroid CROP ULSH-500B). Diffusion was evaluated to limit the photo- initiated recording sensitivity at high I(greater than W/cm2 approximately (Lambda) -2). At the same time, however, the significant post-exposure grating development observed for diffusion limited recordings, was identified to allow eventually for equally high sensitive final gratings (approximately 3 - 5 cm/mJ) without reciprocity, or diffusion limitations. Based on these observations, a new physical model was developed that describes more accurately holographic recording utilizing photo-initiated polymerization, and accounts successfully for the observed physical properties of grating formation.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We evaluate the physical properties of volume holographic recording in photopolymer that allow for high performance nonvolatile digital data storage. We identified efficient volume grating formation for photoinitiated cationic-ring- opening polymerization that utilizes unrestricted monomer diffusive transport contributions in the grating development process during and after exposure.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Volume holographic recording of information is an attractive solution for the next generation of digital storage systems, for the ability to optically record and retrieve, independently, multiple superimposed holograms, transferring in parallel the corresponding page-formated digital data representations. Due to these two unique properties, a holographic digital data storage (HDDS) system holds promise for high capacity density (Tb/cm 3 ), and fast transfer rate (Gb/sec) [1]. During holographic recording, information is stored as refractive index modulation, i.e. volume phase gratings, resulting from the interference of the information-bearing and reference laser beams within the volume of the holographic recording medium. The performance of a holographic storage system is principally determined by the physical characteristics of the recording medium [2]. Photorefractives have been the most extensively investigated materials utilized in holographic storage. Recently, advancements in sufficiently thick photopolymer holographic media have provided a promising alternative for WORM systems [3, 4]. In these materials, formation of compositional volume phase gratings through a photoinitiated polymerization process provides an attractive recording mechanism which allows for relatively large permanent refractive index modulation with high recording sensitivity, that compares favorably to, typically volatile, recording in photorefractives [4, 5, 6]. Limitations in the response of these materials, however, may arise during and after exposure, limiting the sensitivity, the final grating strength, and the digital system performance. In this presentation, we evaluate the physical properties that allow for efficient volume holographic recording utilizing photoinitiated polymerization grating formation. The previous studies of photoinitiated polymerization recording, in materials utilizing a free-radical [4], or a cationing-ring-opening (crop) [7] process, have suggested limited grating strength to arise due to reciprocity failure at high intensity, and at large grating spacing recordings. Grating formation has further been described through a photoinduced reaction diffusion model that ignores postexposure polymerization (dark reaction), and introduces diffusion limited response for multiple recordings [4]. In this presentation, we evaluate photopolymer recording in a unified framework based on the polymerization (τ p ) and the diffusion (τ d = Λ 2 /D) time scales that completely characterize the principal physical processes during grating formation [8]. We investigated elaborately holographic recording in a material utilizing cationing-ring-opening polymerization (crop Polaroid samples).

The performance of holographic storage in photopolymer recording media gets limited by compositional volume grating distortions, arising primarily due to postrecording anisotropic medium dimension changes. We evaluate the polymer grating distortions, and the corresponding diffraction efficiency fluctuations, as noise in the holographic digital system. The analysis suggests the importance of the distortion induced grating strength fluctuations relative to optical scattering from the system performance, and encoding, characteristics at different grating distortion regimes.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

By reading data in an angular multiplexed holographic storage system at a wavelength other than the wavelength used for writing, the problem of unwanted erasure can be prevented. By compensating data prior to recording, the mismatch resulting from the difference in reading and writing wavelengths may be minimized. Such a compensation technique was experimentally investigated by recording differentially encoded data within an Fe doped sample of LiNbO3 at a wavelength of 514 nm and recalling data using 488 nm. Our system demonstrated that the recording of compensated data allowed accurate readout with a raw bit error rate of .08%.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We investigated compositional volume grating formation in the Polaroid medium that utilizes the cationic-ring-opening photoinitiated polymerization process, and compared our conclusions with the current physical model describing polymer holographic recording. We identified the effects of diffusion and polymerization during illumination, as well as significant postexposure grating development. Holographic recording in this medium allows for final strong gratings with high recording sensitivity (S approximately 2 cm/mJ), that were not limited at the higher recording intensities (I less than or equal to 250 mW/cm2) corresponding to photon (exposure) limited recording. The results of the present analysis allow for more comprehensive physical description of grating formation in the photoinitiated CROP process, and evaluation of the polymer recording process in a nonvolatile holographic storage system.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ce doped and undoped SrxBa1-xNb2O6 (SBN) fibers grown by the laser heated pedestal growth (LHPG) technique in Stanford University were investigated by 2D scanning electron microprobe analysis. The SBN fibers grown along c [001] or a [100] axes often show radially distributed optical inhomogeneities (core effects) of varying magnitude. Ba enrichment and Sr reduction were primarily detected in the core which can be qualitatively described by a complex-segregation effect. This defect structure as a complex-congruency related phenomenon modified by the composition-control mechanism of LHPG system. Its radial dependence of effective segregation coefficient is described by the modified Burton-Prim- Slichter equation.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A volume photorefractive optical memory architecture can be integrated into 2D arrays of reconfigurable optical interconnect pixels for high performance digital processing applications such as high speed telecommunications and computing. This volume memory array will ultimately be implemented into a high performance optical computing module architecture. These modules use planar diffractive optical interconnect elements where fixed programs are stored. The insertion of volume photorefractive optical interconnect element technology will provide wavelength selective interconnect reconfigurability at system clock speeds (or faster). Target switching speeds of 1 ns may be achieved by electrical tuning of a multisection distributed Bragg reflection edge or a vertical cavity surface emitting laser diode. This photonic random optical memory access system is referred to as `PROMAC'.

Holograms may be superimposed in a holographic medium by a number of techniques such as angular, phase-encoded, and wavelength multiplexing. For typical architectures, crosstalk increases as the bandwidth of stored data increases. The number of superimposed holograms in an ideal medium is limited by its length L, the wavelength of light (lambda) , and index of refraction n, such that for crosstalk-limited storage we can superimpose up to 2nL/(lambda) holograms of high bandwidth. In practice, however, the properties of real materials depart from the ideal through index inhomogeneities and scattering centers, dispersion in the material response as a function of grating spatial frequency, and dispersion as a function of the wavevector and polarization of both incident and scattered light. We discuss the impact of these properties on holographic data storage and describe material, device, and system strategies designed to minimize these effects.

Color holography is typically achieved through the use of three wavelengths during the imaging. However, three-color holography is sufficient only when one has the freedom to select locally the proportions of the primaries during reconstruction. This freedom exists in some, but not all, holographic techniques; we discuss wavelength selection in light of this distinction. For holograms that do not allow for local control of color, such as display holography, the color contributions depend on the surface reflectances in the scene; the monochromatic sources point sample these reflectances. From this sampling, we show that the problem of wavelength selection is equivalent to that of finding efficient approximations to the tristimulus integrals. We conclude that three sources are often insufficient for accurate color reproduction, and we suggest wavelengths for holography with three, four, or more wavelengths. For holograms that do allow for local color control, the color science involved is similar to that of raster displays. Therefore, only three primaries are necessary. However, we describe situations where only two primaries are sufficient. This conclusion follows from the dichromatic theory of color reflection, which postulates that often the reflection of light from a surface contains only two color components.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this invited paper we discuss recent advances in holographic data storage using ferroelectric SBN fibers as the recording medium. An optical architecture involving an array of SBN fibers is discussed that potentially allows 2-3 orders of magnitude faster access times than for conventional magnetic data storage devices of Gbyte-size . To realize this potential we are studying the interplay between fundamental materials issues related to fiber growth and photorefractive processes underlying storage and readout processes in SBN.

The capacity of volume holographic data storage depends on the multiplexing efficiency of input holographic data arrays or pages. We compare this page-packing capacity of two common approaches: angle, and wavelength multiplexing. For maximal page packing the angular separation between the reference and signal beam incidence in the angle and wavelength multiplexing methods should be 90 degree(s) and 180 degree(s), respectively. We find that in these optimal arrangements both methods can multiplex a similar number of paraxial data-page signals, which is comparable to conceptual storage capacity limits derived from considerations of resolution in three-dimensions. In practice, the high number of multiplexed data pages predicted here will be compromised by material-related noise sources.

In this paper we discuss recent advances in holographic data storage using ferroelectric SBN as the recording medium. A novel optical architecture involving an array of SBN fibers is discussed that allows 2 - 3 orders of magnitude faster access times than for conventional magnetic data storage devices of Gbyte size. To realize this potential we are studying fundamental materials issues related to SBN fiber growth and photorefractive processes underlying prolonged readout in SBN.

We discuss our recent work on extraction and visualization of topological information in separated fluid flow data sets. As with scene analysis, an abstract representation of a large data set can greatly facilitate the understanding of complex, high-level structures. When studying flow topology, such a representation can be produced by locating and characterizing critical points in the velocity field and generating the associated stream surfaces. In 3D flows, the surface topology serves as the starting point. The 2D tangential velocity field near the surface of the body is examined for critical points. The tangential velocity field is integrated out along the principal directions of certain classes of critical points to produce curves depicting the topology of the flow near the body. The points and curves are linked to form a skeleton representing the 2D vector field topology. This skeleton provides a basis for analyzing the 3D structures associated with the flow separation. The points along the separation curves in the skeleton are used to start tangent curve integrations. Integration origins are successively refined to produce stream surfaces. The map of the global topology is completed by generating those stream surfaces associated with 3D critical points.

There are some "Grand Challenges" of data visualization which scientists in every application domain confront at one time or another. For example, how to access large volumes of data, how to isolate the "important" pieces of information, how to map scientific data to primitives suitable for graphical algorithms, how to achieve the speed of useful interaction, why won't off-the-shelf software do what I need it to do, how to make hardcopy, etc., are just some of the common problems. This panel session addresses issues like these, from the point of view of the scientist who uses visualization as a research tool. Each panelist was invited to submit a short "position paper", which is reproduced here.

A new optical switch design is reported consisting of two sets of parallel channel waveguides intersecting at right angles. Arrays based on Ti:LiNbO3 technology, with waveguide intersections iron doped to provide photorefractive sensitivity, have been fabricated. Interfering guided beams are used to write index gratings at the waveguide intersections, which in turn diffract a portion of an incident signal beam into the crossing waveguide. Arrays ranging from 15 x 15 up to 50 x 50 waveguides are constructed in an active area of 5 mm square. Diffraction efficiency and writing time measurements are reported along with a brief theoretical analysis. A proposal for a practical architecture offering nondestructive readout is described.

Optical implementations of interconnects for digital processors are being inves- tigated for their high bandwidth, large interconnect density and high level of immu- nity from interference. Implementations can be categorized into several classes, in- cluding fiber optics, holographic approaches and integrated optics. Photorefractives appear to be attractive media for interconnects requiring dynamic reconfiguration capabilities. The attractiveness stems from the ability to record large multiple inter- connect patterns on a time scale of milliseconds using modest laser powers, typically of a few mW/cm2. Few of the interconnect architectures that have been explored so far take advantage of the dynamic holographic recording properties of photore- fractives, and key issues related to holographic recording of interconnect patterns in these media still need to be considered. For example, fixing approaches are re- quired to record and store multiple holograms with minimum crosstalk, and update strategies are necessary for modifying or removing interconnect patterns without affecting the others. In this paper we dwell on the pertinent physical characteristics of photorefractives, and discuss implications for optical interconnects. For example, we present a procedure for prolonged readout, an architecture for Bragg matched diffraction with light of a different wavelength than is used for recording, a novel approach to a large recording medium consisting of an SBN fiber bundle, and a very high density integrated optical interconnect of 100x100 switches per square centimeter.

The results of a fresh look at holographic data storage in photorefractive materials is reported. This work concludes that advances in photorefractive material, particularly SBN, AO deflector technology, CCD technology, and laser technology could make a very interesting low latency mass storage device possible. Two advances in this technology, a technique for a highly asymmetric write/read cycle and a method for building artificial crystal shcipes, are described.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper provides a review of non-holographic display devices. Pertinent aspects of the human visual system are briefly discussed in relation to the design of devices for display of three-dimensional data. Several technologies which have now reached relative maturity are discussed. A broad scope of applications strongly drives new developments, and the present state-of-the-art is considered.

Instantaneous three-dimensional measurements of species concentration in a co-flowing jet are obtained with optical tomography. The processing of 36 interferometric views to obtain measurements with 1.3mm resolution and 5% accuracy is described. Data from one experiment is presented, and merits of two visualizations of the data are compared.

A new approach for visualizing vector data sets was developed by reducing the original vector field to a set of critical points and their connections, and was applied to fluid flow data sets. The critical point representation allows for considerable reduction in the data complexity. The representations are displayed as surfaces which are much simpler than the original data set, yet retain all the pertinent flow topology information. It is suggested that topological representations may be useful for database comparison.

The three-dimensional structure of the flow around a delta wing with tangential leading edge blowing is visualized. The flow is "sliced" by a scanning laser light sheet into a set of two-dimensional cross sections, resulting in a set of three-dimensional data. The light scattered off smoke particles in the flow during a 30 ns laser pulse is imaged onto a high speed camera. The measurement period of a few milliseconds is brief enough to image the flow "instantaneously" (i.e. to within the resolution of the apparatus). The resulting cross sections are digitized and filtered to reduce noise. The STANSURFS software package developed in the Fourier Optics and Optical Diagnostics lab at Stanford is used to threshold the pictures at a prespecified value, stack the thresholded crossections, and reconstruct the three-dimensional flow field at that threshold using cubic B-splines. The resulting structures are displayed in stereo pairs and viewed in three dimensions. Various display techniques including clipping the surface to reveal interior details and rotating the viewer perspective around the structure are used to gain further insight into the three-dimensional nature of this and other flows.

Although the process of computed axial tomography (CAT) yields data from a sample volume, the possibility of fully three-dimensional imaging is not yet exploited by present tomographic systems, which produce a set of planar images. Data from contiguous cross-sectional scans can be combined to provide simultaneous direct three-dimensional visualization of the volume. CT data can be used as an input to several holographic display techniques. We present results of one such technique, the incoherent superposition hologram made from individual planar CT cross-sections. The holographic images are arranged in order corresponding to the method in which they were recorded by the x-ray scanner. Incoherent superposition holography is an additive three-dimensional display, the eye views a volume of data as the sum of light sources from each image. Structure in one plane is less obscured by structure in other planes as compared to coherent holography, of nonholographic displays where light reaching the eye has been attenuated in a multiplicative manner. This type of hologram provides fully three-dimensional depth cues and the ability to focus onto individual cross-sectional images. The recording medium for the incoherent super-position hologram is a silver halide emulsion. The experimental procedure for synthesizing large format holograms is discussed, in particular the method for superimposing holograms that reconstruct images of equal brightness. A method for optimizing this procedure is presented along with the actual incoherent superposition holograms of CT data.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

It is desirable to extend the bene-fits of several new and emerging imag-ing modalities (such as computed tomography and nuclear magnetic reso-nance imaging) by providing means for visualizing an entire volume of image data at the same time. Such advances have been reported previously by us in the area of computer-generated holog-raphy, and in the generation of real-time imagery [1,2,3]. This paper reports on the applica-tion of these developed techniques to several diverse problems, including x-ray imaging of the pelvic girdle, neutron imaging of nuclear fuel rod bundles, and optical imaging of fluid flow in a volume. The particular problems and solutions involved in displaying these types of data are discussed.

The photorefractive materials Bi12Si020(BSO) and its structural isomorph Bi12Ge020 (BGO) have been used as real time holographic materials in a variety of optical storage and information processing applications in the last decade [Ref 1]. Their overall response speed and comparitive ease of crystal growth - and hence availability in relatively large sizes - have frequently made BSO and BGO the materials of choice in these applications despite the supe-rior diffraction efficiencies available with the ferroelectric compounds barium titanate and strontium barium niobate (SBN) [Ref 2]. An understanding of the properties of holographic devices utilizing these materials requires an accurate description of both the holographic formation and read-out processes. The mechanics of the recording process in photorefractive materials, in which photogenerated charge carriers redistribute themselves to form a periodic electric field variation in the medium, have been studied extensively and a number of useful theoretical models now exist [Ref 3, 4]. The holographic read-out process though similarly complex, has been afforded somewhat less attention.© (1986) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Modern scientific data sets require new algorithms and hardware for display and interpretation tasks. We present a discussion of the new display requirements and of techniques currently under developed for this purpose. Special emphasis is placed on holographic and interactive devices. We also present examples of the application of these new techniques to fluid mechanics data.

Dynamic global interconnections between processors in massively parallel computers are a highly desirable feature. Their implementation would greatly increase performance because large bandwidth interprocessor communication links may be reconfigured to match problem geometries. Global hardwiring of interconnects for large processor arrays is cumbersome, and present systems use rather tedious packet routing virtual interconnects. This report presents a novel design concept for a dynamic optical interconnect which would create a holographic interconnect between any two (or more) processors upon request. Each processor has a detector and a light source. A hologram may then be written into a nonlinear crystal which will diffract modulated light from a source at one processor to detectors at any other processors which desire that communication link. Writing is a two step process using a phase conjugate mirror and requiring the light sources of the involved processors to be mutually coherent. Preliminary analysis of this system along with an experimental proof of concept is discussed.

A real-time method to enhance defects in periodic objects is described. Using four-wave mixing techniques, a hologram is nonlinearly recorded in photorefractive BSO so that read-out results in suppression of the periodic structure and enhancement of defects. Experimental results are presented, illustrating detection of defects of size 10 μm x 100 μm. Limitations on the size of defects that can be detected are discussed.