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A novel method of phase-detection in the infrared is proposed to enhance the sensitivity and dynamic range of a single-wavelength surface plasmon resonance biosensor. A structure is also proposed to prevent the sensitivity degradation.

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.

An aspherical-meniscus and air-spaced-spherics are identified as minimum aberration configurations for page-based holographic recordings. Air-spaced-apsherics attain imaging NA’s of 0.7 for holographic recording only, and of 0.45 for a combination of holographic and surface recording.

A unique C-aperture metallic waveguide with a 90° bend and tapered region having applications to HAMR is presented. The structure has a small footprint and yet shows high throughput and a small spot size.

High NA (0.7 ~ 0.8) objective lens in which both object and pupil aberrations are compensated for are designed in two-element configurations, and are usable for a combination of holographic and surface recordings.

We present a design of a linear optical waveguide that utilizes a C-shaped metallic nano-aperture that efficiently transports light while maintaining a spot size of lambda/10. The performance of a C-aperture waveguide is superior to both a regular ridge waveguide and other surface plasmon based metal nano-optical waveguides. The energy transport mechanisms are explained by the coupling of an aperture surface resonance and the thickness resonances inside the guide channel. Finite-difference time-domain simulations of gold C-aperture waveguides are performed for a 1.5 microm wavelength incident plane wave. The 1/e decay length in power transmission is predicted to be approximately 2.5 microm. The total power throughput is 1.66 for the 2.55 microm long guide, with an intensity 6 times that of the incident wave at a distance 120 nm from the exit plane, having a spot size of 150 nm.

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.

near-field optical data storage. Also, data transfer rates canbegreatly increased iftheVCSELsareapplied inparallel arrays[11. Previous workonnanoaperture VCSELsutilize conventional circular apertures whichsuffer fromlowpoweroutput through thenanoaperture whentheaperture size becomes muchsmaller thanonewavelength[23]. We propose toapply aunique C-shaped nano-aperture (C-aperture) ontoVCSELs.Fromsimulation, theC-aperture showsthree orders of magnitude higher powertransmission efficiency thanaconventional square orcircular aperture producing thesame near-field spotsize[41. We report herearecord-high near-field intensity of15.4mW/[tm2 achieved fromournanoaperture VCSELwitha70nmC-aperture. Ourtop-emitting VCSELsaredesigned tooperate around 970nmandconsist of9.5pairs ofp-type distributed Bragg reflectors (DBR),three strain-compensated InGaAs/GaAsP quantumwellsand38.5pairs ofn-DBRs.The reflectivity ofthetopmirror isenhanced witha150nmthick Aucoating. We insert ahalf-wavelength thick SiO2 filmbetween theAucoating andthetopDBR pairs toenhance thetransmission through thenano-aperture. We use wetoxidation ofAlGaAstoobtain a2.8pim-diameter oxide aperture forcurrent andmodeconfinement. Thenanoapertures areetched through theAucoating using aFocused IonBeam(FIB). Thetransmission oflight through theC-aperture ispolarization-dependent. Forthematched polarization, theCaperture produces awell-confined near-field spotwithhighintensity. However, fortheorthogonal mismatched polarization, theresulted near-field spotispoorly confined andtheintensity istwoorders ofmagnitude lower. Since VCSELsnormally havetwodegenerate orthogonal polarization states, weneedtocontrol thepolarization ofthe VCSELsinorder toapply theC-aperture ontheVCSELs.We openfour50*1500nm slits surrounding a70nmCaperture intheAu coating using FIBtocontrol thepolarization. Sincethetransmission oflight polarized perpendicular totheslit ismuchhigher thanthatoflight polarized parallel totheslit, thepolarization ofthe VCSELsiseffectively controlled tobeparallel totheslit duetolower loss inthis direction. Toidentify howmuchnetpowercomesoutoftheC-aperture, weblock thelight transmitted through theslits by depositing 150nmthick Pttofill theslits using electron-beam assisted chemical vapordeposition onaFIB/SEM dual-beam system. Pthasreflectivity of73%at1ptm, compared withreflectivity of95%forAu.Sothepolarization selectivity bytheslits ismaintained after theslits arefilled withPt.We measured thepolarization-resolved power

Tilt tolerance of media is compared for bit-based and page-based holographic storage systems having an equal diffraction efficiency per bit detector, dynamic range of the medium, and surface recording density. We have formalized the diffraction efficiency degradation caused by aberrations of a reconstructing reference beam induced by tilt of the medium, using a coupled wave theory in the Fourier domain. The bit-based holographic storage system has a larger media tilt tolerance compared with a page-based system with relatively large page size.

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.

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.

We present a C-shaped nano-aperture-enhanced Ge photodetector that shows 2~5 times photocurrent enhancement over that from a square aperture of the same area at 1310 nm. We demonstrate the polarization dependence of C aperture photodetector.

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.

This paper discusses recent advances in the understanding of holographic data storage in photorefractive SBN. The implications of electrical fixing procedures on the storage architecture will be treated by using a systems approach.

We recently discovered that C-shaped sub-wavelength (nano) metallic apertures when irradiated at specific resonance frequencies have extraordinary power transmission five to six orders of magnitude beyond what is observed for conventional round or square apertures. These apertures produce optical spot sizes as small as 25-50 nm using visible light in the near-field of the aperture with a brightness 10-100 times higher than that of the illuminating beam. A proper understanding into this remarkable phenomenon can aid in the development and understanding of a multitude of applications of these apertures including dense data storage, particle manipulation, and nano-scale photonic devices. Current scalar visualization approaches typically are insufficient to significantly aid in the understanding of these complex near-field optical problems. For example, two common approaches involving either visualization of scalar electromagnetic wave amplitudes in 2-D or rudimentary arrow plots of the vector fields produced in Finite-Difference-Time- Domain simulations are clearly inadequate. Both techniques provide only partial insight into the problem, as only specific planes can be visualized and therefore the global structure of the fields cannot be readily inferred. Understanding of the three-dimensional electromagnetic vector fields and energy flows related to the illumination of nano-sized apertures is critically important in near-field applications, as simple scalar analysis is not suitable at these small dimensions [8]. An ideal visualization tool that has not been used before in studying the optical behavior of near-field apertures is three-dimensional vector field topology. The global view of the vector field structure is deduced by locating singularities (critical points) within the field and augmenting these points with nearby streamlines. We have used for the first time, to the best of our knowledge, three-dimensional topology to analyze the topological differences between a resonant C-shaped nano-aperture and various non-resonant conventional apertures. The topological differences between these apertures are related to the superiority in power throughput of the C-aperture versus conventional round and square sub-wavelength apertures. We demonstrate how topological visualization techniques provide significant insight into the energy enhancement mechanism of the C aperture, and also shed light on critical issues related to the interaction between multiple apertures located in close proximity to each other, which gives rise to cross-talk, for example as a function of distance. Topological techniques allow us to develop design rules for the geometry of these apertures and their desired spot sizes and brightness. The performance of various sub-wavelength apertures can also be compared quantitatively based on their topology. Since topological methods are generically applicable to tensor and vector fields, our approach can be readily extended to provide insight into the broader category of Finite-Difference-Time-Domain nano-photonics and nano-science problems.

By using the direct-write e-beam technique with liquid phase epitaxy LiNbO3 thin films, we have successfully produced sub-micron domain structures for achieving dynamically switchable filters in a periodically poled lithium niobate (PPLN) waveguide. The effects of direct-write e - beam parameters are investigated to achieve sub-micron periodic domain structures in homoepitaxial liquid phase epitaxy (LPE) LiNbO3 thin films. More regular structures appear at acceleration voltages higher than 20 kV and areal dose range 350 μC / cm2 ~ 450 μC / cm2 with lower scanning speeds. Under these optimal conditions, an approximately 500 μm-long grating of a 1.1 μm period, consisting ~ 180 nm domains is achieved.

We demonstrate 12-layer storage of 5.84 Gbits per square inch via micro-holograms written and read at 0.532 nm from a 125 micron photopolymer disk continuously rotating at 3600 RPM. Scaling predicts a potential TByte capacity.

We propose and demonstrate multi-layer storage in holographic photopolymer by locally altering the reflectivity of a factory-written reflection hologram at the focus of a single objective lens. Linear, two-photon and thermal writing mechanisms are demonstrated.

The transmission and photocurrent of a multiple‐quantum‐well optically addressed spatial light modulator are measured to study the screening dynamics of the internal electric field under uniform illumination. The response is modeled with a numerical device simulator which solves the conventional drift‐diffusion transport equations. Evidence is found for bipolar transport, and the photocurrent response at low internal fields is shown to decay due to the transit time of carriers across the quantum well region. For large internal fields the photocurrent response saturates and the corresponding screening rate is estimated using an analytical device model.

Results on the use of C-shaped nano-apertures for optical data storage are reported. This type of aperture have a highly concentrated nanometer sized spot with a power throughput 1,000,000 times higher than for a square or round aperture producing the same spot size. Optical recording using contact media and conventional optical read-write media in DVD technology is also described.

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.

C-shaped apertures in a metal film, were made to be resonant at visible wavelengths. They showed transmission enhancement of 22 times over a square aperture of the same area. This resonance was tuned over 70 nm

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.

Optical resolution beyond the diffraction limit can be achieved by use of a metallic nanoaperture in a near-field optical system. Conventional nanoapertures have very low power throughput. Using a numerical finite-difference time domain method, we discovered a unique C-shaped aperture that provides approximately 3 orders of magnitude more power throughput than a conventional square aperture with a similar near-field spot size of approximately 0.1 lambda. Microwave experiments at 6 GHz quantitatively confirmed the simulated transmission enhancement. The high transmission of the C-aperture--or one of the related shapes--is linked to both a propagation mode in the aperture and local surface plasmons.

In this article, we propose and demonstrate a novel holographic optical disk storage system based on polarization-collinear holography. This method will enable us to construct a small volumetric optical disk storage system with CD and DVD upper compatibility.

Water-assisted micromachining of silicon with ultra-short laser pulses is investigated.We show that water confinement provides enhanced ablation rate, improved ablation profile, and less debris re-deposition as compared to ablation in air. Theoretical modeling of laser-matter interaction in water-confined silicon ablation and experimental results with femtosecond laser pulses are presented.

We demonstrate periodic domain engineering using a direct-write electron beam poling technique in Z--oriented liquid phase epitaxy LiNbO3 films grown on LiNbO3 and LiTaO3 substrates for waveguide applications. Submicron domains (~500 nm) are experimentally observed.

We performed a parametric study to suppress secondary phases in lithium niobate thin films by using pulsed laser deposition (PLD). A KrF excimer laser (λ=248nm) was used as a PLD source and c-oriented sapphire was used as substrates, for waveguide applications. By reducing the growth rate and changing the ambient gas pressure respectively, we found that the main parameter suppressing a secondary phase is controlling the plume strength. To investigate 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 and Li-deficient phase mixed films are compared and related to the growth mechanism with a lattice misfit. Deposition parameters to achieve lower loss films are also discussed.

We report the growth of epitaxial SrxBa1−xNb2O6 (SBN) thin films by pulsed laser deposition. The films were grown on (100) MgO substrates with thicknesses in the range 200–400 nm. Rutherford backscattering analysis showed that the films have stoichiometric composition identical to the target material. X‐ray diffraction 2θ scans indicate single crystalline layers with the (001) orientation perpendicular to the substrate plane. Phi scans on the (221) plane, however, reveal that the films have two in‐plane orientations. The unit cell of SBN is rotated in the plane of the film by ±18.4° with respect to the MgO substrate unit cell. This rotation is explained using a model which takes into account both the lattice match and the electrostatic energy within the heteroepitaxial interface.

In this paper, we review the state-of-the-art in holographic data storage, with particular emphasis on the interplay between materials and systems issues. In a generic configuration, a reference and object beam are incident on a recording medium. Electronic digital bit streams are impressed onto a laser beam via a spatial light modulator (SLM) in the form of 2-D digital bit patterns or pages. Multiple pages are superimposed in a stack by angular, phase or wavelength encoding in the Fourier domain. The total recording volume is addressed by scanning both writing beams across the surface of the storage medium. Readout in each stack is achieved by capturing the reconstructed bit pattern on a CCD or other suitable detector array. The medium may consist of a monolithic single crystal or a mozaic of fibers ordered in a regular pattern. >

We demonstrate a novel solid-state three-dimensional display using rare earth doped heavy metal fluoride glass as the active medium. In this device, two laser beams intersect inside a bulk glass at room temperature to address a pixel in three-dimensional space. The two-step resonant upconversion process requires two different infrared wavelengths to produce visible radiation. In this manner, a pixel can be addressed only at the intersection of the two laser beams. By scanning the intersection of these beams inside the display material, true three-dimensional figures can be drawn. For practical applications with high bit densities and low power pump lasers, high upconversion efficiency is necessary. Recent work on upconversion in fluoride glasses, motivated by fiber amplifier and short wavelength laser development, has identified fluoride glass hosts and rare earth dopants as systems that have high radiative recombination rates and high upconversion efficiencies. In this presentation we demonstrate three-dimensional displays in both trivalent praseodymium (Pr/sup 3+/:ZBLAN) and in trivalent thulium (Tm/sup 3+/:ZBLAN) doped bulk fluoride glass. >

A number of spatially nonlinear-optical materials, such as photorefractive media, are suitable for volume holography. High Bragg selectivity of thick media has led to the development of applications of multiplex volume holography ranging from binary and analog data storage, to associative memory, to neural networks, to optical interconnects. An important consideration is the balance between capacity and noise. We examine here crosstalk for angular, phase-encoded, and wavelength multiplexing for holographic data storage and describe the properties of null-matched arrangement of reference waves, presenting new results for adjacent, sparse, and fractal strategies. We emphasize the impact of signal bandwidth on crosstalk and describe how crosstalk limits storage capacity. We consider first crosstalk due to Bragg mismatch (mismatch-limited crosstalk), and then relate it to other noise sources present in a holographic memory system. >

Certain memory applications based on photorefractive media require the ability to conveniently fix holograms. An attractive alternative is to sufficiently prolong the readout time. Low photoexcitation at long wavelength augmented by self-diffraction can increase readout time by a few orders of magnitude. The interaction of the writing and readout waves, both of the same wavelength, with the photorefractive space charge field has been investigated theoretically and experimentally. Dynamics of beam coupling and self diffraction, in certain geometries, can lead to an initial increase followed by non-exponential decay of the diffracted signal during readout. Here we study how the difference in gain, lifetime, photoexcitation and absorption at different wavelengths - which require changing incident angles to satisfy the Bragg condition - affect the decay dynamics of photorefractive gratings. >

Digital holographic data storage fundamentally differs from bit-wise surface recording techniques by storing the transform of a two-dimensional array of bits throughout the volume of a recording medium. Upon readout the data are transformed and detected by a 2-D detector array, providing massively parallel data streams. The third dimension of the recording medium provides an additional degree of freedom to increase capacity per unit surface area. Data storage densities exceeding those of conventional optical and magnetic recording devices by up to ten times (200 bits/cm/sup 2/) have been achieved. These densities allow 200 GB of information to be stored on a single sided 5.25" disk. By reading out 2-D arrays of bits using an image capturing device, very large data transfer rates can be obtained, up to 1 Gbit/sec. In addition, acousto-optic beam steering devices are capable of addressing each of the stored pages in a few microseconds, providing phenomenally short access times to blocks of data. On the basis of the experimental results and the analysis fundamental issues are elucidated, and conclusions presented concerning the consequences for the various system architectures. Signal processing and coding approaches are discussed for over-coming some of the noise degradations. Tradeoffs between materials and systems performance characteristics are presented to achieve a competitive storage device.

We describe a fully functional, hardware implemented, high data rate (1 Gbit/sec) high capacity digital holographic data storage photopolymer disk system. High density holographic recording is achieved using high-resolution short focal length optics and correlation shift multiplexing. Sustained data transfer rates as high as 10 Gbit/s in optical domain have been achieved.

Volume holographic memory can offer massively parallel associative search capability in addition to high capacity data storage. After holograms have been stored into a photosensitive material, an optical correlation of an input user query against all co-locationally stored patterns can be made simultaneously, resulting in fast search speed. We describe a correlator based on a 90 degree geometry holographic data storage system using thick (/spl sim/l cm) storage media. Two important parameters considered are the correlation error rate and minimum size of the search template. A minimum template area less than 0.05% relative to the whole image area has been demonstrated. Due to the strict Bragg selectivity of volume holograms in thick media, the correlator has very small shift invariance. Thus it lends itself best to the search of relational databases, where information can have a fixed position on the stored record. We describe a demonstration database application designed to make best use of the volume holographic correlator.

In this paper, I discuss a new volumetric recording method capable of achieving ultra-high storage density while leveraging existing surface recording technology, thereby overcoming some of the shortcomings of holographic and layered recording. The three-dimensional recording (3DR) technology uses a novel optical imaging technique to store digital information throughout the third dimension, the depth, of storage media. A grating or plane wave hologram is recorded during a photochemical formatting process of the media in a highly controlled factory environment. Portions of the grating can then be erased during bit writing in the less controlled end-user drive environment with a conventional DVD-type optical stylus. Reading is achieved in the drive by detecting the erased bits with the same optical stylus at reduced laser power.

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.

A new high density integrated‐optical switch design using electrically controlled diffraction gratings formed in the intersection of crossing waveguides is proposed and demonstrated. The gratings are formed, in one implementation, by implanting donor atoms in a periodic pattern. Free carriers from the implanted ions modify the index of refraction resulting in Bragg diffraction between the waveguides. Depletion of the free carriers using a reverse bias voltage switches off the diffraction. High speed switch arrays of 100×100 elements on a single substrate may be feasible. Fabrication and demonstration of a low efficiency proof‐of‐concept switch array in GaAs for use at 1.55 μm are reported. Other designs capable of much higher diffraction efficiencies are described.

In several applications, such as electron beam lithography and X-ray differential phase contrast imaging, there is a need for a free electron source with a current density at least 10 A/cm2 yet can be shaped with a resolution down to 20 nm and pulsed. Additional requirements are that the source must operate in a practical demountable vacuum (>1e-9 Torr) and be reasonably compact. In prior work, a photocathode comprising a film of CsBr on metal film on a sapphire substrate met the requirements except it was bulky because it required a beam (>10 W/cm2) of 257 nm radiation. Here, we describe an approach using a 405 nm laser which is far less bulky. The 405 nm laser, however, is not energetic enough to create color centers in CsBr films. The key to our approach is to bombard the CsBr film with a flood beam of about 1 keV electrons prior to operation. Photoelectron efficiencies in the range of 100–1000 nA/mW were demonstrated with lifetimes exceeding 50 h between electron bombardments. We suspect that the electron bombardment creates intraband color centers whence electrons can be excited by the 405 nm photons into the conduction band and thence into the vacuum.

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.

Summary form only given.Volume holographic recording of information is an attractive solution for the next generation of digital storage, holding promise for systems with high density (/spl ges/10 Gbit/cm/sup 2/), and fast transfer rate (Gbit/sec). The performance of a holographic storage system is principally determined by the recording medium characteristics. Photorefractive crystals had been the most extensively investigated volumetric media, offering good optical quality, and sensitive, but typically volatile, recording. Recently, advances in sufficiently thick photopolymerizable recording media have provided a very attractive alternative for WORM systems. This work evaluates the recording physical properties of photopolymer holographic storage.

Summary form only given.Holographic data storage records information in the form of volumetric gratings within the volume of the recording medium. In digital holographic storage information is typically encoded in the form of data pages, which includes modulation coding, data shuffling, and error correction. Selective properties of volumetric gratings allow for a multitude of holograms to be recorded in virtually the same volume through angular, wavelength, or shift and correlation multiplexing techniques. Potentially high data density and transfer rates (which are due to highly parallel access to the stored data) have been a topic of intense research and development. Short data seek time ( 100 Gbit per 6.5' disk).

Its useful capacity, transfer rate and access time measure the performance of a holographic data storage system (HDSS). Data should never be lost, requiring a corrected bit error rate (BER) of 10-12 to 10-15. To compete successfully in the large storage marketplace, an HDS drive should be cost-competitive with improved performance over other drives. The exception could be certain niche markets, where unique HDS attributes — all-solid-state implementation with extremely short access times or associative retrieval — are attractive or required.

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.