bluuebunny/crossref_metadata_2025 huggingface dataset:
Extended Bandwidth Reflector Designs using Wavelets
Authors: Southwell William H.
Published: February 2023

Quarterwave stacks have for many years been the building blocks of optical interference coating design. Rugates1, introduced in the 1980’s, have the advantage of being without harmonics seen with quarterwave stacks. Recently introduced wavelets2, as shown in Fig. 1, have the additional advantage of being without side lobes as well as being without harmonics.
Experimental Aspects of Rugate Filter Fabrication
Authors: Hall Randolph L.
Published: February 2023

Substantial theoretical work has been done in the area of gradient-index filters since Jacobsson's original paper in 19661-18. In 1982, the term rugate (from the Latin, rugatus meaning wrinkled) filter was coined by the Air Force Materials Directorate to describe a particular class of gradient-index filters, namely multiple, superimposed, sinusiodally varying refractive index profiles. This paper will present various experimental aspects of rugate filter fabrication and show examples of fabricated filters.
Multilayer reflectors with absent higher order reflectance bands—simulation of a rugate reflector
Authors: Baumeister Philip
Published: February 2023

The goal is to produce a reflector whose reflectance peak is centered at a relatively long wavelength λ0. One possibility is a stack is composed of dielectric materials—alternating between a high index B and low index layers A. In general, such a coating manifests harmonic reflectance peaks at shorter wavelengths, λ0/2, λ0/3, λ0/2,… λ0/m, and so on. m is the order number of the reflectance band, which is defined as the number of half wavelengths contained in the basic period. If the ratio of the optical thickness of B to the optical thickness of A is p/q, (where q and p are integers) single (but not adjacent) higher order reflectance peaks are missing, As an example, reflectance bands may be missing at m = 2,4,6,… or at m = 3,6,9,… but not at m = 2,3 and or m = 3,4.
The Dependence of Optical and Spectral Properties of Thin-Layer Interference Structures on the Angle of Incidence of Plane Wave
Authors: Kozar' A.V. , Putrina Ye.V.
Published: February 2023

In the previous research of Thin-layer Interference Structures (TIS) only the normal incidence of the electromagnetic wave on the structures under consideration was studied [1,2]. However, in practice we often meet with oblique incidence of the waves on stratified structures. So in this paper we have studied the dependence of optical and spectral properties of TIS on the angle of incidence of plane wave. This analysis is based on following assumptions: 1. The medium, from which the wave is falling, is homogenous and half infinite. 2. The layers of antireflection coating are homogenous and bounded only in the direction, which is perpendicular to the plane of the structure. 3. The wave is plane and monochromatic. 4. The losses in layers are supposed to be absent.
Analysis of a Multilayer Film with an Absorbing Incidence Medium
Authors: Carniglia C. K.
Published: February 2023

The expressions for the reflectance and transmittance of light from a multilayer thin-film stack are usually derived for a non-absorbing incidence medium.1 This paper presents the results for the case that the incidence medium is absorbing, extending previous results for an interface between non-absorbing media,2 and the multilayer case treated at normal incidence.3
Mechanical characterization of SiO2 evaporated layers
Authors: Nouvelot Luc , Bosmans Richard
Published: February 2023

Mechanical behavior of optical thin films is a field of increasing interest especially when durability of coatings made of hard materials on plastic substrates is concerned. This is typically the case of antireflection coatings on spectacle lenses. Improving mechanical resistance of such systems requires measurement and optimization of the rheological properties of thin films materials, as well as control of the residual stress in the stack. In this paper, we present the stress, hardness and Young modulus measurements performed on SiO2 layers evaporated under different residual gas conditions.
Design of A High Resolution Staring Infrared Sensor for Multiple Gases Based on Fabry-Perot Resonators
Authors: Lopez F. , Meneses J. , de Castro A. J. , Meléndez J. , Bosch S.
Published: February 2023

One of the widest used methods among the non-dispersive IR (NDIR) low-concentration gas sensors is the gas correlation filter. The optical principle uses a gas ampoule, filled with a known concentration of the gas to be measured, which is introduced in the IR light path by means of a rotating wheel. This gives a reference channel. The wheel also contains an identical gas ampoule filled with a non-absorbing gas (N2) to give a signal channel. Simultaneously the light describes a long path through the gas cell containing the gas to be measured. Both channels impinge consecutively on the detector through a narrow band-pass filter.
Compensation of Phase Dispersion in Michelson Type Interferometer
Authors: Lemarquis F. , Pelletier E.
Published: February 2023

We consider the Michelson type interferometer shown in figure 1. The incident beam is split by the first interface encountered. The rear face of the beam-splitter plate as well as the two faces of the compensating plate are coated with an antireflection coating.
Determination of grain size in indium tin oxide films by optical means
Authors: Lehan J.P , Wolfe Jesse D. , Gibbons Kevin , Carniglia C.K.
Published: February 2023

Indium tin oxide (ITO) is a commercially important transparent conductive material commonly used in antistatic and transparent electrode applications. Its optical, electronic and environmental properties are affected by the degree of crystallinity and grain size. Thus determination of the grain size is an important factor in developing a stable, repeatable ITO process. Grain measurement is typically accomplished by x-ray diffraction or electron microscopy. Electron microscopy of ITO films is difficult because electron beam heating of the samples can cause recrystallization. X-ray diffraction is not commonly available to most process engineers and data analysis can be cumbersome if film stress is present. Thus we looked at optical techniques that were compatible with our existing measurements and equipment to determine grain size.
Spectroscopic Ellipsometry with Multichannel Detection: Applications in Real Time Monitoring of Optical Coatings
Authors: Collins R.W. , Kim Sangbo
Published: February 2023

Inhomogeneities in the composition and microstructure as a function of depth in thin film coatings, whether intentional or unintentional, strongly influence their performance in a variety of applications including optical coatings, electrochromics, and photovoltaics. Spectroscopic ellipsometry has proven to be a very useful technique for characterizing such property gradients.1 With ex situ measurements, however, the available data are insufficient to handle continuous gradients with high resolution. In our work, we have solved this problem by collecting ellipsometric data continuously versus wavelength and time during film growth. By applying this real time spectroscopic ellipsometry (RTSE), we have extracted continuous microstructural gradients having complex profiles with ~10 Å depth resolution, at the same time determining the instantaneous deposition rate and the evolution of the surface roughness layer thickness. Although the approach has been first demonstrated for characterizing intentional void volume fraction gradients in the window layers used for thin film photovoltaic devices, it has wider generality in a variety of other thin film coatings applications.
Perpendicular-incidence photometric ellipsometry of biaxial anisotropic thin films
Authors: Zuber Alexander , Jänchen Heidrun , Kaiser Norbert
Published: February 2023

Since the last decade, the application of optical coatings for the ultraviolett (UV) range has increased enormously. Especially mirrors (HR) and antireflecting (AR) coatings with minimal optical losses and long time stability are the optical components of interest. For the depostion of high quality interfence coatings, extensive knowledge of the optical properties and microstructure of the materials is necessary. One frequently used high refractive material down to the UV range is HfO2. Moreover, this material is important for XeCl- and KrF-excimer-laser coatings at 308 nm and 248 nm, respectively /1/.
Calorimetric absorption measurements of substrates and coatings for excimer lasers
Authors: Eva E. , Mann K.
Published: February 2023

Absorption of intense UV-light can cause deterioration of optical components [1]. To investigate the mechanisms involved, sensitive measurements of absolute absorptance are needed. A calorimeter determines the energy dissipated in a sample under irradiation by measuring the temperature rise ΔT, thus it is particularly suited for characterization of dielectic thin films for high power excimer laser applications which may be damaged by absorption heating [2].
Coatings Graded Reflectance Profile - a Review
Authors: Piegari Angela
Published: February 2023

Optical coatings that show a gradually varying performance (reflectance, transmittance, etc.) along the coated surface are known as graded coatings. They are mainly used in the laser field as output couplers of unstable laser resonators [1,2,3]. The replacement of traditional laser mirrors, that have a high reflecting area delimited by sharp edges, with graded reflectance mirrors permits the achievement of diffraction-limited beams of high power or energy. The use of traditional hard-edge mirrors in unstable resonators gives output laser beams having a near-field profile with pronounced ripples due to the diffraction at the mirror edge and a far-field pattern with noticeable side lobes. These shortcomings can be avoided by using output couplers with a graded reflectance profile described by a predefined law, in most cases the reflectance against the radius is represented by a Gaussian or super-Gaussian equation.
Theoretical aspects of rugate filters
Authors: Southwell William H.
Published: February 2023

Rugate filters have seen significant progress in recent years in performance, applications, and fabrication techniques. Underlying this success are some remarkable theoretical principles for gradient-index thin films.
Temperature stability of optical coatings produced by plasma and ion assisted evaporation processes
Authors: Zöller A.
Published: February 2023

The benefits of ion based deposition processes such as ion assisted deposition (IAD), plasma ion-assisted deposition (PIAD), reactive ion plating (RIP), magnetron sputtering and ion beam sputtering have been described in the literature for two decades. One important paper was given by Martin and Netterfield in 1986 [1]. The ability to produce oxide films with high packing density is common for these deposition techniques. The temperature stability of optical coatings, defined by the temperature dependence of the optical performance, depends strongly on the packing density of the individual layers in a multilayer stack. If the film structure is not fully dense, water vapor from the air can penetrate the film. In that case the average refractive index varies with air humidity and ambient temperature. This leads to an vacuum to air shift which is typical for conventional evaporated oxide coatings. The vacuum to air shift of the optical thickness is in the range between 1% to 5 % [1,2,3]. With high packing density films there is no discernible difference between the spectral photometric measurements in vacuum and on air [1,2,3].
Interference Coatings based on Synthesis Silicon Nitride
Authors: Lee Cheng-Chung , Chen Sharu-Lii , Hsu Jin-Cherng , Tien Chuen-Lin
Published: February 2023

Silicon nitride films have very good optical properties and have been investigated by several authors1-8 This paper reports in detail the synthesis of SiNx films by electron beam evaporation of pure silicon accompanied with nitrogen ion bombardment and the results of investigation on composition and optical properties. The application on fabrication of near infrared interference coating has been discussed.
Ion Assisted Deposition of Optical Coatings on cold substrates - a comparison of processes using different ion sources
Authors: Niederwald H. S. , Mertin M. , Schallenberg U. B. , Laux S. , Duparre A. , Kaiser N. , Kennedy M. , Ristau D.
Published: February 2023

Ion- or plasma assisted deposition processes for optical coating applications have been studied for many years. It is well established that they imply superior properties of the coatings, which lead to the application of these technologies in several specialized fields. Until recently, however, IAD has not replaced conventional physical vapor deposition processes on heated substrates in the wide field of optical coatings.
Dense moisture stable titania and silica ion assisted deposited films deposited using a compact cold cathode ion source
Authors: Morton Dale E. , Fridman Vitaly
Published: February 2023

Considerable data has been published on the benefits of ion assisted deposition (IAD) (1,2,3). The cold cathode ion source is a relatively mature device but has generally been regarded as having limited utility in applications requiring large area, uniform ion beams or improving the oxidation of reactive processes and increasing the refractive index of deposited films. A majority of the thin film community did not regard the early versions of the cold cathode ion source as equivalents to the Kaufinan gridded ion sources, end-Hall ion sources, Advanced Plasma Source (APS) or Reactive Low Voltage Ion Plating in producing high-index, moisture stable films.
Realization of High Absorption Achromatic Metal-Dielectric Coatings
Authors: Cathelinaud M. , Torchio P. , Amra C.
Published: February 2023

For an increasing number of applications [1,2], black components must be produced that absorb the whole incident energy with broad-band properties.
Anisotropic antireflection coatings for light at normal incidence
Authors: Hodgkinson Ian , Wu Qi hong
Published: February 2023

A well known antireflection (AR) coating for an air (n
a
)–glass (n
g
) interface and normally incident light is constructed by depositing a quarter-wave of a high index material (nH) followed by a quarter-wave of a low index material (nL).1 In this presentation we expand the scope of the AR coating so that it is antireflecting for one linear polarization which we designate p, but gives a reflectance of a few percent for the mutually perpendicular s polarization. Potential applications of the anisotropic antireflection (AAR) coating2 include polarization-selection devices for lasers, replacing the Brewster-angle plate which requires considerable space in an optical cavity.
Relationship between mixed TiO2-SiO2 films and TiO2/SiO2 interfaces. A combination of spectroscopic ellipsometry and photoemission spectroscopy
Authors: Souche D. , Fisson S. , Nguyen Van V. , Vuye G. , Wang-Leprince Y. , Abelès F. , Rivory J.
Published: February 2023

TiO2-SiO2 mixed oxides are very interesting materials from many points of view: these materials might be of interest as supports for industrial catalysts [1]; they can provide intermediate refractive indices between SiO2 (1.46) and TiO2 (2.4) for optical coatings and are useful in graded-index thin film structures [2]; the addition of SiO2 into TiO2 changes the film structure from polycrystalline to amorphous and decreases optical scatter [3]. In this work, we will emphasize their interest for the characterization of interfaces in TiO2/SiO2 multilayer stacks.
Optical, structural and mechanical properties of lanthanide trifluoride thin film materials for use in the DUV-spectral region
Authors: Thielsch R. , Heber J. , Jakobs S. , Kaiser N. , Duparré A. , Ullmann J.
Published: February 2023

Numerical design and manufacturing of DUV dielectric coatings are strongly influenced by the material properties in this wavelength region. Due to the limited number of DUV transparent materials and due to the lack of a really high index material only a few material combinations are applicable for interference multilayer coatings. Because of their high band gap energy and small absorption, lanthanide trifluorides belong to the only materials to be used in VUV multilayer optics in conjunction with low refractive index materials like MgF2, AlF3, Na3AlF6 (cryolith) or SiO2. LaF3, NdF3 and GdF3 have been chosen for a detailed study in comparison to former investigations on these materials1-3. Thin single films as well as different multilayer coatings (dielectric mirrors, antireflection coatings) have been deposited by a low loss evaporation technology4 developed at IOF.
Fourier transform approach for thin film characterization
Authors: Verly P.G.
Published: February 2023

A Fourier tranform approach was recently proposed by Swart and co-workers for thin film characterization.1 It is based on the observation that the reflectance spectrum of multilayer coatings contains detailed information about the layer thicknesses. When the Fourier transform of the reflectance R is computed in a spectral region where dispersion and losses are negligible, peaks are observed in positions corresponding to the layer interfaces.
Effect of Process Parameters on the Amorphous and the Crystalline Structure of Sn-doped Indium Oxide Films
Authors: Heinz Bernd
Published: February 2023

DC magnetron sputtering is the dominant deposition process for the high volume production of ITO (Indium-Tin-Oxide) thin films. Most of the applications require low resistivity and highly transparent layers. Depending on the process conditions the deposited ITO is either amorphous or crystalline. The major parameters, which influence the structure and the film performance, will be discussed. The emphasis is on conditions, which allow optimizing the optical as well as the electronic performance.
Theory of narrow-band polarizing interference filters
Authors: Ciosek Jerzy
Published: February 2023

Perfect narrow-band polarizing interference filter (NBPIF) reflects radiation in wide spectral range except radiation of selected wavelength and specified linear polarization. In real systems of NBPIF there are the constructions with feature of narrow-band interference filters and thin-film interference polarizers for the single wavelength. These filters may be designed for different spectral range. Then the different optical materials could be used. NBPIF have been described earlier1-3.
Ellipsometric Characterization of Low Pressure Plasma Deposited Au/Fluoropolymer Nanocomposite Films
Authors: Dalacu D. , Martinu L.
Published: February 2023

Composite films composed of a dielectric matrix with imbedded metal nanoparticles are primarily of interest as spectrally selective optical coatings for such applications as photothermal conversion, radiative cooling, infrared furtivity, etc. More recently, they have received attention for their non-linear optical properties.1 Detailed knowledge of the microstructure becomes critical for the latter application as the nanoparticle size and shape (through their effect on the local field) as well as the volume fraction (filling factor) affect the magnitude of the non-linear response. Microstructural characterization of these materials generally involves TEM measurements, which can influence the microstructure through electron beam induced coalescence of the metal grains.2 Alternatively, optical characterization, namely transmission measurements, have been used3,4, but the results are generally qualitative and thickness and filling evaluations need to be made by other methods. It is the purpose of this work to demonstrate the applicability of ellipsometric measurements to characterize fully (film thickness, nanoparticle filling, size and shape) the microstructure of these nanocomposite materials.
Multiscale absorption and scattering mapping (100 μm - 3 μm)
Authors: Commandré M. , Roche P. , Gatto A. , Escoubas L.
Published: February 2023

We have developed an apparatus1,2 allowing precise positioning of the sample and simultaneous mapping of absorptance and scattering on a selected area with different resolutions. Photothermal deflection is used for measuring absorption while a low f-number lens collects part of the pump beam light scattered by the surface. The pump beam is focused on the sample through lenses of various focal lengths. Typically its gaussian beam diameter on the sample surface lies between 3 and 100 μm, according to the desired spatial resolution. By using centering tools and precise optical procedure, the sample positioning is reproducible with a precision of 1 μm. Recurrent mappings of the same area are possible either with the same resolution to study a sample at different stages of its life or with an increasing resolution for more detailed studies3. If thin film thermal properties are homogenous, the spatial resolution of the absorption mapping is about the size of the illuminated area which is therefore the same than that of scattering mapping, that is a value between 3 to 100 μm.
Symmetry properties of solutions in admittance matching method
Authors: Dinca Andreea , Lupei Voicu , Dinca Mihai
Published: February 2023

The admittance matching method is generally used in the design of optical components which require in the same time high reflectance and high transmission bands. The matching is done at one or at both sides of the basic stack by synthesizing a symmetrical three layer periods with an equivalent layer. In order to obtain a broad transmission band, a quasi-matching is necessary around the matching wavelength [1, 2]. In the following, one analyzes some symmetry regularities exhibited by the solutions obtained for two or three periods in the matching stack.
Algorithms for Digital Optical Processors
Authors: Sawchuk A.A. , Jenkins B.K.
Published: February 2023

Recently, several techniques for constructing digital optical processors (DOPs) that perform binary operations have been proposed [1]-[4]. We have recently described and implemented an optical binary sequential logic system that offers a free-interconnection capability very different from that of electronic VLSI [5], [6]. The system is shown schematically in Fig. 1, and consists of a spatially parallel array of optically implemented independent binary gates, and an interconnection unit that optically directs some of the signals on the output side of the gate array back to the input side of the gate array. In the existing system the gate is formed on the active area of a Hughes 45 degree twisted nematic liquid crystal light valve (LCLV). The LCLV is biased so that each gate implements a NOR operation, which is a complete logical set for any combinatorial logic function. In principle, any physical mechanism which provides a fast, large array of independent optical nonlinear threshold elements could serve as the gate array (optical chip).
An Adaptive, Associative Optical Computing Element
Authors: Fisher A. D. , Giles C. L. , Lee John N.
Published: February 2023

An associative memory is essentially a mechanism for storing pairs of information patterns
u¯ and
v¯, so that at a later time presentation of one pattern,
u¯, will result in recall of the other,
v¯. These information patterns are represented here as time-varying vectors,
u¯,
v¯, of n discrete binary or analogue elements. These vectors could encode, for example, pixel intensities from a
n×n 2-D image, strings of characters from a textual database, speech spectral samples, the state variables of a control system, features extracted from a scene, or the output of a robot's sensors. A large number of paradigms have been advanced for implementing associative memory. These1,2 range from purely deterministic matrix multipliers and content-addressable digital memories to holography and randomly interconnected neural network models. The various associative memory schemes offer differing performance capabilities in terms of such measures as1,2 information capacity, the ability to recall
v¯ when presented with only a similar (e.g., partial or distorted) version of the key pattern
u¯, discrimination ability between significantly different u's, information pattern crosstalk, hardware fault-tolerance, pretaught versus adaptive self-organizing capabilties, implementational complexity, and retentiveness/forgeting of old associations. It is sometimes desirable to distinguish an autoassociative memory, where
u¯ recalls itself, from a heteroassociative memory, where
u¯ and
v¯ differ.
A Programmable Optical Processor Based on Symbolic Substitution
Authors: Brenner K.-H. , Stucke G.
Published: February 2023

A new architecture for a programmable optical processor is proposed. It is based on a few simple substitution rules and offers general computing capability.
Optical Systems for Symbolic Substitution
Authors: Mait Joseph N. , Brenner Karl-Heinz
Published: February 2023

Symbolic substitution has been proposed as one means of performing digital computations optically [1,2]. In such a system, information is distributed throughout an assemblage of spatial patterns and is then processed via the transformation of these patterns. For example, the logical AND operator is represented by four transformations: 0 for 00, 0 for 01, 0 for 10, and 1 for 11. In addition, when the data are seen as patterns and the operator as a pattern transformation, spatial coding of patterns follows naturally.
Free Space Optical Interconnects by Cascaded Holographic Elements
Authors: Hossack W.J.
Published: February 2023

Cascaded holographic system for optical coordinate transformations is applied to free space optical interconnect. The design criteria for afocal systems, performing conformal mappings is presented.
Architectures for Opto-Electronic Analogs of Self-Organizing Neural Networks
Authors: Farhat Nabil H.
Published: February 2023

Architectures for partitioning opto-electronic analogs of neural nets into input/output and internal units to enable self-organization and learning where a net can form its own internal representations of the "environment" are described.
Optical associative processing elements with versatile adaptive learning capabilities
Authors: Fisher Arthur D. , Lee John N.
Published: February 2023

We are investigating associative processing architectures for tackling the massive parallel symbolic-processing demands of problems from image understanding, robotic manipulation and locomotion, expert-system problem solving, and other difficult artificial intelligence domains. A modular approach is taken, where a number of smaller adaptive, associative "modules" are nonlinearly interconnected and cascaded under the guidance of a variety of "organizational principles" to construct larger architectures for solving specific problems.1,2 Each module is a complete associative memory which adapts as it is exposed to associated information patterns (u,v), (e.g., feature vectors, encoded symbols, images,…), so that subsequent presentation of one pattern u results in recall of its paired pattern v.
Processing of Synthetic Aperture Radar Data Using the PRIMO Optical Outer-Product Processor
Authors: Owechko Y. , Grinberg J. , Marom E. , Soffer B.H.
Published: February 2023

The processing of SAR data is one of the great success stories of optical data processing. It is a problem which readily lends itself to the parallelism of optics. Optical solutions have, however, lacked two desireable characteristics: small size and real-time operation. Recently, novel optical architectures which overcome these drawbacks have been developed by Psaltis and Tanguay. (Some of which are reviewed in (1).) In this paper, we describe a new compact lensless real-time optical processor of SAR data which is unique in that it utilizes incoherent light and readily available components and materials.
Two-Dimensional Arrays of Semiconductor Optical Gates for Optical Computing
Authors: Gibbs Hyatt M.
Published: February 2023

The emphasis here is to assess the potential role of nonlinear thin-film etalons in optical computing. Nonlinear optics can contribute decisions to optical signal processing and computing.1 The optical nonlinearity makes the device's transmission intensity dependent, so one can obtain the thresholding needed for logic decision making. Nonlinear decision-making devices can be constructed as waveguides in which the light is guided in the plane of the nonlinear thin film or as etalons in which the light is imaged from one nonlinear thin film to the next in such a way that its intensity is highest as it interacts with each film. Guided-wave devices are most likely to find application where data are handled in a pipeline manner, for example, in optical-fiber communication and interconnect systems, data encryption, etc. However, waveguides are much like wires except for their higher bandwidth. Etalons permit massive parallelism and global interconnectivity, i.e., one can perform many operations simultaneously and interconnect in the next plane two or more pixels far apart in the present plane. Consequently we anticipate the use of guided-wave devices in the near term and increased introduction of etalons in the long term.
Towards An Optical/Electronic Hybrid Image Processor
Authors: Nicholson M G , Gibbons G G , Mayo S , Petts C R , Loiseaux B , Huignard J P , Dubois F , Ebbeni J
Published: February 2023

This paper describes work directed at utilising the parallel processing power of relatively simple analogue optical systems, to improve the capability, compactness and cost of machine vision systems. We are investigating methods which allow the combination of the best features of both electronic and optical systems in such a way that the control and decision-making are performed by the digital electronic system, whilst the parallel computations and data reduction are performed by analogue optical means. The resulting machine is termed a hybrid processor. Figure 1 shows a generalised block diagram of the Optical Functional Unit of such a system.
Classification of Normal and Aberrant Chromosomes by an Optical Neural Network in Flow Cytometry
Authors: Noehte S. , Männer R. , Hausmann M. , Homer H. , Cremer C.
Published: February 2023

This paper proposes to use an optical neural network for the real-time classification of normal and aberrant chromosomes in flow cytometry. It has been shown previously [1] that slit scan flow cytometry allows such an analysis for several problems of biomedical importance. Particularly, the rate of dicentric or translocation chromosomes can be used for a measurement of the radiation exposition of a patient in biological dosimetry.
Optical Artificial Intelligence Based on Semantic Network Architecture
Authors: Yatagai Toyohiko
Published: February 2023

In symbolic processing, associative network approaches show promise for solving difficult artificial intelligence problems. [1,2] Optical associative networks, including holographic[3,4] and matrix-vector multiplication [5] architectures, are one of the most attractive approaches toward large-scale associative processing. Optics provides both 2-D parallel interconnection ability between modules and parallel-computing mechanisms for parallel association algorithm. A hybrid optical inference architecture has been proposed. [6] Recently optical architectures for learning and self-organizing neural network are discussed.[7,8]
Adaptive two-dimensional quadratic associative memory using holographic lenslet arrays
Authors: Jang Ju-Seog , Shin Sang-Yung , Lee Soo-Young
Published: February 2023

Optical implementation of two-dimensional (2-D) quadratic associative memory (QAM) that needs parallel N6 weighted interconnections is described. We show that fully adaptive interconnections for the 2-D QAM are realizable by using two 2-D holographic lenslet arrays and two spatial light modulators (SLM’s). Thus two extensions of our previous work1 are proposed; they are learning capability and storage of 2-D images in QAM. We also show basic experimental results for the 2-D QAM.
Dual Beam Recrystallization of Silicon on PLZT
Authors: Ersen Ali , Dasgupta Samhita , Lin T. H. , Esener Sadik , Lee Sing H.
Published: February 2023

In the last few years extensive efforts have gone into the development of spatial light modulators (SLMs) for the realization of massively parallel optical processors [1-3]. The silicon-PLZT SLM approach is a promising approach and has the potential of combining the computational power of silicon with the communication power of optical interconnects [4]. Optical interconnects utilize the third dimension normal to the processing plane to provide the advantages of high speed parallel and global interconnections among simple silicon electronic circuits performing local computational operations. Fig. 1 shows the schematic of Si/PLZT SLM.
Multiply Exposed Photorefractive Holograms With Maximal Diffraction Efficiency
Authors: Brady David , Hsu Ken , Psaltis Demetri
Published: February 2023

Photorefractive materials are attractive for use as high density distributed storage media due to their dynamic response and high diffraction efficiency. Real-time holography is of particular interest in the implementation of optical neural networks. One of the key attractions of neural processors is their ability to “learn” input-output mappings by adapting distributed connections between processors. In an optical neural system, this adaptation typically involves updating holographic interconnections. Photorefractive crystals are useful for this application because photorefractive holograms may be updated continuously with no degradation in the holographic response.
Dynamic Optical Interconnection for Reconfigurable Neural Networks
Authors: Clymer Bradley D. , Ren Qiu-Shi
Published: February 2023

Neural networks have become attractive resources for the solution of a large class of problems which are not easily handled by traditional computing tools and strategies[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18]. The massive sharing of information between nodal processors in neural network configurations allows both redundancy for fault tolerance and a high level of association of data for classification problems such as sorting and character or pattern recognition. It is this massive data distribution that is at once the advantage of neural computing in that it facilitates solutions to difficult information processing problems and a disadvantage in that the enormous number of required interconnection paths can severely limit the size or capability of the network if wire paths are used.
Trainable Optical Network for Pattern Recognition
Authors: Hong John H. , Yeh Pochi
Published: February 2023

An optical implementation of a single layer network for pattern recognition is described in which both subtractive and additive changes of the weights can be made.
Optical Systems Tolerances for Symmetric Self Electro-optic effect Devices in Optical Computers
Authors: Craft Nick C. , Prise Michael E.
Published: February 2023

The s-SEED as a logic gate has been demonstrated [1] and we are building optical systems using them [2] to implement the architectures proposed by Murdocca [3]. Here we investigate the systems requirements we must meet in order to do this. We show that the s-SEED is a significantly easier optical logic device with which to build optical digital computers, than previously demonstrated devices. We demonstrate two methods of fully utilizing its advantages in the systems we are building. It is also the purpose of this paper to stimulate the design of other devices which will have the advantages of s-SEEDs.
GaAs Waveguide Microlenses and Lens Arrays with Applications to Data Processing and Computing*
Authors: Vu T. Q. , Tsai C. S.
Published: February 2023

Waveguide lenses are among the essential components in construction of integrated optic modules or circuits for data processing and computing. For this purpose, various types of waveguide lens have been fabricated in LiNbO3 substrate. These lens types include Luneburg, geodesic, index refraction via TIPE or two layers construction, chirp grating, and Fresnel. Some of these lens types have been utilized to construct RF spectrum analyzers, correlators,(1,2,3) and computers.(4,5,6) Despite the various successes with such LiNbO3-based modules they have only been developed into hybrid integrated optic (IO) modules due to lack of technology for integration of lasers, detectors, and associated electronic circuits in the same substrate. In contrast, the GaAs-based substrate provides the capability for monolithic integration of all passive and active components. However, the material constraints such as a very high refractive index and high brittleness, and the relatively small reduction in refractive index in Ga1−xAlxAs for a desirable fractional composition x have prevented any lens type from being fabricated in GaAs waveguide heretofore. We have most recently utilized ion-milling technique to fabricate waveguide lenses of high efficiency and diffraction-limited focal spot size in GaAs. In this paper, design, fabrication, and measured performances of single microlenses and microlens arrays of the analog Fresnel and chirp grating types as well as hybrid combination of the two are presented. IO modules that incorporate such waveguide lenses and acoustooptic and electrooptic Bragg modulators in channel-planar composite waveguides are also being constructed. The measured performances of such modules with applications to data processing and computing will also be reported.
Binary Arithmetic Using Optical Symbolic Substitution and Cascadable Surface-Emitting Laser Logic Devices
Authors: Cheng Julian , Olbright G. R. , Bryan R. P.
Published: February 2023

In this paper, we describe the design and operation of optical logic gates based on heterojunction phototransistor (HPT) and vertical-cavity surface-emitting laser (VCSEL) structures. We call the HPT/VCSEL structure a surface-emitting laser logic device. These structures will find use in optical communication systems as well as in parallel optical computing architectures. We illustrate complete sets of optical logic functions, upon which arithmetical logic units (ALU) are based, and provide specific examples of binary arithmetic operations based on optical symbolic substitution.
The Reliability of Optical Logic
Authors: Stirk Charles W. , Psaltis Demetri
Published: February 2023

One of the potential niches for optical logic is very high speed digital circuits. Conventional lithographic manufacturing techniques decrease the individual logic device cost when the device density per unit area increases. Thermal power dissipation limitations, however, restrict the device density at a given duty cycle and switching speed. Thus, we desire optical logic devices with small switching energies for high speed systems. Since switching energy usually decreases with decreasing device area, small devices decrease thermal dissipation problems and increase manufacturing density.
Spatial Noise Reduction in Array Illuminators
Authors: Lohmann Adolf W. , Sinzinger Stefan O.
Published: February 2023

An ideal array illuminator would provide equal amounts of light power to all elements of an array of gates or smart pixels. Existing array illuminators (abbreviated: AIL) achieve a homogeneity of 5 to 10%. That may seem to be good enough, if the signals are binary. However, it is desirable to achieve the best possible homogeneity, since there might be other causes for inhomogeneous behavior of the array system. Having a good AIL relieves the burden of tolerances for the other components of the overall system. Furthermore, when the signals are analog, as in some neural systems, the homogeneity of the power supply becomes even more important.
Two Dimensional Spatially Variant Optical Interconnects
Authors: Restall E. J. , Robertson B. , Taghizadeh M. R. , Walker A. C.
Published: February 2023

Spatially variant interconnects (SVIs) show great potential in the fields of optical computing and optical communications. Two dimensional forms of these interconnects offer even more power over their stacked one dimensional1 or wrap around counterparts2.
Design and fabrication of VLSI ferroelectric liquid crystal spatial light modulators
Authors: Jared David A. , Turner Richard , Johnson Kristina M.
Published: February 2023

This paper discusses several design and fabrication issues surrounding VLSI, ferroelectric liquid crystal (FLC) spatial light modulators (SLMs). These SLMs consist of a VLSI CMOS backplane and FLC modulators as shown in Fig. (1). The FLC is sandwiched between the CMOS backplane and a sheet of glass coated with a transparent conductor. The design and fabrication issues that are described include: FLC material selection, alignment of the FLC, installation of the glass cover, and the design of photodetectors, amplifiers, and pad drivers. An electrically addressed dynamic RAM SLM with 64 × 64 pixels and three optically addressed SLMs with 32 × 32 pixels are described to discuss these issues.
Huge optical amplification by applying pulsed electric fields to photorefractive crystals
Authors: Mathey P. , Pauliat G. , Launay J.C. , Roosen G.
Published: February 2023

A large number of proposed or demonstrated architectures for optical computing takes advantage of the unique properties of photorefractive crystals.
An optoelectronic full adder using: a beam scanning laser diode
Authors: Itoh Hideo , Mukai Seiji , Mori Masahiko , Watanabe Masanobu , Yajima Hiroyoshi
Published: February 2023

The present stage of the integration technology for optoelectronic digital computing systems is primitive, while this technology is essential for the systems to overcome electronic digital computers in the future. For example, an optical full adder is usually composed of several fundamental optical logic gates, and the number of these gates easily amounts to a prohibitive level when such adders are integrated. This difficulty will be relieved if the number of the gates composing an adder is reduced. The reduction of the gates also results in smaller size and higher operation speed of the system.
Implementation of a Fiber Optic Delay Line Memory
Authors: Soukup Todd J. , Heuring Vincent P.
Published: February 2023

The objective of the Digital Optical Computer (DOC) group at the University of Colorado at Boulder is to implement a general purpose computer using the speed advantages of light.[1] The machine is being implemented using lithium niobate directional couplers as logic elements and optical fiber loops for memory. Figure 1 shows the logic functionality of the directional coupler. Terminal C, normally an electronic input, has been converted to an optical input by the addition of a sensitive detector, amplifier, and thresholder.[2] This paper describes the implementation of the fiber optic delay line memory.
Techniques for Implementation of High-Speed Free-Space Optical Interconnections
Authors: Tsang Dean Z.
Published: February 2023

A free-space optical interconnection has zero insertion force and no ground planes. Low propagation delays are possible in board-to-board applications because of the direct path between interconnected points compared to the circuitous path often required by electrical interconnections. The optical channel has very high bandwidth and low dispersion. Furthermore, very high interconnection densities are possible because light beams can cross in free space. However, high­speed optoelectronic components are typically small and difficult to align in a computer environment. Experimental free-space optical interconnections have required the use of micropositioners for alignment and are not readily adapted for conventional computers.1 In this work, techniques for the practical implementation of high-speed board-to-board free-space optical interconnections without micropositioners have been developed. A free-space transmitter and receiver module combined with a card cage board enclosure designed for the application have made possible a differential electrical current efficiency (detector photocurrent divided by laser drive current) as high as 8%.
Hologram Recording by a Pulsed Method on Phase Change Media
Authors: Nonaka Koutarou , Nishida Yasuhide , Fujimori Susumu
Published: February 2023

This paper presents a novel real-time hologram recording method and derives a formula for calculating the diffraction efficiency of gratings recorded in phase change media. The formula gives media parameters for high diffraction efficiency. In addition, a two-dimensional character pattern is successfully reconstructed using GeTe alloy film.
Image Correlation Using Photorefractive GaAs
Authors: Cheng Li-Jen , Liu Duncan T.H. , Luke Keung L. , Kwong Norman S.Z.
Published: February 2023

Image correlation can be implemented optically, which takes full advantages of light, namely parallel operation and global interconnection with the Fourier transform provided by lens. Photorefractive compound semiconductors can provide this type of implementation1. This paper presents results from a detailed investigation on potentials of the photorefractive GaAs correlator for practical applications. The results illustrate that the matched filter formation rate in photorefractive GaAs crystal can be higher than 1000 frames per second. The filter contains complex values, leading to high quality correlation as demonstrated. Other advantages verified by experiments include real object image input with no need for preprocessing Fourier transform; edge enhancement automatically processed in the correlation process; dynamic spatial invariance, substantial enhancement of the signal by using a DC electric field providing high dynamic range; and easy alignment. In addition, this paper also presents the result of an experiment on imaging by phase conjugation in GaAs with 1.3 micron semiconductor injection lasers. This result provides realistic potentials to develop compact correlation modules using photorefractive semiconductors with semiconductor lasers. These modules could be building blocks for future "intelligent" automatic pattern recognition systems.
Optical Thresholding and Max Operation
Authors: Gu Claire , Yeh Pochi
Published: February 2023

Thresholding and Max operations are essential elements in the implementation of neural networks. Although there have been several optical implementations of neural networks, the thresholding functions are performed electronically [1-3]. Optical thresholding and Max operations have the advantages of parallelism and cascadability without resorting to optoelectronic conversion. Unfortunately, there has been very limited work in this area. In this paper, we propose and study the properties of self-oscillation in nonlinear optical (NLO) four-wave mixing (FWM) and NLO resonators for parallel optical thresholding and Max operations.
Hardware and Software System Design for Hybrid Optical-Electronic Signal Processing
Authors: Griffin R.D. , Lee J.N.
Published: February 2023

Many workers have demonstrated the potential of optical techniques to process high bandwidth data at very high computation rates.1,2 Optical processors have been proposed for such diverse applications as pattern recognition, neural networks, switching, digital computing, filtering, transformations, and matrix algebra. Since most of these methods implement specialized processors, they must be integrated into presently available digital electronic systems to obtain the necessary degree of control and flexibility for practical applications. Few systems exist today that realize the potential of these optical techniques, perhaps because of the amount of engineering and development effort that separates a successful laboratory demonstration from a useful and practical system. The engineering effort is complicated by the high bandwidth of the optical system: the input and output requirements of most optical systems can easily swamp traditional digital systems. Other complicating factors are data transduction between the electronic and optical domains, and dynamic range and signal-to-noise ratio requirements. In addition to the physical interface issues, the logical interface must be well-designed and easy to use. We present here some results of our effort to integrate a self-contained, "digital-in, digital-out" space-integrating one-dimensional matched filter system into a conventional digital processing system. This system can cross-correlate a 4000 point reference waveform with a 7000 point search waveform in about 100 µsec.