bluuebunny/crossref_metadata_2025 huggingface dataset:
Diode Pumped Solid State Lasers for High Power Precision Machining
Authors: Marabella Leonard J.
Published: February 2023

The objective of the Precision Laser Machining Technology Reinvestment Project (PLM TRP) is to develop the next generation laser machine tools and advanced manufacturing processes for both commercial and military applications. This is a government-industry cost share program sponsored by the Advanced Research Projects Agency (ARPA) to provide the most advanced and affordable US military systems, and the most competitive commercial products in the global marketplace for the automotive, aircraft/aerospace, heavy equipment, and shipbuilding industries. To accomplish the objective a Consortium of 20 organizations that represent industrial users, process developers, system integrators and technology developers has been established forming a user-driven, horizontally and vertically integrated team.
Record small-signal direct modulation bandwidths up to 40 GHz and low chirp characteristics (α = 1.4) in short-cavity strained In0.35Ga0.65As/GaAs MQW laser diodes
Authors: Schönfelder A. , Weisser S. , Czotscher K. , Larkins E.C. , Benz W. , Daleiden J. , Fleissner J. , Maier M. , Ralston J.D. , Rosenzweig J.
Published: February 2023

We demonstrate, for the first time, direct modulation bandwidths exceeding 40 GHz in short-cavity In0.35Ga0.65As/GaAs multiple-quantum-well laser diodes. Low linewidth enhancement factors (α = 1.4) have been extracted, indicating reduced laser chirp under high-speed direct modulation.
High-Power Diode Laser Transmitter for Aerosol LIDAR and Laser Ranging
Authors: Cornwell Donald M. , Yu Anthony W. , Hamagel Gary L. , Hopf Daniel E. , Millar Pamela S.
Published: February 2023

The next generation of space-based instruments for NASA will be smaller and more efficient than ever before. In keeping with this requirement, LIDAR and laser ranging systems are being developed which are based on AlGaAs semiconductor laser diodes [1, 2]. These systems use pseudo-random noise (PN) intensity modulation of the laser in conjunction with a correlation receiver to improve the overall system sensitivity and allow the inherently low-power diode laser to compete with much higher power solid state and gas lasers. While the size and efficiency of diode lasers make them attractive for such applications, the high-power, quasi-CW intensity modulation of these devices can introduce deleterious effects, such as spectral linewidth broadening. In addition, the highly-divergent beams from diode lasers require fast (F/1) optical systems, which in turn place micron-level tolerances on their opto-mechanical alignment and packaging. We present here the design and performance of a high-power diode laser transmitter which addresses the problem of spectral broadening under large-signal intensity modulation and also the problem of micron-level tolerance opto-mechanical packaging. The laser transmitter is a candidate for an aerosol LIDAR system currently operating at the South Pole, and may also enable future NASA laser ranging and communication systems.
High Power (>1 W) Semiconductor Lasers
Authors: Lang Robert J. , Parke Ross , Mehuys David , O’Brien Steve , Major Jo , Osinski Julian S. , Harnagel Gary , Shum Frank , Welch David F.
Published: February 2023

Coherent semiconductor sources based on flared amplifiers — monolithic and discrete MOPAs and flared unstable resonators have demonstrated the highest cw diffraction-limited output powers from semiconductor sources at wavelengths from 630 nm to beyond 2 μm. This talk will describe continuing advances in flared amplifier devices, including visible output powers approaching 1 W cw diffraction limited, powers up to 10 W diffraction-limited from monolithic devices, high-speed modulation, and more.
Spectral Properties of an AlGaAs MOPA Laser Under Large Signal Modulation of the Oscillator or the Amplifier
Authors: Krainak Michael A. , Cornwell Donald M. , Dutto Valerie , Yu Anthony W. , O'Brien Stephen
Published: February 2023

In this paper, we report on the optical spectrum characteristics of a modulated, high power (> 1 W average), monolithic flared amplifier master oscillator power amplifier (MFA-MOPA) laser. The CW performance of this laser is presented in Reference 1. The master oscillator (MO) is a distributed Bragg reflector (DBR) laser operating in a single longitudinal mode under CW operation. The power amplifier (PA) is monolithically integrated with the MO and has a tapered gain region. The laser was capable of delivering over 1 W of CW power with the MO biased at 140 mA and the PA biased at 4.0 A at operating temperature of 15°C. The MFA-MOPA can be tuned with temperature at a rate of 0.07 nm/°C. The instantaneous CW linewidth of the laser was measured to be 300 MHz (0.74 pm).
Beam Propagation Model of Tapered Amplifiers including Non-Linear Gain and Carrier Diffusion
Authors: Chazan P. , Ralston J.D.
Published: February 2023

Recent interest in high-power single-mode diode lasers has led to the evaluation of a variety of semiconductor amplifier geometries [1], integrated master oscillator power amplifier (MOPA), designs and flared oscillator devices. Flared amplifiers and oscillators have been found to be less sensitive to filamentation effects than broad area devices, although filamentation still ultimately limits the performance of such devices [2]. Using a FD-BPM model we investigate the performance to be expected from various flared laser structures in terms of both output power and beam quality. We clarify the influence of such material parameters as the number of quantum wells, the differential quantum efficiency and the linewidth enhancement factor on the output beam profile of the amplifier. We point out the influence of the linewidth enhancement factor showing that a reduction of this factor improves the output beam quality, the resistance to inhomogeneous injection, and the output farfield. Furthermore, a simulation of a 2D integrated elliptical lens is presented, showing the possibility of ‘on chip’ correction of the astigmatism for low α-factor structures. Such a lens would spare the use of an external cylindrical lens for collimation of the output signal.
Development of a Tritium Powered Semiconductor Laser
Authors: Ruda H. E. , Jedral L. , Mannik L.
Published: February 2023

Tritium is a radioisotope that emits beta radiation on its decay with a half life exceeding twelve years. The average emitted beta particle energy is ~6 keV. Typically for a semiconductor with bandgap on the order of ~1-2 eV for example, one incident beta particle could result in the production of ~1000 electron-hole pairs in the semiconductor. Beta decay thus represents an interesting generation source for the design of semiconductor-based light sources requiring no external energy supply. In this work we study the luminescence mechanisms resulting from such excitation in materials from the GaInAsP alloy system.
Jitter Measurements in Gain Switched DFB Semiconductor Lasers Coupled to Optical Fibers
Authors: Sapia Adalberto , Dellunde Jaume
Published: February 2023

Time jitter measurements in a repeatedly gain switched laser diode subject to a weak optical feedback are reported in this work. Reflections were induced by the tip of an optical fiber placed at a very short distance (10 μm) from the output laser facet. The results point out the importance of controlling the reflections due to optical elements inside dense packaged devices.
Analysis of Segmented Tapered Rib-Waveguide Semiconductor Optical Amplifiers
Authors: Spencer P.S. , Middlemast I. , Balasubramanyam R. , Sarma J. , Shore K.A.
Published: February 2023

A single stripe semiconductor laser typically produces about 10mW of output power. This figure can be increased to about 50-60 mW by using some complicated fabrications techniques, but the goal of achieving higher powers and maintaining single mode operation has proved elusive. When the drive current to a single stripe laser is increased two effects may occur to limit the output power: the inversion population starts to saturate, and Catastrophic Optical Damage, (COD), starts to destroy the facets. Several approaches to these problems have been tried, eg., increased active area, and laser arrays, and have generally been found to be unsatisfactory. Increasing the active area does indeed result in increased output power but at the expense of the far-field pattern; and, unfortunately, increasing the active area generally leads to multi-mode operation, and hence a poor far-field.
Quantum Interference Effect and Electric Field Domains in Multiple Quantum Well Structures
Authors: Xu Yuanjian , Shakouri Ali , Yariv Amnon
Published: February 2023

There has been great interest in studying optical and transport properties of multiple quantum well (MQW) structures. In these “artificial molecules”, energy quantization and the wave nature of the carriers have been used to design new devices, e.g., intersubband lasers. The understanding of carrier transport in MQWs is important for the design of lasers with high modulation speed. In this talk, we report on a new observation of a quantum interference effect in the photocurrent spectrum of weakly coupled bound-to-continuum MQWs. Using this effect, we analyze the electric field domain (EFD) formation in the superlattice [1].
An Fe-InP buried 1.3-μm double heterostructure laser heteroepitaxially grown on Si
Authors: Yamada T. , Tachikawa M. , Sasaki T. , Mori H. , Kadota Y. , Matsumoto S. , Kishi K.
Published: February 2023

Opto-electronic integrated circuits (OEICs), especially photonic devices on Si, are attractive because of their potential to combine photonic functions with highly integrated silicon electronic circuits. We have already demonstrated long term cw operation of a 1.5-μm multiple quantum well laser1) and high-temperature cw operation of a 1.3-μm double heterostructure (DH) laser2) heteroepitaxially grown on Si. Low threshold current lasers are required to reduce the power consumption of OEICs. An effective approach to reduce the threshold current is burying lasers with semi-insulating InP. The semi-insulating buried structure is also indispensable to reduce parasitic capacitance for high-frequency operation. Though a semi-insulating InP layer has been successfully grown on a Si substrate,3) there are no reports on its application to devices on Si.
The Use of Binary Magneto-optic Spatial Light Modulators in Pattern Recognition Processors
Authors: Flannery David , Loomis John , Milkovitch Mary
Published: February 2023

Binary magneto-optic spatial light modulators (SLM) [1] have been used successfully in several optical computing architectures. Here we concentrate on their use to implement binary phase-only filters [2-6] in coherent optical correlators including general characteristics, correlation performance, smart filters, and the potential for ternary filter encoding.
Nonlinear Optics of Liquid Crystals for Image Processing
Authors: Khoo Iam Choon
Published: February 2023

Current research and development in optical imaging, computing, communication and signal processing and switching have focused considerable efforts on highly efficient nonlinear optical and electro-optical materials. In combination with novel nonlinear optical processes and cw or pulsed lasers covering a wide spectral range, several useful practical devices have been developed. In particular, optical switching elements and logic gates1,2, infrared-to-visible image converter, real time image correlators, image or beam amplifiers3, nonlinear guided wave structures, optical memory devices (e.g., associative memory by phase conjugation4) and various beam steering and beam combining devices5 have been proposed and demonstrated. Concommitant to these device developments, optimization procedures and system requirement considerations have narrowed the "ideal" nonlinear optical materials to a few classes, such as semiconductors, photorefractive crystals and organic materials6. Several of these materials are still in the research phase, although they have been shown to possess many desirable characteristics (such as high speed and low energy requirements).
General Thin-Lens Action on Spatial Intensity Distribution Behaves as Non-Integer Powers of Fourier Transform
Authors: Ludwig Lester F.
Published: February 2023

This paper shows that the classical equations for the action of a thin-lens on the spatial intensity distribution of light [3] behave generally as non-integer powers of the Fourier transform [1,2] for separation distances within the lens-law boundary.
A Schottky Diode Liquid Crystal Light Valve
Authors: Efron U. , Stanchina W. E. , Rouse I. D. , Wu W. Y. , Goodwin N. W. , Reif P. G. , Wu S. T. , Welkowsky M. S.
Published: February 2023

We have recently developed and demonstrated a Schottky-diode-based LCLV. The concept is to use a Schottky metal-semiconductor interface which allows depletion through the silicon to be attained and thus maintain the impedance match between the photoconductor and the liquid crystal. This match is critical in achieving the operation of a photoactivated SLM.(1) Since a high Schottky barrier-forming metal such as aluminum or platinum can be deposited on the n-type silicon substrate at low temperature, the silicon substrate can first be mounted on a flat glass substrate, polished, and then processed. This allows a high degree of output uniformity to be attained. Secondly, by eliminating the SiO2 insulator present in our MOS LCLV version,(2) one can reduce the sheet conductivity at the Si/LC interface and achieve higher resolution and dynamic range.
Development of an e-Beam Charge-Transfer Liquid Crystal Light Modulator
Authors: Hirsch Peter W. , Farber Ira , Warde Cardinal
Published: February 2023

An electron beam charge transfer liquid crystal light modulator is being developed and demonstrated. Preliminary results show great potential for optical computing displays.
High Performance Single Crystal Silicon Liquid Crystal Light Valve with Good Image Uniformity
Authors: Sayyah K. , Welkowsky M.S.
Published: February 2023

Spatial light modulators play the role of converting an input image written in certain wavelength, intensity and coherence conditions to an output image in which some or all of these parameters are varied. As image amplifiers, these devices can be used for large screen display applications while as image wavelength converters, they can be used for displaying visible images from IR scenery or for missile testing. For optical image processing applications, spatial light modulators can be used as incoherent-to-coherent image converters.
Optimal Operation Temperature of a Si-LCLV
Authors: Wu Shin-Tson , Efron Uzi
Published: February 2023

A silicon liquid crystal light valve (Si-LCLV) is a useful device for converting an input image written in certain wavelength, intensity, and coherence conditions to an output image in which some or all of these parameters are varied. For examples, IR-to-visible(2) and visible-to-IR(3) image conversions using a Si-LCLV have been demonstrated successfully.
Performance Evaluation of a Transmissive Liquid Crystal Spatial Light Modulator
Authors: Lin Shih-Chun , Boughton R. Scott , Hong John , Reichman Joe
Published: February 2023

Liquid crystal spatial light modulators (LCSLM) have been used in many optical data processing systems. The one most often cited is the reflective type produced and marketed by Hughes Aircraft Company. Its construction, performance, and applications to real-time optical data processing have been reported before1,2. Grumman has recently developed an LCSLM, which allows both the write and the read beams to enter from the same side. The CdS photoconductor used is transparent to light of wavelength longer than 600 nm, so a red light, such as a He-Ne laser, will transmit through. Otherwise, the light valve operation is similar to the Hughes device.
Improved photorefractive performance from a special cut of BaTiO3.
Authors: Ford Joseph E. , Fainman Yeshaiahu , Lee Sing H.
Published: February 2023

Photorefractive materials have been used to construct optically controlled spatial light modulators (SLMs) using incoherent erasure of an index grating1 and using photorefractive gain2. An SLM should provide high resolution, large aperture, low noise and crosstalk, and fast time response. If gain is to be provided it should be high, and uniform to within the 3db criterion3. Among the currently available photorefractive materials, barium titanate has the best performance characteristics for optical signal processing applications requiring gain. It provides large index modulation, high sensitivity, reasonable response times, and crystals of good optical quality are available. However, utilization of these characteristics in a regularly cut crystal (with faces parallel to the (100), (010) and (001) crystallographic planes) introduces certain operational difficulties. To overcome these difficulties we have prepared a specially-cut crystal of BaTiO3, with faces parallel to the (100), (011), and
(011¯) crystallographic planes. In this paper, we will evaluate the performance of crystals with this orientation for information processing and particularly for SLM applications.
Photorefractive Spatial Light Modulator as a 2-D Beam Steering Array.
Authors: Roosen G.
Published: February 2023

Free space optical interconnections are of prime importance for both optical communications(1) and optical computing(2).
Development Issues for MCP-Based Spatial Light Modulators
Authors: Lee John N. , Fisher Arthur D.
Published: February 2023

Several of the most critically needed characteristics for two-dimensional (2-D) spatial light modulators (SLMs) include i)high input sensitivity, ii)high resolution, iii)long storage times, iv)high speed, and v)large dynamic range. One would desire to maximize all these characteristics simultaneously, but in actuality there exist tradeoffs that prohibit complete freedom in optimizing one parameter in isolation from the others. The microchannel-plate (MCP) devices, however, can be shown to have tradeoff points allowing unique performance in several of the above characteristics. The use of an MCP electron amplifier allows for internal signal gain, unlike most other SLMs where the output signal gain can be increased only by increasing the readout light level. Thus, detection and processing of very low signal levels, such as often encountered in multistage and feedback processing, becomes feasible. Further, MCP-based devices can intrinsically perform special image-processing operations (see Sec. III below).
Quantum well self-electrooptic effect devices for information processing
Authors: Miller D. A. B.
Published: February 2023

Recent work on these optically controlled semiconductor optoelectronic devices will be discussed, included large two-dimensional arrays, high performance devices, and prospects for integration with electronics.
Spatial Light Modulators Using Flexoelectric Effect
Authors: Patel J. S.
Published: February 2023

Flexoelectric effect1 in liquid crystal is important for spatial light modulators because it allows for polar effect in liquid crystals. The commonly used electro-optic effect for nematic liquid crystal is the dielectric effect whose magnitude is proportional to the square of the applied electric field. For this process the "switch on" process can be accelerated by applying larger values of the electric field, but there is no electrical control over the "switch off process. The "switch off process depends on the sample thickness and elastic properties of the system. In contrast to these processes the polar effects such as the flexoelectric effect1 and the more popular ferroelectric effect2 allows for electrical control over both the "switch on" and the "switch off" times.
The Biological Photochrome Bacteriorhodopsin and its Genetic Variant Asp96 → Asn as Reversible Media for Dynamic Optical Pattern Recognition
Authors: Hampp N. , Thoma R. , Oesterhelt D. , Bräuchle C.
Published: February 2023

The photochromic protein bacteriorhodopsin (BR) is contained in two-dimensional crystallized form in the purple membrane (PM) fragments from the cell membrane of Halobacterium halobium [1, 2]. BR belongs to the class of retinal proteins and is related to the human visual pigment. Excitation with light induces a cyclic sequence of photoconversions which are summarized in Figure 1. Even in dried PM-films the photocycle is observed. After absorption of a photon the protein reaches approximately 50 μs later the longest living M-form, which is about 160 nm blue-shifted from the initial state B. From the M-intermediate BR can relax either thermally or photochemically to the initial B-state.
Joint Transform Correlator Based on Photo-induced Anisotropy in Fluorescein-doped Boric Acid Glass*
Authors: O’Sullivan M.S. , Myslinski P.
Published: February 2023

Anisotropy in the nonlinear optical properties of fixed organic dye molecules has been used for polarization sensitive four wave mixing1 or transient holography.2,3 Here we demonstrate a joint transform correlator4 which is based on anisotropic angular distribution of fluorescein molecules fixed in boric acid glass.5 Linearly polarized pump light (457.9 nm wavelength) is used excite molecules into their long lived triplet state (lifetime = 0.2 s to 0.008 s depending on temperature). Excited molecules are probed by light from a second, linearly polarised, read beam and make transitions to higher lying triplet states. Since the transition electric dipole moments and the main axis of the polarizability tensor are aligned with the molecular axis, dichroism and birefringence in the glass, which change the state of the read beam polarisation, are controlled by the local pump intensity.
Suitability of Hydrogenated Amorphous Silicon Photosensors for Optically Addressed Spatial Light Modulators
Authors: Barbier P. R. , Walker C. M. , Moddel G.
Published: February 2023

We present the photoresponse of hydrogenated amorphous silicon photodiodes and demonstrate their suitability as photosensors in fast and efficient optically addressed spatial light modulators.
Characterization of a New CDSE Liquid Crystal Light Valve
Authors: Zhuang Songlin , Qiu Yinggang , Jiang Yinqui , Gu Linjuan , Cai Zhonghua , Tu Yinjung , Chao Tien-Hsin
Published: February 2023

The liquid crystal light valve (LCLV) is one of the most widely used spatial light modulators in optical information processing research because of its high resolution and large throughput. The Hughes CdS LCLV has the advantages of high sensitivity and high resolution [1-3]. However, it has a relatively slow response dm, especially in the case of low writing light intensity. Recently, an amorphous silicon photoconductor has been used in the LCLV to improve its response time [4]. However, its spectral response is shifted to the longer wavelengths and thus its sensitivity is much lower than the CdS LCLV in the visible spectral region.
Design and characteristics of liquid crystal light modulators
Authors: Uchida Tatsuo
Published: February 2023

Liquid crystal light modulators (LCLMs) are classified into optical writing type and electrically writing type. Both types are useful for optical and electrical information sources. Recently, the electrical writing type has made progress as liquid crystal displays (LCDs) for laptop computers and pocket television. These LCDs are also classified into direct matrix type and active matrix type by using thin-film transistors or nonlinear diodes. In this presentation, the fundamental design concept and characteristics of these LCLMs are discussed in detail.
Electron Beam-Addressed Liquid Crystal Phase Modulator
Authors: Melnik G.A. , Genetti G.J. , Horsky T.N. , O’Mara D.M. , Tsakiris T.N. , Warde C. , Gilbreath G.C.
Published: February 2023

The electron beam-addressed liquid crystal phase modulator is an extension of the charge transfer signal processor developed by Warde and Dillon,1 in that the device is optimized for phase modulation by incorporating a thick layer of homogeneously aligned liquid crystal as the light modulation element The index of refraction of the liquid crystal layer is modulated by the electric field set up by an accumulated charge distribution via the electro-optic effect. The resulting spatial variations in the index of refraction then modulate the phase of the readout light upon reflection.
Optical neural networks
Authors: Softer Bernard H. , Owechko Yuri , Dunning G.J.
Published: February 2023

Spatial light modulators (SLMs) play an essential role in almost every optical implementation of neural networks. They are used to perform some or all of the functions of input, neural states and interconnection pattern. If we take a very broad encompassing definition of SLMs to include one- and two-dimensional LED arrays and perhaps even fixed masks, then every optical neural network implementation we know of uses SLMs.
Longitudinal Effect PLZT Spatial Light Modulators
Authors: Tully John W. , Biricik V. Warren
Published: February 2023

This paper presents the design and fabrication aspects of a longitudinal effect PLZT spatial light modulator designed for operation in the visible and near infrared.
Structures and Drive Modes for Optically Addressed Ferroelectric Liquid Crystal Slms
Authors: Moddel Garret , Barbier Pierre R.
Published: February 2023

We survey structures and drive modes for optically addressed spatial light modulators (OASLMs) which incorporate surface stabilized ferroelectric liquid crystal (FLC) light modulating layers and hydrogenated amorphous silicon (a-Si:H) photosensors.
Chiral Smectic Liquid Crystals for High Information Content Displays and Spatial Light Modulators
Authors: Johnson Kristina M. , McKnight Douglas J. , Mao Chongchang , Sharp Gary , Liu Jian-Yu , Sneh Anat
Published: February 2023

Although the liquid crystal display market is being driven by the need for a light weight display in computer workstations, laptop computers and notebook computers, there are other applications for high density, high information content displays.
Smart and Advanced Spatial Light Modulators
Authors: Brocklehurst J R , Collings N , Crossland W A , Mears R J , Vass D G , Worboys M R
Published: February 2023

This paper reports the work of a collaboration which has sought to design smart ferroelectric liquid crystal spatial light modulators (Smart SLMs) by starting with potential systems applications and asking what functions are required of the smart SLM for it to perform a useful task in the system.
Electrically addressed field effect transistor self electro-optic effect device (FET-SEED) amplified differential modulator array.
Authors: Lentine A. L. , Chirovsky L. M. F. , D’Asaro L. A. , Laskowski E. J. , Pei S. S. , Focht M. W. , Freund J. M. , Guth G. D. , Leibenguth R. E. , Smith L. E. , Woodward T. K.
Published: February 2023

The integration of Gallium Arsenide field effect transistors (GaAs - FETs) and multiple quantum well modulators is an exciting advancement in the area of optical interconnections [1-3].
Polarization Behavior of a Ferroelectric Liquid Crystal Light Valve
Authors: Xue W. , Collings N.
Published: February 2023

Surface stabilized ferroelectric liquid crystal spatial light modulators (FLCSLM's) might be used in both neural network and optical interconnect applications
Liquid Crystal Spatial Light Modulators for Optical Image Preprocessing
Authors: Parfenov A. V. , Buchholz J. C.
Published: February 2023

Spatial light modulators (SLM) are considered as the main elements of optical data processing systems. Liquid crystal SLMs (LCSLM) having high performance parameters are normally used in optical systems as image transducers and optical filters. The value of LCSLM for optical data processing is increased by combining image transducing and image preprocessing functions in the same sample. Such a combination improves the flexibility and productivity of optical data processing methods, and simplifies optical setup. Among realized preprocessing functions of LCSLM are the edge enhancement, the selection of nonstationary objects, the optical analog of lock-in-amplifier, image subtraction, and spatial selection of the image details corresponding to their intensity. Most of mentioned preprocessing functions and new features like IR-sensitivity, IR-modulation are primarily realized in LC SLM at P.N.Lebedev Institute. The physical mechanisms for these opportunities are discussed together with possible improvements in parameters and features. Recently observed new electro-optical effects in ferroelectric liquid crystals are reported as ones giving new opportunity to combine image preprocessing and fast response.
A Novel High Contrast Multiple Quantum Well Spatial Light Modulator Based on Polarization Rotation
Authors: Shen H. , Wraback M. , Pamulapati J. , Dutta M. , Kosinski J. , Chang W. , Newman P. , Lu Y.
Published: February 2023

Prior research on multiple quantum well (MQW) spatial light modulators (SLM) has concentrated on amplitude modulation, relying on a sufficient difference in the absorption coefficient between the on/off states at the operating wavelength to achieve useful contrasts.
Ex-situ Cavity Phase Tuning of InGaAs/AlGaAs Multiple Quantum Well Based Inverted Asymmetric Fabry-Perot Reflection Modulators
Authors: Hu Kezhong , Cartland R. , Chen Li , Kaviani K. , Chen P. , Madhukar A.
Published: February 2023

A large array of light modulators is one of the key building blocks for optical computing and interconnection. Multiple quantum well (MQW) based asymmetric Fabry-Perot (ASFP) modulators1-6 are a promising candidate for providing the basic surface normal switching function with high contrast and throughput, low switching energy and insertion loss.
A Design Model for Reflection Mode MQW Modulators Based on Minimization of Power Penalties
Authors: Fan C. , Hansen M. W. , Shih D. W. , Esener S. C.
Published: February 2023

The quantum-confined Stark effect and the Wannier-Stark effect in multiple-quantum-well (MQW) materials have been used in Fabry-Perot étalons to modulate the total reflected power.
Potential Field Computation for Robotic Path Planning Using a Microchannel SLM
Authors: Reid Max B.
Published: February 2023

A microchannel SLM is employed to demonstrate the optical calculation of potential field maps for mobile robot navigation. In one MSLM mode, written patterns expand spatially, and this characteristic is used to create an extended two dimensional function representing the influence of the goal in a robot's workspace. The optical calculation time scales favorably in comparison to digital electronic computation.
Optically addressed intrinsic multiple quantum well spatial light modulators
Authors: Rabinovich W. S. , Bowman S. R. , Katzer D. S. , Kyono C. S.
Published: February 2023

Recent demonstrations of perpendicular geometry GaAs/AlGaAs multiple quantum well (MQW) structures as optically addressed spatial light modulators (OASLM) have shown that these devices can offer high speed [1] and high resolution [2].
Spatial light modulation based on photo-induced change in the complex refractive index of bacteriorhodopsin
Authors: Takei Hiroyuki , Shimizu Norio
Published: February 2023

Bacteriorhodopsin (bR) is a photosensitive molecule found in the cell membrane of Halobacterium halobium. It has a large extinction coefficient of 6.3 x 104 M-1 cm-1 at 568 nm. A chromophore, which is responsible for absorption, undergoes rapid isomerization upon photon absorption. In tens of µs, the M photo-intermediate whose absorption maximum is at 412 nm forms. Irradiation of the M photointermediate results in regeneration of the original B state. Thus, bR has a potential as a photoreversible photochromic material. It is characterized by a high quantum efficiency of over 60%, exceptional cyclical durability of more than million cycles, and excellent mechanical stability over several years.
Nonlinear optical image processing with bacteriorhodopsin films
Authors: Downie John D.
Published: February 2023

The transmission properties of bacteriorhodopsin film spatial light modulators are used to perform nonlinear optical image processing operations on images with multiplicative noise. A logarithmic amplitude transmission characteristic of the film permits the real-time optical conversion of multiplicative noise to additive noise, which is then linearly filtered out in the Fourier plane of the transformed image. We present experimental results for different image and noise situations, including deterministic noise and speckle.
Novel Electroclinic Liquid Crystal Materials for Spatial Light Modulators
Authors: Ratna B. R. , Shashidhar R.
Published: February 2023

Electroclinic liquid crystal materials are promising for applications, such as spatial light modulators, that require analog phase modulation capability and fast response times1. The evolution of this technology greatly depends on the development of chiral smectic A materials with large induced tilt angles, field-independent and fast switching times and a broad operating temperature range. Development of such materials require a fundamental understanding of the molecular structure and its relation to the electrooptic performance.
Tunable Holographic Wavelength Filter
Authors: Parker M.C. , Warr S.T. , Mears R.J. , Crossland W.A.
Published: February 2023

The high available bandwidth of optical fibres has led to a large interest in wavelength division-multiplexed (WDM) networks. Such systems rely on the functionality provided by tunable sources, receivers and filters. Components must be quickly tunable over a large range, have a narrow-band channel response, low insertion loss and be robust and repeatable in their operation. Various wavelength filtering techniques have been previously proposed. These have been based on liquid crystal birefringent slabs [1], Fabry-Perot cavity filters [2], acousto-optic surface wave effects [3] and semiconductor resonant amplification [4]. A method of space-wavelength switching using a mechanically rotatable grating has also been demonstrated [5]. Such methods are generally analogue in operation and require complex calibration or control techniques.
Experimental Investigation of Free Space Optical Interconnects.
Authors: Stevens A.J. , Gourlay J. , Samus S. , Hossack W.J. , Vass D.G. , Burns D.C.
Published: February 2023

Free space optical interconnects have applications in many optical systems such as crossbars, optical neural networks and telecommunications. The interconnect may be implemented in two ways; by the use of static holographic elements to fan out the input channels onto a modulating plane which allows only the only the appropriate channels to propagate1,2, or by using a dynamic holographic element to provide direct interconnection3,4. Ferroelectric, liquid crystal over silicon spatial light modulators (FLC/VLSI SLM’s) have been demonstrated to be suitable elements as both an amplitude modulating plane addressed by holographic elements, and as a phase modulating plane for encoding dynamic holograms. The aim of this paper is to assess the capabilities of FLC/VLSI SLM’s in both these roles using experimental test systems. In order to do this, performance criteria such as scalability, diffraction efficiency, uniformity, contrast ratio, optical throughput, and switching speed shall be considered. Finally, the analysis of these results will provide an insight into the performance of future FLC/VLSI SLM’s in optical free space routing systems.
MIS model of optically addressed spatial light modulators
Authors: Wang Li , Moddel Garret
Published: February 2023

Optically addressed spatial light modulators (OASLMs) that incorporate nematic liquid crystal (NLC) light modulating layers find many applications in optical information processing due to their gray-scale capability. These devices are usually driven with sine or square-wave voltages at frequencies of 1-10 kHz that are beyond those to which the NLC can respond. The NLC responds to the rms value of the applied voltage across it. Some NLC OASLMs incorporate photosensors of hydrogenated amorphous silicon (a-Si:H) that offer high resolution and high sensitivity[1-6]. We have made some NLC OASLMs with intrinsic a-Si:H for phase-modulation applications. The observed behavior from these devices cannot be explaining using a resistor-capacitor circuit model in which the a-Si:H is treated as a photoconductor. Instead, a metal-insulator-semiconductor (MIS) model is found to fit the experimental data very well. The indium-tin oxide (ITO) electrode and the NLC layer in the OASLM form the respective metal and insulator layers. This MIS model can be used to optimize the thicknesses of the NLC and a-Si:H layers in an OASLM to obtain large phase or amplitude modulation.
Noise induced switching and stochastic resonance in an optically addressed spatial light modulator
Authors: Sharpe John P. , O’Brien Dominic C. , Moddel Garret
Published: February 2023

Since it was first adduced as a possible explanation for the periodic occurrence of the earths ice ages [1] [2], the phenomenon of stochastic resonance has been extensively investigated, both theoretically and experimentally. An intuitive understanding of the phenomenon may be developed by considering figure 1(a) which shows a particle in a double potential well. Under a large periodic perturbation of the wells (1(b)) the particle can escape from well to well, and if we regard the particle position as the observable or signal then the power spectrum of this signal will exhibit a large peak at the perturbation frequency. Under large random forcing the particle also makes the transition between the two wells but this time in a random fashion and the output spectrum is typically Lorentzian. In the case where there is a small periodic perturbation the particle is unable to escape from the right hand well where it resides initially (fig 1(c)). However, if random noise is now added the particle can make the transition with a greater probability from right to left when the right well is higher and vice versa when it is in the left well. As may be imagined, if there is insufficient noise then no transitions are made while if the noise is too large then the random switching dominates. It is this notion of an optimum amount of noise coupled with a small periodic component in a nonlinear system that forms a definition of stochastic resonance.
Large Arrays of Spatial Light Modulators Hybridized to Silicon Integrated Circuits
Authors: Worchesky T. L. , Ritter K. J. , Martin R. , Lane B.
Published: February 2023

Designs 128x128 spatial light modulators hybridized to silicon integrated circuits are presented; and results of arrays operating at 100,000 frames/second are reported.
The Thin Film Filters for the Extreme Ultraviolet Explorer Satellite
Authors: Vedder P.W. , Vallerga J. , Siegmund O.H.W. , Malina R.F.
Published: February 2023

The Extreme Ultraviolet Explorer (EUVE) satellite will conduct an all-sky survey in the extreme ultraviolet (EUV) between 80 and 900 Å. The survey mission will be performed using three grazing incidence EUV telescopes equipped with microchannel plate (MCP) detectors. A fourth telescope will provide a deeper survey over a limited portion of the sky and contains three spectrometers for pointed EUV spectroscopic observations of selected objects. Thin film filters are used directly in front of the imaging MCP detectors to define four separate photometric bandpasses for the survey and act as order filters for the spectrometers.
Stellar Interferometry in Space - Science and Strategy
Authors: Greenaway A. H.
Published: February 2023

Particularly for imaging applications, and to a lesser extent for astrometry, the design of a spacecraft interferometer has a direct influence on the range of scientific problems that the instrument may address.
Stellar Interferometer Design for Minimizing Polarization-Induced Visibility Losses
Authors: Traub Wesley A.
Published: February 2023

The effects of non-normal-incidence optical phase shifts at the surfaces of mirrors in the arms of stellar interferometers are considered. An explicit expression is given for the wavelength-dependant loss in fringe visibility which results from measureable phase shifts between the perpendicular and parallel reflected components of unpolarized radiation. This loss occurs as a result of the generally different reflection to-pologies in the various arms of an interferometer. An optical design method is presented which eliminates these potentially degrading effects. This method essentially says that the radiation in each arm should experience reflections having the same sequence of direction cosines between the point where the beam is divided and the point where it is combined. We also show that other useful properties of interferometers are obtained by following this rule. Wavelength-dependent phase-shift measurements on real mirrors are presented, allowing numerical evaluation of the degradation factor for any optical configuration. Various optical configurations are shown to illustrate the effect, including new COSMIC (Coherent Optical System of Modular Interferometric Collectors) designs.
An Entry Level Interferometer for Space
Authors: Bely P.Y. , Burrows C. , Roddier F. , Weigelt G.
Published: February 2023

Observational optical astronomy is always scientifically driven to develop telescopes with fainter limiting magnitude and higher resolution. Larger ground-based telescopes are more sensitive, but give little improvement in resolution unless extremely demanding interferometric techniques are used. Space-based telescopes of traditional configuration such as the Hubble Space Telescope (HST) give great improvements in resolution being diffraction limited, and a consequent improvement in limiting magnitude, but further improvements are limited by launch constraints.
Point-to-Point Laser Metrology for POINTS
Authors: Phillips James D. , Reasenberg Robert D.
Published: February 2023

The Precision Optical INTerferometer in Space (POINTS) is an astrometric instrument comprising a metrology system and two starlight interferometers mounted at an angle ϕ ≈ 90 deg. This angle, which must be measured with an uncertainty small compared to the nominal instrument accuracy of 5 microarcseconds (μas), is determined by measuring the six distances among four fiducial points, two for each interferometer. The fiducial points are connected to the starlight optics via Full Aperture Metrology (Babcock et al., in this Digest; Reasenberg, in this Digest). Because of the observing geometry, the uncorrelated part of the error in the distance measurements must be held to a few picometers (pm). In this paper, we consider a new, “two color” laser gauge that appears to meet the requirements of POINTS. We are developing a test version of such a gauge.
Innovations in Optical Technologies for Extreme Ultraviolet Astronomy
Authors: Bowyer Stuart
Published: February 2023

Extreme ultraviolet (EUV) astronomy has been a late arrival to the scene of space astronomy. Part of the reason for this was an incorrect appraisal of incomplete astronomical knowledge, which lead to the belief that, intrinsically, this kind of astronomy could not be carried out. Equally important was the lack of appropriate optical technologies for this field.
The GSFC Diffraction Grating Evaluation Facility - Capabilities and Application
Authors: Leviton Douglas B. , Osantowski John F.
Published: February 2023

The Optical Research Section at the Goddard Space Flight Center (GSFC) is developing the diffraction grating evaluation facility (DGEF) to evaluate the performance of new technology diffraction gratings for future space flight instrumentation. Because grating performance is most accurately assessed with the grating in the optical configuration for which it is designed, the DGEF has been devised to evaluate gratings in an optical breadboard scheme that emulates design concepts or design options. The working volume of the DGEF was sized to accomodate proposed spectrographic designs for future missions, e.g. Lyman or the Far Ultraviolet Spectrographic Explorer (FUSE), and second generation Space Telescope Instruments such as the Space Telescope Imaging Spectrograph (STIS).
Comparison of Imaging Approaches for Extrasolar Planet Detection
Authors: Diner David J. , Tubbs Eldred , Appleby John F. , Duval Valerie G. , Gaiser Steven L. , Jones Dayton L. , Korechoff Robert P. , Ribak Erez , van Zyl Jakob
Published: February 2023

We have been examining the optical performance requirements of systems capable of directly detecting Jupiter-like and Earth-like planets around nearby stars. The system requirements are driven by (1) the desire to observe a statistically significant stellar population, such that even a null result would have scientific value, (2) the extreme brightness contrast between the parent stars and their companions, and (3) the required sensitivity owing to the intrinsically faint planetary signals. By using detection and characterization of Earth-like planets as our ultimate objective, we plan to establish a technological target which can then be used to govern near-term developmental activities, including system designs to search for larger, brighter planets around the nearest stars. Since we have no a priori information as to how many planets may exist around a given star, imaging is deemed to provide the most robust method of searching. There are two methods of producing images: directly and interferometrically, and three wavelength regions to be considered: visible, infrared, and submillimeter. Our study includes this entire matrix of possible approaches.
Scattering Analysis Problems from Visible to X-ray
Authors: Glenn Paul
Published: February 2023

Scattering due to optical surface imperfections manifests itself very differently in infra red, visible, extreme ultra violet, and X-ray systems. (In this context, we are limiting ourselves to relatively small angle scattering on the order of arc seconds or minutes, as opposed to wider angle stray light.) The differences are due not only to the very different radiation wavelengths, but also to the very different geometries required of the optical systems. For example, infra red and visible systems use conventional, near normal incidence optical surfaces, while X-ray systems use grazing incidence, near cylindrical surfaces. Extreme ultra violet systems can use surfaces which fit neither of these descriptions very well, and which have quickly changing curvatures and incidence angles.
Technical challenges and science benefits of using astrometric devices to track laser-carrying spacecraft
Authors: Schumaker Bonny L.
Published: February 2023

Research and development related to the use of lasers for optical communication links with planetary spacecraft is now being pursued vigorously by NASA and other organizations worldwide. Baseline models envision a 1-Watt, frequency-doubled Nd:YAG laser (532 nm) firing through a 30-cm telescope aboard spacecraft as early as the late 1990's. At Saturn or Neptune, for example, such a laser would look to typical broadband astrometric detectors like a Sun-like star of apparent visual magnitude 12 or 15, respectively. JPL has been looking into the use of astrometric techniques to locate and track the angular motion of the spacecraft relative to nearby quasi - stationary stars or solar-system objects. This talk will discuss some of the technical challenges and advantages associated with the use of single-telescope (e.g., with Ronchi gratings) and interferometric astrometric techniques for tracking spacecraft, both from the ground and from space. Also to be discussed are some of the potential science benefits that would result from a laser on board a spacecraft and a precise astrometric tracking capability.
A Space Station Millimeter Facility
Authors: Weiler K.W. , Dennison B.K. , Johnston K.J.
Published: February 2023

The design and use of a large millimeter facility for construction on the planned Space Station (the Space Station Millimeter Facility, SSMF) will be described. A facility consisting of a number of small antennas distributed over the structure of the Station and linked to form a coherent interferometric array operating at millimeter-submillimeter wavelengths will have manifold applications in both basic and applied research. Earth surface surveying, atmospheric studies, communications research, and, especially, astronomy will be greatly enhanced by such an instrument.