The Quantum Scientific Computing Open User Testbed (QSCOUT) at Sandia National Laboratories is a trapped-ion qubit system designed to evaluate the potential of near-term quantum hardware in scientific computing applications for the U.S. Department of Energy and its Advanced Scientific Computing Research program. Similar to commercially available platforms, it offers quantum hardware that researchers can use to perform quantum algorithms, investigate noise properties unique to quantum systems, and test novel ideas that will be useful for larger and more powerful systems in the future. However, unlike most other quantum computing testbeds, the QSCOUT allows both quantum circuit and low-level pulse control access to study new modes of programming and optimization. The purpose of this article is to provide users and the general community with details of the QSCOUT hardware and its interface, enabling them to take maximum advantage of its capabilities.
The design, construction, and testing of a high-magnification, long working-distance plenoptic camera is reported. A plenoptic camera uses a microlens array to enable resolution of the spatial and angular information of the incoming light field. Instantaneous images can be numerically refocused and perspective shifted in post-processing to enable threedimensional (3D) resolution of a scene. Prior to this work, most applications of plenoptic imaging were limited to relatively low magnifications (1× or less) or small working distances. Here, a unique system is developed with enables 5× magnification at a working distance of over a quarter meter. Experimental results demonstrate ~25 µm spatial resolution with 3D imaging capabilities. This technology is demonstrated for 3D imaging of the shock structure in a underexpanded, Mach 3.3 free air jet.
The design, fabrication, and performance of InGaAs and InGaP/GaAs microcells are presented. These cells are integrated with a Si wafer providing a path for insertion in hybrid concentrated photovoltaic modules. Comparisons are made between bonded cells and cells fabricated on their native wafer. The bonded cells showed no evidence of degradation in spite of the integration process that involved significant processing including the removal of the III-V substrate.
The design, construction, and initial testing of a high-magnification, long working-distance plenoptic camera is reported. A plenoptic camera uses a microlens array to enable resolution of the spatial and angular information of the incoming light field. With this, instantaneous images can be numerically refocused and perspective shifted in post-processing to enable instantaneous three-dimensional (3D) resolution of a scene. Prior to this work, most applications of plenoptic imaging were limited to relatively low magnifications (1× or less) or small working distances. Here, a unique system is developed with enables 5× magnification at a working distance of over a quarter meter. Experimental results demonstrate ~25 m spatial resolution with 3D imaging capabilities. This technology is demonstrated on two practical applications. First, burning aluminum particles on the order of 100 m in diameter are imaged near the reacting surface of a combusting solid rocket propellant. The long working distance is particularly advantageous for protection of the experimental hardware in this extremely hazardous environment. Next, background oriented schlieren is used to resolve the 3D structure of an underexpanded free jet. This demonstrates the ability to resolve index-of-refraction gradients at the working distances and spatial scales necessary to meet our ultimate goal of resolving 3D turbulent transition in the boundary layer of Sandia’s Hypersonic Wind Tunnel (HWT).
Concurrent sound associated with very bright meteors manifests as popping, hissing, and faint rustling sounds occurring simultaneously with the arrival of light from meteors. Numerous instances have been documented with â '11 to â '13 brightness. These sounds cannot be attributed to direct acoustic propagation from the upper atmosphere for which travel time would be several minutes. Concurrent sounds must be associated with some form of electromagnetic energy generated by the meteor, propagated to the vicinity of the observer, and transduced into acoustic waves. Previously, energy propagated from meteors was assumed to be RF emissions. This has not been well validated experimentally. Herein we describe experimental results and numerical models in support of photoacoustic coupling as the mechanism. Recent photometric measurements of fireballs reveal strong millisecond flares and significant brightness oscillations at frequencies ≥40 Hz. Strongly modulated light at these frequencies with sufficient intensity can create concurrent sounds through radiative heating of common dielectric materials like hair, clothing, and leaves. This heating produces small pressure oscillations in the air contacting the absorbers. Calculations show that â '12 brightness meteors can generate audible sound at ∼25 dB SPL. The photoacoustic hypothesis provides an alternative explanation for this longstanding mystery about generation of concurrent sounds by fireballs.
Spectrum splitting is an optical technique that can increase conversion efficiency or add energy storage capability to a photovoltaic (PV) energy system. In this Sandia National Laboratory Campus Executive project, two distinct types of Diffractive Optical Elements (DOEs) for spectrum splitting were developed, fabricated and measured. The first DOE was an algorithmically-designed freeform surface relief structure. A parametric study of the Broadband Gerchberg-Saxton algorithm was performed to show the effect of design variables on device performance. Two DOE designs were fabricated using a grayscale Maskless Lithography Tool (MLT) and measured. The second DOE was a volume holographic lens. This concept was explored in the context of hybrid PV/biofuel implementation, and was later applied to a multiple-bandgap PV module. A design process was developed to ensure diffraction into a single order across the lens and to enable spectral tuning of diffracted light. A proof-of-concept off-axis holographic lens was fabricated and measured. The report concludes with a summary of spectrum splitting performance and discussion of areas for improvement and future work.
A unique, micro-scale architecture is proposed to create a novel hybrid concentrated photovoltaic system. Micro-scale (sub-millimeter wide), multi-junction cells are attached to a large-area silicon cell backplane (several inches wide) that can optimally collect both direct and diffuse light. By using multi- junction III-V cells, we can get the highest possible efficiency of the direct light input. In addition, by collecting the diffuse light in the large-area silicon cell, we can produce power on cloudy days when the concentrating cells would have minimal output. Through the use of micro-scale cells and lenses, the overall assembly will provide higher efficiency than conventional concentrators and flat plates, while keeping the form factor of a flat plate module. This report describes the hybrid concept, the design of a prototype, including the PV cells and optics, and the experimental results.
High-speed photometric observations of meteor fireballs have shown that they often produce high-amplitude light oscillations with frequency components in the kHz range, and in some cases exhibit strong millisecond flares. We built a light source with similar characteristics and illuminated various materials in the laboratory, generating audible sounds. Models suggest that light oscillations and pulses can radiatively heat dielectric materials, which in turn conductively heats the surrounding air on millisecond timescales. The sound waves can be heard if the illuminated material is sufficiently close to the observer’s ears. The mechanism described herein may explain many reports of meteors that appear to be audible while they are concurrently visible in the sky and too far away for sound to have propagated to the observer. This photoacoustic (PA) explanation provides an alternative to electrophonic (EP) sounds hypothesized to arise from electromagnetic coupling of plasma oscillation in the meteor wake to natural antennas in the vicinity of an observer.
Digital image correlation (DIC) uses images from a camera and lens system to make quantitative measurements of the shape, displacement, and strain of test objects. This increasingly popular method has had little research on the influence of the imaging system resolution on the DIC results. This paper investigates the entire imaging system and studies how both the camera and lens resolution influence the DIC results as a function of the system Modulation Transfer Function (MTF). It will show that when making spatial resolution decisions (including speckle size) the resolution limiting component should be considered. A consequence of the loss of spatial resolution is that the DIC uncertainties will be increased. This is demonstrated using both synthetic and experimental images with varying resolution. The loss of image resolution and DIC accuracy can be compensated for by increasing the subset size, or better, by increasing the speckle size. The speckle-size and spatial resolution are now a function of the lens resolution rather than the more typical assumption of the pixel size. The paper will demonstrate the tradeoffs associated with limited lens resolution.
Silicon usage in fixed, flat-panel photovoltaic systems can be reduced by 60 to 75% with no efficiency loss through use of arrays of mini-concentrators. These concentrators are simple trough-like reflectors that are formed in flat sheets of ~1- mm thick optical plastic. Concentration ratios of 2.55X can be achieved on rooftops and 4.0X on walls while collecting all of the direct sun and scattered skylight. The concentrators are fabricated in optical plastic— preferably polycarbonate for its high refractive index. The panels are typically 1mm thick so the weight of a panel is ~1kg/m2. In addition to the rooftop, wall and window blind designs, a design is proposed that can be tilted toward the sun position at the equinox. These systems are all designed so they can be mass-produced.
Microsystems Enabled Photovoltaics (MEPV) is a relatively new field that uses microsystems tools and manufacturing techniques familiar to the semiconductor industry to produce microscale photovoltaic cells. The miniaturization of these PV cells creates new possibilities in system designs that can be used to reduce costs, enhance functionality, improve reliability, or some combination of all three. In this article, we introduce analytical tools and techniques to estimate the costs associated with a hybrid concentrating photovoltaic system that uses multi-junction microscale photovoltaic cells and miniaturized concentrating optics for harnessing direct sunlight, and an active c-Si substrate for collecting diffuse sunlight. The overall model comprises components representing costs and profit margin associated with the PV cells, concentrating optics, balance of systems, installation, and operation. This article concludes with an analysis of the component costs with particular emphasis on the microscale PV cell costs and the associated tradeoffs between cost and performance for the hybrid CPV design.
Reflective particle tags derive their unique identities through utilization of thousands of microscopic reflective elements randomly suspended in a clear adhesive matrix. For verification of a tag's authenticity, an illumination/imaging system is used to "read" information about precise positions and orientations of faceted particles. SNL developed the original Reflective Particle Tag (RPT) system, comprising a tag and an imager, in the 1990's to identify treaty-accountable items. Since then, the RPT system has evolved with advances in computing, imaging, and materials, and is considered a robust, low-cost, hard-to-counterfeit passive tagging system for treaty verification. However, a limitation of the current system is the need to mechanically dock the reader with the tag, which prevents its use in many situations. This paper discusses R&D at SNL to develop a non-contact handheld imaging system that will allow RPT system use in new scenarios and allows automation.
Current technology cuts solar Si wafers by a wire saw process, resulting in 50% 'kerf' loss when machining silicon from a boule or brick into a wafer. We want to develop a kerf-free laser wafering technology that promises to eliminate such wasteful wire saw processes and achieve up to a ten-fold decrease in the g/W{sub p} (grams/peak watt) polysilicon usage from the starting polysilicon material. Compared to today's technology, this will also reduce costs ({approx}20%), embodied energy, and green-house gas GHG emissions ({approx}50%). We will use short pulse laser illumination sharply focused by a solid immersion lens to produce subsurface damage in silicon such that wafers can be mechanically cleaved from a boule or brick. For this concept to succeed, we will need to develop optics, lasers, cleaving, and high throughput processing technologies capable of producing wafers with thicknesses < 50 {micro}m with high throughput (< 10 sec./wafer). Wafer thickness scaling is the 'Moore's Law' of silicon solar. Our concept will allow solar manufacturers to skip entire generations of scaling and achieve grid parity with commercial electricity rates. Yet, this idea is largely untested and a simple demonstration is needed to provide credibility for a larger scale research and development program. The purpose of this project is to lay the groundwork to demonstrate the feasibility of laser wafering. First, to design and procure on optic train suitable for producing subsurface damage in silicon with the required damage and stress profile to promote lateral cleavage of silicon. Second, to use an existing laser to produce subsurface damage in silicon, and third, to characterize the damage using scanning electron microscopy and confocal Raman spectroscopy mapping.
Sandia National Laboratories has developed a means of manufacturing high precision aspheric lenslet arrays turned on-center. An innovative chucking and indexing mechanism was designed and implemented which allows the part to be indexed in two orthogonal directions parallel to the spindle face. This system was designed to meet a need for center to center positioning of 2μm and form error of λ/10. The part utilizes scribed orthogonal sets of grooves that locate the part on the chuck. The averaging of the grooves increases the repeatability of the system. The part is moved an integral number of grooves across the chuck by means of a vacuum chuck on a tool post that is mated to the part and holds the part while the chuck repositions to receive the part. The current setup is designed to create as many as 169 lenslets distributed over a 3mm square area while holding a true position tolerance of 1μm for all lenslets.
The LIGA microfabrication technique offers a unique method for fabricating 3-dimensional photonic lattices based on the Iowa State "logpile" structure. These structures represent the [111] orientation of the [100] logpile structures previously demonstrated by Sandia National Laboratories, The novelty to this approach is the single step process that does not require any alignment. The mask and substrate are fixed to one another and exposed twice from different angles using a synchrotron light source. The first exposure patterns the resist at an angle of 45 degrees normal to the substrate with a rotation of 8 degrees. The second exposure requires a 180 degree rotation about the normal of the mask and substrate. The resulting pattern is a vertically oriented logpile pattern that is rotated slightly off axis. The exposed PMMA is developed in a single step to produce an inverse lattice structure. This mold is filled with electroplated gold and stripped away to create a usable gold photonic crystal. Tilted logpiles demonstrate band characteristics very similar to those observed from [100] logpiles. Reflectivity tests show a band edge around 5 μm and compare well with numerical simulations.
The potential for electrochromic (EC) materials to be incorporated into a Fabry-Perot (FP) filter to allow modest amounts of tuning was evaluated by both experimental methods and modeling. A combination of chemical vapor deposition (CVD), physical vapor deposition (PVD), and electrochemical methods was used to produce an ECFP film stack consisting of an EC WO{sub 3}/Ta{sub 2}O{sub 5}/NiO{sub x}H{sub y} film stack (with indium-tin-oxide electrodes) sandwiched between two Si{sub 3}N{sub 4}/SiO{sub 2} dielectric reflector stacks. A process to produce a NiO{sub x}H{sub y} charge storage layer that freed the EC stack from dependence on atmospheric humidity and allowed construction of this complex EC-FP stack was developed. The refractive index (n) and extinction coefficient (k) for each layer in the EC-FP film stack was measured between 300 and 1700 nm. A prototype EC-FP filter was produced that had a transmission at 500 nm of 36%, and a FWHM of 10 nm. A general modeling approach that takes into account the desired pass band location, pass band width, required transmission and EC optical constants in order to estimate the maximum tuning from an EC-FP filter was developed. Modeling shows that minor thickness changes in the prototype stack developed in this project should yield a filter with a transmission at 600 nm of 33% and a FWHM of 9.6 nm, which could be tuned to 598 nm with a FWHM of 12.1 nm and a transmission of 16%. Additional modeling shows that if the EC WO{sub 3} absorption centers were optimized, then a shift from 600 nm to 598 nm could be made with a FWHM of 11.3 nm and a transmission of 20%. If (at 600 nm) the FWHM is decreased to 1 nm and transmission maintained at a reasonable level (e.g. 30%), only fractions of a nm of tuning would be possible with the film stack considered in this study. These tradeoffs may improve at other wavelengths or with EC materials different than those considered here. Finally, based on our limited investigation and material set, the severe absorption associated with the refractive index change suggests that incorporating EC materials into phase correcting spatial light modulators (SLMS) would allow for only negligible phase correction before transmission losses became too severe. However, we would like to emphasize that other EC materials may allow sufficient phase correction with limited absorption, which could make this approach attractive.
The ''Design and Manufacturing of Complex Optics'' LDRD sought to develop new advanced methods for the design and manufacturing of very complex optical systems. The project team developed methods for including manufacturability into optical designs and also researched extensions of manufacturing techniques to meet the challenging needs of aspherical, 3D, multi-level lenslet arrays on non-planar surfaces. In order to confirm the applicability of the developed techniques, the team chose the Dragonfly Eye optic as a testbed. This optic has arrays of aspherical micro-lenslets on both the exterior and the interior of a 4mm diameter hemispherical shell. Manufacturing of the dragonfly eye required new methods of plunge milling aspherical optics and the development of a method to create the milling tools using focused ion beam milling. The team showed the ability to create aspherical concave milling tools which will have great significance to the optical industry. A prototype dragonfly eye exterior was created during the research, and the methods of including manufacturability in the optical design process were shown to be successful as well.
In order to optically vary the magnification of an imaging system, continuous mechanical zoom lenses require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of lenses. By incorporating active elements into the optical design, we have designed and demonstrated imaging systems that are capable of variable optical magnification with no macroscopic moving parts. Changing the effective focal length and magnification of an imaging system can be accomplished by adeptly positioning two or more active optics in the optical design and appropriately adjusting the optical power of those elements. In this application, the active optics (e.g. liquid crystal spatial light modulators or deformable mirrors) serve as variable focal-length lenses. Unfortunately, the range over which currently available devices can operate (i.e. their dynamic range) is relatively small. Therefore, the key to this concept is to create large changes in the effective focal length of the system with very small changes in the focal lengths of individual elements by leveraging the optical power of conventional optical elements surrounding the active optics. By appropriately designing the optical system, these variable focal-length lenses can provide the flexibility necessary to change the overall system focal length, and therefore magnification, that is normally accomplished with mechanical motion in conventional zoom lenses.
Recent world events have underscored the need for a satellite based persistent global surveillance capability. To be useful, the satellite must be able to continuously monitor objects the size of a person anywhere on the globe and do so at a low cost. One way to satisfy these requirements involves a constellation of satellites in low earth orbit capable of resolving a spot on the order of 20 cm. To reduce cost of deployment, such a system must be dramatically lighter than a traditional satellite surveillance system with a high spatial resolution. The key to meeting this requirement is a lightweight optics system with a deformable primary and secondary mirrors and an adaptive optic subsystem correction of wavefront distortion. This proposal is concerned with development of MEMS micromirrors for correction of aberrations in the primary mirror and improvement of image quality, thus reducing the optical requirements on the deployable mirrors. To meet this challenge, MEMS micromirrors must meet stringent criteria on their performance in terms of flatness, roughness and resolution of position. Using Sandia's SUMMIT foundry which provides the world's most sophisticated surface MEMS technology as well as novel designs optimized by finite element analysis will meet severe requirements on mirror travel range and accuracy.
A figure of merit for optimization of a complete Stokes polarimeter based on its measurement matrix is described from the standpoint of singular value decomposition and analysis of variance. It is applied to optimize a system featuring a rotatable retarder and fixed polarizer, and to study the effects of non-ideal retarder properties. A retardance of 132{degree} (approximately three-eighths wave) and retarder orientation angles of {+-}51.7{degree} and {+-}15.1{degree} are favorable when four measurements are used. An achromatic, form-birefringent retarder for the 3--5 {micro}m spectral region has been fabricated and characterized. The effects of non-idealities in the form-birefringent retarder are moderate, and performance superior to that of a quarter-wave plate is expected.
The authors describe the microfabrication of a multi-level diffractive optical element (DOE) onto a micro-electromechanical system (MEMS) as a key element in an integrated compact optical-MEMS laser scanner. The DOE is a four-level off-axis microlens fabricated onto a movable polysilicon shuttle. The microlens is patterned by electron beam lithography and etched by reactive ion beam etching. The DOE was fabricated on two generations of MEMS components. The first generation design uses a shuttle suspended on springs and displaced by a linear rack. The second generation design uses a shuttle guided by roller bearings and driven by a single reciprocating gear. Both the linear rack and the reciprocating gear are driven by a microengine assembly. The compact design is based on mounting the MEMS module and a vertical cavity surface emitting laser (VCSEL) onto a fused silica substrate that contains the rest of the optical system. The estimated scan range of the system is {+-}4{degree} with a spot size of 0.5 mm.
This report represents the completion of a three-year Laboratory-Directed Research and Development (LDRD) program to investigate combining microelectromechanical systems (MEMS) with optoelectronic components as a means of realizing compact optomechanical subsystems. Some examples of possible applications are laser beam scanning, switching and routing and active focusing, spectral filtering or shattering of optical sources. The two technologies use dissimilar materials with significant compatibility problems for a common process line. This project emphasized a hybrid approach to integrating optoelectronics and MEMS. Significant progress was made in developing processing capabilities for adding optical function to MEMS components, such as metal mirror coatings and through-vias in the substrate. These processes were used to demonstrate two integration examples, a MEMS discriminator driven by laser illuminated photovoltaic cells and a MEMS shutter or chopper. Another major difficulty with direct integration is providing the optical path for the MEMS components to interact with the light. The authors explored using folded optical paths in a transparent substrate to provide the interconnection route between the components of the system. The components can be surface-mounted by flip-chip bonding to the substrate. Micro-optics can be fabricated into the substrate to reflect and refocus the light so that it can propagate from one device to another and them be directed out of the substrate into free space. The MEMS components do not require the development of transparent optics and can be completely compatible with the current 5-level polysilicon process. They report progress on a MEMS-based laser scanner using these concepts.
Grating light reflection spectroscopy (GLRS) is an emerging technique for spectroscopic analysis and sensing. A transmission diffraction grating is placed in contact with the sample to be analyzed, and an incident light beam is directed onto the grating. At certain angles of incidence, some of the diffracted orders are transformed from traveling waves to evanescent waves. This occurs at a specific wavelength that is a function of the grating period and the complex index of refraction of the sample. The intensities of diffracted orders are also dependent on the sample's complex index of refraction. The authors describe the use of GLRS, in combination with electrochemical modulation of the grating, for the detection of trace amounts of aromatic hydrocarbons. The diffraction grating consisted of chromium lines on a fused silica substrate. The depth of the grating lines was 1 {micro}m, the grating period was 1 {micro}m, and the duty cycle was 50%. Since chromium was not suitable for electrochemical modulation of the analyte concentration, a 200 nm gold layer was deposited over the entire grating. This gold layer slightly degraded the transmission of the grating, but provided satisfactory optical transparency for the spectroelectrochemical experiments. The grating was configured as the working electrode in an electrochemical cell containing water plus trace amounts of the aromatic hydrocarbon analytes. The grating was then electrochemically modulated via cyclic voltammetry waveforms, and the normalized intensity of the zero order reflection was simultaneously measured. The authors discuss the lower limits of detection (LLD) for two analytes, 7-dimethylamino-1,2-benzophenoxazine (Meldola's Blue dye) and 2,4,6-trinitrotoluene (TNT), probed with an incident HeNe laser beam ({lambda} = 543.5 nm) at an incident angle of 52.5{degree}. The LLD for 7-dimethylamino-1,2-benzophenoxazine is approximately 50 parts per billion (ppb), while the LLD for TNT is approximately 50 parts per million (ppm). The possible factors contributing to the differences in LLD for these analytes are discussed. This is the final report for a Sandia National Laboratories Laboratory Directed Research and Development (LDRD) project conducted during fiscal years 1998 and 1999 (case number 3518.190).
We have designed and assembled two generations of integrated micro-optical systems that deliver pump light and detect broadband laser-induced fluorescence in micro-fluidic chemical separation systems employing electrochromatography. The goal is to maintain the sensitivity attainable with larger, tabletop machines while decreasing package size and increasing throughput (by decreasing the required chemical volume). One type of micro-optical system uses vertical-cavity surface-emitting lasers (VCSELs) as the excitation source. Light from the VCSELs is relayed with four-level surface relief diffractive optical elements (DOEs) and delivered to the chemical volume through substrate-mode propagation. Indirect fluorescence from dye-quenched chemical species is collected and collimated with a high numerical aperture DOE. A filter blocks the excitation wavelength, and the resulting signal is detected as the chemical separation proceeds. Variations of this original design include changing the combination of reflective and transmissive DOEs and optimizing the high numerical aperture DOE with a rotationally symmetric iterative discrete on-axis algorithm. We will discuss the results of these implemented optimizations.
Polarimetry is the method of recording the state of polarization of light. Imaging polarimetry extends this method to recording the spatially resolved state of polarization within a scene. Imaging-polarimetry data have the potential to improve the detection of manmade objects in natural backgrounds. We have constructed a midwave infrared complete imaging polarimeter consisting of a fixed wire-grid polarizer and rotating form-birefringent retarder. The retardance and the orientation angles of the retarder were optimized to minimize the sensitivity of the instrument to noise in the measurements. The optimal retardance was found to be 132{degree} rather than the typical 90{degree}. The complete imaging polarimeter utilized a liquid-nitrogen cooled PtSi camera. The fixed wire-grid polarizer was located at the cold stop inside the camera dewar. The complete imaging polarimeter was operated in the 4.42-5 {micro}m spectral range. A series of imaging experiments was performed using as targets a surface of water, an automobile, and an aircraft. Further analysis of the polarization measurements revealed that in all three cases the magnitude of circular polarization was comparable to the noise in the calculated Stokes-vector components.
The authors describe the design and microfabrication of an extremely compact optical system as a key element in an integrated capillary-channel electrochromatograph with laser induced fluorescence detection. The optical design uses substrate-mode propagation within the fused silica substrate. The optical system includes a vertical cavity surface-emitting laser (VCSEL) array, two high performance microlenses and a commercial photodetector. The microlenses are multilevel diffractive optics patterned by electron beam lithography and etched by reactive ion etching in fused silica. Two generations of optical subsystems are described. The first generation design is integrated directly onto the capillary channel-containing substrate with a 6 mm separation between the VCSEL and photodetector. The second generation design separates the optical system onto its own module and the source to detector length is further compressed to 3.5 mm. The systems are designed for indirect fluorescence detection using infrared dyes. The first generation design has been tested with a 750 nm VCSEL exciting a 10{sup -4} M solution of CY-7 dye. The observed signal-to-noise ratio of better than 100:1 demonstrates that the background signal from scattered pump light is low despite the compact size of the optical system and meets the system sensitivity requirements.
A specialized hyperspectral imager has been developed that preprocesses the spectra from an image before the light reaches the detectors. This "optical computer" does not allow the flexibility of digital post-processing. However, the processing is done in real time and the system can examine = 2 x 10{sup 6} scene pixels/sec. Therefore, outdoors it could search for pollutants, vegetation types, minerals, or man-made objects. On a high- speed production line it could identify defects in sheet products like plastic wrap or film, or on painted or plastic parts. ISIS is a line scan imager. A spectrally dispersed slit image is projected on a Spatial Light Modulator. The SLM is programmed to take the inner product of the spectral intensity vector and a spectral basis vector. The SLM directs the positive and negative parts of the inner product to different linear detector arrays so the signal difference equals the inner product. We envision a system with one telescope and =4 SLMS.
We have developed a method for encoding phase and amplitude in microscopic computer-generated holograms (microtags) for security applications. Eight-by-eight-cell and 12 x 12-cell phase-only and phase-and-amplitude microtag designs has been exposed in photoresist using the extreme-ultraviolet (13.4 nm) lithography (EUVL) tool developed at Sandia National Laboratories. Using EUVL, we have also fabricated microtags consisting of 150-nm lines arranged to form 300-nm-period gratings. The microtags described in this report were designed for readout at 632.8 nm and 442 nm. The smallest microtag measures 56 {mu}m x 80 {mu}m when viewed at normal incidence. The largest microtag measures 80 by 160 microns and contains features 0.2 {mu}m wide. The microtag design process uses a modified iterative Fourier-transform algorithm to create either phase-only or phase-and-amplitude microtags. We also report on a simple and compact readout system for recording the diffraction pattern formed by a microtag. The measured diffraction patterns agree very well with predictions. We present the results of a rigorous coupled-wave analysis (RCWA) of microtags. Microtags are CD modeled as consisting of sub-wavelength gratings of a trapezoidal profile. Transverse-electric (TE) and TM readout polarizations are modeled. The objective of our analysis is the determination of optimal microtag-grating design parameter values and tolerances on those parameters. The parameters are grating wall-slope angle, grating duty cycle, grating depth, and metal-coating thickness. Optimal microtag-grating parameter values result in maximum diffraction efficiency. Maximum diffraction efficiency is calculated at 16% for microtag gratings in air and 12% for microtag gratings underneath a protective dielectric coating, within fabrication constraints. TM-microtag gratings. Finally, we suggest several additional microtag concepts, such as two-dimensional microtags and pixel-code microtags.
The optical correlator described in this report is intended to serve as an attention-focusing processor. The objective is to narrowly bracket the range of a parameter value that characterizes the correlator input. The input is a waveform collected by a satellite-borne receiver. In the correlator, this waveform is simultaneously correlated with an ensemble of ionosphere impulse-response functions, each corresponding to a different total-electron-count (TEC) value. We have found that correlation is an effective method of bracketing the range of TEC values likely to be represented by the input waveform. High accuracy in a computational sense is not required of the correlator. Binarization of the impulse-response functions and the input waveforms prior to correlation results in a lower correlation-peak-to-background-fluctuation (signal-to-noise) ratio than the peak that is obtained when all waveforms retain their grayscale values. The results presented in this report were obtained by means of an acousto-optic correlator previously developed at SNL as well as by simulation. An optical-processor architecture optimized for 1D correlation of long waveforms characteristic of this application is described. Discussions of correlator components, such as optics, acousto-optic cells, digital micromirror devices, laser diodes, and VCSELs are included.
Microtags are microscopic computer-generated holograms with 130-nm features and are mass-producible with EUVL. This fabrication method renders microtags difficult to counterfeit. Applications includ tagging and tracking of microprocessors, memory chips, currencey, and credit cards.
This report discusses a novel fabrication process to produce nearly perfect optics. The process utilizes vacuum deposition techniques to optimally modify polished optical substrate surfaces. The surface figure, i.e. contour of a polished optical element, is improved by differentially filling in the low spots on the surface using flux from a physical vapor deposition source through an appropriate mask. The process is expected to enable the manufacture of diffraction-limited optical systems for the UV, extreme UV, and soft X-ray spectral regions, which would have great impact on photolithography and astronomy. This same technique may also reduce the fabrication cost of visible region optics with aspheric surfaces.
A ``debris-less`` laser-plasma source (LPS) of extreme-UV radiation has been developed by Kubiak, et al. This is a huge step forward for the extreme-UV lithography program (EUVL) because it will extend the life of the collecting mirrors that face the source. This source has a 300-{mu}m diameter (D source) which is larger than the earlier, {approximately}75-{mu}m diameter plasma balls created on metal targets. The larger source size requires that the Etendu of the system must also be larger if the source radiation is to be used efficiently. A family of 4-mirror, scanning, ring-field lithography cameras has been designed that can be efficiently coupled to a ``debris-less`` LPS. The most promising design has a 0.085-numerical aperture (NA{sub camera}) for printing {approx} 100-nm features. At the image plane it has 13 nm of distortion and a 98% Strehl ratio across its 7-mm wide ring-field ({Delta}r).
Scanning, ring-field lithographic cameras designed for 14-nm radiation can print 100-nm features on large chips. Mating high-efficiency illuminators are described.