Publications

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We present the design, fabrication, and characterization of a pixelated, hyperspectral arrayed component for Focal Plane Array (FPA) integration in the Long-Wave IR. This device contains tens of pixels within a single super-pixel which is tiled across the extent of the FPA. Each spectral pixel maps to a single FPA pixel with a spectral FWHM of 200nm. With this arrayed approach, remote sensing data may be accumulated with a non-scanning, "snapshot" imaging system. This technology is flexible with respect to individual pixel center wavelength and to pixel position within the array. Moreover, the entire pixel area has a single wavelength response, not the integrated linear response of a graded cavity thickness design. These requirements bar tilted, linear array technologies where the cavity length monotonically increases across the device. © 2010 Copyright SPIE - The International Society for Optical Engineering.

For practical quantum computing, it will be necessary to detect the fluorescence from many trapped ions. We describe a design and integration approach using microoptics to couple this fluorescence into an array of optical fibers. © 2010 Optical Society of America.

For practical quantum computing, it will be necessary to detect the fluorescence from many trapped ions. We describe a design and integration approach using micro-optics to couple this fluorescence into an array of optical fibers.

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In this work, we describe the most recent progress towards the device modeling, fabrication, testing and system integration of active resonant subwavelength grating (RSG) devices. Passive RSG devices have been a subject of interest in subwavelength-structured surfaces (SWS) in recent years due to their narrow spectral response and high quality filtering performance. Modulating the bias voltage of interdigitated metal electrodes over an electrooptic thin film material enables the RSG components to act as actively tunable high-speed optical filters. The filter characteristics of the device can be engineered using the geometry of the device grating and underlying materials. Using electron beam lithography and specialized etch techniques, we have fabricated interdigitated metal electrodes on an insulating layer and BaTiO3 thin film on sapphire substrate. With bias voltages of up to 100V, spectral red shifts of several nanometers are measured, as well as significant changes in the reflected and transmitted signal intensities around the 1.55um wavelength. Due to their small size and lack of moving parts, these devices are attractive for high speed spectral sensing applications. We will discuss the most recent device testing results as well as comment on the system integration aspects of this project. © 2010 Copyright SPIE - The International Society for Optical Engineering.

We will present results of the design, operation, and performance of surface ion micro-traps fabricated at Sandia. Recent progress in the testing of the micro-traps will be highlighted, including successful motional control of ions and the validation of simulations with experiments.

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Plasmonic structures open up new opportunities in photonic devices, sometimes offering an alternate method to perform a function and sometimes offering capabilities not possible with standard optics. In this LDRD we successfully demonstrated metal coatings on optical surfaces that do not adversely affect the transmission of those surfaces at the design frequency. This technology could be applied as an RF noise blocking layer across an optical aperture or as a method to apply an electric field to an active electro-optic device without affecting optical performance. We also demonstrated thin optical absorbers using similar patterned surfaces. These infrared optical antennas show promise as a method to improve performance in mercury cadmium telluride detectors. Furthermore, these structures could be coupled with other components to lead to direct rectification of infrared radiation. This possibility leads to a new method for infrared detection and energy harvesting of infrared radiation.

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Conductive polymers have become an extremely useful class of materials for many optical applications. We have developed an electrochemical growth method for depositing highly conductive ({approx}100 S/cm) polypyrrole. Additionally, we have adapted advanced fabrication methods for use with the polypyrrole resulting in gratings with submicron features. This conductive polymer micro-wire grid provides an optical polarizer with unique properties. When the polymer is exposed to ionizing radiation, its conductivity is affected and the polarization properties of the device, specifically the extinction ratio, change in a corresponding manner. This change in polarization properties can be determined by optically interrogating the device, possibly from a remote location. The result is a passive radiation-sensitive sensor with very low optical visibility. The ability to interrogate the device from a safe standoff distance provides a device useful in potentially dangerous environments. Also, the passive nature of the device make it applicable in applications where external power is not available. We will review the polymer deposition, fabrication methods and device design and modeling. The characterization of the polymer's sensitivity to ionizing radiation and optical testing of infrared polarizers before and after irradiation will also be presented. These experimental results will highlight the usefulness of the conductive infrared polarizer to many security and monitoring applications.

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We investigate the advantages of employing a fiber faceplate in a snapshot polarimetry system. Our previous work at Sandia National Laboratories indicates that diffraction and propagation between the micropolarizer array, the micro-waveplate array, and the Focal Plane Array (FPA) degrade performance, as quantified by the extinction ratio1,2. Crosstalk between adjacent pixels due to diffraction increases uncertainty of the measured polarization states in a scene of interest. These issues are exacerbated in the long-wavelength regime and as FPA pixel dimensions decrease. One solution, since it minimizes propagation distance, is to construct the micropolarizer and micro-waveplate arrays on a single substrate surface and to place this combination on the FPA3. This solution is a significant fabrication challenge and decreases yield due to its serial assembly nature. An alternative solution that would improve yield is to fabricate the micropolarizer on top of a fiber faceplate, place the faceplate on the FPA with the micropolarizer facing away, then place the waveplate array on top of the micropolarizer. The optical field that passes through the plane of the microwaveplate array and the micropolarizer array is guided to the FPA plane, without suffering diffraction effects associated with free-space propagation. We will quantify the utility of these proposed configurations with predicted imaging polarimetric system extinction ratios.

Conductive polymers have become an extremely useful class of materials for many optical applications. We have developed an electrochemical growth method for depositing highly conductive (~100 S/cm) polypyrrole. Additionally, we have adapted advanced fabrication methods for use with the polypyrrole resulting in gratings with submicron features. This conductive polymer micro-wire grid provides an optical polarizer with unique properties. When the polymer is exposed to ionizing radiation, its conductivity is affected and the polarization properties of the device, specifically the extinction ratio, change in a corresponding manner. This change in polarization properties can be determined by optically interrogating the device, possibly from a remote location. The result is a passive radiation-sensitive sensor with very low optical visibility. The ability to interrogate the device from a safe standoff distance provides a device useful in potentially dangerous environments. Also, the passive nature of the device make it applicable in applications where external power is not available. We will review the polymer deposition, fabrication methods and device design and modeling. The characterization of the polymer's sensitivity to ionizing radiation and optical testing of infrared polarizers before and after irradiation will also be presented. These experimental results will highlight the usefulness of the conductive infrared polarizer to many security and monitoring applications.

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We present simulations and measurements of a technology that can manipulate thermal angular and wavelength emission. This work is representative of Sandia National Laboratories' efforts to investigate advanced technologies that are not currently accessible for reasons such as risk, cost, or limited availability. The goal of this project is to demonstrate a passive thermal emission management surface that can tailor the direction of emission as well as the wavelength bands of emission. This new proposed technology enables thermal emission pattern management by structuring the surface. This structuring may be in either the lateral or depth dimension. A lateral structuring consists of a shallow grating on a metal surface. This air/metal interface allows photon/plasmon coupling, which has been shown to coherently and preferentially emit at certain wavelengths.

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Remote detection of radiation is a difficult problem due to the 1/r 2 fall-off Recent advances in polymer research and nanoscale fabrication methods along with advances in optical Polarimetrie remote sensing systems suggest a solution. The basic device uses a micro-wiregrid infrared polarizer fabricated in conductive polymer. When the polymer is exposed to hard radiation, its conductivity will be affected and the polarization properties of the device will change in a corresponding manner. This change in polarization properties can be determined by optically interrogating the device, possibly from a remote location. We will report on the development of a radiation-sensitive passive dosimeter polymer with very low optical visibility. Progress on material development, lithographic fabrication and optical characterization will be presented.

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We developed techniques to design higher efficiency diffractive optical elements (DOEs) with large numerical apertures (NA) for quantum computing and quantum information processing. Large NA optics encompass large solid angles and thus have high collection efficiencies. Qubits in ion trap architectures are commonly addressed and read by lasers1. Large-scale ion-trap quantum computing2 will therefore require highly parallel optical interconnects. Qubit readout in these systems requires detecting fluorescence from the nearly isotropic radiation pattern of single ions, so efficient readout requires optical interconnects with high numerical aperture. Diffractive optical element fabrication is relatively mature and utilizes lithography to produce arrays compatible with large-scale ion-trap quantum computer architectures. The primary challenge of DOEs is the loss associated with diffraction efficiency. This is due to requirements for large deflection angles, which leads to extremely small feature sizes in the outer zone of the DOE. If the period of the diffractive is between λ (the free space wavelength) and 10λ, the element functions in the vector regime. DOEs in this regime, particularly between 1.5λ and 4λ, have significant coupling to unwanted diffractive orders, reducing the performance of the lens. Furthermore, the optimal depth of the zones with periods in the vector regime differs from the overall depth of the DOE. We will present results indicating the unique behaviors around the 1.5λ and 4λ periods and methods to improve the DOE performance.

We present the design and initial fabrication for a wavelength-agile, high-speed modulator that enables a long-term vision for the THz Scannerless Range Imaging (SRI) sensor. This modulator takes the place of the currently utilized SRI micro-channel plate which is limited to photocathode sensitive wavelengths (primarily in the visible and near-IR regimes). The new component is an active Resonant Subwavelength Grating (RSG). An RSG functions as an extremely narrow wavelength and angular band reflector, or mode selector. Theoretical studies predict that the infinite, laterally-extended RSG can reflect 100% of the resonant light while transmitting the balance of the other wavelengths. Previous experimental realization of these remarkable predictions has been impacted primarily by fabrication challenges. Even so, we have demonstrated large-area (1.0mm) passive RSG reflectivity as high as 100.2%, normalized to deposited gold. In this work, we transform the passive RSG design into an active laser-line modulator.