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Spatial filter issues

Description: Experiments and calculations indicate that the threshold pressure in spatial filters for distortion of a transmitted pulse scales approximately as I{sup O.2} and (F{number_sign}){sup 2} over the intensity range from 10{sup 14} to 2xlO{sup 15} W/CM{sup 2} . We also demonstrated an interferometric diagnostic that will be used to measure the scaling relationships governing pinhole closure in spatial filters.
Date: December 9, 1996
Creator: Murray, J.E.; Estabrook, K.G.; Milam, D.; Sell, W.D.; Van Wonterghem, R.M.; Feil, M.D. et al.
Partner: UNT Libraries Government Documents Department

Frequency Selective Volumes for Optical Spatial Filters

Description: A new model is proposed for modeling metallic losses at optical frequencies and is used in the analysis of Frequency Selective Surfaces (FSSs) and Volumes (FSVs). Conventional methods for simulating metallic losses are also outlined and a comparison with those models is given for a patch FSS. Measured data for a slot-ring FSS are also given for model validation.
Date: April 15, 2004
Creator: Topsakal, E & Volakis, JL
Partner: UNT Libraries Government Documents Department

Kalman filtering to suppress spurious signals in Adaptive Optics control

Description: In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.
Date: March 29, 2010
Creator: Poyneer, L & Veran, J P
Partner: UNT Libraries Government Documents Department

The oxide defined VCSEL-based smart pixels for the optical database filter

Description: This paper presents the construction of the smart pixel arrays which perform AND and XOR functions with three-input and one-output optical signals for the application of an optical database filter. The device is based on oxide confined VCSELs bump bonded to GaAs MESFET pixels. The MSM photodetectors are monolithically integrated with MESFETs.
Date: April 1, 1997
Creator: Pu, R.; Hayes, E.; Jurrat, R.; Stanko, P.J.; Wilmsen, C.W.; Choquette, K. et al.
Partner: UNT Libraries Government Documents Department

Spatial filter lens design for the main laser of the National Ignition Facility

Description: The National Ignition Facility 0, being designed and constructed at Lawrence Livermore National Laboratory (LLNL), comprises 192 laser beams. The lasing medium is neodymium in phosphate glass with a fundamental frequency (Ice) of 1.053~. Sum frequency generation in a pair of conversion crystals (KDP/KD*P) will produce 1.8 megajoules of the third harmonic light (30 or bO.351~) at the target. The purpose of this paper is to provide the lens design community with the current lens design details of the large powered optics in the Main Laser. This paper describes the lens design configuration and design considerations of the Main Laser. The Main Laser is 123 meters long and includes two spatial tllters: one 23.5 meters and one 60 meters. These spatial filters perform crucial beam filtering and relaying functions. We shall describe the significant lens design aspects of these spatial tilter lenses which allow them to successfully deliver the appropriate beam characteristic onto the target. For a broad overview of NIF. please see, �Optical system design of the National Ignition Facility,� by R. Edward English, et al, also found in this volume.
Date: June 26, 1998
Creator: English, R E; Korniski, R J & Miller, J L
Partner: UNT Libraries Government Documents Department

An improved pinhole spatial filter

Description: Lasers generate phase aberrated light that can damage laser glass, frequency conversion crystals, lenses, and mirror coatings and can also reduce extractable energy and power. Spatial pinhole filters can partly eliminate such ``hot spots.`` Problems are that the pinhole closes during the laser pulse and has to be made too large initially. Debris from the pinhole can coat or damage spatial filter lenses. This paper presents a novel design for a more robust pinhole filter. Phase distorted (hot spot) light refracts at grazing incidence by plasma on the wall of a funnel shaped filter resulting in less absorption and debris. Refracted light absorbs at low intensities on the vacuum wall. We present 2D hydrodynamic computer simulations and compare the two types of filters with experiment.
Date: August 21, 1996
Creator: Estabrook, K.; Celliers, P.; Murray, J.; Wallace, R.; Stone, G.; Van Wonterghem, B. et al.
Partner: UNT Libraries Government Documents Department

Subwavelength structured narrow-band integrated optical grating filters

Description: A unique type of narrow band integrated optical filter is investigated based on embedding a subwavelength resonant grating structure within a planar waveguide. Current integrated narrow-band optical filters are limited by their size, density of devices that can be produced, overall performance, and ability to be actively altered for tuning and modulation purposes. In contrast, the integrated optical filters described in this work can have extremely narrow bandwidths--on the order of a few angstroms. Also, their compact size enables multiple filters to be integrated in a single high density device for signal routing or wavelength discrimination. Manipulating any of the resonant structure`s parameters will tune the output response of the filter, which can be used for modulation or switching applications.
Date: January 1, 1998
Creator: Grann, E.B.; Holcomb, D.E.; Zuhr, R.A. & Moharam, M.G.
Partner: UNT Libraries Government Documents Department

Three-Dimensional Silicon Photonic Lattice

Description: Silicon processing techniques were used to fabricate 3-D photonic lattices with band gaps in the infrared. The demonstration vehicle was a selective infrared mirror/band pass filter, a wide range of other applications are also possible.
Date: November 30, 1998
Creator: Fleming, J.G. & Lin, S.
Partner: UNT Libraries Government Documents Department

MTI Focal Plane Assembly Design and Performance

Description: The focal plane assembly for the Multispectral Thermal Imager (MTI) consists of sensor chip assemblies, optical filters, and a vacuum enclosure. Sensor chip assemblies, composed of linear detector arrays and readout integrated circuits, provide spatial resolution in the cross-track direction for the pushbroom imager. Optical filters define 15 spectral bands in a range from 0.45 {micro}m to 10.7 {micro}m. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. Three pairs of sensor chip assemblies (SCAs) are required to provide cross-track coverage in all 15 spectral bands. Each pair of SCAs includes detector arrays made from silicon, iridium antimonide, and mercury cadmium telluride. Read out integrated circuits multiplex the signals from the detectors to 18 separate video channels. Optical filter assemblies defining the spectral bands are mounted over the linear detector arrays. Each filter assembly consists of several filter strips bonded together side-by-side. The MTI focal plane assembly has been integrated with the rest of the payload and has undergone detailed testing and calibration. This paper includes representative test data for the various spectral bands and the overall performance of the focal plane assembly.
Date: June 17, 1999
Creator: Ballard, M. & Rienstra, J.L.
Partner: UNT Libraries Government Documents Department

Review of window and filter requirements for commissioning of the Advanced Photon Source insertion device beamlines

Description: The Advanced Photon Source (APS) is building 16 insertion device (ID) front ends for the first phase of the project. Eleven of these are to be equipped with the APS Undulator A and the other five with a Wiggler-A-type source. The Undulator A front ends are designed to operate in a ``windowless`` mode using an APS-designed differential pump. However, during beamline commissioning and early operations of the storage ring, it is prudent to install windows to ensure storage ring vacuum safety before easing into windowless operation. However, the window designed for this interim period may not meet all the needs of a user`s scientific program. In the early phases of the project through commissioning and start of operations, such a window will permit the user to prepare for his program, while allowing both the user and the facility operators to gain experience for safe phasing into eventual windowless operations. In this report, we will present analysis and design options for a variety of windows particularly suited to either the APS Undulator A front ends or as user windows located in the first optics enclosure (FOE).
Date: June 2, 1994
Creator: Kuzay, T.M. & Wang, Zhibi
Partner: UNT Libraries Government Documents Department

Transient radiation-induced absorption in materials for the DOI laser

Description: This is the final report on a series of experiments concerned with transient radiation-induced absorption in materials for a Cr,Nd:GSGG laser. Both the Sandia National Laboratories SPR III pulsed reactor and the Hermes III pulsed X-ray machine are used as radiation sources. The time dependence and the magnitude of the induced absorption in filter glasses and in doped and undoped LiNbO{sub 3} Q-switch materials have been measured. Gain has been observed in Cr,Nd:GSGG, the laser medium, when it is irradiated by X-rays.
Date: January 1, 1995
Creator: Brannon, P. J.
Partner: UNT Libraries Government Documents Department

Polarization-independent WDM channel dropping filters

Description: We show how polarization-independent wavelength filters can be realized using asymmetric directional couplers. Simulations demonstrate that excellent polarization behavior can be achieved with practical tolerances without sacrificing filter bandwidth or insertion loss.
Date: February 1, 1994
Creator: Deri, R. J.; Patterson, F. G. & Dijaili, S. P.
Partner: UNT Libraries Government Documents Department

False color viewing device

Description: This invention consists of a viewing device for observing objects in near-infrared false-color comprising a pair of goggles with one or more filters in the apertures, and pads that engage the face for blocking stray light from the sides so that all light reaching, the user`s eyes come through the filters. The filters attenuate most visible light and pass near-infrared (having wavelengths longer than approximately 700 nm) and a small amount of blue-green and blue-violet (having wavelengths in the 500 to 520 nm and shorter than 435 nm, respectively). The goggles are useful for looking at vegetation to identify different species and for determining the health of the vegetation, and to detect some forms of camouflage.
Date: May 8, 1991
Creator: Kronberg, J. W.
Partner: UNT Libraries Government Documents Department

SNAP Satellite Focal Plane Development

Description: The proposed SuperNova/Acceleration Probe (SNAP) mission will have a two-meter class telescope delivering diffraction-limited images to an instrumented 0.7 square degree field in the visible and near-infrared wavelength regime. The requirements for the instrument suite and the present configuration of the focal plane concept are presented. A two year R&D phase, largely supported by the Department of Energy, is just beginning. We describe the development activities that are taking place to advance our preparedness for mission proposal in the areas of detectors and electronics.
Date: July 7, 2003
Creator: Bebek, C.; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Baltay, C. et al.
Partner: UNT Libraries Government Documents Department

Video Monitoring and Control of the LENS Process

Description: The LENS (Laser Engineered Net Shaping) process has significant potential impact to the manufacturing community in producing near-net shape rapid prototypes, tooling and customized small lot parts. LEINS has its roots in stereolithography and weld surfacing. Parts are built up in layers by delivering powder carried in an inert gas stream directed via nozzles to a laser-produced molten pool. A robust implementation of this technology requires a thorough understanding of how the thermal history during part fabrication influences the dimensions, microstructure and properties of the part. This understanding, in combination with effective closed loop feedback control of the process, and modeling of the part to be formed, is required to ensure routine fabrication of components with appropriate properties Thermal behavior at high temperatures (above 800 C) can be readily monitored by visible light radiation pyrometry. In this work a high speed digital camera with a narrow bandpass optical filter was used to obtain thermal images of the LENS process zone. The thermal imaging system was incorporated into the optical path of the laser so that the melt pool and adjacent areas of the part could be monitored without intrusive hardware add-ens at the lens/powder nozzle/process zone vicinity. The output of the digital camera was collected by a fiarne grabber card in a personal computer (PC). Characteristics of the melt pool were evaluated and then used as inputs to a Proportional-Integral-Derivative (PID) control algorithm also running on the PC. The output of the PID algorithm was then used to control the laser power. Running the closed loop control resulted in significant stabilization of the melt pool size during simulated fabrication experiments. We will describe the equipment, algorithms, experiments and results obtained from LENS-formed simple shapes of 316 Stainless Steel.
Date: November 30, 1999
Creator: HOFMEISTER,WILLIAM; KNOROVSKY,GERALD A. & MACCALLUM,DANNY O.
Partner: UNT Libraries Government Documents Department

Photochemical coal dissolution. Quarterly technical progress report, October 1, 1995--December 31, 1995

Description: The remaining types of photochemical extraction experiments originally proposed have now been examined. Experiments in which benzophenone (BP) in solution was employed as a photochemical extraction reagent on pre-extracted coals were performed with Hg arc light through a quartz light filter at a concentration permitting light absorption primarily by the coal. Experiments were done on pre-extracted coals in which tetralin was employed as the photochemical extraction reagent. Finally experiments were performed in which the pre-extracted coal was swelled with BP above its melting point, irradiated through a quartz filter and extracted. The solvent was acetonitrile in all cases.
Date: May 1, 1996
Creator: Doetschman, D.C.
Partner: UNT Libraries Government Documents Department

Multispectral Focal Plane Assembly for Satellite Remote Sensing

Description: Sandia National Laboratories and several subsystem contractors are developing technologies applicable to multispectral remote sensing from space. A proof of concept multispectral sensor system is under development. The objective of building this sensor is to demonstrate and evaluate multispectral imaging technologies for various applications. The three major subsystems making up the sensor are the focal plane assembly (FPA), the cryocooler, and the telescope. This paper covers the focal plane assembly, which is the basis of the sensor system. The focal plane assembly includes sensor chip assemblies, optical filters, and a vacuum enclosure with cold shielding. Linear detector arrays provide spatial resolution in the cross-track direction for a pushbroom imager configuration. The optical filters define 15 spectral bands in a range from 0.45 microns to 10.7 microns. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. No beam splitters are used. The four spectral bands covering the visible to near infrared have roughly 2400 pixels each, and the remaining 11 spectral bands have roughly 600 pixels each. The average total rate of multispectral data from the FPA is approximately 15.4 megapixels per second. At the time this paper is being written, the multispectral focal plane assembly is in the fabrication phase. A thermal/mechanical mockup has been built and tested for the vibration environment and to determine the thermal load. Some of the sensor chip assemblies and filters have been built and tested. Several notable features of the design are covered in the paper as well as preliminary test data.
Date: December 31, 1997
Creator: Rienstra, J. & Ballard, M.
Partner: UNT Libraries Government Documents Department

Beam control and diagnostic functions in the NIF transport spatial filter

Description: Beam control and diagnostic systems are required to align the National Ignition Facility (NIF) laser prior to a shot as well as to provide diagnostics on 192 beam lines at shot time. A design that allows each beam`s large spatial filter lenses to also serve as objective lenses for beam control and diagnostic sensor packages helps to accomplish the task at a reasonable cost. However, this approach also causes a high concentration of small optics near the pinhole plane of the transport spatial filter (TSF) at the output of each beam. This paper describes the optomechanical design in and near the central vacuum vessel of the TSF.
Date: October 1, 1996
Creator: Holdener, F.R.; Ables, E. & Bliss, E.S.
Partner: UNT Libraries Government Documents Department

Transformation of filter transmission data for f-number and chief ray angle

Description: This paper describes a method for transforming measured optical and infrared filter data for use with optical systems of arbitrary f-number and angle of incidence. Although it is generally desirable to have normal incidence at the filter (i.e., collimated light where an optical filter is used), other system design considerations may take precedence. In the case of a multispectral sensor under development at Sandia National Laboratories, system constraints require optical filter placement very near the focal plane. The light rays incident on the filters are therefore converging as determined by the system f-number while the chief ray of each ray bundle varies with focal plane position. To analyze the system`s spectral response at different points on the focal plane, a method was devised to transform the filter vendor`s measured data to account for the optical system design. The key to the transformation is the determination of weighting factors and shift factors for each angle of incidence making up a ray bundle. A computer worksheet was developed using a popular mathematical software package which performs this transformation for 75 key points on the focal plane.
Date: March 1, 1998
Creator: Rienstra, J.L.
Partner: UNT Libraries Government Documents Department

Subcarrier multiplexing system with built-in dispersion reduction

Description: Dispersion is effectively reduced in a 1550-nm subcarrier-multiplexed fiber link by using optical pre-filtering at the receiver. Recent experimental results demonstrate transmission of two 2.5 Gbit/s data channels over 220 km of ordinary single-mode fiber.
Date: September 8, 1995
Creator: Sargis, P.D.; Haigh, R.E. & McCammon, K.G.
Partner: UNT Libraries Government Documents Department

Fringe Pattern of the PEP-II Synchrotron-Light Interferometers

Description: Synchrotron-light interferometry is used to measure the vertical beam sizes in the high-energy and low-energy rings (HER and LER) of the PEP-II B Factory at SLAC. Light from a point in a dipole magnet is diffracted by two slits and then imaged onto a CCD camera. A curve fitting algorithm matches the measured interference fringes to a calculated pattern that includes the effect on the modulation depth of the fringes due to both the small but nonzero source size and the narrow bandpass of the optical filter. These formulas are derived here. Next, an additional focusing term from the primary mirror in the vacuum chamber is considered. The mirror needs extensive cooling due to the intense fan of synchrotron x-rays and is likely to have a slight stress-induced curvature, which must be considered to determine the true source size.
Date: September 19, 2005
Creator: Fisher, Alan
Partner: UNT Libraries Government Documents Department

Characteristics of degenerately doped silicon for spectral control in thermophotovoltaic systems

Description: Heavily doped Si was investigated for use as spectral control filter in thermal photovoltaic (TPV) system. These filters should reflect radiation at 4 {micro}m and above and transmit radiation at 2 {micro}m and below. Two approaches have been used for introducing impurities into Si to achieve high doping concentration. One was the diffusion technique, using spin-on dopants. The plasma wavelength ({lambda}{sub p}) of these filters could be adjusted by controlling the diffusion conditions. The minimum plasma wavelength achieved was 4.8 {micro}m. In addition, a significant amount of absorption was observed for the wavelength 2 {micro}m and below. The second approach was doping by ion implantation followed by thermal annealing with a capped layer of doped glass. Implantation with high dosage of B and As followed by high temperature annealing (> 1,000 C) resulted in a plasma wavelength that could be controlled between 3.5 and 6 {micro}m. The high temperature annealing (> 1,000 C) that was necessary to activate the dopant atoms and to heal the implantation damage, also caused significant absorption at 2 {micro}m. For phosphorus implanted Si, a moderate temperature (800--900 C) was sufficient to activate most of the phosphorus and to heal the implantation damage. The position of the plasma turn-on wavelength for an implantation dose of 2 {times} 10{sup 16} cm{sup {minus}2} of P was at 2.9 {micro}m. The absorption at 2 {micro}m was less than 20% and the reflection at 5 {micro}m was about 70%.
Date: July 1, 1995
Creator: Ehsani, H.; Bhat, I.; Borrego, J.; Gutmann, R.; Brown, E.; Dzeindziel, R. et al.
Partner: UNT Libraries Government Documents Department

Transient radiation effects in D.O.I. optical materials: Schott filter glass

Description: Department of Energy and Defense Programs systems are becoming increasingly reliant on the use of optical technologies that must perform under a range of ionizing radiation environments. In particular, the radiation response of materials under consideration for applications in direct optical initiation (D.O.I.) schemes must be well characterized. In this report, transient radiation effects observed in Schott filter glass S-7010 are characterized. Under gamma exposure with 2 MeV photons in a 20--30 nsec pulse, the authors observe strong initial induced fluorescence in the red region of the spectrum followed by significant induced absorption over the same spectral region. Peak induced absorption coefficients of 0.113 cm{sup {minus}1} and 0.088 cm{sup {minus}1} were calculated at 800 nm and 660 nm respectively.
Date: July 1, 1998
Creator: Simmons-Potter, K.
Partner: UNT Libraries Government Documents Department