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Sample records for echelle gratings

  1. Groove shape characteristics of echelle gratings with high diffraction efficiency

    NASA Astrophysics Data System (ADS)

    Zhang, Shanwen; Mi, Xiaotao; Zhang, Qian; Jirigalantu; Feng, Shulong; Yu, Haili; Qi, Xiangdong

    2017-03-01

    The groove shape characteristics of echelle gratings with high diffraction efficiency are investigated. Using the coordinate transformation method (C method), an r-2 aluminum echelle with 79 grooves/mm is optimized through rigorous numerical simulations and shows high diffraction efficiency of 76-81% in the high Littrow orders. A grating is found to be essentially an echelle if it contains a series of reflective facets with a specific tilt angle that are located far from the nonworking facet of the grating and have a deep groove depth; any groove shape that meets these conditions can be called an echelle grating. The underlying mechanism is analyzed phenomenologically using electromagnetic theory. The universal model proposed here, which represents a new cognitive understanding of the concept of the echelle, is ready for use in manufacturing applications and offers a new perspective for the fabrication of these gratings.

  2. Cooled echelle grating spectrometer. [for space telescope applications

    NASA Technical Reports Server (NTRS)

    Beer, R. (Inventor)

    1980-01-01

    A cooled echelle grating spectrometer for detecting wavelengths between one micron and fifteen microns is disclosed. More specifically, the spectrometer has a cross-dispersing grating for ordering infrared energy and an echelle grating for further ordering of the infrared energy. Ordered radiation from the echelle grating is sensed by a detecting means. Also disclosed is use of a Schmidt camera for focusing the further ordered radiation from the echelle grating onto a detector array having individual detectors dispersed on a plane which substantially corresponds to a curved focal plane of the Schmidt camera. A spectrometer constructed according to the teachings of the present invention will continuously cover the spectrum between one micron and fifteen microns and have a resolution of 0.1/cm.

  3. An echelle diffraction grating for imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Yang, Minyue; Wang, Han; Li, Mingyu; He, Jian-Jun

    2016-09-01

    We demonstrate an echelle diffraction grating (EDG) of 17 input waveguides and 33 output waveguides. For each input waveguide, only 17 of 33 output waveguides are used, receiving light ranging from 1520 nm to 1600 nm wavelength. The channel spacing of the EDG is 5 nm, with loss of -6dB and crosstalk of -17dB for center input waveguide and -15dB for edge input waveguides. Based on the 3 μm SOI platform the device is polarization insensitive. As a simple version of EDG spectrometer it is designed to be a part of the on-chip spectroscopic system of the push-broom scanning imaging spectrometer. The whole on-chip spectrometer consists of an optical on-off switch array, a multi-input EDG and detector array. With the help of on-off switch array the multiple input waveguides of the EDG spectrometer could work in a time division multiplexed fashion. Since the switch can scan very fast (less than 10 microseconds), the imaging spectrometer can be operated in push-broom mode. Due to the CMOS compatibility, the 17_channel EDG scales 2.5×3 mm2. The full version of EDG spectrometer is designed to have 129 input waveguides and 257 output waveguides (129 output channel for each input waveguide), working in wavelength ranging from 1250 nm to 1750 nm, and had similar blazed facet size with the 17_channel one, which means similar fabrication tolerance in grating facets. The waveguide EDG based imaging spectrometer can provide a low-cost solution for remote sensing on unmanned aerial vehicles, with advantages of small size, light weight, vibration-proof, and high scalability.

  4. Echelle grating multi-order imaging spectrometer utilizing a catadioptric lens

    DOEpatents

    Chrisp, Michael P; Bowers, Joel M

    2014-05-27

    A cryogenically cooled imaging spectrometer that includes a spectrometer housing having a first side and a second side opposite the first side. An entrance slit is on the first side of the spectrometer housing and directs light to a cross-disperser grating. An echelle immersions grating and a catadioptric lens are positioned in the housing to receive the light. A cryogenically cooled detector is located in the housing on the second side of the spectrometer housing. Light from the entrance slit is directed to the cross-disperser grating. The light is directed from the cross-disperser grating to the echelle immersions grating. The light is directed from the echelle immersions grating to the cryogenically cooled detector on the second side of the spectrometer housing.

  5. Immersion grating development for the VLT high-resolution IR echelle spectrometer: status report.

    NASA Astrophysics Data System (ADS)

    Wiedemann, G.

    Infrared immersion gratings are a possible way to realize the very high-resolution option in the planned VLT IR echelle spectrograph. In addition, immersion gratings and particular aspects of their fabrication are of interest to other applications. This paper summarizes the present status of the development program.

  6. Determination of chemical concentration with a 2 dimensional CCD array in the Echelle grating spectrometer

    SciTech Connect

    Lewis, D.K.; Stevens, C.G.

    1994-11-15

    The Echelle grating spectrometer (EGS) uses a stepped Echelle grating, prisms and a folded light path to miniaturize an infrared spectrometer. Light enters the system through a slit and is spread out along Y by a prism. This light then strikes the grating and is diffracted out along X. This spreading results in a superposition of spectral orders since the grating has a high spectral range. These orders are then separated by again passing through a prism. The end result of a measurement is a 2 dimensional image which contains the folded spectrum of the region under investigation. The data lies in bands from top to bottom, for example, with wavenumber increments as small as 0.1 lying from left to right such that the right end of band N is the same as the left end of band N+1. This is the image which must be analyzed.

  7. Facet-rotated echelle grating for cyclic wavelength router with uniform loss and flat passband.

    PubMed

    Mu, Ge; Huang, Pingli; Wu, Lin; He, Jian-Jun

    2015-09-01

    A novel method for designing a cyclic echelle grating wavelength router with uniform loss and flat passband is proposed and experimentally demonstrated. A 4×4 cyclic wavelength router with a channel spacing of 400 GHz at 1550 nm wavelength band is designed and fabricated in InP. Measurement results show that the loss of 16 input-output combinations varies from 9 to 19.3 dB in a conventional design, with a nonuniformity of 10.3 dB, while the 1-dB spectral bandwidth is only 0.3 nm. By rotating angles of grating facets according to an appropriately designed distribution function, the loss nonuniformity is reduced to 1.5 dB, and a flat-top spectral response with 1 dB bandwidth of 1.0 nm is achieved simultaneously.

  8. Echelle grating for silicon photonics applications: integration of electron beam lithography in the process flow and first results

    NASA Astrophysics Data System (ADS)

    Kaschel, Mathias; Letzkus, Florian; Butschke, Jörg; Skwierawski, Piotr; Schneider, Marc; Weber, Marc

    2016-05-01

    We present the technology steps to integrate an Echelle grating in the process flow of silicon-organic hybrid (SOH) modulators or related active devices. The CMOS-compatible process flow on SOI substrates uses a mix of optical i-line lithography and electron beam lithography (EBL). High speed optical data communication depends on wavelength divisions multiplexing and de-multiplexing devices like Echelle gratings. The minimum feature sizes vary from device to device and reach down to 60 nm inside a modulator, while the total area of a single Echelle grating is up to several mm2 of unprocessed silicon. Resist patterning using a variable shape beam electron beam pattern generator allows high resolution. An oxide hard mask is deposited, patterns are structured threefold by EBL and are later transferred to the silicon. We demonstrate a 9-channel multiplexer featuring a 2 dB on-chip loss and an adjacent channel crosstalk better than -22 dB. Additionally a 45-channel Echelle multiplexer is presented with 5 dB on chip loss and a channel crosstalk better than -12 dB. The devices cover an on-chip area of only 0.08 mm2 and 0.5 mm2 with a wavelength spacing of 10.5 nm and 2.0 nm, respectively.

  9. First high-efficiency and high-resolution (R=80,000) NIR spectroscopy with high-blazed Echelle grating: WINERED HIRES modes

    NASA Astrophysics Data System (ADS)

    Otsubo, Shogo; Ikeda, Yuji; Kobayashi, Naoto; Sukegawa, Takashi; Kondo, Sohei; Hamano, Satoshi; Sameshima, Hiroaki; Fukue, Kei; Yoshikawa, Tomohiro; Nakanishi, Kenshi; Watase, Ayaka; Takenaka, Keiichi; Asano, Akira; Yasui, Chikako; Matsunaga, Noriyuki; Kawakita, Hideyo

    2016-08-01

    WINERED is a PI-type 0.9 - 1.35 μm high-resolution spectrograph developed by the Laboratory of Infrared highresolution Spectrograph (LiH) of the Koyama Astronomical Observatory at Kyoto Sangyo University, Japan. The scope of WINERED is to realize a high-resolution near-infrared (NIR) spectrograph with both wide coverage and high sensitivity. WINERED provides three observational modes called as the Wide, Hires-Y and Hires-J modes. The Wide mode simultaneously covers the z, Y and J-bands in a single exposure with R ≡ λ/Δλ = 28,000 and was commissioned for the 1.3 m Araki Telescope of Koyama Astronomical Observatory in 2013. We have been building alternative observational modes "Hires-Y" and "Hires-J", providing R = 80,000 spectra in the Y- and J-bands, respectively. There are two choices for realizing a compact spectrograph with a high spectral resolution of R ≧ 50,000: an immersion grating (IG) or a highblazed echelle grating (HBG). Investigating the availabilities of both optical devices, we selected an HBG solution for λ < 1.5 μm because can be realized with currently available technology in earlier time. The optical parameters of WINERED's HBGs are as follows: groove pitch = 90.38 μm, blaze angle = 79.32 °, and apex angle = 88°, which are determined to minimize vignetting in the optical system as well as aberrations with the spectral resolution of R = 80,000. Custom HBGs were made by CANON Inc. Because of the size the size limitation in fabrication process, we decided to use a mosaicked grating consisting of two HBGs. The alignment tolerances of the two HBGs are very tight (< 0.5 arcsec for the parallelism between grooves of the two gratings and 1.5 arcsec for the flatness between the two grating surfaces). To enable these fine alignments, we designed a grating holder with an adjustment mechanism with sub-μm positional resolution. We adapted cordierite CO-220 as the material for the grating holder, thereby reducing the misalignment generated by

  10. Echelle Blaze Shift vs. MSM Monthly Offset

    NASA Astrophysics Data System (ADS)

    Valenti, Jeff

    2002-07-01

    In the near future, monthly MSM offsets will probably be disabled for STIS echelle gratings, alleviating to some extent calibration problems associated with the monthly offsets. The data from this program will be used to improve empirical and optical models relating wavelength and blaze function shifts. These models will in turn be used to improve the calibration of archival echelle data obtained while monthly MSM offsets were enabled. The flux standard HZ43 will be observed with the E230H echelle grating at a central wavelength of 2513 Angstroms. Five exposures will be obtained, each with a different monthly offset applied to the Mode Select Mechanism {MSM}.

  11. Immersion echelle spectrograph

    DOEpatents

    Stevens, Charles G.; Thomas, Norman L.

    2000-01-01

    A small spectrograph containing no moving components and capable of providing high resolution spectra of the mid-infrared region from 2 microns to 4 microns in wavelength. The resolving power of the spectrograph exceeds 20,000 throughout this region and at an optical throughput of about 10.sup.-5 cm.sup.2 sr. The spectrograph incorporates a silicon immersion echelle grating operating in high spectral order combined with a first order transmission grating in a cross-dispersing configuration to provide a two-dimensional (2-D) spectral format that is focused onto a two-dimensional infrared detector array. The spectrometer incorporates a common collimating and condensing lens assembly in a near aberration-free axially symmetric design. The spectrometer has wide use potential in addition to general research, such as monitoring atmospheric constituents for air quality, climate change, global warming, as well as monitoring exhaust fumes for smog sources or exhaust plumes for evidence of illicit drug manufacture.

  12. Immersion echelle spectrograph

    SciTech Connect

    Stevens, C.G.; Thomas, N.L.

    2000-06-20

    A small spectrograph is disclosed containing no moving components and capable of providing high resolution spectra of the mid-infrared region from 2 microns to 4 microns in wavelength. The resolving power of the spectrograph exceeds 20,000 throughout this region and at an optical throughput of about 10{sup {minus}5}cm{sup 2}sr. The spectrograph incorporates a silicon immersion echelle grating operating in high spectral order combined with a first order transmission grating in a cross-dispersing configuration to provide a two-dimensional (2-D) spectral format that is focused onto a two-dimensional infrared detector array. The spectrometer incorporates a common collimating and condensing lens assembly in a near aberration-free axially symmetric design. The spectrometer has wide use potential in addition to general research, such as monitoring atmospheric constituents for air quality, climate change, global warming, as well as monitoring exhaust fumes for smog sources or exhaust plumes for evidence of illicit drug manufacture.

  13. Compact high-resolution spaceborne echelle grating spectrometer with acousto-optical tunable filter based order sorting for the infrared domain from 2.2 to 4.3 microm.

    PubMed

    Nevejans, Dennis; Neefs, Eddy; Van Ransbeeck, Emiel; Berkenbosch, Sophie; Clairquin, Roland; De Vos, Lieve; Moelans, Wouter; Glorieux, Stijn; Baeke, Ann; Korablev, Oleg; Vinogradov, Imant; Kalinnikov, Yuri; Bach, Benny; Dubois, Jean-Pierre; Villard, Eric

    2006-07-20

    A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.

  14. EGRAM- ECHELLE SPECTROGRAPH DESIGN AID

    NASA Technical Reports Server (NTRS)

    Dantzler, A. A.

    1994-01-01

    EGRAM aids in the design of spectrographic systems that utilize an echelle-first order cross disperser combination. This optical combination causes a two dimensional echellogram to fall on a detector. EGRAM describes the echellogram with enough detail to allow the user to effectively judge the feasibility of the spectrograph's design. By iteratively altering system parameters, the desired echellogram can be achieved without making a physical model. EGRAM calculates system parameters which are accurate to the first order and compare favorably to results from ray tracing techniques. The spectrographic system modelled by EGRAM consists of an entrance aperture, collimator, echelle, cross dispersion grating, focusing options, and a detector. The system is assumed to be free of aberrations and the echelle, cross disperser, and detector should be planar. The EGRAM program is menu driven and has a HELP facility. The user is prompted for information such as minimum and maximum wavelengths, slit dimensions, ruling frequencies, detector geometry, and angle of incidence. EGRAM calculates the resolving power and range of order numbers covered by the echellogram. A numerical map is also produced. This tabulates the order number, slit bandpass, and high/middle/low wavelengths. EGRAM can also compute the centroid coordinates of a specific wavelength and order (or vice versa). EGRAM is written for interactive execution and is written in Microsoft BASIC A. It has been implemented on an IBM PC series computer operating under DOS. EGRAM was developed in 1985.

  15. Optical Alignment and Diffraction Analysis for AIRES: An Airborne Infrared Echelle Spectrometer

    NASA Technical Reports Server (NTRS)

    Haas, Michael R.; Fonda, Mark (Technical Monitor)

    2002-01-01

    The optical design is presented for a long-slit grating spectrometer known as AIRES (Airborne InfraRed Echelle Spectrometer). The instrument employs two gratings in series: a small order sorter and a large steeply blazed echelle. The optical path includes four pupil and four field stops, including two narrow slits. A detailed diffraction analysis is performed using GLAD by Applied Optics Research to evaluate critical trade-offs between optical throughput, spectral resolution, and system weight and volume. The effects of slit width, slit length, oversizing the second slit relative to the first, on- vs off-axis throughput, and clipping at the pupil stops and other optical elements are discussed.

  16. Total reduction of distorted echelle spectrograms: an automatic procedure.

    PubMed

    Peterson, R C; Title, A M

    1975-10-01

    We describe a semiautomatic procedure for the reduction of high-dispersion echelle spectra recorded with an image tube. The spectra are traced with a computer-controlled microdensitometer that scans along the curved spectral orders. The curvature of each order is calculated approximately by a FORTRAN program from known grating and distortion parameters. A typical spectrum includes 25 orders (covering 1500 A) and is traced with a slit 0.012 A wide. To produce an atlas of intensity vs wavelength and to determine the equivalent widths of 300 lines currently require a day. We discuss the reduction procedures and time requirements in detail.

  17. WES—Weihai Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Gao, Dong-Yang; Ji, Hang-Xin; Cao, Chen; Hu, Shao-Ming; Wittenmyer, Robert A.; Hu, Zhong-Wen; Grupp, Frank; Kellermann, Hanna; Li, Kai; Guo, Di-Fu

    2016-12-01

    The Weihai Echelle Spectrograph (WES) is the first fiber-fed echelle spectrograph for astronomical observation in China. It is primarily used for chemical abundance and asteroseismology studies of nearby bright stars, as well as radial velocity (RV) detections for exoplanets. The optical design of WES is based on the widely demonstrated and well-established white-pupil concept. We describe the WES in detail and present some examples of its performance. A single exposure echelle image covers the spectral region 371-1100 nm in 107 spectral orders over the rectangular CCD. The spectral resolution R=λ /{{Δ }}λ changes from 40,600 to 57,000 through adjusting the entrance slit width from full to 2.2 pixels sampling at the fiber-exit. The limiting magnitude scales to V = 8 with a signal-to-noise ratio of more than 100 in V for an hour exposure, at the spectral resolution R ≈ 40,000 in the median seeing of 1.″7 at Weihai Observatory for the 1 m telescope. The RV measurement accuracy of WES is estimated to be <10 m s-1 in 10 months (302 days) and better than 15 m s-1 in 4.4 years (1617 days) in the recent data processing.

  18. An echelle spectrograph for middle ultraviolet solar spectroscopy from rockets.

    PubMed

    Tousey, R; Purcell, J D; Garrett, D L

    1967-03-01

    An echelle grating spectrograph is ideal for use in a rocket when high resolution is required becaus itoccupies a minimum of space. The instrument described covers the range 4000-2000 A with a resolution of 0.03 A. It was designed to fit into the solar biaxial pointing-control section of an Aerobee-150 rocket. The characteristics of the spectrograph are illustrated with laboratory spectra of iron and carbon are sources and with solar spectra obtained during rocket flights in 1961 and 1964. Problems encountered in analyzing the spectra are discussed. The most difficult design problem was the elimination of stray light when used with the sun. Of the several methods investigated, the most effective was a predispersing system in the form of a zero-dispersion double monochromator. This was made compact by folding the beam four times.

  19. New algorithms for reducing cross-dispersed echelle spectra

    NASA Astrophysics Data System (ADS)

    Piskunov, N. E.; Valenti, J. A.

    2002-04-01

    We describe advanced image processing algorithms, implemented in a data analysis package for conventional and cross-dispersed echelle spectra. Comparisons with results from other packages illustrate the outstanding quality of the new REDUCE package, particularly in terms of resulting noise level and treatment of CCD defects and cosmic ray spikes. REDUCE can be adapted relatively easily to handle a variety of instrument types, including spectrographs with prism or grating cross-dispersers, possibly fed by a fiber or image slicer, etc. In addition to reduced spectra, an accurate spatial profile is recovered, providing valuable information about the spectrograph PSF and simplifying scattered light corrections. Based on data obtained with the VLT UVES and SAAO Giraffe spectrometers.

  20. Photoelectrochemical fabrication of spectroscopic diffraction gratings, phase 2

    NASA Technical Reports Server (NTRS)

    Rauh, R. David; Carrabba, Michael M.; Li, Jianguo; Cartland, Robert F.; Hachey, John P.; Mathew, Sam

    1990-01-01

    This program was directed toward the production of Echelle diffraction gratings by a light-driven, electrochemical etching technique (photoelectrochemical etching). Etching is carried out in single crystal materials, and the differential rate of etching of the different crystallographic planes used to define the groove profiles. Etching of V-groove profiles was first discovered by us during the first phase of this project, which was initially conceived as a general exploration of photoelectrochemical etching techniques for grating fabrication. This highly controllable V-groove etching process was considered to be of high significance for producing low pitch Echelles, and provided the basis for a more extensive Phase 2 investigation.

  1. The assembly, calibration, and preliminary results from the Colorado high-resolution Echelle stellar spectrograph (CHESS)

    NASA Astrophysics Data System (ADS)

    Hoadley, Keri; France, Kevin; Nell, Nicholas; Kane, Robert; Schultz, Ted; Beasley, Matthew; Green, James; Kulow, Jen; Kersgaard, Eliot; Fleming, Brian

    2014-07-01

    The Colorado High-resolution Echelle Stellar Spectrograph (CHESS) is a far ultraviolet (FUV) rocket-borne experiment designed to study the atomic-to-molecular transitions within translucent interstellar clouds. CHESS is an objective echelle spectrograph operating at f/12.4 and resolving power of 120,000 over a band pass of 100 - 160 nm. The echelle flight grating is the product of a research and development project with LightSmyth Inc. and was coated at Goddard Space Flight Center (GSFC) with Al+LiF. It has an empirically-determined groove density of 71.67 grooves/mm. At the Center for Astrophysics and Space Astronomy (CASA) at the University of Colorado (CU), we measured the efficiencies of the peak and adjacent dispersion orders throughout the 90 - 165 nm band pass to characterize the behavior of the grating for pre-flight calibrations and to assess the scattered-light behavior. The crossdispersing grating, developed and ruled by Horiba Jobin-Yvon, is a holographically-ruled, low line density (351 grooves/mm), powered optic with a toroidal surface curvature. The CHESS cross-disperser was also coated at GSFC; Cr+Al+LiF was deposited to enhance far-UV efficiency. Results from final efficiency and reflectivity measurements of both optics are presented. We utilize a cross-strip anode microchannel plate (MCP) detector built by Sensor Sciences to achieve high resolution (25 μm spatial resolution) and data collection rates (~ 106 photons/second) over a large format (40mm round, digitized to 8k x 8k) for the first time in an astronomical sounding rocket flight. The CHESS instrument was successfully launched from White Sands Missile Range on 24 May 2014. We present pre-flight sensitivity, effective area calculations, lab spectra and calibration results, and touch on first results and post-flight calibration plans.

  2. The design of an echelle spectrometer for diffuse extreme ultraviolet/far ultraviolet astronomy

    NASA Technical Reports Server (NTRS)

    Martin, Christopher

    1986-01-01

    The novel, relatively high-resolution nebular spectrometer design presented incorporates a mechanical precollimator with an objective echelle grating that proceeds to a cross-dispensing Wadsworth configuration; the minimum feasible number of reflections is employed in order to maximize EUV sensitivity. The configuration, which is noted to be capable of yielding a comparatively large field of view for optimal diffuse emission sensitivity, is compact and employs conventionally fabricated optical components and available microchannel plate detectors. The sensitivities obtainable approach the limit stipulated by Liouville's theorem.

  3. GHRS Cycle 5 Echelle Wavelength Monitor

    NASA Astrophysics Data System (ADS)

    Soderblom, David

    1995-07-01

    This proposal defines the spectral lamp test for Echelle A. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. This proposal defines the spectral lamp test for Echelle B. It is an internal test which makes measurements of the wavelength lamp SC2. It calibrates the carrousel function, Y deflections, resolving power, sensitivity, and scattered light. The wavelength calibration dispersion constants will be updated in the PODPS calibration data base. It will be run every 4 months. The wavelengths may be out of range according to PEPSI or TRANS. Please ignore the errors.

  4. Scattered light in the STIS echelle modes

    NASA Technical Reports Server (NTRS)

    Landsman, W.; Bowers, C.

    1997-01-01

    The Space Telescope Imaging Spectrograph (STIS) echelle spectra obtained during the Early Release Observations have non-zero residuals in the cores of saturated interstellar lines, indicating the need for a scattered light correction. A rough measure of the magnitude of the needed correction shows the ratio of the interorder to the in-order flux in different echelle modes in both pre-launch calibration images of a continuum lamp source and in post-launch images of stellar continuum sources. The interorder and in-order fluxes are computed by averaging the central 200 pixels in the dispersion direction. The amount of scattered light in the interorder region rises toward shorter wavelengths for two reasons: (1) the order separation decreases toward shorter wavelengths; and (2) the amount of echelle scattering is expected to have an inverse dependence on wavelength. At the shortest wavelengths the fraction of light scattered into the interorder region can be 10% for the Near-ultraviolet-Multi-Anode Microchannel Array (NUV-MAMA) and 15% for the Far-ultraviolet-Multi-Anode Microchannel Array (FUV-MAMA).

  5. High-resolution UV echelle spectrograph for environmental sensing

    NASA Astrophysics Data System (ADS)

    Clauson, Susan L.; Christesen, Steven D.; Spencer, Kevin M.

    2004-03-01

    Resonance Raman spectroscopy is an enhanced Raman technique that can be used to selectively identify a particular analyte in complex matrices. Resonance Raman requires the excitation laser to overlap with an absorption band of the analyte of interest. Since analytes have diverse absorption spectra, dilute concentrations may be detected when resonantly enhanced. A significant portion of interesting molecules absorb only in the UV; unfortunately current UV Raman instrumentation for scientifically desirable spectral resolution is large and costly. In the area of Homeland Defense, explosives, nerve agents, amino acid residues (for toxin analysis) and nucleic acids (for DNA detection and identification of bacteria) are all enhanced using UV laser sources. EIC Laboratories has developed a more user-friendly UVRRS spectrograph that is based upon the use of an echelle grating. The spectrograph has a footprint of 7" x 11" and is capable of providing 4 cm-1 resolution over a fairly wide spectral range. The spectrograph design and spectra from analytes of particular relevance will be presented.

  6. The GMT-CFA-CARNEGIE-CATOLICA LARGE EARTH FINDER (G-CLEF): A Fiber-fed, Optical Echelle Spectrograph For The Giant Magellan Telescope

    NASA Astrophysics Data System (ADS)

    Szentgyorgyi, Andrew; Furesz, G.; Frebel, A.; Geary, J.; Evans, I.; Norton, T.; Hertz, E.; DePonte Evans, J.; Jordan, A.; Guzman, D.; Epps, H.; Barnes, S.; Crane, J.

    2011-01-01

    The GMT-CfA-Carnegie-Catolica Large Earth Finder (G-CLEF) is a fiber-fed optical echelle spectrograph in concept design study phase for first light at the Giant Magellan Telescope. G-CLEF is designed to be a multipurpose echelle spectrograph that operates in a number of modes so as to enable precision radial velocity (RV) measurements, detailed abundance studies, isotopic abundance measurements and probe the IGM and ISM at high Z. Four resolution modes are implemented with image and pupil slicing. Extremely precise RV will be achieved by vacuum enclosing the spectrograph, with advanced fiber scrambling and state-of-the-art calibrators, especially ultra stabilized etalons and possibly laser frequency combs. The optical design is a asymmetric white pupil design with two camera arms splitting the 350 nm - 950 nm passband into red and blue channels. G-CLEF will have an extremely large, mosaiced echelle grating and volume phase holograph cross dispersers.

  7. The re-flight of the Colorado high-resolution Echelle stellar spectrograph (CHESS): improvements, calibrations, and post-flight results

    NASA Astrophysics Data System (ADS)

    Hoadley, Keri; France, Kevin; Kruczek, Nicholas; Fleming, Brian; Nell, Nicholas; Kane, Robert; Swanson, Jack; Green, James; Erickson, Nicholas; Wilson, Jacob

    2016-07-01

    In this proceeding, we describe the scientific motivation and technical development of the Colorado High- resolution Echelle Stellar Spectrograph (CHESS), focusing on the hardware advancements and testing supporting the second flight of the payload (CHESS-2). CHESS is a far ultraviolet (FUV) rocket-borne instrument designed to study the atomic-to-molecular transitions within translucent cloud regions in the interstellar medium (ISM). CHESS is an objective f/12.4 echelle spectrograph with resolving power > 100,000 over the band pass 1000 - 1600 Å. The spectrograph was designed to employ an R2 echelle grating with "low" line density. We compare the FUV performance of experimental echelle etching processes (lithographically by LightSmyth, Inc. and etching via electron-beam technology by JPL Microdevices Laboratory) with traditional, mechanically-ruled gratings (Bach Research, Inc. and Richardson Gratings). The cross-dispersing grating, developed and ruled by Horiba Jobin-Yvon, is a holographically-ruled, "low" line density, powered optic with a toroidal surface curvature. Both gratings were coated with aluminum and lithium fluoride (Al+LiF) at Goddard Space Flight Center (GSFC). Results from final efficiency and reflectivity measurements for the optical components of CHESS-2 are presented. CHESS-2 utilizes a 40mm-diameter cross-strip anode readout microchannel plate (MCP) detector fabricated by Sensor Sciences, Inc., to achieve high spatial resolution with high count rate capabilities (global rates 1 MHz). We present pre-flight laboratory spectra and calibration results. CHESS-2 launched on 21 February 2016 aboard NASA/CU sounding rocket mission 36.297 UG. We observed the intervening ISM material along the sightline to epsilon Per and present initial characterization of the column densities, temperature, and kinematics of atomic and molecular species in the observation.

  8. NRES: The Network of Robotic Echelle Spectrographs

    NASA Astrophysics Data System (ADS)

    Siverd, Robert; Eastman, Jason D.; Brown, Timothy M.; Hygelund, John; Henderson, Todd; Tufts, Joseph; Van Eyken, Julian C.; Barnes, Stuart

    2015-01-01

    Las Cumbres Observatory Global Network (LCOGT) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of six identical, optical (390 - 860 nm) high-precision spectrographs, each fiber-fed simultaneously by two 1 meter telescopes and a thorium argon calibration source, one at each of our observatory sites in the Northern and Southern hemispheres. Thus, NRES will be a single, globally-distributed, autonomous observing facility using twelve 1-m telescopes. Simulations suggest we will achieve long-term radial velocity precision of better than 3 m/s in less than an hour for stars brighter than V = 12. We have been funded with NSF MRI and ATI grants, and expect our first spectrograph to be deployed in mid 2015, with the full network operation of all 6 units beginning in 2016. We will discuss the NRES design, goals, robotic operation, and status, as well as the early results from our prototype spectrograph.

  9. Production and evaluation of silicon immersion gratings for infrared astronomy.

    PubMed

    Marsh, J P; Mar, D J; Jaffe, D T

    2007-06-10

    Immersion gratings, diffraction gratings where the incident radiation strikes the grooves while immersed in a dielectric medium, offer significant compactness and performance advantages over front-surface gratings. These advantages become particularly large for high-resolution spectroscopy in the near-IR. The production and evaluation of immersion gratings produced by fabricating grooves in silicon substrates using photolithographic patterning and anisotropic etching is described. The gratings produced under this program accommodate beams up to 25 mm in diameter (grating areas to 55 mm x 75 mm). Several devices are complete with appropriate reflective and antireflection coatings. All gratings were tested as front-surface devices as well as immersed gratings. The results of the testing show that the echelles behave according to the predictions of the scalar efficiency model and that tests done on front surfaces are in good agreement with tests done in immersion. The relative efficiencies range from 59% to 75% at 632.8 nm. Tests of fully completed devices in immersion show that the gratings have reached the level where they compete with and, in some cases, exceed the performance of commercially available conventional diffraction gratings (relative efficiencies up to 71%). Several diffraction gratings on silicon substrates up to 75 mm in diameter having been produced, the current state of the silicon grating technology is evaluated.

  10. Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Kentischer, T. J.; Steinmetz, T.; Probst, R. A.; Franz, M.; Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Schmidt, W.

    2012-09-01

    Laser frequency combs (LFC) provide a direct link between the radio frequency (RF) and the optical frequency regime. The comb-like spectrum of an LFC is formed by exact equidistant laser modes, whose absolute optical frequencies are controlled by RF-references such as atomic clocks or GPS receivers. While nowadays LFCs are routinely used in metrological and spectroscopic fields, their application in astronomy was delayed until recently when systems became available with a mode spacing and wavelength coverage suitable for calibration of astronomical spectrographs. We developed a LFC based calibration system for the high-resolution echelle spectrograph at the German Vacuum Tower Telescope (VTT), located at the Teide observatory, Tenerife, Canary Islands. To characterize the calibration performance of the instrument, we use an all-fiber setup where sunlight and calibration light are fed to the spectrograph by the same single-mode fiber, eliminating systematic effects related to variable grating illumination.

  11. NRES: The Network of Robotic Echelle Spectrographs

    NASA Astrophysics Data System (ADS)

    Siverd, Robert; Brown, Timothy M.; Hygelund, John; Henderson, Todd; Tufts, Joseph; Eastman, Jason; Van Eyken, Julian C.; Barnes, Stuart

    2016-01-01

    Las Cumbres Observatory Global Network (LCOGT) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of six identical, optical (390 - 860 nm) high-precision spectrographs, each fiber-fed simultaneously by up to two 1-meter telescopes and a thorium argon calibration source. We plan to install one at up to 6 observatory sites in the Northern and Southern hemispheres, creating a single, globally-distributed, autonomous spectrograph facility using up to twelve 1-m telescopes. Simulations suggest we will achieve long-term radial velocity precision of 3 m/s in less than an hour for stars brighter than V = 12. We have been funded with NSF MRI and ATI grants, and expect our first spectrograph to be deployed in early 2016, with the full network operation of 5 or 6 units beginning in 2017. We will briefly overview the NRES design, goals, robotic operation, and status. In addition, we will discuss early results from our prototype spectrograph, the laboratory and on-sky performance of our first production unit, and the ongoing software development effort to bring this resource online.

  12. NRES: The Network of Robotic Echelle Spectrographs

    NASA Astrophysics Data System (ADS)

    Siverd, Robert; Brown, Timothy M.; Henderson, Todd; Hygelund, John; Tufts, Joseph; Eastman, Jason; Barnes, Stuart; Van Eyken, Julian C.

    2016-06-01

    Las Cumbres Observatory Global Network (LCOGT) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of six identical, optical (390 - 860 nm) high-precision spectrographs, each fiber-fed simultaneously by up to two 1-meter telescopes and a thorium argon calibration source. We plan to install one at up to 6 observatory sites in the Northern and Southern hemispheres, creating a single, globally-distributed, autonomous spectrograph facility using up to twelve 1-m telescopes. Simulations suggest we will achieve long-term radial velocity precision of 3 m/s in less than an hour for stars brighter than V = 12. We have been funded with NSF MRI and ATI grants, and expect to deploy the first spectrograph in fall 2016, with the full network operation of 5 or 6 units beginning in 2017. We will briefly overview the NRES design, goals, robotic operation, and status. In addition, we will discuss early results from our prototype spectrograph, the laboratory and on-sky performance of our first production unit, initial science results, and the ongoing software development effort to bring this resource online.

  13. NRES: the network of robotic Echelle spectrographs

    NASA Astrophysics Data System (ADS)

    Siverd, Robert J.; Brown, Timothy M.; Hygelund, John; Henderson, Todd; Tufts, Joseph R.; Eastman, Jason D.; van Eyken, Julian; Barnes, Stuart

    2016-08-01

    Las Cumbres Observatory Global Network (LCOGT) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of six identical, optical (390 - 860 nm) high-precision spectrographs, each fiber-fed simultaneously by up to two 1-meter telescopes and a thorium argon calibration source. We plan to install one at up to 6 observatory sites in the Northern and Southern hemispheres, creating a single, globally-distributed, autonomous spectrograph facility using up to twelve 1-meter telescopes. Simulations suggest we will achieve long-term radial velocity precision of 3 m/s in less than an hour for stars brighter than V = 12. We have been funded with NSF MRI and ATI grants, and expect our first spectrograph to be deployed in fall 2016, with the full network operation of 5 or 6 units beginning in 2017. We will briefly overview the NRES design, goals, robotic operation, and status. In addition, we will discuss early results from our prototype spectrograph, the laboratory and on-sky performance of our first production unit, and the ongoing software development effort to bring this resource online.

  14. Modelling high resolution Echelle spectrographs for calibrations: Hanle Echelle spectrograph, a case study

    NASA Astrophysics Data System (ADS)

    Chanumolu, Anantha; Jones, Damien; Thirupathi, Sivarani

    2015-06-01

    We present a modelling scheme that predicts the centroids of spectral line features for a high resolution Echelle spectrograph to a high accuracy. Towards this, a computing scheme is used, whereby any astronomical spectrograph can be modelled and controlled without recourse to a ray tracing program. The computations are based on paraxial ray trace and exact corrections added for certain surface types and Buchdahl aberration coefficients for complex modules. The resultant chain of paraxial ray traces and corrections for all relevant components is used to calculate the location of any spectral line on the detector under all normal operating conditions with a high degree of certainty. This will allow a semi-autonomous control using simple in-house, programming modules. The scheme is simple enough to be implemented even in a spreadsheet or in any scripting language. Such a model along with an optimization routine can represent the real time behaviour of the instrument. We present here a case study for Hanle Echelle Spectrograph. We show that our results match well with a popular commercial ray tracing software. The model is further optimized using Thorium Argon calibration lamp exposures taken during the preliminary alignment of the instrument. The model predictions matched the calibration frames at a level of 0.08 pixel. Monte Carlo simulations were performed to show the photon noise effect on the model predictions.

  15. First: Florida Ir Silicon Immersion Grating Spectrometer

    NASA Astrophysics Data System (ADS)

    Ge, Jian; Zhao, B.; Wang, J.; Wan, X.; Powell, S.

    2012-01-01

    The FIRST silicon immersion grating spectrometer is being developed at UF to search for habitable Earth-like planets around M dwarfs and giant planets around young active stars. This compact cryogenic IR instrument is designed to have a spectral resolution of R=72,000 at 1.4-1.8 µm with a silicon immersion grating and R=60K at 0.8-1.35 µm with an R4 echelle. The goal is to reach a long term Doppler precision of 1-3 m/s for bright M dwarfs. The FIRST silicon immersion grating, with 54.74 degree blaze angle and 16 l/mm groove density, has been fully characterized in the lab. The 50x50 mm square grating entrance pupil is coated with a single layer of anti-reflection coating resulting in a 2.1% measured reflection loss. The grating surface was coated with a gold layer to increase grating surface reflectivity. It has produced R=110,000 diffraction limited spectral resolution at 1.523 micron in a lab test spectrograph with 20 mm pupil diameter. The integrated scattered light is less than 0.2\\% and grating has no visible ghosts down to the measuring instrument noise level. The grating efficiency is 69\\% at the peak of the blaze. This silicon immersion grating is ready for scientific observations with FIRST. FIRST is scheduled to be integrated in the lab during the spring of 2012 and see the first light at an astronomical telescope (TBD) the summer of 2012.

  16. A compact echelle spectrograph for characterization of astro-combs

    NASA Astrophysics Data System (ADS)

    Probst, Rafael A.; Steinmetz, Tilo; Wu, Yuanjie; Grupp, Frank; Udem, Thomas; Holzwarth, Ronald

    2017-03-01

    We present an echelle spectrograph that is optimized for characterization of frequency combs for astronomical applications (astro-combs). In spite of its very compact and cost-efficient design, it allows viewing the spectrum of a frequency comb in nearly the same way as a full-sized high-resolution echelle spectrograph as used at astronomical observatories. This is of great value for testing and characterizing astro-combs during their assembly phase. The spectrograph can further be utilized to effectfully demonstrate the remarkable capabilities of astro-combs.

  17. Development of the Colorado High-resolution Echelle Stellar Spectrograph (CHESS)

    NASA Astrophysics Data System (ADS)

    France, Kevin; Beasley, Matthew; Kane, Robert; Nell, Nicholas; Burgh, Eric B.; Green, James C.

    2012-09-01

    A key astrophysical theme that will drive future UV/optical space missions is the life cycle of cosmic matter, from the flow of intergalactic gas into galaxies to the formation and evolution of exoplanetary systems. Spectroscopic systems capable of delivering high resolution with low backgrounds will be essential to addressing these topics. Towards this end, we are developing a rocket-borne instrument that will serve as a pathfinder for future high-sensitivity, highresolution UV spectrographs. The Colorado High-resolution Echelle Stellar Spectrograph (CHESS) will provide 2 km s-1 velocity resolution (R = 150,000) over the 100 - 160 nm bandpass that includes key atomic and molecular spectral diagnostics for the intergalactic medium (H I Lyman-series, O VI, N V, and C IV), exoplanetary atmospheres (H I Lyman-alpha, O I, and C II), and protoplanetary disks (H2 and CO electronic band systems). CHESS uses a novel mechanical collimator comprised of an array of 10 mm x 10 mm stainless steel tubes to feed a low-scatter, 69 grooves mm-1 echelle grating. The cross-disperser is a holographically ruled toroid, with 351 grooves mm-1. The spectral orders can be recorded with either a 40 mm cross-strip microchannel plate detector or a 3.5k x 3.5k δ-doped CCD. The microchannel plate will deliver 30 μm spatial resolution and employs new 64 amp/axis electronics to accommodate high count rate observations of local OB stars. CHESS is scheduled to be launched aboard a NASA Terrier/Black Brant IX sounding rocket from White Sands Missile Range in the summer of 2013.

  18. Adaptive filtering of Echelle spectra of distant Quasars

    NASA Technical Reports Server (NTRS)

    Priebe, A.; Liebscher, D.-E.; Lorenz, H.; Richter, G.-M.

    1992-01-01

    The study of the Ly alpha - forest of distant (approximately greater than 3) Quasars is an important tool in obtaining a more detailed picture of the distribution of matter along the line of sight and thus of the general distribution of matter in the Universe and is therefore of important cosmological significance. Obviously, this is one of the tasks where spectral resolution plays an important role. The spectra used were obtained with the EFOSC at the ESO 3.6m telescope. Applying for the data reduction the standard Echelle procedure, as it is implemented for instance in the MIDAS-package, one uses stationary filters (e.g. median) for noise and cosmic particle event reduction in the 2-dimensional Echelle image. These filters are useful if the spatial spectrum of the noise reaches essentially higher frequencies then the highest resolution features in the image. Otherwise the resolution in the data will be degraded and the spectral lines smoothed. However, in the Echelle spectra the highest resolution is already in the range of one or a few pixels and therefore stationary filtering means always a loss of resolution. An Echelle reduction procedure on the basis of a space variable filter described which recognizes the local resolution in the presence of noise and adapts to it is developed. It was shown that this technique leads to an improvement in resolution by a factor of 2 with respect to standard procedures.

  19. Characterizing the cross dispersion reflection gratings of CRIRES+

    NASA Astrophysics Data System (ADS)

    Follert, Roman; Taubert, Dieter; Hollandt, Jörg; Monte, Christian; Oliva, Ernesto; Seemann, Ulf; Löwinger, Tom; Anwand-Heerwart, Heiko; Schmidt, Christof; Dorn, Reinhold J.; Bristow, Paul; Hatzes, Artie; Reiners, Ansgar; Piskunov, Nikolai; Heiter, Ulrike; Stempels, Eric; Marquart, Thomas; Lavail, Alexis; Cumani, Claudio; Grunhut, Jason; Haimerl, Andreas; Hinterschuster, Renate; Ives, Derek J.; Jung, Yves; Kerber, Florian; Klein, Barbara; Lizon, Jean Louis; Molina-Conde, Ignacio; Nicholson, Belinda; Origlia, Livia; Pasquini, Luca; Paufique, Jérôme; Stegmeier, Jörg; Tordo, Sebastien

    2016-08-01

    The CRIRES+ project attempts to upgrade the CRIRES instrument into a cross dispersed Echelle spectrograph with a simultaneous recording of 8-10 diffraction orders. In order to transform the CRIRES spectrograph into a cross-dispersing instrument, a set of six reflection gratings, each one optimized for one of the wavelength bands CRIRES+ will operate in (YJHKLM), will be used as cross dispersion elements in CRIRES+. Due to the upgrade nature of the project, the choice of gratings depends on the fixed geometry of the instrument. Thus, custom made gratings would be required to achieve the ambitious design goals. Custom made gratings have the disadvantage, though, that they come at an extraordinary price and with lead times of more than 12 months. To mitigate this, a set of off-the-shelf gratings was obtained which had grating parameters very close to the ones being identified as optimal. To ensure that the rigorous specifications for CRIRES+ will be fulfilled, the CRIRES+ team started a collaboration with the Physikalisch-Technische Bundesanstalt Berlin (PTB) to characterize gratings underconditions similar to the operating conditions in CRIRES+ (angle of incidence, wavelength range). The respective test setup was designed in collaboration between PTB and the CRIRES+ consortium. The PTB provided optical radiation sources and calibrated detectors for each wavelength range. With this setup, it is possible to measure the absolute efficiency of the gratings both wavelength dependent and polarization state dependent in a wavelength range from 0.9 μm to 6 μm.

  20. Initial Results from the MAVEN IUVS Echelle Channel

    NASA Astrophysics Data System (ADS)

    Clarke, John T.; Mayassi, Majd; McClintock, William; Schneider, Nick; Deighan, Justin; Stewart, Ian; Holsclaw, Greg; Jakosky, Bruce

    2015-11-01

    The study of the evolution of water on Mars includes understanding the high D/ H ratio in the atmosphere and surface water today, believed to be linked to the historic loss of a large volume of primordial water (the lighter H escapes faster than the heavier D). Toward this end, the IUVS instrument on MAVEN contains the first echelle spectrograph to be sent to another planet. The system has a novel optical design to enable long-aperture measurements of emission lines in the absence of continuum, intended primarily to measure the H and D Ly α emission lines and thereby the D/H ratio from the martian upper atmosphere. The system also detects the OI 1304 triplet with the three component lines well resolved. The specific scientific goal of the echelle channel is to measure the H and D Ly α emissions, and to discover how the H and D densities, temperatures, and escape fluxes vary with location, season, topography, etc. Recent IR observations indicate large variations in the D/H ratio in the lower atmosphere from location to location, and possibly seasonal changes [Villanueva et al. 2015]. HST and MEX measurements of the H corona of Mars show large (order of magnitude) changes in the H exosphere and escape flux with changing seasons and/or heliospheric distance [Clarke et al. 2014 Chaffin et al. 2014]. Early results from the echelle channel regarding how these parameters apply to martian deuterium will be presented.

  1. CERES: A Set of Automated Routines for Echelle Spectra

    NASA Astrophysics Data System (ADS)

    Brahm, Rafael; Jordán, Andrés; Espinoza, Néstor

    2017-03-01

    We present the Collection of Elemental Routines for Echelle Spectra (CERES). These routines were developed for the construction of automated pipelines for the reduction, extraction, and analysis of spectra acquired with different instruments, allowing the obtention of homogeneous and standardized results. This modular code includes tools for handling the different steps of the processing: CCD image reductions; identification and tracing of the echelle orders; optimal and rectangular extraction; computation of the wavelength solution; estimation of radial velocities; and rough and fast estimation of the atmospheric parameters. Currently, CERES has been used to develop automated pipelines for 13 different spectrographs, namely CORALIE, FEROS, HARPS, ESPaDOnS, FIES, PUCHEROS, FIDEOS, CAFE, DuPont/Echelle, Magellan/Mike, Keck/HIRES, Magellan/PFS, and APO/ARCES, but the routines can be easily used to deal with data coming from other spectrographs. We show the high precision in radial velocity that CERES achieves for some of these instruments, and we briefly summarize some results that have already been obtained using the CERES pipelines.

  2. Thermal sensitivity of DASH interferometers: the role of thermal effects during the calibration of an Echelle DASH interferometer.

    PubMed

    Marr, Kenneth D; Englert, Christoph R; Harlander, John M; Miller, Kenneth W

    2013-11-20

    The use of a Doppler asymmetric spatial heterodyne (DASH) interferometer with an Echelle grating provides the ability to simultaneously image the 558 and 630 nm emission lines (e.g., at grating orders of n=8 and n=7, respectively) of atomic oxygen in the thermosphere. By measuring the Doppler shifts of these lines (expected relative change in wavelength on the order of 10⁻⁸), we are able to determine the thermospheric winds. Because the expected wavelength changes due to the Doppler shift are so small, understanding, monitoring, and accounting for thermal effects is expected to be important. Previously, the thermal behavior of a temperature-compensated monolithic DASH interferometer was found to have a higher thermal sensitivity than predicted by a simple model [Opt. Express 18, 26430, 2010]. A follow-up study [Opt. Express 20, 9535, 2012] suggested that this is due to thermal distortion of the interferometer, which consists of materials with different coefficients of thermal expansion. In this work, we characterize the thermal drift of a nonmonolithic Echelle DASH interferometer and discuss the implications of these results on the use of only a single wavelength source during calibration. Furthermore, we perform a finite element analysis of the earlier monolithic interferometer in order to determine how distortion would affect the thermal sensitivity of that device. Incorporating that data into the model, we find good agreement between the modified model and the measured thermal sensitivities. These findings emphasize the fact that distortion needs to be considered for the design of thermally compensated, monolithic DASH interferometers.

  3. Development of infrared Echelle spectrograph and mid-infrared heterodyne spectrometer on a small telescope at Haleakala, Hawaii for planetary observation

    NASA Astrophysics Data System (ADS)

    Sakanoi, Takeshi; Kasaba, Yasumasa; Kagitani, Masato; Nakagawa, Hiromu; Kuhn, Jeff; Okano, Shoichi

    2014-08-01

    We report the development of infrared Echelle spectrograph covering 1 - 4 micron and mid-infrared heterodyne spectrometer around 10 micron installed on the 60-cm telescope at the summit of Haleakala, Hawaii (alt.=3000m). It is essential to carry out continuous measurement of planetary atmosphere, such as the Jovian infrared aurora and the volcanoes on Jovian satellite Io, to understand its time and spatial variations. A compact and easy-to-use high resolution infrared spectrometer provide the good opportunity to investigate these objects continuously. We are developing an Echelle spectrograph called ESPRIT: Echelle Spectrograph for Planetary Research In Tohoku university. The main target of ESPRIT is to measure the Jovian H3+ fundamental line at 3.9 micron, and H2 nu=1 at 2.1 micron. The 256x256 pixel CRC463 InSb array is used. An appropriate Echelle grating is selected to optimize at 3.9 micron and 2.1 micron for the Jovian infrared auroral observations. The pixel scale corresponds to the atmospheric seeing (0.3 arcsec/pixel). This spectrograph is characterized by a long slit field-of-view of ~ 50 arcsec with a spectral resolution is over 20,000. In addition, we recently developed a heterodyne spectrometer called MILAHI on the 60 cm telescope. MILAHI is characterized by super high-resolving power (more than 1,500,000) covering from 7 - 13 microns. Its sensitivity is 2400 K at 9.6 micron with a MCT photo diode detector of which bandwidth of 3000 MHz. ESPRIT and MILAHI is planned to be installed on 60 cm telescope is planned in 2014.

  4. Early Results from the MAVEN IUVS Echelle Channel

    NASA Astrophysics Data System (ADS)

    Clarke, J. T.; Mayyasi, M.; Schneider, N. M.; Deighan, J.; Stewart, I. F.; McClintock, B.; Jakosky, B. M.; Bhattacharyya, D.

    2015-12-01

    The IUVS instrument on MAVEN contains the first echelle spectrograph to be sent to another planet. The system has a novel optical design to enable long-aperture measurements of emission lines in the absence of continuum, intended primarily to measure the H and D Ly αlpha emission lines and thereby the D/H ratio from the martian upper atmosphere. The system also detects the OI 1304 triplet with the three component lines well resolved. The main scientific goal of the echelle channel is to measure the H and D Ly αlpha emissions, and to discover how the H and D densities, temperatures, and escape fluxes vary with location, season, topography, etc. The global D/H ratio of the martian atmosphere is roughly 5 times higher than in the terrestrial atmosphere due to the escape of a large volume of water into space, likely early in the history of Mars. Since H atoms escape faster than D atoms, the D/H ratio increases with time as more water is lost. Recent IR observations indicate large variations in the D/H ratio in the lower atmosphere from location to location, and possibly seasonal changes [Villanueva et al. 2015]. HST and MEX measurements of the H corona of Mars show large (order of magnitude) changes in the H exosphere and escape flux with changing seasons and/or heliospheric distance [Clarke et al. 2014; Chaffin et al. 2014]. Do the same variations apply to deuterium? Are there similar variations in the D/H ratio? Early results from the echelle channel will be presented.

  5. SWP Echelle Spectra of Chromospherically Active Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    High resolution spectra of the 1150-2000 A region are enormously valuable for probing outer- atmosphere structure in cool stars. For example, such data can be used to separate blends, identify individual emission components in short-period binary systems, determine intensity ratios in close multiplets, estimate reliable emission strengths of lines superimposed on bright stellar continua, and test for the presence or absence of stellar winds at 105 K temperatures. These possibilities are not practical with IUE low-dispersion spectra. However, one must pay a steep-price to obtain useable high-dispersion IUE spectra and the additional dimension of diagnostic information, namely only a handful of the brightest UV sources are accessible even with shift-long exposures. We propose below an observing program to obtain echelle spectra of chromospherically active dwarf stars in the 1150-2000 A shortwavelength region. This program is intended to explore a particular class of objects that heretofore have not been observed at high dispersion with the SWP camera. Futhermore, this program complements previous SWP echelle studies by our group at the University of Colorado of quiet-chromosphere dwarf stars (alpha Cen A, alpha Cen B), active giants (alpha Aur A, lambda And, beta Dra), and the extreme case of the very active RS CVn-type system HR 1099. As described below, highdispersion spectra of these targets have provided a critical interpretive dimension that was lacking in previous low-dispersion studies. However, several fundamental questions have been raised in the course of our exploratory SWP work on what, in practice, are two distinct classes of chromospheric stars: the quiet dwarfs and the active giants. We feel that many of these questions can be answered by bridging the interpretive gap with a careful study of the active dwarfs. Our recent experience with shift-long SWP echelle exposures of chromospheric emission stars has suggested that our previous estimates of

  6. Research directed toward improved echelles for the ultraviolet

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Research was undertaken to demonstrate that improved efficiencies for low frequency gratings are obtainable with the careful application of present technology. The motivation for the study was the desire to be assured that the grating-efficiency design goals for potential Space Telescope spectrographs can be achieved. The work was organized to compare gratings made with changes in the three specific parameters: the ruling tool profile, the coating material, and the lubricants used during the ruling process. A series of coatings and test gratings were fabricated and were examined for surface smoothness with a Nomarski Differential Interference Microscope and an electron microscope. Photomicrographs were obtained to show the difference in smoothness of the various coatings and rulings. Efficiency measurements were made for those test rulings that showed good groove characteristics: smoothness, proper ruling depth, and absence of defects. The intuitive feeling that higher grating efficiency should be correlated with the degree of smoothness of both the coating and the grating is supported by the results.

  7. Multilayer diffraction grating

    SciTech Connect

    Barbee, T.W., Jr.

    1988-10-18

    This invention is for a reflection diffraction grating that functions at x-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages. 2 figs.

  8. Multilayer diffraction grating

    DOEpatents

    Barbee, T.W. Jr.

    1990-04-10

    This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages. 2 figs.

  9. Multilayer diffraction grating

    DOEpatents

    Barbee, Jr., Troy W.

    1990-01-01

    This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages.

  10. Materials and Fabrication Issues for Large Machined Germanium Immersion Gratings

    SciTech Connect

    Kuzmenko, P J; Davis, P J; Little, S L; Hale, L C

    2006-05-22

    LLNL has successfully fabricated small (1.5 cm{sup 2} area) germanium immersion gratings. We studied the feasibility of producing a large germanium immersion grating by means of single point diamond flycutting. Our baseline design is a 63.4o blaze echelle with a 6 cm beam diameter. Birefringence and refractive index inhomogeneity due to stresses produced by the crystal growth process are of concern. Careful selection of the grating blank and possibly additional annealing to relieve stress will be required. The Large Optics Diamond Turning Machine (LODTM) at LLNL is a good choice for the fabrication. It can handle parts up to 1.5 meter in diameter and 0.5 meter in length and is capable of a surface figure accuracy of better than 28 nm rms. We will describe the machine modifications and the machining process for a large grating. A next generation machine, the Precision Optical Grinder and Lathe (POGAL), currently under development has tighter specifications and could produce large gratings with higher precision.

  11. AIRES: An Airborne Infra-Red Echelle Spectrometer for SOFIA

    NASA Technical Reports Server (NTRS)

    Dotson, Jessie J.; Erickson, Edwin F.; Haas, Michael R.; Colgan, Sean W. J.; Simpson, Janet P.; Telesco, Charles M.; Pina, Robert K.; Wolf, Juergen; Young, Erick T.

    1999-01-01

    SOFIA will enable astronomical observations with unprecedented angular resolution at infrared wavelengths obscured from the ground. To help open this new chapter in the exploration of the infrared universe, we are building AIRES, an Airborne Infra-Red Echelle Spectrometer. AIRES will be operated as a first generation, general purpose facility instrument by USRA, NASA's prime contractor for SOFIA. AIRES is a long slit spectrograph operating from 17 - 210 microns. In high resolution mode the spectral resolving power is approx. 10(exp 6) microns/A or approx. 10(exp 4) at 100 microns. Unfortunately, since the conference, a low resolution mode with resolving power about 100 times lower has been deleted due to budgetary constraints. AIRES includes a slit viewing camera which operates in broad bands at 18 and 25 microns.

  12. Catwalk grate lifting tool

    DOEpatents

    Gunter, L.W.

    1992-08-11

    A device is described for lifting catwalk grates comprising an elongated bent member with a handle at one end and a pair of notched braces and a hook at the opposite end that act in conjunction with each other to lock onto the grate and give mechanical advantage in lifting the grate. 10 figs.

  13. Renewable liquid reflection grating

    DOEpatents

    Ryutov, Dmitri D.; Toor, Arthur

    2003-10-07

    A renewable liquid reflection grating. Electrodes are operatively connected to a conducting liquid in an arrangement that produces a reflection grating and driven by a current with a resonance frequency. In another embodiment, the electrodes create the grating by a resonant electrostatic force acting on a dielectric liquid.

  14. Catwalk grate lifting tool

    DOEpatents

    Gunter, Larry W.

    1992-01-01

    A device for lifting catwalk grates comprising an elongated bent member with a handle at one end and a pair of notched braces and a hook at the opposite end that act in conjunction with each other to lock onto the grate and give mechanical advantage in lifting the grate.

  15. Current Calibration Efforts and Performance of the HST Space Telescope Imaging Spectrograph: Echelle Flux Calibration, the BAR5 Occulter, and Lamp Lifetimes

    NASA Astrophysics Data System (ADS)

    Monroe, TalaWanda R.; Aloisi, Alessandra; Debes, John H.; Jedrzejewski, Robert I.; Lockwood, Sean A.; Peeples, Molly S.; Proffitt, Charles R.; Riley, Allyssa; Walborn, Nolan R.

    2016-06-01

    The variety of operating modes of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) continues to allow STIS users to obtain unique, high quality observations and cutting-edge results 19 years after its installation on HST. STIS is currently the only instrument available to the astronomy community that allows high spectral and spatial resolution spectroscopy in the FUV and NUV, including echelle modes. STIS also supports solar-blind imaging in the FUV. In the optical, STIS provides long-slit, first-order spectra that take advantage of HST's superb spatial resolution, as well as several unique unfiltered coronagraphic modes, which continue to benefit the exoplanet and debris-disk communities. The STIS instrument team monitors the instrument’s health and performance over time to characterize the effects of radiation damage and continued use of the detectors and optical elements. Additionally, the STIS team continues to improve the quality of data products for the user community. We present updates on efforts to improve the echelle flux calibration of overlapping spectral orders due to changes in the grating blaze function since HST Servicing Mission 4, and efforts to push the contrast limit and smallest inner working angle attainable with the coronagraphic BAR5 occulter. We also provide updates on the performance of the STIS calibration lamps, including work to maintain the accuracy of the wavelength calibration for all modes.

  16. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, Michael D.; Britten, Jerald A.; Nguyen, Hoang T.; Boyd, Robert; Shore, Bruce W.

    1999-01-01

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

  17. Multilayer dielectric diffraction gratings

    DOEpatents

    Perry, M.D.; Britten, J.A.; Nguyen, H.T.; Boyd, R.; Shore, B.W.

    1999-05-25

    The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described. 7 figs.

  18. Off-the-shelf Echelle Spectroscopy: Two Devices on the Test Block

    NASA Astrophysics Data System (ADS)

    Eversberg, Thomas

    2016-11-01

    Today, various Echelle spectrographs for small telescopes are available on the market. These instruments are ready-to-use, including professional data reduction chains. Manufacturers claim that their compact instruments can deliver professionally usable data for very low prices. This paper presents extensive tests of the two most popular small-scale Echelle spectrographs for telescopes in the 1 m domain with a focus on radial velocity accuracy.

  19. AVES: an adaptive optics visual echelle spectrograph for the VLT

    NASA Astrophysics Data System (ADS)

    Pasquini, Luca; Delabre, Bernard; Avila, Gerardo; Bonaccini, Domenico

    1998-07-01

    We present the preliminary study of a low cost, high performance spectrograph for the VLT, for observations in the V, R and I bands. This spectrograph is meant for intermediate (R equals 16,000) resolution spectroscopy of faint (sky and/or detector limited) sources, with particular emphasis on the study of solar-type (F-G) stars belonging to the nearest galaxies and to distant (or highly reddened) galactic clusters. The spectrograph is designed to use the adaptive optics (AO) systems at the VLT Telescope. Even if these AO systems will not provide diffraction limited images in the V, R and I bands, the photon concentration will still be above approximately 60% of the flux in an 0.3 arcsecond aperture for typical Paranal conditions. This makes the construction of a compact, cheap and efficient echelle spectrograph possible. AVES will outperform comparable non adaptive optic instruments by more than one magnitude for sky- and/or detector-limited observations, and it will be very suitable for observations in crowded fields.

  20. Design and Construction of VUES: The Vilnius University Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Jurgenson, Colby; Fischer, Debra; McCracken, Tyler; Sawyer, David; Giguere, Matt; Szymkowiak, Andrew; Santoro, Fernando; Muller, Gary

    2016-03-01

    In February 2014, the Yale Exoplanet Laboratory was commissioned to design, build, and deliver a high resolution (R=60,000) spectrograph for the 1.65m telescope at the Molėtai Astronomical Observatory. The observatory is operated by the Institute of Theoretical Physics and Astronomy at Vilnius University. The Vilnius University Echelle Spectrograph (VUES) is a white-pupil design that is fed via an octagonal fiber from the telescope and has an operational bandpass from 400nm to 880nm. VUES incorporates a novel modular optomechanical design that allows for quick assembly and alignment on commercial optical tables. This approach allowed the spectrograph to be assembled and commissioned at Yale using lab optical tables and then reassembled at the observatory on a different optical table with excellent repeatability. The assembly and alignment process for the spectrograph was reduced to a few days, allowing the spectrograph to be completely disassembled for shipment to Lithuania, and then installed at the observatory during a 10-day period in June of 2015.

  1. Calibrating echelle spectrographs with Fabry-Pérot etalons

    NASA Astrophysics Data System (ADS)

    Bauer, F. F.; Zechmeister, M.; Reiners, A.

    2015-09-01

    Context. Over the past decades hollow-cathode lamps have been calibration standards for spectroscopic measurements. Advancing to cm/s radial velocity precisions with the next generation of instruments requires more suitable calibration sources with more lines and fewer dynamic range problems. Fabry-Pérot interferometers provide a regular and dense grid of lines and homogeneous amplitudes, which makes them good candidates for next-generation calibrators. Aims: We investigate the usefulness of Fabry-Pérot etalons in wavelength calibration, present an algorithm to incorporate the etalon spectrum in the wavelength solution, and examine potential problems. Methods: The quasi-periodic pattern of Fabry-Pérot lines was used along with a hollow-cathode lamp to anchor the numerous spectral features on an absolute scale. We tested our method with the HARPS spectrograph and compared our wavelength solution to the one derived from a laser frequency comb. Results: The combined hollow-cathode lamp/etalon calibration overcomes large distortion (50 m/s) in the wavelength solution of the HARPS data reduction software. The direct comparison to the laser frequency comb shows differences of only 10 m/s at most. Conclusions: Combining hollow-cathode lamps with Fabry-Pérot interferometers can lead to substantial improvements in the wavelength calibration of echelle spectrographs. Etalons can provide economical alternatives to the laser frequency comb, especially for smaller projects.

  2. Reflective diffraction grating

    DOEpatents

    Lamartine, Bruce C.

    2003-06-24

    Reflective diffraction grating. A focused ion beam (FIB) micromilling apparatus is used to store color images in a durable medium by milling away portions of the surface of the medium to produce a reflective diffraction grating with blazed pits. The images are retrieved by exposing the surface of the grating to polychromatic light from a particular incident bearing and observing the light reflected by the surface from specified reception bearing.

  3. Biopolymer holographic diffraction gratings

    NASA Astrophysics Data System (ADS)

    Savić Šević, Svetlana; Pantelić, Dejan

    2008-03-01

    Surface-relief diffraction gratings are holographically recorded in dextran sensitized with ammonium dichromate (DCD). DCD was exposed with single-frequency 200 mW diode pumped ND-YAG laser, at 532 nm. The diffraction grating profiles were analyzed by atomic force microscopy (AFM). It was found that different surface profiles could be obtained. Gratings with 330 lines/mm spatial frequencies were made. Existence of higher harmonics in Fourier Transform of non-sinusoidal profiles shows that DCD is capable of recording spatial frequencies up to 1320 lines/mm (four times fundamental frequency). The measured maximum relief depth of the DCD grating is 402 nm.

  4. CAFE: Calar Alto Fiber-fed Echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Sánchez, S. F.; Aceituno, J.; Thiele, U.; Grupp, F.; Dreizler, S.; Bean, J.; Benitez, D.

    2011-11-01

    The Calar Alto Fiber-fed Echelle spectrograph (CAFE) is an instrument underconstruction at CAHA to replace FOCES, the high-resolution echellespectrograph at the 2.2 m telescope of the observatory. FOCES is a property ofthe Observatory of the Munich University, and it was recalled it from Calar Altoin 2009. The instrument comprised a substantial fraction of thetelescope time during its operational life-time, and it is due to that it wastaken the decision to build a replacement.CAFE shares its basic characteristics with those of FOCES. However, significantimprovements have been introduced in the original design, the quality of thematerials, and the overall stability of the system. In particular: (i) a newcalibration Iodine cell is foreseen to operate together with the standard ThArlamps; (ii) the optical quality of all the components has been selected to belambda/20, instead of the original lambda/10; (iii) an isolated room hasbeen selected to place the instrument, termalized and stabilized againstvibrations (extensive tests have been performed to grant the stability); (iv)most of the mobile parts in FOCES has been substituted by fixed elements, toincrease the stability of the system; and finally (v) a new more efficientCCD, with a smaller pixel has been acquired. It is expected that the overallefficiency and the quality of the data will be significantly improved withrespect to its precesor. In particular, CAFE is design and built to achieveresolutions of R ˜ 70000, which will be kept in the final acquired data,allowing it to compete with current operational extrasolar planets hunters.After two years of work all the components are in place. The instrument is nowfinally assembled, and we are performing the the first alignment tests. It isexpected that the commissioning on the laboratory will finish at the end of2010, followed by the commissioning on telescope along the first semester of2011. If everything goes well, we will offer the instrument in a shared

  5. Spherical grating spectrometers

    NASA Astrophysics Data System (ADS)

    O'Donoghue, Darragh; Clemens, J. Christopher

    2014-07-01

    We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

  6. Aluminum nitride grating couplers.

    PubMed

    Ghosh, Siddhartha; Doerr, Christopher R; Piazza, Gianluca

    2012-06-10

    Grating couplers in sputtered aluminum nitride, a piezoelectric material with low loss in the C band, are demonstrated. Gratings and a waveguide micromachined on a silicon wafer with 600 nm minimum feature size were defined in a single lithography step without partial etching. Silicon dioxide (SiO(2)) was used for cladding layers. Peak coupling efficiency of -6.6 dB and a 1 dB bandwidth of 60 nm have been measured. This demonstration of wire waveguides and wideband grating couplers in a material that also has piezoelectric and elasto-optic properties will enable new functions for integrated photonics and optomechanics.

  7. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, Antonio J.; Butler, Michael A.; Sinclair, Michael B.; Senturia, Stephen D.

    1998-01-01

    An electrically-programmable diffraction grating. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers).

  8. Unexpected effects of a trap in CCD echelle spectra of B-type stars

    NASA Technical Reports Server (NTRS)

    Morrison, Nancy D.; Zimba, Jason R.

    1990-01-01

    Because of the nature of echelle spectra, cosmetic defects such as traps may mimic real spectral features. An example from spectra taken at CTIO with a GEC CCD is presented, and it is shown how the affected pixels can be eliminated from the reduced spectrum, at a slight cost in signal-to-noise ratio.

  9. Grating Beam Combiner.

    DTIC Science & Technology

    1982-12-01

    Contract Number: F30602-80-C-0241 Effective Date of Contract: 15 July 1980 Contract Expiration Date: 1 August 1982 Short Title of Work: Grating...performed. Measurements of the efficiency, diffracted wavefront quality, frequency ratio, and skew are described. Analysis of the effects of nonzero...Section 2.5) for grating groove depth can be understood in terms of their effect on efficiency at the two wavelengths and tolerances thereon. Groove

  10. Color separation gratings

    NASA Technical Reports Server (NTRS)

    Farn, Michael W.; Knowlden, Robert E.

    1993-01-01

    In this paper, we describe the theory, fabrication and test of a binary optics 'echelon'. The echelon is a grating structure which separates electromagnetic radiation of different wavelengths, but it does so according to diffraction order rather than by dispersion within one diffraction order, as is the case with conventional gratings. A prototype echelon, designed for the visible spectrum, is fabricated using the binary optics process. Tests of the prototype show good agreement with theoretical predictions.

  11. Bragg gratings in ORMOCERs

    NASA Astrophysics Data System (ADS)

    Belenguer, Tomas; Cheben, Pavel; Moreno-Barriuso, Eva M.; Nunez, Armonia; Ulibarrena, Manuel; del Monte, Francisco; Levy, David

    1997-10-01

    Two novel holographic recording media based on silica gel methyl methacrylate (MMA) and hydroxy ethyl methacrylate (HEMA) organically modified ceramics (ORMOCERS) are presented and its holographic properties, inferred from the experimental data, are discussed. The recording of holographic gratings of both low-spatial frequency (50 lp/mm) and high-spatial frequency (1400 lp/mm) in a bulk ORMOCER matrix is reported. The gratings were recorded by UV irradiation-induced photopolymerization of the MMA or HEMA monomers embedded in the silica matrix. The Bragg gratings were successfully recorded by interference of two coherent beams of 351.1 nm wavelength. A linearly polarized He-Ne laser beam (632.8 nm) was used for continuous monitoring of the recording process by measurement of the diffraction efficiency and for enhancement of the grating creation process. High diffraction efficiencies (93%) and low absorption and scattering coefficients were measured during the holographic reconstruction by He-Ne laser beam. The most important holographic parameters of the gratings were inferred from the experimental data: diffraction efficiency, angular selectivity, refraction-index modulation amplitude, spectral sensitivity, the Klein-Cook parameter, and the environmental stability of the gratings.

  12. Gratings in polymeric waveguides

    NASA Astrophysics Data System (ADS)

    Mishakov, G.; Sokolov, V.; Kocabas, A.; Aydinli, A.

    2007-04-01

    Laser-induced formation of polymer Bragg grating filters for Dense Wavelength Division Multiplexing (DWDM) applications is discussed. Acrylate monomers halogenated with both fluorine and chlorine, which possess absorption losses less than 0.25 dB/cm and wide choice of refractive indices (from 1.3 to 1.5) in the 1.5 μm telecom wavelength region were used. The monomers are highly intermixable thus permitting to adjust the refractive index of the composition within +/-0.0001. Moreover they are photocurable under UV exposure and exhibit high contrast in polymerization. These properties make halogenated acrylates very promising for fabricating polymeric waveguides and photonic circuits. Single-mode polymer waveguides were fabricated on silicon wafers using resistless contact lithography. Submicron index gratings have been written in polymer waveguides using holographic exposure with He-Cd laser beam (325 nm) through a phase mask. Both uniform and apodized gratings have been fabricated. The gratings are stable and are not erased by uniform UV exposure. The waveguide gratings possess narrowband reflection spectra in the 1.5 μm wavelength region of 0.4 nm width, nearly rectangular shape of the stopband and reflectivity R > 99%. The fabricated Bragg grating filters can be used for multiplexing/demultiplexing optical signals in high-speed DWDM optical fiber networks.

  13. A planar lightwave circuit based micro interrogator and its applications to the interrogation of multiplexed optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Xiao, Gaozhi; Mrad, Nezih; Guo, Honglei; Zhang, Zhiyi; Yao, Jianping

    2008-12-01

    Optical fiber Bragg grating sensors have found potential applications in many fields, but the lack of a simple, field deployable and low cost interrogation system is hindering their deployment. To tackle this, we have developed a micro optical sensor interrogator using a monolithically integrated planar lightwave circuit based echelle diffractive grating demultiplexer and a detector array. The design and development of this device are presented in this paper. It has been found that the measurement range of this micro interrogator is more than 25 nm with better than 1 pm resolution. This paper also reports the applications of the micro interrogator developed to the monitoring of commercial optical fiber Bragg grating (FBG) temperature sensors and mechanical sensors. The results obtained are very satisfactory and in some cases, they are better than those obtained using commercial bench top lab equipment.

  14. Fabrication and testing of a silicon immersion grating for infrared spectroscopy

    SciTech Connect

    Kuzmenko, P.J.; Ciarlo, D.R.; Stevens, C.G.

    1994-07-25

    Recent advances in silicon micromachining techniques (e.g. anisotropic etching) allow the fabrication of very coarse infrared echelle gratings. When used in immersion mode, the dispersion is increased proportionally to the refractive index. This permits a very significant reduction in the overall size of a spectrometer while maintaining the same resolution. We have fabricated a right triangular prism (30{times}60{times}67 mm with a rectangular entrance face 30{times}38 mm) from silicon with a grating etched into the face of the hypotenuse. The grating covers an area of 32 mm by 64 mm and has a 97.5 PM periodicity with a blaze angle of 63.4{sup o}. The groove surfaces are very smooth with a roughness of a few manometers. Random defects in the silicon are the dominant source of grating scatter ({approx} 12% at 3.39 {mu}m). We measure a grating ghost intensity of 1.2%. The diffraction peak is quite narrow, slightly larger than the Airy disc diameter at F/12. However due to wavefront aberrations, perhaps 15--20% of the diffracted power is in the peak with the rest distributed in a diameter roughly five times the Airy disc.

  15. Compact grating interferometer for producing photoresist gratings with incoherent light.

    PubMed

    Post, D; Patorski, K; Ning, P

    1987-03-15

    An achromatic interferometer was developed to produce 1200-lines/mm crossed-line photoresist gratings with a mercury arc light source. It is a compact reflection system of outstanding stability. Alignment procedures are described. The most stringent requirement, coplanar alignment of two folding gratings, was accomplished with the aid of a Twyman-Green interferometer. The grating interferometer produced crossed-line photoresist gratings with first-order diffraction efficiency exceeding 20%.

  16. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B.

    1986-01-01

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  17. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B.

    1986-09-02

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  18. Circular Fibonacci gratings.

    PubMed

    Gao, Nan; Zhang, Yuchao; Xie, Changqing

    2011-11-01

    We introduce circular Fibonacci gratings (CFGs) that combine the concept of circular gratings and Fibonacci structures. Theoretical analysis shows that the diffraction pattern of CFGs is composed of fractal distributions of impulse rings. Numerical simulations are performed with two-dimensional fast Fourier transform to reveal the fractal behavior of the diffraction rings. Experimental results are also presented and agree well with the numerical results. The fractal nature of the diffraction field should be of great theoretical interest, and shows potential to be further developed into practical applications, such as in laser measurement with wideband illumination.

  19. An elastomeric grating coupler

    NASA Astrophysics Data System (ADS)

    Kocabas, Askin; Ay, Feridun; Dâna, Aykutlu; Aydinli, Atilla

    2006-01-01

    We report on a novel nondestructive and reversible method for coupling free space light to planar optical waveguides. In this method, an elastomeric grating is used to produce an effective refractive index modulation on the surface of the optical waveguide. The external elastomeric grating binds to the surface of the waveguide with van der Waals forces and makes conformal contact without any applied pressure. As a demonstration of the feasibility of the approach, we use it to measure the refractive index of a silicon oxynitride film. This technique is nondestructive, reversible, low cost and can easily be applied to the characterization of optical materials for integrated optics.

  20. Electro-Optic Diffraction Grating Tuned Laser.

    DTIC Science & Technology

    The patent concerns an electro - optic diffraction grating tuned laser comprising a laser medium, output mirror, retro-reflective grating and an electro - optic diffraction grating beam deflector positioned between the laser medium and the reflective diffraction grating. An optional angle multiplier may be used between the electro - optic diffraction grating and the reflective grating.

  1. Birefringence Bragg Binary (3B) grating, quasi-Bragg grating and immersion gratings

    NASA Astrophysics Data System (ADS)

    Ebizuka, Noboru; Morita, Shin-ya; Yamagata, Yutaka; Sasaki, Minoru; Bianco, Andorea; Tanabe, Ayano; Hashimoto, Nobuyuki; Hirahara, Yasuhiro; Aoki, Wako

    2014-07-01

    A volume phase holographic (VPH) grating achieves high angular dispersion and very high diffraction efficiency for the first diffraction order and for S or P polarization. However the VPH grating could not achieve high diffraction efficiency for non-polarized light at a large diffraction angle because properties of diffraction efficiencies for S and P polarizations are different. Furthermore diffraction efficiency of the VPH grating extinguishes toward a higher diffraction order. A birefringence binary Bragg (3B) grating is a thick transmission grating with optically anisotropic material such as lithium niobate or liquid crystal. The 3B grating achieves diffraction efficiency up to 100% for non-polarized light by tuning of refractive indices for S and P polarizations, even in higher diffraction orders. We fabricated 3B grating with liquid crystal and evaluated the performance of the liquid crystal grating. A quasi-Bragg (QB) grating, which consists long rectangle mirrors aligned in parallel precisely such as a window shade, also achieves high diffraction efficiency toward higher orders. We fabricated QB grating by laminating of silica glass substrates and glued by pressure fusion of gold films. A quasi-Bragg immersion (QBI) grating has smooth mirror hypotenuse and reflector array inside the hypotenuse, instead of step-like grooves of a conventional immersion grating. An incident beam of the QBI grating reflects obliquely at a reflector, then reflects vertically at the mirror surface and reflects again at the same reflector. We are going to fabricate QBI gratings by laminating of mirror plates as similar to fabrication of the QB grating. We will also fabricate silicon and germanium immersion gratings with conventional step-like grooves by means of the latest diamond machining methods. We introduce characteristics and performance of these gratings.

  2. Research directed toward improved echelles for the ultraviolet. [large space teslescope spectrographs

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Low frequency gratings obtainable with present technology, can meet the grating-efficiency design goals for potential space telescope spectrographs. Gratings made with changes in the three specific parameters: the ruling tool profile, the coating material, and the lubricants used during the ruling process were compared. A series of coatings and test gratings were fabricated and were examined for surface smoothness with a Nomarski differential interference microscope and an electron microsocope. Photomicrographs were obtained to show the difference in smoothness of the various coatings and rulings. Efficiency measurements were made for those test rulings that showed good groove characteristics: smoothness, proper ruling depth, and absence of defects (e.g., streaks, feathered edges and rough sides). Higher grating efficiency should be correlated with the degree of smoothness of both the coating and the grating groove.

  3. A new generation of spectral extraction and analysis package for Fiber Optics Cassegrain Echelle Spectrograph (FOCES)

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Grupp, Frank; Kellermann, Hanna; Brucalassi, Anna; Schlichter, Jörg; Hopp, Ulrich; Bender, Ralf

    2016-08-01

    We describe a new generation of spectral extraction and analysis software package (EDRS2) for the Fibre Optics Cassegrain Echelle Spectrograph (FOCES), which will be attached to the 2m Fraunhofer Telescope on the Wendelstein Observatory. The package is developed based on Python language and relies on a variety of third party, open source packages such as Numpy and Scipy. EDRS2 contains generalized image calibration routines including overscan correction, bias subtraction, flat fielding and background correction, and can be supplemented by user customized functions to fit other echelle spectrographs. An optimal extraction method is adopted to obtain the one dimensional spectra, and the output multi order, wavelength calibrated spectra are saved in FITS files with binary table format. We introduce the algorithm and performance of major routines in EDRS2.

  4. Total reduction of distorted echelle spectrograms - An automatic procedure. [for computer controlled microdensitometer

    NASA Technical Reports Server (NTRS)

    Peterson, R. C.; Title, A. M.

    1975-01-01

    A total reduction procedure, notable for its use of a computer-controlled microdensitometer for semi-automatically tracing curved spectra, is applied to distorted high-dispersion echelle spectra recorded by an image tube. Microdensitometer specifications are presented and the FORTRAN, TRACEN and SPOTS programs are outlined. The intensity spectrum of the photographic or electrographic plate is plotted on a graphic display. The time requirements are discussed in detail.

  5. Double groove broadband gratings.

    PubMed

    Pietarinen, Juha; Vallius, Tuomas

    2008-09-01

    Waveguiding in periodical structures of the size of the wavelength is applied to increase the functional spectral band of diffractive optics. The deviation of the effective refractive index between waveguides as a function of the wavelength is utilized to compensate the strong wavelength dependence of the efficiency of diffraction gratings.

  6. Gratings and waveguides

    NASA Technical Reports Server (NTRS)

    Bates, K. A.; Erwin, J. K.; Li, L.; Burke, J. J.; Ramanujam, N.

    1993-01-01

    Our immediate objective is to understand the limitations of guided-wave and grating coupler devices in their application to optical data storage. Our long-range goal is to develop and validate design codes for integrated optic devices. The principal research activity was in the development of numerical models for the design of a blue wavelength integrated optical source for data storage applications.

  7. Electrically-programmable diffraction grating

    DOEpatents

    Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

    1998-05-26

    An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

  8. Charged particle accelerator grating

    DOEpatents

    Palmer, R.B.

    1985-09-09

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams onto the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  9. A Flexible and Modular Data Reduction Library for Fiber-fed Echelle Spectrographs

    NASA Astrophysics Data System (ADS)

    Sosnowska, D.; Lovis, C.; Figueira, P.; Modigliani, A.; Marcantonio, P. D.; Megevand, D.; Pepe, F.

    2015-09-01

    Within the ESPRESSO project a new flexible data reduction library is being built. ESPRESSO, the Echelle SPectrograph for Rocky Exoplanets and Stable Spectral Observations is a fiber-fed, high-resolution, cross-dispersed echelle spectrograph. One of its main scientific goals is to search for terrestrial exoplanets using the radial velocity technique. A dedicated pipeline is being developed. It is designed to be able to reduce data from different similar spectrographs: not only ESPRESSO, but also HARPS, HARPS-N and possibly others. Instrument specifics are configurable through an input static configuration table. The first written recipes are already tested on HARPS and HARPS-N real data and ESPRESSO simulated data. The final scientific products of the pipeline will be the extracted 1-dim and 2-dim spectra. Using these products the radial velocity of the observed object can be computed with high accuracy. The library is developed within the standard ESO pipeline environment. It is being written in ANSI C and makes use of the Common Pipeline Library (CPL). It can be used in conjunction with the ESO tools Esorex, Gasgano and Reflex in the usual way.

  10. Phononic crystal diffraction gratings

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

    2012-02-01

    When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

  11. Slow plasmons in grating cavities

    NASA Astrophysics Data System (ADS)

    Aydinli, Atilla; Karademir, Ertugrul; Balci, Sinan; Kocabas, Coskun

    2016-03-01

    Recent research on surface plasmon polaritons and their applications have brought forward a wealth of information and continues to be of interest to many. In this report, we concentrate on propagating surface plasmon polaritons (SPPs) and their interaction with matter. Using grating based metallic structures, it is possible to control the electrodynamics of propagating SPPs. Biharmonic gratings loaded with periodic Si stripes allow excitation of SPPs that are localized inside the band gap with grating coupling. The cavity state is formed due to periodic effective index modulation obtained by one harmonic of the grating and loaded Si stripes. More complicated grating structures such as metallic Moiré surfaces have also been shown to form a localized state inside the band gap when excited with Kretschmann configuration.

  12. Fabrication of Polymer Optical Fibre (POF) Gratings

    PubMed Central

    Luo, Yanhua; Yan, Binbin; Zhang, Qijin; Peng, Gang-Ding; Wen, Jianxiang; Zhang, Jianzhong

    2017-01-01

    Gratings inscribed in polymer optical fibre (POF) have attracted remarkable interest for many potential applications due to their distinctive properties. This paper overviews the current state of fabrication of POF gratings since their first demonstration in 1999. In particular we summarize and discuss POF materials, POF photosensitivity, techniques and issues of fabricating POF gratings, as well as various types of POF gratings. PMID:28273844

  13. Digital TV-echelle spectrograph for simultaneous multielemental analysis using microcomputer control

    SciTech Connect

    Davidson, J.B.; Case, A.L.

    1980-12-01

    A digital TV-echelle spectrograph with microcomputer control was developed for simultaneous multielemental analysis. The optical system is a commercially available unit originally equipped for film and photomultiplier (single element) readout. The film port was adapted for the intensifier camera. The camera output is digitized and stored in a microcomputer-controlled, 512 x 512 x 12 bit memory and image processor. Multiple spectra over the range of 200 to 800 nm are recorded in a single exposure. Spectra lasting from nanoseconds to seconds are digitized and stored in 0.033 s and displayed on a TV monitor. An inexpensive microcomputer controls the exposure, reads and displays the intensity of predetermined spectral lines, and calculates wavelengths of unknown lines. The digital addresses of unknown lines are determined by superimposing a cursor on the TV display. The microcomputer also writes into memory wavelength fiducial marks for alignment of the TV camera.

  14. A reduction package for cross-dispersed echelle spectrograph data in IDL

    NASA Astrophysics Data System (ADS)

    Hall, Jeffrey C.; Neff, James E.

    1992-12-01

    We have written in IDL a data reduction package that performs reduction and extraction of cross-dispersed echelle spectrograph data. The present package includes a complete set of tools for extracting data from any number of spectral orders with arbitrary tilt and curvature. Essential elements include debiasing and flatfielding of the raw CCD image, removal of scattered light background, either nonoptimal or optimal extraction of data, and wavelength calibration and continuum normalization of the extracted orders. A growing set of support routines permits examination of the frame being processed to provide continuing checks on the statistical properties of the data and on the accuracy of the extraction. We will display some sample reductions and discuss the algorithms used. The inherent simplicity and user-friendliness of the IDL interface make this package a useful tool for spectroscopists. We will provide an email distribution list for those interested in receiving the package, and further documentation will be distributed at the meeting.

  15. First Studies with the Compact Echelle Spectrograph for Aeronomical Research (CESAR)

    NASA Astrophysics Data System (ADS)

    Slanger, T. G.; Hedin, J.; Matsiev, D.

    2014-12-01

    The CESAR echelle spectrograph has been in operation at Poker Flat Research Range since November 2013. High-resolution spectra (R ~ 5000) of both the nightglow and the aurorae have been obtained, and the data overlap the time period in which measurements from the PINOT campaign were made. It has been of particular interest to search for regions in which the O2(b-X) Atmospheric band system could be studied with minimal interference from auroral N2/N2+ features. The b-X 2-1 band at 697 nm is such a feature. At longer wavelengths we have ascertained that CESAR is capable of making measurements on the N(2P-2D) lines near 1040 nm, an extremely strong multiplet where the wavelength region has prevented systematic measurements. Controversially, earlier studies had indicated that these lines suffered interference from the N2 First Positive 0-0 band, which we do not find in our limited sample.

  16. A list of tantalum lines for the wavelength calibration of the Hamilton echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Pakhomov, Yu. V.

    2015-10-01

    A solution to the problem of wavelength calibration for Hamilton echelle spectrographs using a hollow cathode lamp operating at the Lick Observatory Shane telescope until June 9, 2011 is presented. The spectrum of the nominally thorium—argon lamp also contains, in addition to lines of thorium and argon, a number of unknown lines identified with tantalum. Atomic data for measured lines of tantalum and thorium are used to estimate the temperature of the gas in the lamp, T = 3120 ± 60 K. All all lines of TaI and TaII visible in the lamp spectrum have been selected from the VALD3 atomic line database, and a list compiled for use in the processing of spectral observations. The accuracy of this calibration approach is limited by the influence of hyperfine line splitting.

  17. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Steinmetz, T.; Holzwarth, R.; Kentischer, T.; Schmidt, W.

    2012-10-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

  18. Transformation a Echelle Fixe et Groupe de Renormalisation pour les Objets Fractals et Multifractals

    NASA Astrophysics Data System (ADS)

    Tremblay, Real

    Dans un premier temps, la description mathematique des fractals et des multifractais est resumee. Une description de quelques-uns des principaux systemes ou apparaissent des spectres d'exposants multifractals est presentee. L'accent est mis sur deux archetypes, le modele de percolation et le modele de rupture dielectrique. Un modele original de cascade multifractale avec interactions inspire des modeles phenomenologiques de la turbulence est presente et son spectre d'exposants calcule analytiquement. Ce travail elargit la classe de modeles pour lesquels on connait le spectre d'exposants exactement. Dans la seconde partie, on trouve une analyse critique de la transformation a echelle fixe. Sont discutees plus particulierement les proprietes que doivent posseder les diagrammes de base pour obtenir une transformation invariante d'echelle. Les differentes hypotheses arbitraires de la theorie sont mises en evidence. L'une de ces hypotheses concerne le traitement auto-coherent des conditions aux frontieres. Considerant cette hypothese comme valable, la theorie utilise la distribution de trous dans un ensemble de Cantor aleatoire. Un calcul exact de cette distribution est donne ici. Enfin, en troisieme et dernier lieu, on retrouve une analyse exhaustive du probleme du crossover dans le modele de percolation avec une resistance non-nulle pour les liens normalement isolants. A l'aide du groupe de renormalisation de Migdal-Kadanoff, on montre qu'il existe un seul exposant de crossover et une seule longueur de coherence. D'autres longueurs de correlation peuvent etre definies, mais elles demeurent dans un rapport fixe le long des axes propres du groupe de renormalisation. La multifractalite est donc, pour ce modele et ceux qui peuvent etre formules de facon analogue, compatible avec l'existence d'une seule longueur de coherence. Ces resultats sont d'application directe pour les proprietes electriques des milieux desordonnes.

  19. Waveguide silicon nitride grating coupler

    NASA Astrophysics Data System (ADS)

    Litvik, Jan; Dolnak, Ivan; Dado, Milan

    2016-12-01

    Grating couplers are one of the most used elements for coupling of light between optical fibers and photonic integrated components. Silicon-on-insulator platform provides strong confinement of light and allows high integration. In this work, using simulations we have designed a broadband silicon nitride surface grating coupler. The Fourier-eigenmode expansion and finite difference time domain methods are utilized in design optimization of grating coupler structure. The fully, single etch step grating coupler is based on a standard silicon-on-insulator wafer with 0.55 μm waveguide Si3N4 layer. The optimized structure at 1550 nm wavelength yields a peak coupling efficiency -2.6635 dB (54.16%) with a 1-dB bandwidth up to 80 nm. It is promising way for low-cost fabrication using complementary metal-oxide- semiconductor fabrication process.

  20. Fiber Grating Environmental Sensing System

    DOEpatents

    Schulz, Whitten L.; Udd, Eric

    2003-07-29

    Fiber grating environmental measurement systems are comprised of sensors that are configured to respond to changes in moisture or chemical content of the surrounding medium through the action of coatings and plates inducing strain that is measured. These sensors can also be used to monitor the interior of bonds for degradation due to aging, cracking, or chemical attack. Means to multiplex these sensors at high speed and with high sensitivity can be accomplished by using spectral filters placed to correspond to each fiber grating environmental sensor. By forming networks of spectral elements and using wavelength division multiplexing arrays of fiber grating sensors may be processed in a single fiber line allowing distributed high sensitivity, high bandwidth fiber optic grating environmental sensor systems to be realized.

  1. ZEUS: A Submillimeter Grating Spectrometer for Exploring Distant Galaxies

    NASA Astrophysics Data System (ADS)

    Nikola, Tomas; Hailey-Dunsheath, Steven; Stacey, Gordon J.; Benford, Dominic J.; Moseley, Samuel H., Jr.; Staguhn, Johannes G.

    2003-02-01

    The redshift (Z) and of Early Universe Spectrometer (ZEUS) is a long slit echelle grating spectrometer that we are constructing for use in the submillimeter (350μm, 450μm, and 610μm) windows on the James Clerk Maxwell Telescope (JCMT). ZEUS has a resolving power of R≡λ/ΔΛ~1000, optimized for detecting broad, faint lines from extragalactic sources. The detector is a 16×32 pixel array of pop-up bolometers equipped with superconducting transition edge sensors linked into a SQUID multiplexed readout. This array should provide the requisite sensitivity at ~300mK, a temperature easily achieved using a two stage 3He refrigerator. ZEUS is optimized to quickly obtain spectra of point sources over very broad bands in the submillimeter windows. In the 350μm window, ZEUS will provide an instantaneous 27 resolution element spectrum, for each of 16 spatial elements on the sky. The roughly 10% bandwidth 350μm window can therefore be covered with just four settings of the grating. Each pixel is mapped into 5" on the sky (roughly 1•λ/D at 350 μm), so that the field of view is 5"×80". At 610μm, the slit is opened to 12" (2.4 pixels) resulting in a resolving power of around 500. ZEUS can quickly change wavelength or telluric window, adapting well to the demanding weather conditions in the short submillimeter windows. To minimize the effects of stray background radiation, two cold cut-on filters are used, together with 300mK band pass filters mounted on a filter wheel. This filter train fully sorts the echelle grating order, blocking unwanted radiation, but with high submillimeter band transmission. The expected point source sensitivities for 370μm, 444μm, and 610μm are 2.7×1017 W m-2Hz-1/2, 1.2×10-17 W m-2Hz-1/2, and 1.6×10-17W m-2Hz-1/2, respectively. Our primary scientific objectives are to (1) Investigate Ultraluminous Infrared Galaxies (ULIGs) via their (CI) and mid-J CO line emission-what are the origins of their tremendous infrared (IR) luminosities? Why

  2. Apodized Volume Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Mokhov, Sergiy

    2015-03-01

    Reflective and transmissive volume Bragg grating (VBGs) are widely used in high power laser applications because of their large operational aperture and robustness. They are fabricated in photosensitive material through holographic recording of uniform interference pattern of two overlapping coherent waves obtained by splitting a flat-top shaped laser beam. The following thermal treatment produces permanent refractive index modulation (RIM). Reflective VBGs have fringes parallel to operational anti-reflective coated surfaces and they demonstrate narrow reflection bandwidth. Transmissive VBGs are cut with fringes perpendicular to surfaces and they are characterized by narrow angular selectivity. Uniform RIM causes secondary lobes in corresponding reflection and transmission spectra due to sharp boundary conditions for volume Bragg diffraction. We propose to create apodization of RIM by recording two interference patterns with slightly different parameters in the same volume which would create slow varying moire envelope of amplitude of RIM. Cutting the specimen at zeros of moire envelope with one sine semi-period thickness will produce VBGs apodized at sides which will reduce parasitic secondary lobes in spectra. In reflection geometry, two patterns of the same orientation with slightly different periods are required for apodization along Bragg wave vector. In transmission case, recording of the same interference patterns with small mutual rotation angle provides apodization in direction perpendicular to Bragg wave vector. Modeling results show significant improvement in selective properties of VBGs with such moire apodization.

  3. Diffraction by dual-period gratings.

    PubMed

    Skigin, Diana C; Depine, Ricardo A

    2007-03-20

    The dynamical characteristics of dual-period perfectly conducting gratings are explored. Gratings with several grooves (reflection) or slits (transmission) within each period are considered. A scalar approach is proposed to derive the general characteristics of the diffracted response. It was found that compound gratings can be designed to cancel as well as to intensify a given diffraction order. These preliminary estimations for finite gratings are validated by numerical examples for infinitely periodic reflection and transmission gratings with finite thickness, performed using an extension of the rigorous modal method to compound gratings, for both polarization cases.

  4. Near-perfect diffraction grating rhomb

    DOEpatents

    Wantuck, Paul J.

    1990-01-01

    A near-perfect grating rhomb enables an output beam to be diffracted to an angle offset from the input beam. The correcting grating is tipped relative to the dispersing grating to provide the offset angle. The correcting grating is further provided with a groove spacing which differs from the dispersing grating groove space by an amount effective to substantially remove angular dispersion in the output beam. A near-perfect grating rhomb has the capability for selective placement in a FEL to suppress sideband instabilities arising from the FEL.

  5. Fiber Bragg grating multichemical sensor

    NASA Astrophysics Data System (ADS)

    Boland, Patrick; Sethuraman, Gopakumar; Mendez, Alexis; Graver, Tom; Pestov, Dmitry; Tait, Gregory

    2006-10-01

    Fiber optic-based chemical sensors are created by coating fiber Bragg gratings (FBG) with the glassy polymer cellulose acetate (CA). CA is a polymeric matrix capable of localizing or concentrating chemical constituents within its structure. Some typical properties of CA include good rigidity (high modulus) and high transparency. With CA acting as a sensor element, immersion of the gratings in various chemical solutions causes the polymer to expand and mechanically strain the glass fiber. This elongation of the fiber sections containing the grating causes a corresponding change in the periodicity of the grating that subsequently results in a change in the Bragg-reflected wavelengths. A high-resolution tunable fiber ring laser interrogator is used to obtain room-temperature reflectance spectrograms from two fiber gratings at two different wavelengths - 1540nm and 1550nm. The graphical representation from this device enables the display of spectral shape, and not merely shifts in FBG central wavelength, thereby allowing for more comprehensive analysis of how different physical conditions cause the reflectance profile to move and alter overall form. Wavelength shifts on the order of 1 to 80 pm in the FBG transition edges and changes in spectral shape are observed in both sensors upon immersion in a diverse selection of chemical analytes.

  6. Exploiting a Transmission Grating Spectrometer

    SciTech Connect

    Ronald E. Bell

    2004-12-08

    The availability of compact transmission grating spectrometers now allows an attractive and economical alternative to the more familiar Czerny-Turner configuration for many high-temperature plasma applications. Higher throughput is obtained with short focal length refractive optics and stigmatic imaging. Many more spectra can be obtained with a single spectrometer since smaller, more densely packed optical input fibers can be used. Multiple input slits, along with a bandpass filter, can be used to maximize the number of spectra per detector, providing further economy. Curved slits can correct for the strong image curvature of the short focal length optics. Presented here are the governing grating equations for both standard and high-dispersion transmission gratings, defining dispersion, image curvature, and desired slit curvature, that can be used in the design of improved plasma diagnostics.

  7. CSHELL: a high spectral resolution 1-5 um cryogenic echelle spectrograph for the IRTF

    NASA Astrophysics Data System (ADS)

    Greene, Thomas P.; Tokunaga, Alan T.; Toomey, Douglas W.; Carr, Jonathan B.

    1993-10-01

    A 1 - 5.4 micrometers Cryogenic Echelle Spectrograph (CSHELL) for the NASA Infrared Telescope Facility is described. It achieves a resolving power of 5,000 to 40,000 using slits ranging from 4.0' to 0.5' in width and 30' long. It operates in a single-order long-slit mode, and a circular variable filter is used as an order sorter. Two infrared arrays are employed to achieve spectral coverage from 1 - 5.4 micrometers : a 256 X 256 HgCdTe NICMOS-3 array for 1 - 2.5 micrometers and a SBRC 58 X 62 InSb array for 2.8 - 5.4 micrometers . A closed- cycle cooler is employed to keep the optics and supporting structure at 73 K and to maintain the detectors at their proper operating temperatures. The entire spectrograph fits within an envelope of 64 cm X 35 cm X 27 cm. The instrument is controlled by a microcomputer mounted on the telescope, but the observer commands the instrument from a UNIX X Windows workstation on the Internet. This use of the Internet for communication between instrument control and user interface computers facilitates remote observing. A limiting magnitude of 12.3 mag is achieved for S/N equals 10 in 1 hour integration time, at resolving power of 20,000 at 2.2 micrometers wavelength.

  8. PEPSI: the Potsdam Echelle Polarimetric and Spectroscopic Instrument for the LBT

    NASA Astrophysics Data System (ADS)

    Strassmeier, K. G.; Woche, M.; Ilyin, I.; Popow, E.; Bauer, S.-M.; Dionies, F.; Fechner, T.; Weber, M.; Hofmann, A.; Storm, J.; Materne, R.; Bittner, W.; Bartus, J.; Granzer, T.; Denker, C.; Carroll, T.; Kopf, M.; DiVarano, I.; Beckert, E.; Lesser, M.

    2008-07-01

    We present the status of PEPSI, the bench-mounted fibre-fed and stabilized "Potsdam Echelle Polarimetric and Spectroscopic Instrument" for the 2×8.4m Large Binocular Telescope in southern Arizona. PEPSI is under construction at AIP and is scheduled for first light in 2009/10. Its ultra-high-resolution mode will deliver an unprecedented spectral resolution of approximately R=310,000 at high efficiency throughout the entire optical/red wavelength range 390-1050nm without the need for adaptive optics. Besides its polarimetric Stokes IQUV mode, the capability to cover the entire optical range in three exposures at resolutions of 40,000, 130,000 and 310,000 will surpass all existing facilities in terms of light-gathering-power times spectral-coverage product. A solar feed will make use of the spectrograph also during day time. As such, we hope that PEPSI will be the most powerful spectrometer of its kind for the years to come.

  9. Full image spectral analysis of elemental emissions from an echelle spectrograph

    SciTech Connect

    Spencer, W.A.

    2000-01-27

    A new algorithm compares the background corrected echelle emission image obtained from reference standards to images of unknowns for quantitative elemental analyses. Wavelength was not used in the calculations but instead pixel position and intensity. The data reduction solution was unique to the particular detector/spectrometer. The approach was found useful for several types of images including ICP, DCP and glow discharge images. The analysis scheme required that the emission pattern of standards and background be held in memory. A dual weighting scheme was used that decreased the importance of pixels in high background areas and enhanced the importance of signals from pixels where the standards had emissions. Threshold values were used to limit the calculations to signals in the linear range of the electronics. Logarithmic weighting, (by taking the square root), was found to work well for weighting pixels from the standards. This assured that minor emissions had some influence on the data fit. In the program the best-fit scalar was determined using simple iterative guess, change and test approaches. The test looked for the minimum least square residual value in the areas of the flagged pixels.

  10. A search for lithium in Pleiades brown dwarf candidates using the Keck hires echelle

    NASA Technical Reports Server (NTRS)

    Marcy, Geoffrey W.; Basri, Gibor; Graham, James R.

    1994-01-01

    We report Keck Observatory high-resolution echelle spectra of lithium at 670.8 nm in two of the lowest luminosity brown dwarf candidates in the Pleiades. These objects have estimated masses of 0.055 to 0.059 solar mass from their location on a color-magnitude diagram relative to theoretical isochrones. Stellar interior models predict that Li has not burned in them. However, we find no evidence of the Li line, at limits 100 to 1000 times below the initial abundance. This indicates that Li has in fact been depleted, presumably by nuclear processing as occurs in Pleiades stars. Interior models suggest that such large Li depletion occurs only for objects with M greater than 0.09 solar mass at the age of the Pleiades. Thus, it is unlikely that the candidates are brown dwarfs. The brown dwarf candidates present a conflict: either they have masses greater than suggested from their placement on the H-R diagram, or they do have the very low suggested masses but are nonetheless capable of destroying Li, in only 70 Myr. Until this dilemma is resolved, the photometric identification of brown dwarfs will remain difficult. Resolution may reside in higher T(sub eff) derived from optical and IR colors or in lower T(sub eff) in the interior models.

  11. Simplified modal method for slanted grating

    NASA Astrophysics Data System (ADS)

    Li, Shubin; Zhou, Changhe; Jia, Wei

    2017-01-01

    We report the simplified modal method for the slanted grating based on the accurate dispersion equation. The vividly physical insight is presented to interpret the diffraction process for slanted grating. We also present that the simplified modal method with the two-lowest mode condition is effective for a large slanted angle up to 26°. By examining the eignefunction, the mode index, and the two-lowest mode condition, we provide new evidences to verify the assumption that a slanted grating with subwavelength period can be analyzed as an equivalent rectangular grating using the simplified modal method, which is right and convenient to use for a small slanted angle up to 20°. Numerical simulations of the simplified modal method are coincident with rigorous coupled wave analysis for small slanted angle gratings. Thus the simplified modal method can be used for small slanted angle grating since the equivalence of slanted grating and rectangular grating is verified due to its vivid physical analysis.

  12. HIRDES - The high-resolution double-echelle spectrograph for the World Space Observatory Ultraviolet (WSO/UV)

    NASA Astrophysics Data System (ADS)

    Werner, K.; Wso/Uv-Hirdes Team

    The World Space Observatory Ultraviolet WSO UV is a multi-national project grown out of the needs of the astronomical community to have future access to the ultraviolet range of the electromagnetic spectrum The development of the WSO UV S C and the telescope is headed by the Russian Federal Space Agency Roscosmos The mission is scheduled to be launched in 2010 into the L2 orbit The WSO UV consists of a single Ultraviolet Telescope incorporating a primary mirror of 1 7 m diameter feeding UV spectrometer and UV imagers The UV spectrometer comprises three different single spectrographs two high resolution echelle spectrographs - the High Resolution Double Echelle Spectrograph HIRDES - and a low dispersion long slit instrument Within the HIRDES the spectral band 102 - 310 nm is separated to feed two echelle spectrographs covering the UV range between 174 and 310 nm UVES and the Vacuum-UV range between 102 and 176 nm VUVES with a very high spectral resolution of 50000 Each spectrograph encompasses a stand-alone optical bench structure with a fully redundant high-speed MCP detector system the optomechanics and a network of mechanisms with different functionalities The fundamental technical concept is based on the heritage of the two previous ORFEUS-SPAS missions The phase B1 development activities are described in this paper under consideration of performance aspects design drivers the related trade offs e g mechanical concepts material selection MCP detector efficiency etc and the critical functional and environmental test

  13. Near-infrared echelle-AOTF spectrometer ACS-NIR for the ExoMars Trace Gas Orbiter

    NASA Astrophysics Data System (ADS)

    Trokhimovskiy, Alexander; Korablev, Oleg; Kalinnikov, Yurii K.; Fedorova, Anna; Stepanov, Alexander V.; Titov, Andrei Y.; Dziuban, Ilia; Patrakeev, Andrei; Montmessin, Franck

    2015-09-01

    The near-Infrared echelle-AOTF spectrometer is one channel of the Atmospheric Chemistry Suite (ACS) package dedicated for the studies of the Martian atmosphere on board ExoMars Trace Gas Orbiter planned for launch in 2016. The near-infrared (NIR) channel of ACS is a versatile spectrometer for the spectral range of 0.7-1.6 μm with a resolving power of <20,000. The NIR channel is intended to measure the atmospheric water vapor, aerosols, airglows, in nadir, in solar occultation, and on the limb. The science goals of NIR are basically the same as for SPICAM IR channel presently in flight on board Mars Express ESA orbiter, but it offers significantly better spectral resolution. The instrument employs the principle of an echelle spectrometer with an acoustooptical tunable filter (AOTF) as a preselector. The same principle was employed in SOIR, operated on Venus Express ESA mission in 2006-2014, and in RUSALKA, operated onboard ISS in 2009-2012. The NIR channel of ACS consists of entry optics, the AOTF, a Littrow echelle spectrometer, and an electrically cooled InGaAs detector array. It is a complete block with power and data interfaces, and the overall mass of 3.2 kg. The protoflight model of NIR is completed, calibrated, integrated within the ACS suite, and is undergoing tests at the spacecraft.

  14. Surface-core fiber gratings

    NASA Astrophysics Data System (ADS)

    Osório, Jonas H.; Oliveira, Ricardo; Mosquera, L.; Franco, Marcos A. R.; Heidarialamdarloo, Jamshid; Bilro, Lúcia; Nogueira, Rogério N.; Cordeiro, Cristiano M. B.

    2015-09-01

    In this paper, we report, to our knowledge, the first demonstration of the induction of long-period and Bragg gratings on surface-core optical fibers. Surface-core fibers described herein were fabricated from commercial silica tubes and germanium-doped silica rods by employing a very simple procedure. Being the core on the fiber surface, it can be sensitive to refractive index variations in the environment in which the fiber is immersed. Thus, results concerning the sensitivity of these gratings to environmental refractive index variations are presented. Besides, simulation data are presented for comparison to the experimental behavior and for projecting future steps in this research.

  15. A Composite Grating for Moire Interferometry.

    DTIC Science & Technology

    1987-07-01

    shown in Figure 7 in which two virtual reference gratings of frequencies 2400 and 600 lines/mm were used. This arrangement corresponds to a fringe...fields at the two virtual reference grating frequencies of 2400/600 lines/mm. The light paths of the two virtual reference gratings are controlled by...frequencies were selectively recorded. Figure 10 and 11 shows two moire fringe patterns for virtual reference grating frequencies of 2400 lines/mm and 600

  16. Advanced Fibre Bragg Grating and Microfibre Bragg Grating Fabrication Techniques

    NASA Astrophysics Data System (ADS)

    Chung, Kit Man

    Fibre Bragg gratings (FBGs) have become a very important technology for communication systems and fibre optic sensing. Typically, FBGs are less than 10-mm long and are fabricated using fused silica uniform phase masks which become more expensive for longer length or non-uniform pitch. Generally, interference UV laser beams are employed to make long or complex FBGs, and this technique introduces critical precision and control issues. In this work, we demonstrate an advanced FBG fabrication system that enables the writing of long and complex gratings in optical fibres with virtually any apodisation profile, local phase and Bragg wavelength using a novel optical design in which the incident angles of two UV beams onto an optical fibre can be adjusted simultaneously by moving just one optical component, instead of two optics employed in earlier configurations, to vary the grating pitch. The key advantage of the grating fabrication system is that complex gratings can be fabricated by controlling the linear movements of two translation stages. In addition to the study of advanced grating fabrication technique, we also focus on the inscription of FBGs written in optical fibres with a cladding diameter of several ten's of microns. Fabrication of microfibres was investigated using a sophisticated tapering method. We also proposed a simple but practical technique to filter out the higher order modes reflected from the FBG written in microfibres via a linear taper region while the fundamental mode re-couples to the core. By using this technique, reflection from the microfibre Bragg grating (MFBG) can be effectively single mode, simplifying the demultiplexing and demodulation processes. MFBG exhibits high sensitivity to contact force and an MFBG-based force sensor was also constructed and tested to investigate their suitability for use as an invasive surgery device. Performance of the contact force sensor packaged in a conforming elastomer material compares favourably to one

  17. Embedded high-contrast distributed grating structures

    DOEpatents

    Zubrzycki, Walter J.; Vawter, Gregory A.; Allerman, Andrew A.

    2002-01-01

    A new class of fabrication methods for embedded distributed grating structures is claimed, together with optical devices which include such structures. These new methods are the only known approach to making defect-free high-dielectric contrast grating structures, which are smaller and more efficient than are conventional grating structures.

  18. Diffraction gratings used as identifying markers

    DOEpatents

    Deason, Vance A.; Ward, Michael B.

    1991-01-01

    A finely detailed defraction grating is applied to an object as an identifier or tag which is unambiguous, difficult to duplicate, or remove and transfer to another item, and can be read and compared with prior readings with relative ease. The exact pattern of the defraction grating is mapped by diffraction moire techniques and recorded for comparison with future readings of the same grating.

  19. 3D Printed Terahertz Focusing Grating Couplers

    NASA Astrophysics Data System (ADS)

    Jahn, David; Weidenbach, Marcel; Lehr, Jannik; Becker, Leonard; Beltrán-Mejía, Felipe; Busch, Stefan F.; Balzer, Jan C.; Koch, Martin

    2017-02-01

    We have designed, constructed and characterized a grating that focuses electromagnetic radiation at specific frequencies out of a dielectric waveguide. A simple theoretical model predicts the focusing behaviour of these chirped gratings, along with numerical results that support our assumptions and improved the grating geometry. The leaky waveguide was 3D printed and characterized at 120 GHz demonstrating its potential for manipulating terahertz waves.

  20. Electromagnetically induced grating with maximal atomic coherence

    SciTech Connect

    Carvalho, Silvania A.; Araujo, Luis E. E. de

    2011-10-15

    We describe theoretically an atomic diffraction grating that combines an electromagnetically induced grating with a coherence grating in a double-{Lambda} atomic system. With the atom in a condition of maximal coherence between its lower levels, the combined gratings simultaneously diffract both the incident probe beam as well as the signal beam generated through four-wave mixing. A special feature of the atomic grating is that it will diffract any beam resonantly tuned to any excited state of the atom accessible by a dipole transition from its ground state.

  1. The grating as an accelerating structure

    SciTech Connect

    Fernow, R.C.

    1991-02-01

    This report considers the use of a diffraction grating as an accelerating structure for charged particle beams. We examine the functional dependence of the electromagnetic fields above the surface of a grating. Calculations are made of the strength of the accelerating modes for structures with {pi} and 2{pi} phase advance per period and for incident waves polarized with either the E or H vector along the grooves of the grating. We consider examples of using gratings in a laser linac and in a grating lens. We also briefly examine previous results published about this subject. 36 refs.

  2. The science case of the PEPSI high-resolution echelle spectrograph and polarimeter for the LBT

    NASA Astrophysics Data System (ADS)

    Strassmeier, K. G.; Pallavicini, R.; Rice, J. B.; Andersen, M. I.

    2004-05-01

    We lay out the scientific rationale for and present the instrumental requirements of a high-resolution adaptive-optics Echelle spectrograph with two full-Stokes polarimeters for the Large Binocular Telescope (LBT) in Arizona. Magnetic processes just like those seen on the Sun and in the space environment of the Earth are now well recognized in many astrophysical areas. The application to other stars opened up a new field of research that became widely known as the solar-stellar connection. Late-type stars with convective envelopes are all affected by magnetic processes which give rise to a rich variety of phenomena on their surface and are largely responsible for the heating of their outer atmospheres. Magnetic fields are likely to play a crucial role in the accretion process of T-Tauri stars as well as in the acceleration and collimation of jet-like flows in young stellar objects (YSOs). Another area is the physics of active galactic nucleii (AGNs) , where the magnetic activity of the accreting black hole is now believed to be responsible for most of the behavior of these objects, including their X-ray spectrum, their notoriously dramatic variability, and the powerful relativistic jets they produce. Another is the physics of the central engines of cosmic gamma-ray bursts, the most powerful explosions in the universe, for which the extreme apparent energy release are explained through the collimation of the released energy by magnetic fields. Virtually all the physics of magnetic fields exploited in astrophysics is somehow linked to our understanding of the Sun's and the star's magnetic fields.

  3. Study of Extra-Solar Planets with the Advanced Fiber Optic Echelle

    NASA Technical Reports Server (NTRS)

    Noyes, Robert W.; Boyce, Joseph M. (Technical Monitor)

    2002-01-01

    This is the final report of NASA Grant NAG5-7505, for 'Study of Extra-solar Planets with the Advanced Fiber Optic Echelle'. This program was funded in response to our proposal submitted under NASA NRA 97-OSS-06, with a total period of performance from June 1, 1998 through Feb 28 2002. Principal Investigator is Robert W. Noyes; co-Investigators are Sylvain G. Korzennik (SAO), Peter Niserison (SAO), and Timothy M. Brown (High Altitude Observatory). Since the start of this program we have carried out more than 30 observing runs, typically of 5 to 7 days duration. We obtained a total of around 2000 usable observations of about 150 stars, where a typical observation consists of 3 exposures of 10 minutes each. Using this data base we detected thc two additional planetary companions to the star Upsilon Andromedae. This detection was made independently of, and essentially simultaneously with, a similar detection by the Berkeley group (Marcy et al): the fact that two data sets were completely independent and gave essentially the same orbital parameters for this three-planet system gave a strong confirmation of this important result. We also extended our previous detection of the planet orbiting Rho Coronae Borealis to get a better determination of its orbital eccentricity: e=0.13 +/- 0.05. We detected a new planet in orbit around the star HD 89744, with orbital period 256 days, semi-major axis 0.88 AU, eccentricity 0.70, and minimum mass m sini = 7.2 m(sub Jup). This discovery is significant because of the very high orbital eccentricity, arid also because HD 89744 has both high metallicity [Fe/H] and at the same time a low [C/Fe] abundance ratio.

  4. Curved VPH gratings for novel spectrographs

    NASA Astrophysics Data System (ADS)

    Clemens, J. Christopher; O'Donoghue, Darragh; Dunlap, Bart H.

    2014-07-01

    The introduction of volume phase holographic (VPH) gratings into astronomy over a decade ago opened new possibilities for instrument designers. In this paper we describe an extension of VPH grating technology that will have applications in astronomy and beyond: curved VPH gratings. These devices can disperse light while simultaneously correcting aberrations. We have designed and manufactured two different kinds of convex VPH grating prototypes for use in off-axis reflecting spectrographs. One type functions in transmission and the other in reflection, enabling Offnerstyle spectrographs with the high-efficiency and low-cost advantages of VPH gratings. We will discuss the design process and the tools required for modelling these gratings along with the recording layout and process steps required to fabricate them. We will present performance data for the first convex VPH grating produced for an astronomical spectrograph.

  5. Cross-fiber Bragg grating transducer

    NASA Technical Reports Server (NTRS)

    Albin, Sacharia (Inventor); Zheng, Jianli (Inventor); Lavarias, Arnel (Inventor)

    2000-01-01

    A transducer has been invented that uses specially-oriented gratings in waveguide a manner that allows the simultaneous measurement of physical phenomena (such as shear force, strain and temperature) in a single sensing element. The invention has a highly sensitive, linear response and also has directional sensitivity with regard to strain. The transducer has a waveguide with a longitudinal axis as well as two Bragg gratings. The transducer has a first Bragg grating associated with the waveguide that has an angular orientation .theta..sub.a relative to a perpendicular to the longitudinal axis such that 0.degree.<.theta..sub.a <.theta..sub.max. The second Bragg grating is associated with the waveguide in such a way that the angular orientation .theta..sub.b of the grating relative to a perpendicular to the longitudinal axis is (360.degree.-.theta..sub.max)<.theta..sub.b <360.degree.. The first Bragg grating can have a periodicity .LAMBDA..sub.a and the second Bragg grating can have a periodicity .LAMBDA..sub.b such that the periodicity .LAMBDA..sub.a of the first Bragg grating does not equal the periodicity .LAMBDA..sub.b of the second Bragg grating. The angle of the gratings can be such that .theta..sub.a =360.degree.-.theta..sub.b. The waveguide can assume a variety of configurations, including an optical fiber, a rectangular waveguide and a planar waveguide. The waveguide can be fabricated of a variety of materials, including silica and polymer material.

  6. High Efficiency Germanium Immersion Gratings

    SciTech Connect

    Kuzmenko, P J; Davis, P J; Little, S L; Little, L M; Bixler, J V

    2006-05-01

    We have fabricated several germanium immersion gratings by single crystal, single point diamond flycutting on an ultra-precision lathe. Use of a dead sharp tool produces groove corners less than 0.1 micron in radius and consequently high diffraction efficiency. We measured first order efficiencies in immersion of over 80% at 10.6 micron wavelength. Wavefront error was low averaging 0.06 wave rms (at 633 nm) across the full aperture. The grating spectral response was free of ghosts down to our detection limit of 1 part in 10{sup 4}. Scatter should be low based upon the surface roughness. Measurement of the spectral line profile of a CO{sub 2} laser sets an upper bound on total integrated scatter of 0.5%.

  7. Panel Discussion On Grating Technology

    NASA Astrophysics Data System (ADS)

    Chi, Chang H.; Garvin, Hugh L.; Loewen, Erwin G.; Hunter, William R.; Lerner, Jeremy M.; Hutley, Michael C.

    1981-02-01

    CC: I would like to ask the panel four questions of general interest, and since our time is rather limited, I would like to ask you to try to limit your comments to three or four minutes. The questions are the following: 1. How would you characterize the progress of grating technology over the past 5 years, particularly in the area of theoretical analysis, experimental applications, and diagnostics? 2. What are the areas that need innovative ideas and technical break-throughs. This question is addressed more for the benefit of younger people. Suppose we have, for example, a Ph.D. student wanting to do a thesis; in what areas would you like to suggest they put their study time in? 3. What are the major problems in the grating technology community? Do they include funding, work force (are we educating enough talent in the Universities?), industrial secrecy, government assistance, international cooperation, patent protection, or any other items? 4. What actions can you suggest to promote the welfare of the grating technology community? Has it been worthwhile to come to this conference? Are there some things that we can change? What recommendations do von feel we should make?

  8. KiwiSpec: The Design and Performance of a High Resolution Echelle Spectrograph for Astronomy

    NASA Astrophysics Data System (ADS)

    Gibson, Steven Ross

    This document describes the design, analysis, construction and testing of KiwiSpec, a fibre-fed, high resolution astronomical spectrograph of an asymmetric white pupil design. The instrument employs an R4, 31.6 groove mm-1 échelle grating for primary dispersion and a 725 lines mm-1 volume phase holographic (VPH) based grism for cross-dispersion. Two versions of the prototype were designed and constructed: an 'in-air' prototype, and a prototype featuring a vacuum chamber (to increase the stability of the instrument). The KiwiSpec optical design is introduced, as well as a description of the theory behind a cross-dispersed échelle spectrograph. The results of tolerancing the optical design are reported for alignment, optical fabrication, and optical surface quality groups of parameters. The optical windows of an iodine cell are also toleranced. The opto-mechanical mounts of both prototypes are described in detail, as is the design of the vacuum chamber system. Given the goal of 1 m/s radial velocity stability, analyses were undertaken to determine the allowable amount of movement of the vacuum windows, and to determine the allowable changes in temperature and pressure within and outside of the vacuum chamber. The spectral efficiency of the instrument was estimated through a predictive model; this was calculated for the as-built instrument and also for an instrument with ideal, high-efficiency coatings. Measurements of the spectral efficiency of various components of the instrument are reported, as well as a description of the measurement system developed to test the efficiency of VPH gratings. On-sky efficiency measurements from use of KiwiSpec on the 1-m McLellan telescope at Mt John University Observatory are reported. Two possible exposure meter locations are explored via an efficiency model, and also through the measurement of the zero-order reflectivity of the échelle grating. Various stability aspects of the design are investigated. These include the

  9. s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

    NASA Astrophysics Data System (ADS)

    García-Rojas, J.; Madonna, S.; Luridiana, V.; Sterling, N. C.; Morisset, C.; Delgado-Inglada, G.; Toribio San Cipriano, L.

    2015-09-01

    The chemical content of the planetary nebula NGC 3918 is investigated through deep, high-resolution (R ˜ 40 000) UVES (Ultraviolet-Visual Echelle Spectrograph) at VLT (Very Large Telescope) spectrophotometric data. We identify and measure more than 750 emission lines, making ours one of the deepest spectra ever taken for a planetary nebula. Among these lines we detect very faint lines of several neutron-capture elements (Se, Kr, Rb, and Xe), which enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up in NGC 3918 progenitor star. We find that Kr is strongly enriched in NGC 3918 and that Se is less enriched than Kr, in agreement with the results of previous papers and with predicted s-process nucleosynthesis. We also find that Xe is not as enriched by the s-process in NGC 3918 as is Kr and, therefore, that neutron exposure is typical of modestly subsolar metallicity asymptotic giant branch (AGB) stars. A clear correlation is found when representing [Kr/O] versus log(C/O) for NGC 3918 and other objects with detection of multiple ions of Kr in optical data, confirming that carbon is brought to the surface of AGB stars along with s-processed material during third dredge-up episodes, as predicted by nucleosynthesis models. We also detect numerous refractory element lines (Ca, K, Cr, Mn, Fe, Co, Ni, and Cu) and a large number of metal recombination lines of C, N, O, and Ne. We compute physical conditions from a large number of diagnostics, which are highly consistent among themselves assuming a three-zone ionization scheme. Thanks to the high ionization of NGC 3918 we detect a large number of recombination lines of multiple ionization stages of C, N, O and Ne. The abundances obtained for these elements by using recently determined state-of-the-art ionization correction factor (ICF) schemes or simply adding ionic abundances are in very good agreement, demonstrating the quality

  10. Heavy Element Abundances in Planetary Nebulae from Deep Optical Echelle Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mashburn, Amanda; Sterling, Nicholas C.; Dinerstein, Harriet L.; Garofali, Kristen; Jensema, Rachael; Turbyfill, Amanda; Wieser, Hannah-Marie N.; Reed, Evan C.; Redfield, Seth

    2016-01-01

    We present the abundances of neutron(n)-capture elements (atomic number Z > 30) and iron determined from deep optical echelle spectroscopy of 14 Galactic planetary nebulae (PNe). The spectra were obtained with the 2D-coudé spectrograph on the 2.7-m Harlan J. Smith telescope at McDonald Observatory. The abundances of n-capture elements can be enhanced in PNe due to slow n-capture nucleosynthesis in the progenitor asymptotic giant branch (AGB) stars. The high spectral resolution of these data (R = 36,700) allow most n-capture element emission lines to be resolved from other nebular and telluric features. We detect Kr in all of the observed PNe (with multiple ions detected in several objects), while Br, Rb, and Xe were each detected in 4--5 objects. Using the new Kr ionization correction factors (ICFs) of Sterling et al. (2015, ApJS, 218, 25), we find [Kr/O] abundances ranging from 0.05 to 1.1 dex. We utilize approximate ICFs for the other n-capture elements, and find slightly lower enrichments for Br and Rb (-0.1 to 0.7 dex), while Xe is enhanced relative to solar by factors of two to 30. The [Xe/Kr] ratios range from -0.3 to 1.4 dex, indicating a significant range in neutron exposures in PN progenitor stars. Interestingly, the largest [Xe/Kr] ratio is found in the thick-disk PN NGC 6644, which has a lower metallicity than the other observed PNe. We detect iron emission lines in all but one target. Fe can be depleted into dust grains in ionized nebulae, and its abundance thus provides key information regarding dust-to-gas ratios and grain destruction processes. We find that [Fe/O] ranges from -1.3 to -0.7 dex in the observed PNe, a smaller spread of depletion factors than found in recent studies (Delgado-Inglada & Rodriguez 2014, ApJ, 784, 173) though this may be due in part to our smaller sample. These data are part of a larger study of heavy elements in PNe, which will provide more accurate determinations of n-capture element abundances than previous estimates in

  11. Optical fiber grating tuning device and application

    NASA Astrophysics Data System (ADS)

    Luo, Fei; Yeh, T.

    2008-12-01

    A new design for tuning optical fiber grating is proposed. The fiber grating is placed in the grooves between a pair of slides, in which one end of the fiber is bonded on the bottom slide, and the other end of the fiber is bonded on the top slide, the grating section of the fiber is confined in grooves, so that the fiber grating is remaining straight without buckling during axial compressive force applied to the fiber. An actuator is used for driving slide to apply force on fiber to axially compress or stretch the fiber grating. The wavelength of the fiber grating is tuned according to applied stress on the fiber. The applications of the device include tunable fiber laser, tunable fiber filter etc.

  12. Interlaced spin grating for optical wave filtering

    NASA Astrophysics Data System (ADS)

    Linget, H.; Chanelière, T.; Le Gouët, J.-L.; Berger, P.; Morvan, L.; Louchet-Chauvet, A.

    2015-02-01

    Interlaced spin grating is a scheme for the preparation of spectrospatial periodic absorption gratings in an inhomogeneously broadened absorption profile. It relies on the optical pumping of atoms in a nearby long-lived ground state sublevel. The scheme takes advantage of the sublevel proximity to build large contrast gratings with unlimited bandwidth and preserved average optical depth. It is particularly suited to Tm-doped crystals in the context of classical and quantum signal processing. In this paper, we study the optical pumping dynamics at play in an interlaced spin grating and describe the corresponding absorption profile shape in an optically thick atomic ensemble. We show that, in Tm:YAG, the diffraction efficiency of such a grating can reach 18.3 % in the small-angle and 11.6 % in the large-angle configuration when the excitation is made of simple pulse pairs, considerably outperforming conventional gratings.

  13. Varied line-space gratings and applications

    SciTech Connect

    McKinney, W.R.

    1991-07-15

    This paper presents a straightforward analytical and numerical method for the design of a specific type of varied line-space grating system. The mathematical development will assume plane or nearly-plane spherical gratings which are illuminated by convergent light, which covers many interesting cases for synchrotron radiation. The gratings discussed will have straight grooves whose spacing varies across the principal plane of the grating. Focal relationships and formulae for the optical grating-pole-to-exist-slit distance and grating radius previously presented by other authors will be derived with a symbolic algebra system. It is intended to provide the optical designer with the tools necessary to design such a system properly. Finally, some possible advantages and disadvantages for application to synchrotron to synchrotron radiation beamlines will be discussed.

  14. Diffraction gratings used as identifying markers

    SciTech Connect

    Deason, V.A.; Ward, M.B.

    1989-08-03

    A finely detailed defraction grating is applied to an object as an identifier or tag which is unambiguous, difficult to duplicate, or remove and transfer to another item, and can be read and compared with prior readings with relative ease. The exact pattern of the defraction grating is mapped by diffraction moire techniques and recorded for comparison with future readings of the same grating. 7 figs.

  15. Diffraction gratings used as identifying markers

    DOEpatents

    Deason, V.A.; Ward, M.B.

    1991-03-26

    A finely detailed diffraction grating is applied to an object as an identifier or tag which is unambiguous, difficult to duplicate, or remove and transfer to another item, and can be read and compared with prior readings with relative ease. The exact pattern of the diffraction grating is mapped by diffraction moire techniques and recorded for comparison with future readings of the same grating. 7 figures.

  16. Active diffraction gratings: Development and tests

    NASA Astrophysics Data System (ADS)

    Bonora, S.; Frassetto, F.; Zanchetta, E.; Della Giustina, G.; Brusatin, G.; Poletto, L.

    2012-12-01

    We present the realization and characterization of an active spherical diffraction grating with variable radius of curvature to be used in grazing-incidence monochromators. The device consists of a bimorph deformable mirror on the top of which a diffraction grating with laminar profile is realized by UV lithography. The experimental results show that the active grating can optimize the beam focalization of visible wavelengths through its rotation and focus accommodation.

  17. Gap soliton propagation in optical fiber gratings

    NASA Astrophysics Data System (ADS)

    Mohideen, U.; Slusher, R. E.; Mizrahi, V.; Erdogan, T.; Kuwata-Gonokami, M.; Lemaire, P. J.; Sipe, J. E.; Martijn de Sterke, C.; Broderick, Neil G. R.

    1995-08-01

    Intense optical pulse propagation in a GeO2 -doped silica glass fiber grating results in nonlinear pulse propagation velocities and increased transmission at wavelengths where the grating reflects light in the linear limit. These nonlinear pulse propagation effects are predicted by numerical simulations of gap soliton propagation. The large linear refractive-index variations used for the fiber gratings in these experiments permit the propagation of gap solitons in short lengths of fiber.

  18. Focusing Diffraction Grating Element with Aberration Control

    NASA Technical Reports Server (NTRS)

    Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christoph M.

    2010-01-01

    Diffraction gratings are optical components with regular patterns of grooves, which angularly disperse incoming light by wavelength in a single plane, called dispersion plane. Traditional gratings on flat substrates do not perform wavefront transformation in the plane perpendicular to the dispersion plane. The device proposed here exhibits regular diffraction grating behavior, dispersing light. In addition, it performs wavelength transformation (focusing or defocusing) of diffracted light in a direction perpendicular to the dispersion plane (called sagittal plane). The device is composed of a diffraction grating with the grooves in the form of equidistant arcs. It may be formed by defining a single arc or an arc approximation, then translating it along a certain direction by a distance equal to a multiple of a fixed distance ("grating period") to obtain other groove positions. Such groove layout is nearly impossible to obtain using traditional ruling methods, such as mechanical ruling or holographic scribing, but is trivial for lithographically scribed gratings. Lithographic scribing is the newly developed method first commercially introduced by LightSmyth Technologies, which produces gratings with the highest performance and arbitrary groove shape/spacing for advanced aberration control. Unlike other types of focusing gratings, the grating is formed on a flat substrate. In a plane perpendicular to the substrate and parallel to the translation direction, the period of the grating and, therefore, the projection of its k-vector onto the plane is the same for any location on the grating surface. In that plane, no waveform transformation by the grating k-vector occurs, except of simple redirection.

  19. Polarization Measurements on SUMI's TVLS Gratings

    NASA Technical Reports Server (NTRS)

    Kobayashi, K.; West, E. A.; Davis, J. M.; Gary, G. A.

    2007-01-01

    We present measurements of toroidal variable-line-space (TVLS) gratings for the Solar Ultraviolet Magnetograph Investigation (SUMI), currently being developed at the National Space Science and Technology Center (NSSTC). SUMI is a spectro-polarimeter designed to measure magnetic fields in the solar chromosphere by observing two UV emission lines sensitive to magnetic fields, the CIY line at 155nm and the MgII line at 280nm. The instrument uses a pair of TVLS gratings, to observe both linear polarizations simultaneously. Efficiency measurements were done on bare aluminum gratings and aluminum/MgF2 coated gratings, at both linear polarizations.

  20. The diffraction grating - An opinionated appraisal.

    NASA Technical Reports Server (NTRS)

    Harrison, G. R.

    1973-01-01

    As a dispersing device for spectroscopy, the prism was by 1950 being supplanted by the diffraction grating, which provided broader spectrum coverage, gave higher intrinsic dispersion, and was more flexible to use. Today most gratings are three-dimensional and blazed, being embossed with thousands of identical mirrors. The relative merits of gratings in comparison with new interferometric scanning devices are examined, taking into account Fourier spectroscopy. Problems of grating ruling are discussed together with the status of ruling engines, and questions of ruling with mechanical engines.

  1. Astronomical large Ge immersion grating by Canon

    NASA Astrophysics Data System (ADS)

    Sukegawa, Takashi; Suzuki, Takeshi; Kitamura, Tsuyoshi

    2016-07-01

    Immersion grating is a powerful optical device for thee infrared high-resolution spectroscope. Germanium (GGe) is the best material for a mid-infrared immersion grating because of Ge has very large reflective index (n=4.0). On the other hands, there is no practical Ge immersion grating under 5umm use. It was very difficult for a fragile IR crystal to manufacture a diffraction grating precisely. Our original free-forming machine has accuracy of a few nano-meter in positioning and stability. We already fabricated the large CdZnTe immersion grating. (Sukegawa et al. (2012), Ikeda et al. (2015)) Wee are developing Ge immersion grating that can be a good solution for high-resolution infrared spectroscopy with the large ground-based/space telescopes. We succeeded practical Ge immersion grating with the grooved area off 75mm (ruled direction) x 119mm (grove width) and the blaze angle of 75 degrees. Our astronomical large Ge immersion grating has the grooved area of 155mm (ruled direction) x 41mmm (groove width) and groove pitch off 91.74um. We also report optical performance of astronomical large Ge immersion grating with a metal coating on the diffraction surface.

  2. Fiber optic diffraction grating maker

    DOEpatents

    Deason, V.A.; Ward, M.B.

    1991-05-21

    A compact and portable diffraction grating maker is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate. 4 figures.

  3. Fiber optic diffraction grating maker

    DOEpatents

    Deason, Vance A.; Ward, Michael B.

    1991-01-01

    A compact and portable diffraction grating maker comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent beam splitters, and collimating lenses or mirrors directing the split beam at an appropriate photosensitive material. The collimating optics, the output ends of the fiber optic coupler and the photosensitive plate holder are all mounted on an articulated framework so that the angle of intersection of the beams can be altered at will without disturbing the spatial filter, collimation or beam quality, and assuring that the beams will always intersect at the position of the plate.

  4. Optical grating evaluator - A device for detailed measurement of diffraction grating efficiencies in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Michels, D. J.; Hunter, W. R.; Mikes, T. L.

    1974-01-01

    A device for detailed measurement of diffraction grating efficiencies and over-all performance in the VUV has been designed and constructed at the Naval Research Laboratory. The system employs semiautomated mechanisms to scan the face of the grating with a narrow monochromatic beam, and an efficiency map of the grating surface is produced on a strip chart recorder. Grating efficiency in the various diffracted orders and intensity of light scattered between orders may also be measured. A unique feature is the ability to determine the angle and effectiveness of grating blaze and variations in blaze under different conditions of illumination.

  5. Tilt sensitivity of the two-grating interferometer

    SciTech Connect

    Anderson, Christopher N.; Naulleau, Patrick P.

    2008-01-30

    Fringe formation in the two-grating interferometer is analyzed in the presence of a small parallelism error between the diffraction gratings assumed in the direction of grating shear. Our analysis shows that with partially coherent illumination, fringe contrast in the interference plane is reduced in the presence of nonzero grating tilt with the effect proportional to the grating tilt angle and the grating spatial frequencies. Our analysis also shows that for a given angle between the gratings there is an angle between the final grating and the interference plane that optimizes fringe contrast across the field.

  6. Grating lobes analysis based on blazed grating theory for liquid crystal optical-phased array

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Cui, Guolong; Kong, Lingjiang; Xiao, Feng; Liu, Xin; Zhang, Xiaoguang

    2013-09-01

    The grating lobes of the liquid crystal optical-phased array (LCOPA) based on blazed grating theory is studied. Using the Fraunhofer propagation principle, the analytical expressions of the far-field intensity distribution are derived. Subsequently, we can obtain both the locations and the intensities of the grating lobes. The derived analytical functions that provide an insight into single-slit diffraction and multislit interference effect on the grating lobes are discussed. Utilizing the conventional microwave-phased array technique, the intensities of the grating lobes and the main lobe are almost the same. Different from this, the derived analytical functions demonstrate that the intensities of the grating lobes are less than that of the main lobe. The computer simulations and experiments show that the proposed method can correctly estimate the locations and the intensities of the grating lobes for a LCOPA simultaneously.

  7. Inquiry with Laser Printer Diffraction Gratings

    ERIC Educational Resources Information Center

    Van Hook, Stephen J.

    2007-01-01

    The pages of "The Physics Teacher" have featured several clever designs for homemade diffraction gratings using a variety of materials--cloth, lithographic film, wire, compact discs, parts of aerosol spray cans, and pseudoliquids and pseudosolids. A different and inexpensive method I use to make low-resolution diffraction gratings takes advantage…

  8. Advanced Bragg grating filters for DWDM applications

    NASA Astrophysics Data System (ADS)

    Sokolov, Victor I.; Khudobenko, Alexander I.; Panchenko, Vladislav Y.

    2002-09-01

    The advent of the technology of Dense Wavelength Division Multiplexing (DWDM) in Optical Fiber Networks (OFNs) has resulted in the necessity of developing advanced Optical Add/Drop Multiplexers (OADMs) on the basis of submicron Bragg gratings. The OADMs for dense multichannel OFNs with bit rates 10 - 40 Gbits/s per channel and channel spacing 200, 100 and 50 GHz must possess rectangular-shaped reflection/transmission spectra and linear phase characteristic within the stop/passband. These features can not be achieved with uniform periodic Bragg gratings and therefore nonuniform gratings with space-modulated coupling coefficient should be used. We present the recent advances in the design and fabrication of narrowband wavelength-selective optical filters for DWDM applications on the basis of single-mode fibers with side-polishing and periodic relief Bragg gratings with apodized coupling coefficient. The peculiarities of propagation, interaction and diffraction of electromagnetic waves in nonuniform Bragg grating structures are considered. Narrowband reflection filters based on side-polished fibers and submicron relief gratings on SiO2 and SiO materials are designed and fabricated. The filters have stopband width 0.4 - 0.8 nm and peak reflectivity R > 98% in the 1.55 mkm wavelength communication region. Narrowband flat-top reflection filters for DWDM applications based on side-polished fibers and periodic relief Bragg gratings are designed. The schemes for multichannel integration of Bragg grating filters into OFNs are presented.

  9. Polarizing binary diffraction grating beam splitter.

    PubMed

    Davis, Jeffrey A; Evans, Garrett H

    2004-07-01

    We report a polarizing beam splitter that uses binary phase gratings written onto a liquid-crystal spatial light modulator. These gratings produce several linearly polarized diffracted orders and a zeroth-order beam whose polarization state can be completely controlled. Experimental results are shown.

  10. On grating nulls in adaptive arrays

    NASA Astrophysics Data System (ADS)

    Ishide, A.; Compton, R. T., Jr.

    1980-07-01

    The effect of element patterns on grating nulls in adaptive arrays is considered. Two simple array models, a two-element and a three-element array with dipole element patterns, are used to study this question. The element patterns are assumed unequal (i.e., the beam maxima point in different directions). It is shown that element patterns greatly affect the occurrence of grating nulls in the array. Unequal element patterns cause extra grating nulls ('sign reversal grating nulls') to occur, in addition to conventional grating nulls. These sign reversal grating nulls can occur even with element spacing less than a half-wavelength. For a two-element array with dipole element patterns, it turns out that grating nulls cannot be avoided if the spacing is greater than a half-wavelength. However, with more than two elements, the situation is not so bleak. An example is given of a three-element array with dipole patterns and one-wavelength spacing in which all grating nulls are eliminated.

  11. On grating nulls in adaptive arrays

    NASA Astrophysics Data System (ADS)

    Ishide, A.; Compton, R. T., Jr.

    1980-03-01

    This report considers the effect of element patterns on grating nulls in adaptive arrays. Two simple array models, a two-element and a three-element array with dipole element patterns, are used to study this question. The element patterns are assumed unequal (i.e., the beam maxima point in different directions). It is shown that element patterns greatly affect the occurrence of grating nulls in the array. Unequal element patterns cause extra grating nulls (sign reversal grating nulls) to occur, in addition to conventional grating nulls. These sign reversal grating nulls can occur even with element spacing less than a half-wavelength. For a two-element array with dipole element patterns, it turns out that grating nulls cannot be avoided if the spacing is greater than a half wavelength. However, with more than two elements, the situation is not so bleak. An example is given of a three-element array with dipole patterns and one wavelength spacing in which all grating nulls are eliminated.

  12. Fiber grating systems for traffic monitoring

    NASA Astrophysics Data System (ADS)

    Udd, Eric; Kunzler, Marley; Laylor, Harold M.; Schulz, Whitten L.; Kreger, Stephen T.; Corones, John C.; McMahon, Robert; Soltesz, Steven M.; Edgar, Robert

    2001-08-01

    Blue Road Research has designed, built, and installed fiber grating sensor systems onto bridges, and most recently into an asphalt and concrete highway test pad. The sensitivity levels of the fiber grating sensors are sufficiently high to enable detection of people standing on the bridge or highway. This paper briefly overviews the usage of these sensors for traffic monitoring.

  13. Grating droplets with a mesh

    NASA Astrophysics Data System (ADS)

    Soto, Dan; Le Helloco, Antoine; Clanet, Cristophe; Quere, David; Varanasi, Kripa

    2016-11-01

    A drop thrown against a mesh can pass through its holes if impacting with enough inertia. As a result, although part of the droplet may remain on one side of the sieve, the rest will end up grated through the other side. This inexpensive method to break up millimetric droplets into micrometric ones may be of particular interest in a wide variety of applications: enhancing evaporation of droplets launched from the top of an evaporative cooling tower or preventing drift of pesticides sprayed above crops by increasing their initial size and atomizing them at the very last moment with a mesh. In order to understand how much liquid will be grated we propose in this presentation to start first by studying a simpler situation: a drop impacting a plate pierced with a single off centered hole. The study of the role of natural parameters such as the radius drop and speed or the hole position, size and thickness allows us to discuss then the more general situation of a plate pierced with multiple holes: the mesh.

  14. Scatterometry measurement of asymmetric gratings

    NASA Astrophysics Data System (ADS)

    Li, Jie; Hwu, Justin J.; Liu, Yongdong; Rabello, Silvio; Liu, Zhuan; Hu, Jiangtao

    2009-12-01

    Scatterometry has been used extensively for the characterization of critical dimensions (CD) and detailed sidewall profiles of periodic structures in microelectronics fabrication processes. So far the majority of applications are for symmetric gratings. In most cases devices are designed to be symmetric although errors could occur during fabrication process and result in undesired asymmetry. The problem with conventional optical scatterometry techniques lies in the lack of capability to distinguish between left and right asymmetries. In this work we investigate the possibility of measuring grating asymmetry using Mueller matrix spectroscopic ellipsometry (MM-SE). A patterned hard disk prepared by nano-imprint technique is used for the study. The relief image on the disk sometimes has asymmetrical sidewall profile, presumably due to the uneven separation of the template from the disk. The undesired tilting resist profile causes difficulties to the downstream processes or even makes them fail. Cross-section SEM reveals that the asymmetrical resist lines are typically tilted towards the outer diameter direction. The simulation and experimental data show that certain Mueller matrix elements are proportional to the direction and amplitude of profile asymmetry, providing a direct indication to the sidewall tilting. The tilting parameter can be extracted using rigorous optical critical dimension (OCD) modeling or calibration method. We demonstrate that this technique has good sensitivity for measuring and distinguishing left and right asymmetry caused by sidewall tilting, and can therefore be used for monitoring processes, such as lithography and etch processing, for which symmetric structures are desired.

  15. Birefringence compensated arrayed waveguide grating

    NASA Astrophysics Data System (ADS)

    Zou, Jun; Xia, Xiang; Lang, Tingting; He, Jian-Jun

    2014-10-01

    In this paper we review our work on birefringence compensated arrayed waveguide grating. We elaborate on a birefringence compensation technique based on angled star couplers in arrayed waveguide grating (AWG) and discuss several demonstrations both in low-index-contrast and high-index-contrast material systems. A 16-channel AWG with 100GHz channel spacing for DWDM application is designed and fabricated in silica-based low-index-contrast waveguide. The experimental results confirm that the polarization-dependent wavelength shift (PDλ) can be tuned by varying the incident/diffraction angle at the star couplers and a birefringence-free property can be achieved without additional fabrication process as compared to conventional AWG. A further validation of this technique is demonstrated in high-index-contrast silicon-on-insulator waveguide, in combination with different diffraction orders for TE and TM polarizations. A birefringence compensated silicon nanowire AWG for CWDM optical interconnects is designed and fabricated. The theoretical and experimental results show that the PDλ can be reduced from 380-420nm to 0.5-3.5 nm, below 25% of the 3 dB bandwidth of the channel response in the wavelength range of 1500 to 1600nm.

  16. Micro Ring Grating Spectrometer with Adjustable Aperture

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Choi, Sang H. (Inventor)

    2012-01-01

    A spectrometer includes a micro-ring grating device having coaxially-aligned ring gratings for diffracting incident light onto a target focal point, a detection device for detecting light intensity, one or more actuators, and an adjustable aperture device defining a circular aperture. The aperture circumscribes a target focal point, and directs a light to the detection device. The aperture device is selectively adjustable using the actuators to select a portion of a frequency band for transmission to the detection device. A method of detecting intensity of a selected band of incident light includes directing incident light onto coaxially-aligned ring gratings of a micro-ring grating device, and diffracting the selected band onto a target focal point using the ring gratings. The method includes using an actuator to adjust an aperture device and pass a selected portion of the frequency band to a detection device for measuring the intensity of the selected portion.

  17. Profile measurement taken with liquid-crystal gratings.

    PubMed

    Kakunai, S; Sakamoto, T; Iwata, K

    1999-05-01

    Profile measurement taken with liquid-crystal gratings and a phase-shifting technique is proposed, and its effectiveness is verified by experiment. The surface profile is obtained by measurement of the phase distributions of the sinusoidal gratings deformed by an object's surface. The liquid-crystal grating gives an accurate phase shift, an arbitrary projection pitch, and a constant surface brightness compared with conventional gratings such as a laser interference fringe grating and a Ronchi grating. Therefore a flexible measuring system may be developed with it. Two gratings with different pitches are used to measure an object with large steps. A two-color projection system can be used to produce such gratings simultaneously. Locally varying reflectivity on a surface can also be compensated by adjustment of the color component of the projected grating with a liquid-crystal grating. Thus the contrast in the projected grating can be made uniform, and a good profile measurement can be accomplished.

  18. Unexpected series of regular frequency spacing of δ Scuti stars in the non-asymptotic regime. II. Sample-Echelle diagrams and rotation

    SciTech Connect

    Paparo, M.; Benko, J. M.; Hareter, M.; Guzik, J. A.

    2016-06-17

    A sequence search method was developed for searching for regular frequency spacing in δ Scuti stars by visual inspection (VI) and algorithmic search. The sample contains 90 δ Scuti stars observed by CoRoT. An example is given to represent the VI. The algorithm (SSA) is described in detail. The data treatment of the CoRoT light curves, the criteria for frequency filtering, and the spacings derived by two methods (i.e., three approaches: VI, SSA, and FT) are given for each target. Echelle diagrams are presented for 77 targets for which at least one sequence of regular spacing was identified. Comparing the spacing and the shifts between pairs of echelle ridges revealed that at least one pair of echelle ridges is shifted to midway between the spacing for 22 stars. The estimated rotational frequencies compared to the shifts revealed rotationally split doublets, triplets, and multiplets not only for single frequencies, but for the complete echelle ridges in 31 δ Scuti stars. Furthermore, using several possible assumptions for the origin of the spacings, we derived the large separation (${\\rm{\\Delta }}\

  19. Unexpected Series of Regular Frequency Spacing of δ Scuti Stars in the Non-asymptotic Regime. II. Sample-Echelle Diagrams and Rotation

    NASA Astrophysics Data System (ADS)

    Paparó, M.; Benkő, J. M.; Hareter, M.; Guzik, J. A.

    2016-06-01

    A sequence search method was developed for searching for regular frequency spacing in δ Scuti stars by visual inspection (VI) and algorithmic search. The sample contains 90 δ Scuti stars observed by CoRoT. An example is given to represent the VI. The algorithm (SSA) is described in detail. The data treatment of the CoRoT light curves, the criteria for frequency filtering, and the spacings derived by two methods (i.e., three approaches: VI, SSA, and FT) are given for each target. Echelle diagrams are presented for 77 targets for which at least one sequence of regular spacing was identified. Comparing the spacing and the shifts between pairs of echelle ridges revealed that at least one pair of echelle ridges is shifted to midway between the spacing for 22 stars. The estimated rotational frequencies compared to the shifts revealed rotationally split doublets, triplets, and multiplets not only for single frequencies, but for the complete echelle ridges in 31 δ Scuti stars. Using several possible assumptions for the origin of the spacings, we derived the large separation ({{Δ }}ν ) that are distributed along the mean density versus large separations relation derived from stellar models.

  20. Unexpected series of regular frequency spacing of δ Scuti stars in the non-asymptotic regime. II. Sample-Echelle diagrams and rotation

    DOE PAGES

    Paparo, M.; Benko, J. M.; Hareter, M.; ...

    2016-06-17

    A sequence search method was developed for searching for regular frequency spacing in δ Scuti stars by visual inspection (VI) and algorithmic search. The sample contains 90 δ Scuti stars observed by CoRoT. An example is given to represent the VI. The algorithm (SSA) is described in detail. The data treatment of the CoRoT light curves, the criteria for frequency filtering, and the spacings derived by two methods (i.e., three approaches: VI, SSA, and FT) are given for each target. Echelle diagrams are presented for 77 targets for which at least one sequence of regular spacing was identified. Comparing the spacing and the shifts between pairs of echelle ridges revealed that at least one pair of echelle ridges is shifted to midway between the spacing for 22 stars. The estimated rotational frequencies compared to the shifts revealed rotationally split doublets, triplets, and multiplets not only for single frequencies, but for the complete echelle ridges in 31 δ Scuti stars. Furthermore, using several possible assumptions for the origin of the spacings, we derived the large separation (more » $${\\rm{\\Delta }}\

  1. Assessment of the most effective part of echelle laser-induced plasma spectra for further classification using Czerny-Turner spectrometer

    NASA Astrophysics Data System (ADS)

    Pořízka, Pavel; Klus, Jakub; Prochazka, David; Vítková, Gabriela; Brada, Michal; Novotný, Jan; Novotný, Karel; Kaiser, Jozef

    2016-10-01

    The objective of this work was to assess a part of echelle Laser-Induced Plasma spectra (ranging from 200 to 1000 nm) that could be most effectively employed for rocks classification. Therefore, a 60 nm wide spectral window mask was iteratively moved over the broadband echelle spectra. Each created narrow artificial spectral windows (60 nm) was used for the classification of rock samples using various Multivariate Data Analysis (MVDA) algorithms, reaching more than 99% of the overall accuracy in certain cases. Afterwards, the Czerny-Turner spectrometer (having higher sensitivity compared to the echelle spectrometer) was aligned to the a priori selected and the most effective spectral regions and rocks samples were re-measured. Consequently the MVDA analyses were utilized again, providing also satisfying classification results yielding more than 99% of the overall accuracy. Measurements of 28 sedimentary ores (certified reference materials) were done utilizing commercially available X-Trace device (AtomTrace), where spectrometers in both configurations (echelle and Czerny-Turner) were exploited.

  2. Fabricating Radial Groove Gratings Using Projection Photolithography

    NASA Technical Reports Server (NTRS)

    Iazikov, Dmitri; Mossberg, Thomas W.

    2009-01-01

    Projection photolithography has been used as a fabrication method for radial grove gratings. Use of photolithographic method for diffraction grating fabrication represents the most significant breakthrough in grating technology in the last 60 years, since the introduction of holographic written gratings. Unlike traditional methods utilized for grating fabrication, this method has the advantage of producing complex diffractive groove contours that can be designed at pixel-by-pixel level, with pixel size currently at the level of 45 45 nm. Typical placement accuracy of the grating pixels is 10 nm over 30 nm. It is far superior to holographic, mechanically ruled or direct e-beam written gratings and results in high spatial coherence and low spectral cross-talk. Due to the smooth surface produced by reactive ion etch, such gratings have a low level of randomly scattered light. Also, due to high fidelity and good surface roughness, this method is ideally suited for fabrication of radial groove gratings. The projection mask is created using a laser writer. A single crystal silicon wafer is coated with photoresist, and then the projection mask, with its layer of photoresist, is exposed for patterning in a stepper or scanner. To develop the photoresist, the fabricator either removes the exposed areas (positive resist) of the unexposed areas (negative resist). Next, the patterned and developed photoresist silicon substrate is subjected to reactive ion etching. After this step, the substrate is cleaned. The projection mask is fabricated according to electronic design files that may be generated in GDS file format using any suitable CAD (computer-aided design) or other software program. Radial groove gratings in off-axis grazing angle of incidence mount are of special interest for x-ray spectroscopy, as they allow achieving higher spectral resolution for the same grating area and have lower alignment tolerances than traditional in-plane grating scheme. This is especially

  3. Combined plasmonic gratings in organic solar cells.

    PubMed

    Shen, Honghui; Maes, Bjorn

    2011-11-07

    We propose an organic solar cell structure with combined silver gratings consisting of both a front and a back grating. This combination provides multiple, semi-independent enhancement mechanisms which act additively, so that a broadband absorption is obtained. Both gratings couple the incident light into various plasmonic modes, showing a more localized or propagating character respectively. In addition, some modes only appear for tilted incident light, and therefore present a complex angle-dependent behavior. We provide extensive numerical simulations, resulting in an optimized period of 490 nm, with front grating elements of 60 by 10nm and back elements of 60 by 30 nm. With these parameters an integrated absorption enhancement factor around 1.35 is observed, with absorption increasing from 48% to 65% under TM polarized light. In addition, the solar cell with combined gratings is much less sensitive to the angle of incident light than the single grating cases. Furthermore, the grating structure does not have a large influence on the TE polarized light absorption.

  4. Diffraction Grating Structures in Solar Cells

    SciTech Connect

    ZAIDI,SALEEM H.; GEE,JAMES M.; RUBY,DOUGLAS S.

    2000-12-01

    Sub-wavelength periodic texturing (gratings) of crystalline-silicon (c-Si) surfaces for solar cell applications can be designed for maximizing optical absorption in thin c-Si films. We have investigated c-Si grating structures using rigorous modeling, hemispherical reflectance, and internal quantum efficiency measurements. Model calculations predict almost {approximately}100% energy coupling into obliquely propagating diffraction orders. By fabrication and optical characterization of a wide range of 1D & 2D c-Si grating structures, we have achieved broad-band, low ({approximately} 5%) reflectance without an anti-reflection film. By integrating grating structures into conventional solar cell designs, we have demonstrated short-circuit current density enhancements of 3.4 and 4.1 mA/cm{sup 2} for rectangular and triangular 1D grating structures compared to planar controls. The effective path length enhancements due to these gratings were 2.2 and 1.7, respectively. Optimized 2D gratings are expected to have even better performance.

  5. Long period grating response to gamma radiation

    NASA Astrophysics Data System (ADS)

    Sporea, Dan; Stǎncalie, Andrei; Neguţ, Daniel; Delepine-Lesoille, Sylvie; Lablonde, Laurent

    2016-04-01

    We report the evaluation of one long period grating (LPG) and one fiber Bragg grating (FBG) under gamma irradiation. The LPG was produced by the melting-drawing method based on CO2 laser assisted by a micro-flame and was engraved in a commercial single mode fiber SMF28 from Corning, grating length 25 mm, grating pitch of 720 μm. After the manufacturing of the grating, the fiber was re-coated with Acrylate and the grating was inserted into special ceramic case transparent to gamma radiation. The FBG is commercialized by Technica SA, and it is written in SMF-28 optical fiber (λ= 1546 nm; grating length of 12 mm; reflectivity > 80 %; bandwidth - BW @3 dB < 0.3 nm; side lobe suppress ratio - SLSR >15 dB; Acrylate recoating). By on-line monitoring of the LPG wavelength deep with an optical fiber interrogator during the irradiation exposure and pauses, both the irradiation induced shift (maximum 1.45 nm) and the recovery (in the range of 200 pm) phenomena were observed. Temperature sensitivity of the LPS was not affected by gamma irradiation.

  6. Deformed ellipsoidal diffraction grating blank

    NASA Technical Reports Server (NTRS)

    Decew, Alan E., Jr.

    1994-01-01

    The Deformed Ellipsoidal Grating Blank (DEGB) is the primary component in an ultraviolet spectrometer. Since one of the major concerns for these instruments is throughput, significant efforts are made to reduce the number of components and subsequently reflections. Each reflection results in losses through absorption and scattering. It is these two sources of photon loss that dictated the requirements for the DEGB. The first goal is to shape the DEGB in such a way that the energy at the entrance slit is focused as well as possible on the exit slit. The second goal is to produce a surface smooth enough to minimize the photon loss due to scattering. The program was accomplished in three phases. The first phase was the fabrication planning. The second phase was the actual fabrication and initial testing. The last phase was the final testing of the completed DEGB.

  7. Phasor Analysis of Binary Diffraction Gratings with Different Fill Factors

    ERIC Educational Resources Information Center

    Martinez, Antonio; Sanchez-Lopez, Ma del Mar; Moreno, Ignacio

    2007-01-01

    In this work, we present a simple analysis of binary diffraction gratings with different slit widths relative to the grating period. The analysis is based on a simple phasor technique directly derived from the Huygens principle. By introducing a slit phasor and a grating phasor, the intensity of the diffracted orders and the grating's resolving…

  8. Fiber Bragg Grating Sensors for Harsh Environments

    PubMed Central

    Mihailov, Stephen J.

    2012-01-01

    Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments. PMID:22438744

  9. Optical Fiber Grating Hydrogen Sensors: A Review

    PubMed Central

    Dai, Jixiang; Zhu, Li; Wang, Gaopeng; Xiang, Feng; Qin, Yuhuan; Wang, Min; Yang, Minghong

    2017-01-01

    In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests due to their good reliability and distributed measurements. This review paper mainly focuses on optical fiber hydrogen sensors associated with fiber gratings and various materials. Their configurations and sensing performances proposed by different groups worldwide are reviewed, compared and discussed in this paper. Meanwhile, the challenges for fiber grating hydrogen sensors are also addressed. PMID:28287499

  10. Aplanatic and quasi-aplanatic diffraction gratings

    DOEpatents

    Hettrick, M.C.

    1987-09-14

    A reflection diffraction grating having a series of transverse minute grooves of progressively varying spacing along a concave surface enables use of such gratings for x-ray or longer wavelength imaging of objects. The variable groove spacing establishes aplanatism or substantially uniform magnetification across the optical aperture. The grating may be sued, for example, in x-ray microscopes or telescopes of the imaging type and in x-ray microprobed. Increased spatial resolution and field of view may be realized in x-ray imaging. 5 figs.

  11. Optical Fiber Grating Hydrogen Sensors: A Review.

    PubMed

    Dai, Jixiang; Zhu, Li; Wang, Gaopeng; Xiang, Feng; Qin, Yuhuan; Wang, Min; Yang, Minghong

    2017-03-12

    In terms of hydrogen sensing and detection, optical fiber hydrogen sensors have been a research issue due to their intrinsic safety and good anti-electromagnetic interference. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive research interests due to their good reliability and distributed measurements. This review paper mainly focuses on optical fiber hydrogen sensors associated with fiber gratings and various materials. Their configurations and sensing performances proposed by different groups worldwide are reviewed, compared and discussed in this paper. Meanwhile, the challenges for fiber grating hydrogen sensors are also addressed.

  12. Sensitive visual test for concave diffraction gratings.

    NASA Technical Reports Server (NTRS)

    Bruner, E. C., Jr.

    1972-01-01

    A simple visual test for the evaluation of concave diffraction gratings is described. It is twice as sensitive as the Foucault knife edge test, from which it is derived, and has the advantage that the images are straight and free of astigmatism. It is particularly useful for grating with high ruling frequency where the above image faults limit the utility of the Foucault test. The test can be interpreted quantitatively and can detect zonal grating space errors of as little as 0.1 A.

  13. Diffraction by m-bonacci gratings

    NASA Astrophysics Data System (ADS)

    Monsoriu, Juan A.; Giménez, Marcos H.; Furlan, Walter D.; Barreiro, Juan C.; Saavedra, Genaro

    2015-11-01

    We present a simple diffraction experiment with m-bonacci gratings as a new interesting generalization of the Fibonacci ones. Diffraction by these non-conventional structures is proposed as a motivational strategy to introduce students to basic research activities. The Fraunhofer diffraction patterns are obtained with the standard equipment present in most undergraduate physics labs and are compared with those obtained with regular periodic gratings. We show that m-bonacci gratings produce discrete Fraunhofer patterns characterized by a set of diffraction peaks which positions are related to the concept of a generalized golden mean. A very good agreement is obtained between experimental and numerical results and the students’ feedback is discussed.

  14. Aplanatic and quasi-aplanatic diffraction gratings

    DOEpatents

    Hettrick, Michael C.

    1989-01-01

    A reflection diffraction grating having a series of transverse minute grooves of progressively varying spacing along a concave surface enables use of such gratings for X-ray or longer wavelength imaging of objects. The variable groove spacing establishes aplanatism or substantially uniform magnification across the optical aperture. The grating may be used, for example, in X-ray microscopes or telescopes of the imaging type and in X-ray microprobes. Increased spatial resolution and field of view may be realized in X-ray imaging.

  15. Large size metallic glass gratings by embossing

    NASA Astrophysics Data System (ADS)

    Ma, J.; Yi, J.; Zhao, D. Q.; Pan, M. X.; Wang, W. H.

    2012-09-01

    Bulk metallic glasses have excellent thermoforming ability in their wide supercooled liquid region. We show that large-size metallic glass grating (˜8 × 8 mm2) with fine periodicity and ultra smooth surface feature can be readily fabricated by hot embossing. The method for fabrication of gratings is proved to be much cheaper, and requires low pressure and short time (less than 30 s). The metallic glass gratings exhibit comparable optical properties such as rainbow-like spectrum when shone by fluorescent lamp light.

  16. Coherence-polarization mixing in resonance gratings.

    PubMed

    Vartiainen, Ismo; Saastamoinen, Toni; Tervo, Jani; Kuittinen, Markku

    2012-02-01

    We show, using rigorous diffraction theory, that resonance gratings can be used to transfer partial spatial correlation to partial polarization even if the incident light beam is fully polarized. The phenomenon is based on the fact that either of the two orthogonal polarization components can be coupled into the leaky waveguide mode, leading to a strong phase delay, while the other one is reflected without being coupled into the grating. Numerical demonstrations are based on a Gaussian Schell-model beam and a grating analysis performed by rigorous Fourier modal method.

  17. Advanced experimental applications for x-ray transmission gratings spectroscopy using a novel grating fabrication method

    NASA Astrophysics Data System (ADS)

    Hurvitz, G.; Ehrlich, Y.; Strum, G.; Shpilman, Z.; Levy, I.; Fraenkel, M.

    2012-08-01

    A novel fabrication method for soft x-ray transmission grating and other optical elements is presented. The method uses focused-ion-beam technology to fabricate high-quality free standing grating bars on transmission electron microscopy grids. High quality transmission gratings are obtained with superb accuracy and versatility. Using these gratings and back-illuminated CCD camera, absolutely calibrated x-ray spectra can be acquired for soft x-ray source diagnostics in the 100-3000 eV spectral range. Double grating combinations of identical or different parameters are easily fabricated, allowing advanced one-shot application of transmission grating spectroscopy. These applications include spectroscopy with different spectral resolutions, bandwidths, dynamic ranges, and may serve for identification of high-order contribution, and spectral calibrations of various x-ray optical elements.

  18. Boosting phase contrast with a grating Bonse–Hart interferometer of 200 nanometre grating period

    PubMed Central

    Wen, Han; Gomella, Andrew A.; Patel, Ajay; Wolfe, Douglas E.; Lynch, Susanna K.; Xiao, Xianghui; Morgan, Nicole

    2014-01-01

    We report on a grating Bonse–Hart interferometer for phase-contrast imaging with hard X-rays. The method overcomes limitations in the level of sensitivity that can be achieved with the well-known Talbot grating interferometer, and without the stringent spectral filtering at any given incident angle imposed by the classic Bonse–Hart interferometer. The device operates in the far-field regime, where an incident beam is split by a diffraction grating into two widely separated beams, which are redirected by a second diffraction grating to merge at a third grating, where they coherently interfere. The wide separation of the interfering beams results in large phase contrast, and in some cases absolute phase images are obtained. Imaging experiments were performed using diffraction gratings of 200 nm period, at 22.5 keV and 1.5% spectral bandwidth on a bending-magnetic beamline. Novel design and fabrication process were used to achieve the small grating period. Using a slitted incident beam, we acquired absolute and differential phase images of lightly absorbing samples. An advantage of this method is that it uses only phase modulating gratings, which are easier to fabricate than absorption gratings of the same periods. PMID:24470412

  19. Boosting phase contrast with a grating Bonse-Hart interferometer of 200 nanometre grating period.

    PubMed

    Wen, Han; Gomella, Andrew A; Patel, Ajay; Wolfe, Douglas E; Lynch, Susanna K; Xiao, Xianghui; Morgan, Nicole

    2014-03-06

    We report on a grating Bonse-Hart interferometer for phase-contrast imaging with hard X-rays. The method overcomes limitations in the level of sensitivity that can be achieved with the well-known Talbot grating interferometer, and without the stringent spectral filtering at any given incident angle imposed by the classic Bonse-Hart interferometer. The device operates in the far-field regime, where an incident beam is split by a diffraction grating into two widely separated beams, which are redirected by a second diffraction grating to merge at a third grating, where they coherently interfere. The wide separation of the interfering beams results in large phase contrast, and in some cases absolute phase images are obtained. Imaging experiments were performed using diffraction gratings of 200 nm period, at 22.5 keV and 1.5% spectral bandwidth on a bending-magnetic beamline. Novel design and fabrication process were used to achieve the small grating period. Using a slitted incident beam, we acquired absolute and differential phase images of lightly absorbing samples. An advantage of this method is that it uses only phase modulating gratings, which are easier to fabricate than absorption gratings of the same periods.

  20. Liquid crystal on subwavelength metal gratings

    SciTech Connect

    Palto, S. P.; Barnik, M. I.; Artemov, V. V.; Shtykov, N. M.; Geivandov, A. R.; Yudin, S. G.; Gorkunov, M. V.

    2015-06-14

    Optical and electrooptical properties of a system consisting of subwavelength metal gratings and nematic liquid crystal layer are studied. Aluminium gratings that also act as interdigitated electrodes are produced by focused ion beam lithography. It is found that a liquid crystal layer strongly influences both the resonance and light polarization properties characteristic of the gratings. Enhanced transmittance is observed not only for the TM-polarized light in the near infrared spectral range but also for the TE-polarized light in the visible range. Although the electrodes are separated by nanosized slits, and the electric field is strongly localized near the surface, a pronounced electrooptical effect is registered. The effect is explained in terms of local reorientation of liquid crystal molecules at the grating surface and propagation of the orientational deformation from the surface into the bulk of the liquid crystal layer.

  1. Adaptable Diffraction Gratings With Wavefront Transformation

    NASA Technical Reports Server (NTRS)

    Iazikov, Dmitri; Mossberg, Thomas W.; Greiner, Christoph M.

    2010-01-01

    Diffraction gratings are optical components with regular patterns of grooves, which angularly disperse incoming light by wavelength. Traditional diffraction gratings have static planar, concave, or convex surfaces. However, if they could be made so that they can change the surface curvature at will, then they would be able to focus on particular segments, self-calibrate, or perform fine adjustments. This innovation creates a diffraction grating on a deformable surface. This surface could be bent at will, resulting in a dynamic wavefront transformation. This allows for self-calibration, compensation for aberrations, enhancing image resolution in a particular area, or performing multiple scans using different wavelengths. A dynamic grating gives scientists a new ability to explore wavefronts from a variety of viewpoints.

  2. An Electronic Analog of the Diffraction Grating.

    ERIC Educational Resources Information Center

    MacLeod, A. M.

    1978-01-01

    Gives an outline description of electronic circuitry which is analogous to the optical diffraction grating or to crystals used in the Bragg reflection of X-rays or electron waves, and explains how to use it. (Author/GA)

  3. Hydraulic Capacity of an ADA Compliant Street Drain Grate

    SciTech Connect

    Lottes, Steven A.; Bojanowski, Cezary

    2015-09-01

    Resurfacing of urban roads with concurrent repairs and replacement of sections of curb and sidewalk may require pedestrian ramps that are compliant with the American Disabilities Act (ADA), and when street drains are in close proximity to the walkway, ADA compliant street grates may also be required. The Minnesota Department of Transportation ADA Operations Unit identified a foundry with an available grate that meets ADA requirements. Argonne National Laboratory’s Transportation Research and Analysis Computing Center used full scale three dimensional computational fluid dynamics to determine the performance of the ADA compliant grate and compared it to that of a standard vane grate. Analysis of a parametric set of cases was carried out, including variation in longitudinal, gutter, and cross street slopes and the water spread from the curb. The performance of the grates was characterized by the fraction of the total volume flow approaching the grate from the upstream that was captured by the grate and diverted into the catch basin. The fraction of the total flow entering over the grate from the side and the fraction of flow directly over a grate diverted into the catch basin were also quantities of interest that aid in understanding the differences in performance of the grates. The ADA compliant grate performance lagged that of the vane grate, increasingly so as upstream Reynolds number increased. The major factor leading to the performance difference between the two grates was the fraction of flow directly over the grates that is captured by the grates.

  4. Grating enhanced solid-state laser amplifiers

    DOEpatents

    Erlandson, Alvin C.; Britten, Jerald A.

    2010-11-09

    A novel method and apparatus for suppressing ASE and parasitic oscillation modes in a high average power laser is introduced. Such an invention, as disclosed herein, uses diffraction gratings to increase gain, stored energy density, and pumping efficiency of solid-state laser gain media, such as, but not limited to rods, disks and slabs. By coupling predetermined gratings to solid-state gain media, such as crystal or ceramic laser gain media, ASE and parasitic oscillation modes can be effectively suppressed.

  5. Multiple scattering by deep perturbed gratings

    SciTech Connect

    Knotts, M.E.; O`Donnell, K.A.

    1994-11-01

    We present measurements of the far-field scattered intensity for gratings consisting of uniform, regularly spaced, wavelength-scale grooves that have randomly fluctuating depths. The complete polarization dependence of the scattering is determined, and particular attention is given to measurements that isolate multiple scattering. For both perturbed and unperturbed gratings, effects similar to backscattering enhancement seen for randomly rough surfaces are observed, and these effects are linked to the coherent interference of reciprocal pairs of waves multiply scattered within the grooves.

  6. Spatial heterodyne interferometry with polarization gratings.

    PubMed

    Kudenov, Michael W; Miskiewicz, Matthew N; Escuti, Michael J; Dereniak, Eustace L

    2012-11-01

    The implementation of a polarization-based spatial heterodyne interferometer (SHI) is described. While a conventional SHI uses a Michelson interferometer and diffraction gratings, our SHI exploits mechanically robust Wollaston prisms and polarization gratings. A theoretical model for the polarization SHI is provided and validated with data from our proof of concept experiments. This device is expected to provide a compact monolithic sensor for subangstrom resolution spectroscopy in remote sensing, biomedical imaging, and machine vision applications.

  7. Resonant grating biosensor platform design and fabrication

    NASA Astrophysics Data System (ADS)

    Brioude, Valerie; Saoudi, Rachida; Blanc, Daniele; Reynaud, Stephanie; Tonchev, Svetlen; Lyndin, Nikolai M.; Molloy, James

    2004-02-01

    Grating coupled evanescent wave slab waveguide biosensors are now well established about twenty years after they were demonstrated. They usually rely upon mode excitation from the substrate side, providing a means to measure the bioreaction at the waveguide surface through the monitoring of the conditions of mode excitation. A new readout principle will be presented whereby the incident beam undergoes a sharp and high reflection while being trapped into the biomaterial loaded grating waveguide. The high index metal oxide waveguide and the grating are designed so that the evanescent wave sensitivity is maximum and the conditions for resonant reflection are fulfilled for both polarizations close to normal incidence. Under these conditions, the grating corrugation cannot be located on both sides of the waveguide, as usually preferred, since the grating strength of the TM polarization would be too low. The corrugation must therefore be at the analyte side of the metal oxide layer ; this calls for a specific grating fabrication technology. The option retained for low cost manufacturing is that of wet etching of Ta2O5. This is quite a challenging problem since there is no wet etchant of high density Ta2O5 which does not dissolve standard photoresist, and since the isotropy of wet etching is likely to smooth out the required short period corrugation by underetching. This paper describes the rationale of the design of the reflection interrogation scheme and brings the experimental evidence of the effect obtained on wet etched sensor platforms.

  8. Electro-optic Phase Grating Streak Spectrometer

    SciTech Connect

    Goldin, F. J.

    2012-08-02

    The electro-optic phase grating streak spectrometer (EOPGSS) generates a time-resolved spectra equivalent to that obtained with a conventional spectrometer/streak camera combination, but without using a streak camera (by far the more expensive and problematic component of the conventional system). The EOPGSS is based on a phase, rather than an amplitude grating. Further, this grating is fabricated of electro-optic material such as, for example, KD*P, by either etching grooves into an E-O slab, or by depositing lines of the E-O material onto an optical flat. An electric field normal to the grating alters the material’s index of refraction and thus affects a shift (in angle) of the output spectrum. Ramping the voltage streaks the spectrum correspondingly. The streak and dispersion directions are the same, so a second (static, conventional) grating disperses the spectrum in the orthogonal direction to prevent different wavelengths from “overwriting” each other. Because the streaking is done by the grating, the streaked output spectrum is recorded with a time-integrating device, such as a CCD. System model, typical design, and performance expectations will be presented.

  9. Polarization insensitive imaging through polarization gratings.

    PubMed

    Nersisyan, Sarik R; Tabiryan, Nelson V; Hoke, Landa; Steeves, Diane M; Kimball, Brian R

    2009-02-02

    Liquid crystal polarization gratings exhibit high diffraction efficiency (approximately 100%) in thin material layers comparable to the radiation wavelength. We demonstrate that they can be combined for polarization-insensitive imaging and optical switching applications. A pair of closely spaced, parallel oriented, cycloidal polarization gratings is capable of canceling the diffractive property of an individual grating. As a result, the phase of the beam is not distorted, and holographic images can be formed through them. An anti-parallel arrangement results in a broader effective diffraction band and doubles the diffraction angle. Broadband diffraction spanning from 480 nm to beyond 900 nm wavelengths has been obtained for a pair of gratings with 500 nm and 633 nm peak diffraction wavelengths. Liquid crystal polymer cycloidal gratings were used in the study showing 98% diffraction efficiency over a large area, and allowed for the use of laser beams expanded to 25 mm. The characteristics of combined cycloidal gratings were tested with laser beams at both UV and red wavelengths.

  10. Dynamic optical coupled system employing Dammann gratings

    NASA Astrophysics Data System (ADS)

    Di, Caihui; Zhou, Changhe; Ru, Huayi

    2004-10-01

    With the increasing of the number of users in optical fiber communications, fiber-to-home project has a larger market value. Then the need of dynamic optical couplers, especially of N broad-band couplers, becomes greater. Though some advanced fiber fusion techniques have been developed, they still have many shortcomings. In this paper we propose a dynamic optical coupled system employing even-numbered Dammann gratings, which have the characteristic that the phase distribution in the first half-period accurately equals to that in the second-period with π phase inversion. In our experiment, we divide a conventional even-numbered Dammann grating into two identical gratings. The system can achieve the beam splitter and combiner as the switch between them according to the relative shift between two complementary gratings. When there is no shift between the gratings, the demonstrated 1×8 dynamic optical coupler achieves good uniformity of 0.06 and insertion loss of around 10.8 dB for each channel as a splitter. When the two gratings have an accurate shift of a half-period between them, our system has a low insertion loss of 0.46 dB as a combiner at a wavelength of 1550 nm.

  11. Convex Diffraction Grating Imaging Spectrometer

    NASA Technical Reports Server (NTRS)

    Chrisp, Michael P. (Inventor)

    1999-01-01

    A 1:1 Offner mirror system for imaging off-axis objects is modified by replacing a concave spherical primary mirror that is concentric with a convex secondary mirror with two concave spherical mirrors M1 and M2 of the same or different radii positioned with their respective distances d1 and d2 from a concentric convex spherical diffraction grating having its grooves parallel to the entrance slit of the spectrometer which replaces the convex secondary mirror. By adjusting their distances d1 and d2 and their respective angles of reflection alpha and beta, defined as the respective angles between their incident and reflected rays, all aberrations are corrected without the need to increase the spectrometer size for a given entrance slit size to reduce astigmatism, thus allowing the imaging spectrometer volume to be less for a given application than would be possible with conventional imaging spectrometers and still give excellent spatial and spectral imaging of the slit image spectra over the focal plane.

  12. Visibility simulation of realistic grating interferometers including grating geometries and energy spectra.

    PubMed

    Harti, Ralph P; Kottler, Christian; Valsecchi, Jacopo; Jefimovs, Konstantins; Kagias, Matias; Strobl, Markus; Grünzweig, Christian

    2017-01-23

    The performance of X-ray and neutron grating interferometers is characterised by their visibility, which is a measure for the maximum achievable contrast. In this study we show how the real grating geometry in a grating interferometer with three gratings impacts the interference and self projection that leads to visibility in the first place. We quantify the individual contributions of wavelength distributions and grating shapes in terms of visibility reduction by determining the absolute as well as relative effect of each contribution. The understanding of the impact of changed geometry and wavelength distributions on the interference of neutrons/X-rays allows us to present the first fully quantitative model of a grating interferometer setup. We demonstrate the capability of the simulation framework by building a model of the neutron grating interferometer at the ICON beamline and directly comparing simulated and measured visibility values. The general nature of the model makes it possible to extend it to any given grating interferometer for both X-rays and neutrons.

  13. A novel single-order diffraction grating: Random position rectangle grating

    NASA Astrophysics Data System (ADS)

    Zuhua, Yang; Qiangqiang, Zhang; Jing, Wang; Quanping, Fan; Yuwei, Liu; Lai, Wei; Leifeng, Cao

    2016-05-01

    Spectral diagnosis of radiation from laser plasma interaction and monochromation of radiation source are hot and important topics recently. Grating is one of the primary optical elements to do this job. Although easy to fabricate, traditional diffraction grating suffers from multi-order diffraction contamination. On the other hand, sinusoidal amplitude grating has the nonharmonic diffraction property, but it is too difficult to fabricate, especially for x-ray application. A novel nonharmonic diffraction grating named random position rectangle grating (RPRG) is proposed in this paper. Theoretical analysis and experiment results show that the RPRG is both higher order diffraction suppressing and not difficult to fabricate. Additionally, it is highly efficient; its first order absolute theoretical diffraction efficiency reaches 4.1%. Our result shows that RPRG is a novel tool for radiation diagnosis and monochromation. Project supported by the National Natural Science Foundation of China (Grant No. 11375160) and the National Science Instruments Major Project of China (Grant No. 2012YQ130125).

  14. Case study of grate-chain degradation in a Grate-Kiln process

    NASA Astrophysics Data System (ADS)

    Nilsson, Erik A. A.; Pettersson, L.; Antti, M.-L.

    2013-12-01

    Austenitic stainless steels are often used in high temperature applications due to their resistance to corrosion. Grate-Kiln processes that sinter iron ore pellets use grate-chains which are made of austenitic stainless steel to withstand the severe environment. It has been shown, however, that the grate-chain is affected by several degrading mechanisms in the harsh environment of the sintering process. A grate-chain that has been in service for 8 months was investigated in order to find the mechanisms of degradation. Results show that slag products are accumulated on the grate-chain and interact with the steel as hot corrosion. The stainless steel is believed to be sensitized against inter-granular attack by carburization followed by inter-granular attack. The resistance towards degradation seems to decrease with time which is suggested to be caused by depletion of chromium.

  15. Trends and future of fiber Bragg grating sensing technologies: tailored draw tower gratings (DTGs)

    NASA Astrophysics Data System (ADS)

    Lindner, E.; Hartung, A.; Hoh, D.; Chojetzki, C.; Schuster, K.; Bierlich, J.; Rothhardt, M.

    2014-05-01

    Today fiber Bragg gratings are commonly used in sensing technology as well as in telecommunications. Numerous requirements must be satisfied for their application as a sensor such as the number of sensors per system, the measurement resolution and repeatability, the sensor reusability as well as the sensor costs. In addition current challenges need to be met in the near future for sensing fibers to keep and extend their marketability such as the suitability for sterilization, hydrogen darkening or the separation of strain and temperature (or pressure and temperature). In this contribution we will give an outlook about trends and future of the fiber Bragg gratings in sensing technologies. Specifically, we will discuss how the use of draw tower grating technology enables the production of tailored Bragg grating sensing fibers, and we will present a method of separating strain and temperature by the use of a single Bragg grating only, avoiding the need for additional sensors to realize the commonly applied temperature compensation.

  16. A census of quasar-intrinsic absorption in the Hubble Space Telescope archive: systems from high-resolution echelle spectra

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Lynch, Ryan S.; Charlton, Jane C.; Eracleous, Michael; Tripp, Todd M.; Palma, Christopher; Sembach, Kenneth R.; Misawa, Toru; Masiero, Joseph R.; Milutinovic, Nikola; Lackey, Benjamin D.; Jones, Therese M.

    2013-10-01

    We present a census of zabs ≲ 2 intrinsic (those showing partial coverage) and associated (zabs ˜ zem) quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. survey of 2 < zem < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called strong N V intrinsic systems (where the equivalent width of H I Lyα is small compared to N V λ1238) presented in that work, but find no convincing cases of `strong C IV' intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of `strong O VI' systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is an ˜3σ excess in the number of absorbers near the quasar redshift (|Δv| ≤ 5000 km s-1) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disc of the quasar.

  17. Variability of D and H in the Martian upper atmosphere observed with the MAVEN IUVS echelle channel

    NASA Astrophysics Data System (ADS)

    Clarke, J. T.; Mayyasi, M.; Bhattacharyya, D.; Schneider, N. M.; McClintock, W. E.; Deighan, J. I.; Stewart, A. I. F.; Chaufray, J.-Y.; Chaffin, M. S.; Jain, S. K.; Stiepen, A.; Crismani, M.; Holsclaw, G. M.; Montmessin, F.; Jakosky, B. M.

    2017-02-01

    The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions, which are produced by resonant scattering of solar emission, over the course of most of a martian year. The fundamental purpose of these measurements is to understand the physical principles underlying the escape of H and D from the upper atmosphere into space, and thereby to relate present-day measurements of an enhanced HDO/H2O ratio in the bulk atmosphere to the water escape history of Mars. Variations in these emissions independent of the solar flux reflect changes in the density and/or temperature of the species in the upper atmosphere. The MAVEN measurements show that the densities of both H and D vary by an order of magnitude over a martian year, and not always in synch with each other. This discovery has relevance to the processes by which H and D escape into space. One needs to understand the controlling factors to be able to extrapolate back in time to determine the water escape history from Mars at times when the atmosphere was thicker, when the solar flux and solar wind were stronger, etc. Further measurements will be able to identify the specific controlling factors for the large changes in H and D, which likely result in large changes in the escape fluxes of both species.

  18. Echelle spectrograph calibration with a frequency comb based on a harmonically mode-locked fiber laser: a proposal

    SciTech Connect

    McFerran, J. J.

    2009-05-10

    Details for constructing an astronomical frequency comb suitable as a wavelength reference for echelle spectrographs associated with optical telescopes are outlined. The source laser for the frequency comb is a harmonically mode-locked fiber laser with a central wavelength of 1.56 {mu}m. The means of producing a repetition rate greater than 7 GHz and a peak optical power of {approx}8 kW are discussed. Conversion of the oscillator light into the visible can occur through a two-step process of (i) nonlinear conversion in periodically poled lithium niobate and (ii) spectral broadening in photonic crystal fiber. While not necessarily octave spanning in spectral range to permit the use of an f -to- 2f interferometer for offset frequency control, the frequency comb can be granted accuracy by linking the mode spacing and a comb tooth to separate frequency references. The design avoids the use of a Fabry-Perot cavity to increase the mode spacing of the frequency comb; however, the level of supermode suppression and sideband asymmetry in the fiber oscillator and in the subsequent frequency conversion stages are aspects that need to be experimentally tested.

  19. Grating tuned unstable resonator laser cavity

    DOEpatents

    Johnson, Larry C.

    1982-01-01

    An unstable resonator to be used in high power, narrow line CO.sub.2 pump lasers comprises an array of four reflectors in a ring configuration wherein spherical and planar wavefronts are separated from each other along separate optical paths and only the planar wavefronts are impinged on a plane grating for line tuning. The reflector array comprises a concave mirror for reflecting incident spherical waves as plane waves along an output axis to form an output beam. A plane grating on the output axis is oriented to reflect a portion of the output beam off axis onto a planar relay mirror spaced apart from the output axis in proximity to the concave mirror. The relay mirror reflects plane waves from the grating to impinge on a convex expanding mirror spaced apart from the output axis in proximity to the grating. The expanding mirror reflects the incident planar waves as spherical waves to illuminate the concave mirror. Tuning is provided by rotating the plane grating about an axis normal to the output axis.

  20. Post-exposed fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Miller, Gary A.

    This thesis explains the development and characterization of a novel technique to fabricate weak fiber Bragg gratings for highly specific multi-element sensor arrays. This method, termed the "rescan technique," involves re-exposing a local region of a grating to fringeless ultraviolet light to "trim" unwanted portions of the reflection spectrum. The spectral effects that result from a rescan can only be adequately described by inventing the concept of a three-dimensional index growth surface, where induced index is a function of both the writing intensity and the exposure time. Using this information, it is possible to predict the spectral response of a rescanned grating using a numerical model. For our model, we have modified the piecewise-uniform approach to include coefficients within the coupled-mode formulism that imitate the same scattering properties as the actual grating. By taking high accuracy measurements of the refractive index change in germanosilicate fiber, we have created the necessary 3D map of photoinduced index to accurately model gratings and their post-exposure spectra. We will also demonstrate that optical fiber exhibits what we call "exposure history"; the final index change in a region depends on the previous exposures conditions.

  1. Hyperspectral grating optimization and manufacturing considerations

    NASA Astrophysics Data System (ADS)

    Ziph-Schatzberg, Leah; Swartz, Barry; Warren, Chris; Santman, Jeff; Saleh, Mohammad; Wiggins, Richard; Crifasi, Joe; Comstock, Lovell; Taylor, Kevan

    2015-06-01

    Hyperspectral imaging systems are finding broader applications in both the commercial and aerospace markets. It is becoming clear that to optimize the performance of these systems, their instrument transfer function needs to be tailored for each application. Vis-SWIR systems in the full 400nm to 2500nm waveband present particular design and manufacturing challenges. A single blazed grating is inadequate for a system operating in the full vis-SWIR wavelength range. In addition, optical materials and broad band coatings present a challenge for non-reflective systems. An understanding of the application and wavelengths of interest, combined with a judicious choice of a focal plane array, can then lead to an optimized system for the specific application. The ability to tailor the grating and manufacture a wide variety of grating profiles and substrate shapes becomes a significant performance enabler. This paper will discuss how the use of optical, coating, and grating design/analysis software, combined with grating manufacturing techniques assure meeting high performance requirements for different applications.

  2. Iridescence in Meat Caused by Surface Gratings

    PubMed Central

    Martinez-Hurtado, Juan Leonardo; Akram, Muhammad Safwan; Yetisen, Ali Kemal

    2013-01-01

    The photonic structure of cut muscle tissues reveals that the well-ordered gratings diffract light, producing iridescent colours. Cut fibrils protruding from the muscle surface create a two-dimensional periodic array, which diffract light at specific wavelengths upon illumination. However, this photonic effect misleads consumers in a negative way to relate the optical phenomenon with the quality of the product. Here we discuss the fundamentals of this optical phenomenon and demonstrate a methodology for quantitatively measuring iridescence caused by diffraction gratings of muscle tissue surface of pork (Sus scrofa domesticus) using reflection spectrophotometry. Iridescence was discussed theoretically as a light phenomenon and spectral measurements were taken from the gratings and monitored in real time during controlled drying. The findings show that the intensity of diffraction diminishes as the surface grating was dried with an air flow at 50 °C for two minutes while the diffracted light wavelength was at 585 ± 9 nm. Our findings indicate that the diffraction may be caused by a blazed surface grating. The implications of the study include providing guidelines to minimise the iridescence by altering the surface microstructure, and in consequence, removing the optical effect. PMID:28239133

  3. Grating array systems having a plurality of gratings operative in a coherently additive mode and methods for making such grating array systems

    DOEpatents

    Kessler, Terrance J.; Bunkenburg, Joachim; Huang, Hu

    2007-02-13

    A plurality of gratings (G1, G2) are arranged together with a wavefront sensor, actuators, and feedback system to align the gratings in such a manner, that they operate like a single, large, monolithic grating. Sub-wavelength-scale movements in the mechanical mounting, due to environmental influences, are monitored by an interferometer (28), and compensated by precision actuators (16, 18, 20) that maintain the coherently additive mode. The actuators define the grating plane, and are positioned in response to the wavefronts from the gratings and a reference flat, thus producing the interferogram that contains the alignment information. Movement of the actuators is also in response to a diffraction-limited spot on the CCD (36) to which light diffracted from the gratings is focused. The actuator geometry is implemented to take advantage of the compensating nature of the degrees of freedom between gratings, reducing the number of necessary control variables.

  4. Silicon nitride grating waveguide based directional coupler

    NASA Astrophysics Data System (ADS)

    Feng, Jijun; Li, Anyuan; Akimoto, Ryoichi; Zeng, Heping

    2016-10-01

    Silicon nitride is a promising wave-guiding material for integrated photonics applications with a wide transparency bandwidth from visible to mid-infrared, with a superior performance in fiber-coupling and propagation losses, more tolerant fabrication process to the structure parameters variation and compatible with the CMOS technology. Directional coupler (DC) is very popular for realizing beam splitter because of its structural simplicity and no excess loss intrinsically. Here, a conventional silicon nitride directional coupler, three-dimensional vertical coupler, and grating waveguide assisted coupler are designed and fabricated, and compared with each other. A grating waveguide based coupler with a period of 300 nm and coupling length of 26 um, can realize a wideband 3-dB splitter for the wavelength in the range from 1540 to 1620 nm, for a transverse electric (TE) polarized wave. With further optimization of the grating period and duty cycle, the device performance can be further improved with a wider bandwidth.

  5. Optically tunable chirped fiber Bragg grating.

    PubMed

    Li, Zhen; Chen, Zhe; Hsiao, V K S; Tang, Jie-Yuan; Zhao, Fuli; Jiang, Shao-Ji

    2012-05-07

    This work presents an optically tunable chirped fiber Bragg grating (CFBG). The CFBG is obtained by a side-polished fiber Bragg grating (SPFBG) whose thickness of the residual cladding layer in the polished area (D(RC)) varies with position along the length of the grating, which is coated with a photoresponsive liquid crystal (LC) overlay. The reflection spectrum of the CFBG is tuned by refractive index (RI) modulation, which comes from the phase transition of the overlaid photoresponsive LC under ultraviolet (UV) light irradiation. The broadening in the reflection spectrum and corresponding shift in the central wavelength are observed with UV light irradiation density of 0.64mW/mm. During the phase transition of the photoresponsive LC, the RI increase of the overlaid LC leads to the change of the CFBG reflection spectrum and the change is reversible and repeatable. The optically tunable CFBGs have potential use in optical DWDM system and an all-fiber telecommunication system.

  6. Spatial filtering by using cascading plasmonic gratings.

    PubMed

    Wang, Chih-Ming; Chang, Yia-Chung; Tsai, Din Ping

    2009-04-13

    In this study, the optical properties of a plasmonic multilayer structure, consisting of two longitudinally cascaded gratings with a half pitch off-set, are investigated. The proposed structure, which is a system mixing extended and localized surface plasmon, forms transversely cascaded metal/insulator/metal cavities. The angle dependent reflection spectrum of the proposed structure displays a resonance peak at a specific angle. The full-width at half maximum (FWHM) of the resonant peak is smaller than 3 degrees. The angular dispersion of the cascading plasmonic gratings is about d theta/d lambda =0.15 degrees/nm. The cascading plasmonic gratings can be used as a spatial filter to improve the spatial coherence of a light source.

  7. Development of Aspherical Active Gratings at NSRRC

    SciTech Connect

    Tseng, T.-C.; Wang, D.-J.; Perng, S.-Y.; Chen, C.-T.; Lin, C.-J.; Kuan, C.-K.; Ho, H.-C.; Wang, J.; Fung, H.S.; Chang, S.-H.

    2007-01-19

    An active grating based on a novel optical concept with bendable polynomial surface profile to reduce the coma and defocus aberrations had been designed and proved by the prototype testing. Due to the low glass transition temperature of the glue and the difference of thermal expansion coefficient between the 17-4 steel bender and silicon, the prototype distorted from flat polished condition when thermally de-blocked the polishing pitch. To improve the thermal deformation of the active grating in the polishing process, a new invar bender and high curing temperature glue were adapted to glue a silicon substrate on the bender. After some tests and manufacturer polishing, it showed acceptable conditions. In this paper we will present the design and preliminary tests of the invar active grating. Meanwhile, the design and analysis of a new 17-4 PH steel bender to be electro-less nickel plating and mechanical ruling for a new beamline will also be discussed.

  8. Ultra-high density diffraction grating

    DOEpatents

    Padmore, Howard A.; Voronov, Dmytro L.; Cambie, Rossana; Yashchuk, Valeriy V.; Gullikson, Eric M.

    2012-12-11

    A diffraction grating structure having ultra-high density of grooves comprises an echellette substrate having periodically repeating recessed features, and a multi-layer stack of materials disposed on the echellette substrate. The surface of the diffraction grating is planarized, such that layers of the multi-layer stack form a plurality of lines disposed on the planarized surface of the structure in a periodical fashion, wherein lines having a first property alternate with lines having a dissimilar property on the surface of the substrate. For example, in one embodiment, lines comprising high-Z and low-Z materials alternate on the planarized surface providing a structure that is suitable as a diffraction grating for EUV and soft X-rays. In some embodiments, line density of between about 10,000 lines/mm to about 100,000 lines/mm is provided.

  9. Curved grating fabrication techniques for concentric-circle grating, surface-emitting semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Jordan, Rebecca H.; King, Oliver; Wicks, Gary W.; Hall, Dennis G.; Anderson, Erik H.; Rooks, Michael J.

    1993-01-01

    We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a concentric-circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each concentric-circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, concentric-circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.

  10. Strongly Dispersive Transient Bragg Grating for High Harmonics

    SciTech Connect

    Farrell, J.; Spector, L.S.; Gaarde, M.B.; McFarland, B.K.; Bucksbaum, P.H.; Guhr, Markus; /SLAC, PULSE /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.

    2010-06-04

    We create a transient Bragg grating in a high harmonic generation medium using two counterpropagating pulses. The Bragg grating disperses the harmonics in angle and can diffract a large bandwidth with temporal resolution limited only by the source size.

  11. PASSIVE VENTILATION DETAIL (CORRESPONDS WITH METAL GRATE IN CENTER OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PASSIVE VENTILATION DETAIL (CORRESPONDS WITH METAL GRATE IN CENTER OF BATTERY STREET). LOOKING SOUTH AT GRATE IN SOUTHBOUND TUNNEL BORE. - Alaskan Way Viaduct and Battery Street Tunnel, Seattle, King County, WA

  12. Waveguide grating mirror for laser resonators

    NASA Astrophysics Data System (ADS)

    Rabady, Rabi Ibrahim

    Improved beam quality for semiconductor lasers has been a challenging problem since laser invention. The approach proposed in this thesis for beam improvement is based on zero-order anomalies in the reflectance spectra of periodically corrugated waveguides, which is the waveguide analogy of the well-known Wood anomalies in diffraction spectra of metallic gratings. The proposed investigation include developing a high-quality and reliable technologies for optical waveguides, holographic-grating, and optical resonant filters. Applications of this research include high-power and high-brightness vertical-cavity surface-emitting lasers (VCSELs), large area lasers, and laser arrays for optical communications, lidars, and industrial material processing.

  13. Coherent imaging by using defocus grating

    NASA Astrophysics Data System (ADS)

    Ma, Haotong; Xie, Zongliang; Qi, Bo; Zhang, Guowen; Ren, Ge; Wang, Sanhong

    2016-10-01

    We propose and demonstrate an coherent imaging technique by using defocus grating. For the imaging system, the defocus grating combined with lens with short focal length is used to realize multiplane imaging on the lens' focal plane, simultaneously. Based on these multiplane images, Gerchberg-Saxton (GS) algorithm is used to reconstruct the complex amplitude distribution of the input imaging beam. By using computational imaging and digital wavefront distortion correction with stochastic parallel gradient descent (SPGD) algorithm, this technology can be used for joint estimation of both pupil aberrations and an high resolution image of the object, successfully.

  14. Modified fiber Bragg grating pulse pressure sensor

    NASA Astrophysics Data System (ADS)

    Kaczmarek, Tomasz; Kaczmarek, Zdzisław

    2007-04-01

    A new fiber optic, pulse pressure sensor with a Bragg grating, in the structure of which the operating principle of the Hopkinson bar is applied, is presented in the paper. The delivery of the measured pressure to the sensor is realized by means of a measuring head with truncated cone, made of silica glass and fusion-spliced to the grating's fiber. The optical and the electronic setup of the sensor is given. The sensor was employed to measure pulse pressure generated by an electric discharge in water. The obtained measurement results and the conclusions arising from them are presented.

  15. Optically Tunable Gratings for Optical Interconnects

    DTIC Science & Technology

    1989-10-30

    OPTICALLY TUNABLE GRATINGS FOR OPTICAL INTERCONNECTS Final Report SELECTED JAN 2 31990 D ~ Submitted...such as acousto - optic or electro- optic deflectors . Using the strengths of our research program, we investigated optically tuneable gratings in...are those ~!,f~~ a~Sh~;~~L~~ d ~~9~H ~~t.:~~!-r~~~’~IU! 2 ~’h!~ ~H~~!~g:rtment of the Army position, 17. COSATI CODES 1 I. SUBJECT TERMS (Continut on

  16. Fabrication of reflection gratings by contact copying of amplitude holographic gratings on a metal surface

    NASA Astrophysics Data System (ADS)

    Madjidi-Zolbanine, Habib; Hodjat-Zadeh, A.

    1995-04-01

    This paper describes the contact copying of amplitude transmission holographic gratings. Master gratings (MG) are written in silver halide sensitized gelatine. A smooth and flat sheet is coated with a layer of negative photoresist constituted from a combination of polyvinyl alcohol, ammonium dichromate and Arabic gum, then the MG is put in contact with the metal surface and exposed by a mercury lamp. After processing with deionized water at (35 degree(s)C), a reflection grating is obtained. For a MG with 117 l/mm of spatial frequency and 10% of diffraction efficiency (DE), we have obtained a DE of 12%.

  17. Transmission grating stretcher for contrast enhancement of high power lasers.

    PubMed

    Tang, Yunxin; Hooker, Chris; Chekhlov, Oleg; Hawkes, Steve; Collier, John; Rajeev, P P

    2014-12-01

    We propose, for the first time, a transmission grating stretcher for high power lasers and demonstrate its superiority over conventional, reflective gold grating stretchers in terms of pulse temporal quality. We show that, compared to a conventional stretcher with the same stretching factor, the transmission-grating based stretcher yields more than an order of magnitude improvement in the contrast pedestal. We have also quantitatively characterized the roughness of the grating surfaces and estimated its impact on the contrast pedestal.

  18. Terahertz quantum well photodetectors with reflection-grating couplers

    SciTech Connect

    Zhang, R.; Fu, Z. L.; Gu, L. L.; Guo, X. G.; Cao, J. C.

    2014-12-08

    The design, fabrication, and characterization of terahertz (THz) quantum well photodetectors with one-dimensional reflection-grating coupler are presented. It is found that the reflection gratings could effectively couple the THz waves normally incident to the device. Compared with the 45-degree facet sample, the peak responsivity of this grating-coupled detector is enhanced by over 20%. The effects of the gratings on the photocurrent spectra are also analyzed.

  19. Laser-induced transient grating setup with continuously tunable period

    SciTech Connect

    Vega-Flick, A.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Khanolkar, A.; Abi Ghanem, M.; Boechler, N.; Alvarado-Gil, J. J.

    2015-12-15

    We present a modification of the laser-induced transient grating setup enabling continuous tuning of the transient grating period. The fine control of the period is accomplished by varying the angle of the diffraction grating used to split excitation and probe beams. The setup has been tested by measuring dispersion of bulk and surface acoustic waves in both transmission and reflection geometries. The presented modification is fully compatible with optical heterodyne detection and can be easily implemented in any transient grating setup.

  20. Fractional Talbot field and of finite gratings: compact analytical formulation.

    PubMed

    Arrizón, V; Rojo-Velázquez, G

    2001-06-01

    We present a compact analytical formulation for the fractional Talbot effect at the paraxial domain of a finite grating. Our results show that laterally shifted distorted images of the grating basic cell form the Fresnel field at a fractional Talbot plane of the grating. Our formulas give the positions of those images and show that they are given by the convolution of the nondistorted cells (modulated by a quadratic phase factor) with the Fourier transform of the finite-grating pupil.

  1. Polymeric waveguide Bragg grating filter using soft lithography

    NASA Astrophysics Data System (ADS)

    Kocabas, Askin; Aydinli, Atilla

    2006-10-01

    We use the soft lithography technique to fabricate a polymeric waveguide Bragg grating filter. Master grating structure is patterned by e-beam lithography. Using an elastomeric stamp and capillary action, uniform grating structures with very thin residual layers are transferred to the UV curable polymer without the use of an imprint machine. The waveguide layer based on BCB optical polymer is fabricated by conventional optical lithography. This approach provides processing simplicity to fabricate Bragg grating filters.

  2. First light observation of GIGMICS (germanium immersion grating mid-infrared cryogenic spectrograph) by Kanata 1.5-m Telescope at Higashi-Hiroshima Observatory

    NASA Astrophysics Data System (ADS)

    Hirahara, Yasuhiro; Aoki, Keishin; Ohta, Kanako; Shibata, Sho; Hirao, Tsuyoshi; Tatamitani, Yoshio; Ebizuka, Noboru; Kawabata, Koji S.; Yoshida, Michitoshi; Uemura, Makoto; Oosugi, Takashi; Kawaguchi, Kentaro; Fujimori, Ryuji; Ohiwa, Hiroki; Nagahiro, Hisayuki

    2012-09-01

    We have developed a germanium immersion grating mid-infrared cryogenic spectrograph (GIGMICS) designed for the Nasmyth focus stage of NAOJ Subaru 8.2-m telescope, which operates at N-band (8-13 μm) in wavelength (λ) with maximum resolving power R(≡λ/Δλ) ~ 50,000. A single crystal germanium echelle immersion grating (30 × 30 × 72 mm) for collimated beam size of 28 mmφ was fabricated by utilizing ultra precision micro-grinding method coupled with the ELID (ELectrolytic In-process Dressing) technique (Ohmori, H. 1992, Ebizuka et al. 2003, Tokoro et al. 2003). After the critical test for the application to the laboratory gas-phase IR high-resolution spectroscopy(Hirahara et al. 2010), we have conducted the "first light" astronomical observation of GIGMICS by the Kanata 1.5-m telescope at Higashi- Hiroshima Observatory from January to April, 2011. Toward many astronomical objects such as the Moon, Venus, Jupiter, circumstellar envelopes of late-type stars, proto-planetary nebulae, and interstellar molecular clouds in the vicinity of star-forming regions, we conducted spectroscopic observations in the N-band region.

  3. Theoretical analysis of subwavelength high contrast grating reflectors.

    PubMed

    Karagodsky, Vadim; Sedgwick, Forrest G; Chang-Hasnain, Connie J

    2010-08-02

    A simple analytic analysis of the ultra-high reflectivity feature of subwavelength dielectric gratings is developed. The phenomenon of ultra high reflectivity is explained to be a destructive interference effect between the two grating modes. Based on this phenomenon, a design algorithm for broadband grating mirrors is suggested.

  4. 75 FR 41889 - Certain Steel Grating From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-19

    ... COMMISSION Certain Steel Grating From China Determination On the basis of the record \\1\\ developed in the... steel grating from China, provided for in subheading 7308.90.70 of the Harmonized Tariff Schedule of the... imports of certain steel gratings from China were being subsidized within the meaning of section 703(b)...

  5. 75 FR 8746 - Certain Steel Grating From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-25

    ... COMMISSION Certain Steel Grating From China AGENCY: United States International Trade Commission. ACTION... retarded, by reason of subsidized and less-than-fair-value imports from China of certain steel gratings... ``certain steel grating, consisting of two or more pieces of steel, including load- bearing pieces and...

  6. Deep-etched sinusoidal polarizing beam splitter grating.

    PubMed

    Feng, Jijun; Zhou, Changhe; Cao, Hongchao; Lv, Peng

    2010-04-01

    A sinusoidal-shaped fused-silica grating as a highly efficient polarizing beam splitter (PBS) is investigated based on the simplified modal method. The grating structure depends mainly on the ratio of groove depth to grating period and the ratio of incident wavelength to grating period. These ratios can be used as a guideline for the grating design at different wavelengths. A sinusoidal-groove PBS grating is designed at a wavelength of 1310 nm under Littrow mounting, and the transmitted TM and TE polarized waves are mainly diffracted into the zeroth order and the -1st order, respectively. The grating profile is optimized by using rigorous coupled-wave analysis. The designed PBS grating is highly efficient (>95.98%) over the O-band wavelength range (1260-1360 nm) for both TE and TM polarizations. The sinusoidal grating can exhibit higher diffraction efficiency, larger extinction ratio, and less reflection loss than the rectangular-groove PBS grating. By applying wet etching technology on the rectangular grating, which was manufactured by holographic recording and inductively coupled plasma etching technology, the sinusoidal grating can be approximately fabricated. Experimental results are in agreement with theoretical values.

  7. [Intercross cascaded dual-layer resonant sub-wavelength gratings].

    PubMed

    Chen, Yong-li; Zhao, Da-zun

    2009-04-01

    A security grating structure, intercross cascaded dual-layer resonant sub-wavelength grating structure, is presented. It can broaden the resonant wavelength width of resonant sub-wavelength gratings and obtain the better optical variable effect. The full-width-at half-maximum (FWHM) broadening mechanism of security grating structures is analyzed. The FWHM is dependent on the energy coupled into the grating waveguide layer. The grating structure parameters are optimized and designed. The resonance performance and grating fabrication tolerances are also studied numerically using the vector diffraction theory (the rigorous coupled wave theory). Simulation results indicate that the value of the spectral resonant peak for the security grating structure is not decreased as the incident angle increases or decreases and the maximum FWHM of different depth of grating grooves is about seven times that of the basic resonant grating structure. The resonant dual grating waveguide structure is a kind of security grating configuration with the potential to achieve higher industry application value and its resonance performance is not sensitive to manufacture errors.

  8. High Resolution Echelle Spectroscopy of Low Redshift Intervening O VI Absorbers with the Space Telescope Imaging Spectrograph

    NASA Astrophysics Data System (ADS)

    Tripp, T. M.; Bowen, D. V.; Jenkins, E. B.; Savage, B. D.

    1999-12-01

    We present high resolution FUV echelle spectroscopy of several low z intervening O VI absorbers (z < 0.3) in the spectra of H1821+643 and PG0953+415. The data were obtained with the Space Telescope Imaging Spectrograph at a resolution of 45,000 (7 km/s FWHM). We also present selected new measurements of galaxy redshifts in the 10' field centered on H1821+643. The observations provide several clues about the nature of these absorbers: (1) In the case of the strong O VI system at z = 0.2250 in the spectrum of H1821+643, we detect multicomponent Si II and Si III absorption as well as O VI and several Lyman series lines of H I. Multiple components are evident in the O VI profiles, but the components have different velocities than the Si III and Si II lines. Furthermore, the Si II and Si III lines are quite narrow, and the O VI lines are broader and spread over a larger velocity range. This evidence strongly indicates that this is a multiphase absorber. (2) We also detect `high velocity' O VI in the z = 0.2250 system. High velocity H I is also seen in the Lyα profile, but substantially offset in velocity from the O VI. This high velocity O VI may be analogous to the highly ionized high velocity clouds seen near the Milky Way. (3) We also present systems at other redshifts including very weak O VI absorption lines accompanied by weak and narrow H I absorption. (4) In all cases, several galaxies are close to the sight lines at the redshift of the O VI systems. We examine whether the O VI absorption can be attributed to the ISM of a single galaxy or the intragroup medium.

  9. The GMT-Consortium Large Earth Finder (G-CLEF): an optical Echelle spectrograph for the Giant Magellan Telescope (GMT)

    NASA Astrophysics Data System (ADS)

    Szentgyorgyi, Andrew; Baldwin, Daniel; Barnes, Stuart; Bean, Jacob; Ben-Ami, Sagi; Brennan, Patricia; Budynkiewicz, Jamie; Chun, Moo-Young; Conroy, Charlie; Crane, Jeffrey D.; Epps, Harland; Evans, Ian; Evans, Janet; Foster, Jeff; Frebel, Anna; Gauron, Thomas; Guzmán, Dani; Hare, Tyson; Jang, Bi-Ho; Jang, Jeong-Gyun; Jordan, Andres; Kim, Jihun; Kim, Kang-Miin; Mendes de Oliveira, Claudia Mendes; Lopez-Morales, Mercedes; McCracken, Kenneth; McMuldroch, Stuart; Miller, Joseph; Mueller, Mark; Oh, Jae Sok; Onyuksel, Cem; Ordway, Mark; Park, Byeong-Gon; Park, Chan; Park, Sung-Joon; Paxson, Charles; Phillips, David; Plummer, David; Podgorski, William; Seifahrt, Andreas; Stark, Daniel; Steiner, Joao; Uomoto, Alan; Walsworth, Ronald; Yu, Young-Sam

    2016-08-01

    The GMT-Consortium Large Earth Finder (G-CLEF) will be a cross-dispersed, optical band echelle spectrograph to be delivered as the first light scientific instrument for the Giant Magellan Telescope (GMT) in 2022. G-CLEF is vacuum enclosed and fiber-fed to enable precision radial velocity (PRV) measurements, especially for the detection and characterization of low-mass exoplanets orbiting solar-type stars. The passband of G-CLEF is broad, extending from 3500Å to 9500Å. This passband provides good sensitivity at blue wavelengths for stellar abundance studies and deep red response for observations of high-redshift phenomena. The design of G-CLEF incorporates several novel technical innovations. We give an overview of the innovative features of the current design. G-CLEF will be the first PRV spectrograph to have a composite optical bench so as to exploit that material's extremely low coefficient of thermal expansion, high in-plane thermal conductivity and high stiffness-to-mass ratio. The spectrograph camera subsystem is divided into a red and a blue channel, split by a dichroic, so there are two independent refractive spectrograph cameras. The control system software is being developed in model-driven software context that has been adopted globally by the GMT. G-CLEF has been conceived and designed within a strict systems engineering framework. As a part of this process, we have developed a analytical toolset to assess the predicted performance of G-CLEF as it has evolved through design phases.

  10. Four-wave mixing using polarization grating induced thermal grating in liquids exhibiting circular dichroism

    SciTech Connect

    Nunes, J.A.; Tong, W.G.; Chandler, D.W.; Rahn, L.A.

    1995-04-01

    A novel four-wave mixing technique for the detection of circular dichroism in optically active liquid samples is demonstrated. When two cross-polarized laser beams are crossed at a small angle in a circular dichroic liquid a weak thermal grating is produced with a phase depending on the sign of the circular dichroism. The authors show that the polarization of one of the beams can be modified to allow coherent interference with an intensity-grating induced thermal grating. A probe beam scattering from the composite grating results in a signal that reveals the sign and magnitude of the circular dichroism. The use of this technique to optimize the signal-to-noise ratio in the presence of scattered light and laser intensity noise is discussed.

  11. Focusing single-order diffraction transmission grating with a focusing plane perpendicular to the grating surface.

    PubMed

    Fan, Quanping; Liu, Yuwei; Yang, Zuhua; Wei, Lai; Zhang, Qiangqiang; Chen, Yong; Hu, Feng; Wang, Chuanke; Gu, Yuqiu; Zhou, Weimin; Jiang, Gang; Cao, Leifeng

    2015-06-15

    By combining the single-order dispersion properties of quasi-sinusoidal single-order diffraction transmission gratings (QSTG) and the single-foci focusing properties of annulus-sector-shaped-element binary Gabor zone plate (ASZP), we propose a novel focusing single-order diffraction transmission grating (FSDTG). Different from the diffraction patterns of a normal transmission grating (TG), it has a focusing plane perpendicular to the grating surface. Numerical simulations are carried out to verify its diffraction patterns in the framework of Fresnel-Kirchhoff diffraction. Higher-order diffraction components of higher harmonics can be effectively suppressed by the FSDTG we designed. And we find that the focal depth and resolving power are only determined by the structure parameters of our FSDTG by theoretical estimations.

  12. VINROUGE: a very compact 2-5μm high-resolution spectrograph with germanium immersion grating

    NASA Astrophysics Data System (ADS)

    Arasaki, Takayuki; Kobayashi, Naoto; Ikeda, Yuji; Kondo, Shohei; Sarugaku, Yuki; Kaji, Sayumi; Kawakita, Hideyo

    2016-08-01

    The infrared high-resolution and highly-sensitive spectroscopy can provide new and deep insights in many fields of astronomy. The 2.0-5.5 μm region is a very unique and important wavelength region for astrochemistry and astrobiology, because the vibrational transitions of C-H, N-H, O-H, C-O, and C-N bonds in many molecules, which are of astrophysical interest, concentrate in this wavelength range. To advance the study in this wavelength range, we are developing a new near-infrared spectrograph: VINROUGE (= Very-compact INfrared high-ResOlUtion Ge-immersion Echelle spectrograph). The instrumental concepts of VINROUGE are "high-resolution", "highly-sensitive", and "very-compact instrumentation". With (i) Germanium immersion grating, (ii) white pupil spectrograph design, (iii) reflective optics using the integrated off-axis mirrors and the optical bench by ceramic (cordierite CO-220), and (iv) highly-sensitive array (HAWAII-2RG 5.3μm cutoff array), we could obtain a solution of optical design with a spectral resolution of 80,000, total throughput of > 0.28, and a compact volume that is smaller than 600 mm×600 mm×600 mm even for 10-m class telescope. We have already completed the development of Germanium immersion grating. In this year, we plan to fabricate a set of integrated off-axis ceramic mirrors together with the ceramic optical bench to demonstrate that the reflective optics was an athermal performance. The first light of VINROUGE is expected in 2019.

  13. Undergraduate Experiment with Fractal Diffraction Gratings

    ERIC Educational Resources Information Center

    Monsoriu, Juan A.; Furlan, Walter D.; Pons, Amparo; Barreiro, Juan C.; Gimenez, Marcos H.

    2011-01-01

    We present a simple diffraction experiment with fractal gratings based on the triadic Cantor set. Diffraction by fractals is proposed as a motivating strategy for students of optics in the potential applications of optical processing. Fraunhofer diffraction patterns are obtained using standard equipment present in most undergraduate physics…

  14. High efficiency germanium-assisted grating coupler.

    PubMed

    Yang, Shuyu; Zhang, Yi; Baehr-Jones, Tom; Hochberg, Michael

    2014-12-15

    We propose a fiber to submicron silicon waveguide vertical coupler utilizing germanium-on-silicon gratings. The germanium is epitaxially grown on silicon in the same step for building photodetectors. Coupling efficiency based on FDTD simulation is 76% at 1.55 µm and the optical 1dB bandwidth is 40 nm.

  15. Hybrid grating reflectors: Origin of ultrabroad stopband

    NASA Astrophysics Data System (ADS)

    Park, Gyeong Cheol; Taghizadeh, Alireza; Chung, Il-Sug

    2016-04-01

    Hybrid grating (HG) reflectors with a high-refractive-index cap layer added onto a high contrast grating (HCG) provide a high reflectance close to 100% over a broader wavelength range than HCGs. The combination of a cap layer and a grating layer brings a strong Fabry-Perot (FP) resonance as well as a weak guided mode (GM) resonance. Most of the reflected power results from the FP resonance, while the GM resonance plays a key role in achieving a reflectance close to 100% as well as broadening the stopband. An HG sample with 7 InGaAlAs quantum wells included in the cap layer has been fabricated by directly wafer-bonding a III-V cap layer onto a Si grating layer. Its reflection property has been characterized. This heterogeneously integrated HG reflector may allow for a hybrid III-V on Si laser to be thermally efficient, which has promising prospects for silicon photonics light sources and high-speed operation.

  16. Diffraction from a liquid crystal phase grating.

    PubMed

    Kashnow, R A; Bigelow, J E

    1973-10-01

    The diffraction of light by a sinusoidal perturbation of the optic axis in a nematic liquid crystal is discussed. This corresponds to experiments at the electrohydrodynamic instability thresholds. An interesting qualitative feature appears: The diffraction pattern exhibits a contribution at half of the expected spatial frequency, corresponding to nonorthogonal traversals of the thick phase grating.

  17. Holographic reflection gratings in photopolymerizable solgel materials.

    PubMed

    Murciano, A; Blaya, S; Carretero, L; Madrigal, R F; Fimia, A

    2006-08-01

    The recording of holographic reflection gratings with a spatial frequency higher than 5400 lines/mm in photopolymerizable solgel materials is experimentally demonstrated. Diffraction efficiencies near 60% and a FWHM of 2.5 nm centered at 531.5 nm are achieved. Moreover, the effect of the energetic exposure is characterized at different recording intensities.

  18. Optical properties of actively controlled reflection and transmission gratings

    NASA Astrophysics Data System (ADS)

    Rodriguez, Miguel Angel

    2001-05-01

    Reflection and transmission gratings have found a wide variety of applications as optical filters and beam steering elements. In this work we have studied the optical properties of reflection and transmission gratings whose diffraction properties could be actively controlled. Two different material systems were utilized for the study. Reflection gratings in optical fibers were used and reflection and transmission gratings were fabricated holographically in a polymer dispersed liquid crystal (PDLC) material. The optical properties of refractive index-shifted gratings were studied using the fiber Bragg gratings. It was found that narrow, high transmission spikes developed inside a high reflectivity stopgap when the refractive index of a section of the grating is shifted. The refractive index-shift was achieved using the thermo- optic effect. Experimental as well as theoretical results are presented and discussed. The optical properties of electrically switchable reflection and transmission gratings fabricated in polymer dispersed liquid crystal materials were also studied. The PDLC material is electro-optic and therefore by applying an external electric field to the gratings the diffraction properties are modified. Gratings were fabricated holographically. From the study of the transmission properties of the reflection gratings we found that the reflection of the structures can be switched off by applying an external electric field and that the reflectivity is polarization insensitive for normal incidence. We also studied the diffraction properties of PDLC transmission gratings. In our analysis of the diffraction properties of these electrically- switchable liquid crystal gratings we found that it was necessary to use a generalized two-wave coupled mode theory that includes the effects of the optical anisotropy of the liquid crystal. We found that the morphology of the PDLC gratings depends on the specific PDLC mixture used to fabricate the grating.

  19. Optical tests of the Si immersed grating demonstrator for METIS

    NASA Astrophysics Data System (ADS)

    Agócs, Tibor; Navarro, Ramon; Venema, Lars; van Amerongen, Aaldert H.; Hoogeveen, Ruud W. M.; Coppens, Tonny; Nieuwland, Govert; Rodenhuis, Michiel; Brandl, Bernhard R.; Vink, Ramon

    2016-07-01

    Immersed gratings offer several advantages over conventional gratings: more compact spectrograph designs, and by using standard semiconductor industry techniques, higher diffraction-efficiency and lower stray-light can be achieved. We present the optical tests of the silicon immersed grating demonstrator for the Mid-infrared E-ELT Imager and Spectrograph, METIS. We detail the interferometric tests that were done to measure the wavefront-error and present the results of the throughput and stray-light measurements. We also elaborate on the challenges encountered and lessons learnt during the immersed grating demonstrator test campaign that helped us to improve the fabrication processes of the grating patterning on the wafer.

  20. Quenched Optical Transmission in Ultrathin Subwavelength Plasmonic Gratings

    DTIC Science & Technology

    2011-01-01

    PHYSICAL REVIEW B 83, 035426 (2011) Λ =a + b d 0k E ϑ x z HH = y -100 -80 -60 -40 -20 0 20 0.25 0.50 0.75 1.00 1.25 1.50 λ (μm) εr εi (a) (b) a Grating b...FIG. 1. (Color online) (a) Metallic grating made of silver with grating thickness d , slit aperture a, and grating period = a + b where b is the length...which the magnetic field H is polarized. The input grating surface is located at z = 0 and the output surface at z = d . (b) Real (εr ) and imaginary (εi

  1. Silicon photonic devices based on binary blazed gratings

    NASA Astrophysics Data System (ADS)

    Zhou, Zhiping; Yu, Li

    2013-09-01

    Optical technology is poised to revolutionize short-reach communication systems, and the leading technology is silicon photonics. Silicon photonic devices have attracted more and more attention and have been increasingly studied in recent years. Grating, which functions as a building block for many passive and active devices, is widely used in silicon photonics. This review presents some silicon photonic devices based on binary blazed gratings, such as grating couplers, beam splitters, polarization beam splitters, broadband reflectors, and narrow filters, that demonstrate much better performance than those based on uniform gratings, owing to the novel characteristics of binary blazed gratings.

  2. Metrology measurements for large-aperture VPH gratings

    NASA Astrophysics Data System (ADS)

    Zheng, Jessica R.; Gers, Luke; Heijmans, Jeroen

    2013-09-01

    The High Efficiency and Resolution Multi Element Spectrograph (HERMES) for the Australian Astronomical Observatory (AAO) uses four large aperture, high angle of incidence volume phase holographic gratings (VPHG) for high resolution `Galactic archaeology' spectroscopy. The large clear aperture, the high diffraction efficiency, the line frequency homogeneity, and mosaic alignment made manufacturing and testing challenging. We developed new metrology systems at the AAO to verify the performance of these VPH gratings. The measured diffraction efficiencies and line frequency of the VPH gratings received so far meet the vendor's provided data. The wavefront quality for the Blue VPH grating is good but the Green and Red VPH gratings need to be post polishing.

  3. Gratings and their quasistatic equivalents for high optical absorptance

    SciTech Connect

    McPhedran, R. C.; Chen, P. Y.; Bonod, N.; Popov, E.

    2009-05-15

    We consider thin lamellar and cylinder gratings, composed of silicon carbide and air, and investigate the conditions under which they can totally absorb an incident plane wave, for both p and s polarizations. We also consider thin-film equivalent in the quasistatic limit to the gratings, deriving the effective dielectric tensor for cylinder gratings. We show that the accuracy of the quasistatic models is a strong function of polarization, wavelength, and grating thickness due to the resonant nature of the optical constants of silicon carbide but that these models can be quantitatively accurate and give a good qualitative guide to the parameter values under which thin gratings can deliver high optical absorptance.

  4. Fiber-bragg grating-loop ringdown method and apparatus

    DOEpatents

    Wang, Chuji

    2008-01-29

    A device comprising a fiber grating loop ringdown (FGLRD) system of analysis is disclosed. A fiber Bragg grating (FBG) or Long-Period grating (LPG) written in a section of single mode fused silica fiber is incorporated into a fiber loop. By utilizing the wing areas of the gratings' bandwidth as a wavelength dependent attenuator of the light transmission, a fiber grating loop ringdown concept is formed. One aspect of the present invention is temperature sensing, which has been demonstrated using the disclosed device. Temperature measurements in the areas of accuracy, stability, high temperature, and dynamic range are also described.

  5. Compact Bragg grating with embedded metallic nano-structures.

    PubMed

    Mu, Jianwei; Li, Xun; Huang, Wei-Ping

    2010-07-19

    A compact Bragg grating with embedded gapped metallic nano-structures is proposed and investigated theoretically. The Bragg grating consists of periodic planar metallic strips embedded in a dielectric waveguide. The grating exhibits distinct polarization characteristics due to its underlying working mechanisms of the metallic nano-strips. The grating can be considered as insulator-metal-insulator surface plasmonic polariton waveguide grating with improved light confinement for TM polarized waves. For the TE waves, significant field mismatch between metal and non-metal sections of the grating results in strong reflection. Comparison with the conventional deeply-etched grating on the same waveguide structures reveals interesting characteristics. It is concluded that the two types of grating structures share similar guidance, reflection and loss mechanisms for the TE modes. The spectral characteristics and their dependences on grating duty cycle are drastically different for the TM modes, mainly due to the SPP effect for the metal. Although the proposed grating performs slightly worse comparing to the deeply-etched grating for TE waves, its fabrication process should be easier since there will be no narrow trench (in sub-microns) deep-etching process (up to a few microns in depth) involved.

  6. Single-order diffraction grating designed by trapezoidal transmission function.

    PubMed

    Fan, Quanping; Liu, Yuwei; Wang, Chuanke; Yang, Zuhua; Wei, Lai; Zhu, Xiaoli; Xie, Changqing; Zhang, Qiangqiang; Qian, Feng; Yan, Zhuoyang; Gu, Yuqiu; Zhou, Weimin; Jiang, Gang; Cao, Leifeng

    2015-06-01

    Diffraction grating is a widely used dispersion element in spectral analysis from the infrared to the x-ray region. Traditionally, it has a square-wave transmission function, suffering from high-order diffraction contamination. Single-order diffraction can be achieved by sinusoidal amplitude transmission grating, but the fabrication is difficult. Here, we propose a novel idea to design a grating based on trapezoidal transmission function, which makes traditional grating a special case. Grating designed by this idea can not only suppress higher order diffraction by several orders of magnitude as sinusoidal amplitude grating does but also greatly reduce the fabrication difficulty to the level of processing for traditional grating. It offers a new opportunity for fabrication of grating with single-order diffraction and measurement of spectrum without contamination of high-order harmonic components. This idea can easily extend to varied-line-space grating, concave grating with single-order diffraction, or zone plates with single foci and will bring great changes in the field of grating applications.

  7. High resolution Florida IR silicon immersion grating spectrometer and an M dwarf planet survey

    NASA Astrophysics Data System (ADS)

    Ge, Jian; Powell, Scott; Zhao, Bo; Wang, Ji; Fletcher, Adam; Schofield, Sidney; Liu, Jian; Muterspaugh, Matthew; Blake, Cullen; Barnes, Rory

    2012-09-01

    We report the system design and predicted performance of the Florida IR Silicon immersion grating spectromeTer (FIRST). This new generation cryogenic IR spectrograph offers broad-band high resolution IR spectroscopy with R=72,000 at 1.4-1.8 μm and R=60,000 at 0.8-1.35 μm in a single exposure with a 2kx2k H2RG IR array. It is enabled by a compact design using an extremely high dispersion silicon immersion grating (SIG) and an R4 echelle with a 50 mm diameter pupil in combination with an Image Slicer. This instrument is operated in vacuum with temperature precisely controlled to reach long term stability for high precision radial velocity (RV) measurements of nearby stars, especially M dwarfs and young stars. The primary technical goal is to reach better than 4 m/s long term RV precision with J<9 M dwarfs within 30 min exposures. This instrument is scheduled to be commissioned at the Tennessee State University (TSU) 2-m Automatic Spectroscopic Telescope (AST) at Fairborn Observatory in spring 2013. FIRST can also be used for observing transiting planets, young stellar objects (YSOs), magnetic fields, binaries, brown dwarfs (BDs), ISM and stars. We plan to launch the FIRST NIR M dwarf planet survey in 2014 after FIRST is commissioned at the AST. This NIR M dwarf survey is the first large-scale NIR high precision Doppler survey dedicated to detecting and characterizing planets around 215 nearby M dwarfs with J< 10. Our primary science goal is to look for habitable Super-Earths around the late M dwarfs and also to identify transiting systems for follow-up observations with JWST to measure the planetary atmospheric compositions and study their habitability. Our secondary science goal is to detect and characterize a large number of planets around M dwarfs to understand the statistics of planet populations around these low mass stars and constrain planet formation and evolution models. Our survey baseline is expected to detect ~30 exoplanets, including 10 Super Earths

  8. Nonperiodic metallic gratings transparent for broadband terahertz waves

    NASA Astrophysics Data System (ADS)

    Ren, Xiao-Ping; Fan, Ren-Hao; Peng, Ru-Wen; Huang, Xian-Rong; Xu, Di-Hu; Zhou, Yu; Wang, Mu

    2015-01-01

    In this work, we demonstrate both theoretically and experimentally that nonperiodic metallic gratings can become transparent for broadband terahertz waves. It is shown that broadband high transmission appears in aperiodic metallic gratings (including quasiperiodic and disordered ones), which originates from the nonresonant excitations in the grating system. Quasiperiodic and disordered metallic gratings effectively weaken and even eliminate Wood's anomalies, which are the diffraction-related characters of periodic gratings. Consequently, both the transparence bandwidth and transmission efficiency are significantly increased due to the structural aperiodicity. An optimal condition is also achieved for broadband high transparency in aperiodic metallic gratings. Experimental measurements at the terahertz regime reasonably agree with both analytical analysis and numerical simulations. Furthermore, we show that for a specific light source, for example, a line source, a corresponding nonperiodic transparent grating can be also designed. We expect that our findings can be applied for transparent conducting panels, perfect white-beam polarizers, antireflective conducting solar cells, and beyond.

  9. Fabrication of liquid crystal gratings based on photoalignment technology

    NASA Astrophysics Data System (ADS)

    Lu, Yan-Qing; Hu, Wei; Srivastava, Abhishek; Chigrinov, Vladimir G.

    2013-03-01

    A serial of LC gratings are fabricated mainly based on photoalignment, which include (1) Nematic LC grating with alternating 90° twisted nematic (TN) regions and homogeneous alignment (PA). Both 1D and 2D diffraction gratings are demonstrated by periodic photoalignment of sulfonic azo-dye (SD1) films with a linearly polarized light beam. (2) A polarization independent of 1D/2D LC gratings with alternate orthogonal homogeneously aligned regions. No polarizer is employed. (3) A polarizer-free submillisecond response grating employing dual-frequency LC (DFLC) together with patterned hybrid aligned nematic (HAN) structures. To obtain instantly controllable LC microstructures rather than simple gratings, a digital micro-mirror device (DMD) based a micro-lithography system is developed. It may generate arbitrary micro-images on photoalignment layers. Besides normal phase gratings, more complex 2D patterns including quasicrystal structure are demonstrated, which give us more freedom to develop microstructured LC based photonic devices.

  10. Nanostructure Diffraction Gratings for Integrated Spectroscopy and Sensing

    NASA Technical Reports Server (NTRS)

    Guo, Junpeng (Inventor)

    2016-01-01

    The present disclosure pertains to metal or dielectric nanostructures of the subwavelength scale within the grating lines of optical diffraction gratings. The nanostructures have surface plasmon resonances or non-plasmon optical resonances. A linear photodetector array is used to capture the resonance spectra from one of the diffraction orders. The combined nanostructure super-grating and photodetector array eliminates the use of external optical spectrometers for measuring surface plasmon or optical resonance frequency shift caused by the presence of chemical and biological agents. The nanostructure super-gratings can be used for building integrated surface enhanced Raman scattering (SERS) spectrometers. The nanostructures within the diffraction grating lines enhance Raman scattering signal light while the diffraction grating pattern of the nanostructures diffracts Raman scattering light to different directions of propagation according to their wavelengths. Therefore, the nanostructure super-gratings allows for the use of a photodetector array to capture the surface enhanced Raman scattering spectra.

  11. Nanostructure Diffraction Gratings for Integrated Spectroscopy and Sensing

    NASA Technical Reports Server (NTRS)

    Guo, Junpeng (Inventor)

    2015-01-01

    The present disclosure pertains to metal or dielectric nanostructures of the subwavelength scale within the grating lines of optical diffraction gratings. The nanostructures have surface plasmon resonances or non-plasmon optical resonances. A linear photodetector array is used to capture the resonance spectra from one of the diffraction orders. The combined nanostructure super-grating and photodetector array eliminates the use of external optical spectrometers for measuring surface plasmon or optical resonance frequency shift caused by the presence of chemical and biological agents. The nanostructure super-gratings can be used for building integrated surface enhanced Raman scattering (SERS) spectrometers. The nanostructures within the diffraction grating lines enhance Raman scattering signal light while the diffraction grating pattern of the nanostructures diffracts Raman scattering light to different directions of propagation according to their wavelengths. Therefore, the nanostructure super-gratings allows for the use of a photodetector array to capture the surface enhanced Raman scattering spectra.

  12. Subwavelength transmission gratings for polarization separation in the infrared

    NASA Astrophysics Data System (ADS)

    Vayalamkuzhi, Pramitha; Sridharan, Gayathri M.; Bhattacharya, Shanti

    2016-04-01

    Subwavelength gratings exhibit attractive polarizing properties and have promising applications in communication, optical information processing, holography, and displays. The fabrication of subwavelength binary gratings for operation as polarizing beam splitters (PBS) at a wavelength of 1550 nm is presented. A simplified modal method was used for the design as well as to predict the efficiencies of the polarization components in each order. Electron beam lithography has been employed for patterning subwavelength grating structures on polymethyl methacrylate (PMMA) resist. The fixed beam moving stage patterning mode is used for patterning gratings with a period of 936 nm and width of 374 nm. The exposure and developing parameters are optimized to realize the grating with the designed feature sizes on PMMA resist. Gratings patterned using the optimized exposure and development parameters match well with the design, except for the height. The performance of the fabricated PBS grating has been evaluated by optical testing. The experimental results match well with the predictions.

  13. First order Bragg grating filters in silicon on insulator waveguides

    NASA Astrophysics Data System (ADS)

    Waugh, Peter Michael

    2008-08-01

    The subject of this project is the design; analysis, fabrication and characterisation of first order Bragg Grating optical filters in Silicon-on-Insulator (SOI) planar waveguides. It is envisaged that this work will result in the possibility of Bragg Grating filters for use in Silicon Photonics. It is the purpose of the work to create as far as is possible flat surface waveguides so as to facilitate Thermo-Optic tuning and also the incorporation into rib-waveguide Silicon Photonics. The spectral response of the shallow Bragg Gratings was modelled using Coupled Mode Theory (CMT) by way of RSoft Gratingmod TM. Also the effect of having a Bragg Grating with alternate layers of refractive index of 1.5 and 3.5 was simulated in order to verify that Silica and Silicon layered Bragg Gratings could be viable. A series of Bragg Gratings were patterned on 1.5 micron SOI at Philips in Eindhoven, Holland to investigate the variation of grating parameters with a) the period of the gratings b) the mark to space ratio of the gratings and c) the length of the region converted to Bragg Gratings (i.e. the number of grating period repetitions). One set of gratings were thermally oxidised at Philips in Eindhoven and another set were ion implanted with Oxygen ions at the Ion Beam Facility, University of Surrey, England. The gratings were tested and found to give transmission minima at approximately 1540 nanometres and both methods of creating flat surfaces were found to give similar minima. Atomic Force Microscopy was applied to the grating area of the as-implanted samples in the Advanced Technology Institute, University of Surrey, which were found to have surface undulations in the order of 60 nanometres.

  14. New methods of fabricating gratings for deformation measurements: A review

    NASA Astrophysics Data System (ADS)

    Dai, Xianglu; Xie, Huimin

    2017-05-01

    Gratings have been widely accepted as practical and effective deformation carriers/sensors and are commonly used in many deformation measurement methods. Since the deformation measurement sensitivity is directly proportional to the grating frequency, and the measurement accuracy is strongly affected by the grating quality. Thus, it is crucial to prepare an appropriate grating on the specimen surface that is to be measured. Over the past few decades, an increasing number of grating fabrication methods have been developed, including holographic photolithography, electron beam lithography, focused ion beam etching, nanoimprinting, soft lithography, and others. Although substantial literature regarding grating fabrication can be found, a comprehensive review is still necessary to promote the application of these methods. This review introduces the technical details and characteristics of recently developed grating fabrication methods and provides suggestions of which grating fabrication methods to use in correspondence with different deformation measurement methods. Emphasis is placed on the introduction of grating fabrication processes and the quality and applicability of the resulting gratings.

  15. Binary-Phase Fourier Gratings for Nonuniform Array Generation

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.

    2003-01-01

    We describe a design method for a binary-phase Fourier grating that generates an array of spots with nonuniform, user-defined intensities symmetric about the zeroth order. Like the Dammann fanout grating approach, the binary-phase Fourier grating uses only two phase levels in its grating surface profile to generate the final spot array. Unlike the Dammann fanout grating approach, this method allows for the generation of nonuniform, user-defined intensities within the final fanout pattern. Restrictions governing the specification and realization of the array's individual spot intensities are discussed. Design methods used to realize the grating employ both simulated annealing and nonlinear optimization approaches to locate optimal solutions to the grating design problem. The end-use application driving this development operates in the near- to mid-infrared spectrum - allowing for higher resolution in grating specification and fabrication with respect to wavelength than may be available in visible spectrum applications. Fabrication of a grating generating a user-defined nine spot pattern is accomplished in GaAs for the near-infrared. Characterization of the grating is provided through the measurement of individual spot intensities, array uniformity, and overall efficiency. Final measurements are compared to calculated values with a discussion of the results.

  16. Varied line-space gratings: past, present and future

    SciTech Connect

    Hettrick, M.C.

    1985-08-01

    A classically ruled diffraction grating consists of grooves which are equidistant, straight and parallel. Conversely, the so-called ''holographic'' grating (formed by the interfering waves of coherent visible light), although severely constrained by the recording wavelength and recording geometry, has grooves which are typically neither equidistant, straight nor parallel. In contrast, a varied line-space (VLS) grating, in common nomenclature, is a design in which the groove positions are relatively unconstrained yet possess sufficient symmetry to permit mechanical ruling. Such seemingly exotic gratings are no longer only a theoretical curiosity, but have been ruled and used in a wide variety of applications. These include: (1) aberration-corrected normal incidence concave gratings for Seya-Namioka monochromators and optical de-multiplexers, (2) flat-field grazing incidence concave gratings for plasma diagnostics, (3) aberration-corrected grazing incidence plane gratings for space-borne spectrometers, (4) focusing grazing incidence plane grating for synchrotron radiation monochromators, and (5) wavefront generators for visible interferometry of optical surfaces (particularly aspheres). Future prospects of VLS gratings as dispersing elements, wavefront correctors and beamsplitters appear promising. The author discusses the history of VLS gratings, their present applications, and their potential in the future. 61 refs., 24 figs.

  17. Varied Line-Space Gratings: Past, Present And Future

    NASA Astrophysics Data System (ADS)

    Hettrick, Michael C.

    1986-05-01

    A classically ruled diffraction grating consists of grooves which are equidistant, straight and parallel. Conversely the so-called "holographic" grating ( formed by the interfering waves of coherent visible light ) , although severely constrained by the recording wavelength and recording geometry, has grooves which are typically neither equidistant, straight nor parallel. In contrast a varied line-space (VLS) grating, in common nomenclature, is a design in which the groove positions are relatively unconstrained yet possess sufficient symmetry to permit mechanical ruling. Such seemingly exotic gratings are no longer only a theoretical curiosity, but have been ruled and used in a wide variety of applications. These include 1) aberration-corrected normal incidence concave gratings for Seya-Namioka monochromators and optical demultiplexers, 2) flat-field grazing incidence concave gratings for plasma diagnostics, 3) aberration-corrected grazing incidence plane gratings for space-borne spectrometers, 4) focusing grazing incidence plane grating for synchrotron radiation monochromators, and 5) wavefront generators for visible interferometry of optical surfaces (particularly aspheres). Future prospects of VLS gratings as dispersing elements, wavefront correctors and beamsplitters appear promising. I discuss the history of VLS gratings, their present applications and their potential in the future.

  18. Fresnel diffraction of fractal grating and self-imaging effect.

    PubMed

    Wang, Junhong; Zhang, Wei; Cui, Yuwei; Teng, Shuyun

    2014-04-01

    Based on the self-similarity property of fractal, two types of fractal gratings are produced according to the production and addition operations of multiple periodic gratings. Fresnel diffractions of fractal grating are analyzed theoretically, and the general mathematic expressions of the diffraction intensity distributions of fractal grating are deduced. The gray-scale patterns of the 2D diffraction distributions of fractal grating are provided through numerical calculations. The diffraction patterns take on the periodicity along the longitude and transverse directions. The 1D diffraction distribution at some certain distances shows the same structure as the fractal grating. This indicates that the self-image of fractal grating is really formed in the Fresnel diffraction region. The experimental measurement of the diffraction intensity distribution of fractal grating with different fractal dimensions and different fractal levels is performed, and the self-images of fractal grating are obtained successfully in experiments. The conclusions of this paper are helpful for the development of the application of fractal grating.

  19. Fluidized bed boiler having a segmented grate

    DOEpatents

    Waryasz, Richard E.

    1984-01-01

    A fluidized bed furnace (10) is provided having a perforate grate (9) within a housing which supports a bed of particulate material including some combustibles. The grate is divided into a plurality of segments (E2-E6, SH1-SH5, RH1-RH5), with the airflow to each segment being independently controlled. Some of the segments have evaporating surface imbedded in the particulate material above them, while other segments are below superheater surface or reheater surface. Some of the segments (E1, E7) have no surface above them, and there are ignitor combustors (32, 34) directed to fire into the segments, for fast startup of the furnace without causing damage to any heating surface.

  20. Theory of Fiber Optical Bragg Grating: Revisited

    NASA Technical Reports Server (NTRS)

    Tai, H.

    2003-01-01

    The reflected signature of an optical fiber Bragg grating is analyzed using the transfer function method. This approach is capable to cast all relevant quantities into proper places and provides a better physical understanding. The relationship between reflected signal, number of periods, index of refraction, and reflected wave phase is elucidated. The condition for which the maximum reflectivity is achieved is fully examined. We also have derived an expression to predict the reflectivity minima accurately when the reflected wave is detuned. Furthermore, using the segmented potential approach, this model can handle arbitrary index of refraction profiles and compare the strength of optical reflectivity of different profiles. The condition of a non-uniform grating is also addressed.

  1. Binocular vision measurement using Dammann grating.

    PubMed

    Wei, Shengbin; Wang, Shaoqing; Zhou, Changhe; Liu, Kun; Fan, Xin

    2015-04-10

    In this paper, we propose a novel three-dimensional (3D) profilometry using a binocular camera and a 64 × 64 Dammann grating for generation of a regular square laser array. A new constraint called a "ray constraint," taking advantage of the splitting characteristic of Dammann grating, is proposed for binocular matching. Binocular matching is realized by using ray constraint and precalibration of a laser array. Point clouds without outliers are obtained with binocular matching results according to triangulation. The experimental apparatus weighs less than 170 g with a width of less than 14 cm. We used this apparatus to scan a statue of Apollo under indoor illumination (at 450 lux). Its 3D model with complex profile was reconstructed by more than 150,000 points. This 3D profilometry has advantages of low cost, low power, and small size and should be useful for practical applications.

  2. Transmission Grating Measurements of Undulator K

    SciTech Connect

    Bionta, R M; Ott, L L

    2006-05-15

    This study was undertaken to understand the practicalities of determine K differences in the undulator modules by measuring single-shot x-ray spectra of the spontaneous radiation with a transmissive grating spectrometer under development to measure FEL spectra. Since the quality of the FEL is dependent on a uniform K value in all the undulator modules, being able to measure the relative undulator K values is important. Preliminary results were presented in a presentation, ''Use of FEL Off-Axis Zone Plate Spectrometer to Measure Relative K by the Pinhole/Centroid Method'', at the ''LCLS Beam-Based Undulator K Measurements Workshop'' on November 14, 2005 (UCRL-PRES-217281). This study applies equally well to reflective gratings of the appropriate period and inclinations.

  3. Transmission Grating Measurements of Undulator K

    SciTech Connect

    Bionta, R. M.

    2010-12-01

    This study was undertaken to understand the practicalities of determine K differences in the undulator modules by measuring single-shot x-ray spectra of the spontaneous radiation with a transmissive grating spectrometer under development to measure FEL spectra. Since the quality of the FEL is dependent on a uniform K value in all the undulator modules, being able to measure the relative undulator K values is important. Preliminary results were presented in a presentation, 'Use of FEL Off-Axis Zone Plate Spectrometer to Measure Relative K by the Pinhole/Centroid Method', at the 'LCLS Beam-Based Undulator K Measurements Workshop' on November 14, 2005 (UCRL-PRES-217281). This study applies equally well to reflective gratings of the appropriate period and inclinations.

  4. Photoelectrical encoder employing an optical grating

    SciTech Connect

    Kabaya, Y.

    1985-02-12

    A photoelectrical encoder is disclosed wherein a physical quantity is detected from brightness obtained by moving a first and a second scale. Each scale is provided thereon with an optical grating relative to each other. The grating in one of the scales is constructed such that a first signal lead-out material layer made of a light shielding conductive material, a PN semiconductor layer for converting light into electricity, and a second signal lead-out material layer made of a light transmitting conductive material are laminated on a light transmitting base member to form a narrow belt-shaped light receiving portion and a plurality of narrow belt-shaped light receiving portions arranged at regular pitches. Against the light from the light transmitting base member, the light receiving portions function as light shielding slits, and intervals between the light receiving portions are formed into light transmitting slits.

  5. SH Wave Scattering from a Sinusoidal Grating

    DTIC Science & Technology

    1989-08-01

    468-471. Rayleigh , Lord (J. W. Strutt ) (1907). On the dynamical theory of gratings, Proc. Roy. Soc., Ser. A. 79, 399-416. 32 Varadan, V. K., A...version of the Rayleigh method, formulated in the wavenumber domain. However, since Lippmann (1953) questioned the expansion used in the Rayleigh method...the so called " Rayleigh ansatz", the history of this modeling approach has been shrouded in controversy. Lippmann suggested that the Rayleigh

  6. Aspheric grating for extreme ultraviolet astronomy

    NASA Technical Reports Server (NTRS)

    Kastner, S. O.; Wade, C., Jr.

    1978-01-01

    A family of plane curves is developed which can diffract incident parallel rays to a point focus. These curves, termed diffractoidal curves, are rotated around an axis to produce surfaces of revolution correspondingly termed diffractoids, whose imaging properties for sources at infinity are studied by ray tracing in a few examples. The paraboloid emerges as a limiting case of the diffractoid. A comparison is made between the stigmatic focusing properties of the diffractoid and the toroidal grating.

  7. Miniature Grating for Spectrally-Encoded Endoscopy

    PubMed Central

    Kang, Dongkyun; Martinez, Ramses V.; Whitesides, George M.

    2013-01-01

    Spectrally-encoded endoscopy (SEE) is an ultraminiature endoscopy technology that acquires high-definition images of internal organs through a sub-mm endoscopic probe. In SEE, a grating at the tip of the imaging optics diffracts the broadband light into multiple beams, where each beam with a distinctive wavelength is illuminated on a unique transverse location of the tissue. By encoding one transverse coordinate with the wavelength, SEE can image a line of the tissue at a time without using any beam scanning devices. This feature of the SEE technology allows the SEE probe to be miniaturized to sub-mm dimensions. While previous studies have shown that SEE has the potential to be utilized for various clinical imaging applications, the translation of SEE for medicine has been hampered by challenges in fabricating the miniature grating inherent to SEE probes. This paper describes a new fabrication method for SEE probes. The new method uses a soft lithographic approach to pattern a high-aspect-ratio grating at the tip of the miniature imaging optics. Using this technique, we have constructed a 500-μm-diameter SEE probe. The miniature grating at the tip of the probe had a measured diffraction efficiency of 75%. The new SEE probe was used to image a human finger and formalin fixed mouse embryos, demonstrating the capability of this device to visualize key anatomic features of tissues with high image contrast. In addition to providing high quality imaging SEE optics, the soft lithography method allows cost-effective and reliable fabrication of these miniature endoscopes, which will facilitate the clinical translation of SEE technology. PMID:23503940

  8. Long period gratings in photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Ju, Jian; Jin, Wei

    2012-03-01

    The authors review the recent advances in fabricating long-period gratings (LPGs) in photonic crystal fibers (PCFs). The novel light-guiding properties of the PCFs allow the demonstration of novel sensors and devices based on such LPGs. The sensitivity of these PCF LPGs to temperature, strain and refractive index is discussed and compared with LPGs made on conventional single-mode fibers. In-fiber devices such as tunable band rejection filters, Mach-Zehnder interferometers are discussed.

  9. Development and validation of the 'Echelle de Motivation envers l'Activité Physique en contexte de Santé': A motivation scale towards health-oriented physical activity in French.

    PubMed

    Boiché, Julie; Gourlan, Mathieu; Trouilloud, David; Sarrazin, Philippe

    2016-11-21

    This article presents the validation of the 'Echelle de Motivation envers l'Activité Physique en contexte de Santé' including the six forms of motivation underlined by self-determination theory. Study 1 underlines the content validity of a pool of 30 items (N = 20). Study 2 supports the six-factor structure validity of the 18-item Echelle de Motivation envers l'Activité Physique en contexte de Santé (N = 309). Study 3 (N = 191) confirms structure validity, as well as concurrent validity and 2-week temporal reliability. The Echelle de Motivation envers l'Activité Physique en contexte de Santé can be considered as a valid and reliable tool to use in prevention or rehabilitation contexts.

  10. Fiber Bragg grating based tunable sensitivity goniometer

    NASA Astrophysics Data System (ADS)

    Padma, Srivani; Umesh, Sharath; Pant, Shweta; Srinivas, Talabattula; Asokan, Sundarrajan

    2016-03-01

    Goniometer has found extensive usage in diverse applications, primary being medical field in which it is employed for obtaining the range of motion of joints during physical therapy. It is imperative to have a dynamic system to measure the range of motion which will aid for a progressive therapeutic treatment. Hence in the present study, a novel goniometer for real time dynamic angle measurement between two surfaces with the aid of a Fiber Bragg Grating sensor is proposed. The angular rotation between the two surfaces will be identified by the two arms of the Fiber Bragg Grating Goniometer (FBGG), which is translated to the rotation of the shaft which holds these arms together. A cantilever beam is fixed onto the base plate whose free end is connected to the rotating shaft. The rotating shaft will actuate a mechanism which will pull the free end of the cantilever resulting in strain variation over the cantilever beam. The strain variation on the cantilever beam is measured by the Fiber Bragg Grating sensor bonded over it. Further, the proposed FBGG facilitates tunable sensitivity by the discs of varying diameters on the rotating shaft. Tunable sensitivity of the FBGG is realised by the movement of these discs by varying circumferential arc lengths for the same angular movement, which will actuate the pull on the cantilever beam. As per the requirement of the application in terms of resolution and range of angular measurement, individual mode of sensitivity may be selected.

  11. Imaging Spectrometers Using Concave Holographic Gratings

    NASA Technical Reports Server (NTRS)

    Gradie, J.; Wang, S.

    1993-01-01

    Imaging spectroscopy combines the spatial attributes of imaging with the compositionally diagnostic attributes of spectroscopy. For spacebased remote sensing applications, mass, size, power, data rate, and application constrain the scanning approach. For the first three approaches, substantial savings in mass and size of the spectrometer can be achieved in some cases with a concave holographic grating and careful placement of an order-sorting filter. A hologram etched on the single concave surface contains the equivalent of the collimating, dispersing, and camera optics of a conventional grating spectrometer and provides substantial wavelength dependent corrections for spherical aberrations and a flat focal field. These gratings can be blazed to improve efficiency when used over a small wavelength range or left unblazed for broadband uniform efficiency when used over a wavelength range of up to 2 orders. More than 1 order can be imaged along the dispersion axis by placing an appropriately designed step order-sorting filter in front of the one- or two-dimensional detector. This filter can be shaped for additional aberration corrections. The VIRIS imaging spectrometer based on the broadband design provides simultaneous imaging of the entrance slit from lambda = 0.9 to 2.6 microns (1.5 orders) onto a 128 x 128 HgCdTe detector (at 77 K). The VIRIS spectrometer was used for lunar mapping with the UH 24.in telescope at Mauna Kea Observatory. The design is adaptable for small, low mass, space based imaging spectrometers.

  12. Grating THz laser with optical pumping

    NASA Astrophysics Data System (ADS)

    Khoury, Jed; Haji-saeed, Bahareh; Woods, Charles; Kierstead, John

    2010-04-01

    In this paper, we present a design for a widely tunable solid-state optically and electrically pumped THz laser based on the Smith-Purcell free-electron laser. In the free-electron laser, an energetic electron beam pumps a metallic grating to generate surface plasmons. Our solid-state optically pumped design consists of a thin layer of dielectic, such as SiNx, sandwiched between a corrugated structure and a thin metal or semiconductor layer. The lower layer is for current streaming, and replaces the electron beam in the original design. The upper layer consists of one micro-grating for coupling the electromagnetic field in, another for coupling out, and a nano-grating for coupling with the current in the lower layer for electromagnetic field generation. The surface plasmon waves generated from the upper layer by an external electromagnetic field, and the lower layer by the applied current, are coupled. Emission enhancement occurs when the plasmonic waves in both layers are resonantly coupled.

  13. Diffractive coherence in multilayer dielectric gratings

    SciTech Connect

    Shore, B.W.; Feit, M.D.; Perry, M.D.; Boyd, R.D.; Britten, J.A.; Li, Lifeng

    1995-05-26

    Successful operation of large-scale high-power lasers, such as those in use and planned at LLNL and elsewhere, require optical elements that can withstand extremely high fluences without suffering damage. Of particular concern are dielectric diffraction gratings used for beam sampling and pulse compression. Laser induced damage to bulk dielectric material originates with coupling of the electric field of the radiation to bound electrons, proceeding through a succession of mechanisms that couple the electron kinetic energy to lattice energy and ultimately to macroscopic structural changes (e.g. melting). The constructive interference that is responsible for the diffractive behavior of a grating or the reflective properties of a multilayer dielectric stack can enhance the electric field above values that would occur in unstructured homogeneous material. Much work has been done to model damage to bulk matter. The presence of nonuniform electric fields, resulting from diffractive coherence, has the potential to affect damage thresholds and requires more elaborate theory. We shall discuss aspects of work directed towards understanding the influence of dielectric structures upon damage, with particular emphasis on computations and interpretation of electric fields within dielectric gratings and multilayer dielectric stacks, noting particularly the interference effects that occur in these structures.

  14. Grating Loaded Cantilevers for Displacement Measurements

    NASA Astrophysics Data System (ADS)

    Karademir, Ertugrul; Olcum, Selim; Atalar, Abdullah; Aydinli, Atilla

    2010-03-01

    A cantilever with a grating coupler engraved on its tip is used for measuring displacement. The coupled light in the cantilever is guided to a single mode optical waveguide defined at the base of the cantilever. The grating period is 550 nm and is fabricated on a SOI wafer using nanoimprint lithography. The waveguide and the cantilever are defined by an RIE and cantilevers released by KOH and HF solutions. Light with 1550 nm wavelength, is directed onto the grating coupler and detected at the cleaved end of the SOI waveguide. The angle of incidence is controlled by a motorized rotary stage. Light couples into the waveguide at a characteristic angle with a full width at half maximum of approximately 6.9 mrads translating into a Q factor of 87.5. The displacement sensitivity is measured by driving the cantilever with a frequency controlled piezoelectric element. The modulation of the light at the waveguide output is lock-in detected by a biased infrared detector. The resulting 43%mrad-1 sensitivity can be increased with further optimization.

  15. Ultrafast transient grating radiation to optical image converter

    DOEpatents

    Stewart, Richard E; Vernon, Stephen P; Steel, Paul T; Lowry, Mark E

    2014-11-04

    A high sensitivity transient grating ultrafast radiation to optical image converter is based on a fixed transmission grating adjacent to a semiconductor substrate. X-rays or optical radiation passing through the fixed transmission grating is thereby modulated and produces a small periodic variation of refractive index or transient grating in the semiconductor through carrier induced refractive index shifts. An optical or infrared probe beam tuned just below the semiconductor band gap is reflected off a high reflectivity mirror on the semiconductor so that it double passes therethrough and interacts with the radiation induced phase grating therein. A small portion of the optical beam is diffracted out of the probe beam by the radiation induced transient grating to become the converted signal that is imaged onto a detector.

  16. Towards freeform curved blazed gratings using diamond machining

    NASA Astrophysics Data System (ADS)

    Bourgenot, C.; Robertson, D. J.; Stelter, D.; Eikenberry, S.

    2016-07-01

    Concave blazed gratings greatly simplify the architecture of spectrographs by reducing the number of optical components. The production of these gratings using diamond-machining offers practically no limits in the design of the grating substrate shape, with the possibility of making large sag freeform surfaces unlike the alternative and traditional method of holography and ion etching. In this paper, we report on the technological challenges and progress in the making of these curved blazed gratings using an ultra-high precision 5 axes Moore-Nanotech machine. We describe their implementation in an integral field unit prototype called IGIS (Integrated Grating Imaging Spectrograph) where freeform curved gratings are used as pupil mirrors. The goal is to develop the technologies for the production of the next generation of low-cost, compact, high performance integral field unit spectrometers.

  17. Cryogenic performance of high-efficiency germanium immersion grating

    NASA Astrophysics Data System (ADS)

    Sarugaku, Yuki; Ikeda, Yuji; Kaji, Sayumi; Kobayashi, Naoto; Sukegawa, Takashi; Arasaki, Takayuki; Kondo, Sohei; Nakanishi, Kenshi; Yasui, Chikako; Kawakita, Hideyo

    2016-08-01

    Immersion gratings will play important roles for infrared astronomy in the next generation. We have been developing immersion gratings with a variety of kinds of materials and have succeeded in fabricating a high-efficiency germanium (Ge) immersion grating with both a reflection coating on the grating surface and an AR coating on the entrance surface. The grating will be installed in a K-, L-, and M-bands (2-5μm) high-resolution (R=80,000) spectrograph, VINROUGE, which is a prototype for the TMT MIR instrument. In this paper, we report the preliminary results on the evaluation of the Ge immersion grating. We confirmed that the peak absolute diffraction efficiency was in the range of 70-80%, which was as expected from the design, at both room and cryogenic temperatures.

  18. Spatial phase-shifting characteristic of double grating interferometer.

    PubMed

    Song, Yang; Chen, Yunyun; He, Anzhi; Zhao, Zhimin

    2009-10-26

    Double grating interferometer is usually used to achieve phase information from distorted wave front by its temporal phase-shifting characteristic. In this paper, the spatial phase-shifting characteristic of double grating interferometer is presented. The explicit intensity distributions of interferograms produced by double gratings are derived with the scalar diffraction theory, and the stable phase shift is found between plus-first, zero and minus-first order interferograms. Results indicate that the phase shift only depends on the grating period and the distance between two gratings if no phase object exists. If phase object exists, it varies on the interferograms. But the phase shifts are equal at any special point of interferograms. In particular, the triple grating interferometer is presented to generate at least four phase shift interferograms simultaneously with the similar method.

  19. Broadband optical concentration technology based on grating side-coupling

    NASA Astrophysics Data System (ADS)

    Lu, Luyun; Wang, Kaiwei

    2014-08-01

    Though the technology of grating side-coupling is often applied in fields, such as coupling of light of single wavelength or narrow waveband, pump of fiber laser, integration of optical waveguide, its application for broadband coupling of visible spectrum is rarely studied. Sunlight can concentrate and output at the edge of waveguides by integrating sub-wavelength gratings with waveguides, making it a novel solar concentrator. In this paper, we simulated different grating structures with the finite-difference time-domain solution software (FDTD) to obtain the optimal structure design, since different grating structures feature different diffractive efficiencies. The result demonstrates that the structures mentioned above all feature good diffractive efficiencies in broadband wavelength, among which the blazing grating reaches the largest efficiency, namely 48.8%.This kind of sub-wavelength gratings feature integration of small size, which makes it promising in absorption of solar energy, such as lumination, photovoltaic cell, space melting, etc.

  20. Arrayed waveguide grating interrogator for fiber Bragg grating sensors: measurement and simulation.

    PubMed

    Koch, Jan; Angelmahr, Martin; Schade, Wolfgang

    2012-11-01

    A fiber Bragg grating (FBG) interrogation system based on an intensity demodulation and demultiplexing of an arrayed waveguide grating (AWG) module is examined in detail. The influence of the spectral line shape of the FBG on the signal obtained from the AWG device is discussed by accomplishing the measurement and simulation of the system. The simulation of the system helps to create quickly and precisely calibration functions for nonsymmetric, tilted, or nonapodized FBGs. Experiments show that even small sidebands of nonapodized FBGs have strong influences on the signal resulted by an AWG device with a Gaussian profile.

  1. Diffraction Grating Efficiency Calculations Based on Real Groove Profiles

    NASA Technical Reports Server (NTRS)

    Content, David; Sroda, Tom; Palmer, Christopher; Kuznetsov, Ivan

    2000-01-01

    The program we are attempting to bring about combines 3 difficult features, in order to demonstrate accuracy of efficiency predictions: (1) Accurate groove metrology methods on surface relief gratings; (2) Rigorous and usable electromagnetic efficiency calculation codes; (3) Accurate efficiency measurements in polarized light The benefit would be an increase in yield for high-performance gratings. Many such applications suffer long lead time or serious performance loss when new gratings are made which do not meet requirements or expectations.

  2. Manipulation of plasma grating by impulsive molecular alignment

    SciTech Connect

    Lu, Peifen; Wu, Jian; Zeng, Heping

    2013-11-25

    We experimentally demonstrated that multiphoton-ionization-induced plasma grating in air could be precisely manipulated by impulsive molecular alignment. In the linear region, the impulsively aligned molecules modulated the diffraction efficiency of the plasma grating for a time-delayed femtosecond laser pulse. In the nonlinear region, the third harmonic generation from the plasma grating was either enhanced or suppressed by following the alignment of the molecules.

  3. The Giant Branch of omega Centauri. IV. Abundance Patterns Based on Echelle Spectra of 40 Red Giants

    NASA Astrophysics Data System (ADS)

    Norris, John E.; Da Costa, G. S.

    1995-07-01

    Abundances of some 20 elements have been determined for a (biased) sample of 40 red giants having Mv < -1.5 in the chemically inhomogeneous globular cluster ω Centauri. The results are based on high-resolution, high signal-to-noise echelle spectra and permit one to examine the roles of primordial enrichment and stellar evolutionary mixing effects in the cluster. Our basic conclusions are as follows (1) There is an abundance range -1.8 < [Fe/H] < -0.8, and even more metal rich stars may exist in the cluster. (2) For the α (Mg, Si, Ca, Ti) and iron peak (Cr, Ni) elements and Sc and V, [metal/Fe] is flat as a function of [Fe/H] and is consistent with primordial enrichment from stars having mass greater than 10 Msun, as has been found for field halo stars. (3) There is a large scatter in the abundances of C, N, and 0. The bulk of the stars have -0.9 < [C/Fe] < -0.3 and [O/Fe] ˜ 0.3, as is found at the red giant branch tip in other "normal" (showing no spread in [Fe/H]) clusters of similar abundance, while there also exists a group of CN-strong stars having [C/Fe] ˜ -0.7 and [O/Fe] ˜ -0.5. Nitrogen appears to be enhanced in all of these carbon-depleted stars. These results are most readily explained in terms of evolutionary mixing effects not predicted by standard stellar evolution calculations and are consistent with the earlier suggestions of Cohen & Bell (1986) and Paltoglou & Norris (1989) concerning processing in both the CN and ON cycles in the stars being observed. In contrast, the group of CO-strong stars first identified by Persson et al. (1980) has [C/Fe] ˜ 0.0, [O/Fe] ˜ 0.4, and [N/Fe] ˜ 0.4 (or 0.9 if the nitrogen scale of Brown and Wallerstein is correct) and is suggestive of primordial enrichment of carbon and/or nitrogen from intermediate- and possibly low-mass stars, tempered by later stellar evolutionary effects. (4) [Na/Fe] and [Al/Fe] are anticorrelated with [O/Fe], and there is a positive correlation between [Na/Fe] and [Al/Fe], all of which

  4. High-fidelity replication of Dammann gratings using soft lithography.

    PubMed

    Wang, Wei; Zhou, Changhe; Jia, Wei

    2008-04-01

    We report the experimental results of using the soft lithography method for replication of Dammann gratings. By using an elastomeric stamp, uniform grating structures were transferred to the UV-curable polymer. To evaluate the quality of the replication, diffraction images and light intensity were measured. Compared with the master devices, the replicas of Dammann gratings show a slight deviation in both surface relief profile and optical performance. Experimental results demonstrated that high-fidelity replication of Dammann gratings is realized by using soft lithography with low cost and high throughput.

  5. A millimeter wavelength radiation source using a dual grating resonator

    SciTech Connect

    Killoran, J.H.; Hacker, F.L.; Walsh, J.E. . Dept. of Physics)

    1994-10-01

    A novel means of producing coherent radiation by passing an electron through a dual-grating resonator is presented. The observed radiation is in accordance with the Smith-Purcell dispersion relation for a single grating. Feedback is provided by a second grating. Experiments carried out at beam energies from 30--55 KeV produced radiation at wavelengths from 6 to 0.75 mm. Power measurements were used to clarify the grating-beam interaction. Indications are that operation could be easily extended to shorter wavelengths to provide an inexpensive and compact radiation source in the far-infrared.

  6. Spherical grating based x-ray Talbot interferometry

    SciTech Connect

    Cong, Wenxiang E-mail: xiy2@rpi.edu Xi, Yan E-mail: xiy2@rpi.edu Wang, Ge E-mail: xiy2@rpi.edu

    2015-11-15

    Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and

  7. Stratified Diffractive Optic Approach for Creating High Efficiency Gratings

    NASA Technical Reports Server (NTRS)

    Chambers, Diana M.; Nordin, Gregory P.

    1998-01-01

    Gratings with high efficiency in a single diffracted order can be realized with both volume holographic and diffractive optical elements. However, each method has limitations that restrict the applications in which they can be used. For example, high efficiency volume holographic gratings require an appropriate combination of thickness and permittivity modulation throughout the bulk of the material. Possible combinations of those two characteristics are limited by properties of currently available materials, thus restricting the range of applications for volume holographic gratings. Efficiency of a diffractive optic grating is dependent on its approximation of an ideal analog profile using discrete features. The size of constituent features and, consequently, the number that can be used within a required grating period restricts the applications in which diffractive optic gratings can be used. These limitations imply that there are applications which cannot be addressed by either technology. In this paper we propose to address a number of applications in this category with a new method of creating high efficiency gratings which we call stratified diffractive optic gratings. In this approach diffractive optic techniques are used to create an optical structure that emulates volume grating behavior. To illustrate the stratified diffractive optic grating concept we consider a specific application, a scanner for a space-based coherent wind lidar, with requirements that would be difficult to meet by either volume holographic or diffractive optic methods. The lidar instrument design specifies a transmissive scanner element with the input beam normally incident and the exiting beam deflected at a fixed angle from the optical axis. The element will be rotated about the optical axis to produce a conical scan pattern. The wavelength of the incident beam is 2.06 microns and the required deflection angle is 30 degrees, implying a grating period of approximately 4 microns

  8. Diffraction Gratings for High-Intensity Laser Applications

    SciTech Connect

    Britten, J

    2008-01-23

    The scattering of light into wavelength-dependent discrete directions (orders) by a device exhibiting a periodic modulation of a physical attribute on a spatial scale similar to the wavelength of light has been the subject of study for over 200 years. Such a device is called a diffraction grating. Practical applications of diffraction gratings, mainly for spectroscopy, have been around for over 100 years. The importance of diffraction gratings in spectroscopy for the measurement of myriad properties of matter can hardly be overestimated. Since the advent of coherent light sources (lasers) in the 1960's, applications of diffraction gratings in spectroscopy have further exploded. Lasers have opened a vast application space for gratings, and apace, gratings have enabled entirely new classes of laser systems. Excellent reviews of the history, fundamental properties, applications and manufacturing techniques of diffraction gratings up to the time of their publication can be found in the books by Hutley (1) and more recently Loewen and Popov (2). The limited scope of this chapter can hardly do justice to such a comprehensive subject, so the focus here will be narrowly limited to characteristics required for gratings suitable for high-power laser applications, and methods to fabricate them. A particular area of emphasis will be on maximally-efficient large-aperture gratings for short-pulse laser generation.

  9. Widely tunable distributed-feedback lasers with chirped gratings

    NASA Astrophysics Data System (ADS)

    Xue, Liang; Brueck, S. R. J.; Kaspi, R.

    2009-04-01

    A quasicontinuous tuning range of 65 nm at 3.2 μm was obtained for continuous wave, single-longitudinal-mode operation at 77 K of an optically pumped distributed-feedback laser with a chirped grating. Interferometric lithography with spherical wavefronts was used to fabricate a large-area chirped grating whose period varied continuously in the direction of the grating lines. Tuning was achieved by translating the optical pump stripe relative to the device to activate regions with different grating periods. Methane absorption spectra, obtained using this tunable distributed-feedback laser, closely match the high-resolution transmission molecular absorption database simulations.

  10. Analysis on volume grating induced by femtosecond laser pulses.

    PubMed

    Zhou, Keya; Guo, Zhongyi; Ding, Weiqiang; Liu, Shutian

    2010-06-21

    We report on a kind of self-assembled volume grating in silica glass induced by tightly focused femtosecond laser pulses. The formation of the volume grating is attributed to the multiple microexplosion in the transparent materials induced by the femtosecond pulses. The first order diffractive efficiency is in dependence on the energy of the pulses and the scanning velocity of the laser greatly, and reaches as high as 30%. The diffraction pattern of the fabricated grating is numerically simulated and analyzed by a two dimensional FDTD method and the Fresnel Diffraction Integral. The numerical results proved our prediction on the formation of the volume grating, which agrees well with our experiment results.

  11. FIFI-LS diffraction grating vibration on SOFIA

    NASA Astrophysics Data System (ADS)

    Rebell, Felix; Beckmann, Simon; Bryant, Aaron; Colditz, Sebastian; Fischer, Christian; Fumi, Fabio; Hoenle, Rainer; Geis, Norbert; Iserlohe, Christof; Klein, Randolf; Krabbe, Alfred; Looney, Leslie; Poglitsch, Albrecht; Raab, Walfried; Savage, Maureen

    2016-08-01

    FIFI-LS (the Field Imaging Far Infrared Line Spectrometer for SOFIA) was successfully commissioned in 2014 during six flights on SOFIA. The observed wavelengths are set by rotating reflective gratings. In flight these gratings and their rotating mechanisms are exposed to vibrations. To quantify these vibrations, an acceleration sensor was placed on the exterior of the instrument. Simultaneously, the angle sensor of the grating was read out to analyze the movement of the grating. Based on this data, lab measurements were conducted to evaluate the effect of the vibrations on the image quality of FIFI-LS. The submitted paper will present the measured data and show the results of the analysis.

  12. Fiber optic security seal including plural Bragg gratings

    DOEpatents

    Forman, Peter R.

    1994-01-01

    An optical security system enables the integrity of a container seal to be remotely interrogated. A plurality of Bragg gratings is written holographically into the core of at least one optical fiber placed about the container seal, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer is provided with a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings to output a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings.

  13. Fiber optic security seal including plural Bragg gratings

    DOEpatents

    Forman, P.R.

    1994-09-27

    An optical security system enables the integrity of a container seal to be remotely interrogated. A plurality of Bragg gratings is written holographically into the core of at least one optical fiber placed about the container seal, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer is provided with a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings to output a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings. 2 figs.

  14. Wavelength-conserving grating router for intermediate wavelength density

    DOEpatents

    Deri, Robert J.; Patel, Rajesh R.; Bond, Steven W.; Bennett, Cory V.

    2007-03-20

    A wavelength router to be used for fiber optical networking router is based on a diffraction grating which utilizes only N wavelengths to interconnect N inputs to N outputs. The basic approach is to augment the grating with additional couplers or wavelength selective elements so than N-1 of the 2N-1 outputs are combined with other N outputs (leaving only N outputs). One embodiment uses directional couplers as combiners. Another embodiment uses wavelength-selective couplers. Another embodiment uses a pair of diffraction gratings to maintain parallel propagation of all optical beams. Also, beam combining can be implemented either by using retroflection back through the grating pair or by using couplers.

  15. Optical implementation of the Hopfield neural network with matrix gratings

    NASA Astrophysics Data System (ADS)

    Yeh, Sheng L.; Lo, Rong C.; Shi, Cha Y.

    2004-02-01

    We propose a new method for the optical implementation of the Hopfield neural network with a universal tool. The tool is a matrix grating constituted with a group of element gratings. The algorithms for designing a matrix grating are proposed, and a matrix grating is created to execute recognition experiments by use of the Hopfield neural network. The experimental results demonstrate that the proposed method performs well. The stability of the light efficiencies of different optical components used in optical networks is also considered.

  16. Stress measurements in glass by use of double thermal gratings.

    PubMed

    Cannon, B D; Shepard, C; Khaleel, M

    2001-10-20

    We developed a nondestructive and noncontact method for measuring stress at the midplane of tempered glass plates that uses Bragg scattering from a pair of thermal gratings. These gratings are formed by 1064-nm beams from a seeded Nd:YAG laser, and we measure the polarization state of light from a 532-nm beam that scatters from both thermal gratings. The change in polarization of the doubly scattered light with separation between the two gratings allows measurement of the in-plane stress. A model of the Bragg scattering efficiency, experimental investigations of the scattered beams, and stress measurements are reported.

  17. Mechanics of dielectric elastomer-activated deformable transmission grating

    NASA Astrophysics Data System (ADS)

    Wang, Yin; Zhou, Jinxiong; Sun, Wenjie; Wu, Xiaohong; Zhang, Ling

    2014-09-01

    Laminating a thin layer of elastomeric grating on the surface of a prestretched dielectric elastomer (DE) membrane forms a basic design of electrically tunable transmission grating. We analyze the inhomogeneous deformation of a circular multiple-region configuration. Variation of the geometric and material parameters, as well as of the critical condition determined by loss of tension instability, is probed to aid the design of a DE-based deformable grating. The predicted changes in the grating period agree substantially with the experimental results reported by Aschwanden et al (Aschwanden et al 2007 IEEE Photon. Technol. Lett. 19 1090).

  18. Modeling spatially localized photonic nanojets from phase diffraction gratings

    NASA Astrophysics Data System (ADS)

    Geints, Yu. E.; Zemlyanov, A. A.

    2016-04-01

    We investigated numerically the specific spatially localized intense optical structure, a photonic nanojet (PNJ), formed in the near-field scattering of optical radiation at phase diffraction gratings. The finite-difference time-domain technique was employed to study the PNJ key parameters (length, width, focal distance, and intensity) produced by diffraction gratings with the saw-tooth, rectangle, and hemispheric line profiles. Our analysis showed that each type of diffraction gratings produces a photonic jet with unique characteristics. Based on the numerical calculations, we demonstrate that the PNJ could be manipulated in a wide range through the variation of period, duty cycle, and shape of diffraction grating rulings.

  19. Talbot effect of grating with fractal rough edges

    NASA Astrophysics Data System (ADS)

    Teng, Shuyun; Cui, Yuwei; Li, Zhong

    2016-01-01

    Since the random edges of practically manufactured grating can be described by the self-affine fractal model, this paper investigates theoretically Fresnel diffraction of grating with rough edges on the basis of the self-affine fractal theory and discusses the variation of the Talbot image of grating with the rough parameters of edges. The amplitude gratings with different rough edges are produced with the help of the correlation function of the random distribution. Then, simulations of the diffraction intensity distributions of rough gratings are performed, and the modulation effect of speckles on Talbot image are shown. In order to explain the variation of the Talbot image of grating with rough edges, the theoretical analysis of the Talbot effect of grating with rough edges is given according to the statistic optics theory. The presented approximate analytic expression of the average diffraction intensity indicates the relationship between the diffraction and rough parameters of grating edges. The conclusions of this paper are useful for evaluating the Talbot image of practical grating.

  20. Increasing the field of view in grating based X-ray phase contrast imaging using stitched gratings.

    PubMed

    Meiser, J; Willner, M; Schröter, T; Hofmann, A; Rieger, J; Koch, F; Birnbacher, L; Schüttler, M; Kunka, D; Meyer, P; Faisal, A; Amberger, M; Duttenhofer, T; Weber, T; Hipp, A; Ehn, S; Walter, M; Herzen, J; Schulz, J; Pfeiffer, F; Mohr, J

    2016-03-17

    Grating based X-ray differential phase contrast imaging (DPCI) allows for high contrast imaging of materials with similar absorption characteristics. In the last years' publications, small animals or parts of the human body like breast, hand, joints or blood vessels have been studied. Larger objects could not be investigated due to the restricted field of view limited by the available grating area. In this paper, we report on a new stitching method to increase the grating area significantly: individual gratings are merged on a carrier substrate. Whereas the grating fabrication process is based on the LIGA technology (X-ray lithography and electroplating) different cutting and joining methods have been evaluated. First imaging results using a 2×2 stitched analyzer grating in a Talbot-Lau interferometer have been generated using a conventional polychromatic X-ray source. The image quality and analysis confirm the high potential of the stitching method to increase the field of view considerably.

  1. An explanation for the non-uniform grating effects during recording of diffraction gratings in photopolymers.

    PubMed

    Blaya, S; Acebal, P; Carretero, L; Murciano, A; Madrigal, R F; Fimia, A

    2010-01-18

    The recent results reported in reference 1 have produced an increased interest in explaining deviations from the ideal behavior of the energetic variation of the diffraction efficiency of holographic gratings. This ideal behavior occurs when uniform gratings are recorded, and the index modulation is proportional to the energetic exposure. As a result, a typical sin(2) curve is obtained reaching a maximum diffraction efficiency and saturation at or below this value. However, linear deviations are experimentally observed when the first maximum on the curve is lower than the second. This effect does not correspond to overmodulation and recently in PVA/acrylamide photopolymers of high thickness it has been explained by the dye concentration in the layer and the resulting molecular weight of the polymer chains generated in the polymerization process. In this work, new insights into these deviations are gained from the analysis of the non-uniform gratings recorded. Therefore, we show that deviations from the linear response can be explained by taking into account the energetic evolution of the index modulation as well as the fringe bending in the grating.

  2. Shaping Diffraction-Grating Grooves to Optimize Efficiency

    NASA Technical Reports Server (NTRS)

    Backlund, John; Wilson, Daniel; Mouroulis, Pantazis; Maker, Paul; Muller, Richard

    2008-01-01

    A method of shaping diffraction-grating grooves to optimize the spectral efficiency, spectral range, and image quality of a spectral imaging instrument is under development. The method is based on the use of an advanced design algorithm to determine the possibly complex shape of grooves needed to obtain a desired efficiency-versus-wavelength response (see figure). Then electron- beam fabrication techniques are used to realize the required groove shape. The method could be used, for example, to make the spectral efficiency of the grating in a given wavelength range proportional to the inverse of the spectral efficiency of a photodetector array so that the overall spectral efficiency of the combination of the grating and the photodetector array would be flat. The method has thus far been applied to one-dimensional gratings only, but in principle, it is also applicable to two-dimensional gratings. The algorithm involves calculations in the spatial-frequency domain. The spatial-frequency spectrum of a grating is represented as a diffraction-order spectral-peak-width function multiplied by an efficiency function for a single grating groove. This representation affords computational efficiency and accuracy by making it possible to consider only the response from one grating groove (one period of the grating), instead of from the whole grating area, in determining the response from the entire grating. This combination of efficiency and accuracy is crucial for future extensions of the algorithm to two-dimensional designs and to designs in which polarization must also be taken into account. The algorithm begins with the definition of target values of relative efficiency that represent the desired spectral response of the grating in certain spectral frequencies calculated from the diffraction order and wavelength. The grating period is divided into a number of cells - typically, 100. The phase contribution from each cell is determined from the phase of the incident

  3. Near-field diffraction of chirped gratings.

    PubMed

    Sanchez-Brea, Luis Miguel; Torcal-Milla, Francisco Jose; Morlanes, Tomas

    2016-09-01

    In this Letter, we analyze the near-field diffraction pattern produced by chirped gratings. An intuitive analytical interpretation of the generated diffraction orders is proposed. Several interesting properties of the near-field diffraction pattern can be determined, such as the period of the fringes and its visibility. Diffraction orders present different widths and also, some of them present focusing properties. The width, location, and depth of focus of the converging diffraction orders are also determined. The analytical expressions are compared to numerical simulation and experimental results, showing a high agreement.

  4. Demonstration of uniform multicore fiber Bragg gratings.

    PubMed

    Lindley, Emma; Min, Seong-Sik; Leon-Saval, Sergio; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon; Bland-Hawthorn, Joss

    2014-12-15

    Fiber Bragg gratings in multicore fibers have significant potential as compact and robust filters for research and commercial applications. With the aid of an innovative, flat-fielded Mach-Zehnder interferometer, we demonstrate deep (>30 dB) narrow (100 pm at 3 dB; 90 pm at 10 dB) notches in the outer 6 cores of a 7-core fiber at a constant wavelength ( ± 15 pm). This is a crucial step in the development of FBGs operating within multimode fibers that carry an arbitrary number of spatial modes.

  5. Metal embedded Fiber Brag Grating Sensors

    NASA Astrophysics Data System (ADS)

    Khanal, Chooda; Vargas, Garman; Balani, Kantesh; Keshri, Anup; Barbosa, Carmen; Agarwal, Arvind; Panepucci, Roberto

    2009-03-01

    A novel method of embedding optical fibers and optical fiber sensors, inside metallic structures will be discussed. We specifically report results for embedding fiber bragg grating sensors in an aluminum coating onto a steel plate. Characterization of an embedded FBG sensor and its effects on the sensor operation are also presented. Temperature sensitivity and the strain sensitivity will be discussed. The novel high throughput deposition method show the potential of embedding optical sensors onto metallic structures which make it suitable for many engineering applications in biomedical, civil, mechanical and aeronautical, among other fields.

  6. The Constellation-X Reflection Grating Spectrometer

    NASA Technical Reports Server (NTRS)

    Allen, Jean C.

    2006-01-01

    The Reflection Grating Spectrometer on the Constellation-X mission will provide high sensitivity, high-resolution spectra in the soft x-ray band. The RGS performance requirements are specified as a resolving power of greater than 300 and an effective area of greater than 1000 sq cm across most of the 0.25 to 2.0 keV band. These requirements are driven by the science goals of the mission. We will describe the performance requirements and goals, the reference design of the spectrometer, and examples of science cases where we expect data from the RGS to significantly advance our current understanding of the universe.

  7. Compact catadioptric imaging spectrometer utilizing reflective grating

    DOEpatents

    Lerner, Scott A.

    2005-12-27

    An imaging spectrometer apparatus comprising an entrance slit for directing light, a light means for receiving the light and directing the light, a grating that receives the light from the light means and defracts the light back onto the light means which focuses the light, and a detector that receives the focused light. In one embodiment the light means is a rotationally symmetric ZNSE aspheric lens. In another embodiment the light means comprises two ZNSE aspheric lenses that are coaxial. In another embodiment the light means comprises an aspheric mirror and a ZNSE aspheric lens.

  8. Fractal signatures in the aperiodic Fibonacci grating.

    PubMed

    Verma, Rupesh; Banerjee, Varsha; Senthilkumaran, Paramasivam

    2014-05-01

    The Fibonacci grating (FbG) is an archetypal example of aperiodicity and self-similarity. While aperiodicity distinguishes it from a fractal, self-similarity identifies it with a fractal. Our paper investigates the outcome of these complementary features on the FbG diffraction profile (FbGDP). We find that the FbGDP has unique characteristics (e.g., no reduction in intensity with increasing generations), in addition to fractal signatures (e.g., a non-integer fractal dimension). These make the Fibonacci architecture potentially useful in image forming devices and other emerging technologies.

  9. Interrogation of a long-period grating using a mechanically scannable arrayed waveguide grating and a sampled chirped fiber Bragg grating.

    PubMed

    Guo, Honglei; Dai, Yitang; Xiao, Gaozhi; Mrad, Nezih; Yao, Jianping

    2008-08-01

    A novel technique to interrogate a long-period grating (LPG) using a mechanically scannable arrayed waveguide grating (AWG) is proposed. This technique is implemented based on space-to-wavelength mapping by mechanically scanning the input light beam along the input coupler facet of an AWG. By employing a sampled chirped fiber Bragg grating with multiple peaks as a reference, the central wavelength of the LPG is measured. An interrogation system with a resolution of 10 pm at a speed of 10 Hz is demonstrated. Furthermore, the technique proposed can potentially offer subpicometer resolution at a speed of 500 Hz.

  10. Linear Fresnel Spectrometer Chip with Gradient Line Grating

    NASA Technical Reports Server (NTRS)

    Choi, Sang Hyouk (Inventor); Park, Yeonjoon (Inventor)

    2015-01-01

    A spectrometer that includes a grating that disperses light via Fresnel diffraction according to wavelength onto a sensing area that coincides with an optical axis plane of the grating. The sensing area detects the dispersed light and measures the light intensity associated with each wavelength of the light. Because the spectrometer utilizes Fresnel diffraction, it can be miniaturized and packaged as an integrated circuit.

  11. Pre-correction of projected gratings for surface profile measurement

    NASA Astrophysics Data System (ADS)

    Sun, Cuiru; Lu, Hua

    2008-11-01

    This paper discusses errors caused by unequal grating pitch in applying the phase-shifted digital grating projection method for object profile measurement. To address the related issues, a new scheme is proposed to effectively improve the uniformity of the projected grating pitch across the object surface with no additional hardware cost. The improvement is mainly realized via a grating pitch pre-correction algorithm assisted by Digital Speckle/Image Correlation (DSC/DIC). DIC is utilized to accurately determine the surface grating pitch variation when an originally equal-pitched grating pattern is slant projected to the surface. With the actual pitch distribution function determined, a pre-corrected grating with unequal pitch is generated and projected, and the iterative algorithm reaches a constant pitched surface grating. The mapping relationship between the object surface profile (or out-of-plane displacement) and the fringe phase changes is obtained with a real-time subtraction based calibration. A quality guide phase unwrapping method is also adopted in the fringe processing. Finally, a virtual reference phase plane obtained by a 3-point plane fitting algorithm is subtracted to eliminate the carrier phase. The study shows that a simple optical system implemented with the mentioned improvements remarkably increase the accuracy and the efficiency of the measurement.

  12. Slit and phase grating diffraction with a double crystal diffractometer

    NASA Astrophysics Data System (ADS)

    Treimer, Wolfgang; Hilger, André; Strobl, Markus

    2006-11-01

    The lateral coherence properties of a neutron beam ( λ=0.5248 nm) in a double crystal diffractometer (DCD) were studied by means of single slit diffraction and by diffraction by different perfect Silicon phase gratings. Perfect agreements were found for the lateral coherence length measured with the slit and for the one determined by Silicon phase gratings, however, some peculiarities are still present.

  13. Compact Catadioptric Imaging Spectrometer Designs Utilizing Immersed Gratings

    DOEpatents

    Lerner, Scott A.

    2006-02-28

    An imaging spectrometer comprising an entrance slit for directing light, a lens that receives said light and reflects said light, a grating that defracts said light back onto said lens which focuses said light, and a detector array that receives said focused light. In one embodiment the grating has rulings immersed into a germanium surface.

  14. Design aspects of X-ray grating interferometry

    SciTech Connect

    Weitkamp, Timm; Zanette, Irene; Pfeiffer, Franz; David, Christian

    2012-07-31

    Considerations are made for the design of X-ray grating interferometers in general and, in particular, for the case of a parallel beam with a high degree of spatial coherence. We specifically discuss the properties of different types of gratings and the interdependence of instrument parameters and performance characteristics.

  15. Scientific Objectives and Design Study of an Adaptive Optics Visual Echelle Spectrograph and Imager Coronograph (AVES-IMCO) for the NAOS Visitor Focus at the VLT

    NASA Astrophysics Data System (ADS)

    Pallavicini, Roberto; Zerbi, Filippo; Beuzit, Jean-Luc; Bonanno, Giovanni; Bonifacio, Piercarlo; Comari, Maurizio; Conconi, Paolo; Delabre, Bernard; Franchini, Mariagrazia; Marcantonio, Paolo Di; Lagrange, Anne-Marie; Mazzoleni, Ruben; Molaro, Paolo; Pasquini, Luca; Santin, Paolo

    We present the scientific case for an Adaptive Optics Visual Echelle Spectrograph and Imager Coronograph (AVES-IMCO) that we propose as a visitor instrument for the secondary port of NAOS at the VLT. We show that such an instrument would be ideal for intermediate resolution (R=16,000) spectroscopy of faint sky-limited objects down to a magnitude of V=24.0 and will complement very effectively the near-IR imaging capabilities of CONICA. We present examples of science programmes that could be carried out with such an instrument and which cannot be addressed with existing VLT instruments. We also report on the result of a two-year design study of the instrument, with specific reference to its use as parallel instrument of NAOS.

  16. The high-resolution cross-dispersed echelle white-pupil spectrometer of the McDonald Observatory 2.7-m telescope

    NASA Technical Reports Server (NTRS)

    Tull, Robert G.; Macqueen, Phillip J.; Sneden, Christopher; Lambert, David L.

    1995-01-01

    A new high-resolution cross-dispersed echelle spectrometer has been installed at the coude focus of the McDonald Observatory 2.7-m telescope. Its primary goal was simultaneously to gather spectra over as much of the spectral range 3400 A to 1 micrometer as practical, at a resolution R identical with lambda/Delta lambda which approximately = 60,000 with signal-to-noise ratio of approximately 100 for stars down to magnitude 11, using 1-h exposures. In the instrument as built, two exposures are all that are needed to cover the full range. Featuring a white-pupil design, fused silica prism cross disperser, and folded Schmidt camera with a Tektronix 2048x2048 CCD used at either of two foci, it has been in regularly scheduled operation since 1992 April. Design details and performance are described.

  17. CARMENES: Calar Alto high-resolution search for M dwarfs with exo-earths with a near-infrared Echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Quirrenbach, A.; Amado, P. J.; Mandel, H.; Caballero, J. A.; Mundt, R.; Ribas, I.; Reiners, A.; Abril, M.; Aceituno, J.; Afonso, C.; Barrado y Navascues, D.; Bean, J. L.; Béjar, V. J. S.; Becerril, S.; Böhm, A.; Cárdenas, M. C.; Claret, A.; Colomé, J.; Costillo, L. P.; Dreizler, S.; Fernández, M.; Francisco, X.; Galadí, D.; Garrido, R.; González Hernández, J. I.; Guàrdia, J.; Guenther, E. W.; Gutiérrez-Soto, F.; Joergens, V.; Hatzes, A. P.; Helmling, J.; Henning, T.; Herrero, E.; Kürster, M.; Laun, W.; Lenzen, R.; Mall, U.; Martin, E. L.; Martín-Ruiz, S.; Mirabet, E.; Montes, D.; Morales, J. C.; Morales Muñoz, R.; Moya, A.; Naranjo, V.; Rabaza, O.; Ramón, A.; Rebolo, R.; Reffert, S.; Rodler, F.; Rodríguez, E.; Rodríguez Trinidad, A.; Rohloff, R. R.; Sánchez Carrasco, M. A.; Schmidt, C.; Seifert, W.; Setiawan, J.; Solano, E.; Stahl, O.; Storz, C.; Suárez, J. C.; Thiele, U.; Wagner, K.; Wiedemann, G.; Zapatero Osorio, M. R.; del Burgo, C.; Sánchez-Blanco, E.; Xu, W.

    2010-07-01

    CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument to be built for the 3.5m telescope at the Calar Alto Observatory by a consortium of Spanish and German institutions. Conducting a five-year exoplanet survey targeting ~ 300 M stars with the completed instrument is an integral part of the project. The CARMENES instrument consists of two separate spectrographs covering the wavelength range from 0.52 to 1.7 μm at a spectral resolution of R = 85, 000, fed by fibers from the Cassegrain focus of the telescope. The spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a 1m/s radial velocity precision employing a simultaneous ThAr calibration.

  18. Grating image with desired shaped dots

    NASA Astrophysics Data System (ADS)

    Honma, Hideaki; Toda, Toshiki; Takahashi, Susumu; Sawamura, Chikara; Iwata, Fujio

    2000-03-01

    A new type of Grating Image we dominate as `Sparklegram' is presented. The Sparklegram is characterized because it provides high quality and better design flexibility. These features are achieved by constructing it with shaped dots as desired. Each dot can be designed as an individual shape, for example, a star or a triangle. As dot shapes, we can use not only geometric patterns, but also some kind of symbols. Not only flexibility of each consists dot shape, but also the quality of reconstructed image is remarkably increased too. Because of these features, the constructed image with the new type of Grating Image, Sparklegram has high quality and high flexibility. It can be applied to security use, for example on credit-cards, tickets, etc., and also can be applied to the package of software products, CDs, videos and other kind of items requiring security. And with these features of flexibility and high quality, Sparklegram has also advantages to be applied to other use, for example amusement use, comics and game characters' goods and packages.

  19. Optical fiber Bragg gratings for tunnel surveillance

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Frank, Andreas; Broennimann, Rolf; Sennhauser, Urs J.

    2000-06-01

    We report on application tests of novel sensor elements for long term surveillance of tunnels. The sensors are made of glass fiber reinforced polymers (GFRP) with embedded optical fiber Bragg gratings. The tests were made in a tunnel near Sargans in Switzerland and we will present strain and temperature data of more than one year of operation of the sensor elements. Two sensor types were tested. First, GFRP rockbolts with a diameter of 22 mm were produced. They have a load-bearing function as anchors for tunnel or mine roofs and in addition measure distributed strain fields and temperature with embedded optical fiber Bragg grating arrays. Rockbolts are key elements during construction and operation of tunnels. Data about strain inside the rockbolts can support decision about precautions to be taken and reveal information about the long term movement of the rock. Second, thin and flexible GFRP wires of 3 mm in diameter were found to be robust and versatile sensors not only for tunnel surveillance but for many civil engineering applications where they can be attached or embedded (e.g., in concrete). The fabrication of both sensor types and solutions for the connection of the embedded fiber sensors to a fiber cable will be presented. Moreover, laboratory and tunnel data of functionality and long term stability tests will be discussed and compared.

  20. Photoelectrochemical fabrication of spectroscopic diffraction gratings

    NASA Technical Reports Server (NTRS)

    Rauh, R. David; Carrabba, Michael M.; Nguyen, Nguyet M.

    1986-01-01

    Photoelectrochemical etching was demonstrated as a means of fabricating a variety of periodic structures in semiconductors. The semiconductor is used as an electrode in an electrochemical cell, and is in contact with a liquid electrolyte. When the crystal is held at a positive voltage and illuminated, etching occurs in only the illuminated regions to a depth proportional to the illumination intensity and exposure time. In Phase 1, it was determined that diffraction gratings could be produced in gallium arsenide crystals by this method, using either a scanned focused laser beam or by uniform illumination of a ruling mask defined in metal or photoresist on the crystal surface. The latter approach was determined to produce V-grooves if the mask is oriented along certain crystallographic directions. These V-grooves were produced with an exceedingly smooth crystal morphology due to the highly controllable nature of the process and the mild electrolytes involved. The results form the basis for photoelectrochemical fabrication of deep, low pitch Eschelle gratings for use in high orders in NASA spectrographic instrumentation such as the Space Telescope Imaging Spectrograph.

  1. Writing Bragg Gratings in Multicore Fibers.

    PubMed

    Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

    2016-04-20

    Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

  2. Optimization of direct-write polarization gratings

    NASA Astrophysics Data System (ADS)

    Miskiewicz, Matthew N.; Escuti, Michael J.

    2015-02-01

    We recently reported on a mathematical formalism for analyzing the result of a direct-write scanning system applied to photoaligned liquid crystal films. We use that formalism to study the direct-write recording of polarization gratings (PGs). First, we evaluate three scan paths in simulation and experiment, describe their tradeoffs and practical constraints, and identify the most favorable. Second, we explore the parameter space of direct-write PGs in simulation, which includes four dimensions in general: grating period, line spacing, beam size, and spatially averaged fluence. Using this analysis, we predict that a certain portion of the parameter space should be optimal, leading to high diffraction efficiency and well-aligned PGs. Finally, we experimentally fabricate and characterize nine PGs with scan parameters within and around this optimal parameter space and conclude that the prediction is validated. This work is the first in-depth study of direct-write PGs; it identifies many challenges and solutions, and shows, for the first time, direct-write recorded PGs with quality equivalent to those recorded via holography. In particular, we demonstrate a PG (20 μm period) with first-order diffraction efficiency 99.5%, 0.2% haze, and polarization contrast of 2000.

  3. Surface plasmon amplification and active nonreciprocal gratings

    NASA Astrophysics Data System (ADS)

    Karami Keshmarzi, Elham; Tait, R. Niall; Berini, Pierre

    2015-03-01

    In this paper, we review our recent work on active plasmonic structures composed of optically pumped dye molecules infiltrated in a polymer host as the cladding of long-range surface plasmon polariton (LRSPP) structures. In particular, concepts for distributed Bragg and distributed feedback (DBR/DFB) lasers, and a spatially non-reciprocal Bragg grating (NRBG) are reviewed. The LRSPP Bragg grating is a fundamental element in these devices which is created by stepping the width of a metal stripe to produce modulation of refractive index. The gain medium in all of these active devices is assumed to be a thin film (~1μm) of polymer (poly (methyl methacrylate)) doped with organic laser dye molecules IR- 140. The gain medium is assumed pumped optically through the top of the devices via 10 ns laser pulses at 810 nm with 500 kW/cm2 power intensity to enable stimulated emission at 880 nm. The maximum material gain coefficient of this medium was measured independently as 68 cm-1.

  4. Holographic dielectric grating: theory and practice.

    PubMed

    Chang, M; George, N

    1970-03-01

    Lossy dielectric gratings have been analyzed using a Raman-Nath formalism modified to incorporate losses. Four second-order coupled wave equations are retained for computation of the zero, first- and second-order diffracted beams for a multitude of practical cases. Significant differences are found in comparison with computations in which only two coupled waves are retained. The entire range of losses and thicknesses encountered for holograms in film emulsions has been studied using this unified approach. Graphs have been prepared to show the efficiency, i.e., power diffracted in the first-order relative to the total incident power, vs the index modulation for a wide range of thicknesses and losses. At a given thickness, optimum frequency requires a specific exposure. The efficiency for an optimum exposure is plotted vs the loss factor with thickness as a parameter. New experimental data are presented for bleached gratings in which several diffracted orders are measured and compared to our theory for a wide range of index modulation and loss factors.

  5. Plasmonic band gap cavities on biharmonic gratings

    NASA Astrophysics Data System (ADS)

    Kocabas, Askin; Seckin Senlik, S.; Aydinli, Atilla

    2008-05-01

    In this paper, we have experimentally demonstrated the formation of plasmonic band gap cavities in infrared and visible wavelength range. The cavity structure is based on a biharmonic metallic grating with selective high dielectric loading. A uniform metallic grating structure enables strong surface plasmon polariton (SPP) excitation and a superimposed second harmonic component forms a band gap for the propagating SPPs. We show that a high dielectric superstructure can dramatically perturb the optical properties of SPPs and enables the control of the plasmonic band gap structure. Selective patterning of the high index superstructure results in an index contrast in and outside the patterned region that forms a cavity. This allows us to excite the SPPs that localize inside the cavity at specific wavelengths, satisfying the cavity resonance condition. Experimentally, we observe the formation of a localized state in the band gap and measure the dispersion diagram. Quality factors as high as 37 have been observed in the infrared wavelength. The simplicity of the fabrication and the method of testing make this approach attractive for applications requiring localization of propagating SPPs.

  6. IUVS echelle-mode observations of interplanetary hydrogen: Standard for calibration and reference for cavity variations between Earth and Mars during MAVEN cruise

    NASA Astrophysics Data System (ADS)

    Mayyasi, Majd; Clarke, John; Quémerais, Eric; Katushkina, Olga; Bhattacharyya, Dolon; Chaufray, Jean-Yves; Bertaux, Jean-Loup; McClintock, Bill; Stewart, Ian; Holsclaw, Greg; Deighan, Justin; Chaffin, Michael; Schneider, Nick; Jakosky, Bruce

    2017-02-01

    The high-resolution echelle mode of the Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile Evolution mission has been designed to measure D and H Lyman α emissions from the Martian atmosphere to obtain key information about the physical processes by which water escapes into space. Toward this goal, the absolute calibration of the instrument is critical for determining the D and H densities, the D/H ratio, and the escape flux of water. The instrument made observations of interplanetary hydrogen (IPH) along multiple look directions and conducted several postlaunch calibration campaigns during cruise as well as during orbit around Mars. The calibration efforts monitored instrument degradation and produced a consistent calibration factor at the hydrogen Lyman α wavelength (121.567 nm). The instrument was calibrated with the diffuse emission of interplanetary hydrogen (IPH) as a standard candle using measurements and model results from the Solar Wind Anisotropies (SWAN) instrument. Validation of the calibrated instrument was made by (1) comparisons to simultaneous observations of the IPH made with the lower resolution FUV mode of the IUVS instrument that were independently calibrated by using standard stars and by (2) comparisons to same-day observations of Mars at hydrogen Lyman α made with the Hubble Space Telescope that were calculated with a radiative transfer model. Adopted FUV mode values and Hubble Space Telescope-based model results agreed with the echelle SWAN calibrated values to within 6% and 4%, respectively. The calibrated IUVS instrument can be used to interpret emissions of atmospheric species at Mars for insights into water evolution at the planet, as well as observed IPH measurements made during cruise for further insights into dynamics of the inner heliosphere.

  7. Very Large Telescope deep echelle spectroscopy of Galactic planetary nebulae NGC 6153, M 1-42 and Hf 2-2

    NASA Astrophysics Data System (ADS)

    McNabb, I. A.; Fang, X.; Liu, X.-W.

    2016-09-01

    We present deep spectroscopy of three Galactic planetary nebulae (PNe) with large abundance discrepancy factors: NGC 6153, M 1-42 and Hf 2-2. The spectra were obtained with Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph and cover the whole optical range (3040-11 000 Å) with a spectral resolution of ˜20 000. For all three PNe, several hundred emission lines were detected and identified, with more than 70 per cent of them as permitted lines. Most of these permitted lines are excited by recombination. Numerous weak optical recombination lines (ORLs) of O II, C II, N II and Ne II were detected in the spectra and accurate fluxes measured. Line flux tables were compiled and ready for use by the community of nebular astrophysics. These ORLs were critically analysed using the effective recombination coefficients recently calculated for the optical recombination spectrum of N II and O II under the physical conditions of photoionized gaseous nebulae. Plasma diagnostics based on the heavy element ORLs were carried out using the new atomic data. Elemental abundances derived from the ORLs were systematically higher than those derived from the collisionally excited lines (CELs) by a factor of ˜11, 22 and 80 for NGC 6153, M 1-42 and Hf 2-2, respectively. The electron temperatures derived from the heavy element ORLs are systematically lower than those derived from the CELs. These ORL versus CEL abundance and temperature discrepancies, previously observed in the three PNe through deep spectroscopy with medium to low spectral resolution, are thus confirmed by our analysis of the deep echelle spectra using the new atomic data.

  8. Approaching perfection in the manufacturing of silicon immersion gratings

    NASA Astrophysics Data System (ADS)

    Kidder, Benjamin T.; Brooks, Cynthia B.; Grigas, Michelle M.; Jaffe, Daniel T.

    2016-07-01

    Silicon immersion gratings make near-IR spectrographs compact and allow them to have continuous wavelength coverage over a large bandwidth. We have produced an exceptional silicon immersion grating that approaches optical perfection in terms of surface error. This grating has a peak-to-valley error of 79 nm over a 25 mm beam, which exceeds the 85 nm requirement to have λ/4 peak-to-valley error at the shortest wavelength where silicon immersion gratings can be used. In order to reduce the level of large-scale errors we have honed our contact printing method by optimizing our UV exposure system, introducing additional process checks and inspections and carefully evaluating large-scale errors in the gratings produced.

  9. Electronic speckle pattern shearing interferometer using holographic gratings

    NASA Astrophysics Data System (ADS)

    Joenathan, Charles; Buerkle, L.

    1997-09-01

    We propose two methods to perform shearing in electronic speckle patten shearing interferometry (ESPSI). These new methods of shearing make the setup compact and easy to align. The first system we propose consists of two parts: (1) the object is imaged onto an intermediate ground glass and (2) the image on the ground glass is in turn imaged onto the photosensor of a CCD camera. A holographic grating placed in front of the ground glass screen is used to shear the two images and to introduce phase stepping. The separation between the grating and the ground glass plate is used to control shearing. In the second method, two identical holographic gratings separated by a distance introduce shearing and the distance between two gratings can be used to control the size of shearing. Phase shifts to be employed for phase measurements are introduced by displacing the grating.

  10. Near-field diffraction of gratings with surface defects.

    PubMed

    Sanchez-Brea, Luis Miguel; Torcal-Milla, Francisco Jose

    2010-04-10

    Diffraction gratings produce self-images in the near field. Defects on the surface of the grating may occur due to the manufacturing process. These devices are often placed in dirty industrial environments. Dust particles or drops of liquid can be deposited over their surface. In this work, we analyze the effect of surface defects placed over the grating on the self-imaging process. We analytically show how the self-images gradually recover as we separate from the grating when one defect is present. Also a random distribution of surface defects over the grating is analyzed. In particular, we focus on how the contrast of the self-images decreases in terms of the density of the defects. Analytical expressions for the near field are derived, considering a stochastic description of the spatial distribution of defects. In addition, numerical simulations based on the Rayleigh-Sommerfeld formulation are performed to validate the analytical results.

  11. Electromagnetically induced two-dimensional grating assisted by incoherent pump

    NASA Astrophysics Data System (ADS)

    Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang

    2017-04-01

    We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication.

  12. Tunable resonance-domain diffraction gratings based on electrostrictive polymers.

    PubMed

    Axelrod, Ramon; Shacham-Diamand, Yosi; Golub, Michael A

    2017-03-01

    Critical combination of high diffraction efficiency and large diffraction angles can be delivered by resonance-domain diffractive optics with high aspect ratio and wavelength-scale grating periods. To advance from static to electrically tunable resonance-domain diffraction grating, we resorted to its replication onto 2-5 μm thick P(VDF-TrFE-CFE) electrostrictive ter-polymer membranes. Electromechanical and optical computer simulations provided higher than 90% diffraction efficiency, a large continuous deflection range exceeding 20°, and capabilities for adiabatic spatial modulation of the grating period and slant. A prototype of the tunable resonance-domain diffraction grating was fabricated in a soft-stamp thermal nanoimprinting process, characterized, optically tested, and provided experimental feasibility proof for the tunable sub-micron-period gratings on electrostrictive polymers.

  13. Asymmetric dynamic phase holographic grating in nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Ren, Chang-Yu; Shi, Hong-Xin; Ai, Yan-Bao; Yin, Xiang-Bao; Wang, Feng; Ding, Hong-Wei

    2016-09-01

    A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal (NLC) was presented. An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating. The diffraction efficiency we achieved is more than 40%, exceeding the theoretical limit for symmetric profile gratings. Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC. Finally, physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented, based on the photo-refractive-like (PR-like) effect. Project supported by the Science and Technology Programs of the Educational Committee of Heilongjiang Province, China (Grant No. 12541730) and the National Natural Science Foundation of China (Grant No. 61405057).

  14. Polarization sensitivity testing of off-plane reflection gratings

    NASA Astrophysics Data System (ADS)

    Marlowe, Hannah; McEntaffer, Randal L.; DeRoo, Casey T.; Miles, Drew M.; Tutt, James H.; Laubis, Christian; Soltwisch, Victor

    2015-09-01

    Off-Plane reflection gratings were previously predicted to have different efficiencies when the incident light is polarized in the transverse-magnetic (TM) versus transverse-electric (TE) orientations with respect to the grating grooves. However, more recent theoretical calculations which rigorously account for finitely conducting, rather than perfectly conducting, grating materials no longer predict significant polarization sensitivity. We present the first empirical results for radially ruled, laminar groove profile gratings in the off-plane mount which demonstrate no difference in TM versus TE efficiency across our entire 300-1500 eV bandpass. These measurements together with the recent theoretical results confirm that grazing incidence off-plane reflection gratings using real, not perfectly conducting, materials are not polarization sensitive.

  15. Specification of multiple image characteristics viewed through a grating

    NASA Astrophysics Data System (ADS)

    Abolhassani, Mohammad

    2016-11-01

    When a person observes an object, illuminated incoherently by a quasi-monochromatic source, through a grating, he will see more than one image. Angular positions of these images are derived in terms of wavelength, period of the grating, separation between the object and the grating, and position of the object relative to the observer. In a special case, when the object is another grating, the condition of coincidence of its multiple images is investigated. The relation derived is, to some extent, similar to that seen in the Lau effect. As a secondary outcome, it is shown that the sum of the squared modulus of the odd Fourier series coefficients for a binary grating function is equal to that of the even coefficients.

  16. Lamellar multilayer gratings with very high diffraction efficiency

    SciTech Connect

    Martynov, V.V. |; Yakshin, A.; Agafonov, Yu.A.; Padmore, H.A.

    1997-07-01

    The authors report here the development of a hard x-ray multilayer grating that has achieved an absolute efficiency of 34% at a wavelength of 1.54{angstrom}. The W-C multilayer itself has a reflectivity of 57% and the grating has a 0th order absolute efficiency of 36%. The origin of this extraordinarily high efficiency is that the short period and highly asymmetric structure of the gratings combined with its deep grooves allows light to interact with a large number of layer pairs. This increases angular separation of the diffraction orders and reduces the multilayer bandwidth to the point where there is little or no order to order overlap in the grating structure, and hence maximum intensity can be diffracted into a selected order. This paper reports on the development of an optimized multilayer grating and some of its unique characteristics.

  17. Holographic gratings in hybrid sol-gel films

    NASA Astrophysics Data System (ADS)

    Raschella, R.; Marino, I.-G.; Lottici, P. P.; Bersani, D.; Lorenzi, A.; Montenero, A.

    2003-08-01

    Organic-inorganic films based on SiO2, containing Disperse Red 1 (DR1), carbazole units and 2,4,7-trinitro-9-fluorenone (TNF), have been prepared by a sol-gel technique. Diffraction gratings have been produced through different effects: photoinduced birefringence and photorefractivity, using 488.0 nm and 632.8 nm light, respectively. Pure polarization holographic birefringence gratings have been investigated and diffraction efficiencies higher than those obtained by light intensity modulation have been measured. The study of the temporal behavior of the diffraction efficiencies makes possible the identification of different processes involved in the DR1 molecular orientation: angular hole burning (AHB), angular redistribution (AR), Cis molecules gain has been determined by two-beam coupling (2BC) measurements. The effect of the polarization of the writing beams on the grating and of a circularly polarized photoisomerizing radiation during grating erasure has been interpreted in terms of an orientation contribution to the grating formation.

  18. Study on spectrometer based upon volume holographic transmission grating

    NASA Astrophysics Data System (ADS)

    Huang, Zhen; Liu, Guodong; Ren, Zhong; Zeng, Lvming

    2010-10-01

    In this present paper, a spectrometer based upon axial transmissive optical structure with the volume-phase holographic (VPH) transmission grating technology is introduced. We give a physical insight for the structure and mechanism of photorefractive volume holographic gratings and theoretically analyze some important performance parameters of the spectrometer device using the coupled wave theory, which should be considered in the process of the following design for the device with volume phase holographic transmission gratings. The experimental results show, owing to its axial transmissive optical geometry and the perfect performance of the VPH transmission grating, the spectrometer based on the volume-phase holographic transmission grating has satisfactory high resolution and wavelength accuracy. It has great promise to be widely used in the future.

  19. Coherent grating x-ray diffraction (CGXD) and its applications

    SciTech Connect

    Shen, Q.

    1996-09-01

    We show that an x-ray interference phenomenon, coherent grating x-ray diffraction (CGXD), can be used to study lateral nanostructure arrays on crystal surfaces and interfaces. Compared to Fraunhofer grating diffraction of visible light, x-ray grating diffraction contains information not only about geometric profiles of the surface but also about the internal crystalline structures and lattice strain distributions in the grating features. The grating diffraction pattern can also be measured in a white-beam Laue method using highly collimated polychromatic synchrotron radiation, which provides a parallel data collection scheme and may be useful in {ital in} {ital situ} studies on evolution of nanostructure arrays. {copyright} {ital 1996 American Institute of Physics.}

  20. Discrete dipole approximation simulation of bead enhanced diffraction grating biosensor

    NASA Astrophysics Data System (ADS)

    Arif, Khalid Mahmood

    2016-08-01

    We present the discrete dipole approximation simulation of light scattering from bead enhanced diffraction biosensor and report the effect of bead material, number of beads forming the grating and spatial randomness on the diffraction intensities of 1st and 0th orders. The dipole models of gratings are formed by volume slicing and image processing while the spatial locations of the beads on the substrate surface are randomly computed using discrete probability distribution. The effect of beads reduction on far-field scattering of 632.8 nm incident field, from fully occupied gratings to very coarse gratings, is studied for various bead materials. Our findings give insight into many difficult or experimentally impossible aspects of this genre of biosensors and establish that bead enhanced grating may be used for rapid and precise detection of small amounts of biomolecules. The results of simulations also show excellent qualitative similarities with experimental observations.

  1. Excitation of a surface plasmon with an elastomeric grating

    NASA Astrophysics Data System (ADS)

    Kocabas, A.; Dâna, A.; Aydinli, A.

    2006-07-01

    We report on a new method to excite surface plasmon polaritons on a thin metal slab surface using an elastomeric grating which is fabricated by replica molding technique. The grating is placed on the metal surface which creates a periodic perturbation on the surface matching the momentum of the incident light to that of the surface plasmon. The conformal contact between the metal surface and the elastomeric grating changes the dielectric medium periodically and allows the observation of an effective surface plasmon polariton at the metal-air and metal-polymer interfaces of the grating. To clarify the nature of the observed plasmon, comparison of the elastomeric grating with elastomeric slabs was performed with the attenuated total reflection method.

  2. Resonant diffraction gratings for spatial differentiation of optical beams

    SciTech Connect

    Golovastikov, N V; Bykov, D A; Doskolovich, L L

    2014-10-31

    Diffraction of a two-dimensional optical beam from a resonant diffraction grating is considered. It is shown that at certain resonance parameters the diffraction grating allows for spatial differentiation and integration of the incident beam. The parameters of the diffraction grating for spatial differentiation of optical beams in the transmission geometry are calculated. It is shown that the differentiating diffraction grating allows the conversion of the two-dimensional beam into the two-dimensional Hermite – Gaussian mode. The presented results of numerical modelling are in good agreement with the proposed theoretical description. The use of the considered resonant diffraction gratings is promising for solving the problems of all-optical data processing. (laser applications and other topics in quantum electronics)

  3. Temperature-insensitive arrayed waveguide grating demodulation technique for fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Li, Hongqiang; Li, Yang; Li, Enbang; Dong, Xiaye; Bai, Yaoting; Liu, Yu; Zhou, Wenqian

    2013-10-01

    As the output characteristics of arrayed waveguide grating (AWG) can be affected by temperature, the output spectrum central wavelength λi of every channel has a tendency to drift with the temperature. To improve demodulation accuracy, this paper presents a type of AWG demodulation algorithm with temperature compensation. This algorithm assumes that under the same environment, with similarly changing temperatures of AWG and fiber Bragg grating (FBG), the AWG central wavelength is replaced with the expression that includes ΔT, and the values of AWG and of FBG which change with the temperature (ΔT) are integrated. The experiment result shows that when temperature compensation is added in the demodulation technique, the correlation coefficient r of the demodulation result is 0.997, which means that the curve has good consistency and can be measured repeatedly. This also proves the rightness of the technique. The application of this technique for smart clothing is mentioned, which indicates its feasibility.

  4. High-resolution diffraction grating interferometric transducer of linear displacements

    NASA Astrophysics Data System (ADS)

    Shang, Ping; Xia, Haojie; Fei, Yetai

    2016-01-01

    A high-resolution transducer of linear displacements is presented. The system is based on semiconductor laser illumination and a diffraction grating applied as a length master. The theory of the optical method is formulated using Doppler description. The relationship model among the interference strips, measurement errors, grating deflection around the X, Y and Z axes and translation along the Z axis is built. The grating interference strips' direction and space is not changed with movement along the X (direction of grating movement), Y (direction of grating line), Z axis, and the direction and space has a great effect when rotating around the X axis. Moreover the space is little affected by deflection around the Z axis however the direction is changed dramatically. In addition, the strips' position shifted rightward or downwards respectively for deflection around the X or Y axis. Because the emitted beams are separated on the grating plane, the tilt around the X axis error of the stage during motion will lead to the optical path difference of the two beams resulting in phase shift. This study investigates the influence of the tilt around the X axis error. Experiments show that after yaw error compensation, the high-resolution diffraction grating interferometric transducer readings can be significantly improved. The error can be reduced from +/-80 nm to +/-30 nm in maximum.

  5. Improve the diffraction efficiency of the multilayer dielectric gratings

    NASA Astrophysics Data System (ADS)

    Muhutijiang, Bilali; Qiu, Keqiang; Yusufu, Taximaiti

    2016-10-01

    The chirped-pulse amplification system plays a critical role in the process of achieving high-peak ultrashort pulses. Chirped-pulse amplification technology performance mainly depends on the pulse compression gratings. Diffraction efficiency is the critical parameter of the pulse compression gratings, and optimization of grating shape can achieve higher diffraction efficiency. If the photoresist grating mask bottom is not clean, the side walls would not be steep and duty cycle would be too big or too small, thus pulse compression grating diffraction efficiency would decrease. Solving these problems is the key to improve the diffraction efficiency. In this paper, oxygen etching methods are used to reduce the photoresist mask duty cycle, and PDMS pressing method is used to increase the duty cycle of photoresist mask, and aperture up to 100 mm×100 mm. Best photoresist grating mask parameter could be obtained by effectively combining the above two methods. Based on above techniques, a number of pulse compression gratings with line densities of 1740 lines/mm was achieved. The diffraction efficiency at the-1st order was greater than 99% for TE polarized light. A qualitative judgments for graphic transfer of ion beam etching is received through the picture before and after etching which is get from the SEM. These experimental results proved the accuracy, stability, and success rates of the technique.

  6. High efficiency diffraction grating for EUV lithography beamline monochromator

    NASA Astrophysics Data System (ADS)

    Voronov, D. L.; Warwick, T.; Gullikson, E. M.; Salmassi, F.; Naulleau, P.; Artemiev, N. A.; Lum, P.; Padmore, H. A.

    2016-09-01

    A blazed diffraction grating for the EUV lithography Beamline 12.0.1 of the Advanced Light Source has been fabricated using optical direct write lithography and anisotropic wet etching technology. A variable line spacing pattern was recorded on a photoresist layer and transferred to a hard mask layer of the grating substrate by a plasma etch. Then anisotropic wet etching was applied to shape triangular grating grooves with precise control of the ultralow blaze angle. Variation of the groove density along the grating length was measured with a Long Trace Profiler (LTP). Fourier analysis of the LTP data confirmed high groove placement accuracy of the grating. The grating coated with a Ru coating demonstrated diffraction efficiency of 69.6% in the negative first diffraction order which is close to theoretical efficiency at the wavelength of 13.5 nm. This work demonstrates an alternative approach to fabrication of highly efficient and precise x-ray diffraction gratings with ultra-low blaze angles.

  7. Suppressing Ghost Diffraction in E-Beam-Written Gratings

    NASA Technical Reports Server (NTRS)

    Wilson, Daniel; Backlund, Johan

    2009-01-01

    A modified scheme for electron-beam (E-beam) writing used in the fabrication of convex or concave diffraction gratings makes it possible to suppress the ghost diffraction heretofore exhibited by such gratings. Ghost diffraction is a spurious component of diffraction caused by a spurious component of grating periodicity as described below. The ghost diffraction orders appear between the main diffraction orders and are typically more intense than is the diffuse scattering from the grating. At such high intensity, ghost diffraction is the dominant source of degradation of grating performance. The pattern of a convex or concave grating is established by electron-beam writing in a resist material coating a substrate that has the desired convex or concave shape. Unfortunately, as a result of the characteristics of electrostatic deflectors used to control the electron beam, it is possible to expose only a small field - typically between 0.5 and 1.0 mm wide - at a given fixed position of the electron gun relative to the substrate. To make a grating larger than the field size, it is necessary to move the substrate to make it possible to write fields centered at different positions, so that the larger area is synthesized by "stitching" the exposed fields.

  8. Fork gratings based on ferroelectric liquid crystals.

    PubMed

    Ma, Y; Wei, B Y; Shi, L Y; Srivastava, A K; Chigrinov, V G; Kwok, H-S; Hu, W; Lu, Y Q

    2016-03-21

    In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices.

  9. Metal-coated Bragg grating reflecting fibre

    NASA Astrophysics Data System (ADS)

    Chamorovskiy, Yu. K.; Butov, O. V.; Kolosovskiy, A. O.; Popov, S. M.; Voloshin, V. V.; Vorob'ev, I. L.; Vyatkin, M. Yu.

    2017-03-01

    High-temperature optical fibres (OF) with fibre Bragg gratings (FBG) arrays written over a long length and in-line metal coating have been made for the first time. The optical parameters of the FBG arrays were tested by the optical frequency domain reflectometer (OFDR) method in a wide temperature range, demonstrating no degradation in reflection at heating up to 600 °C for a fibre with Al coating. The mechanical strength of the developed fibre was practically the same as "ordinary" OF with similar coating, showing the absence of the influence of FBG writing process on fibre strength. Further experiments are necessary to evaluate the possibility of further increases in the operational temperature range.

  10. Torque transducer based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Li, Tao; Jiang, Shu; Li, Jiang; Lin, Jiejun; Qi, Hongli

    2016-11-01

    In order to obtain the accurate torque measurements in harsh condition, such as marine environment, a torque transducer based on fiber Bragg grating is proposed in this paper. According to its optimized elastomer design and fiber Bragg grati ng patching tactics, the new proposed torque transducer realizes automatic compensations of temperature and bending moment which avoids influences from environment. The accuracy and stability of the torquetransducer, as well as its under water performance are tested by loading tests both in air and in underwater environment, which indicate the designed tor que transducer is not only able to realize highaccurate and robust measurements, but also can be applied in torque sensing in harsh environment. We believe the proposed design detailed illustrated in this paper provides important reference for studies and applications on torque measurements in marine environment.

  11. Nano-Fabricated Gratings for Electrons

    NASA Astrophysics Data System (ADS)

    Gronniger, Glen; Savas, Tim; Batelaan, Herman

    2005-05-01

    We explore the lower energy range for electron diffraction from a Au and Pd coated nano-fabricated transmission grating. This has the promise of providing a route to the lowest energy electron interferometer currently possible. Starting at 1000 eV we get well resolved diffraction peaks. As 60 eV electron energy is approached the diffraction peaks broaden to the extent that they are hard to resolve. We attribute this to an effective loss of transverse coherence length. We show that the broadening and coherence loss can be modeled with a path integral calculation where the essential ingredient is a random spatially varying potential with a typical length scale of 200 nm. The effect of other coatings, such as Ni, is investigated and indicates that lower electron energies can be reached. Work supported by NSF, DOD-EPSCoR.

  12. Periodic waves in fiber Bragg gratings

    SciTech Connect

    Chow, K. W.; Merhasin, Ilya M.; Malomed, Boris A.; Nakkeeran, K.; Senthilnathan, K.; Wai, P. K. A.

    2008-02-15

    We construct two families of exact periodic solutions to the standard model of fiber Bragg grating (FBG) with Kerr nonlinearity. The solutions are named ''sn'' and ''cn'' waves, according to the elliptic functions used in their analytical representation. The sn wave exists only inside the FBG's spectral bandgap, while waves of the cn type may only exist at negative frequencies ({omega}<0), both inside and outside the bandgap. In the long-wave limit, the sn and cn families recover, respectively, the ordinary gap solitons, and (unstable) antidark and dark solitons. Stability of the periodic solutions is checked by direct numerical simulations and, in the case of the sn family, also through the calculation of instability growth rates for small perturbations. Although, rigorously speaking, all periodic solutions are unstable, a subfamily of practically stable sn waves, with a sufficiently large spatial period and {omega}>0, is identified. However, the sn waves with {omega}<0, as well as all cn solutions, are strongly unstable.

  13. Ripplon scattering using grating heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Sirohi, R. S.; Edwards, R. V.; Mann, J. A., Jr.

    1980-01-01

    Heterodyne photon spectroscopy was used for the study of the viseo-elastic properties of the liquid interface by studying the scattering from thermal ripplons. A theory of a heterodyne apparatus based on a grating is presented, and the heterodyne condition is given in terms of the parameters of the experimental set-up. Emphasis was placed on the study of the instrumental function and its influence on the measurement data. The instrumental function is not always gaussian, but its functional form depends on the parameters of the experimental set-up. An algorithm is suggested to arrive at the center frequency and half width at half height of the spectrum from the noisy experimental data, and applied to the measurement data obtained from ethanol and water surfaces.

  14. Grating-based tomography of human tissues

    NASA Astrophysics Data System (ADS)

    Müller, Bert; Schulz, Georg; Mehlin, Andrea; Herzen, Julia; Lang, Sabrina; Holme, Margaret; Zanette, Irene; Hieber, Simone; Deyhle, Hans; Beckmann, Felix; Pfeiffer, Franz; Weitkamp, Timm

    2012-07-01

    The development of therapies to improve our health requires a detailed knowledge on the anatomy of soft tissues from the human body down to the cellular level. Grating-based phase contrast micro computed tomography using synchrotron radiation provides a sensitivity, which allows visualizing micrometer size anatomical features in soft tissue without applying any contrast agent. We show phase contrast tomography data of human brain, tumor vessels and constricted arteries from the beamline ID 19 (ESRF) and urethral tissue from the beamline W2 (HASYLAB/DESY) with micrometer resolution. Here, we demonstrate that anatomical features can be identified within brain tissue as well known from histology. Using human urethral tissue, the application of two photon energies is compared. Tumor vessels thicker than 20 μm can be perfectly segmented. The morphology of coronary arteries can be better extracted in formalin than after paraffin embedding.

  15. Aries x ray objective grating spectrograph

    NASA Technical Reports Server (NTRS)

    Catura, R. C.

    1991-01-01

    This investigation was initiated in June of 1983. An Aries payload involving a single Wolter 1 telescope was developed and flown under a previous contract and the objective of this work was to add two additional mirrors, nested inside of the then existing mirror and add 12 objective reflection gratings to convert the telescope into a spectrograph. A summary of major milestones in the investigation are given. Results of efforts under this contract prior to 1987 are presented in the form of four reprints of published papers attached to this report. Results of the gamma-ray research are also included in the form of an attached reprint. A summary of other work under the contract since 1987 is given.

  16. Large Scale Interconnections Using Dynamic Gratings

    NASA Astrophysics Data System (ADS)

    Pauliat, Gilles; Roosen, Gerald

    1987-01-01

    Optics is attractive for interconnects because the possibility of crossing without any interaction multiple light beams. A crossbar network can be achieved using holographic elements which permit to connect independently all inputs and all outputs. The incorporation of dynamic holographic materials is enticing as this will render the interconnection changeable. However, it is necessary to find first a passive method permitting to achieve beam deflection and secondly a photosensitive material of high optical quality requiring low power levels to optically induce the refractive index changes. We first describe an optical method allowing to produce very large deflections of light beams thus enabling to randomly address any spot on a plane. Such a technique appears applicable to both interconnections of VLSI chips and random access of optical memories. Our scheme for realizing dynamic optical interconnects is based on Bragg diffraction of the beam to steer by a dynamic phase grating which spacing and orientation are changeable in real time. This is achieved in a passive way by acting on the optical frequency of the control beams used to record the dynamic grating. Deflection angles of 15° have been experimentally demonstrated for a 27 nm shift in the control wavelength. For a larger wavelength scanning (50 nm), 28° deflections are anticipated while maintaining the Bragg condition satisfied. We then discuss some issues related to photosensitive materials able to dynamically record the optically induced refractive index change. The specific example of Bi12 Si 020 or Bi12 Ge 020 photorefractive crystals is presented. Indeed these materials are very attractive as they require low driving energy and exhibit a memory effect. This latter property permits to achieve numerous iterations between computing cells before reconfiguration of the interconnect network.

  17. Choice of Grating Orientation for Evaluation of Peripheral Vision

    PubMed Central

    Venkataraman, Abinaya Priya; Winter, Simon; Rosén, Robert; Lundström, Linda

    2016-01-01

    ABSTRACT Purpose Peripheral resolution acuity depends on the orientation of the stimuli. However, it is uncertain if such a meridional effect also exists for peripheral detection tasks because they are affected by optical errors. Knowledge of the quantitative differences in acuity for different grating orientations is crucial for choosing the appropriate stimuli for evaluations of peripheral resolution and detection tasks. We assessed resolution and detection thresholds for different grating orientations in the peripheral visual field. Methods Resolution and detection thresholds were evaluated for gratings of four different orientations in eight different visual field meridians in the 20-deg visual field in white light. Detection measurements in monochromatic light (543 nm; bandwidth, 10 nm) were also performed to evaluate the effects of chromatic aberration on the meridional effect. A combination of trial lenses and adaptive optics system was used to correct the monochromatic lower- and higher-order aberrations. Results For both resolution and detection tasks, gratings parallel to the visual field meridian had better threshold compared with the perpendicular gratings, whereas the two oblique gratings had similar thresholds. The parallel and perpendicular grating acuity differences for resolution and detection tasks were 0.16 logMAR and 0.11 logMAD, respectively. Elimination of chromatic errors did not affect the meridional preference in detection acuity. Conclusions Similar to peripheral resolution, detection also shows a meridional effect that appears to have a neural origin. The threshold difference seen for parallel and perpendicular gratings suggests the use of two oblique gratings as stimuli in alternative forced-choice procedures for peripheral vision evaluation to reduce measurement variation. PMID:26889822

  18. Review of High-Speed Fiber Optic Grating Sensors Systems

    SciTech Connect

    Udd, E; Benterou, J; May, C; Mihailov, S J; Lu, P

    2010-03-24

    Fiber grating sensors can be used to support a wide variety of high speed measurement applications. This includes measurements of vibrations on bridges, traffic monitoring on freeways, ultrasonic detection to support non-destructive tests on metal plates and providing details of detonation events. This paper provides a brief overview of some of the techniques that have been used to support high speed measurements using fiber grating sensors over frequency ranges from 10s of kHz, to MHZ and finally toward frequencies approaching the GHz regime. Very early in the development of fiber grating sensor systems it was realized that a high speed fiber grating sensor system could be realized by placing an optical filter that might be a fiber grating in front of a detector so that spectral changes in the reflection from a fiber grating were amplitude modulated. In principal the only limitation on this type of system involved the speed of the output detector which with the development of high speed communication links moved from the regime of 10s of MHz toward 10s of GHz. The earliest deployed systems involved civil structures including measurements of the strain fields on composite utility poles and missile bodies during break tests, bridges and freeways. This was followed by a series of developments that included high speed fiber grating sensors to support nondestructive testing via ultrasonic wave detection, high speed machining and monitoring ship hulls. Each of these applications involved monitoring mechanical motion of structures and thus interest was in speeds up to a few 10s of MHz. Most recently there has been interest in using fiber grating to monitor the very high speed events such as detonations and this has led to utilization of fiber gratings that are consumed during an event that may require detection speeds of hundreds of MHz and in the future multiple GHz.

  19. Electron diffraction from free-standing, metal-coated transmission gratings

    NASA Astrophysics Data System (ADS)

    Gronniger, Glen; Barwick, Brett; Batelaan, Herman; Savas, Tim; Pritchard, Dave; Cronin, Alex

    2005-09-01

    Electron diffraction from a free-standing nanofabricated transmission grating was demonstrated, with energies ranging from 125 eV to 25 keV. Observation of 21 diffraction orders highlights the quality of the gratings. The image charge potential due to one electron was measured by rotating the grating. These gratings may pave the way to low-energy electron interferometry.

  20. 75 FR 43144 - Certain Steel Grating from the People's Republic of China: Countervailing Duty Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-23

    ... International Trade Administration Certain Steel Grating from the People's Republic of China: Countervailing... certain steel grating (steel grating) from the People's Republic of China (PRC). EFFECTIVE DATE: July 23... in the countervailing duty investigation of certain steel grating from PRC. See Certain Steel...

  1. Transducing mechanical force by use of a diffraction grating sensor.

    PubMed

    Wang, Wei-Chih; Ho, Chi-Ting; Lian, Yi-Ru; Chuang, Wei-Ching

    2006-03-20

    A novel means of transducing mechanical force by using a polymeric-based diffractive grating sensor is presented. The diffraction gratings are successfully fabricated upon poly(dimethyl siloxane) polymer substrates by holographic interference and micromolding. A micromaterial tensile test incorporated into the surface diffraction grating experiment showed that a relationship between the load and the observed diffraction-pattern shift could be obtained. The results show an excellent correlation between the optical measurement and load, with a sensitivity of 0.05 N.

  2. Optical fibre grating refractometers for resin cure monitoring

    NASA Astrophysics Data System (ADS)

    Buggy, S. J.; Chehura, E.; James, S. W.; Tatam, R. P.

    2007-06-01

    The use of fibre grating refractometers as a means of monitoring the cure of a UV-cured epoxy resin is presented. The wavelength shift of the attenuation bands of a long period grating and the spectral response of a tilted fibre Bragg grating sensor were measured simultaneously during the cure of the resin and compared with measurements made using a fibre optic Fresnel-based refractometer. The results showed a good correlation (6 × 10-3 rius) and illustrate the potential of the techniques for non-invasive composite material cure monitoring.

  3. High speed measurements using fiber-optic Bragg gratings

    NASA Astrophysics Data System (ADS)

    Benterou, Jerry; May, Chadd; Udd, Eric; Mihailov, Stephen J.; Lu, Ping

    2011-06-01

    Fiber grating sensors may be used to monitor high-speed events that include catastrophic failure of structures, ultrasonic testing and detonations. This paper provides insights into the utility of fiber grating sensors to measure structural changes under extreme conditions. An emphasis is placed on situations where there is a structural discontinuity. Embedded chirped fiber Bragg grating (CFBG) sensors can track the very high-speed progress of detonation waves (6-9 km/sec) inside energetic materials. This paper discusses diagnostic instrumentation and analysis techniques used to measure these high-speed events.

  4. High Speed Measurements using Fiber-optic Bragg Grating Sensors

    SciTech Connect

    Benterou, J J; May, C A; Udd, E; Mihailov, S J; Lu, P

    2011-03-26

    Fiber grating sensors may be used to monitor high-speed events that include catastrophic failure of structures, ultrasonic testing and detonations. This paper provides insights into the utility of fiber grating sensors to measure structural changes under extreme conditions. An emphasis is placed on situations where there is a structural discontinuity. Embedded chirped fiber Bragg grating (CFBG) sensors can track the very high-speed progress of detonation waves (6-9 km/sec) inside energetic materials. This paper discusses diagnostic instrumentation and analysis techniques used to measure these high-speed events.

  5. Emerging Beam Resonances in Atom Diffraction from a Reflection Grating

    SciTech Connect

    Zhao, Bum Suk; Meijer, Gerard; Schoellkopf, Wieland

    2010-06-18

    We report on the observation of emerging beam resonances, well known as Rayleigh-Wood anomalies and threshold resonances in photon and electron diffraction, respectively, in an atom-optical diffraction experiment. Diffraction of He atom beams reflected from a blazed ruled grating at grazing incidence has been investigated. The total reflectivity of the grating as well as the intensities of the diffracted beams reveal anomalies at the Rayleigh angles of incidence, i.e., when another diffracted beam emerges parallel to the grating surface. The observed anomalies are discussed in terms of the classical wave-optical model of Rayleigh and Fano.

  6. Rigorous coupled-wave analysis for two-dimensional gratings

    NASA Astrophysics Data System (ADS)

    Logofătu, Petre Cătălin

    2005-08-01

    Rigorous Coupled-Wave Analysis for 2D gratings is reviewed. The main features of RCWA such as the Fourier expansion of the dielectric function in the grating area, solving the Maxwell equation inside the grating, the eigenvalue problem and the matching of the tangential fields at the interfaces are described. Key improvements of the theory, that allows the reduction of the work time by orders of magnitude, such as the reduction of the sue of the matrix for the eigenvalue problem are stressed. The computer code written based on this theory passed consistency tests and was checked against other computer codes.

  7. Holographic optical grating and method for optimizing monochromator configuration

    DOEpatents

    Koike, Masato

    1999-01-01

    This invention comprises a novel apparatus for recording a holographic groove pattern on a diffraction grating blank. The recording apparatus is configured using newly developed groups of analytical equations. The invention further comprises the novel holographic diffraction grating made with the inventive recording apparatus. The invention additionally comprises monochromators and spectrometers equipped with the inventive holographic diffraction grating. Further, the invention comprises a monochromator configured to reduce aberrations using a newly developed group of analytical equations. Additionally, the invention comprises a method to reduce aberrations in monochromators and spectrometers using newly developed groups of analytical equations.

  8. FLC diffraction grating: Efficiency enhancement by SWCNT doping

    NASA Astrophysics Data System (ADS)

    Gupta, Swadesh Kumar; Singh, Dharmendra Pratap; Manohar, Rajiv

    2013-06-01

    At present, Ferroelectric liquid crystals (FLCs) are well known for their use as a switchable grating in surface stabilized mode. The efficiency of such gratings is not attractive enough to be used in devices. An approach that uses an electro-optically tunable phase grating to enhance the diffraction efficiency is proposed here. The doping of Single wall carbon nanotubes (SWCNTs) in pure FLC has shown improved diffraction efficiency. The observations indicate towards the phase diffraction phenomenon. The enhanced efficiency of first order diffraction suggests the use of present system in holography and different spatial light modulators.

  9. Wavelength demodulation of fiber grating sensors using hybrid optical bistability

    NASA Astrophysics Data System (ADS)

    Lv, Guohui; Ou, Jinping; Wang, Huiying; Jiang, Xu; Shang, Shaohua

    2007-07-01

    In this article, a novel approach for demodulation of fiber grating sensors with high resolution is proposed based on a hybrid fiber optical bistablity device (OBD). This OBD is consisted of a FFP ring-cavity laser, fiber Bragg grating (FBG) and a certain optoelectronic feedback circuit. The optical bistability can be realized through alternative the center wavelength of the tunable fiber laser when the output power of the laser is fixed. The Bragg wavelength of sensing grating is determined by the switching on voltage of OBD.

  10. Characteristics of a cascaded grating multi wavelength dye laser

    NASA Astrophysics Data System (ADS)

    Rana, Paramjit; Sridhar, G.; Manohar, K. G.

    2016-12-01

    Characteristics of a multi wavelength dye laser in two cascaded grating resonator configurations are presented. DCM dye dissolved in ethanol, was transversely pumped by second harmonic of Nd:YAG laser and four wavelength, independently tunable, collinear dye laser operation was obtained in Cascaded Grazing Incidence Grating cavity (CGIG) and Hybrid CGIG with fourth grating in Littrow angle (HCGIG) configuration. Gain competition effect of all the sub-cavities was fully characterized and wavelength zones of operation were identified for each cavity for sustaining four wavelength operation. Overall efficiency of the oscillator was measured to be around 2% in CGIG and 7% in HCGIG.

  11. Phase-shifting point diffraction interferometer phase grating designs

    DOEpatents

    Naulleau, Patrick

    2001-01-01

    Diffraction phase gratings are employed in phase-shifting point diffraction interferometers to improve the interferometric fringe contrast. The diffraction phase grating diffracts a zeroth-order diffraction of light at a first power level to the test-beam window of a mask that is positioned at the image plane and a first-order diffraction at a second power to the reference-beam pinhole. The diffraction phase grating is preferably selected to yield a desired ratio of the first power level to second power level.

  12. Ultrafast laser inscribed fiber Bragg gratings for sensing applications

    NASA Astrophysics Data System (ADS)

    Mihailov, Stephen J.

    2016-05-01

    Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on femtosecond infrared laser-material processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This tutorial paper will present a review of some of the more recent developments.

  13. A reconfigurable optofluidic Michelson interferometer using tunable droplet grating.

    PubMed

    Chin, L K; Liu, A Q; Soh, Y C; Lim, C S; Lin, C L

    2010-04-21

    This paper presents a novel optofluidic Michelson interferometer based on droplet microfluidics used to create a droplet grating. The droplet grating is formed by a stream of plugs in the microchannel with constant refractive index variation. It has a real-time tunability in the grating period through varying the flow rates of the liquids and index variation via different combinations of liquids. The optofluidic Michelson interferometer is highly sensitive and is suitable for the measurement of biomedical and biochemical buffer solutions. The experimental results show that it has a sensitivity of 66.7 nm per refractive index unit (RIU) and a detection range of 0.086 RIU.

  14. Single-grating laser pulse stretcher and compressor.

    PubMed

    Lai, M; Lai, S T; Swinger, C

    1994-10-20

    Stretching and compressing of laser pulses is demonstrated with a single-grating apparatus. A laser pulse of 110 fs is stretched to 250 ps and then recompressed to 115 fs. The apparatus exploits a two-level structure: one level for stretching and the other for compressing. This single-grating configuration shows significant simplification in structure and alignment over existing multiple-grating systems. Such a stretcher-compressor is particularly suitable for use with chirped-pulse amplification in which laser wavelength tuning is desirable. Only one rotational adjustment is rquired to restore the alignment of the entire stretcher and compressor when the laser wavelength is changed.

  15. Transmission grating goniometer elements for use at synchrotron radiation facilities

    NASA Astrophysics Data System (ADS)

    Tatchyn, R.; Lindau, I.

    1982-04-01

    In this paper we show analytically that accurate detection of the positions of the diffracted orders from a holographic transmission grating can be used to compute the angle of incidence of the light onto the grating, irrespective of the light's frequency. Since such a device may be employed as a goniometer, and since beam height may be measured independently, we show that such grating may be employed as beam attitude/altitude detectors at synchrotron radiation facilities where beam steering and positioning are problematical.

  16. Aberrations of diffracted wave fields. II. Diffraction gratings.

    PubMed

    Mahajan, V N

    2000-12-01

    The Rayleigh-Sommerfeld theory is applied to diffraction of a spherical wave by a grating. The grating equation is obtained from the aberration-free diffraction pattern, and its aberrations are shown to be the same as the conventional aberrations obtained by using Fermat's principle. These aberrations are shown to be not associated with the diffraction process. Moreover, it is shown that the irradiance distribution of a certain diffraction order is the Fraunhofer diffraction pattern of the grating aperture as a whole aberrated by the aberration of that order.

  17. Thermally tunable grating using thermo-responsive magnetic fluid

    NASA Astrophysics Data System (ADS)

    Zaibudeen, A. W.; Philip, John

    2017-04-01

    We report a thermally tunable grating prepared using poly(N-isopropylacrylamide) and super paramagnetic iron oxide nanoparticles. The array spacing is reversibly tuned by varying the temperature between 5 and 38 °C. Here, the ability of thermo-responsive polymer brushes to alter their conformation at an interface is exploited to control the grating spacing in nanoscale. The underlying mechanism for the temperature dependent conformational changes are studied by measuring the subtle intermolecular forces between the polymer covered interfaces. It is observed that the interparticle forces are repulsive and exponentially decaying with distance. The thermo-responsive grating is simple to use and offers a wide range of applications.

  18. Imaging properties of high aspect ratio absorption gratings for use in preclinical x-ray grating interferometry.

    PubMed

    Trimborn, Barbara; Meyer, Pascal; Kunka, Danays; Zuber, Marcus; Albrecht, Frederic; Kreuer, Sascha; Volk, Thomas; Baumbach, Tilo; Koenig, Thomas

    2016-01-21

    X-ray grating interferometry is one among various methods that allow extracting the so-called phase and visibility contrasts in addition to the well-known transmission images. Crucial to achieving a high image quality are the absorption gratings employed. Here, we present an in-depth analysis of how the grating type and lamella heights influence the final images. Benchmarking gratings of two different designs, we show that a frequently used proxy for image quality, a grating's so-called visibility, is insufficient to predict contrast-to-noise ratios (CNRs). Presenting scans from an excised rat lung, we demonstrate that the CNRs obtained for transmission and visibility images anti-correlate. This is explained by the stronger attenuation implied by gratings that are engineered to provide high visibilities by means of an increased lamella height. We show that even the visibility contrast can suffer from this effect when the associated reduced photon flux on the detector is not outweighed by a corresponding gain in visibility. Resulting in an inevitable trade-off between the quality of the two contrasts, the question of how an optimal grating should be designed can hence only be answered in terms of Pareto optimality.

  19. Performance of multilayer coated diffraction gratings in the EUV

    NASA Technical Reports Server (NTRS)

    Keski-Kuha, Ritva A. M.; Thomas, Roger J.; Gum, Jeffrey S.; Condor, Charles E.

    1990-01-01

    The effect of multilayer coating application on the performance of a diffraction grating in the EUV spectral region was evaluated by examining the performance of a 3600-line/mm and a 1200-line/mm replica blazed gratings, designed for operation in the 300-A spectral region in first order. A ten-layer IrSi multilayer optimized for 304 A was deposited using electron-beam evaporation. The grating efficiency was measured on the SURF II calibration beamline in a chamber designed for calibrating the solar EUV rocket telescope and spectrograph multilayer coatings. A significant (by a factor of about 7) enhancement in grating efficiency in the 300-A region was demonstrated.

  20. Quasi-periodic gratings: diffraction orders accelerate along curves.

    PubMed

    Gao, Nan; Li, Hailiang; Zhu, Xiaoli; Hua, Yilei; Xie, Changqing

    2013-08-01

    Light diffracting to different diffraction orders of a periodic grating generally propagates along a set of straight trajectories. Here we show that certain quasi-periodic gratings can produce curved diffraction orders. These curved lobes are created by the caustic interference of the originally straight diffraction orders and manifest themselves as accelerating beams. Both numerical simulations and experimental results demonstrate the validity of multiple accelerating beam generation with a single binary grating. Our work makes a quantitative link between the quasi-periodicity of a grating and the resulting caustic diffraction orders. Furthermore, the use of binary devices has important applications in acoustics, x-ray optics, and electron beam engineering and is also useful when high optical power is needed.

  1. Large spontaneous emission rate enhancement in grating coupled hyperbolic metamaterials.

    PubMed

    Sreekanth, Kandammathe Valiyaveedu; Krishna, Koduru Hari; De Luca, Antonio; Strangi, Giuseppe

    2014-09-11

    Hyperbolic metamaterial (HMM), a sub-wavelength periodic artificial structure with hyperbolic dispersion, can enhance the spontaneous emission of quantum emitters. Here, we demonstrate the large spontaneous emission rate enhancement of an organic dye placed in a grating coupled hyperbolic metamaterial (GCHMM). A two-dimensional (2D) silver diffraction grating coupled with an Ag/Al2O3 HMM shows 18-fold spontaneous emission decay rate enhancement of dye molecules with respect to the same HMM without grating. The experimental results are compared with analytical models and numerical simulations, which confirm that the observed enhancement of GCHMM is due to the outcoupling of non-radiative plasmonic modes as well as strong plasmon-exciton coupling in HMM via diffracting grating.

  2. Reduced length fibre Bragg gratings for high frequency acoustic sensing

    NASA Astrophysics Data System (ADS)

    Davis, Claire; Robertson, David; Brooks, Chris; Norman, Patrick; Rosalie, Cedric; Rajic, Nik

    2014-12-01

    In-fibre Bragg gratings (FBGs) are now well established for applications in acoustic sensing. The upper frequency response limit of the Bragg grating is determined by its gauge length, which has typically been limited to about 1 mm for commercially available Type 1 gratings. This paper investigates the effect of FBG gauge length on frequency response for sensing of acoustic waves. The investigation shows that the ratio of wavelength to FBG length must be at least 8.8 in order to reliably resolve the strain response without significant gain roll-off. Bragg gratings with a gauge length of 200 µm have been fabricated and their capacity to measure low amplitude high frequency acoustic strain fields in excess of 2 MHz is experimentally demonstrated. The ultimate goal of this work is to enhance the sensitivity of acoustic damage detection techniques by extending the frequency range over which acoustic waves may be reliably measured using FBGs.

  3. High speed demodulation systems for fiber optic grating sensors

    NASA Technical Reports Server (NTRS)

    Udd, Eric (Inventor); Weisshaar, Andreas (Inventor)

    2002-01-01

    Fiber optic grating sensor demodulation systems are described that offer high speed and multiplexing options for both single and multiple parameter fiber optic grating sensors. To attain very high speeds for single parameter fiber grating sensors ratio techniques are used that allow a series of sensors to be placed in a single fiber while retaining high speed capability. These methods can be extended to multiparameter fiber grating sensors. Optimization of speeds can be obtained by minimizing the number of spectral peaks that must be processed and it is shown that two or three spectral peak measurements may in specific multiparameter applications offer comparable or better performance than processing four spectral peaks. Combining the ratio methods with minimization of peak measurements allows very high speed measurement of such important environmental effects as transverse strain and pressure.

  4. Zonal wavefront estimation using an array of hexagonal grating patterns

    SciTech Connect

    Pathak, Biswajit E-mail: brboruah@iitg.ernet.in; Boruah, Bosanta R. E-mail: brboruah@iitg.ernet.in

    2014-10-15

    Accuracy of Shack-Hartmann type wavefront sensors depends on the shape and layout of the lenslet array that samples the incoming wavefront. It has been shown that an array of gratings followed by a focusing lens provide a substitution for the lensslet array. Taking advantage of the computer generated holography technique, any arbitrary diffraction grating aperture shape, size or pattern can be designed with little penalty for complexity. In the present work, such a holographic technique is implemented to design regular hexagonal grating array to have zero dead space between grating patterns, eliminating the possibility of leakage of wavefront during the estimation of the wavefront. Tessellation of regular hexagonal shape, unlike other commonly used shapes, also reduces the estimation error by incorporating more number of neighboring slope values at an equal separation.

  5. Analysis of dispersion characteristics of long period fiber grating

    NASA Astrophysics Data System (ADS)

    Jain, Vishal; Pawar, Santosh; Kumbhaj, S.; Sen, P. K.

    2016-10-01

    Present work deals with theoretical analysis of dispersion characteristics of long period fiber grating using straight forward coupled mode theory. Simple analytical solutions are obtained for co propagating core and cladding modes under linear regime. These solutions are used to derive expressions for transmission coefficient (tLPG), phase (ϕL), delay (τρ) and group velocity dispersion (Dρ) for proposed grating structure. Attention is paid to study the delay response of the grating, by varrying physical parameters like incident wavelength and coupling strength of grating. Negative values of group delay for certain value of coupling strength shows that long period fiber can be used as dispersion compansator device in optical fiber communication link.

  6. The extreme nearfield of an acoustic diffraction grating

    NASA Technical Reports Server (NTRS)

    Ochs, R. L., Jr.; Maynard, J. D.; Williams, E. G.; Hughes, W. J.

    1983-01-01

    An expression for the transmitted sound field near (within a fraction of a wavelength) an array of slits is derived under the assumption that the normal component of the particle velocity is the same, in the slits, as if no grating were present and zero everywhere else in the plane of the grating. The expression is in the form of an inverse Fourier transform and can be evaluated quickly using a standard fast-Fourier-transform (FFT) algorithm. Using this technique, the sound pressure on the axis of symmetry normal to the grating was evaluated for a plane-wave incident at various angles with respect to the normal to the grating, and the results were found to provide an excellent qualitative (and to a significant degree quantitative) description of some experimental measurements. Extensions of the method to oscillating pistons of arbitrary (but planar) configuration in a rigid baffle are indicated.

  7. Broadband enhanced transmission of acoustic waves through serrated metal gratings

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Xiang; Deng, Yu-Qiang; Xu, Di-Hu; Fan, Ren-Hao; Peng, Ru-Wen; Chen, Ze-Guo; Lu, Ming-Hui; Huang, X. R.; Wang, Mu

    2015-01-01

    In this letter, we have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing, and acoustic devices.

  8. Multichannel optical signal processing using sampled fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zhang, Guiju; Wang, Chinhua; Zhu, Xiaojun

    2008-12-01

    Sampled and linearly chirped fiber Bragg gratings provide multiple wavelength responses and linear group delays (constant dispersions) within each of the wavelength channels. We show that the sampled and chirped fiber Bragg gratings can be used to perform multiwavelength signal processing. In particular, we demonstrate, by numerical simulation, their use for performing real-time Fourier transform (RTFT) and for pulse repetition rate multiplication (PRRM) simultaneously over multiple wavelength channels. To present how the sampled fiber Bragg gratings perform the multichannel optical signal processing, a 9-channel sampled fiber grating with 100GHz channel spacing was designed and the effect of ripples in both amplitude and the group delay channel on the performance of the signal processing was examined and discussed.

  9. Grate assembly for fixed-bed coal gasifier

    DOEpatents

    Notestein, John E.

    1993-01-01

    A grate assembly for a coal gasifier of a moving-bed or fixed-bed type is provided for crushing agglomerates of solid material such as clinkers, tailoring the radial distribution of reactant gases entering the gasification reaction zone, and control of the radial distribution of downwardly moving solid velocities in the gasification and combustion zone. The clinker crushing is provided by pinching clinkers between vertically oriented stationary bars and angled bars supported on the upper surface of a rotating conical grate. The distribution of the reactant gases is provided by the selective positioning of horizontally oriented passageways extending through the grate. The radial distribution of the solids is provided by mounting a vertically and generally radially extending scoop mechanism on the upper surface of the grate near the apex thereof.

  10. Efficiency-enhanced third-order grating coupler.

    PubMed

    Ura, S; Fujii, T; Suhara, T; Nishihara, H

    1999-05-10

    A third-order grating coupler with a grating period 3 times that of a first-order grating is discussed in terms of efficiency enhancement. A reflection film is integrated between the optical buffer layer and the substrate beneath the grating-guiding core. The power-distribution ratio for each diffracted wave depends on the optical buffer layer's thickness because of interference effects. The thickness is determined to suppress first- and second-order diffraction and to enhance the power distribution to the output air-radiation wave generated by third-order diffraction. A demonstrator was designed and examined at a wavelength of 0.82 microm. The measured output coupling efficiency was 40%, whereas the theoretical prediction was 60%.

  11. Lasing in nano-grating with Fano resonance

    NASA Astrophysics Data System (ADS)

    Chen, Ya-Bin; Deng, Zi-Lan; Dong, Jian-Wen

    2016-10-01

    We propose a new scheme of lasing in a nano-grating with Fano resonance by the independent control of dark and bright modes. The controllability of both dark and bright modes can be achieved by fine-tuning the widths of two kinds of metallic stripes in the nano-grating. It enables the match between resonant frequencies of the nano-grating structure and the absorption and emission frequencies of gain medium. For example, changing the width of the thin strip is to hit the emission peak of the gain medium, while the fat strip corresponds to the absorption peak of the gain medium. We work out an optimal example of silver grating immersing Rhodamine dye, verifying the lasing dynamic process with minimum threshold and maximum output power. It may provide a new way on low-threshold and high-efficient plasmon laser.

  12. Photonic crystal fiber long-period gratings for biochemical sensing.

    PubMed

    Rindorf, Lars; Jensen, Jesper B; Dufva, Martin; Pedersen, Lars Hagsholm; Høiby, Poul Erik; Bang, Ole

    2006-09-04

    We present experimental results showing that long-period gratings in photonic crystal fibers can be used as sensitive biochemical sensors. A layer of biomolecules was immobilized on the sides of the holes of the photonic crystal fiber and by observing the shift in the resonant wavelength of a long-period grating it was possible to measure the thickness of the layer. The long-period gratings were inscribed in a large-mode area silica photonic crystal fiber with a CO2 laser. The thicknesses of a monolayer of poly-L-lysine and double-stranded DNA was measured using the device. We find that the grating has a sensitivity of approximately 1.4nm/1nm in terms of the shift in resonance wavelength in nm per nm thickness of biomolecule layer.

  13. Solving conical diffraction grating problems with integral equations.

    PubMed

    Goray, Leonid I; Schmidt, Gunther

    2010-03-01

    Off-plane scattering of time-harmonic plane waves by a plane diffraction grating with arbitrary conductivity and general surface profile is considered in a rigorous electromagnetic formulation. Integral equations for conical diffraction are obtained involving, besides the boundary integrals of the single and double layer potentials, singular integrals, the tangential derivative of single-layer potentials. We derive an explicit formula for the calculation of the absorption in conical diffraction. Some rules that are expedient for the numerical implementation of the theory are presented. The efficiencies and polarization angles compared with those obtained by Lifeng Li for transmission and reflection gratings are in a good agreement. The code developed and tested is found to be accurate and efficient for solving off-plane diffraction problems including high-conductive gratings, surfaces with edges, real profiles, and gratings working at short wavelengths.

  14. Displacement measurement using a wavelength-phase-shifting grating interferometer.

    PubMed

    Lee, Ju-Yi; Jiang, Geng-An

    2013-10-21

    A grating interferometer based on the wavelength-modulated phase-shifting method for displacement measurements is proposed. A laser beam with sequential phase shifting can be accomplished using a wavelength-modulated light passing through an unequal-path-length optical configuration. The optical phase of the moving grating is measured by the wavelength-modulated phase-shifting technique and the proposed time-domain quadrature detection method. The displacement of the grating is determined by the grating interferometry theorem with the measured phase variation. Experimental results reveal that the proposed method can detect a displacement up to a large distance of 1 mm and displacement variation down to the nanometer range.

  15. Observation of subterahertz monochromatic transition radiation from a grating

    NASA Astrophysics Data System (ADS)

    Potylitsyn, A. P.; Naumenko, G. A.; Sukhikh, L. G.; Aryshev, A.; Shevelev, M.; Terunuma, N.; Urakawa, J.

    2016-12-01

    Transition radiation appearing when a charged particle crosses the interface between two media with different dielectric constants, e.g., a metal-vacuum interface, has been well studied in a wide spectral range. However, primarily, radiation from smooth interfaces has been studied. Transition radiation from conducting gratings (grating transition radiation) is experimentally studied and theoretically analyzed in this work. In this case, it is possible to obtain monochromatic radiation with a tunable frequency depending on the rotation angle of the grating with respect to the electron momentum. Coherent grating transition radiation can be efficiently used as a source of terahertz radiation based on the use of a compact electron accelerator with an energy below 10 MeV and a bunch duration of ≤1 ps.

  16. Fiber optical Bragg grating sensors embedded in CFRP wires

    NASA Astrophysics Data System (ADS)

    Nellen, Philipp M.; Frank, Andreas; Broennimann, Rolf; Meier, Urs; Sennhauser, Urs J.

    1999-05-01

    Based on the example application of Emmenbridge, a newly built steel-concrete-composite bridge in Switzerland with 47 m long built-in carbon fiber reinforced polymer (CFRP) prestressing cables, we will present and analyze the process chain leading to a reliable surveillance of modern civil engineering structures with embedded fiber optical Bragg gratings. This consists first in the embedding of optical fibers and in-fiber Bragg gratings in long CFRP wires in an industrial environment, including fiber optical monitoring of the curing process. Then, various qualifying tests were done: annealing experiments for determining optical lifetime of the Bragg gratings used, dynamic and static tensile tests for estimating their mechanical lifetime under operation, push-out experiments to check adhesion of fiber/coating/matrix interfaces, and performance tests to determine strain and temperature sensitivity of the embedded Bragg gratings. Finally, the prestressing cables were equipped with the CFRP sensor wires and built into the bridge.

  17. Transverse strain measurements using fiber optic grating based sensors

    NASA Technical Reports Server (NTRS)

    Udd, Eric (Inventor)

    1998-01-01

    A system and method to sense the application of transverse stress to an optical fiber which includes a light source that producing a relatively wide spectrum light beam. The light beam is reflected or transmitted off of an optical grating in the core of an optical fiber that is transversely stressed either directly or by the exposure to pressure when the fiber is bifringent so that the optical fiber responds to the pressure to transversely stress its core. When transversely stressed, the optical grating produces a reflection or transmission from the light beam that has two peaks or minimums in its frequency spectrum whose spacing and/or spread are indicative of the forces applied to the fiber. One or more detectors sense the reflection or transmissions from the optical grating to produce an output representative of the applied force. Multiple optical gratings and detectors may be employed to simultaneously measure temperature or the forces at different locations along the fiber.

  18. Index grating lifetime in photorefractive GaAs

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Partovi, Afshin

    1988-01-01

    The index grating lifetime in liquid encapsulated Czochralski-grown undoped semi-insulating GaAs was measured using a beam coupling technique. The largest lifetime measure was about 8 s under a read beam intensity of 0.7 mW/sq cm with the grating periodicity being 0.63 microns. The measured value decreases to milliseconds as the read beam intensity and the grating periodicity increase to about 10 mW/sq cm and 4 microns, respectively. This range of grating lifetime in this material is adequate for its use in real-time spatial light modulators, reconfigurable beam steering devices, and dynamic memory elements, for optical computing. In addition, the results suggest that the lifetime is sensitive to residual imperfections in the crystal.

  19. Microfiber Bragg grating for temperature and strain sensing applications

    NASA Astrophysics Data System (ADS)

    Tian, Jie; Liu, Shuhui; Yu, Wenbing; Deng, Peigang

    2017-03-01

    Fiber Bragg grating is inscribed on microfiber with femtosecond laser pulses irradiation. The microfiber is fabricated by stretching a section of single mode fiber over a flame. Periodic grooves are carved on the microfiber by the laser as have been observed experimentally. The microfiber Bragg grating is demonstrated for temperature and strain sensing, and the strain sensitivity is improved with decreased diameters of the microfibers.

  20. High diffraction order grating interferometer for pitch measurement

    NASA Astrophysics Data System (ADS)

    Apostol, Dan; Udrea, Cristian; Garoi, Florin; Vasile, Tiberius; Logofătu, Petre Cătălin

    2011-10-01

    A grating interferometer that uses the high diffraction orders in conjunction with a Twyman-Green commercial interferometer is used for the measurement of in plane movement of gratings. The high diffraction orders ensures the amplification of the measurement precision with a factor equal to the diffraction order of the measurement in principle, because no imaging of features marking the beginning and the end of the measured length feature is necessary, and therefore the resolution limits associated with microscope imaging are eliminated.

  1. Microfiber Bragg grating for temperature and strain sensing applications

    NASA Astrophysics Data System (ADS)

    Tian, Jie; Liu, Shuhui; Yu, Wenbing; Deng, Peigang

    2016-12-01

    Fiber Bragg grating is inscribed on microfiber with femtosecond laser pulses irradiation. The microfiber is fabricated by stretching a section of single mode fiber over a flame. Periodic grooves are carved on the microfiber by the laser as have been observed experimentally. The microfiber Bragg grating is demonstrated for temperature and strain sensing, and the strain sensitivity is improved with decreased diameters of the microfibers.

  2. Grating-assisted silicon-on-insulator racetrack resonator reflector.

    PubMed

    Boeck, Robert; Caverley, Michael; Chrostowski, Lukas; Jaeger, Nicolas A F

    2015-10-05

    We experimentally demonstrate a grating-assisted silicon-on-insulator (SOI) racetrack resonator reflector with a reflect port suppression of 10.3 dB and no free spectral range. We use contra-directional grating couplers within the coupling regions of the racetrack resonator to enable suppression of all but one of the peaks within the reflect port spectrum as well as all but one of the notches within the through port spectrum.

  3. Minimizing Fizeau Fringes During the Contact Printing of Diffraction Gratings

    SciTech Connect

    Ciarlo, D; Rushford, M; Kuzmenko, P; Ge, J

    2001-04-27

    An index matching fluid has been used to minimize the effect of interference fringes which develop when contact printing diffraction gratings on silicon wafers. These fringes are the result of interference effects when there is a small but uneven gap between the photomask and resist surface. They are especially troublesome when printing and etching large area, coarse diffraction gratings on the surface of silicon wafers and silicon disks.

  4. Low efficiency gratings for 3rd harmonic diagnostics applications

    SciTech Connect

    Britten, J.A.; Boyd, R.D.; Perry, M.D.; Shore, B.W.; Thomas, I.M.

    1995-08-09

    The baseline design of the National Ignition Facility (NIF) calls for sampling gratings to provide third-harmonic energy diagnostics in the highly constrained area of the target chamber. These 40 {times} 4O cm transmission gratings are to diffract at (order +1) nominally 0.3% of the incident 351 run light at a small angle on to a focusing mirror and into a calorimeter. The design calls for a plane grating of 500 lines/mm, and approximately 30 run deep, etched into a fused silica focusing lens and subsequently overcoated with a solgel anti reflective coating. Gratings of similar aperture and feature size have been produced for other applications by ion etching processes, but, in an effort to reduce substantially the cost of such optics, we are studying the feasibility of making these gratings by wet chemical etching techniques. Experimentation with high-quality fused silica substrates on 5 and 15 cm. scale has led to a wet etching process which can meet the design goals and which offers no significant scaleup barriers to full sized optics. The grating is produced by holographic exposure and a series of processing steps using only a photoresist mask and a final hydrofluoric acid etch. Gratings on 15 cm diameter test substrates exhibit absolute diffraction efficiencies from 0.2--0.4% with a standard deviation of about 15% of the mean over the full aperture. The efficiency variation is due to variation in linewidth caused by spatial nonuniformities in exposure energy. Uniformity improvements can be realized by using a smaller, more uniform portion of the exposure beam and exposing for longer times. The laser damage threshold for these gratings has been measured at LLNL and found to be identical to that of the fused silica substrate.

  5. Cascaded-grating holography for artificial neural networks

    NASA Astrophysics Data System (ADS)

    Owechko, Y.

    1993-03-01

    A holographic technique for implementing optical neural networks is described in which each connection weight is distributed among a series of cascaded angularly and spatially multiplexed photorefractive gratings. This greatly reduces cross talk caused by the conical Bragg degeneracy associated with a single grating, reduces distortions caused by beam coupling, and improves the utilization of pixels in the input spatial light modulator. Experimental examples of high-quality holographic storage and optical implementations of the perceptron and backpropagation neural networks are also discussed.

  6. Research of double matched fiber optic grating demodulation system

    NASA Astrophysics Data System (ADS)

    Zhao, Limin; Ma, Yuling; Wang, Meng

    2008-12-01

    In this paper, a design of demodulation system applied to Fiber Bragg Grating sensor will be illustrated. This system is based on the principle of Fiber Bragg Grating strain sensing; therefore this applied system has the following characteristics: high sensitivity, high precision, low cost and so on. Demodulation system bases on the traditional matching method, and uses the two matched Fiber Bragg Grating parallel mode. Just because of this, it improves on a certain extent compared with the traditional one. The two Fiber Bragg Gratings are pasted on Hollow Aluminum Cantilever respectively so as to realize the high precision and the large scale strain demodulation. This paper proves the following theory through the academic analyses and experimentation, that is: pasting Fiber Bragg Grating on Hollow Aluminum Cantilever can improve the response sensitivity. During the process of matching, increasing the load on the Hollow Aluminum Cantilever, when the qualities of load cannot beyond the limited quality, there is a good linearity relation between the change of load's quality and the change of wavelength. The limited quality comes from the experimentation. The experimentation proves that the structure of two matched Fiber Bragg Grating parallel can increase the range of strain which can be measured largely, and at the same time this structure can solve double-value problem which exists in the ordinary matching method. The strain sense signal through the two parallel demodulation Fiber Bragg Gratings into data processing circuit. The single chip processes the data from the data processing circuit and works out the strain which is detected by Fiber Bragg Grating sensor.

  7. Spin Wave Diffraction and Perfect Imaging of a Grating

    NASA Astrophysics Data System (ADS)

    Mansfeld, S.; Topp, J.; Martens, K.; Toedt, J. N.; Hansen, W.; Heitmann, D.; Mendach, S.

    2012-01-01

    We study the diffraction of Damon-Eshbach-type spin waves incident on a one-dimensional grating realized by microslits in a thin Permalloy film. By means of time-resolved scanning Kerr microscopy, we observe unique diffraction patterns behind the grating which exhibit replications of the spin wave field at the slits. We show that these spin wave images, with details finer than the wavelength of the incident Damon-Eshbach spin wavelength, arise from the strongly anisotropic spin wave dispersion.

  8. Observation of laser feedback using a grating spectrometer

    NASA Astrophysics Data System (ADS)

    Brekke, Erik G.; Schulz, Matthew A.

    2015-07-01

    We describe an experimental setup for observing the effect of optical feedback in an extended cavity diode laser. A simple grating spectrometer is used to observe the naturally occurring wavelength spread and mode spacing for the diode. When the diode is provided with optical feedback from a grating in the Littman-Metcalf configuration, the tunability of the diode is easily observed. This setup presents an intuitive and cost-effective method for demonstrating optical feedback in an advanced undergraduate laboratory setting.

  9. Humidity and temperature response of photopolymer-based holographic gratings

    NASA Astrophysics Data System (ADS)

    Mikulchyk, Tatsiana; Walshe, James; Cody, Dervil; Martin, Suzanne; Naydenova, Izabela

    2015-05-01

    Holographic sensors have significant potential in various applications ranging from in vitro diagnostics to optical security. They are capable of providing fast, real-time, reversible or irreversible, visual colorimetric or optical readouts. The main challenge in the development of holographic sensors is to improve their selectivity by functionalizing the holographic recording material and achieve a response to a specific analyte. This material should be permeable to the analyte and its properties should change under exposure to the analyte. This work explores the humidity and temperature response of volume phase gratings recorded in photopolymers containing acrylamide and diacetone acrylamide as monomers, and triethanolamine and N-phenylglycine as photoinitiators. Characterization of the humidity response of photopolymer-based gratings in the relative humidity (RH) range of 20-90 % was carried out by measuring the diffraction efficiency of slanted transmission gratings and the position of the maximum intensity in the spectral response of reflection gratings. A strong humidity dependence of the diffraction efficiency of diacetone acrylamide-based transmission gratings was observed at RH=20-90%. The humidity dependence of the spectral response of the reflection gratings showed that photopolymers containing triethanolamine are more hydrophilic than photopolymers containing N-phenylglycine. The temperature response of slanted transmission gratings was investigated in the temperature (T) range of 20-60 °C. Exposure of the photopolymer layers containing triethanolamine to elevated temperature showed that the observed Bragg angle shift was caused by layer shrinkage due to water evaporation. The application of a sealing technique allowed for the observation of the photopolymer layer swelling due to the layer's thermal expansion. The results demonstrate an effective approach to obtaining photopolymer-based gratings with tuneable temperature and humidity sensitivity.

  10. Effect of finite dimensions of diffraction grating to Talbot imaging

    NASA Astrophysics Data System (ADS)

    Pokorný, Petr; Mikš, Antonín.; Novák, Jiří; Novák, Pavel; Rinner, Stefan

    2016-11-01

    This work presents detailed theoretical analysis of the effect of finite dimensions of an amplitude diffraction grating to the edge response function of the Talbot imaging. A diffraction of a plane wave is studied as well as a diffraction of a spherical one. The derived formulas can be used to refine the description of field propagation behind the amplitude diffraction grating; therefore, an analysis and an improvement of current applications, where the Talbot effect is used, can be realised.

  11. Linear displacement measurement with a grating and speckle pattern illumination

    SciTech Connect

    Perez-Quintian, Fernando; Lutenberg, Ariel; Rebollo, Maria A

    2006-07-10

    We present a study of the variations of a speckle pattern passing through a grating that can be displaced. This study is described theoretically by a simple model based on the scalar diffraction theory in the Fresnel zone. The intensity correlation of the modified speckle as a function of the grating displacement is obtained and compared with experimental results.The possibilities of metrological applications in optical encoders are suggested.

  12. Simple formulae for the transmittance of strip gratings

    NASA Astrophysics Data System (ADS)

    Compton, R. C.; Whitbourn, L. B.; McPhedran, R. C.

    1983-11-01

    The simple, accurate formulas presented for transmittance through strip gratings of infinitesimal thickness are valid irrespective of the angle of incidence of the radiation on the gratings, and can take into account the effects of a dielectric substrate. The formulas' range of applicability is demonstrated through a comparison of their predictions with the results of rigorous calculations. The formulas are simple to implement on a computer or programmable calculator, and are accurate over a wide range of grid parameters and wavelengths.

  13. Strain and temperature characterization of photonic crystal fiber Bragg gratings.

    PubMed

    Martelli, Cicero; Canning, John; Groothoff, Nathaniel; Lyytikainen, Katja

    2005-07-15

    A Bragg grating in a photonic crystal fiber was written and its dependence with temperature and strain analyzed. The two observed Bragg wavelengths correspond to a fundamental and a higher-order mode in the optical fiber. The temperature and strain calibration curves for both modes are measured and found to be distinct. The general properties of gratings in these fibers, and their implications, are enunciated.

  14. MEMS-based tunable gratings and their applications

    NASA Astrophysics Data System (ADS)

    Yu, Yiting; Yuan, Weizheng; Qiao, Dayong

    2015-03-01

    The marriage of optics and MEMS has resulted in a new category of optical devices and systems that have unprecedented advantages compared with their traditional counterparts. As an important spatial light modulating technology, diffractive optical MEMS obtains a wide variety of successful commercial applications, e.g. projection displays, optical communication and spectral analysis, due to its features of highly compact, low-cost, IC-compatible, excellent performance, and providing possibilities for developing totally new, yet smart devices and systems. Three most successful MEMS diffraction gratings (GLVs, Polychromator and DMDs) are briefly introduced and their potential applications are analyzed. Then, three different MEMS tunable gratings developed by our group, named as micro programmable blazed gratings (μPBGs) and micro pitch-tunable gratings (μPTGs) working in either digital or analog mode, are demonstrated. The strategies to largely enhance the maximum blazed angle and grating period are described. Some preliminary application explorations based on the developed grating devices are also shown. For our ongoing research focus, we will further improve the device performance to meet the engineering application requirements.

  15. Unraveling the nucleation and growth of spontaneous surface relief gratings

    NASA Astrophysics Data System (ADS)

    Mazaheri, Leila; Sabat, Ribal Georges; Lebel, Olivier; Nunzi, Jean-Michel

    2016-12-01

    Nucleation and growth of spontaneous surface relief gratings (SSRGs) on a Disperse Red 1 (DR1) glass-forming derivative were investigated. No interference pattern is applied and surface patterning is induced using single-beam irradiation: the gratings are self-organized. Grating growth is assumed to initiate from an interference pattern formed between the incident light beam and waves scattered at grazing angle by surface defects. However, the mechanism is not yet fully understood and there is not a comprehensive explanation of the structure formation process. Herein, the grating formation procedure is studied by monitoring the surface topology of thin films exposed to one writing beam for various periods of time, under both linear and circular polarizations, using AFM. Even in the absence of surface defects on the initial film, irradiation produces light-induced surface defects due to the reorientation and mass movement of the azo molecules. These defects act as seeds for SSRG around which gratings gradually emerge and propagate throughout the sample. To consolidate this hypothesis, the formation of gratings was studied on samples with controlled surface roughness. Pore-shaped defects do not diffract light on top of the sample, and thus have no impact on SSRG growth, while for hill-shaped defects, growth rate decreases sharply with defect sizes larger than the writing beam wavelength. Two other analogous glass-forming azobenzene derivatives were studied, and in all cases, SSRG formation was correlated with the induction of birefringence in the early stages of the irradiation.

  16. Analytical treatment of the polychromatic spatially multiplexed volume holographic grating.

    PubMed

    Brotherton-Ratcliffe, David

    2012-10-20

    An alternative model to N-coupled wave theory of the spatially multiplexed finite thickness volume holographic reflection grating is developed from the parallel stacked mirrors (PSM) model in terms of N infinite arrays of parallel stacked mirrors each characterized by a different grating vector. A plane reference wave interacts with each of the N sets of stacked mirrors, producing N signal waves. First-order coupled partial differential equations describing the detailed process of Fresnel reflection within the grating are derived for the reference and N signal waves. These equations can be solved analytically at Bragg resonance where agreement with conventional N-coupled wave theory is exact. The new model is compared for the case of some simple multiplexed volume phase reflection gratings at and away from Bragg resonance with a rigorous coupled-wave solution of the Helmholtz equation. Good agreement is attained for even rather high values of index modulation. For lower modulations more characteristic of modern holographic materials, agreement appears extremely good at and around Bragg resonance, although differences inevitably appear in the higher-order diffractive sideband structure. The analytic model is extended to cover polychromatic spatially multiplexed volume phase gratings at Bragg resonance, where once again agreement with rigorous coupled-wave calculations is very good for index modulations typical for modern holographic gratings. Finally, the model is extended to cover the case of the lossless multicolor phase-reflection hologram, where analytic and graphical results are presented concerning diffractive efficiency.

  17. Creation and transfer of gratings with designed spatially varying periodicity

    NASA Astrophysics Data System (ADS)

    Zhang, Cuiping; Ji, Min; Shen, Wenxin; Ge, Haixiong; Li, Wen-Di

    2016-12-01

    Gratings with spatially varying periodicity have unique applications such as dispersive elements for compact spectrometers and spectrum splitting. However, large-area fabrication of spatially varying gratings, especially those featuring arbitrarily designed and accurate chirp factors, is challenging. In this paper, we develop a facile method that can arbitrarily modulate the spatial distribution of the periodicity in periodic patterns, by stretching shape-tailored elastomeric templates carrying the original periodic patterns and then transferring the deformed patterns onto rigid substrates. Periodicity-varying gratings transferred onto the rigid substrate were characterized by scanning electron microscopy to confirm the capability of our method on modifying and recording the spatial distribution of grating periodicity. As demonstration, we fabricated gratings with various chirp factors on stretched elastomeric molds and on rigid substrates, by varying processing parameters in our method. This work provides a low-cost and high-resolution fabrication technique for large-area chirped grating patterns and enables the exploration of practical applications of periodic structures with spatially varying periodicity.

  18. Dislocated double-layer metal gratings: an efficient unidirectional coupler.

    PubMed

    Liu, Tianran; Shen, Yang; Shin, Wonseok; Zhu, Qiangzhong; Fan, Shanhui; Jin, Chongjun

    2014-07-09

    We propose theoretically and demonstrate experimentally a dislocated double-layer metal grating structure, which operates as a unidirectional coupler capable of launching surface plasmon polaritons in a desired direction under normal illumination. The structure consists of a slanted dielectric grating sandwiched between two gold gratings. The upper gold grating has a nonzero lateral relative displacement with respect to the lower one. Numerical simulations show that a grating structure with 7 periods can convert 49% of normally incident light into surface plasmons with a contrast ratio of 78 between the powers of the surface plasmons launched in two opposite directions. We explain the unidirectional coupling phenomenon by the dislocation-induced interference of the diffracted waves from the upper and lower gold gratings. Furthermore, we developed a simple and cost-effective technique to fabricate the structure via tilted two-beam interference lithography and subsequent shadow deposition of gold. The experimental results demonstrate a coupling efficiency of 36% and a contrast ratio of 43. The relatively simple periodic nature of our structure lends itself to large-scale low-cost fabrication and simple theoretical analysis. Also, unlike the previous unidirectional couplers based on aperiodic structures, the design parameters of our unidirectional coupler can be determined analytically. Therefore, this structure can be an important component for surface-plasmon-based nanophotonic circuits by providing an efficient interface between free-space and surface plasmon waves.

  19. Refraction effects in soft x-ray multilayer blazed gratings.

    PubMed

    Voronov, D L; Salmassi, F; Meyer-Ilse, J; Gullikson, E M; Warwick, T; Padmore, H A

    2016-05-30

    A 2500 lines/mm Multilayer Blazed Grating (MBG) optimized for the soft x-ray wavelength range was fabricated and tested. The grating coated with a W/B4C multilayer demonstrated a record diffraction efficiency in the 2nd blazed diffraction order in the energy range from 500 to 1200 eV. Detailed investigation of the diffraction properties of the grating demonstrated that the diffraction efficiency of high groove density MBGs is not limited by the normal shadowing effects that limits grazing incidence x-ray grating performance. Refraction effects inherent in asymmetrical Bragg diffraction were experimentally confirmed for MBGs. The refraction affects the blazing properties of the MBGs and results in a shift of the resonance wavelength of the gratings and broadening or narrowing of the grating bandwidth depending on diffraction geometry. The true blaze angle of the MBGs is defined by both the real structure of the multilayer stack and by asymmetrical refraction effects. Refraction effects can be used as a powerful tool in providing highly efficient suppression of high order harmonics.

  20. Gaussian-Schell-model beams propagating through rough gratings.

    PubMed

    Torcal-Milla, Francisco Jose; Sanchez-Brea, Luis Miguel

    2011-03-01

    In this work we analyze the near-field intensity distribution produced by a rough grating illuminated with a Gaussian-Schell-model beam. This kind of grating is formed by rough and smooth slits. Statistical techniques are used to describe the grating, and the Fresnel approach is used to perform the propagation of light. Two kinds of coherence affect the light propagation. One of them comes from the light beam, since it is not totally coherent. The other one comes from the rough topography of the grating surface. We have found that the Talbot effect is not present just after the grating, but it gradually increases. In addition, the contrast of the self-images decreases from a certain distance due to the coherence properties of the illumination beam. Then, the self-imaging process is only present between two specific distances from the grating. To corroborate the analytical results, we have performed numerical simulations for the mean intensity distribution based on the Sommerfeld-Rayleigh approach, showing their validity.

  1. "The Reflection Grating Spectrometer on Constellation-X"

    NASA Technical Reports Server (NTRS)

    Cottam, J.

    2006-01-01

    The Constellation-X Reflection Grating Spectrometer (RGS) is designed to provide high-throughput, high-resolution spectra in the long wavelength band of 6 to 50 angstrom. In the nominal design an array of reflection gratings is mounted at the exit of the Spectroscopy X-ray Telescope (SXT) mirror module. The gratings intercept and disperse light to a designated array of CCD detectors. To achieve the throughput (A_eff > 1000 cm2 below 0.6 keV) and resolution (R > 300 below 0.6 keV) requirements for the instrument we are investigating two possible grating designs. The first design uses in-plane gratings in a classical configuration that is very similar to the XMM-Newton RGS. The second design uses off-plane gratings in a conical configuration. The off-plane design has the advantage of providing higher reflectivity and potentially, a higher spectral resolution than the in-plane configuration. In our presentation we will describe the performance requirements and the current status of the technology development.

  2. Ultraviolet surface-enhanced Raman spectroscopy using aluminum plasmonic gratings

    NASA Astrophysics Data System (ADS)

    Roberts, Adam T.; Butun, Serkan; Aydin, Koray; Everitt, Henry O.; Bloemer, Mark; D'Aguanno, Giuseppe; Mattiucci, Nadia

    2013-03-01

    Surface-enhanced Raman scattering (SERS) has been widely studied both theoretically and experimentally for chemical and biological sensing, primarily in the visible and near-infrared wavelengths. Although in the ultraviolet (UV) plasmonic behavior is limited by metallic dampening, we have theoretically shown that SERS enhancement factors as large as 105 can be achieved when the laser is tuned to the plasmonic band edge of an Al metallic grating grown on a sapphire substrate. Using electron beam lithography, aluminum gratings were fabricated whose pitch (150-300 nm), slit widths (64 nm), and thickness (50 nm) were chosen to produce large enhancement factors at wavelengths in the UV. Analytes such as thiophenol were then deposited on the gratings, and UV-SERS spectroscopy was performed to measure the enhancement factors and compare with theoretical estimates. Enhancement factors were measured by comparing the strength of the Raman signal from the grating region with the strength of the Raman signal from adjacent regions without a grating. The dependence of the enhancement factor on laser wavelength relative to the plasmonic band edge for a given grating pitch was explored, as was the effect of using a tapered slit geometry that focuses the local field on the nanoscale.

  3. Apodized grating coupler using fully-etched nanostructures

    NASA Astrophysics Data System (ADS)

    Wu, Hua; Li, Chong; Li, Zhi-Yong; Guo, Xia

    2016-08-01

    A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency. Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer. Project supported by the National Natural Science Foundation of China (Grant Nos. 61222501, 61335004, and 61505003), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111103110019), the Postdoctoral Science Foundation of Beijing Funded Project, China (Grant No. Q6002012201502), and the Science and Technology Research Project of Jiangxi Provincial Education Department, China (Grant No. GJJ150998).

  4. Fiber optic hot-wire flowmeter based on a metallic coated hybrid long period grating/fiber Bragg grating structure.

    PubMed

    Caldas, Paulo; Jorge, Pedro A S; Rego, Gaspar; Frazão, Orlando; Santos, José Luís; Ferreira, Luís Alberto; Araújo, Francisco

    2011-06-10

    In this work an all-optical hot-wire flowmeter based on a silver coated fiber combining a long period grating and a fiber Bragg grating (FBG) structure is proposed. Light from a pump laser at 1480  nm propagating down the fiber is coupled by the long period grating into the fiber cladding and is absorbed by the silver coating deposited on the fiber surface over the Bragg grating structure. This absorption acts like a hot wire raising the fiber temperature locally, which is effectively detected by the FBG resonance shift. The temperature increase depends on the flow speed of the surrounding air, which has the effect of cooling the fiber. It is demonstrated that the Bragg wavelength shift can be related to the flow speed. A flow speed resolution of 0.08  m/s is achieved using this new configuration.

  5. Design of a variable-line-spacing grating pattern for spectrometers based on a grating Fresnel device.

    PubMed

    Li, Xinghui; Zhang, Jinchao; Zhou, Qian; Ni, Kai; Pang, Jinchao; Tian, Rui

    2016-04-01

    In this Letter, we propose a variable-line-spacing (VLS) grating pattern for a hybrid diffractive device termed a grating Fresnel (G-Fresnel) lens, which is used in spectrometers to improve spectral resolution over a wide spectral range. The VLS grating pattern disperses light of specific wavelengths with a different angle and position such that the aberration caused by the Fresnel surface can be compensated for. In this manner, high resolution can be achieved over a relatively wide spectral range. The VLS grating pattern is designed based on the least wave-change principle and simulated by ZEMAX. Results reveal that the VLS G-Fresnel device allows a subnanometer resolution over a spectral range of 200 nm.

  6. Dynamic high pressure measurements using a Fiber Bragg Grating probe and an arrayed waveguide grating spectrometer

    NASA Astrophysics Data System (ADS)

    Barbarin, Y.; Lefrançois, A.; Magne, S.; Woirin, K.; Sinatti, F.; Osmont, A.; Luc, J.

    2016-08-01

    High pressure shock profiles are monitored using a long Fiber Bragg Grating (FBG). Such thin probe, with a diameter of typically 150 μm, can be inserted directly into targets for shock plate experiments. The shocked FBG's portion is stressed under compression, which increases its optical group index and shortens its grating period. Placed along the 2D symmetrical axis of the cylindrical target, the second effect is stronger and the reflected spectrum shifts towards the shorter wavelengths. The dynamic evolution of FBG spectra is recorded with a customized Arrayed Waveguide Grating (AWG) spectrometer covering the C+L band. The AWG provides 40 channels of 200-GHz spacing with a special flattop design. The output channels are fiber-connected to photoreceivers (bandwidth: DC - 400 MHz or 10 kHz - 2 GHz). The experimental setup was a symmetric impact, completed in a 110-mm diameter single-stage gas gun with Aluminum (6061T6) impactors and targets. The FBG's central wavelength was 1605 nm to cover the pressure range of 0 - 8 GPa. The FBG was 50-mm long as well as the target's thickness. The 20-mm thick impactor maintains a shock within the target over a distance of 30 mm. For the impact at 522 m/s, the sustained pressure of 3.6 GPa, which resulted in a Bragg shift of (26.2 +/- 1.5) nm, is measured and retrieved with respectively thin-film gauges and the hydrodynamic code Ouranos. The shock sensitivity of the FBG is about 7 nm/GPa, but it decreases with the pressure level. The overall spectra evolution is in good agreement with the numerical simulations.

  7. Feasibility of fiber Bragg grating and long-period fiber grating sensors under different environmental conditions.

    PubMed

    Wang, Jian-Neng; Tang, Jaw-Luen

    2010-01-01

    This paper presents the feasibility of utilizing fiber Bragg grating (FBG) and long-period fiber grating (LPFG) sensors for nondestructive evaluation (NDE) of infrastructures using Portland cement concretes and asphalt mixtures for temperature, strain, and liquid-level monitoring. The use of hybrid FBG and LPFG sensors is aimed at utilizing the advantages of two kinds of fiber grating to implement NDE for monitoring strains or displacements, temperatures, and water-levels of infrastructures such as bridges, pavements, or reservoirs for under different environmental conditions. Temperature fluctuation and stability tests were examined using FBG and LPFG sensors bonded on the surface of asphalt and concrete specimens. Random walk coefficient (RWC) and bias stability (BS) were used for the first time to indicate the stability performance of fiber grating sensors. The random walk coefficients of temperature variations between FBG (or LPFG) sensor and a thermocouple were found in the range of -0.7499 °C/ [square root]h to -1.3548 °C/ [square root]h. In addition, the bias stability for temperature variations, during the fluctuation and stability tests with FBG (or LPFG) sensors were within the range of 0.01 °C/h with a 15-18 h time cluster to 0.09 °C/h with a 3-4 h time cluster. This shows that the performance of FBG or LPFG sensors is comparable with that of conventional high-resolution thermocouple sensors under rugged conditions. The strain measurement for infrastructure materials was conducted using a packaged FBG sensor bonded on the surface of an asphalt specimen under indirect tensile loading conditions. A finite element modeling (FEM) was applied to compare experimental results of indirect tensile FBG strain measurements. For a comparative analysis between experiment and simulation, the FEM numerical results agreed with those from FBG strain measurements. The results of the liquid-level sensing tests show the LPFG-based sensor could discriminate five

  8. Grating lobe elimination in steerable parametric loudspeaker.

    PubMed

    Shi, Chuang; Gan, Woon-Seng

    2011-02-01

    In the past two decades, the majority of research on the parametric loudspeaker has concentrated on the nonlinear modeling of acoustic propagation and pre-processing techniques to reduce nonlinear distortion in sound reproduction. There are, however, very few studies on directivity control of the parametric loudspeaker. In this paper, we propose an equivalent circular Gaussian source array that approximates the directivity characteristics of the linear ultrasonic transducer array. By using this approximation, the directivity of the sound beam from the parametric loudspeaker can be predicted by the product directivity principle. New theoretical results, which are verified through measurements, are presented to show the effectiveness of the delay-and-sum beamsteering structure for the parametric loudspeaker. Unlike the conventional loudspeaker array, where the spacing between array elements must be less than half the wavelength to avoid spatial aliasing, the parametric loudspeaker can take advantage of grating lobe elimination to extend the spacing of ultrasonic transducer array to more than 1.5 wavelengths in a typical application.

  9. Multipoint sensor based on fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Méndez-Zepeda, O.; Muñoz-Aguirre, S.; Beltrán-Pérez, G.; Castillo-Mixcóatl, J.

    2011-01-01

    In some control and industrial measurement systems of physical variables (pressure, temperature, flow, etc) it is necessary one system and one sensor to control each process. On the other hand, there are systems such as PLC (Programmable Logic Control), which can process several signals simultaneously. However it is still necessary to use one sensor for each variable. Therefore, in the present work the use of a multipoint sensor to solve such problem has been proposed. The sensor consists of an optical fiber laser with two Fabry-Perot cavities constructed using fiber Bragg gratings (FBG). In the same system is possible to measure changes in two variables by detecting the intermodal separation frequency of each cavity and evaluate their amplitudes. The intermodal separation frequency depends on each cavity length. The sensor signals are monitored through an oscilloscope or a PCI card and after that acquired by PC, where they are analyzed and displayed. Results of the evaluation of the intermodal frequency separation peak amplitude behavior with FBG stretching are presented.

  10. Immersion Gratings for Infrared High-resolution Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sarugaku, Yuki; Ikeda, Yuji; Kobayashi, Naoto; Kaji, Sayumi; Sukegawa, Takashi; Sugiyama, Shigeru; Nakagawa, Takao; Arasaki, Takayuki; Kondo, Sohei; Nakanishi, Kenshi; Yasui, Chikako; Kawakita, Hideyo

    2016-10-01

    High-resolution spectroscopy in the infrared wavelength range is essential for observations of minor isotopologues, such as HDO for water, and prebiotic organic molecules like hydrocarbons/P-bearing molecules because numerous vibrational molecular bands (including non-polar molecules) are located in this wavelength range. High spectral resolution enables us to detect weak lines without spectral line confusion. This technique has been widely used in planetary sciences, e.g., cometary coma (H2O, CO, and organic molecules), the martian atmosphere (CH4, CO2, H2O and HDO), and the upper atmosphere of gas giants (H3+ and organic molecules such as C2H6). Spectrographs with higher resolution (and higher sensitivity) still have a potential to provide a plenty of findings. However, because the size of spectrographs scales with the spectral resolution, it is difficult to realize it.Immersion grating (IG), which is a diffraction grating wherein the diffraction surface is immersed in a material with a high refractive index (n > 2), provides n times higher spectral resolution compared to a reflective grating of the same size. Because IG reduces the size of spectrograph to 1/n compared to the spectrograph with the same spectral resolution using a conventional reflective grating, it is widely acknowledged as a key optical device to realize compact spectrographs with high spectral resolution.Recently, we succeeded in fabricating a CdZnTe immersion grating with the theoretically predicted diffraction efficiency by machining process using an ultrahigh-precision five-axis processing machine developed by Canon Inc. Using the same technique, we completed a practical germanium (Ge) immersion grating with both a reflection coating on the grating surface and the an AR coating on the entrance surface. It is noteworthy that the wide wavelength range from 2 to 20 um can be covered by the two immersion gratings.In this paper, we present the performances and the applications of the immersion

  11. Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating

    NASA Astrophysics Data System (ADS)

    Kuo, Ju-Nan; Chen, Kuan-Yu

    2010-11-01

    In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

  12. Electronically reconfigurable superimposed waveguide long-period gratings

    NASA Astrophysics Data System (ADS)

    Kulishov, Mykola; Daxhelet, Xavier; Gaidi, Mounir; Chaker, Mohamed

    2002-08-01

    The perturbation to the refractive index induced by a periodic electric field from two systems of interdigitated electrodes with the electrode-finger period l is analyzed for a waveguide with an electro-optically (EO) active core-cladding. It is shown that the electric field induces two superimposed transmissive refractive-index gratings with different symmetries of their cross-section distributions. One of these gratings has a constant component of an EO-induced refractive index along with its variable component with periodicity l, whereas the second grating possesses only a variable component with periodicity 2l. With the proper waveguide design, the gratings provide interaction between a guided fundamental core mode and two guided cladding modes. Through the externally applied electric potential, these gratings can be independently switched ON and OFF, or they can be activated simultaneously with electronically controlled weighting factors. Coupling coefficients of both gratings are analyzed in terms of their dependence on the electrode duty ratio and dielectric permittivities of the core and cladding. The coupled-wave equations for the superimposed gratings are written and solved. The spectral characteristics are investigated by numerical simulation. It is found that the spectral characteristics are described by a dual-dip transmission spectrum with individual electronic control of the dip depths and positions. Within the concept, a new external potential application scheme is described in which the symmetry of the cross-sectional distribution of the refractive index provides coupling only between the core mode and the cladding modes, preventing interaction of the cladding modes with each another. This simple concept opens opportunities for developing a number of tunable devices for integrated optics by use of the proposed design as a building block.

  13. Polarization-independent mechanically induced long-period fiber gratings

    NASA Astrophysics Data System (ADS)

    Block, Ueyn L.; Ozcan, Aydogan; Digonnet, Michel J. F.; Fejer, Martin M.

    2002-05-01

    We have developed long-period fiber gratings (LPFGs) utilizing the photoelastic effect and have demonstrated polarization-independent operation. The LPFG is made by pressing a standard, jacketed single-mode fiber between a flat plate and a plate with grooves mechanically machined with a suitable period. The grating's transmission spectrum is easily tuned by adjusting pressure, grating tilt, and length. Furthermore, the grating can be completely erased by removing the pressure from the fiber. Grating attenuation greater than 25 dB has been demonstrated with a notch-location polarization dependence of +-4 nm. In this paper we report drastic reduction in this polarization dependence by two different approaches. Passing through the grating a second time after reflecting off a Faraday rotator mirror was successful; this method may be used with other types of LPFGs. The second approach utilizes our mechanical grating's ability to be double-passed with two fibers side-by-side. Between passes, a fiber-loop half-wave plate aligned at 45 degrees to the plane of the grooved plate swaps power between x- and y-polarization states. The resulting output's measured polarization dependence was smaller than +/- 0.2 nm. Further improvement is expected through careful tuning of the wave plate. We also report a computer model of the filter spectrum and its polarization dependence, which takes into account non-uniform index perturbation, lossy cladding modes, cladding index perturbation, as well as the polarization dependence of the photoelastic effect, characteristics not usually present in UV-induced LPFGs. The model generates transmission spectra that agree quite well with experimental results.

  14. Performance evaluation of fiber Bragg gratings at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Juergens, Jeffrey; Adamovsky, Grigory; Floyd, Bertram

    2004-03-01

    The development of integrated fiber optic sensors for smart propulsion systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor"s limits and how it responds under various environmental conditions. The sensor evaluation currently involves examining the performance of fiber Bragg gratings at elevated temperatures. Fiber Bragg gratings (FBG) are periodic variations of the refractive index of an optical fiber. These periodic variations allow the FBG to act as an embedded optical filter passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change what wavelengths are transmitted and what wavelengths are reflected by the grating. Both thermal and mechanical forces acting on the grating will alter its physical characteristics allowing the FBG sensor to detect both temperature variations and physical stresses, strain, placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. This paper reports on test results of the performance of FBGs at elevated temperatures. The gratings looked at thus far have been either embedded in polymer matrix materials or freestanding with the primary focus of this paper being on the freestanding FBGs. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. These parameters include the peak Bragg wavelength, the power of the Bragg wavelength, and total power returned by the FBG. Several test samples were subjected to identical test conditions to

  15. Performance of silicon immersed gratings: measurement, analysis, and modeling

    NASA Astrophysics Data System (ADS)

    Rodenhuis, Michiel; Tol, Paul J. J.; Coppens, Tonny H. M.; Laubert, Phillip P.; van Amerongen, Aaldert H.

    2015-09-01

    The use of Immersed Gratings offers advantages for both space- and ground-based spectrographs. As diffraction takes place inside the high-index medium, the optical path difference and angular dispersion are boosted proportionally, thereby allowing a smaller grating area and a smaller spectrometer size. Short-wave infrared (SWIR) spectroscopy is used in space-based monitoring of greenhouse and pollution gases in the Earth atmosphere. On the extremely large telescopes currently under development, mid-infrared high-resolution spectrographs will, among other things, be used to characterize exo-planet atmospheres. At infrared wavelengths, Silicon is transparent. This means that production methods used in the semiconductor industry can be applied to the fabrication of immersed gratings. Using such methods, we have designed and built immersed gratings for both space- and ground-based instruments, examples being the TROPOMI instrument for the European Space Agency Sentinel-5 precursor mission, Sentinel-5 (ESA) and the METIS (Mid-infrared E-ELT Imager and Spectrograph) instrument for the European Extremely Large Telescope. Three key parameters govern the performance of such gratings: The efficiency, the level of scattered light and the wavefront error induced. In this paper we describe how we can optimize these parameters during the design and manufacturing phase. We focus on the tools and methods used to measure the actual performance realized and present the results. In this paper, the bread-board model (BBM) immersed grating developed for the SWIR-1 channel of Sentinel-5 is used to illustrate this process. Stringent requirements were specified for this grating for the three performance criteria. We will show that -with some margin- the performance requirements have all been met.

  16. Performance Evaluation of Fiber Bragg Gratings at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Juergens, Jeffrey; Adamovsky, Grigory; Floyd, Bertram

    2004-01-01

    The development of integrated fiber optic sensors for smart propulsion systems demands that the sensors be able to perform in extreme environments. In order to use fiber optic sensors effectively in an extreme environment one must have a thorough understanding of the sensor s limits and how it responds under various environmental conditions. The sensor evaluation currently involves examining the performance of fiber Bragg gratings at elevated temperatures. Fiber Bragg gratings (FBG) are periodic variations of the refractive index of an optical fiber. These periodic variations allow the FBG to act as an embedded optical filter passing the majority of light propagating through a fiber while reflecting back a narrow band of the incident light. The peak reflected wavelength of the FBG is known as the Bragg wavelength. Since the period and width of the refractive index variation in the fiber determines the wavelengths that are transmitted and reflected by the grating, any force acting on the fiber that alters the physical structure of the grating will change what wavelengths are transmitted and what wavelengths are reflected by the grating. Both thermal and mechanical forces acting on the grating will alter its physical characteristics allowing the FBG sensor to detect both temperature variations and physical stresses, strain, placed upon it. This ability to sense multiple physical forces makes the FBG a versatile sensor. This paper reports on test results of the performance of FBGs at elevated temperatures. The gratings looked at thus far have been either embedded in polymer matrix materials or freestanding with the primary focus of this paper being on the freestanding FBGs. Throughout the evaluation process, various parameters of the FBGs performance were monitored and recorded. These parameters include the peak Bragg wavelength, the power of the Bragg wavelength, and total power returned by the FBG. Several test samples were subjected to identical test conditions to

  17. Slip Potential for Commonly Used Inclined Grated Metal Walkways

    PubMed Central

    Pollard, Jonisha P.; Heberger, John R.; Dempsey, Patrick G.

    2016-01-01

    Background No specific guidelines or regulations are provided by the Mine Safety and Health Administration for the use of inclined grated metal walkways in mining plants. Mining and other companies may be using walkway materials that do not provide sufficient friction, contributing to slip and fall injuries. Purpose The purpose of this study was to determine if there are significant differences in the required friction for different grated metal walkways during walking in diverse conditions. Methods The normalized coefficients of friction were measured for 12 participants while walking up and down an instrumented walkway with different inclinations (0°, 5°, 10°, 15°, and 20°) and with and without the presence of a contaminant (glycerol). Self-reported slip events were recorded and the required coefficients of friction were calculated considering only the anterior/posterior components of the shear forces. Additionally, the available coefficients of friction for these walkway materials were measured at the 0° orientation using a tribometer, with and without the presence of the contaminant, using a boot heel as well as Neolite as the test feet. Results The number of slips increased when the inclination angle reached 10° and above. Of all materials tested, the diamond weave grating was found to have the best performance at all inclines and when contaminated or dry. A high number of slips occurred for the perforated grating and serrated bar grating at 20° when contaminated. Conclusions Results of this study suggest that the diamond weave grating provides significantly better friction compared to serrated bar and perforated gratings, especially at inclines greater than 10°. PMID:26779388

  18. Diffraction of slow neutrons by holographic SiO{sub 2} nanoparticle-polymer composite gratings

    SciTech Connect

    Klepp, J.; Fally, M.; Pruner, C.; Tomita, Y.; Plonka-Spehr, C.; Geltenbort, P.; Ivanov, S.; Manzin, G.; Andersen, K. H.; Kohlbrecher, J.; Ellabban, M. A.

    2011-07-15

    Diffraction experiments with holographic gratings recorded in SiO{sub 2} nanoparticle-polymer composites have been carried out with slow neutrons. The influence of parameters such as nanoparticle concentration, grating thickness, and grating spacing on the neutron-optical properties of such materials has been tested. Decay of the grating structure along the sample depth due to disturbance of the recording process becomes an issue at grating thicknesses of about 100 microns and larger. This limits the achievable diffraction efficiency for neutrons. As a solution to this problem, the Pendelloesung interference effect in holographic gratings has been exploited to reach a diffraction efficiency of 83% for very cold neutrons.

  19. Fiber Bragg Grating Sensors: Industrial Applications

    NASA Astrophysics Data System (ADS)

    Ambrosino, Carmen; Iadicicco, Agostino; Campopiano, Stefania; Cutolo, Antonello; Giordano, Michele; Cusanoa, Andrea

    Over the last few years, optical fiber sensors have seen increased acceptance and widespread use for a variety of applications. Among the large number of fiber optic sensing configurations, Fiber Bragg Grating (FBG) based sensors, more than any other particular sensor type, have become widely known and popular within and out the photonics community and seen a rise in their utilization and commercial growth. The capability of FBGs to measure a multitude of parameters such as strain, temperature and pressure and many others coupled with their flexibility of design to be used as single point or multi-point sensing arrays and their relative low cost, make them ideal devices to be adopted for a multitude of different sensing applications and implemented in different fields and industries. This work, involving the present and next chapter, reports on recent FBG sensing applications in several industrial fields. In particular, we first summarize the FBG major milestones of their technological evolution in thirty years from the discovery of Kenneth Hill in 1978 and then focus the attention on FBG recent application in civil engineering. We also report on FBG applications in aerospace, energy, oil and gas, transportation and underwater industrial fields. In particular relevant works ranging from structural sensing and health monitoring of composites and structures in aeronautic areas, to pressure and temperature sensors for oil and gas reservoir monitoring, to acoustic sensors for underwater applications, to high voltage and high current sensing systems for the power industry to name just a few, proposed by research groups and industries in last years are discussed.

  20. Spectral calibration for convex grating imaging spectrometer

    NASA Astrophysics Data System (ADS)

    Zhou, Jiankang; Chen, Xinhua; Ji, Yiqun; Chen, Yuheng; Shen, Weimin

    2013-12-01

    Spectral calibration of imaging spectrometer plays an important role for acquiring target accurate spectrum. There are two spectral calibration types in essence, the wavelength scanning and characteristic line sampling. Only the calibrated pixel is used for the wavelength scanning methods and he spectral response function (SRF) is constructed by the calibrated pixel itself. The different wavelength can be generated by the monochromator. The SRF is constructed by adjacent pixels of the calibrated one for the characteristic line sampling methods. And the pixels are illuminated by the narrow spectrum line and the center wavelength of the spectral line is exactly known. The calibration result comes from scanning method is precise, but it takes much time and data to deal with. The wavelength scanning method cannot be used in field or space environment. The characteristic line sampling method is simple, but the calibration precision is not easy to confirm. The standard spectroscopic lamp is used to calibrate our manufactured convex grating imaging spectrometer which has Offner concentric structure and can supply high resolution and uniform spectral signal. Gaussian fitting algorithm is used to determine the center position and the Full-Width-Half-Maximum(FWHM)of the characteristic spectrum line. The central wavelengths and FWHMs of spectral pixels are calibrated by cubic polynomial fitting. By setting a fitting error thresh hold and abandoning the maximum deviation point, an optimization calculation is achieved. The integrated calibration experiment equipment for spectral calibration is developed to enhance calibration efficiency. The spectral calibration result comes from spectral lamp method are verified by monochromator wavelength scanning calibration technique. The result shows that spectral calibration uncertainty of FWHM and center wavelength are both less than 0.08nm, or 5.2% of spectral FWHM.

  1. Fabricating Blazed Diffraction Gratings by X-Ray Lithography

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis; Hartley, Frank; Wilson, Daniel

    2004-01-01

    Gray-scale x-ray lithography is undergoing development as a technique for fabricating blazed diffraction gratings. As such, gray-scale x-ray lithography now complements such other grating-fabrication techniques as mechanical ruling, holography, ion etching, laser ablation, laser writing, and electron-beam lithography. Each of these techniques offers advantages and disadvantages for implementing specific grating designs; no single one of these techniques can satisfy the design requirements for all applications. Gray-scale x-ray lithography is expected to be advantageous for making gratings on steeper substrates than those that can be made by electron-beam lithography. This technique is not limited to sawtooth groove profiles and flat substrates: various groove profiles can be generated on arbitrarily shaped (including highly curved) substrates with the same ease as sawtooth profiles can be generated on flat substrates. Moreover, the gratings fabricated by this technique can be made free of ghosts (spurious diffraction components attributable to small spurious periodicities in the locations of grooves). The first step in gray-scale x-ray lithography is to conformally coat a substrate with a suitable photoresist. An x-ray mask (see Figure 1) is generated, placed between the substrate and a source of collimated x-rays, and scanned over the substrate so as to create a spatial modulation in the exposure of the photoresist. Development of the exposed photoresist results in a surface corrugation that corresponds to the spatial modulation and that defines the grating surface. The grating pattern is generated by scanning an appropriately shaped x-ray area mask along the substrate. The mask example of Figure 1 would generate a blazed grating profile when scanned in the perpendicular direction at constant speed, assuming the photoresist responds linearly to incident radiation. If the resist response is nonlinear, then the mask shape can be modified to account for the

  2. Optical high temperature sensor based on fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhang, Bowei

    The aim of this thesis is to fabricate a fiber Bragg grating (FBG) temperature sensor that is capable to measure temperatures in excess of 1100°C. For this purpose, two topics have been studied and investigated during this project. One of them is the development of a high temperature resistant molecular-water induced FBGs; and the other is to investigate the effect of microwave-irradiation on the hydrogen-loaded FBG. The molecular-water induced FBGs are different from the other types of FBG. In these devices the refractive index is modulated by the periodic changes of molecular-water concentration within the grating. The device was developed using thermal annealing technology based on hydrogen-load FBG. Thermal stability of these devices was studied by measuring the grating reflectivity from room temperature to 1000°C. The stability of the device was tested by examining the FBG reflectivity for a period of time at certain temperatures. The results show that these devices are extremely stable at temperatures in excess of 1000°C. The hydroxyl concentration in the grating has been also investigated during this thesis. Based on the knowledge of hydroxyl groups inside FBG, a microwave treatment was designed to increase the hydroxyl concentration in the FBG area. The results show that the molecular-water induced grating, which was fabricated using microwave radiated hydrogen-loaded FBI, are stable at temperatures above 1100°C.

  3. Design of integrated and networked multidimensional grating digital readout

    NASA Astrophysics Data System (ADS)

    Chang, Li; Xu, Hui; Xiu, Guoyi

    2008-10-01

    The grating digital readout is the key measurement feedback device of the numerical control system and base of the equipment manufacturing industry. With the development of the complex machining, the multi-axis linkage is a new direction of the numerical control system, which needs the multidimensional measurement. Based on all digital grating moiré fringe subdivision theory, the paper introduces the design of integrated and networked multidimensional grating digital readout with an embedded system-on-chip ZA7V that is a complete field configurable system-on-chip with a 32- bit ARM7TDMI processor core, a programmable logic matrix, a robust memory subsystem and a high-performance dedicated internal bus. Networked functions include Ethernet interface, CAN bus interface, USB bus interface and GPRS interface so that the grating digital readout can access the device network, workshop network, intranet network and Internet. The simulation results and experimental data prove that the realization of the integrated and networked multidimensional grating digital readout. It will be widely used in the numerical control system and machining center.

  4. Quantitative examination of out-of-phase mixed holographic gratings

    NASA Astrophysics Data System (ADS)

    Voit, Kay-Michael; Bruening, Hauke; Imlau, Mirco

    2012-02-01

    Modern holographic applications require advanced photosensitive materials that particularly obey alterations of the complex permittivity with pronounced amplitudes of both real and imaginary parts on the sub-ps-time scale. Promising candidates such as amorphous and crystalline materials remarkably show a mutual phase-shift between phase and absorption gratings that complicates the analysis of the underlying wave-coupling mechanisms. Hence, theoretical descriptions that are simply based on Kogelnik's coupled-wave theory can not be applied, i.e., a formal approach to systematically derive the full parameter space of the gratings from diffraction efficiency measurements is missing in literature. We revised the analysis of the wave-coupling theory omitting former approximations or applying them later. As a result we derived a formal description for mixed gratings allowing for a full description of beam-coupling experiments. Both the modulations of the refractive index and the absorption coefficient as well as the phase shift between these gratings can be determined through measurements of the angular dependent diffraction efficiency around the positive and the negative Bragg angle. Our approach and results are demonstrated along a mixed grating with a most common parameter set.

  5. Electrically tunable holographic polymer templated blue phase liquid crystal grating

    NASA Astrophysics Data System (ADS)

    He, Zheng-Hong; Chen, Chao-Ping; Zhu, Ji-Liang; Yuan, Ya-Chao; Li, Yan; Hu, Wei; Li, Xiao; Li, Hong-Jing; Lu, Jian-Gang; Su, Yi-Kai

    2015-06-01

    In this paper, we demonstrate an alternative approach to fabricating an electrically tunable holographic polymer templated blue phase liquid crystal grating. This grating is obtained by preforming a polymer template comprised of periodic fringes, and then refilling it with a blue phase liquid crystal. Compared with conventional holographic polymer dispersed liquid crystal gratings, our grating can remarkably reduce its switching voltage from 200 V to 43 V while maintaining a sub-millisecond response time. The holographic polymer templated blue phase liquid crystal (HPTBPLC) grating is free from electrode patterning, thus leading to a lower cost and more flexible applications. Project supported by the National Basic Research Program of China (Grant No. 2013CB328804), the National Natural Science Foundation of China (Grant No. 61307028), the Funds from the Science and Technology Commission of Shanghai Municipality (Grant Nos. 11JC1405300, 13ZR1420000, and 14ZR1422300), and the Fundamental Research Funds for the Central Universities, China (Grant No. XDJK 2011C047).

  6. Liquid crystal gratings from nematic to blue phase

    NASA Astrophysics Data System (ADS)

    Lu, Yan-qing; Hu, Wei; Lin, Xiao-wen; Srivastava, Abhishek; Chigrinov, Vladimir G.

    2012-10-01

    Some of our recent progress on liquid crystal (LC) gratings, from nematic to blue phase, is reviewed in this invited talk. The first kind of grating is fabricated by periodically adjusting the LC directors to form alternate micro phase retarders and polarization rotators in a cell placed between crossed polarizers. The second one is demonstrated by means of photoalignment technique with alternate orthogonal homogeneously-aligned domains. To improve the response time of the gratings, several approaches are also proposed by using dual-frequency addressed nematic LC, ferroelectric LC and blue phase LC, which shows great performance including high transmittance, polarization independency and submillisecond response. At last, to obtain other controllable LC microstructures rather than simple 1D/2D gratings, we develop a micro-lithography system with a digital micro-mirror device as dynamic mask forms. It may instantly generate arbitrary micro-images on photoalignment layers and further guides the LC molecule orientations. Besides normal phase gratings, more complex patterns such as quasicrystal structures are demonstrated. Some new applications such as tunable multiport optical switching and vector beam generations are expected.

  7. Broadband enhanced transmission of acoustic waves through serrated metal gratings

    NASA Astrophysics Data System (ADS)

    Qi, Dong-Xiang; Fan, Ren-Hao; Deng, Yu-Qiang; Peng, Ru-Wen; Wang, Mu; Jiangnan University Collaboration

    In this talk, we present our studies on broadband properties of acoustic waves through metal gratings. We have demonstrated that serrated metal gratings, which introduce gradient coatings, can give rise to broadband transmission enhancement of acoustic waves. Here, we have experimentally and theoretically studied the acoustic transmission properties of metal gratings with or without serrated boundaries. The average transmission is obviously enhanced for serrated metal gratings within a wide frequency range, while the Fabry-Perot resonance is significantly suppressed. An effective medium hypothesis with varying acoustic impedance is proposed to analyze the mechanism, which was verified through comparison with finite-element simulation. The serrated boundary supplies gradient mass distribution and gradient normal acoustic impedance, which could efficiently reduce the boundary reflection. Further, by increasing the region of the serrated boundary, we present a broadband high-transmission grating for wide range of incident angle. Our results may have potential applications to broadband acoustic imaging, acoustic sensing and new acoustic devices. References: [1] Dong-Xiang Qi, Yu-Qiang Deng, Di-Hu Xu, Ren-Hao Fan, Ru-Wen Peng, Ze-Guo Chen, Ming-Hui Lu, X. R. Huang and Mu Wang, Appl. Phys. Lett. 106, 011906 (2015); [2] Dong-Xiang Qi, Ren-Hao Fan, Ru-Wen Peng, Xian-Rong Huang, Ming-Hui Lu, Xu Ni, Qing Hu, and Mu Wang, Applied Physics Letters 101, 061912 (2012).

  8. Continuous wavelength tunable laser source with optimum positioning of pivot axis for grating

    DOEpatents

    Pushkarsky, Michael; Amone, David F.

    2010-06-08

    A laser source (10) for generating a continuously wavelength tunable light (12) includes a gain media (16), an optical output coupler (36F), a cavity collimator (38A), a diffraction grating (30), a grating beam (54), and a beam attacher (56). The diffraction grating (30) is spaced apart from the cavity collimator (38A) and the grating (30) cooperates with the optical output coupler (36F) to define an external cavity (32). The grating (30) includes a grating face surface (42A) that is in a grating plane (42B). The beam attacher (56) retains the grating beam (54) and allows the grating beam (54) and the grating (30) to effectively pivot about a pivot axis (33) that is located approximately at an intersection of a pivot plane (50) and the grating plane (42B). As provided herein, the diffraction grating (30) can be pivoted about the unique pivot axis (33) to move the diffraction grating (30) relative to the gain media (16) to continuously tune the lasing frequency of the external cavity (32) and the wavelength of the output light (12) so that the output light (12) is mode hop free.

  9. [Technology Development for X-Ray Reflection for the Constellation-X Reflection Grating Spectrometer (RGS)

    NASA Technical Reports Server (NTRS)

    Schattenburg, Mark L.

    2003-01-01

    This Grant covers MIT support for the technology development of x-ray reflection gratings for the Constellation-X Reflection Grating Spectrometer (RGS). Since the start of the Grant MIT has extended its previously-developed patterning and super-smooth, blazed grating fabrication technology to ten-times smaller grating periods and ten-times larger blaze angles to demonstrate feasibility and performance in the off-plane grating geometry. In the past year we successfully developed several nanoimprint grating replication methods that achieved very high fidelity replication of master silicon gratings. Grating geometry on the nano and macro scales were faithfully replicated, demonstrating the viability of the process for manufacturing the thousands of gratings required for the RGS. We also successfully developed an improved metrology truss for holding test grating substrates during metrology. The flatness goal of grating substrates is under 500 nm. In the past, grating holders would cause non-repeatable distortion of >> 500 nm to the substrates due to friction and gravity sag. The new holder has a repeatability of under 50 nm which is adequate for the proposed RGS grating substrates.

  10. Volume phase holographic gratings for the Subaru Prime Focus Spectrograph: performance measurements of the prototype grating set

    NASA Astrophysics Data System (ADS)

    Barkhouser, Robert H.; Arns, James; Gunn, James E.

    2014-08-01

    The Prime Focus Spectrograph (PFS) is a major instrument under development for the 8.2 m Subaru telescope on Mauna Kea. Four identical, fixed spectrograph modules are located in a room above one Nasmyth focus. A 55 m fiber optic cable feeds light into the spectrographs from a robotic fiber positioner mounted at the telescope prime focus, behind the wide field corrector developed for Hyper Suprime-Cam. The positioner contains 2400 fibers and covers a 1.3 degree hexagonal field of view. Each spectrograph module will be capable of simultaneously acquiring 600 spectra. The spectrograph optical design consists of a Schmidt collimator, two dichroic beamsplitters to separate the light into three channels, and for each channel a volume phase holographic (VPH) grating and a dual- corrector, modified Schmidt reimaging camera. This design provides a 275 mm collimated beam diameter, wide simultaneous wavelength coverage from 380 nm to 1.26 µm, and good imaging performance at the fast f/1.1 focal ratio required from the cameras to avoid oversampling the fibers. The three channels are designated as the blue, red, and near-infrared (NIR), and cover the bandpasses 380-650 nm (blue), 630-970 nm (red), and 0.94-1.26 µm (NIR). A mosaic of two Hamamatsu 2k×4k, 15 µm pixel CCDs records the spectra in the blue and red channels, while the NIR channel employs a 4k×4k, substrate-removed HAWAII-4RG array from Teledyne, with 15 µm pixels and a 1.7 µm wavelength cutoff. VPH gratings have become the dispersing element of choice for moderate-resolution astronomical spectro- graphs due their potential for very high diffraction efficiency, low scattered light, and the more compact instru- ment designs offered by transmissive dispersers. High quality VPH gratings are now routinely being produced in the sizes required for instruments on large telescopes. These factors made VPH gratings an obvious choice for PFS. In order to reduce risk to the project, as well as fully exploit the performance

  11. Design and integration of a mechanism for focusing and alignment of the Echelle spectrograph for the telescope of 2.1 meters of the National Astronomic Observatory

    NASA Astrophysics Data System (ADS)

    Gutiérrez, Horacio O. A.; Farah, Alejandro S.; Echevarria R., Juan M.; Sierra, Gerardo D.

    2014-08-01

    This paper is focused on an engineering project applied to astronomy for scientific purposes. The project consisted elementally on the design, fabrication and characterization of an interface or mechanism to align and focus the lens of the Echelle spectrograph and its CCD camera. This instrument is part of the 2.1 m telescope of the Observatorio Astronómico Nacional located at the Sierra de San Pedro Martir, B. C., Mexico (OAN-SPM). The mechanism described in this article is composed functionally of the next pieces: two half- clamps, three profiles type "L" (that function as support columns), a fixed plate, a reference sliding plate, and three digital sensors for measuring the relative position between the camera interface of the spectrograph and the plane of its dewar. The cryostat system has a lens that must be focused and aligned with the spectrograph. The cryostat and the mechanism have to be attached and it has to allow rotational movements around the three axes with linear adjustments along them. Similarly there is a brief description of the adjacent elements to understand the mechanism and functionality design criteria used in order to ensure the proper functionality of the mechanism that has been tested and integrated in the telescope. Such results are also described as well as the technical specifications, the manufacturing process and the manufacturing drawings. A brief description of the scientific instrument and some finite element simulations are also included in this work. Finally, some recommendations and future work that may be carried out as a continuous improvement mechanism are presented.

  12. Comparison of angular movement measurement using grating and laser interferometer

    NASA Astrophysics Data System (ADS)

    Peng, Jun

    2008-06-01

    Primary angular acceleration calibration system is developed by Changcheng Institute of Metrology and Measurement (CIMM) to generate angular vibration and shock, which are traceable to the International System of Units (SI). It can be used to calibrate angular transducers, i.e. angular accelerometer, angular velocity transducer, and rotational angle transducer. Two kinds of system are used in the measurement of angular movement, one is based on circular grating and scanning heads, another is based on laser interferometer with diffraction grating. This paper introduce the comparison results of the two measurement systems in the measurement of angular movement under sinusoidal and shock excitation. The results of the investigations show a good accordance of the newly developed method of using grating and scanning heads measuring angular acceleration in comparison with the laser interferometer method.

  13. Research on the fire alarming system of fiber grating

    NASA Astrophysics Data System (ADS)

    Qi, Yaobin

    2007-09-01

    The application of fiber grating sensing technology in fire alarming based on temperature detection has the advantages of high accuracy, high reliability and strong immunity from electronic and magnetic fields. It is especially advantageous to use this system in the petroleum and chemistry industry because it can provide an extraordinary safe means for the fire alarm. But due to the traditional optical Wavelength Division Multiplexing (WDM) technology is limited by the optic source bandwidth, the number of its multiplexing points is few. In this paper WDM technology will be developed mixing with Identified Bragg, which is called Identified and Wavelength Multiplexing, to build the Fiber Grating (FBG) fire alarm system integrated with computers. Some technologies applied in fire alarming system of fiber grating such as the transmission of test signals which pass through modulate and demodulate, the disposal of software system, the output of control signal and the strong ability of anti-disturbance have been studied and discussed.

  14. Applications of laser-induced gratings to spectroscopy and dynamics

    SciTech Connect

    Rohlfing, E.A.

    1993-12-01

    This program has traditionally emphasized two principal areas of research. The first is the spectroscopic characterization of large-amplitude motion on the ground-state potential surface of small, transient molecules. The second is the reactivity of carbonaceous clusters and its relevance to soot and fullerene formation in combustion. Motivated initially by the desire to find improved methods of obtaining stimulated emission pumping (SEP) spectra of transients, most of our recent work has centered on the use of laser-induced gratings or resonant four-wave mixing in free-jet expansions. These techniques show great promise for several chemical applications, including molecular spectroscopy and photodissociation dynamics. The author describes recent applications of two-color laser-induced grating spectroscopy (LIGS) to obtain background-free SEP spectra of transients and double resonance spectra of nonfluorescing species, and the use of photofragment transient gratings to probe photodissociation dynamics.

  15. Embedded fiber optic Bragg grating (FBG) detonation velocity sensor

    NASA Astrophysics Data System (ADS)

    Benterou, Jerry; Bennett, Corey V.; Cole, Garrett; Hare, D. E.; May, Chadd; Udd, Eric; Mihailov, Stephen J.; Lu, Ping

    2009-05-01

    In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation models and detonation models of high explosives, the ability to continuously measure the detonation velocity within an explosive is required. Progress on an embedded velocity diagnostic using a 125 micron diameter optical fiber containing a chirped fiber Bragg grating is reported. As the chirped fiber Bragg grating is consumed by the moving detonation wave, the physical length of the unconsumed Bragg grating is monitored with a fast InGaAs photodiode. Experimental details of the associated equipment and data in the form of continuous detonation velocity records within PBX-9502 are presented. This small diameter fiber sensor has the potential to measure internal detonation velocities on the order of 10 mm/μsec along path lengths tens of millimeters long.

  16. EUV-multilayers on grating-like topographies

    SciTech Connect

    van Boogaard, A. J. R.; Louis, E.; Goldberg, K. A.; Mochi, I.; Bijkerk, F.

    2010-03-12

    In this study, multilayer morphology near the key anomalies in grating-like structures, namely sharp step-edges and steep walls, are examined. Different deposition schemes are employed. Based on cross section TEM analysis an explanatory model describing the morphology of the successive layers is developed. A further insight into the periodicity and the general performance of the multilayer is obtained by EUV microscopy. The main distortions in multilayer structure and hence EUV performance are found to be restricted to a region within a few hundred nanometers from the anomalies, which is very small compared to the proposed grating period (50-100 {micro}m). These multilayer coated blazed gratings can thus be considered a viable option for spectral purity enhancement of EUV light sources.

  17. Vibrational spectroscopy at electrolyte/electrode interfaces with graphene gratings

    PubMed Central

    Bie, Ya-Qing; Horng, Jason; Shi, Zhiwen; Ju, Long; Zhou, Qin; Zettl, Alex; Yu, Dapeng; Wang, Feng

    2015-01-01

    Microscopic understanding of physical and electrochemical processes at electrolyte/electrode interfaces is critical for applications ranging from batteries, fuel cells to electrocatalysis. However, probing such buried interfacial processes is experimentally challenging. Infrared spectroscopy is sensitive to molecule vibrational signatures, yet to approach the interface three stringent requirements have to be met: interface specificity, sub-monolayer molecular detection sensitivity, and electrochemically stable and infrared transparent electrodes. Here we show that transparent graphene gratings electrode provide an attractive platform for vibrational spectroscopy at the electrolyte/electrode interfaces: infrared diffraction from graphene gratings offers enhanced detection sensitivity and interface specificity. We demonstrate the vibrational spectroscopy of methylene group of adsorbed sub-monolayer cetrimonium bromide molecules and reveal a reversible field-induced electrochemical deposition of cetrimonium bromide on the electrode controlled by the bias voltage. Such vibrational spectroscopy with graphene gratings is promising for real time and in situ monitoring of different chemical species at the electrolyte/electrode interfaces. PMID:26123807

  18. Launching focused surface plasmon in circular metallic grating

    SciTech Connect

    Kumar, Pawan; Tripathi, V. K.; Kumar, Ashok; Shao, X.

    2015-01-07

    The excitation of focused surface plasma wave (SPW) over a metal–vacuum interface embedded with circular surface grating is investigated theoretically. The normally impinged radiation imparts oscillatory velocity to free electrons that beats with the surface ripple to produce a nonlinear current, driving the SPW. As SPW propagates, it gets focused. The focused radiation has a maximum at the centre of grating and decreases beyond the centre due to diffraction. The amplitude of SPW is fixed for a given groove depth and increases rapidly around the resonance frequency. The intensity at the focus point depends on dimensions of the grating. It increases with the radiation frequency approaching the surface plasmon resonance. The scheme has potential applications for photonic devices and surface enhanced Raman scattering.

  19. Volume phase holographic gratings for astronomy based on solid photopolymers

    NASA Astrophysics Data System (ADS)

    Zanutta, Alessio; Bianco, Andrea; Insausti, Maider; Garzón, Francisco

    2014-07-01

    Volume Phase Holographic Gratings (VPHG) are gaining more and more interest as optical dispersing elements in new astronomical spectrographs at low and medium resolution. A key point is the development of new photosensitive materials suitable to produce VPHGs that match the stringent requirements of the astronomical environment. Here we report on the performances of VPHG based on Bayfol®HX solid photopolymer films developed by Bayer MaterialScience AG. Parameters affecting the grating efficiency (e. g. photopolymer film thickness and refractive index modulation) are measured and linked to the performances of VPHG working in the VIS-NIR region. Moreover, the behavior at low temperature and the aging properties of such materials/gratings are reported. Substantial efficiency gains on a new VPHG installed at the Asiago's spectrograph are shown and proven on the observation of a standard star (hr5501).

  20. Ultrasonic Diffraction Grating Spectroscopy and Characterization of Fluids and Slurries.

    SciTech Connect

    Greenwood, Margaret S.; Brodsky, Anatol; Burgess, Lloyd; Bond, Leonard J.; Hamad, Mazen

    2004-04-01

    The ultrasonic diffraction grating is formed by machining triangular grooves, 300 microns apart, on a stainless steel surface. The grating surface is in contact with the liquid or slurry. The ultrasonic beam, traveling in the solid, strikes the back of the grating and produces a transmitted m = 1 beam in the liquid. The angle of this beam in the liquid increases with decreasing frequency and the critical frequency FCR occurs when the angle is 90{sup o}. At frequencies below FCR, this m = 1 wave does not exist and its energy is shared with other types of waves. The signal of the reflected m = 0 wave is observed and an increase is observed at FCR. This information yields the velocity of sound in the liquid and particle size.

  1. Diffraction of Gaussian beams on intracavity Bragg gratings

    NASA Astrophysics Data System (ADS)

    Bitauld, David; Menez, Ludivine; Zaquine, Isabelle; Maruani, Alain; Frey, Robert

    2005-06-01

    The diffraction of Gaussian beams on intracavity Bragg gratings is analyzed theoretically. For reasonable waists the associated beam divergence does not significantly influence the diffraction efficiency of such devices. Nevertheless, the tilt angle of the incident beam, imposed by the Bragg resonance condition, strongly reduces the diffraction efficiency at short grating periods. However, the angular selectivity can be maintained if the Fabry-Perot cavity is tuned to the incident beam direction, which allows the use of small-volume holograms together with a dense angular multiplex. This theoretical analysis can be applied to the optimization of the diffraction properties of Gaussian beams on any intracavity Bragg grating, which could then be used for free-space parallel signal processing.

  2. Design of plasmonic circular grating with broadband absorption enhancements

    NASA Astrophysics Data System (ADS)

    Chiu, Nan-Fu; Yang, Cheng-Du; Kao, Yi-Lun; Cheng, Chih-Jen

    2015-05-01

    We have investigated the effect of concentric circles geometry on the performance of focusing plasmonic circular grating (PCG)-coupled surface-omnidirectional absorption. We wish to highlight the essential characteristics of plasmonic circular grating nanostructure to assist researchers in developing and advancing suitable organic solar cells (OSC) for unique applications. Exactly how plasmonic enhancement and the absorption characteristics of the organic materials (P3HT:PCBM and PEDOT:PSS) interact with each other is also examined. We present experimental studies of broadband absorption enhancement in PCG structure. We show that the PCG structure can result in broadband absorption enhancement, the overall optical absorption in organic film can be greatly enhanced up to ~111.2 % compared to the planar device without grating.

  3. Diffraction light analysis method for a diffraction grating imaging lens.

    PubMed

    Ando, Takamasa; Korenaga, Tsuguhiro; Suzuki, Masa-aki; Tanida, Jun

    2014-04-10

    We have developed a new method to analyze the amount and distribution of diffraction light for a diffraction grating lens. We have found that diffraction light includes each-order diffraction light and striped diffraction light. In this paper, we describe characteristics of striped diffraction light and suggest a way to analyze diffraction light. Our analysis method, which considers the structure of diffraction grating steps, can simulate the aberrations of an optical system, each-order diffraction light, and striped diffraction light simultaneously with high accuracy. A comparison between the simulation and experimental results is presented, and we also show how our analysis method can be used to optimize a diffraction grating lens with low flare light.

  4. Rectangular Relief Diffraction Gratings for Coherent Lidar Beam Scanning

    NASA Technical Reports Server (NTRS)

    Cole, H. J.; Chambers, D. M.; Dixit, S. N.; Britten, J. A.; Shore, B. W.; Kavaya, M. J.

    1999-01-01

    The application of specialized rectangular relief transmission gratings to coherent lidar beam scanning is presented. Two types of surface relief transmission grating approaches are studied with an eye toward potential insertion of a constant thickness, diffractive scanner where refractive wedges now exist. The first diffractive approach uses vertically oriented relief structure in the surface of an optical flat; illumination of the diffractive scanner is off-normal in nature. The second grating design case describes rectangular relief structure slanted at a prescribed angle with respect to the surface. In this case, illumination is normal to the diffractive scanner. In both cases, performance predictions for 2.0 micron, circularly polarized light at beam deflection angles of 30 or 45 degrees are presented.

  5. Germanium implanted Bragg gratings in silicon on insulator waveguides

    NASA Astrophysics Data System (ADS)

    Loiacono, Renzo; Reed, Graham T.; Gwilliam, Russell; Mashanovich, Goran Z.; O'Faolain, Liam; Krauss, Thomas; Lulli, Giorgio; Jeynes, Chris; Jones, Richard

    2010-02-01

    Integrated Bragg gratings are an interesting candidate for waveguide coupling, telecommunication applications, and for the fabrication of integrated photonic sensors. These devices have a high potential for optical integration and are compatible with CMOS processing techniques if compared to their optical fibre counterpart. In this work we present design, fabrication, and testing of Germanium ion implanted Bragg gratings in silicon on insulator (SOI). A periodic refractive index modulation is produced in a 1μm wide SOI rib waveguide by implanting Germanium ions through an SiO2 hardmask. The implantation conditions have been analysed by 3D ion implantation modelling and the induced refractive index change has been investigated on implanted samples by Rutherford Backscattering Spectroscopy (RBS) and ellipsometry analysis. An extinction ratio of up to 30dB in transmission, around the 1.55μm wavelength, has been demonstrated for Germanium implanted gratings on SOI waveguides.

  6. Diffraction grating interferometers for mechanical characterisations of advanced fabric laminates

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ryul; Molimard, Jérôme; Vautrin, Alain; Surrel, Yves

    2006-02-01

    It is demonstrated that two grating interferometers with high spatial resolutions can successfully be applied for the mechanical characterisation of the advanced fabric composite materials. Based on these two techniques, the mechanical properties of two kinds of fabric laminates are obtained without assumption of uniform strain fields to be used in the characterisation approaches using the local strain sensors. The degree of the yarn crimp effects of the two laminates is compared in terms of the out-of-plane displacement derivatives. Especially, it is shown that the grating shearing interferometer is appropriate for the crimped fabric structure requiring a three-dimensional analysis. The modification from moiré interferometer to grating shearing interferometer is performed by introducing a Michelson interferometer modified for image shearing.

  7. The in-focus variable line spacing plane grating monochromator

    NASA Astrophysics Data System (ADS)

    Reininger, R.

    2011-09-01

    The in-focus variable line spacing plane grating monochromator is based on only two plane optical elements, a variable line spacing plane grating and a plane pre-mirror that illuminates the grating at the angle of incidence that will focus the required photon energy. A high throughput beamline requires only a third optical element after the exit slit, an aberration corrected elliptical toroid. Since plane elements can be manufactured with the smallest figure errors, this monochromator design can achieve very high resolving power. Furthermore, this optical design can correct the deformations induced by the heat load on the optics along the dispersion plane. This should allow obtaining a resolution of 10 meV at 1 keV with currently achievable figure errors on plane optics. The position of the photon source when an insertion device center is not located at the center of the straight section, a common occurrence in new insertion device beamlines, is investigated.

  8. Formation and Applications of the Secondary Fiber Bragg Grating

    PubMed Central

    Guan, Bai-Ou; Ran, Yang; Feng, Fu-Rong; Jin, Long

    2017-01-01

    Being one of the most proven fiber optic devices, the fiber Bragg grating has developed continually to extend its applications, particularly in extreme environments. Accompanying the growth of Type-IIa Bragg gratings in some active fibers, a new resonance appears at the shorter wavelength. This new type of grating was named “secondary Bragg grating” (SBG). This paper describes the formation and applications of the SBGs. The formation of the SBG is attributed to the intracore Talbot-type-fringes as a result of multi-order diffractions of the inscribing beams. The SBG presents a variety of interesting characteristics, including dip merge, high-temperature resistance, distinct temperature response, and the strong higher-order harmonic reflection. These features enable its promising applications in fiber lasers and fiber sensing technology. PMID:28218697

  9. Gaussian Schell-model beams propagating through polarization gratings.

    PubMed

    Piquero, G; Borghi, R; Santarsiero, M

    2001-06-01

    The effects of polarization gratings on partially coherent beams are investigated by studying a Gaussian Schell-model beam impinging on a linear polarizer whose transmission axis varies periodically along one transverse direction. Analytical expressions for the beam polarization-coherence matrix after the grating are obtained. In particular, the evolution of the degree of polarization upon propagation is analyzed. Different behaviors of the output beam, depending on the beam parameters and on the period of the grating, are exhibited. In particular, it is shown that, by suitably choosing the latter quantities, it is possible to obtain not only any desirable value of the degree of polarization of the output beam but also particular distributions of such parameters across the transverse sections of the beam.

  10. Three-dimensional grating nanowires for enhanced light trapping.

    PubMed

    Lee, Hoo-Cheol; Na, Jin-Young; Moon, Yoon-Jong; Park, Jin-Sung; Ee, Ho-Seok; Park, Hong-Gyu; Kim, Sun-Kyung

    2016-04-01

    We propose rationally designed 3D grating nanowires for boosting light-matter interactions. Full-vectorial simulations show that grating nanowires sustain high-amplitude waveguide modes and induce a strong optical antenna effect, which leads to an enhancement in nanowire absorption at specific or broadband wavelengths. Analyses of mode profiles and scattering spectra verify that periodic shells convert a normal plane wave into trapped waveguide modes, thus giving rise to scattering dips. A 200 nm diameter crystalline Si nanowire with designed periodic shells yields an enormously large current density of ∼28  mA/cm2 together with an absorption efficiency exceeding unity at infrared wavelengths. The grating nanowires studied herein will provide an extremely efficient absorption platform for photovoltaic devices and color-sensitive photodetectors.

  11. Photofabrication of surface relief gratings using post functionalized azo polymers

    SciTech Connect

    Tripathy, S.K.; Kumar, J.; Kim, D.Y.; Jiang, X.; Wang, X.; Li, L.; Sukwattanasinitt, M.; Sandman, D.J.

    1998-07-01

    A series of azobenzene funtionalized polymers has been synthesized by post polymerization azo coupling reaction. Photo-fabrication of surface relief gratings were studied on the polymer films. Epoxy based azo polymers were prepared by post azo coupling reaction to form polymers containing donor-acceptor type azo chromophores. The azo chromophores were designed to contain ionizable groups to impart self-assembling and photoprocessing capabilities to the polymers. The polymers containing 4-(4-(carboxylic acid)phenylazo)aniline chromophores can be directly photofabricated to form surface relief gratings with large surface modulations. Charge interactions had a strong influence on the details of the writing process. A new soluble polydiacetylene, post-functionalized with azobenzene groups was also prepared. Large amplitude surface gratings could be fabricated on this polydiacetylene film as well.

  12. Round Robin for Optical Fiber Bragg Grating Metrology.

    PubMed

    Rose, A H; Wang, C M; Dyer, S D

    2000-01-01

    NIST has administered the first round robin of measurements for optical fiber Bragg gratings. We compared the measurement of center wavelength, bandwidth, isolation, minimum relative transmittance, and relative group delay among several grating types in two industry groups, telecommunications and sensors. We found that the state of fiber Bragg grating metrology needs improvement in most areas. Specifically, when tunable lasers are used a filter is needed to remove broadband emissions from the laser. The linear slope of relative group delay measurements is sensitive to drift and systematic bias in the rf-modulation technique. The center wavelength measurement had a range of about 27 pm in the sensors group and is not adequate to support long-term structural monitoring applications.

  13. Machined immersion grating with theoretically predicted diffraction efficiency.

    PubMed

    Ikeda, Yuji; Kobayashi, Naoto; Sarugaku, Yuki; Sukegawa, Takashi; Sugiyama, Shigeru; Kaji, Sayumi; Nakanishi, Kenshi; Kondo, Sohei; Yasui, Chikako; Kataza, Hirokazu; Nakagawa, Takao; Kawakita, Hideyo

    2015-06-01

    An immersion grating composed of a transmissive material with a high refractive index (n>2) is a powerful device for high-resolution spectroscopy in the infrared region. Although the original idea is attributed to Fraunhofer about 200 years ago, an immersion grating with high diffraction efficiency has never been realized due to the difficulty in processing infrared crystals that are mostly brittle. While anisotropic etching is one successful method for fabricating a fine groove pattern on Si crystal, machining is necessary for realizing the ideal groove shape on any kind of infrared crystal. In this paper, we report the realization of the first, to the best of our knowledge, machined immersion grating made of single-crystal CdZnTe with a high diffraction efficiency that is almost identical to that theoretically predicted by rigorous coupled-wave analysis.

  14. Exposed core microstructured optical fiber Bragg gratings: refractive index sensing.

    PubMed

    Warren-Smith, Stephen C; Monro, Tanya M

    2014-01-27

    Bragg gratings have been written in exposed-core microstructured optical fibers for the first time using a femtosecond laser. Second and third order gratings have been written and both show strong reflectivity at 1550 nm, with bandwidths as narrow as 60 pm. Due to the penetration of the guided field outside the fiber the Bragg reflections are sensitive to the external refractive index. As different modes have different sensitivities to refractive index but the same temperature sensitivity the sensor can provide temperature-compensated refractive index measurements. Since these Bragg gratings have been formed by physical ablation, these devices can also be used for high temperature sensing, demonstrated here up to 800°C. The fibers have been spliced to single mode fiber for improved handling and integration with commercial interrogation units.

  15. Rayleigh–Bloch waves along elastic diffraction gratings

    PubMed Central

    Colquitt, D. J.; Craster, R. V.; Antonakakis, T.; Guenneau, S.

    2015-01-01

    Rayleigh–Bloch (RB) waves in elasticity, in contrast to those in scalar wave systems, appear to have had little attention. Despite the importance of RB waves in applications, their connections to trapped modes and the ubiquitous nature of diffraction gratings, there has been no investigation of whether such waves occur within elastic diffraction gratings for the in-plane vector elastic system. We identify boundary conditions that support such waves and numerical simulations confirm their presence. An asymptotic technique is also developed to generate effective medium homogenized equations for the grating that allows us to replace the detailed microstructure by a continuum representation. Further numerical simulations confirm that the asymptotic scheme captures the essential features of these waves. PMID:25568616

  16. Moth's eye anti-reflection gratings on germanium freeform surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Meng; Shultz, Jason A.; Owen, Joseph D.; Davies, Matthew A.; Suleski, Thomas J.

    2014-09-01

    Germanium is commonly used for optical components in the infrared, but the high refractive index of germanium causes significant losses due to Fresnel reflections. Anti-reflection (AR) surfaces based on subwavelength "moth's eye" gratings provide one means to significantly increase optical transmission. As found in nature, these gratings are conformal to the curved surfaces of lenslets in the eye of the moth. Engineered optical systems inspired by biological examples offer possibilities for increased performance and system miniaturization, but also introduce significant challenges to both design and fabrication. In this paper, we consider the design and fabrication of conformal moth's eye AR structures on germanium freeform optical surfaces, including lens arrays and Alvarez lenses. Fabrication approaches and limitations based on both lithography and multi-axis diamond machining are considered. Rigorous simulations of grating performance and approaches for simulation of conformal, multi-scale optical systems are discussed.

  17. Chandra X-ray grating spectra of V959 Mon

    NASA Astrophysics Data System (ADS)

    Orio, Marina; Zemko, Polina; Peretz, Uria; Behar, Ehud

    2016-07-01

    V959 Mon (Nova Mon 2012) was discovered in X-rays and gamma rays in the Summer of 2012, before it could be observed optically. It was observed twice with the Chandra gratings, by us in December of 2012 with the Low Energy Transmission Grating (LETG) and previously, in September of 2012, by another team with the Chandra High Energy Transmission Gratings. Although it seems very likely that only a small fraction of the ejecta emitted X-rays in small, dense clumps, the X-ray emission of the ejecta are very important for what the teach us about the kinematics, the chemical composition and nucleosynthesis of the nova. By December, the central source had shrunk almost to pre-outburst size and was visible in X-rays, revealing a massive, hot oxygen-neon white dwarf.

  18. Two-grating Talbot bands spectral-domain interferometer.

    PubMed

    Marques, Manuel J; Bradu, Adrian; Podoleanu, Adrian

    2015-09-01

    A configuration for Talbot bands is presented in which two tilted gratings replace the splitter normally used for recombining the signals from the two interferometer arms. The two optical beams from the interferometer are launched by two fiber leads tightly brought together in the front focal plane of a collimating lens. As the tips of the two fibers are slightly off-axis, the emergent beams after the collimating lens are not parallel. In combination with the two tilted gratings, the nonparallel launching of the two beams leads to a total elimination of mirror terms even when the two beams overlap on either grating. The effects of several geometrical parameters on the visibility performance versus optical path difference between the two arm lengths of the interferometer are evaluated.

  19. Error Measurements in an Acousto-Optic Tunable Filter Fiber Bragg Grating Sensor System

    DTIC Science & Technology

    1994-05-01

    Acousto - Optic Tunable Filter--Fiber Bragg Grating (AOTF-FBG) system. This analysis was targeted to investigate the measurement error in the AOTF-FBG system...Fiber bragg grating, Wavelength division multiplexing, Acousto - optic tunable filter.

  20. Diffraction Revisited: Position of Diffraction Spots upon Rotation of a Transmission Grating

    ERIC Educational Resources Information Center

    Vollmer, Michael

    2005-01-01

    Diffraction gratings are often used in the laboratory to determine the wavelength of laser light. What happens to the spots on the screen if the grating is rotated in this set-up? The answer is nontrivial and instructive.

  1. Fabrication and Testing of Binary-Phase Fourier Gratings for Nonuniform Array Generation

    NASA Technical Reports Server (NTRS)

    Keys, Andrew S.; Crow, Robert W.; Ashley, Paul R.; Nelson, Tom R., Jr.; Parker, Jack H.; Beecher, Elizabeth A.

    2004-01-01

    This effort describes the fabrication and testing of binary-phase Fourier gratings designed to generate an incoherent array of output source points with nonuniform user-defined intensities, symmetric about the zeroth order. Like Dammann fanout gratings, these binary-phase Fourier gratings employ only two phase levels to generate a defined output array. Unlike Dammann fanout gratings, these gratings generate an array of nonuniform, user-defined intensities when projected into the far-field regime. The paper describes the process of design, fabrication, and testing for two different version of the binary-phase grating; one designed for a 12 micron wavelength, referred to as the Long-Wavelength Infrared (LWIR) grating, and one designed for a 5 micron wavelength, referred to as the Mid-Wavelength Infrared Grating (MWIR).

  2. Two-degree-of-freedom displacement measurement system based on double diffraction gratings

    NASA Astrophysics Data System (ADS)

    Lu, Zhengang; Wei, Peipei; Wang, Chaoqun; Jing, Jialei; Tan, Jiubin; Zhao, Xiping

    2016-07-01

    A two-degree-of-freedom (2-DOF) displacement measurement system based on double diffraction gratings is proposed in this paper, which consists of a reflective-type scale grating and a grating read head with a scanning transmission grating. Combining the traditional three-grating interference principle with the Michelson interference principle, the system can measure the displacements of a precision stage along the horizontal direction (X-axis, in the scanning grating plane and vertical to the scanning grating lines) and vertical direction (Z-axis, vertical to the scanning grating plane) simultaneously. The system has the merits of compact structure and uncoupled interference signals in the two axes. By simulating the output signals of the system and comparing them with the experimental results, the validity and feasibility of the system have been verified. The 2-DOF system will be favorable in the displacement measurement of multi-dimensional stages and multi-DOF machines.

  3. Kirigami Nanocomposites as Wide-Angle Diffraction Gratings.

    PubMed

    Xu, Lizhi; Wang, Xinzhi; Kim, Yoonseob; Shyu, Terry C; Lyu, Jing; Kotov, Nicholas A

    2016-06-28

    Beam steering devices represent an essential part of an advanced optics toolbox and are needed in a spectrum of technologies ranging from astronomy and agriculture to biosensing and networked vehicles. Diffraction gratings with strain-tunable periodicity simplify beam steering and can serve as a foundation for light/laser radar (LIDAR/LADAR) components of robotic systems. However, the mechanical properties of traditional materials severely limit the beam steering angle and cycle life. The large strain applied to gratings can severely impair the device performance both in respect of longevity and diffraction pattern fidelity. Here, we show that this problem can be resolved using micromanufactured kirigami patterns from thin film nanocomposites based on high-performance stiff plastics, metals, and carbon nanotubes, etc. The kirigami pattern of microscale slits reduces the stochastic concentration of strain in stiff nanocomposites including those made by layer-by-layer assembly (LBL). The slit patterning affords reduction of strain by 2 orders of magnitude for stretching deformation and consequently enables reconfigurable optical gratings with over a 100% range of period tunability. Elasticity of the stiff nanocomposites and plastics makes possible cyclic reconfigurability of the grating with variable time constant that can also be referred to as 4D kirigami. High-contrast, sophisticated diffraction patterns with as high as fifth diffraction order can be obtained. The angular range of beam steering can be as large as 6.5° for a 635 nm laser beam compared to ∼1° in surface-grooved elastomer gratings and ∼0.02° in MEMS gratings. The versatility of the kirigami patterns, the diversity of the available nanocomposite materials, and their advantageous mechanical properties of the foundational materials open the path for engineering of reconfigurable optical elements in LIDARs essential for autonomous vehicles and other optical devices with spectral range determined

  4. Process improvements in the production of silicon immersion gratings

    NASA Astrophysics Data System (ADS)

    Brooks, Cynthia B.; Kidder, Benjamin; Grigas, Michelle; Griesmann, Ulf; Wilson, Daniel W.; Muller, Richard E.; Jaffe, Daniel T.

    2016-07-01

    We have explored a number of lithographic techniques and improvements to produce the resist lines that then define the grating groove edges of silicon immersion gratings. In addition to our lithographic process using contact printing with photomasks, which is our primary technique for the production of immersion gratings, we explored two alternative fabrication methods, direct-write electron beam and photo-lithography. We have investigated the application of antireflection (AR) coatings during our contact printing lithography method to reduce the effect of Fizeau fringes produced by the contact of the photomask on the photoresist surface. This AR coating reduces the amplitude of the periodic errors by a factor of 1.5. Electron beam (e-beam) patterning allows us to manufacture gratings that can be used in first order, with groove spacing down to 0.5 micrometer or smaller (2,000 grooves/mm), but could require significant e-beam write times of up to one week to pattern a full-sized grating. The University of Texas at Austin silicon diffractive optics group is working with Jet Propulsion Laboratory to develop an alternate e-beam method that employs chromium liftoff to reduce the write time by a factor of 10. We are working with the National Institute of Standards and Technology using laser writing to explore the possibility of creating very high quality gratings without the errors introduced during the contact-printing step. Both e-beam and laser patterning bypass the contact photolithography step and directly write the lines in photoresist on our silicon substrates, but require increased cost, time, and process complexity.

  5. Demonstration of an intelligent hydrogel based diffraction grating

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Bowyer, A.; Eisenthal, R.; Hubble, J.

    2005-05-01

    We report the fabrication of a diffraction grating cast into a responsive hydrogel using a silicone rubber intermediate cast from an engraved glass master grating. The aim to investigate if changes in the swelling of this gel in response to changes in the concentration of a specific analyte led to changes in the line spacing, and hence diffraction pattern, of the grating. The protocol for casting gratings was initially developed using a composite carboxymethyl dextran/bovine serum albumin gel produced using carbodiimide chemistry to assess the optimum gel properties required. Examination under a light microscope showed that, formed under appropriate synthesis conditions, CM-dextran-BSA hydrogels retained the grating structure and appeared to have similar optical properties to the silicon rubber sub-master used for casting. For a facile initial evaluation of the detection principle a number of similar gels were produced using cross-linked alginic acid. In this case excess carboxylic groups remaining after cross-linking were able to form additional ionic cross-links in the presence of divalent cations (Ca2+). Test experiments with these gels showed that both the size and position of the reflected and refracted spots obtained from illumination with a Helium-Neon laser changed as gel swelling changed with calcium ion concentration i.e. the size of both diffraction and reflection spots increased as the alginate hydrogel shrank in response to changes in environmental Ca2+. The utility of the alginate based gels for the detection of cations, together with evidence that dextran protein gels can retain grating structures, suggest that this assay procedure should applicable to any hydrogel where the response is based on protein-ligand interactions. The key requirement is that the cross-linking interactions constraining gel swelling can be quantitatively displaced by the analyte acting as a specific competitor.

  6. Binocular functional architecture for detection of contrast-modulated gratings.

    PubMed

    Georgeson, Mark A; Schofield, Andrew J

    2016-11-01

    Combination of signals from the two eyes is the gateway to stereo vision. To gain insight into binocular signal processing, we studied binocular summation for luminance-modulated gratings (L or LM) and contrast-modulated gratings (CM). We measured 2AFC detection thresholds for a signal grating (0.75c/deg, 216ms) shown to one eye, both eyes, or both eyes out-of-phase. For LM and CM, the carrier noise was in both eyes, even when the signal was monocular. Mean binocular thresholds for luminance gratings (L) were 5.4dB better than monocular thresholds - close to perfect linear summation (6dB). For LM and CM the binocular advantage was again 5-6dB, even when the carrier noise was uncorrelated, anti-correlated, or at orthogonal orientations in the two eyes. Binocular combination for CM probably arises from summation of envelope responses, and not from summation of these conflicting carrier patterns. Antiphase signals produced no binocular advantage, but thresholds were about 1-3dB higher than monocular ones. This is not consistent with simple linear summation, which should give complete cancellation and unmeasurably high thresholds. We propose a three-channel model in which noisy monocular responses to the envelope are binocularly combined in a contrast-weighted sum, but also remain separately available to perception via a max operator. Vision selects the largest of the three responses. With in-phase gratings the binocular channel dominates, but antiphase gratings cancel in the binocular channel and the monocular channels mediate detection. The small antiphase disadvantage might be explained by a subtle influence of background responses on binocular and monocular detection.

  7. Dynamic Optical Grating Device and Associated Method for Modulating Light

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Chu, Sang-Hyon (Inventor)

    2012-01-01

    A dynamic optical grating device and associated method for modulating light is provided that is capable of controlling the spectral properties and propagation of light without moving mechanical components by the use of a dynamic electric and/or magnetic field. By changing the electric field and/or magnetic field, the index of refraction, the extinction coefficient, the transmittivity, and the reflectivity fo the optical grating device may be controlled in order to control the spectral properties of the light reflected or transmitted by the device.

  8. Review of high-speed fiber optic grating sensor systems

    NASA Astrophysics Data System (ADS)

    Udd, Eric; Benterou, Jerry; May, Chadd; Mihailov, Stephen J.; Lu, Ping

    2010-04-01

    Fiber grating sensors can be used to support a wide variety of high speed measurement applications. This includes measurements of vibrations on bridges, traffic monitoring on freeways, ultrasonic detection to support non-destructive tests on metal plates, and providing details of detonation events. This paper provides a brief overview of some of the techniques that have been used to support high speed measurements using fiber grating sensors over frequency ranges from 10s of kHz, to MHZ and finally toward frequencies approaching the GHz regime.

  9. Invariance of waveguide grating mirrors to lateral displacement phase shifts.

    PubMed

    Brown, Daniel; Friedrich, Daniel; Brückner, Frank; Carbone, Ludovico; Schnabel, Roman; Freise, Andreas

    2013-06-01

    We present a method to analyze the coupling of lateral displacements in nanoscale structures, in particular waveguide grating mirrors (WGMs), into the phase of a reflected Gaussian beam using a finite-difference time-domain simulation. Such phase noise is of interest for using WGMs in high-precision interferometry. We show that, to the precision of our simulations (10(-7) rad), waveguide mirrors do not couple lateral displacement into phase noise of a reflected beam and that WGMs are therefore not subject to the same stringent alignment requirements as previously proposed layouts using diffraction gratings.

  10. Miniaturized NIR scanning grating spectrometer for use in mobile phones

    NASA Astrophysics Data System (ADS)

    Knobbe, Jens; Pügner, Tino; Grüger, Heinrich

    2016-05-01

    An extremely miniaturized scanning grating spectrometer at the size of a sugar cube has been developed at Fraunhofer IPMS. To meet the requirements for the integration into a mobile phone a new system approach has been pursued. The key component within the system is a silicon-based deflectable diffraction grating with an integrated driving mechanism. A first sample of the new spectrometer was built and characterized. It was found to have a spectral range from 950 nm to 1900 nm at a resolution of 10 nm. The results show that the performance of the new MEMS spectrometer is in good agreement with the requirements for mobile phone integration.

  11. Time-dependent Bragg diffraction by multilayer gratings

    NASA Astrophysics Data System (ADS)

    André, Jean-Michel; Jonnard, Philippe

    2016-01-01

    Time-dependent Bragg diffraction by multilayer gratings working by reflection or by transmission is investigated. The study is performed by generalizing the time-dependent coupled-wave theory previously developed for one-dimensional photonic crystals (André J-M and Jonnard P 2015 J. Opt. 17 085609) and also by extending the Takagi-Taupin approach of the dynamical theory of diffraction. The indicial response is calculated. It presents a time delay with a transient time that is a function of the extinction length for reflection geometry and of the extinction length combined with the thickness of the grating for transmission geometry.

  12. Fiber-guided modes conversion using superposed helical gratings

    NASA Astrophysics Data System (ADS)

    Ma, Yancheng; Fang, Liang; Wu, Guoan

    2017-03-01

    Optical fibers can support various modal forms, including vector modes, linear polarization (LP) modes, and orbital angular momentum (OAM) modes, etc. The modal correlation among these modes is investigated via Jones matrix, associated with polarization and helical phase corresponding to spin angular momentum (SAM) and OAM of light, respectively. We can generate different modal forms by adopting superposed helical gratings (SHGs) with opposite helix orientations. Detailed analysis and discussion on mode conversion is given as for mode coupling in optical fibers with both low and high contrast index, respectively. Our study may deepen the understanding for various fiber-guided modes and mode conversion among them via fiber gratings.

  13. Security System Responsive to Optical Fiber Having Bragg Grating

    NASA Technical Reports Server (NTRS)

    Gary, Charles K. (Inventor); Ozcan, Meric (Inventor)

    1997-01-01

    An optically responsive electronic lock is disclosed comprising an optical fiber serving as a key and having Bragg gratings placed therein. Further, an identification system is disclosed which has the optical fiber serving as means for tagging and identifying an object. The key or tagged object is inserted into a respective receptacle and the Bragg gratings cause the optical fiber to reflect a predetermined frequency spectra pattern of incident light which is detected by a decoder and compared against a predetermined spectrum to determine if an electrical signal is generated to either operate the lock or light a display of an authentication panel.

  14. Demodulation System for Fiber Optic Bragg Grating Dynamic Pressure Sensing

    NASA Technical Reports Server (NTRS)

    Lekki, John D.; Adamovsky, Grigory; Floyd, Bertram

    2001-01-01

    Fiber optic Bragg gratings have been used for years to measure quasi-static phenomena. In aircraft engine applications there is a need to measure dynamic signals such as variable pressures. In order to monitor these pressures a detection system with broad dynamic range is needed. This paper describes an interferometric demodulator that was developed and optimized for this particular application. The signal to noise ratio was maximized through temporal coherence analysis. The demodulator was incorporated in a laboratory system that simulates conditions to be measured. Several pressure sensor configurations incorporating a fiber optic Bragg grating were also explored. The results of the experiments are reported in this paper.

  15. Liquid crystal gratings based on alternate TN and PA photoalignment.

    PubMed

    Hu, Wei; Srivastava, Abhishek; Xu, Fei; Sun, Jia-Tong; Lin, Xiao-Wen; Cui, Hong-Qing; Chigrinov, Vladimir; Lu, Yan-Qing

    2012-02-27

    A diffraction grating is proposed by periodically defining the liquid-crystal director distribution to form alternate parallel aligned and twist nematic regions in a cell placed between two crossed polarizers. Based on the combined phase and amplitude modulation, both 1D and 2D tunable gratings are demonstrated. Low voltage ON/OFF switching of 1st order diffracted light with extinction ratio over 80 is achieved within a small voltage interval of 0.15 Vrms. Unique four-state feature of the cell is obtained and their applications in optical logic devices are discussed.

  16. Generation of Bessel beam arrays through Dammann gratings.

    PubMed

    García-Martínez, Pascuala; Sánchez-López, María M; Davis, Jeffrey A; Cottrell, Don M; Sand, David; Moreno, Ignacio

    2012-03-20

    In this work we apply the Dammann grating concept to generate an equal-intensity square array of Bessel quasi-free diffraction beams that diverge from a common center. We generate a binary phase mask that combines the axicon phase with the phase of a Dammann grating. The procedure can be extended to include vortex spiral phases that generate an array of optical pipes. Experimental results are provided by means of a twisted nematic liquid crystal display operating as a binary π phase spatial light modulator.

  17. Aspheric wave-front recording optics for holographic gratings.

    PubMed

    Namioka, T; Koike, M

    1995-05-01

    The geometric theory of aspheric wave-front recording optics is extended to include the fourth-order groove parameters that correspond to the fourth-order holographic terms in the light-path function. We derived explicit expressions of the groove parameters by analytically following an exact ray-tracing procedure for a double-element optical system that consists of a point source, an ellipsoidal mirror, and an ellipsoidal grating blank. Design examples of holographic gratings for an in-plane Eagle-type vacuum-UV monochromator are given to demonstrate the capability of the present theory in the design of aspheric wave-front recording optics.

  18. Recording polarization gratings with a standing spiral wave

    SciTech Connect

    Vernon, Jonathan P.; Tondiglia, Vincent P.; White, Timothy J.; Bunning, Timothy J.; Serak, Svetlana V.; Hakobyan, Rafik S.; Aleksanyan, Artur K.; Tabiryan, Nelson V.

    2013-11-11

    A scalable and robust methodology for writing cycloidal modulation patterns of optical axis orientation in photosensitive surface alignment layers is demonstrated. Counterpropagating circularly polarized beams, generated by reflection of the input beam from a cholesteric liquid crystal, direct local surface orientation in a photosensitive surface. Purposely introducing a slight angle between the input beam and the photosensitive surface normal introduces a grating period/orientation that is readily controlled and templated. The resulting cycloidal diffractive waveplates offer utility in technologies requiring diffraction over a broad range of angles/wavelengths. This simple methodology of forming polarization gratings offers advantages over conventional fabrication techniques.

  19. A laser microvibration transducer based on two diffraction gratings

    NASA Astrophysics Data System (ADS)

    Niyibizi, Alphonse

    2004-06-01

    A laser microvibrations transducer based on diffraction of a laser beam on a system of two diffraction gratings is described. The transducer has an experimental threshold of detection of 0.3A°, a dynamic range of about 10 μm. It contains no expensive elements (simple glass stepped gratings) and it is easy to implement and align. Furthermore it is self-calibrating. It can be successfully used for nuclear explosion monitoring and can be useful tool in industrial machinery, transport equipment vibration testing and control and seismic monitoring.

  20. Low-loss arrayed waveguide grating at 760 nm.

    PubMed

    Stanton, E J; Spott, A; Davenport, M L; Volet, N; Bowers, J E

    2016-04-15

    An arrayed waveguide grating (AWG) at 760 nm is demonstrated with an insertion loss smaller than 0.5 dB. Interface roughness and waveguide length errors contribute much more to scattering loss and phase errors at 760 nm than at longer wavelengths, thus requiring improved design and fabrication. This Letter details how this is achieved by minimizing interfacial scattering, grating side-order excitation, and phase errors in the AWG. With silicon nitride core and silicon dioxide clad waveguides on silicon, this AWG is compatible with heterogeneously integrated lasers for on-chip spectral beam combining.