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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. Thick-SOI Echelle grating for any-to-any wavelength routing interconnection in multi-socket computing environments

    NASA Astrophysics Data System (ADS)

    Dabos, G.; Pitris, S.; Mitsolidou, C.; Alexoudi, T.; Fitsios, D.; Cherchi, M.; Harjanne, M.; Aalto, T.; Kanellos, G. T.; Pleros, N.

    2017-02-01

    As data centers constantly expand, electronic switches are facing the challenge of enhanced scalability and the request for increased pin-count and bandwidth. Photonic technology and wavelength division multiplexing have always been a strong alternative for efficient routing and their potential was already proven in the telecoms. CWDM transceivers have emerged in the board-to-board level interconnection, revealing the potential for wavelength-routing to be applied in the datacom and an AWGR-based approach has recently been proposed towards building an optical multi-socket interconnection to offer any-to-any connectivity with high aggregated throughput and reduced power consumption. Echelle gratings have long been recognized as the multiplexing block exhibiting smallest footprint and robustness in a wide number of applications compared to other alternatives such as the Arrayed Waveguide Grating. Such filtering devices can also perform in a similar way to cyclical AWGR and serve as mid-board routing platforms in multi-socket environments. In this communication, we present such a 3x3 Echelle grating integrated on thick SOI platform with aluminum-coated facets that is shown to perform successful wavelength-routing functionality at 10 Gb/s. The device exhibits a footprint of 60x270 μm2, while the static characterization showed a 3 dB on-chip loss for the best channel. The 3 dB-bandwidth of the channels was 4.5 nm and the free spectral range was 90 nm. The echelle was evaluated in a 2x2 wavelength routing topology, exhibiting a power penalty of below 0.4 dB at 10-9 BER for the C-band. Further experimental evaluations of the platform involve commercially available CWDM datacenter transceivers, towards emulating an optically-interconnected multi-socket environment traffic scenario.

  10. The effect of ultrasonic vibration and surfactant additive on fabrication of 53.5gr/mm silicon echelle grating with low surface roughness in alkaline KOH solution.

    PubMed

    Jiao, Qingbin; Zhu, Chunlin; Tan, Xin; Qi, Xiangdong; Bayanheshig

    2018-01-01

    In the silicon echelle grating fabrication process, the "pseudo-mask" formed by the hydrogen bubbles generated during the etching process is the reason causing high surface roughness and poor surface quality of blazed plane. Based upon the ultrasonic mechanical effect and contact angle reduced by surfactant additive, ultrasonic vibration, isopropyl alcohol (IPA) and 2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD) were used to improve surface quality of 53.5gr/mm echelle grating. The surface roughness Rq is smaller than 18nm, 7nm and 2nm when using ultrasonic vibration, IPA and TMDD respectively. The surface roughness Rq is smaller than 5nm and 1.5nm respectively when combining ultrasonic vibration with IPA and TMDD. The experimental results indicated that the combination of ultrasonic agitation and surfactant additive (IPA&TMDD) could obtain a lower surface roughness of blazed plane in silicon echelle grating fabrication process. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. 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

  12. 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}.

  13. 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.

  14. Texas echelon cross echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Lacy, John H.; Richter, Matthew J.; Yu, Wanglong; Basso, Bianca S.

    1998-08-01

    A new mid-IR spectrograph, the Texas Echelon Cross Echelle Spectrograph (TEXES) is under construction. The primary motivation for TEXES is to observe interstellar molecules at very high resolution. TEXES will operate at 7-25 micrometers wavelength with three spectrographic modes: a high resolution cross-dispersed mode, with R approximately equals 100,000, a mid-resolution long-slit mode, with R approximately equals 14,000, and a low resolution long-slit mode, with R approximately equals 2000. In hi-res mode, the primary disperser is a 36 inch long, R10 grating with a 7 mm groove spacing. The echelon is cross-dispersed with a 7 in long R2 echelle. In mid-res mode, the echelon is by-passed with an Offner relay, and the echelle is used by itself. In lo-res mode, a first-order grating is inserted over the echelle. For initial test, TEXES will use a Hughes Aircraft 20 X 64 pixel Si:As impurity-band array, which covers only two echelon orders. It will later be replaced with a 256 X 256 pixel array, which will Nyquist sample approximately 10 orders. The spectrograph has been assembled and tested with a partially complete echelon, demonstrating the soundness of the design. When we began this project, we were unable to find a vendor capable of machining or ruling a diffraction grating with the very coarse ruling required. Consequently, we attempted to hand-fabricate the echelon. We have not succeeded in assembling the echelon with the required precision, missing by about a factor of two. Fortunately, Hyperfine, Inc. is now capable of diamond machining the echelon. We are purchasing a machined echelon, and hope to complete the spectrograph by the end of summer 1998.

  15. 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.

  16. 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.

  17. Echelle efficiencies: Theory and experiment - Comment

    NASA Astrophysics Data System (ADS)

    Bottema, M.

    1981-02-01

    The efficiency of an echelle grating is derived on the basis of the commonly accepted definition of efficiency as a measure of the integrated energy in the spectral image rather than its intensity. Some differences with the results obtained by Schroeder and Hilliard (1980) are pointed out.

  18. 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.

  19. 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.

  20. Post-SM4 Sensitivity Calibration of the STIS Echelle Modes

    NASA Astrophysics Data System (ADS)

    Bostroem, K. Azalee; Aloisi, A.; Bohlin, R.; Hodge, P.; Proffitt, C.

    2012-01-01

    On-orbit sensitivity curves for all echelle modes were derived for post - servicing mis- sion 4 data using observations of the DA white dwarf G191-B2B. Additionally, new echelle ripple tables and grating dependent bad pixel tables were created for the FUV and NUV MAMA. We review the procedures used to derive the adopted throughputs and implement them in the pipeline as well as the motivation for the modification of the additional reference files and pipeline procedures.

  1. 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.

  2. 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.

  3. 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.

  4. Optimal Extraction of Echelle Spectra

    NASA Astrophysics Data System (ADS)

    Piskunov, Nikolai

    The extraction of the echelle spectra registered with a CCD detector represents a big challenge because of three reasons: (1) the pixel sampling is often close or worse then optimal, (2) spectral orders are curved and tilted with respect to the CCD rows (or columns) and (3) every pixel contains additional noise coming from various sources as illustrated in Figure 1. The main goal of an optimal extraction is to recover as much of the science signal while minimizing the contribution of the noise. Here we present the Slit Function Decomposition algorithm which replaces the summation in a sliding window with a reconstruction of the slit illumination profile. The reconstruction is formulated as an inverse problem solved by iterations and it is robust against most of the systematic problems including cosmic rays and cosmetic defects.

  5. The coude spectrograph and echelle scanner of the 2.7 m telescope at McDonald Observatory.

    NASA Technical Reports Server (NTRS)

    Tull, R. G.

    1972-01-01

    Discussion of certain design aspects of the coude spectrograph, and description of the coude scanner that uses some of the spectrograph optics. The configuration of the large echelle grating used is reviewed along with the systems of computer scanner control and data handling.

  6. 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.

  7. 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.

  8. The Time-Dependent Sensitivity of the MAMA and CCD Long-Slit Gratings

    NASA Astrophysics Data System (ADS)

    Holland, Stephen T.; Aloisi, Alessandra; Bostroem, Azalee; Oliveria, Cristina; Proffitt, Charles

    2014-12-01

    We present the results of observing flux standard stars used to determine trends in the sensitivities of the five STIS low-resolution, long-slit gratings between 1997 and 2013. Also, the assumption that the sensitivity trends for the medium-resolution and echelle gratings are the same as those for the corresponding low-resolution gratings is tested.

  9. Correction for the STIS echelle blaze function

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Brown, Thomas M.

    1997-01-01

    Using the Early Release Observation of 9 Comae, we demonstrate an iterative method for correcting Space Telescope Imaging Spectrograph (STIS) echelle spectra for the effects of the echelle ripple. This analytic approach allows the actual spectrum of interest to be used in the determination of its calibration. The late F star 9 Comae is not an ideal candidate for this method, due to the many absorption lines present in its E230M spectrum, yet, given this difficulty, the method still works quite well.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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).

  16. 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).

  17. 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.

  18. Post - SM4 Flux Calibration of the STIS Echelle Modes

    NASA Astrophysics Data System (ADS)

    Bostroem, Azalee; Aloisi, A.; Bohlin, R. C.; Proffitt, C. R.; Osten, R. A.; Lennon, D.

    2010-07-01

    Like all STIS spectroscopic modes, STIS echelle modes show a wavelength dependent decline in detector sensitivity with time. The echelle sensitivity is further affected by a time-dependent shift in the blaze function. To better correct the effects of the echelle sensitivity loss and the blaze function changes, we derive new baselines for echelle sensitivities from post-HST Servicing Mission 4 observations of the standard star G191-B2B. We present how these baseline sensitivities compare to pre-failure trends.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Electromagnetic diffraction efficiencies for plane reflection diffraction gratings

    NASA Technical Reports Server (NTRS)

    Marathay, A. S.; Shrode, T. E.

    1974-01-01

    The theory and computer programs, based on electromagnetic theory, for the analysis and design of echelle gratings were developed. The gratings are designed for instruments that operate in the ultraviolet portion of the spectrum. The theory was developed so that the resulting computer programs will be able to analyze deep (up to 30 wavelengths) gratings by including as many as 100 real or homogeneous diffraction orders. The program calculates the complex amplitude coefficient for each of the diffracted orders. A check on the numerical method used to solve the integral equations is provided by a conservation of energy calculation.

  4. CESAR: Compact Echelle Spectrograph for Aeronomical Research

    NASA Astrophysics Data System (ADS)

    Melchiorri, R.; Grill, M.; Kendall, E. A.; Schiesser, E.; Slanger, T. G.; Radovan, M.; Lacoursiere, J.

    2010-12-01

    CESAR (Compact Echelle Spectrograph for Aeronomical Research) is a state-of-the-art instrument being constructed at SRI International under an NSF Major Research Instrumentation (MRI) program grant. Conceptually, CESAR is an outgrowth of nightglow studies carried out over the last 10 years utilizing the sky spectra of the 8 10 m class optical telescopes - Keck I and Keck II on Mauna Kea, and the VLT (Very Large Telescope) in Chile. Our goal is to significantly expand the range of upper atmospheric science investigations (nightglow, aurora, and dayglow emissions) by providing aeronomers with a high-throughput, high-dispersion, large-passband spectrograph of a caliber heretofore only available to astronomers at a handful of large observatories. We have scaled an astronomical grade echelle spectrograph into a portable version which can be sited at multiple geophysically significant stations. CESAR will cover the wavelength range from 300 to 1000nm with a spectral resolution of 20,000 and observe the sky in any direction with a FOV ranging from 7° to 20° and with a spatial resolution ranging from 0.06° to 0.5°. Upon completion, CESAR will be sited at Flat Research Range (PFRR) in Alaska for studies of aurorae and nightglow. We will first demonstrate CESAR capabilities in comparison to existing instruments, in terms of data acquisition rates, spectral coverage, and sensitivity. Focused experiments will follow, including (1) studies of sources of the oxygen atom Rydberg lines in aurora, looking at many more lines than the standard 777.4 and 844.6 nm emissions; (2) studies of the highly vibrationally excited levels in the O2(b-X) atmospheric bands, well known at equatorial latitudes, but unexplored at high latitudes and in aurorae; (3) continued studies of the OH Meinel bands and influences related to the presence of aurorae and to the general coupling of nightglow and auroral features; and (4) observation of the 2D and 2P states of O+ in aurorae. CESAR has now

  5. 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.

  6. 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.

  7. 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.

  8. NRES: The Network of Robotic Echelle Spectrographs

    NASA Astrophysics Data System (ADS)

    Siverd, Robert; Brown, Timothy M.; Henderson, Todd; Hygelund, John; Barnes, Stuart; Bowman, Mark; De Vera, Jon; Eastman, Jason D.; Kirby, Annie; Norbury, Martin; Smith, Cary; Taylor, Brook; Tufts, Joseph; Van Eyken, Julian C.

    2017-06-01

    Las Cumbres Observatory (LCO) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of four to 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 ten 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 = 11 or 12. Following a few months of on-sky evaluation at our BPL test facility, the first spectrograph unit was shipped to CTIO in late 2016 and installed in March 2017. Barring serious complications, we expect regular scheduled science observing to begin in mid-2017. Three additional units are in building or testing phases and slated for deployment in late 2017. Acting in concert, these four spectrographs will provide a new, unique facility for stellar characterization and precise radial velocities. We will briefly overview the LCO telescope network, the NRES spectrograph design, the advantages it provides, and development challenges we encountered along the way. We will further discuss real-world performance from our first unit, initial science results, and the ongoing software development effort needed to automate such a facility for a wide array of science cases.

  9. New On-Orbit Sensitivity Calibrationfor All STIS Echelle Modes

    NASA Astrophysics Data System (ADS)

    Aloisi, Alessandra; Bohlin, Ralph; Quijano, Jessica Kim

    2007-01-01

    On-orbit sensitivities for the 32 medium- and high-resolution STIS echelle secondarymodes were determined for the rst time using observations of the fundamental DAwhite dwarf standard star G191-B2B. Revised on-orbit sensitivities for the 12 mediumandhigh-resolution echelle prime modes based on observations of the same standardstar are also presented. We review the procedures and assumptions used to derive theadopted throughputs and implement them into the pipeline.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. FEROS: the new fiber-linked echelle spectrograph for the ESO 1.52-m telescope

    NASA Astrophysics Data System (ADS)

    Kaufer, Andreas; Pasquini, Luca

    1998-07-01

    FEROS is a new fiber-fed bench-mounted prism crossdispersed echelle spectrograph for the ESO 1.52-m telescope at the European Southern Observatory (ESO) in La Silla, Chile. It works with a 79 lines/mm R2 echelle grating in quasi-Littrow mode and in white pupil configuration. With two fibers of 100 micrometer core diameter for the object and the nearby sky, the complete optical spectrum from 370 - 860 nm is recorded in one single exposure on a 2k X 4k thinned CCD with 15 micrometer pixels. Therefore, the instrument can work in a fixed configuration on the optical bench without movable parts besides the CCD shutter mechanics. For the highest-possible opto-mechanical stability. FEROS will be housed in a temperature and humidity controlled room in the former Coude room of the telescope. The resolving power of R equals 48,000 is reached by the use of a newly designed two-slice image slicer which is fed by the two fibers. Alternatively, the sky fiber can be illuminated with a calibration lamp during the whole object exposure to monitor the spectrograph's residual motions for high-precision radial-velocity work. FEROS is built for ESO by a consortium of four European astronomical institutes under the leadership of the Landessternwarte Heidelberg, Germany. Further members of the consortium are the Astronomical Observatory Copenhagen, Denmark, the Institut d'Astrophysique de Paris, and the Observatoire de Paris/Meudon, France. It is planned that FEROS will be fully operational at the ESO 1.52-m telescope in December 1998 and will be available to the community in early 1999.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Post-Servicing Mission 4 Flux Calibration of the STIS Echelle Modes

    NASA Astrophysics Data System (ADS)

    Azalee Bostroem, K.; Aloisi, A.; Proffitt, C.; Osten, R.; Bohlin, R.

    2011-01-01

    STIS echelle modes show a wavelength-dependent decline in sensitivity with time. While this trend is observed in all STIS spectroscopic modes, the echelle sensitivity is further affected by a time-dependent shift in the blaze function. To improve the echelle flux calibration, new baselines for the echelle sensitivities are derived from post-Servicing Mission 4 (SM4) observations of the Hubble Space Telescope standard star G191-B2B. We present how these baseline sensitivities compare to pre-failure trends. Specifically, where the new results differ from expectations and discuss anomalous results found in E140H monitoring observations are highlighted.

  3. 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.

  4. NEWS: the near-infrared Echelle for wideband spectroscopy

    NASA Astrophysics Data System (ADS)

    Veyette, Mark J.; Muirhead, Philip S.; Hall, Zachary J.; Taylor, Brian; Ye, Jimmy

    2016-08-01

    We present an updated optical and mechanical design of NEWS: the Near-infrared Echelle for Wide-band Spectroscopy (formerly called HiJaK: the High-resolution J, H and K spectrometer), a compact, high-resolution, near-infrared spectrometer for 5-meter class telescopes. NEWS provides a spectral resolution of 60,000 and covers the full 0.8-2.5 μm range in 5 modes. We adopt a compact, lightweight, monolithic design and have developed NEWS to be mounted to the instrument cube at the Cassegrain focus of the new 4.3-meter Discovery Channel Telescope.

  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. Silicon immersion gratings and their spectroscopic applications

    NASA Astrophysics Data System (ADS)

    Ge, Jian; Zhao, Bo; Powell, Scott; Fletcher, Adam; Wan, Xiaoke; Chang, Liang; Jakeman, Hali; Koukis, Dimitrios; Tanner, David B.; Ebbets, Dennis; Weinberg, Jonathan; Lipscy, Sarah; Nyquist, Rich; Bally, John

    2012-09-01

    Silicon immersion gratings (SIGs) offer several advantages over the commercial echelle gratings for high resolution infrared (IR) spectroscopy: 3.4 times the gain in dispersion or ~10 times the reduction in the instrument volume, a multiplex gain for a large continuous wavelength coverage and low cost. We present results from lab characterization of a large format SIG of astronomical observation quality. This SIG, with a 54.74 degree blaze angle (R1.4), 16.1 l/mm groove density, and 50x86 mm2 grating area, was developed for high resolution IR spectroscopy (R~70,000) in the near IR (1.1-2.5 μm). Its entrance surface was coated with a single layer of silicon nitride antireflection (AR) coating and its grating surface was coated with a thin layer of gold to increase its throughput at 1.1-2.5 μm. The lab measurements have shown that the SIG delivered a spectral resolution of R=114,000 at 1.55 μm with a lab testing spectrograph with a 20 mm diameter pupil. The measured peak grating efficiency is 72% at 1.55 μm, which is consistent with the measurements in the optical wavelengths from the grating surface at the air side. This SIG is being implemented in a new generation cryogenic IR spectrograph, called the Florida IR Silicon immersion grating spectrometer (FIRST), to offer broad-band high resolution IR spectroscopy with R=72,000 at 1.4-1.8 um under a typical seeing condition in a single exposure with a 2kx2k H2RG IR array at the robotically controlled Tennessee State University 2-meter Automatic Spectroscopic Telescope (AST) at Fairborn Observatory in Arizona. FIRST is designed to provide high precision Doppler measurements (~4 m/s) for the identification and characterization of extrasolar planets, especially rocky planets in habitable zones, orbiting low mass M dwarf stars. It will also be used for other high resolution IR spectroscopic observations of such as young stars, brown dwarfs, magnetic fields, star formation and interstellar mediums. An optimally designed

  8. Fiber-optic-echelle-CCD spectral monitoring of UX Arietis

    SciTech Connect

    Huenemoerder, D.P.; Buzasi, D.L.; Ramsey, L.W. )

    1989-10-01

    Results are presented on 30 fiber-optic-echelle-CCD spectra for the UX Ari system, covering one orbit in the spring and two orbits in the fall of 1987. The spectra obtained have a resolution of about 12,000 over the range of the Ca II H lines in the near UV to the Ca II triplet in the near IR, covering several activity sensitive lines. The most striking features observed were strong H-alpha and H-beta absorption near phase 0.8, which were present at epochs eight months apart. The geometry of the system, as determined from the mass ratio, rotational velocities, and the assumption of synchronous rotation, gives a radius for the K star that is approximately filling its Roche lobe. It is suggested that the excess absorption seen is due to mass-transfer activity resulting from Roche lobe overflow of the K star and accretion onto the G star. 30 refs.

  9. 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.

  10. Role of the grating profile in Smith-Purcell radiation at high energies

    NASA Astrophysics Data System (ADS)

    Brownell, J. H.; Doucas, G.

    2005-09-01

    The passage of a finely focused electron beam near the surface of a periodic metallic grating produces radiation known as Smith-Purcell radiation. This paper presents an analysis of the role of the grating profile in the case of echelle-type gratings whose period consists of two facets only. Particular emphasis is placed on the ultrarelativistic regime and a comparison is made with recent experimental results in this region. It is shown that the details of the profile of the grating play an important role in the optimization of the radiated energy. The behavior of higher order modes and the limitations of the surface current description of the radiative process are also discussed briefly.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. 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.

  17. Hectochelle: A Multiobject Optical Echelle Spectrograph for the MMT

    NASA Astrophysics Data System (ADS)

    Szentgyorgyi, Andrew; Furesz, Gabor; Cheimets, Peter; Conroy, Maureen; Eng, Roger; Fabricant, Daniel; Fata, Robert; Gauron, Thomas; Geary, John; McLeod, Brian; Zajac, Joseph; Amato, Stephen; Bergner, Henry; Caldwell, Nelson; Dupree, Andrea; Goddard, Richard; Johnston, Everett; Meibom, Soeren; Mink, Douglas; Pieri, Mario; Roll, John; Tokarz, Susan; Wyatt, William; Epps, Harland; Hartmann, Lee; Meszaros, Szabolcz

    2011-10-01

    The Hectochelle is an optical band, fiber-fed, multiobject echelle spectrograph deployed at the MMT Observatory on Mount Hopkins, Arizona. The optical fibers that feed the Hectochelle are positioned by the Hectospec robot positioner on the MMT f/5 focal surface, and the Hectochelle shares an optical fiber feed system with the Hectospec, a moderate-dispersion spectrograph that is collocated with the Hectochelle. Hectochelle can record up to 240 spectra simultaneously at a resolution of 38,000. Spectra cover a single diffractive order that is approximately 150 Å wide. The total potential operating passband of the Hectochelle extends from 3800 Å to 9000 Å. Operated in conjunction with the MMT f/5 secondary, the MMT wide-field corrector, and the atmospheric dispersion compensator, the patrol field is 1° in diameter and the individual fiber slits are 1.5‧‧ in diameter. The throughput of the combined telescope, fiber feed, and spectrograph is measured to be 6.1% at 5275 Å, exclusive of atmospheric extinction. A 20 minute observation of a V = 15 F-type star yields a signal-to-noise ratio of 35 per resolution element. Hectochelle had first light 2003 December 4 and continues to be operated at the MMT today.

  18. 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.

  19. 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.

  20. Obtaining accurate radial velocities for Cepheid companions using the STIS echelles

    NASA Astrophysics Data System (ADS)

    Proffitt, C. R.; Evans, N. R.; Winston, E. M.; Gallenne, A.; Kervella, P.

    2017-09-01

    We discuss the high dispersion echelle observations of the hot binary companions of six Cepheids with known radial-velocity orbits that we have obtained with the STIS FUV E140H mode on board the Hubble Space Telescope, with the goal of determining the masses of these Cepheids. We discuss the stability and repeatability of the STIS echelle wavelength scale and other issues that may limit the final accuracy of our mass determinations.

  1. 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.

  2. Properties of the ionized gas in HH 202 - II. Results from echelle spectrophotometry with Ultraviolet Visual Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Mesa-Delgado, A.; Esteban, C.; García-Rojas, J.; Luridiana, V.; Bautista, M.; Rodríguez, M.; López-Martín, L.; Peimbert, M.

    2009-05-01

    We present results of deep echelle spectrophotometry of the brightest knot of the Herbig-Haro object HH 202 in the Orion Nebula - HH 202-S - using the Ultraviolet Visual Echelle Spectrograph in the spectral range from 3100 to 10400 Å. The high spectral resolution of the observations has permitted to separate the component associated with the ambient gas from that associated with the gas flow. We derive electron densities and temperatures from different diagnostics for both components, as well as the chemical abundances of several ions and elements from collisionally excited lines, including the first determinations of Ca+ and Cr+ abundances in the Orion Nebula. We also calculate the He+, C2+, O+ and O2+ abundances from recombination lines. The difference between the O2+ abundances determined from collisionally excited and recombination lines - the so-called abundance discrepancy factor - is 0.35 and 0.11 dex for the shock and nebular components, respectively. Assuming that the abundance discrepancy is produced by spatial variations in the electron temperature, we derive values of the temperature fluctuation parameter, t2, of 0.050 and 0.016 for the shock and nebular components, respectively. Interestingly, we obtain almost coincident t2 values for both components from the analysis of the intensity ratios of HeI lines. We find significant departures from case B predictions in the Balmer and Paschen flux ratios of lines of high principal quantum number n. We analyse the ionization structure of HH 202-S, finding enough evidence to conclude that the flow of HH 202-S has compressed the ambient gas inside the nebula trapping the ionization front. We measure a strong increase of the total abundances of nickel and iron in the shock component, the abundance pattern and the results of photoionization models for both components are consistent with the partial destruction of dust after the passage of the shock wave in HH 202-S. Based on observations collected at the European

  3. Electromagnetically induced phase grating.

    PubMed

    de Araujo, Luís E E

    2010-04-01

    I propose an electromagnetically induced phase grating based on the giant Kerr nonlinearity of an atomic medium under electromagnetically induced transparency. The atomic phase grating behaves similarly to an ideal sinusoidal phase grating, and it is capable of producing a pi phase excursion across a weak probe beam along with high transmissivity. The grating is created with arbitrarily weak fields, and diffraction efficiencies as high as 30% are predicted.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Automatic one dimensional spectra extraction for Weihai fiber-fed high resolution echelle spectra

    NASA Astrophysics Data System (ADS)

    Hu, Shao Ming; Gao, Dong Yang

    2014-11-01

    One fiber-fed high resolution echelle spectrograph was built for the one meter telescope atWeihai Observatory of Shandong University. It is used for exoplanet searching by radial velocity method and for stellar spectra analysis. One dimensional spectra extraction from the raw echelle data is researched in this paper. Flat field images with different exposure times were used to trace the order position accurately. The accurate background was fitted from each CCD image and it was subtracted from the raw image to correct the background and straylight. The intensity of each order decreases towards the order margin, and the lengths of order are different between the blue and red regions. The order tracing during the data reduction was investigated in this work. Accurate flux can be obtained after considering the effects of bad pixels, the curvature of each order and so on. One Interactive Data Language program for one dimensional spectra extraction was adopted and implemented to echelle data reduction for Weihai fiber-fed high resolution echelle spectra, and the results are illustrated here. The program is efficient and accurate for echelle data reduction. It can be adopted to reduce data taken by other instruments even the spectrographs in other fields, and it is very convenient for astronomers.

  10. 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

  11. 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.

  12. 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.

  13. Bragg Grating Simulation Software

    DTIC Science & Technology

    2008-02-01

    Organisation DSTO-TN-0800 ABSTRACT (U) This document is a user manual for a software application that predicts the complex reflection spectrum of...fibre Bragg gratings, given user defined input parameters. The software is designed primarily to complement the joint DSTO/Swinburne grating writing

  14. 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.

  15. Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra

    NASA Astrophysics Data System (ADS)

    Becker, Juliette C.; Johnson, John Asher; Vanderburg, Andrew; Morton, Timothy D.

    2015-04-01

    We present a technique to extract radial velocity (RV) measurements from echelle spectrograph observations of rapidly rotating stars (V sin i≳ 50 km s-1). This type of measurement is difficult because the line widths of such stars are often comparable to the width of a single echelle order. To compensate for the scarcity of lines and Doppler information content, we have developed a process that forward-models the observations, fitting the RV shift of the star for all echelle orders simultaneously with the echelle blaze function. We use our technique to extract RV measurements from a sample of rapidly rotating A- and B-type stars used as calibrator stars observed by the California Planet Survey observations. We measure absolute RVs with a precision ranging from 0.5-2.0 km s-1 per epoch for more than 100 A- and B-type stars. In our sample of 10 well-sampled stars with RV scatter in excess of their measurement uncertainties, three of these are single-lined binaries with long observational baselines. From this subsample, we present detections of two previously unknown spectroscopic binaries and one known astrometric system. Our technique will be useful in measuring or placing upper limits on the masses of sub-stellar companions discovered by wide-field transit surveys, and conducting future spectroscopic binarity surveys and Galactic space-motion studies of massive and/or young, rapidly rotating stars.

  16. 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.

  17. 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.

  18. 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).

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Development of silicon grisms and immersion gratings for high-resolution infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Ge, Jian; McDavitt, Daniel L.; Bernecker, John L.; Miller, Shane; Ciarlo, Dino R.; Kuzmenko, Paul J.

    2002-01-01

    We report new results on silicon grism and immersion grating development using photolithography and anisotropic chemical etching techniques, which include process recipe finding, prototype grism fabrication, lab performance evaluation and initial scientific observations. The very high refractive index of silicon (n=3.4) enables much higher dispersion power for silicon-based gratings than conventional gratings, e.g. a silicon immersion grating can offer a factor of 3.4 times the dispersion of a conventional immersion grating. Good transmission in the infrared (IR) allows silicon-based gratings to operate in the broad IR wavelength regions (~1- 10 micrometers and far-IR), which make them attractive for both ground and space-based spectroscopic observations. Coarser gratings can be fabricated with these new techniques rather than conventional techniques, allowing observations at very high dispersion orders for larger simultaneous wavelength coverage. We have found new etching techniques for fabricating high quality silicon grisms with low wavefront distortion, low scattered light and high efficiency. Particularly, a new etching process using tetramethyl ammonium hydroxide (TMAH) is significantly simplifying the fabrication process on large, thick silicon substrates, while providing comparable grating quality to our traditional potassium hydroxide (KOH) process. This technique is being used for fabricating inch size silicon grisms for several IR instruments and is planned to be used for fabricating ~ 4 inch size silicon immersion gratings later. We have obtained complete K band spectra of a total of 6 T Tauri and Ae/Be stars and their close companions at a spectral resolution of R ~ 5000 using a silicon echelle grism with a 5 mm pupil diameter at the Lick 3m telescope. These results represent the first scientific observations conducted by the high-resolution silicon grisms, and demonstrate the extremely high dispersing power of silicon- based gratings. The future of

  8. 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.

  9. The high-resolution Echelle Spectrograph of the 6-m telescope of the special astrophysical observatory

    NASA Astrophysics Data System (ADS)

    Panchuk, V. E.; Klochkova, V. G.; Yushkin, M. V.

    2017-09-01

    Results of the development and implementation of the Nasmyth Echelle Spectrograph (NES) of the 6-m telescope of the Special AstrophysicalObservatory are presented. The NES is a tunable spectral system with a large-diameter collimated beam that is suitable for various types of observations. Selected scientific programs carried out by the developers of the instrument are described as illustrations of its application. The possible development of the spectrograph with the 6-m telescope over the coming 19 years is discussed.

  10. 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%.

  11. Adaptive optics high-resolution IR spectroscopy with silicon grisms and immersion gratings

    NASA Astrophysics Data System (ADS)

    Ge, Jian; McDavitt, Daniel L.; Chakraborty, Abhijit; Bernecker, John L.; Miller, Shane

    2003-02-01

    The breakthrough of silicon immersion grating technology at Penn State has the ability to revolutionize high-resolution infrared spectroscopy when it is coupled with adaptive optics at large ground-based telescopes. Fabrication of high quality silicon grism and immersion gratings up to 2 inches in dimension, less than 1% integrated scattered light, and diffraction-limited performance becomes a routine process thanks to newly developed techniques. Silicon immersion gratings with etched dimensions of ~ 4 inches are being developed at Penn State. These immersion gratings will be able to provide a diffraction-limited spectral resolution of R = 300,000 at 2.2 micron, or 130,000 at 4.6 micron. Prototype silicon grisms have been successfully used in initial scientific observations at the Lick 3m telescope with adaptive optics. Complete K band spectra of a total of 6 T Tauri and Ae/Be stars and their close companions at a spectral resolution of R ~ 3000 were obtained. This resolving power was achieved by using a silicon echelle grism with a 5 mm pupil diameter in an IR camera. These results represent the first scientific observations conducted by the high-resolution silicon grisms, and demonstrate the extremely high dispersing power of silicon-based gratings. New discoveries from this high spatial and spectral resolution IR spectroscopy will be reported. The future of silicon-based grating applications in ground-based AO IR instruments is promising. Silicon immersion gratings will make very high-resolution spectroscopy (R > 100,000) feasible with compact instruments for implementation on large telescopes. Silicon grisms will offer an efficient way to implement low-cost medium to high resolution IR spectroscopy (R ~ 1000-50000) through the conversion of existing cameras into spectrometers by locating a grism in the instrument's pupil location.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Grating interferometer for flatness testing.

    PubMed

    de Groot, P J

    1996-02-01

    Two diffraction gratings placed in front of a f lat surface generate an interference pattern representing the surface deformations. The interference pattern is achromatic and has an equivalent wavelength between 4 and 40 microm, depending on the grating frequencies and the viewing angle. Using phase-shifting techniques, the grating interferometer provides high-precision profile measurements of both smooth and rough surfaces.

  19. 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.

  20. 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.

  1. 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.

  2. Sensored fiber reinforced polymer grate

    DOEpatents

    Ross, Michael P.; Mack, Thomas Kimball

    2017-08-01

    Various technologies described herein pertain to a sensored grate that can be utilized for various security fencing applications. The sensored grate includes a grate framework and an embedded optical fiber. The grate framework is formed of a molded polymer such as, for instance, molded fiber reinforced polymer. Further, the grate framework includes a set of elongated elements, where the elongated elements are spaced to define apertures through the grate framework. The optical fiber is embedded in the elongated elements of the grate framework. Moreover, bending or breaking of one or more of the elongated elements can be detected based on a change in a characteristic of input light provided to the optical fiber compared to output light received from the optical fiber.

  3. Optical fiber Bragg gratings. Part II. Modeling of finite-length gratings and grating arrays

    NASA Astrophysics Data System (ADS)

    Passaro, Vittorio M. N.; Diana, Roberto; Armenise, Mario N.

    2002-09-01

    A model of both uniform finite-length optical fiber Bragg gratings and grating arrays is presented. The model is based on the Floquet-Bloch formalism and allows rigorous investigation of all the physical aspects in either single- or multiple-periodic structures realized on the core of a monomodal fiber. Analytical expressions of reflectivity and transmittivity for both single gratings and grating arrays are derived. The influence of the grating length and the index modulation amplitude on the reflected and transmitted optical power for both sinusoidal and rectangular profiles is evaluated. Good agreement between our method and the well-known coupled-mode theory (CMT) approach has been observed for both single gratings and grating arrays only in the case of weak index perturbation. Significant discrepancies exist there in cases of strong index contrast because of the increasing approximation of the CMT approach. The effects of intragrating phase shift are also shown and discussed.

  4. FIEStool: Automated data reduction for FIber-fed Echelle Spectrograph (FIES)

    NASA Astrophysics Data System (ADS)

    Stempels, Eric; Telting, John

    2017-08-01

    FIEStool automatically reduces data obtained with the FIber-fed Echelle Spectrograph (FIES) at the Nordic Optical Telescope, a high-resolution spectrograph available on a stand-by basis, while also allowing the basic properties of the reduction to be controlled in real time by the user. It provides a Graphical User Interface and offers bias subtraction, flat-fielding, scattered-light subtraction, and specialized reduction tasks from the external packages IRAF (ascl:9911.002) and NumArray. The core of FIEStool is instrument-independent; the software, written in Python, could with minor modifications also be used for automatic reduction of data from other instruments.

  5. 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.

  6. Asymmetric acoustic gratings

    NASA Astrophysics Data System (ADS)

    He, Zhaojian; Peng, Shasha; Ye, Yangtao; Dai, Zhongwei; Qiu, Chunyin; Ke, Manzhu; Liu, Zhengyou

    2011-02-01

    The unidirectional transmission of acoustic waves is realized by a simple geometrically asymmetric steel grating structure. This exotic phenomenon stems from the one-way diffraction effect induced by the different periods of the slits on the both surfaces of the sample. And the frequency range of unidirectional transmission is simply determined by the structure periods. The experimental results agree well with the theoretical simulation. This remarkable effect is expected potential applications in ultrasonic devices, such as acoustic rectifiers and acoustic diodes.

  7. 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.

  8. Grating-based red lasers

    NASA Astrophysics Data System (ADS)

    Pezeshki, Bardia; Hagberg, Mats; Zelinski, Michael; Zou, Sarah; Kolev, Emil I.

    1999-04-01

    We have demonstrated a number of high power and single- frequency lasers at 635 - 680 nm by incorporating a grating reflector within the device, including DBRs, tunable DBRs, monolithic MOPAs, DFBs, and angled-grating DFBs. The DBR laser, with an unpumped grating as the rear reflector, is the simplest single-frequency structure, with about 20 mW output power. The device can be tuned about 3 nm by injecting current in the rear grating. Higher output power can be obtained by combining the DBR with a flared amplifier to form a monolithic MOPA with over 250 mW CW output power. Unlike DBR structures, the DFBs have a grating throughout their gain region, and therefore show no mode hops. Wavelengths as short as 634 nm and output powers as high as 90 mW have been obtained with DFBs. An angle-grating DFB is a broad area device where the angled grating forces lasing in a single spatial and longitudinal mode. More than 400 mW in single-frequency power has been obtained at 660 nm from such a structure. In general, grating-based red lasers are useful for interferometry, spectroscopy, and fiber-coupling applications.

  9. Fibre gratings and their applications

    SciTech Connect

    Vasil'ev, Sergei A; Medvedkov, O I; Korolev, I G; Bozhkov, A S; Kurkov, Andrei S; Dianov, Evgenii M

    2005-12-31

    A brief review is given of the state of the art in the research on the photosensitivity of fibres and photoinduced fibre gratings. The most important properties of fibre gratings are considered and the main methods of their production and their applications are discussed. The photosensitive compositions of silica glasses are presented and methods for increasing their photosensitivity are indicated. (review)

  10. Characterization of an InGaAs/InP-based Echelle mirror multiplexer for widely-tunable mid-IR sources based on quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Orbe, L. J.; Carpintero, G.; Gilles, C.; Boulila, F.; Maisons, G.; Carras, M.

    2015-03-01

    We present the experimental characterization results of a 15-to-1 wavelength multiplexer for a Distributed Feedback Quantum Cascade Laser (DFB QCL) array operating in the 7-8.5 μm (mid-long) infrared (IR) range. This design is customized for its use to combine the output from a DFB QCL array with a 0.1 μm wavelength channel spacing for spectroscopy applications, and it is proposed in order to achieve a continuous tuning range overcoming the limited tunability of a single QCLs, required for multi-gas or complex molecule detection. This multiplexer is based on an Echelle diffraction mirror grating scheme, in which multiple output waveguides are deliberately implemented in the design to de-risk for wavelength deviations in the fabrication process. We optimized the location of the input and output guides in order to allow for monolithic integration of the DFB QCL arrays, which would provide for a number of advantages such as a higher stability, less complexity and lower cost over other technologies such as external cavities. We discuss the effects over the device performance of the design, such as the diffraction effects, input channel width overlapping/crosstalk and input channel profile, which are very important to address in order to avoid unaccounted transmission losses. Other parameters such as the profile of the input and output waveguides and fabrication limitations are also discussed as their effect on the device is observed. A series of characterization tests are presented in order to compare the simulation results to the experimental data, which suggests that these multiplexers are a suitable option compared to other IR multiplexer schemes in terms of size and power transmission.

  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. 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.

  13. The Coude spectrograph and echelle scanner of the 2.7 m telescope at McDonald observatory

    NASA Technical Reports Server (NTRS)

    Tull, R. G.

    1972-01-01

    The design of the Coude spectrograph of the 2.7 m McDonald telescope is discussed. A description is given of the Coude scanner which uses the spectrograph optics, the configuration of the large echelle and the computer scanner control and data systems.

  14. Modelling long-range wavelength distortions in quasar absorption echelle spectra

    NASA Astrophysics Data System (ADS)

    Dumont, V.; Webb, J. K.

    2017-06-01

    Spectra observed with the Ultraviolet and Visual Echelle Spectrograph on the European Southern Observatory's VLT exhibit long-range wavelength distortions. These distortions impose a systematic error on high-precision measurements of the fine-structure constant, α, derived from intervening quasar absorption systems. If the distortion is modelled using a model that is too simplistic, the resulting bias in Δα/α away from the true value can be larger than the statistical uncertainty on the α measurement. If the effect is ignored altogether, the same is true. If the effect is modelled properly, accounting for the way in which final spectra are generally formed from the co-addition of exposures made at several different instrumental settings, the effect can be accurately removed and the correct Δα/α recovered.

  15. 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.

  16. 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.

  17. ESPRESSO — An Echelle SPectrograph for Rocky Exoplanets Search and Stable Spectroscopic Observations

    NASA Astrophysics Data System (ADS)

    Pepe, F.; Cristiani, S.; Rebolo, R.; Santos, N. C.; Dekker, H.; Mégevand, D.; Zerbi, F. M.; Cabral, A.; Molaro, P.; Di Marcantonio, P.; Abreu, M.; Affolter, M.; Aliverti, M.; Allende Prieto, C.; Amate, M.; Avila, G.; Baldini, V.; Bristow, P.; Broeg, C.; Cirami, R.; Coelho, J.; Conconi, P.; Coretti, I.; Cupani, G.; D'Odorico, V.; De Caprio, V.; Delabre, B.; Dorn, R.; Figueira, P.; Fragoso, A.; Galeotta, S.; Genolet, L.; Gomes, R.; González Hernández, J. I.; Hughes, I.; Iwert, O.; Kerber, F.; Landoni, M.; Lizon, J.-L.; Lovis, C.; Maire, C.; Mannetta, M.; Martins, C.; Monteiro, M. A.; Oliveira, A.; Poretti, E.; Rasilla, J. L.; Riva, M.; Santana Tschudi, S.; Santos, P.; Sosnowska, D.; Sousa, S.; Spanò, P.; Tenegi, F.; Toso, G.; Vanzella, E.; Viel, M.; Zapatero Osorio, M. R.

    2013-09-01

    ESPRESSO is the next generation European exoplanet hunter, combining the efficiency of a modern echelle spectrograph with extreme radial velocity and spectroscopic precision. ESPRESSO will be installed in the Combined Coudé Laboratory of the VLT and linked to the four Unit Telescopes (UT) through optical coudé trains, operated either with a single UT or with up to four UTs for 1.5 magnitude gain. The instrumental radial velocity precision will reach the 10 cm s-1 level and ESPRESSO will achieve a gain of two magnitudes with respect to its predecessor HARPS. This is the first VLT instrument using the incoherent combination of light from four telescopes and, together with the extreme precision requirements, calls for many innovative design solutions while ensuring the technical heritage of HARPS.

  18. 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.

  19. 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.

  20. 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.

  1. Time- and frequency-domain models for Smith-Purcell radiation from a two-dimensional charge moving above a finite length grating

    SciTech Connect

    Kesar, Amit S.; Hess, Mark; Korbly, Stephen E.; Temkin, Richard J.

    2005-01-01

    Smith-Purcell radiation (SPR), formed by an electron beam traveling above a grating, is a very promising source of coherent radiation from the THz to the optical regime. We present two theoretical calculations of the SPR from a two-dimensional bunch of relativistic electrons passing above a grating of finite length. The first calculation uses the finite-difference time-domain approach with the total-field/scattered-field procedure for fields incident on the grating. This calculation allows good physical insight into the radiation process and also allows arbitrary geometries to be treated. The second calculation uses an electric-field integral equation method. Good agreement is obtained between these two calculations. The results of these theoretical calculations are then compared with a theoretical formalism based on an infinite-length grating. The latter formalism allows periodic boundary conditions to be rigorously applied. For gratings with less than {approx}50 periods, a significant error in the strength of the radiated field is introduced by the infinite-grating approximation. It is shown that this error disappears asymptotically as the number of periods increases. The Wood-Rayleigh anomalies, predicted in the infinite-grating approximation, were not seen in our finite-grating calculations. The SPR resonance condition is the same in all three formalisms. Numerical examples are presented for an {approx}18 MeV, 50 nC/m, 200 {mu}m bunch traveling 0.6 mm above a ten-period echelle grating having a 2.1-mm periodicity.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. StarCAT: A CATALOG OF SPACE TELESCOPE IMAGING SPECTROGRAPH ULTRAVIOLET ECHELLE SPECTRA OF STARS

    SciTech Connect

    Ayres, Thomas R.

    2010-03-01

    StarCAT is a catalog of high resolution ultraviolet spectra of objects classified as 'stars', recorded by Space Telescope Imaging Spectrograph (STIS) during its initial seven years of operations (1997-2004). StarCAT is based on 3184 echelle observations of 545 distinct targets, with a total exposure duration of 5.2 Ms. For many of the objects, broad ultraviolet coverage has been achieved by splicing echellegrams taken in two or more FUV (1150-1700 A) and/or NUV (1600-3100 A) settings. In cases of multiple pointings on conspicuously variable sources, spectra were separated into independent epochs. Otherwise, different epochs were combined to enhance the signal-to-noise ratio (S/N). A post-facto correction to the calstis pipeline data sets compensated for subtle wavelength distortions identified in a previous study of the STIS calibration lamps. An internal 'fluxing' procedure yielded coherent spectral energy distributions (SEDs) for objects with broadly overlapping wavelength coverage. The best StarCAT material achieves 300 m s{sup -1} internal velocity precision; absolute accuracy at the 1 km s{sup -1} level; photometric accuracy of order 4%; and relative flux precision several times better (limited mainly by knowledge of SEDs of UV standard stars). While StarCAT represents a milestone in the large-scale post-processing of STIS echellegrams, a number of potential improvements in the underlying 'final' pipeline are identified.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. A New Large Echelle Spectrometer for Measuring Atomic Transition Probabilities of Fe-group Ions

    NASA Astrophysics Data System (ADS)

    Wood, Michael; Lawler, J. E.

    2012-01-01

    Accurate atomic transition probabilities for weak lines connected to the ground and low metastable levels of Fe-group ions are needed for elemental abundance studies on metal-poor stars. Metal-poor stars represent the oldest observable stellar generation and offer a direct probe into the early history of nucleosynthesis and the chemical evolution of the Galaxy. Unexplained trends in relative Fe-group abundances, such as [Co/Cr], as a function of metallicity, or [Fe/H], have been observed. These trends may result from a breakdown in the local thermodynamic equilibrium (LTE) approximation used in traditional photosphere models underlying elemental abundance determinations. The ground and low metastable levels of Fe-group ions contain most of the Fe-group material in a stellar photosphere, and thus second spectra lines with low E.P.s are essentially immune to non-LTE effects. To improve lab data on important Fe-group lines we have developed a novel instrument based on a 3 meter focal length vacuum echelle spectrograph combined with an aberration corrected cross dispersion system and a UV sensitive CCD array. This spectrometer is capable of recording both emission and absorption spectra with high resolving power, very broad wavelength coverage, and high signal-to-noise. It is also free from the multiplex noise of a FTS, making it ideally suited for measuring branching fractions of very weak lines. The combination of very accurate branching fractions with radiative lifetimes from time-resolved laser-induced fluorescence will yield accurate absolute transition probabilities of weak second spectra lines with low E.P.s for the Fe-group elements. Instrument design and preliminary results will be presented. Supported by NASA Grant NNX09AL13G.

  2. Cool stars: spectral library of high-resolution echelle spectra and database of stellar parameters

    NASA Astrophysics Data System (ADS)

    Montes, D.

    2013-05-01

    During the last years our group have undertake several high resolution spectroscopic surveys of nearby FGKM stars with different spectrographs (FOCES, SARG, SOFIN, FIES, HERMES). A large number of stars have been already observed and we have already determined spectral types, rotational velocities as well as radial velocities, Lithium abundance and several chromospheric activity indicators. We are working now in a homogeneous determination of the fundamental stellar parameters (T_{eff}, log{g}, ξ and [Fe/H]) and chemical abundances of many elements of all these stars. Some fully reduced spectra in FITS format have been available via ftp and in the {http://www.ucm.es/info/Astrof/invest/actividad/spectra.html}{Worl Wide Web} (Montes et al. 1997, A&AS, 123, 473; Montes et al. 1998, A&AS, 128, 485; and Montes et al. 1999, ApJS, 123, 283) and some particular spectral regions of the echelle spectra are available at VizieR by López-Santiago et al. 2010, A&A, 514, A97. We are now working in made accessible all the spectra of our different surveys in a Virtual Observatory ({http://svo.cab.inta-csic.es/}{VO}) compliant library and database accessible using a common web interface following the standards of the International Virtual Observatory Alliance ({http://www.ivoa.net/}{IVOA}). The spectral library includes F, G, K and M field stars, from dwarfs to giants. The spectral coverage is from 3800 to 10000 Å, with spectral resolution ranging from 40000 to 80000. The database will provide in addition the stellar parameters determined for these spectra using {http://cdsads.u-strasbg.fr/abs/2012arXiv1205.4879T}{StePar} (Tabernero et al. 2012, A&A, 547, A13).

  3. Diffraction pattern of gratings with erosion

    NASA Astrophysics Data System (ADS)

    Olivares-Pérez, Arturo; Fuentes-Tapia, Israel

    2015-03-01

    We present a theoretical study of amplitude diffraction gratings using computer simulating, which consists of a random sampling of points on the image grating to determine the points to be plotted and the points to remove, to simulate erosion in amplitude on the grating. We show their behavior in the diffraction patterns and the induced noise by limiting the number of points that representing the image of the eroded gratings and their symmetry.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Holographic Gratings for Slow-Neutron Optics

    PubMed Central

    Klepp, Juergen; Pruner, Christian; Tomita, Yasuo; Geltenbort, Peter; Drevenšek-Olenik, Irena; Gyergyek, Saso; Kohlbrecher, Joachim; Fally, Martin

    2012-01-01

    Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based on holographic gratings are discussed.

  9. 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

    2017-06-01

    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.

  10. 21 CFR 133.146 - Grated cheeses.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Grated cheeses. 133.146 Section 133.146 Food and... CONSUMPTION CHEESES AND RELATED CHEESE PRODUCTS Requirements for Specific Standardized Cheese and Related Products § 133.146 Grated cheeses. (a) Description. Grated cheeses is the class of foods prepared by...

  11. 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

  12. 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.

  13. 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.

  14. Compact Imaging Spectrometer Utilizing Immersed Gratings

    DOEpatents

    Chrisp, Michael P.; Lerner, Scott A.; Kuzmenko, Paul J.; Bennett, Charles L.

    2006-03-21

    A compact imaging spectrometer with an immersive diffraction grating that compensates optical distortions. The imaging spectrometer comprises an entrance slit for transmitting light, a system for receiving the light and directing the light, an immersion grating, and a detector array. The entrance slit, the system for receiving the light, the immersion grating, and the detector array are positioned wherein the entrance slit transmits light to the system for receiving the light and the system for receiving the light directs the light to the immersion grating and the immersion grating receives the light and directs the light through an optical element to the detector array.

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

    NASA Astrophysics Data System (ADS)

    Hailey-Dunsheath, S.; Nikola, T.; Stacey, G. J.; Oberst, T.; Parshley, S.; Benford, D. J.; Moseley, S. H.; Staguhn, J. G.

    2004-12-01

    The redshift (Z) and Early Universe Spectrometer (ZEUS) is a long slit echelle grating spectrometer that we are constructing for use in the submillimeter atmospheric transmission windows (350 μ m, 450 μ m, and 610 μ m) on the James Clerk Maxwell Telescope (JCMT). ZEUS has a resolving power of R ≡ λ /Δ λ ˜ 1000, optimized for detecting broad, faint lines from extragalactic sources. The detector will be a 4×64 pixel array of pop-up bolometers (PUD) equipped with superconducting transition edge sensors (TES) linked into a SQUID multiplexed readout. The expected point source sensitivities of the TES PUD at 370 μ m and 444 μ m are 4.3 × 10-17 W m-2Hz-1/2 and 2.4 × 10-17 W m-2Hz-1/2. For our lab testing we are using a 1×32 pixel array of thermistor sensed bolometers from GSFC. This array has delivered the requisite sensitivity and spectral coverage for a successful first light at the JCMT in the 350 μ m and 450 μ m windows. We hope to put ZEUS on the JCMT in the spring of 2005. ZEUS is optimized to quickly obtain spectra of point sources over very broad bands in the submillimeter windows. In the 350 μ m window, ZEUS will provide an instantaneous 53 resolution element spectrum, for each of 4 spatial elements on the sky. The roughly 10% bandwidth 350 μ m window can therefore be covered with just two settings of the grating. Each pixel is mapped into 5'' on the sky (roughly λ /D at 350 μ m), so that the field of view is 5''×20''. At 610 μ m, the slit is opened to 10'' (2 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. Our primary scientific objectives are to (1) Investigate Ultraluminous Infrared Galaxies (ULIGs) via their [C I] and mid-J CO line emission -- what are the origins of their tremendous infrared (IR) luminosities? Why are some ULIGs weak in the 158 μ m [C II] line? (2) Probe star formation in

  16. 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.

  17. The principle of differential grating displacement sensor

    NASA Astrophysics Data System (ADS)

    Chen, Xihou; Peng, Donglin; Zhang, Xinghong; Liu, Xiaokang

    2005-12-01

    Grating type sensor is one of the most important displacement sensors. But the number and the machining precision of their gratings limit the resolution of traditional grating displacement sensor. A new sensor called differential displacement sensor is proposed for the first time. Based on the principle resembling that of vernier calipers, using the scale differential of two staves with relative motion, it can gain more impulses, and achieve the goal of improving resolution. As a new displacement sensor, differential grating displacement sensor has its own characteristic. There are some special factors should be considered and some rules should be followed in designing differential grating sensor. And the parameter choice has a great effect on the performance of the sensor. The design idea, working principle and parameter design rules of differential grating sensor are introduced in details in this paper by making gear grating sensor as an example.

  18. Echelle observations of C III lambda 1909 and Si III lambda 1892. [for solar electron densities and mass motions

    NASA Technical Reports Server (NTRS)

    Allen, M. S.

    1979-01-01

    Profiles of C III 1909 and Si III 1892 obtained on and near the limb during the 1976 flight of the University of Hawaii echelle rocket spectrograph were reduced and analyzed to determine electron densities and mass motions. The electron pressure derived agrees well with that determined by Cook and Nicolas (1979) from ATM data. Nonthermal velocities in the region of formation of Si III 1892 on the disk were found to be 10-12 km/s, somewhat lower than the values obtained by Doschek et al. (1976), also from ATM spectra. However, velocities derived at and above the limb were in closer agreement, about 17 km/s.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. Fixational saccades during grating detection and discrimination.

    PubMed

    Spotorno, Sara; Masson, Guillaume S; Montagnini, Anna

    2016-01-01

    We investigated the patterns of fixational saccades in human observers performing two classical perceptual tasks: grating detection and discrimination. First, participants were asked to detect a vertical or tilted grating with one of three spatial frequencies and one of four luminance contrast levels. In the second experiment, participants had to discriminate the spatial frequency of two supra-threshold gratings. The gratings were always embedded in additive, high- or low-contrast pink noise. We observed that the patterns of fixational saccades were highly idiosyncratic among participants. Moreover, during the grating detection task, the amplitude and the number of saccades were inversely correlated with stimulus visibility. We did not find a systematic relationship between saccade parameters and grating frequency, apart from a slight decrease of saccade amplitude during grating discrimination with higher spatial frequencies. No consistent changes in the number and amplitude of fixational saccades with performance accuracy were reported. Surprisingly, during grating detection, saccade number and amplitude were similar in grating-with-noise and noise-only displays. Grating orientation did not affect substantially saccade direction in either task. The results challenge the idea that, when analyzing low-level spatial properties of visual stimuli, fixational saccades can be adapted in order to extract task-relevant information optimally. Rather, saccadic patterns seem to be overall modulated by task context, stimulus visibility and individual variability. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Fibre gratings for hydrogen sensing

    NASA Astrophysics Data System (ADS)

    Trouillet, Alain; Marin, Emmanuel; Veillas, Colette

    2005-05-01

    Liquid hydrogen has been intensively used in aerospace applications during the past forty years and is of great interest for future automotive applications. Following upon major explosive risks due to the use of hydrogen in air, several studies were carried out in order to develop optical fibre sensors for the detection of hydrogen leakage. This communication is aimed towards the presentation of new sensors based on the use of Fibre Bragg Gratings (FBG) and Long Period Gratings (LPG). The sensing principle based on palladium-hydrogen interaction will be presented as well as experimental results with structures including FBG, LPG or in-series LPG. Detection parameters such as response time and sensitivity will be discussed versus temperature.

  5. 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%.

  6. Athermal silicon subwavelength grating waveguides

    NASA Astrophysics Data System (ADS)

    Ibrahim, M.; Schmid, J. H.; Cheben, P.; Lapointe, J.; Janz, S.; Bock, P. J.; Densmore, A.; Lamontagne, B.; Ma, R.; Xu, D.-X.; Ye, W. N.

    2011-08-01

    In this paper, athermal subwavelength grating (SWG) waveguides are investigated. Both numerical simulations and experimental results show that a temperature independent behaviour can be achieved by combining two materials with opposite thermo-optic coefficients within the waveguide. SU-8 polymer with a negative thermo-optic coefficient (dn/dT = -1.1x10-4 K-1) is used in our silicon SWG waveguides to compensate for silicon's positive thermo-optic coefficient of 1.9x10-4 K-1. The grating duty ratio required to achieve an athermal behavior is reported to vary as a function of the operating wavelength and the waveguide dimensions. For example, for athermal waveguides of 260 nm in height, duty ratios of 61.3% and 83.3% were calculated for TE and TM polarized light respectively for a 450 nm wide waveguide, compared to ratios of 79% and 90% for a 350 nm wide waveguide. It is also reported that with increasing width, and increasing height, a smaller grating duty ratio is necessary to achieve an athermal behaviour. A smaller fraction of silicon would hence be needed to compensate for the polymer's negative thermo-optic effect in the waveguide core. Subwavelength sidewall grating (SWSG) waveguides are also proposed here as alternatives to high duty ratio SWG waveguides that are required for guiding TM polarized light. Assuming a duty ratio of 50%, the width of the narrow segments for temperature-independent behavior is found by numerical simulations to be 125 nm and 143 nm for TE and TM polarized light, respectively.

  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. Affordable echelle spectroscopy of the eccentric HAT-P-2, WASP-14, and XO-3 planetary systems with a sub-meter-class telescope

    NASA Astrophysics Data System (ADS)

    Garai, Z.; Pribulla, T.; Hambálek, Ľ.; Kundra, E.; Vaňko, M.; Raetz, S.; Seeliger, M.; Marka, C.; Gilbert, H.

    2017-01-01

    A new off-shelf low-cost echelle spectrograph was installed recently on the 0.6m telescope at the Star\\'a Lesn\\'a Observatory (Slovakia). In this paper we describe in details the radial velocity (RV) analysis of the first three transiting planetary systems, HAT-P-2, WASP-14 and XO-3, observed with this instrument. Furthermore, we compare our data with the RV data achieved with echelle spectrographs of other sub-meter-, meter- and two-meter-class telescopes in terms of their precision. Finally, we investigate the applicability of our RV data for modeling orbital parameters.

  9. 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.

  10. 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.

  11. 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.

  12. Designing Plasmonic Gratings with Transformation Optics

    NASA Astrophysics Data System (ADS)

    Kraft, Matthias; Luo, Yu; Maier, S. A.; Pendry, J. B.

    2015-07-01

    Plasmonic gratings that support both localized and propagating plasmons have wide applications in solar cells and optical biosensing. In this paper, we report on a most unusual grating designed to capture light efficiently into surface plasmons and concentrate their energy at hot spots where the field is resonantly enhanced. The dispersion of the surface plasmons shows degeneracy points at k =0 , where, despite a strongly modulated grating, hidden symmetries forbid hybridization of plasmons traveling in opposite directions.

  13. 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.

  14. 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.

  15. 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.

  16. Active diffraction gratings: Development and tests

    SciTech Connect

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

    2012-12-15

    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. 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.

  20. 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.

  1. Fabrication and application of subwavelength gratings

    NASA Astrophysics Data System (ADS)

    Schnabel, Bernd; Kley, Ernst-Bernhard

    1997-04-01

    Binary gratings with periods below the wavelength of visible light may be fabricated by e-beam direct writing in a resist layer and then transferred into other materials by ion beam etching. We used a well-adapted e-beam writer 'LION LV1' which allows feature sizes of 100nm and below and arbitrary directions of the grating lines as well as radial, circular or elliptical grating lines. By transfering such gratings into metallic layers polarization effects may be obtained which depend both on the parameters of the gratings and of the metal layer. The dependence of the polarization on grating period and duty cycle was measured for chromium layers with 35nm thickness. By writing concentric circular gratin lines, interesting polarization analyzers may be fabricated. in addition to metal stripe gratings, dielectric subwavelength gratings show interesting properties, too. They may be used for coupling free space light into a planar or rib waveguide with incoupling efficiencies higher than 50 percent. Both for metallic and dielectric gratings, the optical properties strongly depend on an accurate and reproducible fabrication process which, therefore, has to be subject of further research.

  2. 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.

  3. Eliminating the Rayleigh anomalies in metal grating

    NASA Astrophysics Data System (ADS)

    Gao, Hongtao; Yan, Wei; Hu, Song; Zhang, Yudong

    2017-12-01

    We demonstrate that Rayleigh anomalies of some diffraction order of metal reflection gratings and transmission grating can be eliminated. The studied grating consists of a one-dimensional (1-D) periodic rectangular slit array. A systemic rule has been reported that can be used to counteract the infinity of the Green function resulted from working at the Rayleigh cutoff wavelength, by choosing a suitable value of the ratio of the slit width to the period of the grating. Eliminating the Rayleigh anomalies is of intrinsic physical interest as well as of vital concern in the design of the optical element.

  4. Biosensing with optical fiber gratings

    NASA Astrophysics Data System (ADS)

    Chiavaioli, Francesco; Baldini, Francesco; Tombelli, Sara; Trono, Cosimo; Giannetti, Ambra

    2017-06-01

    Optical fiber gratings (OFGs), especially long-period gratings (LPGs) and etched or tilted fiber Bragg gratings (FBGs), are playing an increasing role in the chemical and biochemical sensing based on the measurement of a surface refractive index (RI) change through a label-free configuration. In these devices, the electric field evanescent wave at the fiber/surrounding medium interface changes its optical properties (i.e. intensity and wavelength) as a result of the RI variation due to the interaction between a biological recognition layer deposited over the fiber and the analyte under investigation. The use of OFG-based technology platforms takes the advantages of optical fiber peculiarities, which are hardly offered by the other sensing systems, such as compactness, lightness, high compatibility with optoelectronic devices (both sources and detectors), and multiplexing and remote measurement capability as the signal is spectrally modulated. During the last decade, the growing request in practical applications pushed the technology behind the OFG-based sensors over its limits by means of the deposition of thin film overlays, nanocoatings, and nanostructures, in general. Here, we review efforts toward utilizing these nanomaterials as coatings for high-performance and low-detection limit devices. Moreover, we review the recent development in OFG-based biosensing and identify some of the key challenges for practical applications. While high-performance metrics are starting to be achieved experimentally, there are still open questions pertaining to an effective and reliable detection of small molecules, possibly up to single molecule, sensing in vivo and multi-target detection using OFG-based technology platforms.

  5. 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 }}\

  6. 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 }}\

  7. 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 }}\

  8. 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.

  9. 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.

  10. 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.

  11. Unidirectional complex grating assisted couplers

    NASA Astrophysics Data System (ADS)

    Greenberg, Maxim; Orenstein, Meir

    2004-08-01

    We present a novel concept which enables the realization of unidirectional and irreversible grating assisted couplers by using gain-loss modulated medium to eliminate the reversibility. Employing a matched periodic modulation of both refractive index and loss (gain) we achieve a unidirectional energy transfer between the modes of the coupler which translates to light transmission from one waveguide to another while disabling the inverse transmission. The importance of self coupling coefficients is explored as well and a feasible implementation, where the real and imaginary perturbations are implemented in different waveguides is presented.

  12. 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.

  13. 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.

  14. Holographic Grating Study. Volume 1

    DTIC Science & Technology

    1979-03-01

    This property of the "mixing" HGA produces much greater communication among all parts of the annular beam, leading, potentially, to improved mode...that the relationship between etching depth, in photoresist, Ad, and exposure £ (energy/unit area) is : Ad = T[rl - Ar nxp (-cE)] (11...e.’ 45° T/D - 0.6 en^o» D- V2X Figure 93. Diffraction efficiency design curves: beam sampler or mixing axicon. As the grating period becomes

  15. 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.

  16. 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.

  17. 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…

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Compact imaging spectrometer utilizing immersed gratings

    DOEpatents

    Lerner, Scott A.

    2005-12-20

    A compact imaging spectrometer comprising an entrance slit for directing light, lens means for receiving the light, refracting the light, and focusing the light; an immersed diffraction grating that receives the light from the lens means and defracts the light, the immersed diffraction grating directing the detracted light back to the lens means; and a detector that receives the light from the lens means.

  4. 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…

  5. An experimental investigation of immersed gratings

    NASA Astrophysics Data System (ADS)

    Lee, D.; Allington-Smith, J. R.

    2000-02-01

    A generic problem with spectrographs equipped with conventional diffraction gratings is that the maximum attainable spectral resolution scales inversely with the telescope aperture for a fixed grating dimension and angular slit width. It has long been realized that immersed gratings, where a prism is attached to the surface of a reflection grating, offer a means to bypass this limit. We show how, for the case of the Gemini Multiobject Spectrographs, the maximum spectral resolution may be approximately doubled, or, equivalently, how the same spectral resolution may be obtained with a wider slit, resulting in improved throughput when observing extended objects. After reviewing the theory of immersed gratings, we present experimental verification of the theory and experimentally quantify two potential drawbacks: reduced throughput at blaze, and ghost images. We show that these effects are small and conclude that the benefits greatly outweigh the disadvantages.

  6. Compact imaging spectrometer utilizing immersed gratings

    DOEpatents

    Chrisp, Michael P.; Lerner, Scott A.; Kuzmenko, Paul J.; Bennett, Charles L.

    2007-07-03

    A compact imaging spectrometer with an immersive diffraction grating that compensates optical distortions. The imaging spectrometer comprises an entrance slit for transmitting light, means for receiving the light and directing the light, an immersion grating, and a detector array. The entrance slit, the means for receiving the light, the immersion grating, and the detector array are positioned wherein the entrance slit transmits light to the means for receiving the light and the means for receiving the light directs the light to the immersion grating and the immersion grating receives the light and directs the light to the means for receiving the light, and the means for receiving the light directs the light to the detector array.

  7. Chirped polymer optical fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Marques, Carlos A. F.; Pereira, L.; Antunes, P.; Mergo, P.; Webb, D. J.; Pinto, J. L.; André, P.

    2017-05-01

    We report chirped fiber Bragg gratings (CFBGs) photo-inscribed in undoped PMMA polymer optical fibre (POF) for the first time. The chirped polymer optical fiber Bragg gratings (CPOFBGs) were inscribed using an UV KrF excimer laser operating at 248 nm. The rectangular gauss laser beam was expanded to 25 mm in horizontal direction along the fiber core by a cylindrical lens, giving a total of 25 mm grating length. A 25 mm long chirped phase mask chosen for 1550 nm grating inscription was used. The laser frequency was 1 Hz with an energy of 5 mJ per exposure, exposing few pulses for each grating inscription. The reflection amplitude spectrum evolution of a CPOFBG is investigated as a function of the applied strain and temperature. Also, some results regarding to group delay are collected and discussed. These results pave the way to further developments in different fields, where POFs could present some advantages preferably replacing their silica counterparts.

  8. Polymer micro-fiber Bragg grating.

    PubMed

    Rajan, Ginu; Noor, Muhammad Yusof Mohd; Lovell, Nigel H; Ambikaizrajah, Eliathamby; Farrell, Gerald; Peng, Gang-Ding

    2013-09-01

    Polymer micro-fibers with inscribed Bragg gratings are reported in this Letter. Starting with a single-mode polymer optical fiber and implementing a two-stage tapering process, a 16 μm diameter micro-fiber is fabricated and a Bragg grating is inscribed in it that exhibits a peak reflected wavelength circa 1530 nm. The growth dynamics of the polymer micro-fiber Bragg grating are also observed and analyzed. A maximum reflectivity of 5% is obtained after an exposure time of 3 min to a 50 mW power He-Cd laser of 325 nm wavelength. The temperature and strain characterization results of the micro-fiber Bragg grating with different diameters are also presented. Such polymer micro-fiber Bragg gratings can be used as sensors for high-sensitivity measurements in a number of application areas.

  9. Imaging spectrometer/camera having convex grating

    NASA Technical Reports Server (NTRS)

    Reininger, Francis M. (Inventor)

    2000-01-01

    An imaging spectrometer has fore-optics coupled to a spectral resolving system with an entrance slit extending in a first direction at an imaging location of the fore-optics for receiving the image, a convex diffraction grating for separating the image into a plurality of spectra of predetermined wavelength ranges; a spectrometer array for detecting the spectra; and at least one concave sperical mirror concentric with the diffraction grating for relaying the image from the entrance slit to the diffraction grating and from the diffraction grating to the spectrometer array. In one embodiment, the spectrometer is configured in a lateral mode in which the entrance slit and the spectrometer array are displaced laterally on opposite sides of the diffraction grating in a second direction substantially perpendicular to the first direction. In another embodiment, the spectrometer is combined with a polychromatic imaging camera array disposed adjacent said entrance slit for recording said image.

  10. Manufacture and Development of Multilayer Diffraction Gratings

    SciTech Connect

    Keck, J.; Oliver, J.B.; Kessler, T.J.; Huang, H.; Barone, J.; Hettrick, J.; Rigatti, A.L.; Hoover, T.; Marshall, K.L.; Schmid, A.W.; Kozlov, A.; Kosc, T.Z.

    2006-03-01

    The OMEGA EP Facility includes two high-energy, short-pulse laser beams that will be focused to high intensity in the OMEGA target chamber, providing backlighting of compressed fusion targets and investigating the fast-ignition concept. To produce 2.6 kJ output energy per beam, developments in grating compressor technology are required. Gold-coated diffraction gratings limit on-target energy because of their low damage fluence. Multilayer dielectric (MLD) gratings have shown promise as high-damage-threshold, high-efficiency diffraction gratings suitable for use in high-energy chirped-pulse amplification. This paper details the manufacture and development of these gratings, including the specifics of the MLD coating, holographic lithography, reactive ion etching, reactive ion-beam cleaning, and wet chemical cleaning.

  11. 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.

  12. 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.

  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. 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.

  15. 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.

  16. 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

  17. ZEUS-2: a second generation submillimeter grating spectrometer for exploring distant galaxies

    NASA Astrophysics Data System (ADS)

    Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Irwin, Kent D.; Cho, Hsiao-Mei; Halpern, Mark

    2010-07-01

    ZEUS-2, the second generation (z)Redshift and Early Universe Spectrometer, like its predecessor is a moderate resolution (R~1000) long-slit, echelle grating spectrometer optimized for the detection of faint, broad lines from distant galaxies. It is designed for studying star-formation across cosmic time. ZEUS-2 employs three TES bolometer arrays (555 pixels total) to deliver simultaneous, multi-beam spectra in up to 4 submillimeter windows. The NIST Boulder-built arrays operate at ~100mK and are readout via SQUID multiplexers and the Multi-Channel Electronics from the University of British Columbia. The instrument is cooled via a pulse-tube cooler and two-stage ADR. Various filter configurations give ZEUS-2 access to 7 different telluric windows from 200 to 850 micron enabling the simultaneous mapping of lines from extended sources or the simultaneous detection of the 158 micron [CII] line and the [NII] 122 or 205 micron lines from z = 1-2 galaxies. ZEUS-2 is designed for use on the CSO, APEX and possibly JCMT.

  18. 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.

  19. 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.

  20. 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.

  1. Manufacture and development of multilayer diffraction gratings

    NASA Astrophysics Data System (ADS)

    Keck, J.; Oliver, J. B.; Kessler, T. J.; Huang, H.; Barone, J.; Hettrick, J.; Rigatti, A. L.; Hoover, T.; Marshall, K. L.; Schmid, A. W.; Kozlov, A.; Kosc, T. Z.

    2005-12-01

    The OMEGA EP Facility includes two high-energy, short-pulse laser beams that will be focused to high intensity in the OMEGA target chamber, providing backlighting of compressed fusion targets and investigating the fast-ignition concept. To produce 2.6-kJ output energy per beam, developments in grating compressor technology are required. Gold-coated diffraction gratings limit on-target energy because of their low damage fluence. Multilayer dielectric (MLD) gratings have shown promise as high-damage-threshold, high-efficiency diffraction gratings suitable for use in high-energy chirped-pulse amplification [ B. W. Shore et al., J. Opt. Soc. Am. A 14, 1124 (1997).] Binary 100-mm-diam MLD gratings have been produced at the Laboratory for Laser Energetics (LLE) using large-aperture, holographic exposure and reactive ion-beam etching systems. A diffraction efficiency of greater than 99.5% at 1053 nm has been achieved for gratings with 1740 grooves/mm, with a 1:1 damage threshold of 5.49 J/cm2 diffracted beam fluence at 10 ps. To demonstrate the ability to scale up to larger substrates, several 100-mm substrates have been distributed over an aperture of 47 × 43 cm and successfully etched, resulting in high efficiency over the full aperture. This paper details the manufacture and development of these gratings, including the specifics of the MLD coating, holographic lithography, reactive ion etching, reactive ion-beam cleaning, and wet chemical cleaning.

  2. 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.

  3. 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…

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  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. 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.

  13. 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.

  14. 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

  15. FDM Helmholtz modeling of finite grating and waveguide width effects on resonant subwavelength grating reflectivity.

    SciTech Connect

    Kemme, Shanalyn A.; Peters, David William; Hadley, G. Ronald

    2003-07-01

    Resonant subwavelength gratings (RSGs) may be used as narrow-band wavelength and angular reflectors. Rigorous coupled wave analysis (RCWA) predicts 100% reflectivity at the resonant frequency of an incident plane wave from an RSG of infinite extent. For devices of finite extent or for devices illuminated with a finite beam, the peak reflectivity drops, coupled with a broadening of the peak. More complex numerical methods are required to model these finite effects. We have modeled finite devices and finite beams with a two-dimensional finite difference Helmholtz equation. The effect of finite grating aperture and finite beam size are investigated. Specific cases considered include Gaussian beam illumination of an infinite grating, Gaussian illumination of a finite grating, and plane wave illumination of an apertured grating. For a wide grating with a finite Gaussian beam, it is found that the reflectivity is an exponential function of the grating width. Likewise, for an apertured grating the reflectivity shows an exponential decay with narrowing aperture size. Results are compared to other methods, including plane wave decomposition of Gaussian beams using RCWA for the case of a finite input beam, and a semi-analytical techniques for the case of the apertured grating.

  16. 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.

  17. 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.

  18. Multiperiod-grating surface-emitting lasers

    NASA Technical Reports Server (NTRS)

    Lang, Robert J. (Inventor)

    1992-01-01

    Surface-emitting distributed feedback (DFB) lasers are disclosed with hybrid gratings. A first-order grating is provided at one or both ends of the active region of the laser for retroreflection of light back into the active region, and a second-order or nonresonant grating is provided at the opposite end for coupling light out perpendicular to the surfaces of the laser or in some other selected direction. The gratings may be curved to focus light retroreflected into the active region and to focus light coupled out to a point. When so focused to a point, the DFB laser may be part of a monolithic read head for a laser recorded disk, or an optical coupler into an optical fiber.

  19. 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)

  20. 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.

  1. 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)

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 3D Bragg Grating Waveguide Devices

    NASA Astrophysics Data System (ADS)

    Zhang, Haibin; Herman, Peter R.

    Over the past decade, ultrashort pulse laser processing has opened a large suite of photonic devices that can be formed inside bulk optical glasses by direct writing. Such processes promise rapid and seamless integration into novel three-dimensional optical circuits. One obstacle towards commercial application of this technology has been finding an effective means for inscribing high-quality grating devices. Such gratings, when embedded within the laser written waveguides, enable multi-functional spectral filters to be tailored to specific applications required in optical sensing, fiber lasers, and telecommunications. In this chapter, a new Bragg grating waveguide device is introduced that can be fabricated directly inside transparent glass materials by ultrashort laser direct writing. These Bragg grating waveguide devices are composed of arrays of partially overlapped refractive index voxels (volume pixels), defining a finely pitched segmented waveguide which simultaneously offers low-loss light guiding and strong Bragg filter resonances. Two approaches, a single-pulse writing method and a burst writing method, are introduced for inscribing the grating waveguide devices with respective low-and high-repetition rate ultrashort laser systems. Optimal laser exposure parameters are presented for fabricating high rejection notch filters (>35 dB) with narrow spectral bandwidth (0.2 nm) in the 1550-nm telecom band. Examples of Bragg grating waveguide circuits are presented for filter and sensor applications.

  8. Dual-twist fiber long period gratings

    NASA Astrophysics Data System (ADS)

    Churikov, Victor M.; Kopp, Victor I.; Genack, A. Z.

    2009-02-01

    Long period fiber gratings couple core and co-propagating cladding modes to produce dips in the transmission spectrum and have been widely utilized as sensors and filters. We have recently developed a new approach to long period fiber gratings utilizing optical fibers, which are uniformly twisted at elevated temperatures to produce double or single helices. Because these fibers are not manufactured by exposing photosensitive glass to patterned UV illumination, as is the case for traditional fiber Bragg gratings (FBGs) or long period gratings (LPGs), they are more robust in harsh thermal and chemical environments. Double helix fibers are polarization sensitive and are fabricated by twisting fiber preforms with high-index noncircular cores while single helix gratings are polarization insensitive and are created by twisting standard optical fibers with cores that are not perfectly centered. Here, we present a new approach to single-helix chiral long-period gratings (CLPGs). The CLPG is created in a glassforming process in which two optical fibers are twisted together to form a helix in the signal fiber as the fibers pass through a miniature oven. "Dual-twist" CLPGs may be fabricated from any conventional or specialty fiber and provide reproducible spectra that may be tailored to specific applications.

  9. 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.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Comparison of precipitable water vapour measurements made with an optical echelle spectrograph and an infrared radiometer at Las Campanas Observatory

    NASA Astrophysics Data System (ADS)

    Querel, Richard R.; Naylor, David A.; Thomas-Osip, Joanna; Prieto, Gabriel; McWilliam, Andrew

    2008-07-01

    We present simultaneous precipitable water vapour (PWV) measurements made at the Las Campanas Observatory in late 2007 using an Infrared Radiometer for Millimetre Astronomy (IRMA) and the Magellan Inamori Kyocera Echelle (MIKE) optical spectrograph. Opacity due to water vapour is the primary concern for ground based infrared astronomy. IRMA has been developed to measure the emission of rotational transitions of water vapour across a narrow spectral region centred around 20 μm, using a 0.1 m off-axis parabolic mirror and a sophisticated atmospheric model to retrieve PWV. In contrast, the MIKE instrument is used in conjunction with the 6.5 m Magellan Clay telescope, and determines the PWV through absorption measurements of water vapour lines in the spectra of telluric standard stars. With its high spectral resolution, MIKE is able to measure absorption from optically thin water vapour lines and can derive PWV values using a simple, single layer atmospheric model. In an attempt to improve the MIKE derived PWV measurements, we explore the potential of fitting a series of MIKE water vapour line measurements, having different opacities.

  16. 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.

  17. Surface-relief and polarization gratings for solar concentrators.

    PubMed

    de Jong, Ties M; de Boer, Dick K G; Bastiaansen, Cees W M

    2011-08-01

    Transmission gratings that combine a large diffraction angle with a high diffraction efficiency and a low angular and wavelength dispersion could be used to collect sunlight in a light guide. In this paper we compare the diffractive properties of polarization gratings and classical surface-relief gratings and explore their possible use in solar concentrators. It is found that polarization gratings and surface-relief gratings have qualitatively comparable diffraction characteristics when their thickness parameters are within the same regime. Relatively large grating periods result in high diffraction efficiencies over a wide range of incident angles. For small grating periods the efficiency and the angular acceptance are decreased. Surface-relief gratings are preferred over polarization gratings as in-couplers for solar concentrators.

  18. Analysis of grating doublets for achromatic beam-splitting.

    PubMed

    Pacheco, Shaun; Milster, Tom; Liang, Rongguang

    2015-08-24

    Achromatic beam-splitting grating doublets are designed for both continuous phase and binary phase gratings. By analyzing the sensitivity to lateral shifts between the two grating layers, it is shown that continuous-profile grating doublets are extremely difficult to fabricate. Achromatic grating doublets that have profiles with a constant first spatial derivative are significantly more resistant to lateral shifts between grating layers, where one design case showed a 17 times improvement in performance. Therefore, binary phase, multi-level phase, and blazed grating doublets perform significantly better than continuous phase grating doublets in the presence of a lateral shift between two grating layers. By studying the sensitivity to fabrication errors in the height of both grating layers, one grating layer height can be adjusted to maintain excellent performance over a large wavelength range if the other grating layer is fabricated incorrectly. It is shown in one design case that the performance of an achromatic Dammann grating doublet can be improved by a factor of 215 if the heights of the grating layers are chosen to minimize the performance change in the presence of fabrication errors.

  19. Analysis of grating doublets for achromatic beam-splitting

    PubMed Central

    Pacheco, Shaun; Milster, Tom; Liang, Rongguang

    2015-01-01

    Achromatic beam-splitting grating doublets are designed for both continuous phase and binary phase gratings. By analyzing the sensitivity to lateral shifts between the two grating layers, it is shown that continuous-profile grating doublets are extremely difficult to fabricate. Achromatic grating doublets that have profiles with a constant first spatial derivative are significantly more resistant to lateral shifts between grating layers, where one design case showed a 17 times improvement in performance. Therefore, binary phase, multi-level phase, and blazed grating doublets perform significantly better than continuous phase grating doublets in the presence of a lateral shift between two grating layers. By studying the sensitivity to fabrication errors in the height of both grating layers, one grating layer height can be adjusted to maintain excellent performance over a large wavelength range if the other grating layer is fabricated incorrectly. It is shown in one design case that the performance of an achromatic Dammann grating doublet can be improved by a factor of 215 if the heights of the grating layers are chosen to minimize the performance change in the presence of fabrication errors. PMID:26368261

  20. 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.

  1. Grating-Outcoupled Radiation in Second-Order Fiber Bragg Gratings

    NASA Astrophysics Data System (ADS)

    Sun, Nai-Hsiang; Hu, Chia-Ming; Chiang, Jung-Sheng; Liu, Wen-Fung; Liau, Jiun-Jie; Lin, Shih-Chiang; Evans, Gary A.; Butler, Jerome K.

    2014-01-01

    The experimental results of the radiation for second-order fiber Bragg gratings, which are made of a single-mode photosensitive fiber (PS-1500; Fiber-Core Corp.) and a single-mode fiber (SMF-28; Corning Inc.), by a phase mask writing fabrication technique are explored. For PS-1500 fiber Bragg gratings, the maximum radiation efficiency of -23.5 dB at resonance λ = 1,539.34 nm with a very narrow bandwidth (about 0.02 nm) are measured from a 10-mm-diameter photo-detector, while for SMF-28 fiber Bragg gratings, the maximum radiation efficiency is -34.6 dB (λ = 1,538.03 nm) with a bandwidth of 0.06 nm. The total efficiencies of the radiation are about -16.8 dB for PS-1500 fiber Bragg gratings and -28.1 dB for SMF-28 fiber Bragg gratings.

  2. Fiber Bragg grating sensor demodulation technique by synthesis of grating parameters from its reflection spectrum

    NASA Astrophysics Data System (ADS)

    Caucheteur, Christophe; Lhommé, Frédéric; Chah, Karima; Blondel, Michel; Mégret, Patrice

    2004-10-01

    In this paper, we present a very reliable simulating algorithm to synthesize the physical parameters of a fiber Bragg grating structure from its reflection spectrum. The knowledge of the gratings parameters allows the determination of the maximum wavelength. The algorithm is then tested to monitor the shift of the central wavelength in response to a change of temperature. Our numerical program uses the transfer matrix method and the Nelder-Mead simplex algorithm. It can be easily implemented in the case of twin Bragg gratings. A twin grating is composed of two identical gratings separated by a short length of fiber. The demodulation technique has been tested experimentally with temperature sensors. It is very accurate and provides absolute measurements.

  3. 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).

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. The planet search program at the ESO Coudé Echelle spectrometer. III. The complete Long Camera survey results

    NASA Astrophysics Data System (ADS)

    Endl, M.; Kürster, M.; Els, S.; Hatzes, A. P.; Cochran, W. D.; Dennerl, K.; Döbereiner, S.

    2002-09-01

    We present the complete results of the planet search program carried out at the ESO Coudé Echelle Spectrometer (CES) on La Silla, using the Long Camera from Nov. 1992 to April 1998. The CES survey has monitored 37 late-type (F8V - M5V) stars in the southern hemisphere for variations in their differential radial velocities (RV) in order to detect Doppler reflex motions caused by planetary companions. This led to the discovery of the first extrasolar planet in an Earth-like orbit around the young (ZAMS) and active G0V star iota Horologii (Kürster et al. \\cite{martin00}). Here we present the RV results for all survey stars and perform a statistical examination of the whole data-set. Each star is tested for RV variability, RV trends (linear and non-linear) and significant periodic signals. beta Hyi and epsilon Ind are identified as long-term, low-amplitude RV variables. Furthermore, for 30 CES survey stars we determine quantitative upper mass-limits for giant planets based on our long-term RV results. We find that the CES Long Camera survey would have detected short-period (``51 Peg-type'') planets around all 30 stars but no planets with msin i < 1 {M}_Jup at orbital separations larger than 2 AU. Finally, we demonstrate that the CES planet search can be continued without applying velocity corrections to the RV results coming from the currently installed Very Long Camera at the CES. Based on observations collected at the European Southern Observatory, La Silla. Appendices A and B are only available in electronic form at http://www.edpsciences.org

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Inverse electromagnetic diffraction by biperiodic dielectric gratings

    NASA Astrophysics Data System (ADS)

    Jiang, Xue; Li, Peijun

    2017-08-01

    Consider the incidence of a time-harmonic electromagnetic plane wave onto a biperiodic dielectric grating, where the surface is assumed to be a small and smooth perturbation of a plane. The diffraction is modeled as a transmission problem for Maxwell’s equations in three dimensions. This paper concerns the inverse diffraction problem which is to reconstruct the grating surface from either the diffracted field or the transmitted field. A novel approach is developed to solve the challenging nonlinear and ill-posed inverse problem. The method requires only a single incident field and is realized via the fast Fourier transform. Numerical results show that it is simple, fast, and stable to reconstruct biperiodic dielectric grating surfaces with super-resolved resolution.

  20. Development of Aspherical Active Gratings at NSRRC

    NASA Astrophysics Data System (ADS)

    Tseng, Tse-Chuan; Wang, Duan Jen; Perng, Shen-Yaw; Chen, Chien-Te; Lin, Chia-Jui; Kuan, Chien-Kuang; Ho, His-Chou; Wang, Jeremy; Fung, H. S.; Chang, Shuo-Hung

    2007-01-01

    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.

  1. 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.

  2. 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

  3. Photorefractive optical fuzzy-logic processor based on grating degeneracy

    NASA Astrophysics Data System (ADS)

    Wu, Weishu; Yang, Changxi; Campbell, Scott; Yeh, Pochi

    1995-04-01

    A novel optical fuzzy-logic processor using light-induced gratings in photorefractive crystals is proposed and demonstrated. By exploiting grating degeneracy, one can easily implement parallel fuzzy-logic functions in disjunctive normal form.

  4. Theoretical investigation and optimization of fiber grating based slow light

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Wang, Peng; Du, Chao; Li, Jin; Hu, Haifeng; Zhao, Yong

    2017-07-01

    On the edge of bandgap in a fiber grating, narrow peaks of high transimittivity exist at frequencies where light interferes constructively in the forward direction. In the vicinity of these transmittivity peaks, light reflects back and forth numerous times across the periodic structure and experiences a large group delay. In order to generate the extremely slow light in fiber grating for applications, in this research, the common sense of formation mechanism of slow light in fiber grating was introduced. The means of producing and operating fiber grating was studied to support structural slow light with a group index that can be in principle as high as several thousand. The simulations proceeded by transfer matrix method in the paper were presented to elucidate how the fiber grating parameters effect group refractive index. The main parameters that need to be optimized include grating length, refractive index contrast, grating period, loss coefficient, chirp and apodization functions, those can influence fiber grating characteristics.

  5. Spatial dispersion for diffraction grating based optical systems

    NASA Astrophysics Data System (ADS)

    Zahid, Ali; Dai, Bo; Sheng, Bin; Hong, Ruijin; Wang, Qi; Zhang, Dawei; Wang, Xu

    2016-01-01

    Diffraction gratings are key components in many applications including pulse compression and stretch, optical imaging, spectral encoding and decoding and optical filtering. In this paper, spatial dispersion of two typical diffraction grating-based optical systems, single-grating system and grating-pair system, are thoroughly studied. The single-grating system consists of a diffraction grating to disperse the quasi-monochromatic lights and a convex lens to make the lights propagate in parallel and focused. In the grating-pair system, a pair of diffraction gratings is used to disperse the collimated lights in parallel. The spatial dispersion law for the two systems is developed and summarized. By investigating the spatial dispersion, the two systems are compared and discussed in detail.

  6. 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.

  7. 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.

  8. 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%.

  9. 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.

  10. 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.

  11. Multilayer with periodic grating based high performance SPR waveguide sensor

    NASA Astrophysics Data System (ADS)

    Teotia, Pradeep Kumar; Kaler, R. S.

    2017-07-01

    We propose a high performance periodic grating coupled multi-layered surface plasmon resonance (SPR) waveguide based on Al+Au. High sensitivity is obtained by using grating filled with silver instead of air. Further sensor's performance is analysed by optimising width and thickness of SPR active metal layer as well as grating period also. Using finite difference time domain (FDTD) method, we have shown that sensitivity and detection accuracy can be improvised using appropriate multi-layered grating configuration.

  12. Terahertz quantum well photodetectors with reflection-grating couplers

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  13. 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.

  14. Spherical grating based x-ray Talbot interferometry.

    PubMed

    Cong, Wenxiang; Xi, Yan; Wang, Ge

    2015-11-01

    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. 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. 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. 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 improves both signal visibility and dose

  15. 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.

  16. 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.

  17. A Composite Grating for Moire Interferometry.

    DTIC Science & Technology

    1987-07-01

    investiqation, a 1200/300 lines/mm composite qratinq was chosen. First, a virtual qratinq of frequency of f=300 lines/mm was produced and recorded on a...The optical setup was then changed to a virtual frequency grating of f=1200 6 lines/mm and the photographic plate was exposed again with a laser power...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

  18. 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.

  19. 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

  20. 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.

  1. Interferometric fiber Bragg grating shift demodulation

    NASA Astrophysics Data System (ADS)

    Stepien, Karol; Jóźwik, Michalina; Nasilowski, Tomasz

    2015-09-01

    In this paper we present a fiber Bragg grating shift demodulator with changeable resolution based on an unbalanced fiber Mach-Zehnder interferometer. Preliminary research proves phase sensitivity to Bragg wavelength changes of 6,83 rad/mɛ. Phase sensitivity can be modified by changing the optical path difference witch is only limited by the coherence length of light reflected by the fiber Bragg grating. This solution can be used as a single sensor or as a part of a more complex system.

  2. 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.

  3. 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)...

  4. 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...

  5. 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.

  6. 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.

  7. Holographic gratings with NOA65® adhesives with edible colorant

    NASA Astrophysics Data System (ADS)

    Olivares-Pérez, A.; Fuentes-Tapia, I.; Toxqui-López, S.

    2015-03-01

    We present the preliminary results of diffraction gratings, which are made by holographic techniques with NOA65 adhesive as polymer matrix and neon purple food colors photosensitized. Gratings are recorded by diode laser ( λ = 445nm), the resulting intensity vs. exposure time curves are shown. The recorded gratings have a mixed behavior the face and the amplitude and itself-developing.

  8. [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.

  9. 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.

  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. Theory of optimal beam splitting by phase gratings. I. One-dimensional gratings.

    PubMed

    Romero, Louis A; Dickey, Fred M

    2007-08-01

    We give an analytical basis for the theory of optimal beam splitting by one-dimensional gratings. In particular, we use methods from the calculus of variations to derive analytical expressions for the optimal phase function.

  13. Echelle spectra of SN2014J from the Apache Point Observatory 3.5m telescope, UT January 27 and January 30, 2014

    NASA Astrophysics Data System (ADS)

    Ritchey, Adam M.; Welty, Daniel E.; Dahlstrom, Julie A.; York, Donald G.

    2014-02-01

    Optical spectra of SN2014J were recorded with the ARC echelle spectrograph at Apache Point Observatory, at approximately UT Jan. 27.2 (7 spectra, 8400 s) and UT Jan. 30.4, (6 spectra, 7200s), through thin clouds in seeing averaging 1.0 arcsec. The resolving power is 31,500. Useful interstellar spectra were obtained from 3850A to 9000A; estimated S/N values (photon counts only) near 6563A are 500 on Jan 27 and 400 on Jan 30, and about 1/3 those values at Ca II 3933A.

  14. 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.

  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. 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.

  17. 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.

  18. Fast thermal regeneration of fiber Bragg gratings.

    PubMed

    Bueno, Antonio; Kinet, Damien; Mégret, Patrice; Caucheteur, Christophe

    2013-10-15

    In this Letter we report a fast thermal regeneration of Type I fiber Bragg gratings inscribed with a UV laser in up to four different optical fibers: hydrogenated standard fiber, hydrogenated highly Ge-doped fiber, hydrogenated photosensitive fiber, and nonhydrogenated fiber. The thermal treatment consists in directly introducing the optical fiber into a preheated oven. The preheat temperature depends on the type of fiber used and is high enough to erase the grating and regenerate it afterward. The best results are obtained with hydrogenated photosensitive fiber and highly Ge-doped fiber, whereas no satisfactory results were obtained with hydrogenated standard fiber and nonhydrogenated photosensitive fiber. A regenerated grating with only 1.6 dB of loss was obtained in 10 min, reducing the time needed by a factor of 5.7. By adjusting the temperature of the oven, regenerated gratings of 13.7 dB of loss in 31 s and 5.8 dB of loss in 3 min were obtained. The factors of improvement in time are 110.3 and 19, respectively.

  19. Hybrid grating reflectors: Origin of ultrabroad stopband

    SciTech Connect

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

    2016-04-04

    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.

  20. 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…

  1. 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.

  2. 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…

  3. Fiber Bragg Grating Filter High Temperature Sensors

    NASA Technical Reports Server (NTRS)

    Lyons, Donald R.; Brass, Eric D.; Pencil, Eric (Technical Monitor)

    2001-01-01

    We present a scaled-down method for determining high temperatures using fiber-based Bragg gratings. Bragg gratings are distributed along the length of the optical fiber, and have high reflectivities whenever the optical wavelength is twice the grating spacing. These spatially distinct Bragg regions (located in the core of a fiber) are sensitive to local temperature changes. Since these fibers are silica-based they are easily affected by localized changes in temperature, which results in changes to both the grating spacing and the wavelength reflectivity. We exploit the shift in wavelength reflectivity to measure the change in the local temperature. Note that the Bragg region (sensing area) is some distance away from where the temperature is being measured. This is done so that we can measure temperatures that are much higher than the damage threshold of the fiber. We do this by affixing the fiber with the Bragg sensor to a material with a well-known coefficient of thermal expansion, and model the heat gradient from the region of interest to the actual sensor. The research described in this paper will culminate in a working device as well as be the second portion of a publication pending submission to Optics Letters.

  4. Reliable spectrometric fiber Bragg grating peak detection

    NASA Astrophysics Data System (ADS)

    Magalhães, Filipe; Martins, Paulo; Ferreira, Luís. A.; Araújo, Francisco M.

    2015-09-01

    A method for reliable fiber Bragg grating peak detection compatible with spectrometric demodulation schemes is presented. High immunity to differential losses and independency on the threshold settings was achieved. The effectiveness of the demonstrated method was corroborated by a 3σ accuracy of 2pm determined over 109 samples of 100 resonant peaks multiplexed in [1500; 1600] nm spectral range acquired throughout a year.

  5. Extraordinary optical extinctions through dual metallic gratings.

    PubMed

    Tardieu, Clément; Estruch, Thomas; Vincent, Grégory; Jaeck, Julien; Bardou, Nathalie; Collin, Stéphane; Haïdar, Riad

    2015-02-15

    We report on multiple extraordinary optical extinction (EOE) phenomena achieved through encapsulated dual metallic gratings. They are evidenced in TM polarization by angularly and spectrally resolved transmission measurements in the mid-infrared wavelength range. We show that EOE can be achieved on both sides of the extraordinary optical transmission (EOT) resonance, leading to pass-band filters with an improved rejection rate.

  6. 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.

  7. Parameter-tolerant design of high contrast gratings

    NASA Astrophysics Data System (ADS)

    Chevallier, Christyves; Fressengeas, Nicolas; Jacquet, Joel; Almuneau, Guilhem; Laaroussi, Youness; Gauthier-Lafaye, Olivier; Cerutti, Laurent; Genty, Frédéric

    2015-02-01

    This work is devoted to the design of high contrast grating mirrors taking into account the technological constraints and tolerance of fabrication. First, a global optimization algorithm has been combined to a numerical analysis of grating structures (RCWA) to automatically design HCG mirrors. Then, the tolerances of the grating dimensions have been precisely studied to develop a robust optimization algorithm with which high contrast gratings, exhibiting not only a high efficiency but also large tolerance values, could be designed. Finally, several structures integrating previously designed HCGs has been simulated to validate and illustrate the interest of such gratings.

  8. 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.

  9. 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.

  10. 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

  11. Optical position encoder based on four-section diffraction grating

    NASA Astrophysics Data System (ADS)

    Zherdev, A. Y.; Odinokov, S. B.; Lushnikov, D. S.; Markin, V. V.; Gurylev, O. A.; Shishova, M. V.

    2017-05-01

    Optical position encoder consists of movable coding grating and fixed analyzing grating. Light passing and diffracting through these two gratings creates interference signal on optical detector. Decoding of interference signal phase allows to determinate current position. Known optical position encoders use several accurate adjusted optical channels and detectors to gather several signals with different phase for higher encoder accuracy. We propose to use one optical channel with several-section analyzing diffraction grating for this purpose to simplify optical scheme and adjusting requirements. Optical scheme of position encoder based on four-section analyzing diffraction grating is developed and described in this paper.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Fabrication, measurement, and analysis of multilayer x- ray diffraction gratings

    NASA Astrophysics Data System (ADS)

    Hansen, Douglas P.

    1997-12-01

    I examine the theory and fabrication of lamellar multilayer x-ray diffraction gratings. I use current theory based on the Kirchoff Integral for amplitude gratings and a new equation for phase gratings to analyze current technology multilayer grating performance (where the period/λ exceeds 10). I examine the possible fabrication methods and define two general categories (additive: multilayer added to patterned substrate, subtractive: grating etched into multilayer). I conclude the additive approach is superior, leading to x-ray analogues to binary optics and holographic optical elements. I define an additive process in detail and demonstrate the serviceability of the key processes: thermal growth of silicon dioxide on silicon, lithography, a combined plasma-etch and wet-etch. Multilayer fabrication difficulties on patterned substrates are identified, including: mushroom cap growth, and filleting in the grooves. Measurements done at NSLS on 2 amplitude gratings and 1 phase grating are reported. The data is shown to be compatible with the Kirchoff theory.

  3. 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.

  4. 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.

  5. Use of Dual-Grating Sensors Formed by Different Types of Fiber Bragg Gratings for Simultaneous Temperature and Strain Measurements

    NASA Astrophysics Data System (ADS)

    Shu, Xuewen; Zhao, Donghui; Zhang, Lin; Bennion, Ian

    2004-04-01

    We report on a systematic investigation of the dependence of both temperature and strain sensitivities on the fiber Bragg grating type, including the well-known Type I, Type IIA, and a new type that we have designated Type IA, using both hydrogen-free and hydrogenated B/Ge codoped fibres. We have identified distinct sensitivity characteristics for each grating type, and we have used them to implement a novel dual-grating, dual-parameter sensor device. Three dual-grating sensing schemes with different combinations of grating type have been constructed and compared, and that of a Type IA-Type IIA combination exhibits the best performance, which is also superior to that of previously reported grating-based structures. The characteristics of the measurement errors in such dual-grating sensor systems is also presented in detail.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Novel gratings for next-generation instruments of astronomical observations

    NASA Astrophysics Data System (ADS)

    Ebizuka, N.; Okamoto, T.; Takeda, M.; Hosobata, T.; Yamagata, Y.; Sasaki, M.; Uomoto, M.; Shimatsu, T.; Sato, S.; Hashimoto, N.; Tanaka, I.; Hattori, T.; Ozaki, S.; Aoki, W.

    2017-05-01

    We will introduce current status of development of a birefringence volume phase holographic (B-VPH) grating, volume binary (VB) grating and reflector facet transmission (RFT) grating developing as the novel dispersive optical element for astronomical instruments for the 8.2m Subaru Telescope, for next generation 30 m class huge ground-based telescopes and for next generation large space-bone telescopes. We will also introduce a hybrid grism developed for MOIRCS (Multi-Object InfraRed Camera and Spectrograph) of the Subaru Telescope and a quasi-Bragg (QB) immersion grating. Test fabrication of B-VPH gratings with a liquid crystal (LC) of UV curable and normal LCs or a resin of visible light curable are performed. We successfully fabricated VB gratings of silicon as a mold with ridges of a high aspect ratio by means of the cycle etching process, oxidation and removal of silicon oxide. The RFT grating which is a surface-relief (SR) transmission grating with sawtooth shaped ridges of an acute vertex angle. The hybrid grism, as a prototype of the RFT grating, combines a high-index prism and SR transmission grating with sawtooth shape ridges of an acute vertex angle. The mold of the SR grating for the hybrid grism on to a work of Ni-P alloy of non-electrolysic plating successfully fabricated by using our ultra-precision machine and a single-crystal diamond bite. The QB immersion grating was fabricated by a combination of an inclined QB grating, Littrow prism and surface reflection mirror.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Transmission Grating Spectrometers in Undergraduate Astronomy Laboratories

    NASA Astrophysics Data System (ADS)

    Hood, Ryan; Moore, J.; McKinlay, M.; Coffin, D.; Trieweiler, D.; Mutel, R. L.

    2012-01-01

    The Iowa Robotic Telescope, located in southern Arizona, has been used in University of Iowa undergraduate laboratories for more than a decade. The addition of a low-resolution transmission grating spectrometer (TGS) to the 0.37 m classical Cassegrain reflector has allowed students to obtain spectra of stars, planets, and nebulae as regular part of the lab curriculum. We discuss the relative efficiency and resolution dependences using different groove spacings, slits, telescope optics, and camera sensor geometries. In addition, we consider the use of beam steering prisms joined with diffraction gratings (grisms). Students may schedule the TGS system using a simple web-based form to observe targets down to approximately 10th magnitude. Some of the TGS observational targets include Wolf-Rayet stars with optically thick winds, novae, as well as main sequence stars over the entire spectral sequence.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. High-end spectroscopic diffraction gratings: design and manufacturing

    NASA Astrophysics Data System (ADS)

    Glaser, Tilman

    2015-02-01

    Diffraction gratings are key components for spectroscopic systems. For high-end applications, they have to meet advanced requirements as, e.g., maximum efficiency, lowest possible scattered light level, high numerical aperture, and minimal aberrations. Diffraction gratings are demanded to allow spectrometer designs with highest resolution, a maximal étendue, and minimal stray light, built within a minimal volume. This tutorial is intended to provide an overview of different high-end spectroscopic gratings, their theoretical design and manufacturing technologies.

  16. 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.

  17. Imaging Spectrometer Designs Utilizing Immersed Gratings With Accessible Entrance Slit

    DOEpatents

    Chrisp, Michael P.; Lerner, Scott A.

    2006-03-21

    A compact imaging spectrometer comprises an entrance slit, a catadioptric lens with a mirrored surface, a grating, and a detector array. The entrance slit directs light to the mirrored surface of the catadioptric lens; the mirrored surface reflects the light back through the lens to the grating. The grating receives the light from the catadioptric lens and diffracts the light to the lens away from the mirrored surface. The lens transmits the light and focuses it onto the detector array.

  18. 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.

  19. Tunable phase-shifted fiber Bragg grating based on femtosecond laser fabricated in-grating bubble.

    PubMed

    Liao, Changrui; Xu, Lei; Wang, Chao; Wang, D N; Wang, Yiping; Wang, Qiao; Yang, Kaiming; Li, Zhengyong; Zhong, Xiaoyong; Zhou, Jiangtao; Liu, Yingjie

    2013-11-01

    We present a type of phase-shifted fiber Bragg gratings based on an in-grating bubble fabricated by femtosecond (fs) laser ablation together with a fusion-splicing technique. A microchannel vertically crossing the bubble is drilled by fs laser to allow liquid to flow in or out. By filling different refractive index (RI) liquid into the bubble, the phase-shift peak is found to experience a linear red shift with the increase of RI, while little contribution to the change of phase shift comes from the temperature and axial strain. Therefore, such a PS-FBG could be used to develop a promising tunable optical filter and sensor.

  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. A modal analysis of lamellar diffraction gratings in conical mountings

    NASA Technical Reports Server (NTRS)

    Li, Lifeng

    1992-01-01

    A rigorous modal analysis of lamellar grating, i.e., gratings having rectangular grooves, in conical mountings is presented. It is an extension of the analysis of Botten et al. which considered non-conical mountings. A key step in the extension is a decomposition of the electromagnetic field in the grating region into two orthogonal components. A computer program implementing this extended modal analysis is capable of dealing with plane wave diffraction by dielectric and metallic gratings with deep grooves, at arbitrary angles of incidence, and having arbitrary incident polarizations. Some numerical examples are included.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Ultrasonic hydrophone based on short in-fiber bragg gratings.

    PubMed

    Fisher, N E; Webb, D J; Pannell, C N; Jackson, D A; Gavrilov, L R; Hand, J W; Zhang, L; Bennion, I

    1998-12-01

    We investigate the feasibility of using in-fiber Bragg gratings for measuring acoustic fields in the megahertz range. We found that the acoustic coupling from the ultrasonic field to the grating leads to the formation of standing waves in the fiber. Because of these standing waves, the system response is complex and, as we show, the grating does not act as an effective probe. However, significant improvement in its performance can be gained by use of short gratings coupled with an appropriate desensitization of the fiber. A noise-limited pressure resolution of approximately 4.5 x 10(-3) atm/ radicalHz was found.

  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. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Grating coupler on single-crystal lithium niobate thin film

    NASA Astrophysics Data System (ADS)

    Chen, Zhihua; Wang, Yiwen; Jiang, Yunpeng; Kong, Ruirui; Hu, Hui

    2017-10-01

    The grating coupler on single-crystal lithium niobate thin film (lithium niobate on insulator, LNOI) was designed. A bottom reflector was added in the LNOI material to improve the coupling efficiency. The grating structure was optimized by FDTD method. The material parameters such as layer thickness of lithium niobate thin film, SiO2 thickness were discussed with respect to the coupling efficiency, and the tolerances of grating period, etch depth, groove width and fiber position were also studied systematically. The simulated maximum coupling efficiency from a grating coupler with (without) bottom reflector to a single-mode fiber is about 78% (40%) in z-cut LNOI for TE polarization.

  13. 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.

  14. Gratings for Increasing Solid-State Laser Gain and Efficiency

    SciTech Connect

    Erlandson, A C; Britten, J A; Bonlie, J D

    2010-04-16

    We introduce new concepts for increasing the efficiency of solid state lasers by using gratings deposited on laser slabs or disks. The gratings improve efficiency in two ways: (1) by coupling out of the slab deleterious amplified spontaneous emission (ASE) and (2) by increasing the absorption efficiency of pump light. The gratings also serve as antireflective coatings for the extracting laser beam. To evaluate the potential for such coatings to improve laser performance, we calculated optical properties of a 2500 groove/mm, tantala-silica grating on a 1cm x 4cm x 8cm titanium-doped sapphire slab and performed ray-trace calculations for ASE and pump light. Our calculations show substantial improvements in efficiency due to grating ASE-coupling properties. For example, the gratings reduce pump energy required to produce a 0.6/cm gain coefficient by 9%, 20% and 35% for pump pulse durations of 0.5 {micro}s, 1{micro}s and 3{micro}s, respectively. Gratings also increase 532-nm pump-light absorption efficiency, particularly when the product slab overall absorption is small. For example, when the single-pass absorption is 1 neper, absorption efficiency increases from 66%, without gratings, to 86%, when gratings are used.

  15. Nanoimprint of gratings on a bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Chu, J. P.; Wijaya, H.; Wu, C. W.; Tsai, T. R.; Wei, C. S.; Nieh, T. G.; Wadsworth, Jeffrey

    2007-01-01

    The authors demonstrate that optical gratings with 600 and 1500nm periods on a Pd40Ni40P20 bulk metallic glass (BMG) can be faithfully imprinted in air from Si dies. Results of scanning electron microscopy, atomic force microscopy, and optical diffraction analysis show the fine line feature of ˜150nm. The gratings have smooth and uniform surface profiles with comparable optical properties as the original Si dies. The BMG gratings can be further used to imprint the second-generation replicas on polymethylmethacrylate. Thereby, BMG is a suitable material not only for imprinting nanostructured parts such as gratings, but also as a good die material for nanoimprints.

  16. 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).

  17. The characteristics of fiber slanted gratings in multimode fiber

    NASA Astrophysics Data System (ADS)

    Yang, Xiufeng; Zhao, Chunliu; Zhou, Junqiang; Guo, Xin; Ng, Junhong; Zhou, Xiaoqun; Lu, Chao

    2004-01-01

    We report what is believed to the first example of graded index multimode fiber slanted grating. The gratings are realized by the same technique as the single mode fiber gratings. The periodic perturbation causes fundamental core mode to higher order core modes, cladding modes and radiation modes coupling. There is a unique feature in the spectra of certain angle-slanted gratings (2.5°-4°). Hope this phenomenon can cause a new type of fiber components that can be widely used in the LAN and sensing systems.

  18. Spherical grating based x-ray Talbot interferometry

    PubMed Central

    Cong, Wenxiang; Xi, Yan; Wang, Ge

    2015-01-01

    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

  19. Aberration corrected aspheric grating for far ultraviolet spectrographs - Conventional approach

    NASA Technical Reports Server (NTRS)

    Content, David; Trout, Catherine; Davila, Pam; Wilson, Mark

    1991-01-01

    Two approaches to reducing optical aberrations of concave grating spectrographs have been used, holographically controlling the groove curvature and spacing and reshaping the optical substrate while ruling the grooves conventionally. The latter approach, slightly deforming an ellipsoidal grating blank, can lead to diffraction-limited performance at a single FUV wavelength. When such a grating is used in a slitted Rowland circle spectrograph, the result is an extremely efficient spectrograph with spectral resolving power of about 30,000 and low astigmatism. Optical fabrication technology has advanced to the point where these exotic surface gratings are becoming practical.

  20. Modeling spatially localized photonic nanojets from phase diffraction gratings

    SciTech Connect

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

    2016-04-21

    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.

  1. 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.

  2. 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.

  3. 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.

  4. Measurement of atomic diffraction phases induced by material gratings

    SciTech Connect

    Perreault, John D.; Cronin, Alexander D.

    2006-03-15

    Atom-surface interactions can significantly modify the intensity and phase of atom de Broglie waves diffracted by a silicon nitride grating. This affects the operation of a material grating as a coherent beam splitter. The phase shifts induced by diffraction are measured by comparing the relative phases of several interfering paths in a Mach-Zehnder Na atom interferometer formed by three material gratings. The values of the diffraction phases are consistent with a simple model which includes a van der Waals atom-surface interaction between the Na atoms and the silicon nitride grating bars.

  5. 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.

  6. 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.

  7. 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.

  8. The GMT-Consortium Large Earth Finder (G-CLEF) : An Optical Echelle Spectrograph for the Giant Magellan Telescope (GMT) with Multi-Object Spectroscopy (MOS) Capability

    NASA Astrophysics Data System (ADS)

    Szentgyorgyi, Andrew

    2017-09-01

    "The GMT-Consortium Large Earth Finder (G-CLEF) is an optical band echelle spectrograph that has been selected as the first light instrument for the Giant Magellan Telescope (GMT). G-CLEF is a general purpose, high dispersion instrument that is fiber fed and capable of extremely precise radial velocity (PRV) measurements. G-CLEF will have a novel multi-object spectroscopy (MOS) capability that will be useful for a number of exoplanet science programs. I describe the general properties of G-CLEF and the systems engineering analyses, especially for PRV, that drove the current G-CLEF design. The requirements for calibration of the MOS channel are presented along with several novel approaches for achieving moderate radial velocity precision in the MOS mode."

  9. 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; di Marcantonio, Paolo; 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Influence of grating characteristics on the operation of circular-grating distributed-feedback polymer lasers

    NASA Astrophysics Data System (ADS)

    Turnbull, G. A.; Carleton, A.; Barlow, G. F.; Tahraouhi, A.; Krauss, T. F.; Shore, K. A.; Samuel, I. D. W.

    2005-07-01

    We explore the influence of grating characteristics on the lasing performance of polymer circular-grating distributed-feedback lasers. A range of circular-grating sizes and profiles were fabricated on a single silica substrate, which was coated with a thin film of the conjugated polymer poly[2-methoxy-5-(2'ethylhexyloxy)-1,4-phenylene vinylene]. Variations in lasing threshold and surface-emitted slope efficiency were determined as a function of grating outer diameter and duty cycle. The experimental lasing results are compared with predictions from a theoretical analysis based on an adaptation of the transfer matrix method. We find that an outer diameter of at least 200μm is required to minimize the threshold and optimize the surface-emitted slope efficiency. A groove-to-period duty cycle of ˜25% gives the lowest lasing thresholds by optimizing the in-plane feedback. We also find that the structure of the polymer-air surface varies substantially with substrate duty cycle, which has implications for optimum device design.

  16. 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

  17. A Catalog of Chandra Grating Spectra

    NASA Astrophysics Data System (ADS)

    Huenemoerder, David; Nichols, J.; Mitschang, A.; Dewey, D.; Marshall, H.; Nowak, M.; Schulz, N.; Davis, J. E.; Houck, J. C.; Canizares, C.

    2008-03-01

    We are developing a Chandra Grating-Data Archive and Catalog to make all grating spectra more visible and accessible to users. We intend to to provide a simple browser interface to analysis-quality standard spectral products (binned spectra and corresponding response files), with the addition of summary graphical products and model-independent flux properties tables. Such products and a browser interface will make it easy for a user to find observations of a particular object, type of object, or type of observation, to quickly assess the quality and potential usefulness of the spectra, and to download the data and responses as a package if desired. We will include LETG data as well as ACIS CC-mode observations. In addition to the data, portable reprocessing scripts, using CXC and other publicly available software which were used to create the archive will also be available to users, facilitating standard or customized reprocessing from download of Level 1 archive data to production of spectra and responses with minimal interaction (analogous to the "psextract" script commonly used for automated imaging spectral extraction). We will add some customized products which may take time, effort, or special expertise to produce. Candidates for such include extended source extractions, crowded field extractions, and aggregate products such as summed Capella or summed Orion-field-objects spectra. Additional content will grow according to user feedback. This catalog builds upon experience with other relevant work, such as the X-Atlas of HETGS spectra (http://cxc.harvard.edu/XATLAS) or the XMM-RGS spectral browser (http://xmm.esac.esa.int/BiRD). It is intended to be a long-term legacy product for Chandra gratings observations. This work was supported by NASA through the Smithsonian Astrophysical Observatory (SAO) contract SV3-73016 for the Chandra X-Ray Center and Science Instruments.

  18. Streaked, x-ray-transmission-grating spectrometer

    SciTech Connect

    Ceglio, N.M.; Roth, M.; Hawryluk, A.M.

    1981-08-01

    A free standing x-ray transmission grating has been coupled with a soft x-ray streak camera to produce a time resolved x-ray spectrometer. The instrument has a temporal resolution of approx. 20 psec, is capable of covering a broad spectral range, 2 to 120 A, has high sensitivity, and is simple to use requiring no complex alignment procedure. In recent laser fusion experiments the spectrometer successfully recorded time resolved spectra over the range 10 to 120 A with a spectral resolving power, lambda/..delta..lambda of 4 to 50, limited primarily by source size and collimation effects.

  19. Tunable air-suspended polymer grating couplers

    NASA Astrophysics Data System (ADS)

    Prokop, Christoph; Schmalz, Tobias; Kleessen, Philipp; Laegel, Bert; Wolff, Sandra; Mitchell, Arnan; Karnutsch, Christian

    2017-06-01

    We present thermal tuning of air-suspended SU-8 polymer waveguide grating couplers for TE-polarized light. Numerical simulations have been performed to estimate the wavelength shift caused by the change of temperature. Due to the small positive thermal expansion and large negative thermo-optic coefficient of SU-8, a shift toward shorter wavelengths is expected. In the experimental evaluation, a negative wavelength shift from 1542 nm at 20°C toward 1527 nm at 56°C is obtained with approximately -0.42 nm K-1 matching the theoretical considerations.

  20. Optical scales, reticles, gratings, masks, and standards.

    PubMed

    Horne, D F

    1981-12-01

    Photofabrication techniques using positive photoresists, developed for the quantity production of theodolite circular scales, have been adapted to making master chrome masks for photoetching moire fringe radial diffraction gratings. Diamond stylus wear, or chipping of the diamond tip, on a precision surface measuring instrument is difficult to detect and can cause incorrect surface texture measurements. A stylus wear standard was developed, and fabrication problems were solved by the anisotropic etching of a silicon slice using a chrome mask and photoresist. An essential feature of this process was precise orientation of the mask with a crystal cleavage plane. Experience gained suggests the means for quantitative quality control of diamond tools used for micromachining.

  1. 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.

  2. 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.

  3. 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.

  4. Gold strip gratings with binary supercell.

    PubMed

    Magno, Giovanni; Marrocco, Valeria; Grande, Marco; D'Orazio, Antonella

    2013-08-01

    In this Letter, the study of a periodic structure composed of gold strips arranged in double-period unit cells, in a symmetric and asymmetric environment, is reported. The spectral maps show that the formation of the plasmonic bandgap and the extraordinary optical transmission are subjected to the proportion between the strip widths. Moreover, when the asymmetric environment is considered, high-transmittance and high-absorbance states arise. Hence, by controlling the geometrical parameters of the binary-periodic structure, it is possible to tailor the spectral response of the grating enhancing the desired features and exploiting them for different applications.

  5. An infrared grating spectrometer for GIRL

    NASA Astrophysics Data System (ADS)

    Knieling, Peter; Lange, Guenther; Offermann, Dirk; Grossmann, Klaus-Ulrich

    1986-08-01

    A grating spectrometer with medium spectral resolution was developed for the GIRL project (Experiment E3), for the determination of the emission of trace constituents in the Earth's atmosphere, and for planetary and astronomical measurements. The spectrometer consists of two Ebert-Fastie spectrometers covering the wavelength range between 2.5 and 100 micron. The engineering model of E3 is described, and the design data are given. The engineering model was verified during operation in a cryostat at liquid helium temperatures. The spectral channels and respective IR filters were designed. Stray light suppression during limb scan measurements is explained. Absorption and emission spectra of atmospheric trace gases were measured.

  6. 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.

  7. 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.

  8. 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.

  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. 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.

  11. Two-Period Gratings For Surface-Emitting Lasers

    NASA Technical Reports Server (NTRS)

    Lang, Robert J.

    1991-01-01

    Grating surfaces having two spatial periods tailored to obtain desired proportions of output coupling and inward reflection. Solid-state lasers of type emitting light perpendicularly to their broad surfaces made more efficient. Same principle also applicable to "Annular-Bragg-Grating Surface-Emitting Laser", (NPO-17912).

  12. 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.

  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. 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.

  15. 21 CFR 133.148 - Hard grating cheeses.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 2 2011-04-01 2011-04-01 false Hard grating cheeses. 133.148 Section 133.148 Food... HUMAN CONSUMPTION CHEESES AND RELATED CHEESE PRODUCTS Requirements for Specific Standardized Cheese and Related Products § 133.148 Hard grating cheeses. (a) The cheeses for which definitions and standards of...

  16. Imaging with classical spherical diffraction gratings: the quadrature configuration.

    PubMed

    Prieto-Blanco, Xesús; Montero-Orille, Carlos; González-Núñez, Héctor; Dolores Mouriz, María; López Lago, Elena; de la Fuente, Raúl

    2009-11-01

    We review the theory of spherical diffraction gratings with regard to their imaging properties in off-plane arrangements. Our study is restricted to gratings with equally spaced grooves, and it is focused on the quadrature configuration, where the incident and diffraction planes are orthogonal to each other. We identify regions of low astigmatism and propose some monochromator mounts.

  17. Transmission gratings for beam sampling and beam splitting.

    PubMed

    Popov, E K; Loewen, E G; Neviére, M

    1996-06-01

    Transmission gratings have rarely been used for beam sampling because they require special properties from dielectric overcoatings, which, to the best of our knowledge, are described here for the first time. Although such gratings are often used as beam splitters, their nature can be modified along the same principles with thin metal coatings, which are described.

  18. Grating Fabrication for Gravitational-Wave Interferometers and LISA GRS

    NASA Astrophysics Data System (ADS)

    Lu, Patrick; Sun, Ke-Xun; Byer, Robert L.

    2006-11-01

    Future LISA and LIGO projects may require gratings for interferometry and angular sensing to accurately monitor test mass positions. This paper summarizes some techniques used to create gratings on materials that will make up the test masses of next generation gravitational-wave detectors. As grating tip/tilt sensing will require two-dimensional grating structures with duty cycles and unit cell shapes that are as of yet undetermined, we concentrate on approaches that allow us to readily generate complex patterns. This paper discusses e-beam lithography for dielectric surfaces, and mechanical trans-imprinting and focused ion-beam writing for gold. These methods are more flexible than traditional techniques, such as the holographic exposure of photoresist with multiple laser beams. Grating patterns suitable for optical sensing have been successfully demonstrated on the surfaces of dielectric materials and gold. Their diffraction efficiencies have been measured to be sufficiently high for tip/tilt sensing.

  19. 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.

  20. 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.

  1. 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.

  2. Gratings in nonlinear optical polymers for integrated optical device applications

    NASA Astrophysics Data System (ADS)

    Kardinahl, Thiemo; Franke, Hilmar

    1993-12-01

    The polymer poly(methyl methacrylate) (PMMA) doped with the active photoinitiator dimethoxyphenalacetophenon (DMPA) is a well known material to form permanent gratings by uv-holographie. An additional doping with the photochromic material E-(alpha) (2,5- dimethyl-3-furyl)ethylidene(adamantylidene)succinic anhydride (Aberchrome 670) leads to a one step fabrication of a nonlinear optical grating. After the permanent grating is fixed, the refractive index of the grating can be tuned by a homogenous illumination. The diffraction efficiency of the grating can be tuned because the fulgide Aberchrome 670 undergoes a reversible transition from its bleached to its colored form by homogeneous uv illumination and back again by irradiating the film with a wavelength near the absorption maximum (here (lambda) equals 514.5 nm).

  3. 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.}

  4. 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.

  5. Holographic surface gratings in iron-doped lithium niobate

    SciTech Connect

    Sarkisov, S. S.; Curley, M. J.; Kukhtarev, N. V.; Fields, A.; Adamovsky, G.; Smith, C. C.; Moore, L. E.

    2001-08-13

    Surface gratings associated with holographic volume gratings in photorefractive crystals of iron-doped lithium niobate have been studied using diffraction of a reflected probe beam and high-resolution phase-shifted interferometric profilometry. Both techniques show that the surface gratings exist in the form of periodical corrugations of the same period as that of the volume grating. The maximum amplitude of the periodical surface relief measured by both techniques is close to 6.5 nm. We also demonstrated that the periodical electric forces on the surface were capable of assembling polystyrene microspheres along the fringes of the grating. Large amplitude of the periodic electric field (1.6 x 10{sup 4}V/cm) is associated with the photogalvanic effect. {copyright} 2001 American Institute of Physics.

  6. 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.

  7. 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).

  8. Electro-optically tunable diffraction grating with photoaligned liquid crystals

    NASA Astrophysics Data System (ADS)

    Węgłowski, Rafał; Kozanecka-Szmigiel, Anna; Piecek, Wiktor; Konieczkowska, Jolanta; Schab-Balcerzak, Ewa

    2017-10-01

    This work shows the possibility of fabricating one- and two-dimensional diffraction structures based on liquid crystals photoaligned with the layers of photosensitive azobenzene poly(ester imide). The gratings involve a micron-sized planar-twisted nematic alignment. The diffraction efficiency of these gratings is controlled by a uniform electric field applied across the cell. The electro-optical measurements showed short switching times (0.8 ms and 7 ms for τrise and τdecay respectively) and low driving electric fields (1 . 5 V / μm) of 1st order diffracted light. The LC grating is regarded as an amplitude grating in the low electric field region and a phase grating in the high electric field region. Moreover the diffraction efficiency is polarization-independent in the wide range of external electric fields.

  9. Electromagnetically Induced Grating Without Absorption Using Incoherent Pump

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

    We propose a scheme for creating electromagnetically induced grating in a four-level double- Λ atomic system driven by a coupling field and an incoherent pump field. Owing to the incoherent pumping process, large refractivity accompanied with vanishing absorption or even gain across the probe field can be built up in the atoms, thus phase grating or gain-phase grating, which diffracts a probe light into different directions, can be formed with the help of a standing-wave coupling field. The diffraction efficiency of the gratings can be tuned by the coupling field intensity and the incoherent pump rate, hence the proposed gratings should be suitable for beam splitter and optical switching in optical communication and networking.

  10. Polarization of holographic grating diffraction. I. General theory

    NASA Astrophysics Data System (ADS)

    Nee, Tsu-Wei; Nee, Soe-Mie F.

    2004-04-01

    The full polarization property of volume holographic grating diffraction is investigated theoretically. With a simple volume grating model, the diffracted fields and Mueller matrices are first derived from Maxwell's equations by using the Green's function algorithms. The formalism is derived for the general case that the diffraction beam and the grating wave vector are not in the plane of incidence, where s waves and p waves are not decoupled. The derived photon-momentum relations determine the Bragg angle selectivity. The parameters of diffraction strength related to the hologram-writing process and material are defined and are not necessarily small in general. The diffracted-beam profiles are analytically calculated by using the known grating shape function. This theory has provided a fundamental understanding of the polarization phenomena of a real holographic diffraction grating device. The derived algorithm would provide a simulation-analysis tool for the engineering design of real holographic beam combiner/splitter devices.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Design of a multiplexing grating for color holographic waveguide

    NASA Astrophysics Data System (ADS)

    Guo, Jingjing; Tu, Yan; Yang, Lanlan; Wang, Lili; Wang, Baoping

    2015-12-01

    Volume holographic gratings have been used in waveguide displays to implement full-color three-dimensional imaging. Among these, multiplexing gratings are advanced in low energy losses and simple manufacture technologies when used as couplers of color hologram waveguides. A multiplexing holographic grating is designed to realize a uniform red, green, and blue diffraction efficiency and eliminate stray light to the largest extent. Results indicate that the red, green, and blue light incident normal to the grating could be successfully in-coupled into the planar waveguide for total internal reflection with high peak diffraction efficiency, similar energy output, and little stray light. We also analyze the effect of the technical tolerance, including gating thickness, index modulation, grating period, slanted angle, and incident angle. This analysis could help to minimize the optical system and improve the color image quality of waveguide displays.

  16. Multilayer Dielectric Gratings for Petawatt-Class Laser Systems

    SciTech Connect

    Britten, J A; Molander, W; Komashko, A M; Barty, C P J

    2003-12-03

    Existing Petawatt class lasers today based on Nd:glass architectures operating at nominally 500 J, 0.5 ps use meter-scale aperture, gold-overcoated master photoresist gratings to compress the amplified chirped pulse. Many lasers operating in the >lkJ, >Ips regime are in the planning stages around the world. These will require multilayer dielectric diffraction gratings to handle larger peak powers than can be accommodated with gold gratings. Models of the electric field distribution in the solid material of these gratings suggest that high aspect-ratio structures used at high incidence angles will have better laser damage resistance. New tooling for transfer etching these submicron-grating patterns and for nondestructive critical-dimension measurement of these features on meter-scale substrates will be described.

  17. 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.

  18. 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.

  19. 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.

  20. Electromagnetically Induced Grating Without Absorption Using Incoherent Pump

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

    We propose a scheme for creating electromagnetically induced grating in a four-level double- Λ atomic system driven by a coupling field and an incoherent pump field. Owing to the incoherent pumping process, large refractivity accompanied with vanishing absorption or even gain across the probe field can be built up in the atoms, thus phase grating or gain-phase grating, which diffracts a probe light into different directions, can be formed with the help of a standing-wave coupling field. The diffraction efficiency of the gratings can be tuned by the coupling field intensity and the incoherent pump rate, hence the proposed gratings should be suitable for beam splitter and optical switching in optical communication and networking.

  1. 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)

  2. 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.

  3. Chirped fiber Bragg grating detonation velocity sensing.

    PubMed

    Rodriguez, G; Sandberg, R L; McCulloch, Q; Jackson, S I; Vincent, S W; Udd, E

    2013-01-01

    An all optical-fiber-based approach to measuring high explosive detonation front position and velocity is described. By measuring total light return using an incoherent light source reflected from a linearly chirped fiber Bragg grating sensor in contact with the explosive, dynamic mapping of the detonation front position and velocity versus time is obtained. We demonstrate two calibration procedures and provide several examples of detonation front measurements: PBX 9502 cylindrical rate stick, radial detonation front in PBX 9501, and PBX 9501 detonation along curved meridian line. In the cylindrical rate stick measurement, excellent agreement with complementary diagnostics (electrical pins and streak camera imaging) is achieved, demonstrating accuracy in the detonation front velocity to below the 0.3% level when compared to the results from the pin data. Finally, an estimate on the linear spatial and temporal resolution of the system shows that sub-mm and sub-μs levels are attainable with proper consideration of the recording speed, detection sensitivity, spectrum, and chirp properties of the grating.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Cooled grating infrared spectrometer for astronomical observations

    NASA Technical Reports Server (NTRS)

    Houck, J. R.; Gull, G. E.

    1983-01-01

    A liquid helium-cooled infrared spectrometer for the 16 to 50 micron range is described. The instrument has six detectors, three each of Si:Sb and Ge:Ga and two diffraction gratings mounted back-to-back. Cold preoptics are used to match the spectrometer to the telescope. In its nominal configuration the system resolution is 0.03 micron from 16 to 30 microns and 0.07 micron from 28 to 50 microns. A cooled filter wheel is used to change order sorting filters. The gratings are driven by a steel band and gear train operating at 4 K. The detector outputs are amplified by a TIA, employing a matched pair of JFETs operating at 70 K inside the dewar. The external warm electronics include a gain stage for the TIA and dc-coupled gating circuit to remove charged-particle (cosmic-ray secondary)-induced noise spikes. The gating circuit reduces the overall system noise by a factor of two when the spectrometer is used on NASA's Kuiper Airborne Observatory. Sample spectra are presented and the deglitcher performance is illustrated.

  10. 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.

  11. The Interaction of Optical Guided Modes with Waveguide Diffraction Gratings.

    NASA Astrophysics Data System (ADS)

    Weller-Brophy, Laura Ann

    In this thesis the results of a theoretical and experimental investigation of the coupling of guided modes by waveguide gratings are presented. This work is motivated by the potential application of waveguide gratings to integrated optical devices. The coupling of guided modes obliquely incident to both periodic and aperiodic gratings is a mechanism basic to the operation of integrated optical components such as filters, reflectors, beamsplitters, and modulators. It is shown in the Introduction to this thesis, that this mechanism is not modeled consistently by the analyses presented in the literature. For the case of TM-TM coupling, virtually each analytical treatment predicts a different value for the grating reflectivity. In addition, it is found that the typical Coupled-Mode formalisms used to derive the grating reflectivity do not offer an intuitive picture of the operation of waveguide gratings. These two particular problem areas serve as the focal points of this thesis. The latter of these is addressed through the development of a thin film model of the operation of waveguide gratings. This model presents an intuitively appealing picture of the interaction of waveguide gratings and guided modes. It also yields grating reflectivities which are in excellent agreement with those obtained through the numerical solution of the Coupled-Mode equations for both periodic and aperiodic gratings. The bulk of this research project is directed towards resolving the conflicting theoretical grating analyses presented in the literature. A new derivation of the coupling of guided modes obliquely incident to periodic gratings is presented in Chapter II of this thesis. This derivation is based on the Local Normal Mode expansion used by Marcuse for the case of normal incidence. It produces coupling coefficients which are nearly identical to those derived using the rigorous Boundary Perturbation technique. The coupling coefficients predicted by this Local Normal Mode formalism

  12. 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.

  13. Optical fiber Bragg gratings. Part I. Modeling of infinitely long gratings

    NASA Astrophysics Data System (ADS)

    Passaro, Vittorio M. N.; Diana, Roberto; Armenise, Mario N.

    2002-09-01

    We present an accurate numerical method based on the Floquet-Bloch formalism to analyze the propagation properties and the radiation loss in infinitely long uniform fiber Bragg gratings. The model allows us to find all the propagation characteristics including the propagation constants, the space harmonics and the total field distribution, the guided and radiated power, and the modal loss induced by the periodic structure. The influence of the geometrical and physical parameters on the performance of the Bragg gratings has been established. A clear explanation of the physical phenomena related to the index modulation amplitude changes is presented, including the photonic bandgap effect, which is not easily described by the finite-difference time-domain method and cannot be described by the widely used coupled-mode theory.

  14. Slow light in fiber Bragg gratings and its applications

    NASA Astrophysics Data System (ADS)

    Skolianos, George; Arora, Arushi; Bernier, Martin; Digonnet, Michel

    2016-11-01

    Slow-light fiber Bragg gratings (FBGs) belong to a class of gratings designed to exhibit one or more narrow resonances in their reflection and transmission spectra, produced either by introducing a π phase shift near the middle of the grating, or by increasing the index modulation so that the grating behaves like a Fabry-Perot interferometer. These resonances can have very narrow linewidths (<50 fm), resulting in low group velocities and high Q factors. Slow-light gratings are finding a growing number of applications in many areas of photonics, including nonlinear optics, optical switching, optical delay lines, and sensing. This paper reviews the principle of these gratings, in particular the more recent slow-light gratings relying on a strong index modulation. It discusses in particular the requirements for achieving large group delays and high sensitivities in sensors, and the fabrication and annealing techniques used to meet these requirements (high index modulation, low loss, index-profile apodization, and optimized length). Several applications are presented, including record-breaking FBGs that exhibit a group delay of 42 ns and Q-factor of ~30 million over a 12.5 mm length, robust acoustic sensors with pressure resolution of ~50 µPa (√Hz)-1 in the few-kHz, and a strain sensor capable of resolving as little as 30 femtostrain (√Hz)-1.

  15. Performance of high spatial frequency X-ray transmission gratings

    NASA Technical Reports Server (NTRS)

    Fischbach, K. F.; Levine, A. M.; Schattenburg, M. L.; Dewey, D.; Renshaw, R. L.

    1988-01-01

    The performance of high spatial frequency 'phased' X-ray transmission gratings developed for the High Energy Transmission Grating Spectrometer on the Advanced X-ray Astrophysics FAcility (AXAF) is examined. The gratings tested here nominally consist of 1-micron-thick gold lines of 0.2 micron period covering approximately 5 sq cm of a polyimide membrane. A table-top setup at MIT employs the gratings in reflection to diffract UV (325 nm) laser light. It is used to measure grating periods and indicates that period variations within and between gratings are a few parts in 10,000. Tests performed at the Marshall Space Flight Center 304 m X-ray Facility using 1.5 keV X-rays in transmission corroborate the UV measurements and demonstrate geometrically-limited resolving powers of E/Delta E about 750. Finally, X-ray transmission tests performed in the MIT 25 m X-ray facility provide measurements of period, line thickness, space-to-period ratio, tilt of grating lines, and efficiency.

  16. 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.

  17. 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.

  18. Characterization of the holographic imaging grating of GOMOS UVIS spectrometer

    NASA Astrophysics Data System (ADS)

    Graeffe, Jussi; Saari, Heikki K.; Astola, Heikki; Rainio, Kari; Mazuray, Lorand; Pierot, Dominique; Craen, Pierre; Gruslin, Michel; Lecat, Jean-Herve; Bonnemason, Francis; Flamand, Jean; Thevenon, Alain

    1996-11-01

    A Finnish-French group has proposed an imaging spectrometer- based instrument for the ENVISAT Earth observation satellite of ESA, which yields a global mapping of the vertical profile of ozone and other related atmospheric gases. The GOMOS instrument works by measuring the UV-visible spectrum of a star that is occulting behind the Earth's atmosphere. The prime contractor of GOMOS is Matra Marconi Space France. The focal plane optics are designed and manufactured by Spacebel Instrumentation S.A. and the holographic grating by Jobin-Yvon. VTT Automation, Measurement Technology has participated in the GOMOS studies since 1989 and is presently responsible for the verification tests of the imaging quality and opto-mechanical interfaces of the holographic imaging grating of GOMOS. The UVIS spectrometer of GOMOS consists of a holographic, aberration corrected grating and of a CCD detector. The alignment of the holographic grating needs as an input very accurate knowledge of the mechanical interfaces. VTT Automation has designed, built and tested a characterization system for the holographic grating. This system combines the accurate optical imaging measurements with the absolute knowledge of the geometrical parameters at the accuracy of plus or minus 10 micrometers which makes the system unique. The developed system has been used for two breadboard gratings and the qualification model grating. The imaging quality results and their analysis together with alignment procedure utilizing of the knowledge of mechanical interfaces is described.

  19. 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.

  20. 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.