Sample records for large aperture laser

  1. The role of the solvent viscosity on the spatiotemporal instabilities of large aperture dye lasers

    E-print Network

    Rey Juan Carlos, Universidad

    The role of the solvent viscosity on the spatiotemporal instabilities of large aperture dye lasers for publication 27 May 1998 Local intensity fluctuations in a large aperture dye laser have been measured behavior as the molecular polarization orientation driven by the laser field. © 1998 American Institute

  2. Large-aperture laser beam scanner for inter-satellite laser communications ground test: assembly and test

    Microsoft Academic Search

    Jianfeng Sun; Lei Yang; Liren Liu; Qiande Shen; Nan Xu

    2006-01-01

    Inter-satellite laser communications attracted more and more attentions due to its excellent performances compared with the RF communications. But the test and verification of the communication terminals are very difficult because of the accuracy and aperture requirement. Large-aperture laser beam scanner was introduced to simulate the relative movement between satellites in the process of ground test for terminals. The scanner

  3. The role of the molecular dynamics in the local intensity instabilities of large aperture dye lasers

    E-print Network

    Rey Juan Carlos, Universidad

    lasers I. Leyvaa) and J. M. Guerra Departamento de O´ ptica, Facultad de Ciencias Fi´sicas Universidad fluctuations of large aperture dye lasers, and find dependencies on solvent viscosity and active molecular size dye lasers are used in a great deal of practical applications, from isotope enrichment to photody

  4. Study on methods for measuring laser energy of large-aperture beam

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Gao, Haoran; Jia, Jing; Hu, Shaoyun; Fan, Hongying

    2014-12-01

    A experimental method measuring laser energy and energy distributing of large-aperture beam is presented. The experimental equipment is established. The energy and energy distribution of beam, the beam size is ?100mm and ?360mm, are measured. The result show measuring error for laser energy is less than 8%. The energy distribution is basically consistent.

  5. Performance results for Beamlet: A large aperture multipass Nd glass laser

    SciTech Connect

    Campbell, J.H.; Barker, C.E.; VanWonterghem, B.M.; Speck, D.R.; Behrendt, W.C.; Murray, J.R.; Caird, J.A.; Decker, D.E.; Smith, I.C.

    1995-04-11

    The Beamlet laser is a large aperture, flashlamp pumped Nd: glass laser that is a scientific prototype of an advanced Inertial Fusion laser. Beamlet has achieved third harmonic, conversion efficiency of near 80% with its nominal 35cm {times} 35cm square beam at mean 3{omega} fluences in excess of 8 J/cm{sup 2}(3-ns). Beamlet uses an adaptive optics system to correct for aberrations and achieve less than 2 {times} diffraction limited far field spot size.

  6. Specification of large-aperture Nd:phosphate glass laser disks

    Microsoft Academic Search

    Milton J. Shoup; Stephen D. Jacobs; John H. Kelly; Christopher T. Cotton; Samuel F. Morse; Steven A. Kumpan

    1992-01-01

    The purchase of large (15- and 20-cm clear aperture) Brewster-angle laser disks involves the specification of a large number of often conflicting parameters, all of which bear on performance and cost. Furthermore, the laser requirements often approach the state-of-the-art in glass-melting technology and the parameter measurement. This paper enumerates the relevant parameters, the trade-offs made in their selection, and the

  7. Development of large-aperture electro-optical switch for high power laser at CAEP

    NASA Astrophysics Data System (ADS)

    Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Lin, Donghui; Zheng, Jiangang; Zheng, Kuixing

    2015-02-01

    Large-aperture electro-optical switch based on plasma Pockels cell (PPC) is one of important components for inertial confinement fusion (ICF) laser facility. We have demonstrated a single-pulse driven 4×1 PPC with 400mm×400mm aperture for SGIII laser facility. And four 2×1 PPCs modules with 350mm×350mm aperture have been operated in SGII update laser facility. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPCs meet the SGII-U laser requirement of four-pass amplification control. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, and higher reliability. To farther reduce the insert loss of the PPC, research on the large-aperture PPC based on DKDP crystal driven by one pulse is developed. And several single-pulse driven PPCs with 80mm×80mm DKDP crystal have been manufactured and operated in laser facilities.

  8. Fourth harmonic generation of a large-aperture Nd:glass laser

    Microsoft Academic Search

    D. Bruneau; A. M. Tournade; E. Fabre

    1985-01-01

    Basic properties of the fourth harmonic conversion of 1.053-..mu..m laser radiation with KDP crystals are experimentally determined. Optimization of crystal thickness, based on numerical simulations is discussed. A large aperture conversion cell combining second and fourth harmonic generators has been designed. Overall conversion efficiencies (..omega.. ..-->.. 4..omega..) in excess of 40% have been achieved for incident laser intensities between 1

  9. Off-axis multipass amplifier as a large aperture driver stage for fusion lasers.

    PubMed

    Murray, J E; Downs, D C; Hunt, J T; Hermes, G L; Warren, W E

    1981-03-01

    A multipass amplifier configuration is described which has potential as a large aperture, high gain driver stage for fusion laser systems. We avoid the present limitations of large aperture switches by using an off-angle geometry that does not require an optical switch. The saturated gain characteristics of this multipass amplifier are optimized numerically. Three potential problems are investigated experimentally, self-lasing, output beam quality, and amplified spontaneous emission output. The results indicate comparable cost for comparable performance to a linear chain, with some operational advantage for the multipass driver stage. PMID:20309212

  10. Partial feedback unstable resonator on small scale supersonic large aperture chemical laser

    NASA Astrophysics Data System (ADS)

    Wang, Hongyan; Wang, Rui; Li, Lei

    2015-05-01

    There is always a challenge on large aperture medium power laser's resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan'ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.

  11. Large aperture plasma electrodes Pockels cell for multi-pass amplified scheme of SGII upgrading laser

    NASA Astrophysics Data System (ADS)

    Wu, Dengsheng; Jing, Feng; Li, Ping; Zhang, Xiongjun; Zhang, Jun; Tian, Xiaolin

    2012-06-01

    The multi-pass amplified scheme of SGII upgrading laser is similar as that of NIF. Large aperture plasma electrodes Pockels cell (PEPC) is the key unit of this amplified scheme. The transit time that laser beam passes through the PEPC for the first time and second time is about 270ns. PEPC should switch the state between ON and OFF in 270ns. The response time of the PEPC driven by positive-negative switching pulses can not satisfy the demand of SGII upgrading laser due to the higher generator impedance. In the single-pulse-process, the low-impedance high voltage generator based on double Blumlein pulse-forming line is used to drive the PEPC. The amplitude of single pulse is up to 21kV, while the impedance of the generator is only 6.25?. The theoretical charge time of the PEPC with 350mm×350mm aperture is about 54ns, and the response time of PEPC is less than 170ns in the single-pulse-process. The response time is reduced greatly. The switching efficiencies with full aperture are higher than 99.7%. The extinction contrast exceeds 381. The top width of the time window is larger than 160ns, and the bottom width is about 400ns. All the experimental results can meet the specification of SGII upgrading laser.

  12. Emission tomography of laser induced plasmas with large acceptance angle apertures

    E-print Network

    Shabanov, Sergei

    2010-01-01

    It is proposed to use apertures with large acceptance angles to reduce the integration time when studying the emissivity of laser induced plasmas by means of the Abel inversion method. The spatial resolution lost due to contributions of angled lines of sight to the intensity data collected along the plasma plume diameter is restored by a special numerical data processing. The procedure is meant for the laser induced plasma diagnostics and tomography when the integration time needed to achieve a reasonable signal to noise ratio exceeds a characteristic time scale of the plasma state variations which is short especially at early stages of the plasma evolution.

  13. Large aperture optical switching devices

    SciTech Connect

    Goldhar, J.; Henesian, M.A.

    1983-12-12

    We have developed a new approach to constructing large aperture optical switches for next generation inertial confinement fusion lasers. A transparent plasma electrode formed in low pressure ionized gas acts as a conductive coating to allow the uniform charging of the optical faces of an electro-optic material. In this manner large electric fields can be applied longitudinally to large aperture, high aspect ratio Pockels cells. We propose a four-electrode geometry to create the necessary high conductivity plasma sheets, and have demonstrated fast (less than 10 nsec) switching in a 5x5 cm aperture KD*P Pockels cell with such a design. Detaid modelling of Pockels cell performance with plasma electrodes has been carried out for 15 and 30 cm aperture designs.

  14. Segmented Electron-Beam Diodes for Pumping Large-Aperture KrF-Laser Amplifiers

    NASA Astrophysics Data System (ADS)

    Okuda, Isao; Owadano, Yoshiro

    2001-08-01

    The design of the segmented electron-beam (e-beam) diodes and e-beam generation in the 60-cm aperture KrF-laser amplifier in our laboratory are reported. Reduction of self-magnetic fields in the segmented-diode configuration to reduce e-beam pinching is discussed with the measured e-beam currents. Diode segmentation in a still larger-aperture amplifier for inertial-fusion-energy drivers is also discussed.

  15. Performance of large-aperture optical switches for high-energy inertial-confinement fusion lasers

    SciTech Connect

    Rhodes, M.A.; Woods, B.; DeYoreo, J.J.; Roberts, D.; Atherton, L.J. [University of California, Lawrence Livermore National Laboratory, P.O. Box 808 L-490, Livermore, California 94550 (United States)

    1995-08-20

    We describe the design and performance of large-aperture ({lt}30 cm {times} 30 cm) optical switches that have demonstrated, for the first time to our knowledge, active switching of a high-energy ({lt}5 kJ) optical pulse in an inertial-confinement fusion laser. These optical switches, which consist of a plasma-electrode Pockels cell (PEPC) and a passive polarizer, permit the design of efficient, multipass laser amplifiers. In a PEPC, plasma discharges on the faces of a thin (1-cm) electro-optic crystal (KDP or KD{bold |}P) act as highly conductive and transparent electrodes. These plasma electrodes facilitate rapid ({lt}100 ns) and uniform charging of the crystal to the half-wave voltage and discharging back to 0 V. We discuss the operating principles, design, optical performance, and technical issues of a 32 cm {times} 32 cm prototype PEPC with both KDP and KD{bold |}P crystals, and a 37 cm {times} 37 cm PEPC with a KDP crystal for the Beamlet laser. This PEPC recently switched a 6-kJ, 3-ns pulse in a four-pass cavity.

  16. A fundamental mode Nd:GdVO4 laser pumped by a large aperture 808 nm VCSEL

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Ma, J. L.; Yan, C. L.; Liu, G. J.; Ma, X. H.; Gong, J. F.; Feng, Y.; Wei, Z. P.; Wang, Y. X.; Zhao, Y. J.

    2013-05-01

    A fundamental mode Nd:GdVO4 laser pumped by a vertical cavity surface emitting laser (VCSEL) is experimentally demonstrated. The VCSEL has a circular output-beam which makes it easier for it to be directly coupled to a Nd:GdVO4 microcrystal. In our research, a large aperture 808 nm VCSEL, with a multi-ring-shaped aperture (MRSA) and an almost Gaussian-shaped far-field profile, is used as the pumping source. Experimental results for the Nd:GdVO4 laser pumped by the VCSEL are presented. The maximum output peak power of 0.754 W is obtained under a pump peak power of 1.3 W, and the corresponding opto-optic conversion efficiency is 58.1%. The average slope efficiency is 65.8% from the threshold pump power of 0.2 W to the pump power of 1.3 W. The laser beam quality factors are measured to be {M}x2=1.2 0 and {M}y2=1.1 5.

  17. Large-aperture optical-switching devices

    SciTech Connect

    Goldhar, J.; Henesian, M.A.

    1984-01-01

    A new approach to constructing large aperture optical switches for next-generation inertial-confinement fusion lasers was developed. A transparent plasma electrode formed in low-pressure ionized gas acts as a conductive coating to allow the uniform charging of the optical faces of an electro-optic material. In this manner large electric fields can be applied longitudinally to large-aperture, high-aspect-ratio Pockels cells. A four-electrode geometry was proposed to create the necessary high-conductivity plasma sheets, and fast (<10 nsec) switching in a 5 x 5 cm aperture KD*P Pockels cell with such a design was demonstrated. Detailed modeling of Pockels-cell performance with plasma electrodes was carried out for 15- and 30-cm aperture designs. 10 references, 8 figures, 2 tables.

  18. Performance of a prototype for a large-aperture multipass Nd:glass laser for inertial confinement fusion

    Microsoft Academic Search

    Bruno M. van Wonterghem; John R. Murray; Jack H. Campbell; D. Ralph Speck; Charles E. Barker; Ian C. Smith; Donald F. Browning; William C. Behrendt

    1997-01-01

    The Beamlet is a single-beam prototype of future multibeam megajoule-class Nd:glass laser drivers for inertial confinement fusion. It uses a multipass main amplifier, adaptive optics, and efficient, high-fluence frequency conversion to the third harmonic. The Beamlet amplifier contains Brewster-angle glass slabs with a clear aperture of 39 cm 39 cm and a full-aperture plasma-electrode Pockels cell switch. It has been

  19. Performance of a prototype for a large-aperture multipass Nd:glass laser for inertial confinement fusion

    Microsoft Academic Search

    Bruno M. Van Wonterghem; John R. Murray; Jack H. Campbell; D. Ralph Speck; Charles E. Barker; Ian C. Smith; Donald F. Browning; William C. Behrendt

    1997-01-01

    The Beamlet is a single-beam prototype of future multibeam megajoule-class Nd:glass laser drivers for inertial confinement fusion. It uses a multipass main amplifier, adaptive optics, and efficient, high-fluence frequency conversion to the third harmonic. The Beamlet amplifier contains Brewster-angle glass slabs with a clear aperture of 39 cmÃ39 cm and a full-aperture plasma-electrode Pockels cell switch. It has been successfully

  20. Distributed apertures in laminar flow laser turrets

    NASA Astrophysics Data System (ADS)

    Tousley, B. B.

    1981-09-01

    Assume a technology that permits undistorted laser beam propagation from the aft section of a streamlined turret. A comparison of power on a distant airborne target is made between a single aperture in a large scale streamlined turret with a turbulent boundary layer and various arrays of apertures in small scale streamlined turrets with laminar flow. The array performance is mainly limited by the size of each aperture. From an array one might expect, at best, about 40 percent as much power on the target as from a single aperture with equal area. Since the turbulent boundary layer on the large single-turret has negligible effect on beam quality, the array would be preferred (if all development efforts were essentially equal) only if a laminar wake is an operational requirement.

  1. Large aperture diffractive space telescope

    DOEpatents

    Hyde, Roderick A. (Livermore, CA)

    2001-01-01

    A large (10's of meters) aperture space telescope including two separate spacecraft--an optical primary objective lens functioning as a magnifying glass and an optical secondary functioning as an eyepiece. The spacecraft are spaced up to several kilometers apart with the eyepiece directly behind the magnifying glass "aiming" at an intended target with their relative orientation determining the optical axis of the telescope and hence the targets being observed. The objective lens includes a very large-aperture, very-thin-membrane, diffractive lens, e.g., a Fresnel lens, which intercepts incoming light over its full aperture and focuses it towards the eyepiece. The eyepiece has a much smaller, meter-scale aperture and is designed to move along the focal surface of the objective lens, gathering up the incoming light and converting it to high quality images. The positions of the two space craft are controlled both to maintain a good optical focus and to point at desired targets which may be either earth bound or celestial.

  2. HI-CLASS on AEOS: a large-aperture laser radar for space surveillance\\/situational awareness investigations

    Microsoft Academic Search

    Mark A. Kovacs; Gordon L. Dryden; Richard H. Pohle; Kirstie Ayers; Richard A. Carreras; Linda L. Crawford; Russell Taft

    2001-01-01

    The Air Force Research Laboratory\\/Directed Energy Directorate (AFRL\\/DE) via the ALVA (Applications of Lidars for Vehicles with Analysis) program installed in late 2000 a wideband, 12 J 15 Hz CO2 laser radar (ladar) on the 3.67 meter aperture AEOS (Advanced Electro-Optics System) telescope. This system is part of the Maui Space Surveillance System (MSSS), on the summit of Haleakala, Maui,

  3. Modeling of large aperture third harmonic frequency conversion of high power Nd:glass laser systems

    SciTech Connect

    Henesian, M.A.; Wegner, P.J.; Speck, D.R.; Bibeau, C.; Ehrlich, R.B.; Laumann, C.W.; Lawson, J.K.; Weiland, T.L.

    1991-03-13

    To provide high-energy, high-power beams at short wavelengths for inertial-confinement-fusion experiments, we routinely convert the 1.053-{mu}m output of the Nova, Nd:phosphate-glass, laser system to its third-harmonic wavelength. We describe performance and conversion efficiency modeling of the 3 {times} 3 arrays potassium-dihydrogen-phosphate crystal plates used for type II/type II phase-matched harmonic conversion of Nova 0.74-m diameter beams, and an alternate type I/type II phase-matching configuration that improves the third-harmonic conversion efficiency. These arrays provide energy conversion of up to 65% and intensity conversion to 70%. 19 refs., 11 figs.

  4. Hybrid assembled micro scanner array with large aperture and their system integration for a 3D ToF laser camera

    NASA Astrophysics Data System (ADS)

    Sandner, Thilo; Baulig, Claudia; Grasshoff, Thomas; Wildenhain, Michael; Schwarzenberg, Markus; Dahlmann, Hans-Georg; Schwarzer, Stefan

    2015-03-01

    This paper presents a large aperture micro scanning mirror (MSM) array especially developed for the novel 3D-laser camera Fovea3D. This 3D-camera uses a pulsed ToF technique with 1MVoxel distance measuring rate and targets for a large measurement range of 30…100m and FOV of 120°x60° at video like frame rates. To guarantee a large reception aperture of ? 20mm, large FOV and 3200 Hz bi-directional scanning frequency at the same time, a hybrid assembled MSM array was developed consisting of 22 reception mirrors and a separate sending mirror. A hybrid assembly of frequency selected scanner elements and a driving in parametric resonance were chosen to enable a fully synchronized operation of all scanner elements. For position feedback piezo-resistive position sensors are integrated on each MEMS chip. The paper discusses details of the MEMS system integration including the synchronized operation of multiple scanning elements.

  5. the Large Aperture GRB Observatory

    SciTech Connect

    Bertou, Xavier [Centro Atomico Bariloche (Argentina)

    2009-04-30

    The Large Aperture GRB Observatory (LAGO) aims at the detection of high energy photons from Gamma Ray Bursts (GRB) using the single particle technique (SPT) in ground based water Cherenkov detectors (WCD). To reach a reasonable sensitivity, high altitude mountain sites have been selected in Mexico (Sierra Negra, 4550 m a.s.l.), Bolivia (Chacaltaya, 5300 m a.s.l.) and Venezuela (Merida, 4765 m a.s.l.). We report on the project progresses and the first operation at high altitude, search for bursts in 6 months of preliminary data, as well as search for signal at ground level when satellites report a burst.

  6. HI-CLASS on AEOS: a large-aperture laser radar for space surveillance/situational awareness investigations

    NASA Astrophysics Data System (ADS)

    Kovacs, Mark A.; Dryden, Gordon L.; Pohle, Richard H.; Ayers, Kirstie; Carreras, Richard A.; Crawford, Linda L.; Taft, Russell

    2001-12-01

    The Air Force Research Laboratory/Directed Energy Directorate (AFRL/DE) via the ALVA (Applications of Lidars for Vehicles with Analysis) program installed in late 2000 a wideband, 12 J 15 Hz CO2 laser radar (ladar) on the 3.67 meter aperture AEOS (Advanced Electro-Optics System) telescope. This system is part of the Maui Space Surveillance System (MSSS), on the summit of Haleakala, Maui, HI. This ladar adopts the technology successfully demonstrated by the first generation HI-CLASS (High Performance CO2) Ladar Surveillance Sensor) operating on the nearby 0.6 meter aperture Laser Beam Director (LBD) and developed under the Field Ladar Demonstration program, jointly sponsored by AFRL/DE and the Army's Space and Missile Defense Command. The moderate power (approximately 180 watts) HI-CLASS/AEOS system generates multiple, coherent waveforms for precision satellite tracking and characterization of space objects for 1 m2 targets at ranges out to 10,000 km. This system also will be used to track space objects smaller than30 cm at ranges to 2,000 km. A third application of this system is to provide data for developing satellite identification, characterization, health and status techniques. This paper will discuss the operating characteristics and innovative features of the new system. The paper will also review recent results in support of AF needs, demonstrations, experiments, as well as planned activities that directly support applications in the DoD, scientific, and commercial arenas.

  7. Large sparse aperture space optical systems

    Microsoft Academic Search

    Aden B. Meinel; Marjorie P. Meinel

    2002-01-01

    The issue of how best to distribute a large optical collecting area is revisited, including the added integration time required for a scene imaged by sparse-aperture configurations to be processed to equal that of a filled aperture, and also its influence on system architecture. The optical performance of three sparse-aperture configurations arising from a 1998 study is presented as a

  8. Performance of a prototype for a large-aperture multipass Nd:glass laser for inertial confinement fusion

    NASA Astrophysics Data System (ADS)

    van Wonterghem, Bruno M.; Murray, John R.; Campbell, Jack H.; Speck, D. Ralph; Barker, Charles E.; Smith, Ian C.; Browning, Donald F.; Behrendt, William C.

    1997-07-01

    The Beamlet is a single-beam prototype of future multibeam megajoule-class Nd:glass laser drivers for inertial confinement fusion. It uses a multipass main amplifier, adaptive optics, and efficient, high-fluence frequency conversion to the third harmonic. The Beamlet amplifier contains Brewster-angle glass slabs with a clear aperture of 39 cm 39 cm and a full-aperture plasma-electrode Pockels cell switch. It has been successfully tested over a range of pulse lengths from 1 10 ns up to energies at 1.053 m of 5.8 kJ at 1 ns and 17.3 kJ at 10 ns. A 39-actuator deformable mirror corrects the beam quality to a Strehl ratio of as much as 0.4. The 1.053- m output has been converted to the third harmonic at efficiencies as high as 80 and fluences as high as 8.7 J cm 2 for 3-ns pulses.

  9. Intracavity frequency doubling in a wide-aperture argon laser

    SciTech Connect

    Abdullina, S R; Babin, S A; Vlasov, Aleksandr A; Kablukov, S I [Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2005-09-30

    The four-mirror cavity with a BBO crystal for frequency doubling in a wide-aperture argon laser is optimised. The dependences of the second-harmonic power on the displacement of a focusing mirror, the displacement of the crystal, and the discharge current are measured. These dependences are in good agreement with calculations. After optimisation, {approx}1 W of UV laser radiation at 244 nm was obtained with the conversion efficiency twice as large as that for the known similar lasers. It is shown that the increase in the efficiency was achieved mainly due to the increase in the discharge-tube aperture. (nonlinear optical phenomena)

  10. PULSE POWER REQUIREMENTS FOR LARGE APERTURE OPTICAL SWITCHES BASED ON PLASMA ELECTRODE POCKELS CELLS

    Microsoft Academic Search

    Mark A. Rhodes; J. Taylor

    1992-01-01

    We discuss very large-aperture optical switches (greater than 30x30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on singlepass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a

  11. Design of a laser cutting system at large distance by a synthetic aperture diffractive optical system in reflection mode

    Microsoft Academic Search

    Bernard Kress; G. Tahmouch; Patrick Meyrueis

    1997-01-01

    Laser material processing by the mean of Diffractive Optical Elements (DOEs) is a promising field, that has not yet entered the industrial world, except for hybrid on-axis spherical or aspherical lenses fabricated by diamond turning. Laser cutting, engraving, welding, and heat treatment are several applications among the potential of numeric-type beam shaping DOEs, designed and optimized by iterative algorithms and

  12. Large aperture electro-optical switch

    SciTech Connect

    Goldhar, J.; Henesian, M.A.

    1984-12-19

    A transparent plasma electrode formed in low pressure ionized gas acts as a conductive coating to allow the uniform charging of the optical faces of an electro-optic material. Experiments with large aperture Pockels cells up to 27 cm are now in progress.

  13. Large-aperture, high-damage-threshold optics for beamlet

    SciTech Connect

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J.; Kozlowski, M.R.; Maney, R.T.; Montesanti, R.C.; Sheehan, L.M.; Barker, C.E.

    1995-02-23

    Beamlet serves as a test bed for the proposed NIF laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of our previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, we discuss the properties and characteristics of the large-aperture optics used on Beamlet.

  14. Large-aperture, high-damage-threshold optics for beamlet

    SciTech Connect

    Campbell, J.H.; Atherton, L.J.; DeYoreo, J.J. [and others

    1996-06-01

    Beamlet serves as a test bed for the proposed National Ignition Facility (NIF) laser design and components. Therefore, its optics are similar in size and quality to those proposed for the NIF. In general, the optics in the main laser cavity and transport section of Beamlet are larger and have higher damage thresholds than the optics manufactured for any of the previous laser systems. In addition, the quality of the Beamlet optical materials is higher, leading to better wavefront quality, higher optical transmission, and lower-intensity modulation of the output laser beam than, for example, that typically achieved on Nova. In this article, the authors discuss the properties and characteristics of the large-aperture optics used on Beamlet.

  15. Large-aperture phase-shifting interferometer for PSD measurements

    NASA Astrophysics Data System (ADS)

    Gu, Yuanyuan; Xu, Qiao; Cai, Lin

    2000-10-01

    In modern high power laser, reflected and transmitted wavefronts of optical components are being specified by the power spectral density function (PSD). In order to ensure accurate measurements of PSD of optical components, the test systems must be calibrated. This paper presents the results of the components wavefront measurements using large aperture laser Fizeau phase shifting interferometer. This paper also describes the testing results of optical components in size from approximately 100 mm X 100 mm to 240 mm X 480 mm, substrate including UBK7 glass, KDP crystal, Nd-glass. These measurements are performed after polishing, after coating and in Brewster. Using these data, we can qualify optical components and improve our fabrication processes under optics development program.

  16. Large-aperture Faraday isolator based on a terbium gallium garnet crystal.

    PubMed

    Mironov, E A; Zheleznov, D S; Starobor, A V; Voitovich, A V; Palashov, O V; Bulkanov, A M; Demidenko, A G

    2015-06-15

    Unique Faraday isolator based on a TGG single crystal with aperture diameter of 40 mm for high average power lasers has been fabricated and investigated experimentally. The device provides a stable isolation ratio over 30 dB for large-radius laser beams with kilowatt average power radiation typical for high-power applications. PMID:26076264

  17. High power 808 nm vertical cavity surface emitting laser with multi-ring-shaped-aperture structure

    NASA Astrophysics Data System (ADS)

    Hao, Y. Q.; Shang, C. Y.; Feng, Y.; Yan, C. L.; Zhao, Y. J.; Wang, Y. X.; Wang, X. H.; Liu, G. J.

    2011-02-01

    The carrier conglomeration effect has been one of the main problems in developing electrically pumped high power vertical cavity surface emitting laser (VCSEL) with large aperture. We demonstrate a high power 808 nm VCSEL with multi-ring-shaped-aperture (MRSA) to weaken the carrier conglomeration effect. Compared with typical VCSEL with single large aperture (SLA), the 300-?m-diameter VCSEL with MRSA has more uniform near field and far field patterns. Moreover, MRSA laser exhibits maximal CW light output power 0.3 W which is about 3 times that of SLA laser. And the maximal wall-plug efficiency of 17.4% is achieved, higher than that of SLA laser by 10%.

  18. Research on materials for the large aperture space mirror

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuwei; Wang, Bin; Gong, Hui; Gu, Zhenyv; Liu, Yiliang

    2014-11-01

    The properties and developments of materials for large aperture space mirrors, which are pursued for high-resolution earth observation and deep space exploration, are summarized in this paper. All these materials were classified into several kinds depend on their substance and performance. Their advantages and disadvantages in manufacturing large aperture space mirrors were discussed; especially their fabrication, optical machining and application. The trends of development of materials for large space mirrors are overviewed.

  19. Inverse synthetic aperture 3-D imaging laser radar

    Microsoft Academic Search

    Jin He; Xiao-you Yang; Jian-feng Wang; Qun Zhang

    2010-01-01

    Three-dimensional (3-D) Image can represent target's physical characteristic well and improve target recognition capability, however, conventional optical imaging radar which is limited by the array units or scan system cannot realize the high resolution imaging for moving targets. This paper combines the inverse synthetic aperture technology, laser signal and interferometric technique to suggest a new radar system which is called

  20. ADVANCED TECHNOLOGY LARGE-APERTURE SPACE TELESCOPE (ATLAST)

    E-print Network

    Sirianni, Marco

    ADVANCED TECHNOLOGY LARGE-APERTURE SPACE TELESCOPE (ATLAST): A TECHNOLOGY ROADMAP FOR THE NEXT = Northrop Grumman Aerospace Systems 8 = Jet Propulsion Laboratory, California Institute of Technology 9 = Johnson Space Flight Center 10 = Princeton University 11 = Jacobs ESTS Group @ MSFC #12;Advanced

  1. Extracting spatial information from large aperture exposures of diffuse sources

    Microsoft Academic Search

    J. T. Clarke; H. W. Moos

    1981-01-01

    The spatial properties of large aperture exposures of diffuse emission can be used both to investigate spatial variations in the emission and to filter out camera noise in exposures of weak emission sources. Spatial imaging can be accomplished both parallel and perpendicular to dispersion with a resolution of 5-6 arc sec, and a narrow median filter running perpendicular to dispersion

  2. Large Aperture, Scanning, L-Band SAR

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Bach, Vinh; Grando, Maurio; Quijano, Ubaldo; Smith, Phil; Zawadzki, Mark

    2011-01-01

    We have developed the first L-band membrane-based active phased array. The antenna is a 16x16 element patch array with dimensions of 2.3mx2.6m. The array uses membrane-compatible Transmit/Receive (T/R) modules for electronic beam steering. We will discuss the antenna design, the fabrication of this large array, the T/R module development, the signal distribution approach and the measured results of the array.

  3. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 [times] 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V[sub x] ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V[sub x], the polarization of an incoming, linearly polarized, laser beam is rotated by 90[degree]. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 [times] 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  4. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    SciTech Connect

    Rhodes, M.A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 {times} 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V{sub x} ( 8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V{sub x}, the polarization of an incoming, linearly polarized, laser beam is rotated by 90{degree}. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 {times} 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  5. Pulse power requirements for large aperture optical switches based on plasma electrode Pockels cells

    NASA Astrophysics Data System (ADS)

    Rhodes, M. A.; Taylor, J.

    1992-06-01

    We discuss very large-aperture optical switches (greater than 30 x 30 cm) as an enabling technology for inertial confinement fusion drivers based on multipass laser amplifiers. Large-scale laser fusion drivers such as the Nova laser have been based on single-pass amplifier designs in part because of the unavailability of a suitable large-aperture switch. We are developing an optical switch based on a Pockels cell employing plasma-electrodes. A plasma-electrode Pockels cell (PEPC) is a longitudinal-mode Pockels cell in which a plasma discharge is formed on each side of an electro-optic crystal (typically KDP or deuterated KDP, often designated KD*P). The plasmas formed on either side of the crystal act as transparent electrodes for a switching-pulse and are intended to allow uniform charging of the entire crystal. The switching-pulse is a nominally rectangular high-voltage pulse equal to the half-wave voltage V(sub x) (8 kV for KD*P or 17 kV for KDP) and is applied across the crystal via the plasma-electrodes. When the crystal is charged to V(sub x), the polarization of an incoming, linearly polarized, laser beam is rotated by 90 degree. When used in conjunction with an appropriate, passive polarizer, an optical switch is thus realized. A switch with a clear aperture of 37 x 37 cm is now in construction for the Beamlet laser which will serve as a test bed for this switch as well as other technologies required for an advanced NOVA laser design. In this paper, we discuss the unique power electronics requirements of PEPC optical switches.

  6. Mission definition for a large-aperture microwave radiometer spacecraft

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.

    1981-01-01

    An Earth-observation measurements mission is defined for a large-aperture microwave radiometer spacecraft. This mission is defined without regard to any particular spacecraft design concept. Space data application needs, the measurement selection rationale, and broad spacecraft design requirements and constraints are described. The effects of orbital parameters and image quality requirements on the spacecraft and mission performance are discussed. Over the land the primary measurand is soil moisture; over the coastal zones and the oceans important measurands are salinity, surface temperature, surface winds, oil spill dimensions and ice boundaries; and specific measurement requirements have been selected for each. Near-all-weather operation and good spatial resolution are assured by operating at low microwave frequencies using an extremely large aperture antenna in a low-Earth-orbit contiguous mapping mode.

  7. Research on 2x1 plasma electrode electro-optical switch with large aperture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiong Jun; Zheng, Kui Xing; Feng, B.; Wu, D. S.; Lu, J. P.; Tian, X. L.; Jin, F.; Sui, Zhan; Wei, Xiaofeng; Zhang, Xiaomin

    2005-01-01

    In conceptual design of the prototype for SG-III facility, a full aperture electro-optical switch was placed between the cavity mirror and the main amplifier to isolate the reflected beams. The beam on the cavity mirror is 240mm×240mm square. Pockells cells of conversional design with coaxial ring electrodes can not scale to such large square aperture. In the 1980s, a plasma electrode Pockels cell (PEPC) concept was invented at LLNL. It uses transparent plasma electrode formed through gas discharge as the electrodes to apply the voltage across switching crystal to rotate the polarization of a transmitted laser beam. And it can be scaled to large aperture with thin crystal. So the switch which would be used in SG-III is based on this technology. The technical integration line as a prototype of SG-III laser is actually a 4×2 beam bundle. And the full aperture optical switch is mechanically designed four apertures as a removable unit, and electrically two 2×1 PEPC putting together. So we built a 2×1 PEPC to develop the technology first. The 2×1 PEPC is a sandwich structure made of an insulating mid plane between a pair of plasma chambers. The frame of both plasma chambers are machining in duralumin. Each chamber is installed with a planar magnetic cathode and four segments spherical anodes made from stainless steel. The cathode and anode are insulated from the housing with a special shell made from plastic, and plasma is insulated from the housing by an 80-?m-thick anodic coating on the duralumin. The two plasma chambers are separated by a mid plane of glass frame with two square holes. The two holes are filled by two electro-optical crystals with a 240-mm square aperture. With the optimized operating pressure and the electrical parameters, a very good homogeneity and low resistivity plasma electrode is obtained. Finally we tested its switching performance to simulate the case that it will be used in the SG-III prototype facility. It works with a quarter wave delay voltage and the laser beam passes through PEPC twice. The average switching efficiency across the entire aperture is greater than 98.6%, the rising time of the switch is about 83ns, and the transmission of the switch is 86%.

  8. Wide-aperture electric-discharge nitrogen laser

    SciTech Connect

    Konovalov, I N; Panchenko, Aleksei N; Tarasenko, Viktor F; Tel'minov, E A [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

    2007-07-31

    The parameters of a wide-aperture nitrogen laser pumped by a generator with the inductive energy storage and a SOS diode opening switch or a generator with the capacitive energy storage are studied. The gas preionisation was performed by soft X-rays. The size of the active volume of the laser was 10x6x100 cm. The output energy and power obtained at the 337.1-nm C {sup 3{Pi}}{sub u} - B {sup 3{Pi}}{sub g} transition are maximal for electric-discharge nitrogen lasers. The output energy in the second positive system of nitrogen in the N{sub 2}-SF{sub 6} mixture achieved 110 mJ for a peak power of 6 MW. Due to an increase in voltage across the laser gap in nitrogen mixtures with NF{sub 3}, the generation of {approx}35-mJ, 100-ns pulses was obtained in the quasi-stationary stage of the discharge. (lasers)

  9. Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures

    NASA Astrophysics Data System (ADS)

    Bleszynski, E.; Bleszynski, M.; Jaroszewicz, T.

    2013-05-01

    An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and back-projection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient-corrected data and extracts the absolute phase value, removing in this way phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus the scene and determine relative target-target distances.

  10. Extracting spatial information from large aperture exposures of diffuse sources

    NASA Astrophysics Data System (ADS)

    Clarke, J. T.; Moos, H. W.

    The spatial properties of large aperture exposures of diffuse emission can be used both to investigate spatial variations in the emission and to filter out camera noise in exposures of weak emission sources. Spatial imaging can be accomplished both parallel and perpendicular to dispersion with a resolution of 5-6 arc sec, and a narrow median filter running perpendicular to dispersion across a diffuse image selectively filters out point source features, such as reseaux marks and fast particle hits. Spatial information derived from observations of solar system objects is presented.

  11. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Leonhardt, W.J.; Mapes, M.

    1993-07-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.

  12. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Leonhardt, W.J.; Mapes, M.

    1993-01-01

    Large vacuum vessels are employed downstream of fixed targets in High Energy Physics experiments to provide a long path for particles to traverse without interacting with air molecules. These vessels generally have a large aperture opening known as a vacuum window which employs a thin membrane to preserve the vacuum environment yet allows the particles to pass through with a minimal effect on them. Several large windows have been built using a composite of Kevlar/Mylar including circular windows to a diameter of 96.5 cm and rectangular windows up to 193 cm x 86 cm. This paper describes the design, fabrication, testing and operating experience with these windows and relates the actual performance to theoretical predictions.

  13. [Spectral calibration for the large aperture infrared radiometer].

    PubMed

    Ye, Zhao; Wan, Zhi; Li, Xian-Sheng; Ren, Jian-Wei; Liu, Hong-Xing

    2012-07-01

    The present paper introduced a spectral calibration method to calibrate a large aperture infrared radiation facility. We developed a radiometer which consisted of optical system, infrared detectors(cavity pyroelectric detector and HgCdTe detector 2 - 14 microm), fine mechanical modulator, lock in amplifier, signal processor, etc. At first, we analyzed the method on how to measure the spectral calibration of the large aperture infrared radiometer, and established the spectral calibration facility. Then, we tested the nonlinear response for the cavity pyroelectric detector and HgCdTe detector. Finally, we used the cavity pyroelectric detector to calibrate the relative spectral responsivity of HgCdTe detector at several wavelengths on the facility. Through the comparison of the two methods for measuring the relative spectral responsivity, the average of multiple measurements and comparative analysis of two methods were given. The uncertainty analysis of the whole system showed that the measurement uncertainty of the facility was better than 3.4%. PMID:23016371

  14. Development of an efficient large-aperture high damage-threshold sol-gel diffraction grating.

    SciTech Connect

    Ashley, Carol S.; Rambo, Patrick K.; Schwarz, Jens; Dunphy, Darren Robert; Branson, Eric D.; Smith, Ian Craig; Johnson, William Arthur; Reed, Scott T.; Cook, Adam W.

    2005-03-01

    In order to develop the next generation of high peak intensity lasers, new grating technology providing higher damage thresholds and large apertures is required. The current assumption is that this technical innovation will be multilayer dielectric gratings, wherein the uppermost layer of a thin film mirror is etched to create the desired binary phase grating. A variant of this is explored with the upper grating layer being a lower density gelatin-based volume phase grating in either sol-gel or dichromated gelatin. One key benefit is the elimination of the etching step.

  15. Design of large aperture, low mass vacuum windows

    SciTech Connect

    Mapes, M.; Leonhardt, W.J. (Brookhaven National Laboratory, Upton, New York 11973 (United States))

    1993-07-01

    Large aperture, low mass, thin vacuum windows are required to minimize beam loss in the beam lines of particle accelerators as the products of nuclear collisions move from upstream targets to downstream detectors. This article describes the design, fabrication, testing, and operating experience of a large rectangular vacuum window, 122 cm[times]61 cm, and two circular windows of 91.4 and 96.5 cm diam. These window designs utilize a composite Kevlar 29 fabric and Mylar laminate as a window material with a typical combined thickness of 0.35 mm. Data for several material thicknesses are also presented. The windows are usually designed to withstand a pressure differential of two to three atmospheres to achieve the required factor of safety. These windows are typically used in the medium vacuum range of 10[sup [minus]4] Torr. The equations used to predict the behavior of the window material will also be discussed.

  16. Guidelines for the design of very large aperture quadrupole magnets

    SciTech Connect

    Daeel, A.; Jorda, J.P.; Kircher, F.; Mayri, C. [CEA-DSM/DAPNIA, Gif-sur-Yvette (France). Service Technique de Cryogenie et de Magnetisme] [CEA-DSM/DAPNIA, Gif-sur-Yvette (France). Service Technique de Cryogenie et de Magnetisme

    1996-07-01

    Very large aperture quadrupole magnets have been recently considered as possible spectrometers on high energy colliders. The interesting characteristics are zero field on beam axis, low fields at small angles, transverse field at large angles. Dimension range is 1 m to 5 m for clear bore and 2 m to 8 m for length; typical maximum field is 2.5 T. Superconducting magnets with cosine 2 {theta} structure, coils with one or two layers and iron yoke have been modeled. Use of two types of conductors have been investigated: Rutherford cable and aluminium stabilized composite. The paper describes the optimization procedure and gives diagrams of feasibility. Two alternative structures are mentioned: superferric and active shield magnets.

  17. Development of a large aperture Nb3Sn racetrack quadrupolemagnet

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich,Daniel R.; Gourlay, Steven A.; Hannaford, Charles R.; Hafalia, AurelioR.; Lietzke, Alan F.; Mattafirri, Sara; McInturff, Alfred D.; Nyman,Mark; Sabbi, Gianluca

    2005-04-14

    The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb{sub 3}Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb{sub 3}Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are prestressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed.

  18. SLGLAO: An all-sky, wide field adaptive optics system for large aperture telescopes

    Microsoft Academic Search

    M. C. Britton; K. Taylor

    2004-01-01

    This paper describes an adaptive optics concept that uses a single sodium laser beacon driving a single deformable mirror to achieve partial compensation of atmospheric turbulence over a relatively wide field of view. The angular size of the corrected field of view increases with aperture diameter, while the degree of partial compensation decreases with aperture diameter. For a 30 meter

  19. Application of Large Aperture Emats to Weld Inspection

    NASA Astrophysics Data System (ADS)

    Maclauchlan, D. T.; Clark, S. P.; Hancock, J. W.

    2008-02-01

    One of the most significant developments in EMAT operation is the incorporation of phased array techniques. Phased array EMATs enable electronic beam steering and focusing while operating with temporally short pulses for good range resolution. Using phased array EMAT operation, multiple high powered pulsers are combined in the generation of the ultrasonic wave and multiple elements are combined in the reception of the ultrasonic wave, for improved sensitivity. EMATs make it practical to operate with shear horizontal (SH) waves and scan over a metal part's surface. An EMAT generated line force at the surface launches shear horizontal waves with uniform amplitude for beam angles from -90° to 90°. Shear horizontal waves also reflect without mode conversion from surfaces that are parallel to the polarization of the shear wave displacements. The combination of these advantages makes phased array EMATs well suited for weld inspection. Recently, BWXT Services has developed a 32 active channel EMAT phased array system for operation up to 5 MHz. In addition, each element can be constructed with several sub-elements, alternating in polarity, to effectively multiply the number of active elements for a restricted range of beam angles. For example by using elements comprised of 4 sub elements, a 128 active element aperture designed for operation with a nominal 60° beam angle provides good beam steering and focusing performance for 45° to 70° beam angles. The large active apertures allow the use of highly focused beams for good defect detection and high resolution imaging of weld defects. Application of this system to weld inspections has verified that good defect detection and imaging is possible. In addition, operation with SH waves has proven to provide improved detection of lack of fusion at the cap and root of the weld for certain weld geometries. The system has also been used to demonstrate the inspection of submerged metal arc welds while welding.

  20. Design considerations for a large aperture high field superconducting dipole

    SciTech Connect

    Harfoush, F.; Ankenbrandt, C.; Harrison, M.; Kerby, J.; Koepke, K.; Mantsch, P.; Nicol, T.; Riddiford, A.; Theilacker, J.

    1989-03-01

    The final phase of the Fermilab upgrade proposal calls for a new ring of superconducting magnets to be placed in the existing Main Accelerator tunnel. The goal of this design study is to specify a high field dipole (HFD) that is capable of supporting fixed target operation (ramping, resonant extraction) at a field of 6.6T (1.5 Tev) and colliding beam physics at 8.0T (1.8 Tev). The magnetic field quality at high field is set by the large amplitude orbits associated with resonant extraction. The field quality must therefore be at least as good as the existing Tevatron magnets which fulfill these criteria. The high fields and large aperture of this magnet result in large forces on the coil and collar assemblies. Therefore, the cold mass design must be able to sustain these forces while providing sufficient cooling to the coils during 4.2 K fixed target operation, and a minimum heat load during 1.8 K collider operation. The design work is still in progress but a cosine-theta, cold-iron dipole with a 70mm inner diameter coil has been tentatively adopted. This report presents details on the conductor and cable parameters, coil cross-section, projected manufacturing tolerances, iron yoke design, and cold mass assembly. 4 refs., 5 figs., 1 tab.

  1. Active Optics for a 16-Meter Advanced Technology Large Aperture Space Telescope

    E-print Network

    Sirianni, Marco

    Active Optics for a 16-Meter Advanced Technology Large Aperture Space Telescope David C. Redding. Unwin, M. Werner Jet Propulsion Laboratory, California Institute of Technology, Pasadena CA, USA 91109-optics Advanced Technology Large Aperture Space Telescope, to be launched by the Ares V Heavy Lift Vehicle

  2. Low mass large aperture vacuum window development at CEBAF

    SciTech Connect

    Keppel, C.

    1995-04-01

    Large aperture low mass vacuum windows are being developed for the HMS (High Momentum Spectrometer) and SOS (Short Orbit Spectrometer) spectrometers in Hall C at CEBAF. Because multiple scattering degrades the performance of a spectrometer it is important that the volume be evacuated and that the entrance and exit windows be as low mass as possible. The material used for such windows must be thin and light enough so as to have minimum effect of the beam, and at the same time, be thick and strong enough to operate reliably and safely. To achieve these goals, composite vacuum windows have been constructed of a thin sheet of Mylar with a reinforcing fabric. Reinforcing fabrics such as Kevlar and Spectra are available with tensile strengths significantly greater than that of Mylar. A thin layer of Myler remains necessary since the fabrics cannot achieve any sort of vacuum seal. The design, fabrication, testing, and operating experience with such composite windows for the Hall C spectrometers will be discussed.

  3. LAGOVirtual: A Collaborative Environment for the Large Aperture GRB Observatory

    E-print Network

    R. Camacho; R. Chacon; G. Diaz; C. Guada; V. Hamar; H. Hoeger; A. Melfo; L. A. Nunez; Y. Perez; C. Quintero; M. Rosales; R. Torrens; the LAGO Collaboration

    2009-12-12

    We present the LAGOVirtual Project: an ongoing project to develop platform to collaborate in the Large Aperture GRB Observatory (LAGO). This continental-wide observatory is devised to detect high energy (around 100 GeV) component of Gamma Ray Bursts, by using the single particle technique in arrays of Water Cherenkov Detectors (WCD) at high mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). This platform will allow LAGO collaboration to share data, and computer resources through its different sites. This environment has the possibility to generate synthetic data by simulating the showers through AIRES application and to store/preserve distributed data files collected by the WCD at the LAGO sites. The present article concerns the implementation of a prototype of LAGO-DR adapting DSpace, with a hierarchical structure (i.e. country, institution, followed by collections that contain the metadata and data files), for the captured/simulated data. This structure was generated by using the community, sub-community, collection, item model; available at the DSpace software. Each member institution-country of the project has the appropriate permissions on the system to publish information (descriptive metadata and associated data files). The platform can also associate multiple files to each item of data (data from the instruments, graphics, postprocessed-data, etc.).

  4. The geometric distortions correction of uncooled large-sized relative aperture infrared imaging system

    Microsoft Academic Search

    Xintian Fan; Qiang Sun; Zhenwu Lu

    2005-01-01

    The geometric distortion of infrared image, which was created by the large-sized relative aperture optical system. It could be corrected by the digital image processing technology. The magnitude of distortion would be enlarged quickly with the enlargement of relative aperture. Though the distortion could not impact on the articulation of the image, it would affect geometric location precision of the

  5. Real and Complex Ray Methods for Large Aperture Systems and Radomes

    Microsoft Academic Search

    Pinchas Dov Einziger

    1982-01-01

    The determination of the far field from the near field in large aperture systems constitutes a major problem in high-frequency antenna and diffraction theory. The aperture field may arise either from a directly specified illumination or it may be generated by an initially confined primary field after transmission through a radome cover. While the geometrical theory of diffraction provides a

  6. The use of a large-aperture radio system for meteor studies

    Microsoft Academic Search

    R. W. Herring; P. A. Forsyth

    1980-01-01

    A large sampled-aperture antenna array has been used to investigate the structure of the radio wave field scattered by meteor trails. The experiment measured the phase and amplitude of the radio waves in the frequency range 20 to 30 MHz at 58 points distributed over an aperture of almost 1.2 km. The temporal changes in the structure of the scattered

  7. Time-gated ballistic imaging using a large aperture switching beam.

    PubMed

    Mathieu, Florian; Reddemann, Manuel A; Palmer, Johannes; Kneer, Reinhold

    2014-03-24

    Ballistic imaging commonly denotes the formation of line-of-sight shadowgraphs through turbid media by suppression of multiply scattered photons. The technique relies on a femtosecond laser acting as light source for the images and as switch for an optical Kerr gate that separates ballistic photons from multiply scattered ones. The achievable image resolution is one major limitation for the investigation of small objects. In this study, practical influences on the optical Kerr gate and image quality are discussed theoretically and experimentally applying a switching beam with large aperture (D = 19 mm). It is shown how switching pulse energy and synchronization of switching and imaging pulse in the Kerr cell influence the gate's transmission. Image quality of ballistic imaging and standard shadowgraphy is evaluated and compared, showing that the present ballistic imaging setup is advantageous for optical densities in the range of 8 < OD < 13. Owing to the spatial transmission characteristics of the optical Kerr gate, a rectangular aperture stop is formed, which leads to different resolution limits for vertical and horizontal structures in the object. Furthermore, it is reported how to convert the ballistic imaging setup into a schlieren-type system with an optical schlieren edge. PMID:24664055

  8. Experimental investigation of optical breakdown using nanosecond 532-nm and 1064-nm laser pulses delivered at high numerical aperture

    NASA Astrophysics Data System (ADS)

    Guerra, Arnold, III; Venugopalan, Vasan; Nahen, Kester; Vogel, Alfred

    2001-05-01

    We have conducted time-resolved studies of optical breakdown produced by the irradiation of water using 6 ns Nd:YAG laser pulses of 1064 nm and 532 nm wavelength focused at a numerical aperture of NA=0.9. We determined pulse energy threshold values for plasma formation to be 1.89 (mu) J and 18.3 (mu) J for 532 and 1064 nm irradiation, respectively. These energy thresholds correspond to irradiance thresholds of 0.77 x 109 W/mm2 for 532 nm irradiation and 1.87 x 109 W/mm2 for 1064 nm irradiation. For pulse energies 1x, 2x, 5x, and 10x above threshold, we determined the length of the laser induced plasma, the propagation speed and peak pressures of the emitted shock wave, and the mechanical energy dissipated by subsequent cavitation bubble formation, growth and collapse. This analysis demonstrates that both the breakdown threshold as well as the conversion efficiency of the incident laser energy into mechanical energy is smaller for irradiation at 532 nm than for 1064 nm. These results are consistent with laser parameters employed for a variety of nanosecond pulsed micro irradiation procedures using 1064 nm and 532 nm radiation focused by microscope objectives with large numerical apertures (NA >0.8). These results suggest that laser- induced breakdown is the primary mechanism that drives a variety of cellular micro manipulation techniques which employ nanosecond visible and near-infrared laser pulses.

  9. The scaling relationship between telescope cost and aperture size for very large telescopes

    NASA Technical Reports Server (NTRS)

    van Belle, Gerard T.; Meinel, Aden Baker; Meinel, Marjorie Pettit

    2004-01-01

    Cost data for ground-based telescopes of the last century are analyzed for trends in the relationship between aperture size and cost. We find that for apertures built prior to 1980, costs scaled as aperture size to the 2.8 power, which is consistent with the precious finding of Meinel (1978). After 1980, 'traditional' monolithic mirror telescope costs have scaled as aperture to the 2.5 power. The large multiple mirror telescopes built or in construction during this time period (Keck, LBT, GTC) appear to deviate from this relationship with significant cost savings as a result, although it is unclear what power law such structures follow. We discuss the implications of the current cost-aperture size data on the proposed large telescope projects of the next ten to twenty years. Structures that naturally tend towards the 2.0 power in the cost-aperture relationship will be the favorable choice for future extremely large apertures; out expectation is that space-based structures will ultimately gain economic advantage over ground-based ones.

  10. CAMERA: a compact, automated, laser adaptive optics system for small aperture telescopes

    NASA Astrophysics Data System (ADS)

    Britton, Matthew; Velur, Viswa; Law, Nick; Choi, Philip; Penprase, Bryan E.

    2008-07-01

    CAMERA is an autonomous laser guide star adaptive optics system designed for small aperture telescopes. This system is intended to be mounted permanently on such a telescope to provide large amounts of flexibly scheduled observing time, delivering high angular resolution imagery in the visible and near infrared. The design employs a Shack Hartmann wavefront sensor, a 12x12 actuator MEMS device for high order wavefront compensation, and a solid state 355nm ND:YAG laser to generate a guide star. Commercial CCD and InGaAs detectors provide coverage in the visible and near infrared. CAMERA operates by selecting targets from a queue populated by users and executing these observations autonomously. This robotic system is targeted towards applications that are diffcult to address using classical observing strategies: surveys of very large target lists, recurrently scheduled observations, and rapid response followup of transient objects. This system has been designed and costed, and a lab testbed has been developed to evaluate key components and validate autonomous operations.

  11. Theoretical model to suppress parasitic lasing in large-aperture Ti:sapphire amplifiers using a temporal dual-pulse pump

    NASA Astrophysics Data System (ADS)

    Chu, Yuxi; Liang, Xiaoyan; Yu, Lianghong; Xu, Lu; Li, Ruxin; Xu, Zhizhan

    2014-05-01

    Transverse parasitic lasing (PL) in large-aperture Ti:sapphire (Ti:S) crystals is a critical factor that limits the energy achievable with the chirped-pulse amplification (CPA) technique. We propose a method to suppress PL effects in large-aperture Ti:S amplifiers by using a temporal dual-pulse pump. Theoretical simulations based on the experimental parameters in 2.0 PW Ti:S laser system are performed to predict the transverse gain as a function of pumping time and output energy. By optimizing the temporal profile of the pump beam as well as the time delay between the input seed and pump pulses, we can minimize PL effects in Ti:S crystals. This method is applicable to larger-aperture Ti:S crystals pumped at higher pump fluence and energy, and is potential to develop a ~10 PW laser system.

  12. Research on 2x1 plasma electrode electro-optical switch with large aperture

    Microsoft Academic Search

    Xiong Jun Zhang; Kui Xing Zheng; B. Feng; D. S. Wu; J. P. Lu; X. L. Tian; F. Jin; Zhan Sui; Xiaofeng Wei; Xiaomin Zhang

    2005-01-01

    In conceptual design of the prototype for SG-III facility, a full aperture electro-optical switch was placed between the cavity mirror and the main amplifier to isolate the reflected beams. The beam on the cavity mirror is 240mm×240mm square. Pockells cells of conversional design with coaxial ring electrodes can not scale to such large square aperture. In the 1980s, a plasma

  13. Large-aperture, tapered fiber-coupled, 10-kHz particle-image velocimetry.

    PubMed

    Hsu, Paul S; Roy, Sukesh; Jiang, Naibo; Gord, James R

    2013-02-11

    We demonstrate the design and implementation of a fiber-optic beam-delivery system using a large-aperture, tapered step-index fiber for high-speed particle-image velocimetry (PIV) in turbulent combustion flows. The tapered fiber in conjunction with a diffractive-optical-element (DOE) fiber-optic coupler significantly increases the damage threshold of the fiber, enabling fiber-optic beam delivery of sufficient nanosecond, 532-nm, laser pulse energy for high-speed PIV measurements. The fiber successfully transmits 1-kHz and 10-kHz laser pulses with energies of 5.3 mJ and 2 mJ, respectively, for more than 25 min without any indication of damage. It is experimentally demonstrated that the tapered fiber possesses the high coupling efficiency (~80%) and moderate beam quality for PIV. Additionally, the nearly uniform output-beam profile exiting the fiber is ideal for PIV applications. Comparative PIV measurements are made using a conventionally (bulk-optic) delivered light sheet, and a similar order of measurement accuracy is obtained with and without fiber coupling. Effective use of fiber-coupled, 10-kHz PIV is demonstrated for instantaneous 2D velocity-field measurements in turbulent reacting flows. Proof-of-concept measurements show significant promise for the performance of fiber-coupled, high-speed PIV using a tapered optical fiber in harsh laser-diagnostic environments such as those encountered in gas-turbine test beds and the cylinder of a combustion engine. PMID:23481818

  14. Laser fabrication of micron-size apertures for electron beam microcolumns

    NASA Astrophysics Data System (ADS)

    Ahn, S. J.; Kim, D. W.; Kim, H. S.; Cho, K. H.; Choi, S. S.

    For electron beam nanolithography and scanning electron microscopy applications, an electrostatic electron lens system called a microcolumn must be assembled. In order to reduce aberrations, laser drilling of the assembled microcolumn system should be highly beneficial. We have drilled micron-size apertures on silicon substrates including molybdenum and tantalum using a 1.064 ?m Nd:YAG laser. In this work, a layer-by-layer evaporation technique using multiple pulse treatment (MPT) is employed in order to minimize melting of the crater wall and maximize the evaporation of the bottom layer of the crater. The machining conditions of an Nd:YAG laser pulsed in the TEM00 mode for ceramic, silicon, and molybdenum diaphragms are optimized. We obtain micron-size apertures for electron beam microcolumn applications such as electron lenses.

  15. Guide lines for the design of very large aperture quadrupole magnets

    Microsoft Academic Search

    A. Daeel; J. P. Jorda; F. Kircher; C. Mayri

    1996-01-01

    Very large aperture quadrupole magnets have been recently considered as possible spectrometers on high energy colliders. The interesting characteristics are zero field on beam axis, low fields at small angles, transverse field at large angles. Dimension range is 1 m to 5 m for clear bore and 2 m to 8 m for length; typical maximum field is 2.5 T.

  16. Large aperture deformable mirror with a transferred single-crystal silicon membrane actuated using large-stroke PZT Unimorph Actuators

    NASA Technical Reports Server (NTRS)

    Hishinumat, Yoshikazu; Yang, Eui - Hyeok (EH)

    2005-01-01

    We have demonstrated a large aperture (50 mm x 50 mm) continuous membrane deformable mirror (DM) with a large-stroke piezoelectric unimorph actuator array. The DM consists of a continuous, large aperture, silicon membrane 'transferred' in its entirety onto a 20 x 20 piezoelectric unimorph actuator array. A PZT unimorph actuator, 2.5 mm in diameter with optimized PZT/Si thickness and design showed a deflection of 5.7 [m at 20V. An assembled DM showed an operating frequency bandwidth of 30 kHz and influence function of approximately 30%.

  17. Large-aperture spectral radiance calibration source for ultraviolet remote sensing instruments

    NASA Astrophysics Data System (ADS)

    Heath, Donald F.

    2003-04-01

    Radiometric calibration of large aperture space-borne remote sensing instruments designed to measure atmospheric radiances in the 250 to 400 nm wavelength range is difficult. Historically the spectral radiance calibrations of these instruments have been derived from aperture radiances of integrating spheres illuminated internally by quartz-tungsten-halogen (QTH) lamps. Typical aperture radiances increase by a factor of 400 from 250 to 400 nm and by an additional factor of 10 from 400 to 900 nm. The characteristics of the aperture radiances of 51 cm diameter Spectralon sphere illuminated by an external xenon arc and by internal QTH lamps have been measured. The aperture radiance of the sphere illuminated externally by the xenon arc is 15 times larger at 250 nm than the radiance from internal QTH lamp illumination. The radiometric stability and the aperture uniformity at 290 nm from the two types of illumination are comparable. These measurements have been made with a calibration transfer standard spectroradiometer using 14 narrow ion-assisted deposition filters covering the wavelength region from 250 to 920 nm. The calibration scale of the transfer radiometer is tied to a NIST 1000 W FEL lamp spectral irradiance standard.

  18. Synthetic aperture laser optical feedback imaging using a translational scanning with galvanometric mirrors.

    PubMed

    Glastre, Wilfried; Jacquin, Olivier; Hugon, Olivier; Guillet de Chatellus, Hugues; Lacot, Eric

    2012-08-01

    In this paper we present an experimental setup based on laser optical feedback imaging (LOFI) and on synthetic aperture with translational scanning by galvanometric mirrors for the purpose of making deep and resolved images through scattering media. We provide real two-dimensional optical synthetic aperture image of a fixed scattering target with a moving aperture and an isotropic resolution. We demonstrate theoretically and experimentally that we can keep microscope resolution beyond the working distance. A photometric balance is made, and we show that the number of photons participating in the final image decreases with the square of the reconstruction distance. This degradation is partially compensated by the high sensitivity of LOFI. PMID:23201879

  19. Measuring parameters of large-aperture crystals used for generating optical harmonics

    SciTech Connect

    Auerbach, J M; English, R E, Jr; Hibbard, R L; Michie, R B; Norton, M A; Perfect, S A; Summers, M D; Wegner, P J

    1999-02-23

    The purpose of this project was to develop tools for understanding the influence of crystal quality and crystal mounting on harmonic-generation efficiency at high irradiance. Measuring the homogeneity of crystals interferometrically, making detailed physics calculations of conversion efficiency, performing finite- element modeling of mounted crystals, and designing a new optical metrology tool were key elements in obtaining that understanding. For this work, we used the following frequency-tripling scheme: type I second- harmonic generation followed by type II sum-frequency mixing of the residual fundamental and the second harmonic light. The doubler was potassium dihydrogen phosphate (KDP), and the tripler was deuterated KDP (KD*P). With this scheme, near-infrared light (1053 nm) can be frequency tripled (to 351 nm) at high efficiency (theoretically >90%) for high irradiance (>3 GW/cm²). Spatial variations in the birefringence of the large crystals studied here (37 to 41 cm square by about 1 cm thick) imply that the ideal phase-matching orientation of the crystal with respect to the incident laser beam varies across the crystal. We have shown that phase-measuring interferometry can be used to measure these spatial variations. We observed transmitted wavefront differences between orthogonally polarized interferograms of {lambda}/50 to {lambda}/100, which correspond to index variations of order 10-6. On some plates that we measured, the standard deviation of angular errors is 22-23 µrad; this corresponds to a 1% reduction in efficiency. Because these conversion crystals are relatively thin, their surfaces are not flat (deviate by k2.5 urn from flat). A crystal is mounted against a precision-machined surface that supports the crystal on four edges. This mounting surface is not flat either (deviates by +2.5 µm from flat). A retaining flange presses a compliant element against the crystal. The load thus applied near the edges of the crystal surface holds it in place. We performed detailed finite-element modeling to predict the resulting shape of the mounted crystal. The prediction agreed with measurements of mounted crystals. We computed the physics of the frequency-conversion process to better quantify the effects on efficiency of variation in the crystal? s axis, changes in the shape of the crystal, and mounting-induced stress. We were able to accurately predict the frequency-conversion performance of 37-cm square crystals on Beamlet, a one-beam scientific prototype of the NIF laser architecture, using interferometric measurements of the mounted crystals and the model. In a 2{omega} measurement campaign, the model predicted 64.9% conversion efficiency; 64.1% was observed. When detuned by 640 µrad, the model and measurement agreement is even better (both were 10.4%). Finally, we completed the design and initial testing of a new optical metrology tool to measure the spatial variation of frequency conversion. This system employs a high-power subaperture beam from a commercial laser oscillator and rod amplifier. The beam interrogates the crystal? s aperture by moving the crystal horizontally on a translation stage and translating the laser beam vertically on an optical periscope. Precision alignment is maintained by means of a full-aperture reference mirror, a precision-machined surface on the crystal mount, and autocollimators (the goal for angular errors is 10 µrad). The autocollimators track the mounting angle of the crystal and the direction of the laser beam with respect to the reference mirror. The conversion efficiency can be directly measured by recording l{omega}, 2{omega}, 3{omega} energy levels during the scan and by rocking (i.e., tilting) the crystal mount over an angular range.

  20. High-resolution photoacoustic vascular imaging in vivo using a large-aperture acoustic lens

    Microsoft Academic Search

    Konstantin Maslov; Lihong V. Wang

    2005-01-01

    Reflection-mode photoacoustic microscopy with dark-field laser pulse illumination and high frequency ultrasonic detection is used to non-invasively image blood vessels in the skin in vivo. Dark-field illumination minimizes the interference caused by strong photoacoustic signals from superficial structures. A high numerical-aperture acoustic lens provides high lateral resolution, 45-120 micrometers in this system while a broadband ultrasonic detection system provides high

  1. Synthesis of a large communications aperture using small antennas

    NASA Technical Reports Server (NTRS)

    Resch, George M.; Cwik, T. W.; Jamnejad, V.; Logan, R. T.; Miller, R. B.; Rogstad, Dave H.

    1994-01-01

    In this report we compare the cost of an array of small antennas to that of a single large antenna assuming both the array and single large antenna have equal performance and availability. The single large antenna is taken to be one of the 70-m antennas of the Deep Space Network. The cost of the array is estimated as a function of the array element diameter for three different values of system noise temperature corresponding to three different packaging schemes for the first amplifier. Array elements are taken to be fully steerable paraboloids and their cost estimates were obtained from commercial vendors. Array loss mechanisms and calibration problems are discussed. For array elements in the range 3 - 35 m there is no minimum in the cost versus diameter curve for the three system temperatures that were studied.

  2. Full aperture backscatter station imager diagnostics system for far-field imaging of laser plasma instabilities on Nova

    Microsoft Academic Search

    Mark D. Wilke; Juan C. Ferna´ndez; Ralph R. Berggren; Richard F. Horton; David S. Montgomery; James A. Faulkner; Larry D. Looney; John R. Jimerson

    1997-01-01

    In ICF, the understanding of laser plasma scattering processes is essential for laser target coupling and for controlling the symmetry of indirect drive implosions. The existing Nova full aperture backscatter station has been useful in understanding laser plasma instabilities occurring in hohlraums by measuring the quantity, spectral distribution, and near-field spatial distributions of Brillouin and more recently Raman backscatter. Equally

  3. Modeling the nonlinear dynamics of wide aperture semiconductor lasers and amplifiers

    SciTech Connect

    Moloney, J.V.; Indik, R.; White, J.K.; Ru, P. [Univ. of Arizona, Tucson, AZ (United States). Dept. of Mathematics; Koch, S.W. [Philipps Univ. Marburg, Marburg an der Lahn (Germany); Chow, W.W. [Sandia National Labs., Albuquerque, NM (United States)

    1994-12-31

    Issues relating to modeling the full spatiotemporal dynamics of wide aperture semiconductor lasers and amplifiers are discussed. Included in the discussion are the limitations of the usual beam propagation approach, characteristics of the many-body light-semiconductor material interaction, spurious nonphysical instabilities which mimic numerical grid oscillations and novel subpicosecond pulse reshaping and compression effects. An explicit simulation is presented for a flared amplifier structure and the results are compared with those using a linear gain model.

  4. Using GPS to Synthesize A Large Antenna Aperture When The Elements Are Mobile

    E-print Network

    Stanford University

    Using GPS to Synthesize A Large Antenna Aperture When The Elements Are Mobile Shau-Shiun Jan, Per antenna elements, where the Global Positioning System (GPS) is used to estimate the current location. With this information, a central algorithm can control the phase of the radio signal radiated from each element so

  5. Advanced Technology Large-Aperture Space Telescope (ATLAST) Appendix C: ATLAST-8m Design & Engineering Study

    E-print Network

    Sirianni, Marco

    & Engineering Study The ATLAST-8m engineering study was lead by NASA MFSC with guidance from the Space Telescope ! #12;ATLAST 8-m Design & Engineering Study 2 TABLE OF CONTENTS 1.0 ATLAST-8m Mission ConceptAdvanced Technology Large-Aperture Space Telescope (ATLAST) 1 Appendix C: ATLAST-8m Design

  6. Model-based processing for a large aperture array

    Microsoft Academic Search

    J. V. Candy; E. J. Sullivan

    1994-01-01

    A model-based approach to solve a deep water ocean acoustic signal processing problem based on a state-space representation of the normal-mode propagation model is developed. The design of a model-based processor (MBP) for signal enhancement employing an array consisting of a large number of sensors for a deep ocean surveillance operation is discussed. The processor provides enhanced estimates of the

  7. Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

    NASA Technical Reports Server (NTRS)

    Farley, Rodger E.; Quinn, David A.

    2004-01-01

    With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 3 - 4 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

  8. Tethered Formation Configurations: Meeting the Scientific Objectives of Large Aperture and Interferometric Science

    NASA Technical Reports Server (NTRS)

    Farley, Rodger E.; Quinn, David A.; Brodeur, Stephen J. (Technical Monitor)

    2001-01-01

    With the success of the Hubble Space Telescope, it has become apparent that new frontiers of science and discovery are made every time an improvement in imaging resolution is made. For the HST working primarily in the visible and near-visible spectrum, this meant designing, building, and launching a primary mirror approximately three meters in diameter. Conventional thinking tells us that accomplishing a comparable improvement in resolution at longer wavelengths for Earth and Space Science applications requires a corresponding increase in the size of the primary mirror. For wavelengths in the sub-millimeter range, a very large telescope with an effective aperture in excess of one kilometer in diameter would be needed to obtain high quality angular resolution. Realistically a single aperture this large is practically impossible. Fortunately such large apertures can be constructed synthetically. Possibly as few as three 34 meter diameter mirrors flying in precision formation could be used to collect light at these longer wavelengths permitting not only very large virtual aperture science to be carried out, but high-resolution interferometry as well. To ensure the longest possible mission duration, a system of tethered spacecraft will be needed to mitigate the need for a great deal of propellant. A spin-stabilized, tethered formation will likely meet these requirements. Several configurations have been proposed which possibly meet the needs of the Space Science community. This paper discusses two of them, weighing the relative pros and cons of each concept. The ultimate goal being to settle on a configuration which combines the best features of structure, tethers, and formation flying to meet the ambitious requirements necessary to make future large synthetic aperture and interferometric science missions successful.

  9. The influence of window thermal conductivity on the temperature distribution of the ADP crystal with large aperture

    NASA Astrophysics Data System (ADS)

    Sun, Fuzhong; Zhang, Peng; Xiang, Yong; Lu, Lihua; Su, Ruifeng

    2015-06-01

    Motivated by the need of achieving the high frequency conversion efficiency of the laser beam with large diameter in the non-critical phase matching, a temperature control scheme of ADP crystal with large aperture was proposed. In this paper, in order to obtain the influence of the window thermal conductivity on the temperature distribution of ADP crystal, four different window materials, the thermal conductivities of which are different orders of magnitude, were proposed and analyzed by using the finite volume method (FVM) and experiments. The temperature distributions and temperature gradients of ADP crystal in the temperature control scheme with different window materials were discussed, and the optimal fourth harmonic generation (FHG) conversion efficiencies were obtained in different optics regions. Finally, the requirement of the window material thermal conductivity was proposed in order to obtain the high frequency conversion efficiency.

  10. Large Aperture "Photon Bucket" Optical Receiver Performance in High Background Environments

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor A.; Hoppe, D.

    2011-01-01

    The potential development of large aperture groundbased "photon bucket" optical receivers for deep space communications, with acceptable performance even when pointing close to the sun, is receiving considerable attention. Sunlight scattered by the atmosphere becomes significant at micron wavelengths when pointing to a few degrees from the sun, even with the narrowest bandwidth optical filters. In addition, high quality optical apertures in the 10-30 meter range are costly and difficult to build with accurate surfaces to ensure narrow fields-of-view (FOV). One approach currently under consideration is to polish the aluminum reflector panels of large 34-meter microwave antennas to high reflectance, and accept the relatively large FOV generated by state-of-the-art polished aluminum panels with rms surface accuracies on the order of a few microns, corresponding to several-hundred micro-radian FOV, hence generating centimeter-diameter focused spots at the Cassegrain focus of 34-meter antennas. Assuming pulse-position modulation (PPM) and Poisson-distributed photon-counting detection, a "polished panel" photon-bucket receiver with large FOV will collect hundreds of background photons per PPM slot, along with comparable signal photons due to its large aperture. It is demonstrated that communications performance in terms of PPM symbol-error probability in high-background high-signal environments depends more strongly on signal than on background photons, implying that large increases in background energy can be compensated by a disproportionally small increase in signal energy. This surprising result suggests that large optical apertures with relatively poor surface quality may nevertheless provide acceptable performance for deep-space optical communications, potentially enabling the construction of cost-effective hybrid RF/optical receivers in the future.

  11. Split-aperture laser pulse compressor design tolerant to alignment and line-density differences.

    PubMed

    Rushford, Michael C; Britten, Jerald A; Barty, Christopher P J; Jitsuno, Takahisa; Kondo, Kiminori; Miyanaga, Noriaki; Tanaka, Kazuo A; Kodama, Ryosuke; Xu, Guang

    2008-08-15

    We introduce a four-pass laser pulse compressor design based on two grating apertures with two gratings per aperture that is tolerant to some alignment errors and, importantly, to grating-to-grating period variations. Each half-beam samples each grating in a diamond-shaped compressor that is symmetric about a central bisecting plane. For any given grating, the two half-beams impinge on opposite sides of its surface normal. It is shown that the two split beams have no pointing difference from paired gratings with different periods. Furthermore, no phase shift between half-beams is incurred as long as the planes containing a grating line and the surface normal for each grating of the pair are parallel. For grating pairs satisfying this condition, gratings surfaces need not be on the same plane, as changes in the gap between the two can compensate to bring the beams back in phase. PMID:18709127

  12. New multiplexed all solid state pulser for high power wide aperture kinetically enhanced copper vapor laser.

    PubMed

    Ghodke, D V; Muralikrishnan, K; Singh, Bijendra

    2013-11-01

    A novel multiplexed scheme is demonstrated to combine two or more pulsed solid state pulsers of moderate capabilities. Pulse power supply comprising of two solid state pulsers of ~6 kW rating each in multiplexed mode with common magnetic pulse compression stage was demonstrated and optimized for operating with a wide aperture kinetically enhanced copper vapor laser. Using this new configuration, the multiplexed pulsed power supply was capable of operating efficiently at net repetition-rate of ~13 kHz, 12 kW (wall plug average power), 18-20 kV discharge voltage and pulse rise-time of ~80 ns. The laser under multiplexed configuration delivered un-interrupted output power of about ~80 W with scope of further increase in laser output power in excess of 100 W. PMID:24289383

  13. The Advanced Technology Large Aperture Space Telescope (ATLAST): Science Drivers and Technology Developments

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2011-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers and the resulting performance requirements for ATLAST (8 to 16 milliarcsecond angular resolution, diffraction limited imaging at 0.5 m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 m to 2.4 m, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to current generation observatory-class space missions. Keywords: Advanced Technology Large-Aperture Space Telescope (ATLAST); ultraviolet/optical space telescopes; astrophysics; astrobiology; technology development.

  14. Design of an infrared four-mirror optical system with large relative aperture

    NASA Astrophysics Data System (ADS)

    Cong, Bin; Wu, Zheng

    2015-04-01

    Reflective optics is used widely in optical systems for their achromatization, large aperture and lightweight compared with refractive systems. An infrared four-mirror optical system with large relative aperture working in the 7.7?10.3 micron long wavelength infrared band is designed by using four reflective mirrors. The design principle, design results are described in this paper. The system has a circinal wide field of view with 1.5°×1.5°. The MTF of the system is diffraction-limited and the distortion is less than 1.0%. The ratio of focal length to total length is about 1/1.04,so the structure of the system is compact. The image quality is evaluated for each field, which shows that the design makes a good system with high image quality.

  15. Estimation of heat and momentum fluxes over complex terrain using a large aperture scintillometer

    Microsoft Academic Search

    A. Chehbouni; C. Watts; J.-P. Lagouarde; Y. H. Kerr; J.-C. Rodriguez; J.-M. Bonnefond; F. Santiago; G. Dedieu; D. C. Goodrich; C. Unkrich

    2000-01-01

    A comprehensive experimental plan has been designed to further investigate the potential and the limitations associated with the use of a large aperture scintillometer (LAS) to infer path average sensible and momentum fluxes over complex surfaces as part of the Semi-Arid Land–Surface–Atmosphere (SALSA) Program. The complexity of the terrain is associated with the type and the cover of the vegetation

  16. Large-aperture MOEMS Fabry-Perot interferometer for miniaturized spectral imagers

    NASA Astrophysics Data System (ADS)

    Rissanen, Anna; Langner, Andreas; Viherkanto, Kai; Mannila, Rami

    2015-02-01

    VTT's optical MEMS Fabry-Perot interferometers (FPIs) are tunable optical filters, which enable miniaturization of spectral imagers into small, mass producible hand-held sensors with versatile optical measurement capabilities. FPI technology has also created a basis for various hyperspectral imaging instruments, ranging from nanosatellites, environmental sensing and precision agriculture with UAVs to instruments for skin cancer detection. Until now, these application demonstrations have been mostly realized with piezo-actuated FPIs fabricated by non-monolithical assembly method, suitable for achieving very large optical apertures and with capacity to small-to-medium volumes; however large-volume production of MEMS manufacturing supports the potential for emerging spectral imaging applications also in large-volume applications, such as in consumer/mobile products. Previously reported optical apertures of MEMS FPIs in the visible range have been up to 2 mm in size; this paper presents the design, successful fabrication and characterization of MEMS FPIs for central wavelengths of ? = 500 nm and ? = 650 nm with optical apertures up to 4 mm in diameter. The mirror membranes of the FPI structures consist of ALD (atomic layer deposited) TiO2-Al2O3 ?/4- thin film Bragg reflectors, with the air gap formed by sacrificial polymer etching in O2 plasma. The entire fabrication process is conducted below 150 °C, which makes it possible to monolithically integrate the filter structures on other ICdevices such as detectors. The realized MEMS devices are aimed for nanosatellite space application as breadboard hyperspectral imager demonstrators.

  17. Temporally focused femtosecond laser pulses for low numerical aperture micromachining through optically transparent materials.

    PubMed

    Vitek, Dawn N; Adams, Daniel E; Johnson, Adrea; Tsai, Philbert S; Backus, Sterling; Durfee, Charles G; Kleinfeld, David; Squier, Jeffrey A

    2010-08-16

    Temporal focusing of spatially chirped femtosecond laser pulses overcomes previous limitations for ablating high aspect ratio features with low numerical aperture (NA) beams. Simultaneous spatial and temporal focusing reduces nonlinear interactions, such as self-focusing, prior to the focal plane so that deep (approximately 1 mm) features with parallel sidewalls are ablated at high material removal rates (25 microm(3) per 80 microJ pulse) at 0.04-0.05 NA. This technique is applied to the fabrication of microfluidic devices by ablation through the back surface of thick (6 mm) fused silica substrates. It is also used to ablate bone under aqueous immersion to produce craniotomies. PMID:20721196

  18. Temporally focused femtosecond laser pulses for low numerical aperture micromachining through optically transparent materials

    PubMed Central

    Vitek, Dawn N.; Adams, Daniel E.; Johnson, Adrea; Tsai, Philbert S.; Backus, Sterling; Durfee, Charles G.; Kleinfeld, David; Squier, Jeffrey A.

    2010-01-01

    Temporal focusing of spatially chirped femtosecond laser pulses overcomes previous limitations for ablating high aspect ratio features with low numerical aperture (NA) beams. Simultaneous spatial and temporal focusing reduces nonlinear interactions, such as self-focusing, prior to the focal plane so that deep (~1 mm) features with parallel sidewalls are ablated at high material removal rates (25 µm3 per 80 µJ pulse) at 0.04-0.05 NA. This technique is applied to the fabrication of microfluidic devices by ablation through the back surface of thick (6 mm) fused silica substrates. It is also used to ablate bone under aqueous immersion to produce craniotomies. PMID:20721196

  19. Research on the support structure of the primary mirror of large-aperture telescope

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Zhang, Jingxu

    2007-12-01

    Large-aperture telescope can be used in surveying battlefield, researching landform, searching object, real-time monitoring, imaging, detecting and identifying spatial targets and so on. A large-aperture telescope for achieving high resolution power is designed to monitor spatial target and image in real time. Real-time monitoring plays an important role in military conflicts. The orbit parameter of object, quantity, geometrical shape parameter and so on can be obtained by detect spatial target. With the development of optical technology, people require larger aperture in optics-electronic (O-E) system. By increasing optical aperture, the ability of collecting light and resolution power in the system can be enhanced. But the support structure of the primary mirror of large-aperture telescope will be a very difficult problem. With the increase of primary mirror aperture, the weight of the primary mirror will become larger than before. The root mean square (rms) of the primary mirror is affected by many factors, such as deadweight, deformation of heat, environment and so on. Due to the primary mirror of telescope is an important component of telescope system. By reducing the weight of primary mirror, precision of the system is ensured. During the designing phase, one can consider the supporting project of the primary mirror synthetically and analyze it roundly according to technical requirement of optical system and the effect factors. The final structural design can be reasonable. In an astronomical telescope, the surface of reflector is an important part for collecting dark radiation of celestial bodies. Its surface shape will have an effect on collecting efficiency of telescope radiant energy directly. So the rms must be very high. Optical system of large aperture, small wavelength and small focus can receive maximal light intensity. For ground-based optical astronomical telescope, the design proposed in the paper can satisfy the requirement of the possible minimum atmosphere seeing at astronomical observatory site and exert the use efficiency of the telescope adequately. So the accuracy of the traditional surface of reflector can assure that 90% of all the light energy can be focused on within the angle diameter range of the minimum atmosphere seeing, then 100% of light energy should be focused on the angle diameter range of minimum atmosphere seeing. Because the rms of mirror is very high, precise surface machining and accurate the support of mirror are very important tasks during designing and manufacturing the telescope. In the paper, various support techniques of a large-aperture telescope primary mirror are discussed and a 3.5 meter telescope system at the Starfire Optical Range (SOR) overviewed simply, which was operated by the Directed Energy Directorate of the Air Force Research Laboratory, Kirtland AFB, NM, USA from the ground-based O-E system for the observations of spatial target. We also analyze Theoretical elastic deformation of the Steward Observatory 2.3 meter mirror is analyzed.

  20. Near-field modulation of laser diode emissions by an aperture probe of near-field optical microscope

    Microsoft Academic Search

    Akihiro Tomioka; Atsushi Fujimoto; Shinji Kinoshita; Wataru Susaki

    2008-01-01

    In situ emission profiles of AlGaInP multiple quantum well laser diodes (LDs) observed by a near-field scanning optical microscope (NSOM) probe with an intentionally enlarged aperture shows a single broad elliptic profile, whereas the detected wavelength hops among those of the longitudinal multimodes observed in the far-field. This hopping suggests the near-field coupling between the aperture and the LD cavity,

  1. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Montgomery, Edward E.; Lindner, Jeff

    2000-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include an improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  2. Recent Enhancements of the Phased Array Mirror Extendible Large Aperture (PAMELA) Telescope Testbed at MSFC

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Burdine, Robert (Technical Monitor)

    2001-01-01

    Recent incremental upgrades to the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope testbed have enabled the demonstration of phasing (with a monochromatic source) of clusters of primary mirror segments down to the diffraction limit. PAMELA upgrades include in improved Shack-Hartmann wavefront sensor, passive viscoelastic damping treatments for the voice-coil actuators, mechanical improvement of mirror surface figures, and optical bench baffling. This report summarizes the recent PAMELA upgrades, discusses the lessons learned, and presents a status of this unique testbed for wavefront sensing and control. The Marshall Space Flight Center acquired the Phased Array Mirror Extendible Large Aperture (PAMELA) telescope in 1993 after Kaman Aerospace was unable to complete integration and testing under the limited SDIO and DARPA funding. The PAMELA is a 36-segment, half-meter aperture, adaptive telescope which utilizes a Shack-Hartmann wavefront sensor, inductive coil edge sensors, voice coil actuators, imaging CCD cameras and interferometry for figure alignment, wavefront sensing and control. MSFC originally obtained the PAMELA to supplement its research in the interactions of control systems with flexible structures. In August 1994, complete tip, tilt and piston control was successfully demonstrated using the Shack-Hartmann wavefront sensor and the inductive edge sensors.

  3. ATLAST-9.2m: a Large-Aperture Deployable Space Telescope

    NASA Technical Reports Server (NTRS)

    Oergerle, William; Feinberg, Lee D.; Purves, Lloyd R.; Hyde, T. Tupper; Thronson, Harley A.; Townsend, Jacqueline A.; Postman, Marc; Bolear, Matthew R.; Budinoff, Jason G.; Dean, Bruce H.; Clampin, Mark C.; Ebbets, Dennis C.; Gong, Qian; Gull, Theodore R.; Howard, Joseph M.; Jones, Andrew L.; Lyon, Richard G.; Pasquale, Bert A.; Perrygo, Charles; Smith, Jeffrey S.; Thompson, Patrick L.; Woodgate, Bruce E.

    2010-01-01

    We present results of a study of a deployable version of the Advanced Technology Large-Aperture Space Telescope (ATLAST), designed to operate in a Sun-Earth L2 orbit. The primary mirror of the segmented 9.2-meter aperture has 36 hexagonal 1.315 m (flat to flat) glass mirrors. The architecture and folding of the telescope is similar to JWST, allowing it to fit into the 6.5 m fairing of a modest upgrade to the Delta-IV Heavy version of the Evolved Expendable Launch Vehicle (EELV). We discuss the overall observatory design, optical design, instruments, stray light, wavefront sensing and control, pointing and thermal control, and in-space servicing options.

  4. A Full Aperture Backscattering Light Diagnostic System Installed on the Shenguang-III Prototype Laser Facility

    NASA Astrophysics Data System (ADS)

    Xu, Tao; Mei, Yu; Wei, Huiyue; Peng, Xiaoshi; Wang, Feng; Yang, Dong; Liu, Shenye; Yan, Yadong

    2014-06-01

    A full aperture backscattering light diagnostic system (FABLDS) implemented on the Shen Guang-III Prototype Laser Facility is described in the paper. FABLDS measures both stimulated brillouin scattering (SBS) and stimulated Raman scattering (SRS) with a series of optical detectors. Energy sensors record the integrated energy, and streak cameras coupled with spectrometers measure the temporal spectrum of the backscattering light. This paper provides an overview of the FABLDS and detailed descriptions of the optical path. Special components, including off-axis parabolic mirror, spatial filter and optical light filters, are incorporated along the beam path for purifying the scattering light. Several hohlraum targets were employed, including C5H12 gas-filled targets and empty targets in the experiments. Results presented in the paper indicate that the fraction of backscatter light has been obviously shrinked when the laser is smoothed by continuous phase plates (CPP).

  5. Current Aperture III-Nitride Edge-emitting Blue Laser Diode

    NASA Astrophysics Data System (ADS)

    Megalini, Ludovico

    This work presents the first Nitride non polar Current Aperture Edge Emitting Blue Laser Diode (CA-LD) fabricated using the Photo-Electro-Chemical Etching (PECE) technique. The main features of this design are represented by the deep etching of the laser diode ridge through the active region, the controlled etching of the active region by PECE and the increase of the p-contact area with respect to the active region area. Preliminary experiments manifest that CA-LD has similar threshold current density, slope efficiency and peak output power of the more commonly used shallow etch ridge design and it has also shown a reduction in the series resistance down to ˜40% with respect to the shallow-etch LDs indicating the potential of the CA-LD design in high-efficient, high-power, high-frequency LD applications.

  6. Design and fabrication of sub-wavelength annular apertures for femtosecond laser machining

    NASA Astrophysics Data System (ADS)

    Hsu, Kuan-Yu; Tung, Yen-Chun; Chung, Ming-Han; Lee, Chih-Kung

    2015-03-01

    Many research teams have begun pursuing optical micromachining technology in recent years due to its associated noncontact and fast speed characteristics. However, the focal spot sizes and the depth of focus (DOF) strongly influenced the design requirements of the micromachining system. The focal spot size determines the minimum features can be fabricated, which is inversely proportional to the DOF. That is, smaller focal spot size led to shorter DOF. However, the DOF of the emitted visible or near-infrared light beam is typically limited to tens of nanometers for traditional optic system. The disadvantages of using nanosecond laser for micromachining such as burrs formation and surface roughness were found to further influence the accuracy of machined surfaces. To alleviate all of the above-mentioned problems, sub-wavelength annular aperture (SAA) illuminated with 780 nm femtosecond laser were integrated to develop the new laser micromachining system presented in this paper. We first optimized the parameters for high transmittance associated with the SAA structure for the 780 nm femtosecond laser used by adopting the finite difference time domain simulations method. A lateral microscope was modified from a traditional microscope to facilitate the measurement of the emitted light beam optical energy distribution. To verify the newly developed system performance the femtosecond laser was used to illuminate the SAA fabricated on the metallic film to produce the Bessel light beam so as to perform micromachining and process on silicon, PCB board and glass. Experimental results were found to match the original system design goals reasonably well.

  7. Study on the stitching interferometry for the surface profile measurement of a large aperture component

    NASA Astrophysics Data System (ADS)

    Zhao, Weirui; Qiu, Lirong; Zhao, Weiqian; Cao, Genrui

    2014-05-01

    The stitching interferometry for the surface profile measurement of a large aperture component is studied. To analyze the overlapping region interferogram of the adjacent subapertures with Scale Invariant Feature Transform(SIFT) algorithm, the stitching parameters of the adjacent subapertures and then overall surface information of the tested component can be obtained. SIFT algorithm of subaperture positioning, interferogram processing, phase unwrapping, Zernike polynomials wavefront fitting and subaperture wavefront stitching programs are written. A principle experiment has been carried out. Compared with the measurement results between the stitching interferometry and full caliber testing, the deviation of RMS is less than 2nm.

  8. Compact large-aperture Fabry-Perot interferometer modules for gas spectroscopy at mid-IR

    NASA Astrophysics Data System (ADS)

    Kantojärvi, Uula; Varpula, Aapo; Antila, Tapani; Holmlund, Christer; Mäkynen, Jussi; Näsilä, Antti; Mannila, Rami; Rissanen, Anna; Antila, Jarkko; Disch, Rolf J.; Waldmann, Torsten A.

    2014-03-01

    VTT has developed Fabry-Pérot Interferometers (FPI) for visible and infrared wavelengths since 90's. Here we present two new platforms for mid-infrared gas spectroscopy having a large optical aperture to provide high optical throughput but still enabling miniaturized instrument size. First platform is a tunable filter that replaces a traditional filter wheel, which operates between wavelengths of 4-5 um. Second platform is for correlation spectroscopy where the interferometer provides a comb-like transmission pattern mimicking absorption of diatomic molecules at the wavelength range of 4.7-4.8 um. The Bragg mirrors have 2-4 thin layers of polysilicon and silicon oxide.

  9. Engineering Specification for Large-aperture UVO Space Telescopes Derived from Science Requirements

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip; Arnold, William; Bevan, Ryan M.; Smith, W. Scott.; Kirk, Charles S.; Postman, Mark

    2013-01-01

    An advanced large aperture UV/optical UVO space telescope is required for the next generation of astrophysics and exoplanet science. The science requirements of proposed exoplanet and astrophysics missions were used to determine the encircled energy, point spread function stability and thermal environment requirements. These requirements then determine the optical wavefront specification for potential telescope assemblies which can fit inside current and planned launch vehicles. The optical wavefront specification becomes the top level of the error budget that is split into various sources that control the structural, thermal and optical design.

  10. Spacecraft Conceptual Design for the 8-Meter Advanced Technology Large Aperture Space Telescope (ATLAST)

    NASA Technical Reports Server (NTRS)

    Hopkins, Randall C.; Capizzo, Peter; Fincher, Sharon; Hornsby, Linda S.; Jones, David

    2010-01-01

    The Advanced Concepts Office at Marshall Space Flight Center completed a brief spacecraft design study for the 8-meter monolithic Advanced Technology Large Aperture Space Telescope (ATLAST-8m). This spacecraft concept provides all power, communication, telemetry, avionics, guidance and control, and thermal control for the observatory, and inserts the observatory into a halo orbit about the second Sun-Earth Lagrange point. The multidisciplinary design team created a simple spacecraft design that enables component and science instrument servicing, employs articulating solar panels for help with momentum management, and provides precise pointing control while at the same time fast slewing for the observatory.

  11. Thermal load of laser aperture masks in nonmechanical trephination for penetrating keratoplasty with the Er:YAG laser: comparison between stainless steel and ceramic masks

    Microsoft Academic Search

    Achim Langenbucher; Michael Küchle; Berthold Seitz; M. Murat Kus; Ashley Behrens; Erich Weimel; G. O. H. Naumann

    2000-01-01

    Purpose: Thermal effects on the laser aperture mask may play a major role in the thermal loading of the cornea during nonmechanical\\u000a trephination in penetrating keratoplasty. The purpose of this study was to assess the temperature increase on the laser mask\\u000a using the 2.94-m Er:YAG laser in order to find suitable parameters for avoidance of thermal damage to the cornea.

  12. Radiometric calibration method for large aperture infrared system with broad dynamic range.

    PubMed

    Sun, Zhiyuan; Chang, Songtao; Zhu, Wei

    2015-05-20

    Infrared radiometric measurements can acquire important data for missile defense systems. When observation is carried out by ground-based infrared systems, a missile is characterized by long distance, small size, and large variation of radiance. Therefore, the infrared systems should be manufactured with a larger aperture to enhance detection ability and calibrated at a broader dynamic range to extend measurable radiance. Nevertheless, the frequently used calibration methods demand an extended-area blackbody with broad dynamic range or a huge collimator for filling the system's field stop, which would greatly increase manufacturing costs and difficulties. To overcome this restriction, a calibration method based on amendment of inner and outer calibration is proposed. First, the principles and procedures of this method are introduced. Then, a shifting strategy of infrared systems for measuring targets with large fluctuations of infrared radiance is put forward. Finally, several experiments are performed on a shortwave infrared system with ?400??mm aperture. The results indicate that the proposed method cannot only ensure accuracy of calibration but have the advantage of low cost, low power, and high motility. Hence, it is an effective radiometric calibration method in the outfield. PMID:26192499

  13. On the Potential of Large Ring Lasers

    E-print Network

    G. E. Stedman; R. B. Hurst; K. U. Schreiber

    2007-07-10

    We describe a new ring laser with area A = 833 m^2 and update performance statistics for several such machines. Anandan & Chaio 1982 judged ring lasers inferior to matter interferometers as possible detectors of gravitational waves. However, we note that geophysically interesting results have been obtained from large ring lasers and that there is still a lot of room for improvements.

  14. Laser Power Meter Large, bright, backlit LCD

    E-print Network

    Woodall, Jerry M.

    Laser Power Meter FEATURES · Large, bright, backlit LCD display · Digital accuracy with analog-like movement for laser tuning · Works with thermopile and optical sensors · Intuitive button-driven user COMPATIBILITY · PowerMax® thermal sensors · Optical sensors FieldMaxII-TO Coherent Laser Measurement and Control

  15. A CLOSE COMPANION SEARCH AROUND L DWARFS USING APERTURE MASKING INTERFEROMETRY AND PALOMAR LASER GUIDE STAR ADAPTIVE OPTICS

    SciTech Connect

    Bernat, David [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Bouchez, Antonin H.; Cromer, John L.; Dekany, Richard G.; Moore, Anna M. [California Institute of Technology, Pasadena, CA 91125 (United States); Ireland, Michael; Tuthill, Peter [Sydney Institute for Astrophysics, School of Physics, University of Sydney (Australia); Martinache, Frantz [National Astronomical Observatory of Japan, Subaru Telescope, Hilo, HI 96720 (United States); Angione, John; Burruss, Rick S.; Guiwits, Stephen R.; Henning, John R.; Hickey, Jeff; Kibblewhite, Edward; McKenna, Daniel L.; Petrie, Harold L.; Roberts, Jennifer; Shelton, J. Chris; Thicksten, Robert P.; Trinh, Thang [Palomar Laser Guide Star Adaptive Optics Team, Palomar Observatory, California Institute of Technology, Palomar Mountain, CA 92060 (United States)

    2010-06-01

    We present a close companion search around 16 known early L dwarfs using aperture masking interferometry with Palomar laser guide star adaptive optics (LGS AO). The use of aperture masking allows the detection of close binaries, corresponding to projected physical separations of 0.6-10.0 AU for the targets of our survey. This survey achieved median contrast limits of {Delta}K {approx} 2.3 for separations between 1.2 {lambda}/D-4{lambda}/D and {Delta}K {approx} 1.4 at 2/3 {lambda}/D. We present four candidate binaries detected with moderate-to-high confidence (90%-98%). Two have projected physical separations less than 1.5 AU. This may indicate that tight-separation binaries contribute more significantly to the binary fraction than currently assumed, consistent with spectroscopic and photometric overluminosity studies. Ten targets of this survey have previously been observed with the Hubble Space Telescope as part of companion searches. We use the increased resolution of aperture masking to search for close or dim companions that would be obscured by full aperture imaging, finding two candidate binaries. This survey is the first application of aperture masking with LGS AO at Palomar. Several new techniques for the analysis of aperture masking data in the low signal-to-noise regime are explored.

  16. Advanced Technology Large-Aperture Space Telescope: Science Drivers and Technology Developments

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Glavallsco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2012-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8- to 16-m ultraviolet optical near Infrared space observatory for launch in the 2025 to 2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including: Is there life elsewhere in the Galaxy? We present a range of science drivers and the resulting performance requirements for ATLAST (8- to 16-marcsec angular resolution, diffraction limited imaging at 0.5 micron wavelength, minimum collecting area of 45 sq m, high sensitivity to light wavelengths from 0.1 to 2.4 micron, high stability in wavefront sensing and control). We also discuss the priorities for technology development needed to enable the construction of ATLAST for a cost that is comparable to that of current generation observatory-class space missions.

  17. Analysis of torque mounting configuration for nonlinear optics with large aperture

    NASA Astrophysics Data System (ADS)

    Liang, Yingchun; Su, Ruifeng; Liu, Haitao; Lu, Lihua

    2014-06-01

    Motivated by the need of decreasing the gravitational distortion and stress of the nonlinear optics with large aperture, as well as increasing the second harmonic generation (SHG) efficiency, a torque mounting configuration was proposed, where the external load brought about the torque to mitigate the distortion and stress. The distortion and stress were calculated by using the Finite Element Method (FEM), and discussed from the view of torque. The effects of the design parameters, namely the external load, loading width, shim plate location and shim plate width, were studied; the changing trends of the distortion and stress with these varying parameters were analyzed. Furthermore, the phase mismatches induced by the distortion and stress were calculated; finally, the SHG efficiency was solved considering the phase mismatch.

  18. Data correction techniques for the airborne large-aperture static image spectrometer based on image registration

    NASA Astrophysics Data System (ADS)

    Zhang, Geng; Shi, Dalian; Wang, Shuang; Yu, Tao; Hu, Bingliang

    2015-01-01

    We propose an approach to correct the data of the airborne large-aperture static image spectrometer (LASIS). LASIS is a kind of stationary interferometer which compromises flux output and device stability. It acquires a series of interferograms to reconstruct the hyperspectral image cube. Reconstruction precision of the airborne LASIS data suffers from the instability of the plane platform. Usually, changes of plane attitudes, such as yaws, pitches, and rolls, can be precisely measured by the inertial measurement unit. However, the along-track and across-track translation errors are difficult to measure precisely. To solve this problem, we propose a co-optimization approach to compute the translation errors between the interferograms using an image registration technique which helps to correct the interferograms with subpixel precision. To demonstrate the effectiveness of our approach, experiments are run on real airborne LASIS data and our results are compared with those of the state-of-the-art approaches.

  19. Development of a Large Aperture Nb3Sn Racetrack Quadrupole Magnet

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich, Daniel R.; Gourlay, Steve A.; Hannaford, Charles R.; Hafalia, Aurelio R.; Lietzke, Alan F.; Mattafirri, Sara; McInturff, Alfred D.; Nyman, Mark; Sabbi, Gianluca

    2005-06-01

    The U.S. LHC Accelerator Research Program (LARP), a collaboration between BNL, FNAL, LBNL, and SLAC, has among its major objectives the development of advanced magnet technology for an LHC luminosity upgrade. The LBNL Superconducting Magnet Group supports this program with a broad effort involving design studies, Nb{sub 3}Sn conductor development, mechanical models, and basic prototypes. This paper describes the development of a large aperture Nb{sub 3}Sn racetrack quadrupole magnet using four racetrack coils from the LBNL Subscale Magnet (SM) Program. The magnet provides a gradient of 95 T/m in a 110 mm bore, with a peak field in the conductor of 11.2 T. The coils are pre-stressed by a mechanical structure based on a pre-tensioned aluminum shell, and axially supported with aluminum rods. The mechanical behavior has been monitored with strain gauges and the magnetic field has been measured. Results of the test are reported and analyzed.

  20. Horizon: A Proposal for Large Aperture, Active Optics in Geosynchronous Orbit

    NASA Technical Reports Server (NTRS)

    Chesters, Dennis; Jenstrom, Del

    2000-01-01

    In 1999, NASA's New Millennium Program called for proposals to validate new technology in high-earth orbit for the Earth Observing-3 (NMP EO3) mission to fly in 2003. In response, we proposed to test a large aperture, active optics telescope in geosynchronous orbit. This would flight-qualify new technologies for both Earth and Space science: 1) a future instrument with LANDSAT image resolution and radiometric quality watching continuously from geosynchronous station, and 2) the Next Generation Space Telescope (NGST) for deep space imaging. Six enabling technologies were to be flight-qualified: 1) a 3-meter, lightweight segmented primary mirror, 2) mirror actuators and mechanisms, 3) a deformable mirror, 4) coarse phasing techniques, 5) phase retrieval for wavefront control during stellar viewing, and 6) phase diversity for wavefront control during Earth viewing. Three enhancing technologies were to be flight- validated: 1) mirror deployment and latching mechanisms, 2) an advanced microcontroller, and 3) GPS at GEO. In particular, two wavefront sensing algorithms, phase retrieval by JPL and phase diversity by ERIM International, were to sense optical system alignment and focus errors, and to correct them using high-precision mirror mechanisms. Active corrections based on Earth scenes are challenging because phase diversity images must be collected from extended, dynamically changing scenes. In addition, an Earth-facing telescope in GEO orbit is subject to a powerful diurnal thermal and radiometric cycle not experienced by deep-space astronomy. The Horizon proposal was a bare-bones design for a lightweight large-aperture, active optical system that is a practical blend of science requirements, emerging technologies, budget constraints, launch vehicle considerations, orbital mechanics, optical hardware, phase-determination algorithms, communication strategy, computational burdens, and first-rate cooperation among earth and space scientists, engineers and managers. This manuscript presents excerpts from the Horizon proposal's sections that describe the Earth science requirements, the structural -thermal-optical design, the wavefront sensing and control, and the on-orbit validation.

  1. Topology optimization-based lightweight primary mirror design of a large-aperture space telescope.

    PubMed

    Liu, Shutian; Hu, Rui; Li, Quhao; Zhou, Ping; Dong, Zhigang; Kang, Renke

    2014-12-10

    For the large-aperture space telescope, the lightweight primary mirror design with a high-quality optical surface is a critical and challenging issue. This work presents a topology optimization-based design procedure for a lightweight primary mirror and a new mirror configuration of a large-aperture space telescope is obtained through the presented design procedure. Inspired by the topology optimization method considering cast constraints, an optimization model for the configuration design of the mirror back is proposed, through which the distribution and the heights of the stiffeners on the mirror back can be optimized simultaneously. For the purpose of minimizing the optical surface deviation due to self-weight and polishing pressure loadings, the objective function is selected as to maximize the mirror structural stiffness, which can be achieved by minimizing the structural compliance. The total mass of the primary mirror is assigned as the constraint. In the application example, results of the optimized design topology for two kinds of mass constraints are presented. Executing the design procedure for specific requirements and postprocessing the topology obtained of the structure, a new mirror configuration with tree-like stiffeners and a multiple-arch back in double directions is proposed. A verification model is constructed to evaluate the design results and the finite element method is used to calculate the displacement of the mirror surface. Then the RMS deviation can be obtained after fitting the deformed surface by Zernike polynomials. The proposed mirror is compared with two classical mirrors in the optical performance, and the comparison results demonstrate the superiority of the new mirror configuration. PMID:25608076

  2. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    NASA Technical Reports Server (NTRS)

    Oegerle, William R.; Feinberg, L.; Purves, L.; Hyde, T.; Thronson, H.; Townsend, J.; Postman, M.; Bolcar, M.; Budinoff, J.; Dean, B.; Clampin, N.; Ebbets, D.; Gong, Q.; Gull, T.; Howard, J.; Jones, A.; Lyon, R.; Pasquale, B.; Perrygo, C.; Smith, S.; Thompson, P.; Woodgate, B.

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already developed for that mission. At the same time, we have identified several design changes to the JWST architecture, some of which are required due to the demanding wavefront error requirements at visible wavelengths. The optical telescope assembly has a segmented 9.2-meter aperture and consists of 36 hexagonal glass mirrors, each of which is I.3l5m in size (flat-to-flat). The telescope can be folded to fit in the 6.5m fairing on the planned upgrade to the Delta-IV heavy launch vehicle. Near-real time wavefront sensing and control is performed on-board the telescope using stars in the field of view to deliver diffraction limited imaging performance at 500nm wavelength. The optical design of the telescope provides an 8x20 arcmin FOV in which 4-5 instruments can be accommodated, plus fine guidance and wavefront sensors. Unlike JWST, the OTA sits at the end of a multi-gimbaled arm, allowing pitch and roll motion, and is isolated from the sunshield and spacecraft bus by an active isolation system. Our design permits servicing in order to extend the life of the observatory.

  3. ATLAST-9.2: A Deployable Large Aperture UVOIR Space Telescope

    NASA Astrophysics Data System (ADS)

    Oegerle, William R.; Feinberg, L.; Purves, L.; Hyde, T.; Thronson, H.; Townsend, J.; Postman, M.; Bolcar, M.; Budinoff, J.; Dean, B.; Clampin, M.; Ebbets, D.; Gong, Q.; Gull, T.; Howard, J.; Jones, A.; Lyon, R.; Pasquale, B.; Perrygo, C.; Smith, S.; Thompson, P.; Woodgate, B.

    2010-01-01

    We present the results of a study of a deployable version of the Advanced Technology Large Aperture Space Telescope (ATLAST) that could be launched on an Evolved Expendable Launch Vehicle (EELV). ATLAST is a concept for a next-generation UVOIR observatory to follow HST and JWST. The observatory retains significant heritage from JWST, thereby taking advantage of technologies and engineering already developed for that mission. At the same time, we have identified several design changes to the JWST architecture, some of which are required due to the demanding wavefront error requirements at visible wavelengths. The optical telescope assembly has a segmented 9.2-meter aperture and consists of 36 hexagonal glass mirrors, each of which is 1.315m in size (flat-to-flat). The telescope can be folded to fit in the 6.5m fairing on the planned upgrade to the Delta-IV heavy launch vehicle. Near-real time wavefront sensing and control is performed on-board the telescope using stars in the field of view to deliver diffraction limited imaging performance at 500nm wavelength. The optical design of the telescope provides an 8x20 arcmin FOV in which 4-5 instruments can be accommodated, plus fine guidance and wavefront sensors. Unlike JWST, the OTA sits at the end of a multi-gimbaled arm, allowing pitch and roll motion, and is isolated from the sunshield and spacecraft bus by an active isolation system. Our design permits servicing in order to extend the life of the observatory.

  4. Hybrid Electrostatic/Flextensional Mirror for Lightweight, Large-Aperture, and Cryogenic Space Telescopes

    NASA Technical Reports Server (NTRS)

    Patrick, Brian; Moore, James; Hackenberger, Wesley; Jiang, Xiaoning

    2013-01-01

    A lightweight, cryogenically capable, scalable, deformable mirror has been developed for space telescopes. This innovation makes use of polymer-based membrane mirror technology to enable large-aperture mirrors that can be easily launched and deployed. The key component of this innovation is a lightweight, large-stroke, cryogenic actuator array that combines the high degree of mirror figure control needed with a large actuator influence function. The latter aspect of the innovation allows membrane mirror figure correction with a relatively low actuator density, preserving the lightweight attributes of the system. The principal components of this technology are lightweight, low-profile, high-stroke, cryogenic-capable piezoelectric actuators based on PMN-PT (piezoelectric lead magnesium niobate-lead titanate) single-crystal configured in a flextensional actuator format; high-quality, low-thermal-expansion polymer membrane mirror materials developed by NeXolve; and electrostatic coupling between the membrane mirror and the piezoelectric actuator assembly to minimize problems such as actuator print-through.

  5. Edge-facet pumped, multi-aperture, thin-disk laser geometry for very high average power output scaling

    DOEpatents

    Zapata, Luis E.

    2004-12-21

    The average power output of a laser is scaled, to first order, by increasing the transverse dimension of the gain medium while increasing the thickness of an index matched light guide proportionately. Strategic facets cut at the edges of the laminated gain medium provide a method by which the pump light introduced through edges of the composite structure is trapped and passes through the gain medium repeatedly. Spontaneous emission escapes the laser volume via these facets. A multi-faceted disk geometry with grooves cut into the thickness of the gain medium is optimized to passively reject spontaneous emission generated within the laser material, which would otherwise be trapped and amplified within the high index composite disk. Such geometry allows the useful size of the laser aperture to be increased, enabling the average laser output power to be scaled.

  6. Fundamental limitation in adaptive optics: how to eliminate it? A full-aperture tilt measurement technique with a laser guide star

    Microsoft Academic Search

    Mikhail S. Belen'kii

    1994-01-01

    A theory for a new laser guide star technique is developed. This technique, for the first time, permits the sensing of a full-aperture tilt of the atmospheric wave front distortions using a laser guide star, eliminating one of the fundamental limitations of adaptive optics. By using a detailed analysis of the laser guide star image jitter for a conventional scheme

  7. Full-aperture tilt measurement technique with a laser guide star

    NASA Astrophysics Data System (ADS)

    Belen'kii, Mikhail S.

    1995-06-01

    A technique for measuring a full aperture tilt (FAT) with a laser guide star (LGS) is proposed. It is shown that information about a FAT is lost in a conventional LGS scheme because of the reciprocity of propagation paths. As a consequence neither the conventional LGS scheme nor its modifications with the receiver coaxial with the transmitter can be used to sense the FAT. A bistatic scheme that permits us to overcome the above difficulty is considered. This scheme permits us to single out the tilt component corresponding to the transmitting beam which is highly correlated with the FAT for a natural star. The tilt component corresponding to the reflected wave can be averaged out by averaging a LGS image motion over its angular extent. Such an averaging, however, does not affect the tilt component corresponding to the transmitting beam. This tilt conservation effect occurs due to the fact that a random motion of the transmitting beam causes a displacement of the LGS as a whole. The accuracy of measuring a FAT with a LGS is determined and the requirements for the measurement scheme are discussed.

  8. A hybridization technique for MLFMM utilizing generalized admittance matrices for a large class of cavity backed aperture scattering problems

    Microsoft Academic Search

    Rainer Bunger; Jan Ritter; A. Enneking; J. M. Reiter

    2003-01-01

    An efficient technique for the analysis of electromagnetic problems involving large metallic bodies with arbitrary complex interior and a number of apertures is proposed. Typical applications for this technique are the computation of EMC related transfer-functions of the electromagnetic field, describing the coupling of energy into complex systems as well as the computation of the RCS of complex cavities in

  9. A Future Large-Aperture UVOIR Space Observatory: Key Technologies and Capabilities

    NASA Astrophysics Data System (ADS)

    Stahle, Carl; Clampin, Mark; Balasubramanian, Kunjithapatham; Bolcar, Matthew R.; Feinberg, Lee; Mosier, Gary; Quijada, Manuel; Rauscher, Bernard J.; Redding, David; Shaklan, Stuart; Stahl, H. Philip; Thronson, Harley A.

    2015-01-01

    We present the key technologies and capabilities that will enable a future, large-aperture ultraviolet/optical/infrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10contrast with an inner working angle of 40 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of ~5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well as low cost, low mass, and rapid fabrication. Key challenges for the detector systems include visible-blind, high quantum efficiency UV arrays, photon counting visible and NIR arrays for coronagraphic spectroscopy and starlight wavefront sensing and control, and detectors with deep full wells with low persistence and radiation tolerance to enable transit imaging and spectroscopy at all wavelengths. Finally, mirror coatings with high reflectivity (> 90%), high uniformity (< 1%) and low polarization (< 1%) that are scalable to large diameter mirror substrates will be essential for ensuring that both high throughput UV observations and high contrast observations can be performed by the same observatory.

  10. Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  11. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, E. J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, M. A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

    2013-01-01

    The increasing scale of cryogenic detector arrays for sub-millimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n = 3.4, low loss, and relatively high thermal conductivity is a nearly optimal material for these purposes, but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coffecient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated and coated silicon lenses as large as 33.4 cm in diameter with coatings optimized for use between 125-165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30 deg. with low cross-polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to sub-millimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

  12. The Large Aperture Gamma Ray Observatory as an Observational Alternative at High Altitude

    NASA Astrophysics Data System (ADS)

    Rosales, M.

    2011-10-01

    Although satellite observations have revealed some mysteries about the origin and location of cosmic rays at low energies, questions remain to be resolved in higher energy ranges (>1 GeV). However, the flow of particles at high energies is very low, large sensitive areas are necessary, so that the detection of secondary particles from observatories on the surface of the earth is a technically viable solution. While the Pierre Auger Observatory has such capacity given its 16000 m^2 of detectors, low height above sea level greatly reduces its detection capability. The Large Aperture Gamma Ray Observatory (LAGO) is an observational alternative that attempts to overcome this limitation. This project was started in 2005, placing water Cherenkov Detectors at high altitude. Observation sites have been selected with some basic requirements: altitude, academic and technical infrastructure, existence of a research group responsible for assembly and maintenance of the detectors and the analysis, visualization, divulgation and data storage. This paper presents the general status of the observatories of Sierra Negra-México, Chacaltaya-Bolívia, Marcapomacocha-Perú, Mérida-Venezuela and Bucaramanga-Colombia.

  13. Acoustic performance of a large-aperture, seabed, fiber-optic hydrophone array

    NASA Astrophysics Data System (ADS)

    Cranch, G. A.; Crickmore, R.; Kirkendall, C. K.; Bautista, A.; Daley, K.; Motley, S.; Salzano, J.; Latchem, J.; Nash, P. J.

    2004-06-01

    A large-aperture, seabed mounted, fiber-optic hydrophone array has been constructed and characterized. The system is designed for use as a large area surveillance array for deployment in shallow water regions. The underwater portion comprises two arrays of 48 hydrophones separated by a 3 km fiber-optic link, which are connected to a shore station by 40 km of single-mode optical fiber. The hydrophone is based on a fiber-optic Michelson interferometer and the acoustic transduction mechanism is a fiber-wrapped mandrel design. No electrical power is required in the underwater portion. The performance of the system is described, characterized during laboratory measurements and during a recent sea trial. Specifically, measurements of the acoustic resolution, array shape, beam patterns, array gain, and target tracking capability of this array. The system demonstrates self-noise levels up to 20 dB (typically 10 dB) lower than the ambient acoustic noise experienced in the sea trial and array gains close to the theoretical maximum. The system telemetry and electronics have been designed to be expandable to accommodate several hundred hydrophones.

  14. Near-field characterization of micro-aperture surface emitting laser for near field data storage

    Microsoft Academic Search

    S. Shinada; F. Koyama; N. Nishiyama; M. Arai; K. Iga

    2000-01-01

    Summary form only given. We have fabricated a 400 nm square micro-aperture VCSEL with single transverse mode operation. We carried out the near field characterization using a sharpened fiber probe. The FWHM of intensity below threshold was 250 nm, and our metal micro-aperture VCSEL may have a potential for a high resolution optical head

  15. Interstellar particles detected by high-power large-aperture radar

    NASA Astrophysics Data System (ADS)

    Close, S.; Marshall, R.; Linscott, I.; Pifko, S.; Janches, D.

    2014-07-01

    We report the first characterization of interstellar dust and meteoroids as a function of its orbital parameters using plasma data collected by two high-power large-aperture radars, including ALTAIR and the Jicamarco Observatory, during a year-long experiment. We achieve this by measuring the weak plasma called head echoes that form when particles ablate and ionize in our atmosphere. Head echoes move with the parent particle and provide information on the plasma signal strength, 3D position, velocity and deceleration that is achievable through the radar's monopulse and interferometric systems. We use a new Finite Difference Time Domain (FDTD) model, in addition to an analytical scattering model, to correlate measured signal strength with plasma density and particle mass. Through analysis of the ballistic coefficient, we are further able to characterize the bulk density of the dust or meteoroid as a function of its orbital parameters by identifying those particles with eccentricities > 1. Our results indicate that interstellar particles are rare in Earth's atmosphere, comprising less than 5 % of the total detected population, and are also detected at the limit of sensitivity. Interstellar particles also have lower bulk densities than interplanetary particles detected in Earth's atmosphere with masses below 1 microgram.

  16. Dynamic characteristics analysis of a large-aperture rotating prism with adjustable radial support.

    PubMed

    Li, Anhu; Wang, Wei; Bian, Yongming; Liu, Liren

    2014-04-01

    Support elements as key components in performing the opto-mechanical function have been an important topic for optical system development. Focusing on a rotation prism with a large aperture and asymmetric loading, a radial multi-segment support is developed to solve the dynamic mounting issue. In order to explore the actual surface deformations over the full rotation, a novel dynamic analysis method to extract the transient load spectrum is established to access the surface deformations, including dynamic load extraction to connect varying loads with corresponding rotation positions, typical position analysis to obtain maximum deformation values, and vibration analysis. The results show that a maximum peak-to-valley value on the plane side reaches 103.16 nm when the prism rotates to 159.84°, and that of the wedge side is 74.38 nm when the prism rotates to 213.84°, both of which are less than ?/4 (?=632.8 nm). However, when excited by the external loads with response frequency, the surface deformations become more serious. Because the dynamic characteristics obtained can reflect the actual usage situation, the proposed method is preferable for system development. PMID:24787184

  17. 8 Meter Advanced Technology Large-Aperture Space Telescope (ATLAST-8m)

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    2010-01-01

    ATLAST-8m (Advanced Technology Large Aperture Space Telescope) is a proposed 8-meter monolithic UV/optical/NIR space observatory (wavelength range 110 to 2500 nm) to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V heavy lift vehicle. Given its very high angular resolution (15 mas @ 500 nm), sensitivity and performance stability, ATLAST-8m is capable of achieving breakthroughs in a broad range of astrophysics including: Is there life elsewhere in the Galaxy? An 8-meter UVOIR observatory has the performance required to detect habitability (H2O, atmospheric column density) and biosignatures (O2, O3, CH4) in terrestrial exoplanet atmospheres, to reveal the underlying physics that drives star formation, and to trace the complex interactions between dark matter, galaxies, and intergalactic medium. The ATLAST Astrophysics Strategic Mission Concept Study developed a detailed point design for an 8-m monolithic observatory including optical design; structural design/analysis including primary mirror support structure, sun shade and secondary mirror support structure; thermal analysis; spacecraft including structure, propulsion, GN&C, avionics, power systems and reaction wheels; mass and power budgets; and system cost. The results of which were submitted by invitation to NRC's 2010 Astronomy & Astrophysics Decadal Survey.

  18. CONCEPTUAL MAGNETIC DESIGN OF THE LARGE APERTURE D2 DIPOLE FOR LHC UPGRADE*

    E-print Network

    Gupta, Ramesh

    that is currently installed in LHC using standard cryostat and support posts. Oblate shaped yoke provides extra iron.1 0.1 0.1 With special shaping of iron, it is possible to design 105 mm aperture D2 dipole for HL-LHC with the desired field quality and low fringe field outside the yoke despite the field in the two apertures being

  19. Design of a large-aperture lens antenna usable over a +/- 15 deg scanning sector

    NASA Technical Reports Server (NTRS)

    Parsons, Chester L.; Miller, Lee S.

    1988-01-01

    A lens antenna design is described which requires the formation of both on-axis and far off-axis beams. The aperture is about 100 wavelengths in diameter, and the off-axis beams are displaced +/- 20 beamwidths from the axis. The results are indicative of the much greater scan capabilities of lensatic antennas compared to paraboloidal designs when both have single-aperture nonarray feeds.

  20. Imaging the midcontinent rift beneath Lake Superior using large aperture seismic data

    USGS Publications Warehouse

    Trehu, Anne M.; Morel-a-l'Huissier, Patrick; Meyer, R.; Hajnal, Z.; Karl, J.; Mereu, R. F.; Sexton, J.; Shay, J.; Chan, W. K.; Epili, D.; Jefferson, T.; Shih, X. R.; Wendling, S.; Milkereit, B.; Green, A.; Hutchinson, Deborah R.

    1991-01-01

    We present a detailed velocity model across the 1.1 billion year old Midcontinent Rift System (MRS) in central Lake Superior. The model was derived primarily from onshore-offshore large-aperture seismic and gravity data. High velocities obtained within a highly reflective half-graben that was imaged on coincident seismic reflection data demonstrate the dominantly mafic composition of the graben fill and constrain its total thickness to be at least 30km. Strong wide-angle reflections are observed from the lower crust and Moho, indicating that the crust is thickest (55–60km) beneath the axis of the graben. The total crustal thickness decreases rapidly to about 40 km beneath the south shore of the lake and decreases more gradually to the north. Above the Moho is a high-velocity lower crust interpreted to result from syn-rift basaltic intrusion into and/or underplating beneath the Archean lower crust. The lower crust is thickest beneath the axis of the main rift half-graben. A second region of thick lower crust is found approximately 100km north of the axis of the rift beneath a smaller half graben that is interpreted to reflect an earlier stage of rifting. The crustal model presented here resembles recent models of some passive continental margins and is in marked contrast to many models of both active and extinct Phanerozoic continental rift zones. It demonstrates that the Moho is a dynamic feature, since the pre-rift Moho is probably within or above the high-velocity lower crust, whereas the post-rift Moho is defined as the base of this layer. In the absence of major tectonic activity, however, the Moho is very stable, since the large, abrupt variations in crustal thickness beneath the MRS have been preserved for at least a billion years.

  1. Determining suitability of Large Aperture Scintillometer for validating remote sensing based evapotranspiration maps

    NASA Astrophysics Data System (ADS)

    Paul, G.; Gowda, P. H.; Howell, T. A.; Basu, S.; Colaizzi, P. D.; Marek, T.

    2013-12-01

    Scintillation method is a relatively new technique for measuring the sensible heat and water fluxes over land surfaces. Path integrating capabilities of scintillometer over heterogeneous landscapes make it a potential tool for comparing the energy fluxes derived from remote sensing based energy balance algorithms. For this reason, scintillometer-derived evapotranspiration (ET) fluxes are being used to evaluate remote sensing based energy balance algorithms for their ability to estimate ET fluxes. However, LAS' (Large Aperture Scintillometer) ability to derive ET fluxes is not thoroughly tested. The objective of this study was to evaluate LAS- and Surface Energy Balance System (SEBS)-derived fluxes against lysimetric data to determine LAS' suitability for validating remote sensing based evapotranspiration (ET) maps. The study was conducted during the Bushland Evapotranspiration and Agricultural Remote sensing EXperiment - 2008 (BEAREX-08) at the USDA-ARS Conservation and Production Research Laboratory (CPRL), Bushland, Texas. SEBS was coded in a GIS environment to retrieve ET fluxes from the high resolution imageries acquired using airborne multispectral sensors. The CPRL has four large weighing lysimeters (3 m long x 3 m wide x 2.4 m deep), each located in the middle of approximately 5 ha fields, arranged in a block pattern. The two lysimeter fields located on the east (NE and SE) were managed under irrigated conditions, and the other two lysimeters on the west (NW and SW) were under dryland management. Each lysimeter field was equipped with an automated weather station that provided measurements for net radiation (Rn), Ts, soil heat flux (Go), Ta, relative humidity, and wind speed. During BEAREX08, the NE and SE fields were planted to cotton on May 21, and the NW and SW dryland lysimeters fields were planted to cotton on June 5. One LAS each was deployed across two large dryland lysimeter fields (NW and SW) and two large irrigated lysimeter fields (NE and SE). The structural parameter of refractive index of air was measured at 1-min interval and averaged at 15-min, and synchronized with weather station. The source area (footprint) of the surface energy fluxes were computed using a footprint model. ET fluxes were derived using LAS-estimated H as a residual from the energy balance equation. Comparison of SEBS- and LAS-derived ET fluxes were made against lysimetric data and performance of each method was discussed to determine the suitability of LAS for evaluating accuracy of remote sensing based ET maps.

  2. Assessing Inter-Sensor Variability and Sensible Heat Flux Derivation Accuracy for a Large Aperture Scintillometer

    PubMed Central

    Rambikur, Evan H.; Chávez, José L.

    2014-01-01

    The accuracy in determining sensible heat flux (H) of three Kipp and Zonen large aperture scintillometers (LAS) was evaluated with reference to an eddy covariance (EC) system over relatively flat and uniform grassland near Timpas (CO, USA). Other tests have revealed inherent variability between Kipp and Zonen LAS units and bias to overestimate H. Average H fluxes were compared between LAS units and between LAS and EC. Despite good correlation, inter-LAS biases in H were found between 6% and 13% in terms of the linear regression slope. Physical misalignment was observed to result in increased scatter and bias between H solutions of a well-aligned and poorly-aligned LAS unit. Comparison of LAS and EC H showed little bias for one LAS unit, while the other two units overestimated EC H by more than 10%. A detector alignment issue may have caused the inter-LAS variability, supported by the observation in this study of differing power requirements between LAS units. It is possible that the LAS physical misalignment may have caused edge-of-beam signal noise as well as vulnerability to signal noise from wind-induced vibrations, both having an impact on the solution of H. In addition, there were some uncertainties in the solutions of H from the LAS and EC instruments, including lack of energy balance closure with the EC unit. However, the results obtained do not show clear evidence of inherent bias for the Kipp and Zonen LAS to overestimate H as found in other studies. PMID:24473285

  3. Thermal Analysis of the Advanced Technology Large Aperture Space Telescope (ATLAST) 8 Meter Primary Mirror

    NASA Technical Reports Server (NTRS)

    Hornsby, Linda; Stahl, H. Philip; Hopkins, Randall C.

    2010-01-01

    The Advanced Technology Large Aperture Space Telescope (ATLAST) preliminary design concept consists of an 8 meter diameter monolithic primary mirror enclosed in an insulated, optical tube with stray light baffles and a sunshade. ATLAST will be placed in orbit about the Sun-Earth L2 and will experience constant exposure to the sun. The insulation on the optical tube and sunshade serve to cold bias the telescope which helps to minimize thermal gradients. The primary mirror will be maintained at 280K with an active thermal control system. The geometric model of the primary mirror, optical tube, sun baffles, and sunshade was developed using Thermal Desktop(R) SINDA/FLUINT(R) was used for the thermal analysis and the radiation environment was analyzed using RADCAD(R). A XX node model was executed in order to characterize the static performance and thermal stability of the mirror during maneuvers. This is important because long exposure observations, such as extra-solar terrestrial planet finding and characterization, require a very stable observatory wave front. Steady state thermal analyses served to predict mirror temperatures for several different sun angles. Transient analyses were performed in order to predict thermal time constant of the primary mirror for a 20 degree slew or 30 degree roll maneuver. This paper describes the thermal model and provides details of the geometry, thermo-optical properties, and the environment which influences the thermal performance. All assumptions that were used in the analysis are also documented. Parametric analyses are summarized for design parameters including primary mirror coatings and sunshade configuration. Estimates of mirror heater power requirements are reported. The thermal model demonstrates results for the primary mirror heated from the back side and edges using a heater system with multiple independently controlled zones.

  4. Distributed aperture active imaging

    Microsoft Academic Search

    Joseph C. Marron; Richard L. Kendrick

    2007-01-01

    With a distributed aperture imaging system, one creates a large imaging aperture by combining the light from a series of distributed telescopes. In doing this, one can construct a fine-resolution imaging system with reduced volume. In this paper we present work on distributed aperture, active imaging systems that use coherent detection and digital image formation. In such a system, the

  5. Sub-aperture interferometric testing of a large-scale elliptical mirror under thermal-vacuum conditions

    Microsoft Academic Search

    James N. Howell; Richard T. Summers; Michael G. Dittman; Kevin Weed; Robert M. Bates; Peter T. Spuhler; Wayne Pierre

    2005-01-01

    Interferometric testing of large-sized optics in a thermal vacuum environment poses challenges not normally found in an optical metrology lab. Unless the test equipment is thermal-vacuum compatible, it must be installed in an ambient environment with the test item viewed through a window in the thermal-vacuum chamber. Limitations in chamber port size preclude normal-incidence viewing of the full aperture of

  6. Near-Field Modulation of AlGaInP Laser Diode Emissions by an Aperture Probe of Near-Field Optical Microscope

    Microsoft Academic Search

    Yasushi Kamiyama; Akihiro Tomioka; Takahiro Anzai; Kazuhisa Iwamoto; Wataru Susaki

    2010-01-01

    In situ emission profiles of AlGaInP multiple quantum well laser diodes (LD's) observed by a near-field scanning optical microscope (NSOM) aperture probe shows a single broad elliptic profile similar to a far-field observation, whereas the local emission spectrum was different depending where the aperture probe was placed within the emission profile. This observation suggests the existence of a near-field coupling

  7. Defining A Risk Analysis Strategy for Exo-Earth Yields from a Future Large Aperture UVOIR Space Telescope

    NASA Astrophysics Data System (ADS)

    Mandell, Avi; Stark, Christopher C.; Roberge, Aki; Domagal-Goldman, Shawn; Stapelfeldt, Karl R.; Robinson, Tyler

    2015-01-01

    The discovery and characterization of Earth-like planets around Sun-like stars using high-contrast imaging is a critical science metric for constraining the requirements on the next-generation large UVOIR space telescope. The dominant driver for the observatory architecture, cost and schedule is the telescope aperture size. Therefore it is important to provide as much constraint as possible on the required aperture size early in the design and planning process.An estimate of the detection yield for Earth-like planets can be calculated using a Monte Carlo simulation of a design reference mission (DRM), allowing the exploration of a variety of mission design and astrophysical parameters. We have developed such a code (Stark et al. 2014); it optimizes the target list and exposure times to maximize mission yield for a specific set of mission parameters. However, many of the important astrophysical quantities and future technical capabilities that feed into these parameters are not well constrained. This leads to a large uncertainty in the final mission architecture needed to achieve a specific exo-Earth yield.In this presentation we discuss the various physical and technological parameters that go into the DRM simulations, and the associated uncertainties based on the current state of research. We then present a strategy for a three-tiered risk assessment using these uncertainties, and conclude with a discussion of the current range in telescope aperture size associated with each risk level.

  8. Attenuating the Absorption Contribution on {C_{n2}} Estimates with a Large-Aperture Scintillometer

    NASA Astrophysics Data System (ADS)

    Solignac, P. A.; Brut, A.; Selves, J. L.; Béteille, J. P.; Gastellu-Etchegorry, J. P.

    2012-05-01

    Large-aperture scintillometers (LAS) are often used to characterize atmospheric turbulence by measuring the structure parameter of the refractive index {C_{n2}} . However, absorption phenomena can lead to an overestimation of {C_{n2}} . By applying an accurate numerical filtering technique called the Gabor transform to the signal output of a LAS, we improved our knowledge of the accuracy of the measured {C_{n2}} by determining and attenuating the contribution of absorption. Two studies are presented on a 12-day dataset using either fixed band pass or adaptive filtering. The first consists of evaluating the best-fit filter for which the resulting {C_{n2}} is independent of meteorological conditions, especially crosswind, and the second consists in accurately reconstructing the signal to remove absorption, without losing information on {C_{n2}} . A reference {C_{n2}} (hereafter `reconstructed {C_{n2}} ') is created by accurately removing absorption from the scintillation spectrum, and is used to evaluate each filter. By comparing the `reconstructed {C_{n2}} ' with a raw {C_{n2}} measured with a scintillometer, in the presence of absorption, we found that the average relative contribution of absorption to the measurement of {C_{n2}} is approximately 9%. However, the absorption phenomenon is highly variable; occasionally, in the worst cases, we estimate that the absorption phenomenon could represent 81% of the value of {C_{n2}} . Some explanations for this high variability are proposed with respect to theoretical considerations. Amongst the fixed band-pass filtering used, we conclude on the preferential use of a band-pass filter [0.2-400 Hz] for {C_{n2}} , as its performance is only slightly affected by the crosswind, and that the mean absorption contribution is reduced to 5.6%, with a maximum value of 60%. Using an adaptive filter on the 12-day dataset really improves the filtering accuracy for both points discussed—the independence of meteorological conditions and the quality of signal reconstruction.

  9. X-ray refractive large aperture rolled prism lenses as condensers for x-ray tubes

    NASA Astrophysics Data System (ADS)

    Vogt, H.; Simon, M.; Last, A.; Marschall, F.; Mohr, J.; Nazmov, V.; Eisenhower, R.; Mettendorf, K. U.

    2011-10-01

    At the Institute of Microstructure Technology (IMT) at Karlsruhe Institute of Technology (KIT), refractive X-ray optics are developed. These optics are proposed to be used as condenser optics in X-Ray spectroscopy and microscopy applications with an X-ray tube as a source. To produce the lenses, a thin structured foil with equidistant fins in triangular form is casted from a structured silicon wafer. The foil is then wound around a glass fibre core. Due to this fabrication method, it is possible to produce large-aperture lenses with low absorption in comparison to other types of refractive X-Ray optics, like X-ray lenses with continuous parabolic shape or prism lenses. The first are limited due to their absorption while the latter are limited due to their mechanical stability of the prism columns. The optimisation of the so called X-Ray rolled prism lenses (RXPL) is underway at the institute and involves several parameters. One important property of the lenses is the correct form of the wound foil layers. This determines the number of necessary refractive elements at a given radius, which in turn determines the refracted slope and focal position of the transmitted beam. The spatial extent of the x-ray source is also being accounted for in the lens design. Another important point is the diameter of the winding core, which should be as small as possible due to the fact that the winding core reduces the active area of the lens. The rolling process itself is also revised to produce lenses with the above-mentioned small diameter winding cores and bend foil layers while sustaining a tight- fitting foil bundle. The lenses are studied at different energies and types of X-Ray tubes, as well as synchrotron sources, to gain additional information of the internal structure of the lens after the winding process. In this paper the current status of the lens development and results at X-Ray tube sources for use in diffractometers is presented.

  10. A Large Sparse Aperture Densified Pupil Hypertelescope Concept for Ground Based Detection of Extra-Solar Earth-Like Planets

    NASA Technical Reports Server (NTRS)

    Gezari, D.; Lyon, R.; Woodruff, R.; Labeyrie, A.; Oegerle, William (Technical Monitor)

    2002-01-01

    A concept is presented for a large (10 - 30 meter) sparse aperture hyper telescope to image extrasolar earth-like planets from the ground in the presence of atmospheric seeing. The telescope achieves high dynamic range very close to bright stellar sources with good image quality using pupil densification techniques. Active correction of the perturbed wavefront is simplified by using 36 small flat mirrors arranged in a parabolic steerable array structure, eliminating the need for large delat lines and operating at near-infrared (1 - 3 Micron) wavelengths with flats comparable in size to the seeing cells.

  11. Design and construction of a large aperture quadrupole electromagnet for ILSE

    SciTech Connect

    Fawley, W.M.; Vella, M.C.; Peters, C.; Stuart, M.; Faltens, A.

    1995-08-01

    We are currently constructing a prototype quadrupole electromagnet for the proposed Induction Linac Systems Experiment (ILSE) at LBNL. ILSE will address many physics and engineering issues relevant to the design of a heavy-ion fusion driver accelerator. The pulsed electromagnet has two layers of current windings and will produce a field gradient of 28 T/m, wi a usable aperture of 6 cm. It operates at a repetition rate of 1 Hz, steady-state. In this paper, we discuss how the interaction of various concerns such as maximum dynamic aperture, short lattice period, field quality, iron yoke weight, heat transfer, and voltage standoff have led to our particular design choices. We also present 2- and 3-D numerical calculations concerning field topography and the results of transport simulations of space-charge dominated ion beams with ILSE parameters.

  12. Theoretical Study of Field Intensity of THz Radiation from GaAs Large-Aperture Photoconductive Antennas

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Hou, Lei

    2006-10-01

    We simulate the THz radiation's time domain waveforms of both the near field and the far field of a GaAs large aperture photoconductive antenna based on the current surge model. Because the micro-kinetic factors, such as transient state changes of current carrier's mobility and lifetime of current carriers, are taken into account in the calculation, we find out the influences of these factors on the THz radiation intensity by changing the above parameters. The results are of guiding significance to design of high-power photoconductive THz radiation antenna materials.

  13. Large-aperture optical modulator materials. Lead lanthanum zirconate titanate ceramic and lithium niobate crystal show promise as modulator materials for optical transmitters with up to 6-inch apertures

    Microsoft Academic Search

    R. P. Bocker; G. M. Meana; M. A. Monahan; G. C. Mooradian; W. E. Richards; H. F. Taylor

    1977-01-01

    Six categories of active optical materials were found to qualify as potential large-aperture optical modulator material candidates. Two of these, the electro-optical linear Pockels lithium niobate crystals and the ferroelectric ceramic lead lanthanum zirconate titanate wafers showed real promise. Both of these satisfy the requirements of field of view, optical quality, frequency response, and economic availability, and both performed above

  14. Relativity and large ring-laser gyroscopes

    NASA Astrophysics Data System (ADS)

    Soffel, M.; Tian, W.

    2012-12-01

    This article deals with a post-Newtonian description of large ring-laser gyroscopes. To this end first two local topocentric reference systems are introduced: a topocentric celestial (ToCRS) and a topocentric terrestrial reference system (ToTRS). The GCRS acts as starting point for these two systems. Whereas the ToCRS is kinematically non-rotating with respect to the GCRS the spatial coordinates of the ToTRS are determined by the ITRS. From the covariant Maxwell-equations a post-Newtonian expression for the Sagnac frequency shift is derived containing contributions from the geodetic-, Lense-Thirring- and Thomas-precession. These relativistic contributions are calculated as a function of some orientation angle ? of the Sagnac platform. Conditions for the measurability of these terms by a system of laser-gyros are discussed.

  15. Full aperture backscatter station imager (FABSI) diagnostics system for far-field imaging of laser plasma instabilities on Nova

    SciTech Connect

    Wilke, M.D.; Fernandez, J.C.; Berggren, R.R.; Montgomery, D.; Faulkner, J.; Looney, L.; Jimerson, J. [Los Alamos National Lab., NM (United States); Horton, R.F. [SAIC, Albuquerque, NM (United States)

    1996-06-01

    In ICF, the understanding of laser plasma scattering processes is essential for laser target coupling and in controlling the symmetry of indirect drive implosions. The existing Nova Full Aperture Backscatter Station (FABS) has been useful in understanding laser plasma instabilities occurring in hohlraums by measuring the quantity, spectral distribution and near-field spatial distributions of Brillouin and more recently Raman backscatter. Equally important is an understanding of the farfield spatial intensity distribution which provides information on density, temperature and velocity gradient distributions, and which affect capsule implosion symmetry in hohlraums. Such information could potentially help in understanding processes such as filamentation and saturation mechanism. This paper describes a broad-band, color-corrected far-field imager and associated diagnostics capable of imaging the source of scattered light to better than 25 {micro}m resolution. The imager can either image Brillouin or Raman backscatter through the Nova beam 7 focusing lens or be used like a microscope to image side scatter from other beams.

  16. Effect of therapeutic femtosecond laser pulse energy, repetition rate, and numerical aperture on laser-induced second and third harmonic generation in corneal tissue.

    PubMed

    Calhoun, William R; Ilev, Ilko K

    2015-05-01

    Clinical therapy incorporating femtosecond laser (FSL) devices is a quickly growing field in modern biomedical technology due to their precision and ability to generate therapeutic effects with substantially less laser pulse energy. FSLs have the potential to produce nonlinear optical effects such as harmonic generation (HG), especially in tissues with significant nonlinear susceptibilities such as the cornea. HG in corneal tissue has been demonstrated in nonlinear harmonic microscopy using low-power FSLs. Furthermore, the wavelength ranges of harmonic spectral emissions generated in corneal tissues are known to be phototoxic above certain intensities. We have investigated how the critical FSL parameters pulse energy, pulse repetition rate, and numerical aperture influence both second (SHG) and third harmonic generation (THG) in corneal tissue. Experimental results demonstrated corresponding increases in HG intensity with increasing repetition rate and numerical aperture. HG duration decreased with increasing repetition rate and pulse energy. The data also demonstrated a significant difference in HG between FSL parameters representing the two most common classes of FSL therapeutic devices. PMID:25779115

  17. Large-field-of-view laser-scanning OR-PAM using a fibre optic sensor

    NASA Astrophysics Data System (ADS)

    Allen, T. J.; Zhang, E.; Beard, P. C.

    2015-03-01

    Laser-Scanning-Optical-Resolution Photoacoustic Microscopy (LSOR-PAM) requires an ultrasound detector with a low noise equivalent pressure (NEP) and a large angular detection aperture in order to image a large field of view (FOV). It is however challenging to meet these requirements when using piezoelectric receivers since using a small sensing element size (<100?m) in order to achieve a large angular detection aperture will inevitability reduce the sensitivity of the detector as it scales with decreasing element size. Fibre optic ultrasound sensors based on a Fabry Perot cavity do not suffer from this limitation and can provide high detection sensitivity (NEP<0.1kPa over a 20 MHz measurement bandwidth) with a large angular detection aperture due to their small active element size (~10?m). A LSOR-PAM system was developed and combined with this type of fibre optic ultrasound sensor. A set of phantom studies were undertaken. The first study demonstrated that a high resolution image over a large field of view (Ø11mm) could be obtained with a sampledetector separation of only 1.6mm. In the second study, a 12?m diameter tube filled with methylene blue whose absorption coefficient was similar to that of blood was visualised demonstrating that the fibre optic sensor could provide sufficient SNR for in-vivo microvascular OR-PAM imaging. These preliminary results suggest that the fibre optic sensor has the potential to outperform piezoelectric detectors for Laser-Scanning Optical Resolution Photoacoustic Microscopy (LSOR-PAM).

  18. Fast, High Fidelity State Detection of a 171Yb+ Ion Using Large Numerical Aperture Optics

    NASA Astrophysics Data System (ADS)

    Noek, Rachel; Vrijsen, Geert; Gaultney, Daniel; Mount, Emily; Baek, So-Young; Maunz, Peter; Kim, Jungsang

    2013-05-01

    Trapped ions provide a viable choice for quantum bits (qubits) for quantum information as most of the DiVincenzo criteria have been demonstrated. However, some scalability challenges remain including the qubit measurement speed, which is typically much slower than gate times, and remote entanglement generation rate, which is currently much slower than qubit coherence times. Current photon collection rates limit the overall speed and fidelity of the qubit detection in a trapped ion quantum processor. Recent advances have been made in improving the state detection fidelity, but the detection time remains long (~ ms) compared to typical gate operations (~101-102 us). Here, we use a high numerical aperture (NA =0.6) lens capable of collecting 10% of the solid angle of light emitted by a single ion to measure a detection fidelity of 99.7% (99.85%) with an integration time of 50 us (150 us). Advanced discrimination schemes can further improve the state detection speed. The 171Yb+ ion is trapped in a Thunderbird type surface trap designed and fabricated at Sandia National Laboratories. Trapped ions provide a viable choice for quantum bits (qubits) for quantum information as most of the DiVincenzo criteria have been demonstrated. However, some scalability challenges remain including the qubit measurement speed, which is typically much slower than gate times, and remote entanglement generation rate, which is currently much slower than qubit coherence times. Current photon collection rates limit the overall speed and fidelity of the qubit detection in a trapped ion quantum processor. Recent advances have been made in improving the state detection fidelity, but the detection time remains long (~ ms) compared to typical gate operations (~101-102 us). Here, we use a high numerical aperture (NA =0.6) lens capable of collecting 10% of the solid angle of light emitted by a single ion to measure a detection fidelity of 99.7% (99.85%) with an integration time of 50 us (150 us). Advanced discrimination schemes can further improve the state detection speed. The 171Yb+ ion is trapped in a Thunderbird type surface trap designed and fabricated at Sandia National Laboratories. This work was supported by the Office of the Director of National Intelligence and Intelligence Advanced Research Projects Activity through the Army Research Office.

  19. Measuring large numerical apertures by imaging the angular distribution of radiation

    E-print Network

    Enderlein, Jörg

    , Dublin City University, Dublin 9, Ireland thomas.ruckstuhl@dcu.ie Abstract: Exact knowledge-molecule detection in liquids by laser-induced fluores- cence," Acc. Chem. Res. 29, 607-613 (1996). 2. J. Enderlein and technology," Chem. Phys. Chem. 4, 792-808 (2003). 3. R. Rigler, J. Widengren "Ultrasensitive Detection

  20. Large linewidth-enhancement factor in a microchip laser

    SciTech Connect

    Szwaj, Christophe; Lacot, Eric; Hugon, Olivier [Laboratoire de Physique des Lasers, Atomes et Molecules, UMR CNRS 8523, CERLA, FR CNRS 1416, Universite des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq Cedex (France); Laboratoire de Spectrometrie Physique, UMR CNRS 5588, Universite Joseph Fourier, F-38402 Saint Martin d'Heres (France)

    2004-09-01

    We evidence experimentally that the linewidth-enhancement factor {alpha} can take a rather large value ({alpha}{approx_equal}1) for a nonsemiconductor laser, here a Nd{sup 3+}: YAG microchip laser. This measure is performed using an original and simple method adapted to this kind of laser and based on the variations of the laser relaxation frequency when the laser is subjected to an optical feedback.

  1. Concept study of an Extremely Large Hyper Telescope (ELHyT) with 1200m sparse aperture for direct imaging at 100 micro-arcsecond resolution

    NASA Astrophysics Data System (ADS)

    Labeyrie, Antoine; Mourard, Denis; Allouche, Fatmé; Chakraborthy, Rijuparna; Dejonghe, Julien; Surya, Arun; Bresson, Yves; Aime, Claude; Mary, David; Carlotti, Alexis

    2012-07-01

    The hypertelescope construction initiated in the Southern Alps (Labeyrie et al., this conference) has provided some preliminary operating experience indicating that larger versions, up to perhaps 1200m, are probably feasible at suitable sites. The Arecibo-like architecture of such instruments does not require the large mount and dome which dominate the cost of a 40m ELT. For the same cost, an "Extremely Large Hyper Telescope” ( ELHyT) may therefore have a larger collecting area. It may thus in principle reach higher limiting magnitudes, both for seeing-limited and, if equipped with a Laser Guide Star and adaptive phasing, for high-resolution imaging with gain as the size ratio, i.e. about 30 with respect to a 40m ELT. Like the radio arrays of antennas, such instruments can be grown progressively. Also, they can be up-graded with several focal gondolas, independently tracking different sources. Candidate sites have been identified in the Himalaya and the Andes. We describe several design options and compare the science achievable for both instruments, ELTs and ELHyTs. The broad science addressed by an ELHyT covers stellar chromospheres, transiting exoplanets and those requiring a high dynamic range, achieved by array apodization or coronagraphy. With a Laser Guide Star, it extends to faint compact sources beyond the limits of telescopes having a smaller collecting area, supernovae, active galactic nuclei, gamma ray bursts. The sparse content of remote galaxies seen in the Hubble Deep Field appears compatible with the crowding limitations of an ELHyT having 1000 apertures.

  2. Towards predicting the laser damage threshold of large-area optics

    SciTech Connect

    Hue, J. [CEA Centre d`Etudes Nucleaires de Grenoble, 38 (France). Lab. d`Electronique et de Technologie de l`Informatique; Genin, F.Y.; Maricle, S.M.; Kozlowski, M.R. [Lawrence Livermore National Lab., CA (United States)

    1996-10-01

    As the size of optics increases, such as in the optical coatings being developed for the National Ignition Facility in US and the Laser MegaJoules in France, the difficulty also increases in measuring and defining their laser damage threshold. Measuring the threshold on small witness samples ({le}cm) rather than full aperture optic (=m) is advantageous, and in this article, the threshold of large-area components is addressed in two ways. First, a model based on the R-on-l threshold distribution is shown to predict the threshold of a large optic with a high degree of confidence. The average R-on-l threshold provides a reliable, accurate value to evaluate coatings. An automated damage test bench has been developed at CEA. Secondly, the damage threshold has to be defined according to final use of the component. LLNL has defined a functional damage threshold to set limits on maximum damage size. An empirical power law dependence of average damage size on peak fluence was found; this can be used to predict the damage behavior of large-aperture optics exhibiting the same damage morphology.

  3. Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

    NASA Technical Reports Server (NTRS)

    Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

    1991-01-01

    The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

  4. The Advanced Technology Large Aperture Space Telescope (ATLAST): Science Drivers, Technology Developments, and Synergies with Other Future Facilities

    NASA Technical Reports Server (NTRS)

    Postman, Marc; Brown, Tom; Sembach, Kenneth; Giavalisco, Mauro; Traub, Wesley; Stapelfeldt, Karl; Calzetti, Daniela; Oegerle, William; Rich, R. Michael; Stahl, H. Phillip; Tumlinson, Jason; Mountain, Matt; Soummer, Remi; Hyde, Tupper

    2011-01-01

    The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a concept for an 8-meter to 16-meter UVOIR space observatory for launch in the 2025-2030 era. ATLAST will allow astronomers to answer fundamental questions at the forefront of modern astrophysics, including "Is there life elsewhere in the Galaxy?" We present a range of science drivers that define the main performance requirements for ATLAST (8 to 16 milliarcsec angular resolution, diffraction limited imaging at 0.5 m wavelength, minimum collecting area of 45 square meters, high sensitivity to light wavelengths from 0.1 m to 2.4 m, high stability in wavefront sensing and control). We will also discuss the synergy between ATLAST and other anticipated future facilities (e.g., TMT, EELT, ALMA) and the priorities for technology development that will enable the construction for a cost that is comparable to current generation observatory-class space missions.

  5. Mechanical and optical analysis of large-aperture optics mounted on a frame with a curved surface

    NASA Astrophysics Data System (ADS)

    Su, Ruifeng; Liu, Haitao; Liang, Yingchun; Lu, Lihua; Sun, Fuzhong; Cao, Yongzhi

    2014-03-01

    Motivated by the need to decrease gravitational sag and stress and increase the frequency conversion efficiency of large-aperture optics, a novel mounting configuration in which a set of optics is mechanically mounted to a frame with a curved surface was developed and mechanically and optically analyzed. The effects of an external load on distortion, stress and the induced frequency conversion efficiency were studied, and the changes in these values with varying external load were assessed to determine the optimum mounting configuration. Additionally, the effects of the frame surface topography on distortion, stress and the induced frequency conversion efficiency were studied. The optimum values for distortion, stress and the induced frequency conversion efficiency were determined for different topographies.

  6. Mg-doped congruent LiTaO3 crystal for large-aperture quasi-phase matching device.

    PubMed

    Ishizuki, Hideki; Taira, Takunori

    2008-10-13

    Mg-doped congruent composition LiTaO(3) (MgLT) crystal, which can be grown by a conventional Czochralski method, has improved properties such as transparent range, thermal conductivity, and coercive field compared to conventional undoped congruent LiTaO(3). In this paper, various properties of MgLT including Mg-doping dependence are characterized, and also compared to that of undoped congruent LiTaO(3), LiNbO(3), and Mg-doped congruent LiNbO(3), as a material of high power quasi-phase matching (QPM) device. Up to 3-mm-thick periodically poled MgLT crystal is shown to demonstrate the possibility of large-aperture QPM-MgLT devices. Subsequently, optical parametric oscillation experiments by using periodically poled MgLT are demonstrated to discuss an efficient QPM condition. PMID:18852804

  7. Subwavelength-thick lenses with high numerical apertures and large efficiency based on high-contrast transmitarrays.

    PubMed

    Arbabi, Amir; Horie, Yu; Ball, Alexander J; Bagheri, Mahmood; Faraon, Andrei

    2015-01-01

    Flat optical devices thinner than a wavelength promise to replace conventional free-space components for wavefront and polarization control. Transmissive flat lenses are particularly interesting for applications in imaging and on-chip optoelectronic integration. Several designs based on plasmonic metasurfaces, high-contrast transmitarrays and gratings have been recently implemented but have not provided a performance comparable to conventional curved lenses. Here we report polarization-insensitive, micron-thick, high-contrast transmitarray micro-lenses with focal spots as small as 0.57??. The measured focusing efficiency is up to 82%. A rigorous method for ultrathin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The micro-lenses, composed of silicon nano-posts on glass, are fabricated in one lithographic step that could be performed with high-throughput photo or nanoimprint lithography, thus enabling widespread adoption. PMID:25947118

  8. Average patterns and coherent phenomena in wide aperture lasers G. D'Alessandro

    E-print Network

    Louvergneaux, Eric

    the physical processes involved in the emission of light. Moreover, average patterns are "robust," in the sense [1­3] and solid state micro- chip lasers [4] are strikingly similar despite the differences between the instantaneous intensity patterns are not generally measurable due to the fast time scales of the dynamics

  9. Laser aperture diagnostics system for gain and wavefront measurements on NIF\\/LMJ amplifiers

    Microsoft Academic Search

    1996-01-01

    We are in the midst of constructing an amplifier laboratory (Arnplab) that will be the physics and engineering proving ground for fill sized segmented glass amplifiers of designs that will outfit the National Ignition Facility (NIF) and Laser Megajoule (LMJ) projects. Amplab will demonstrate the cornerstone mechanical, electrical and optical concepts that support the NW and LMJ amplifier schemes. Here

  10. Measurement of wavefront structure from large-aperture optical components by phase-shifting interferometry

    NASA Astrophysics Data System (ADS)

    Wolfe, C. Robert; Lawson, Janice K.; Kellam, Marcia C.; Maney, Richard T.; Demiris, Anthony

    1995-09-01

    This paper discusses the results of high spatial resolution measurement of the transmitted or reflected wavefront of optical components using phase shifting interferometry with a wavelength of 6328 angstrom. The optical components studied range in size from approximately 50 mm X 100 mm to 400 mm X 750 mm. Wavefront data, in the form of 3D phase maps, have been obtained for three regimes of scale length: 'micro roughness', 'mid-spatial scale', and 'optical figure/curvature'. Repetitive wavefront structure has been observed with scale lengths from 10 mm to 100 mm. The amplitude of this structure is typically 1/100 to 1/20. Previously unobserved structure has been detected in optical materials and on the surfaces of components. We are using this data to assist in optimizing laser system design, to qualify optical components and fabrication processes under study in our component development program.

  11. High-resolution adaptive optics scanning laser ophthalmoscope with dual deformable mirrors for large aberration correction

    SciTech Connect

    Chen, D; Jones, S M; Silva, D A; Olivier, S S

    2007-01-25

    Scanning laser ophthalmoscopes with adaptive optics (AOSLO) have been shown previously to provide a noninvasive, cellular-scale view of the living human retina. However, the clinical utility of these systems has been limited by the available deformable mirror technology. In this paper, we demonstrate that the use of dual deformable mirrors can effectively compensate large aberrations in the human retina, making the AOSLO system a viable, non-invasive, high-resolution imaging tool for clinical diagnostics. We used a bimorph deformable mirror to correct low-order aberrations with relatively large amplitudes. The bimorph mirror is manufactured by Aoptix, Inc. with 37 elements and 18 {micro}m stroke in a 10 mm aperture. We used a MEMS deformable mirror to correct high-order aberrations with lower amplitudes. The MEMS mirror is manufactured by Boston Micromachine, Inc with 144 elements and 1.5 {micro}m stroke in a 3 mm aperture. We have achieved near diffraction-limited retina images using the dual deformable mirrors to correct large aberrations up to {+-} 3D of defocus and {+-} 3D of cylindrical aberrations with test subjects. This increases the range of spectacle corrections by the AO systems by a factor of 10, which is crucial for use in the clinical environment. This ability for large phase compensation can eliminate accurate refractive error fitting for the patients, which greatly improves the system ease of use and efficiency in the clinical environment.

  12. Preliminary evaluation of sensible heat flux measurements from a large aperture scintillometer using lysimetric data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The path integrating capabilities of scintillometers over several kilometers make it a potential tool that can bridge the gap between primary point based observations (lysimeters, Bowen ratio, or eddy covariance) and the demand for large-scale spatially averaged surface fluxes. Further, the spatial...

  13. Large-aperture continuous-phase diffractive optical element for beam transform

    Microsoft Academic Search

    Qiaofeng Tan; Yingbai Yan; Guofan Jin; Minxian Wu

    1999-01-01

    Beam transform, such as to obtain uniform focal spot with flat top, steep edge, low side lobes and high light efficiency, can be realized well by diffractive optical element (DOE). The DOE has many advantages, such as high light efficiency and strong phase distribution design flexibility. To increase the light efficiency and decrease large-angle scattering, continuous phase DOE should be

  14. New technologies for the actuation and controls of large aperture lightweight quality mirrors

    NASA Technical Reports Server (NTRS)

    Lih, S. S.; Yang, E. H.; Gullapalli, S. N.; Flood, R.

    2003-01-01

    This paper presents a set of candidate components: MEMS based large stroke (>100 microns) ultra lightweight (0.01 gm) discrete inch worm actuator technology, and a distributed actuator technology, in the context of a novel lightweight active flexure-hinged substrate concept that uses the nanolaminate face sheet.

  15. A test of basin-scale acoustic thermometry using a large-aperture vertical array at 3250-km range in the eastern

    E-print Network

    deYoung, Brad

    -axial acoustic reception ends, used as a surrogate for the group delay of adiabatic mode 1. The changeA test of basin-scale acoustic thermometry using a large- aperture vertical array at 3250-km range November 1997; revised 14 January 1999; accepted 5 March 1999 Broadband acoustic signals were transmitted

  16. Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry

    NASA Astrophysics Data System (ADS)

    Matthews, Tristan G.; Ade, Peter A. R.; Angilè, Francesco E.; Benton, Steven J.; Chapin, Edward L.; Chapman, Nicholas L.; Devlin, Mark J.; Fissel, Laura M.; Fukui, Yasuo; Gandilo, Natalie N.; Gundersen, Joshua O.; Hargrave, Peter C.; Klein, Jeffrey; Korotkov, Andrei L.; Moncelsi, Lorenzo; Mroczkowski, Tony K.; Netterfield, Calvin B.; Novak, Giles; Nutter, David; Olmi, Luca; Pascale, Enzo; Poidevin, Frédérick; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A.; Soler, Juan Diego; Tachihara, Kengo; Thomas, Nicholas E.; Truch, Matthew D. P.; Tucker, Carole E.; Tucker, Gregory S.; Ward-Thompson, Derek

    2014-04-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 ?m. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  17. PISCES: A Wide-Field, 1-2.5 mum Camera for Large-Aperture Telescopes

    Microsoft Academic Search

    D. W. McCarthy Jr.; J. Ge; J. L. Hinz; R. A. Finn; R. S. de Jong

    2001-01-01

    Wide-field-of-view infrared cameras, operating on the new generation of large telescopes, offer unprecedented gains in the detection of faint sources and in observing efficiency for both direct imaging and spectroscopy. With a 1024×1024 pixel, 1-2.5 mum detector, the PISCES camera provides 8.5' and 3.16' fields at the 2.3 m Bok telescope and 6.5 m Multiple Mirror Telescope, respectively. Its refractive

  18. Diagnostic systems for power balancing large laser fusion facilities

    Microsoft Academic Search

    Guangyu Chen; Xiaomin Zhang; Runchang Zhao

    2009-01-01

    Multiple powerful lasers are shot from large laser fusion facilities synchronously to heat and compress hydrogen fuel to the point where nuclear fusion reactions take place, with the goal of ignition. When the fusion reactions become self-sustaining and controllable, they will provide new clean energy to human beings. Shot reliability is a performance measure of large, multiple beam, power balanced,

  19. A 16-m Telescope for the Advanced Technology Large Aperture Telescope (ATLAST) Mission

    NASA Astrophysics Data System (ADS)

    Lillie, Charles F.; Dailey, D. R.; Polidan, R. S.

    2010-01-01

    Future space observatories will require increasingly large telescopes to study the earliest stars and galaxies, as well as faint nearby objects. Technologies now under development will enable telescopes much larger than the 6.5-meter diameter James Webb Space Telescope (JWST) to be developed at comparable costs. Current segmented mirror and deployable optics technology enables the 6.5 meter JWST telescope to be folded for launch in the 5-meter diameter Ariane 5 payload fairing, and deployed autonomously after reaching orbit. Late in the next decade, when the Ares V Cargo Launch Vehicle payload fairing becomes operational, even larger telescope can be placed in orbit. In this paper we present our concept for a 16-meter JWST derivative, chord-fold telescope which could be stowed in the 10-m diameter Ares V fairing, plus a description of the new technologies that enable ATLAST to be developed at an affordable price.

  20. Measurements of evapotranspiration from eddy-covariance systems and large aperture scintillometers in the Hai River Basin, China

    NASA Astrophysics Data System (ADS)

    Liu, S. M.; Xu, Z. W.; Zhu, Z. L.; Jia, Z. Z.; Zhu, M. J.

    2013-04-01

    SummaryEvapotranspiration (ET) observations were made for 3 years (2008-2010), using eddy covariance (EC) systems and large aperture scintillometers (LAS), in typical underlying surfaces across the Hai River Basin: orchards (Miyun, MY), cropland in the suburbs (Daxing, DX), and cropland in the plains (Guantao, GT). Reliable data were obtained after carefully data processing, and the seasonal and interannual variability in ET was quantitatively analyzed. The annual ET during 2008-2010 ranged from 510-730 mm for the EC measurements and 430-560 mm for the LAS measurements. The differences in ET among the years and sites were connected with differences in soil moisture and crop growing conditions. The difference in the source areas of EC and LAS measurements and the heterogeneity in their source areas are the primary causes of the discrepancy between EC and LAS measurements. The EC and LAS measurements are compared to the field water balance method calculation and MOD16 ET (the MODIS ET product from the MODIS Global Evapotranspiration Project), respectively. The average difference was 0.85% (mean relative error) and 33.80 mm (root mean square error) between the EC measurements and field water balance method calculations, and 7.72% and 47.08 mm between LAS measurements and MOD16 ET from 2008 to 2010 at the three sites. We found a decreasing tendency for ET in the past 15 years across the Hai River Basin, especially after the year of 2005.

  1. Lupus I Observations from the 2010 Flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry

    E-print Network

    Matthews, Tristan G; Angilè, Francesco E; Benton, Steven J; Chapin, Edward L; Chapman, Nicholas L; Devlin, Mark J; Fissel, Laura M; Fukui, Yasuo; Gandilo, Natalie N; Gundersen, Joshua O; Hargrave, Peter C; Klein, Jeffrey; Korotkov, Andrei L; Moncelsi, Lorenzo; Mroczkowski, Tony K; Netterfield, Calvin B; Novak, Giles; Nutter, David; Olmi, Luca; Pascale, Enzo; Poidevin, Frédérick; Savini, Giorgio; Scott, Douglas; Shariff, Jamil A; Soler, Juan Diego; Tachihara, Kengo; Thomas, Nicholas E; Truch, Matthew D P; Tucker, Carole E; Tucker, Gregory S; Ward-Thompson, Derek

    2013-01-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 {\\mu}m. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry (The optical data were published in 1998 by J. Rizzo and collaborators.). The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I,...

  2. Numerical aperture limits on efficient ball lens coupling of laser diodes to single-mode fibers with defocus to balance spherical aberration

    NASA Technical Reports Server (NTRS)

    Wilson, R. Gale

    1994-01-01

    The potential capabilities and limitations of single ball lenses for coupling laser diode radiation to single-mode optical fibers have been analyzed; parameters important to optical communications were specifically considered. These parameters included coupling efficiency, effective numerical apertures, lens radius, lens refractive index, wavelength, magnification in imaging the laser diode on the fiber, and defocus to counterbalance spherical aberration of the lens. Limiting numerical apertures in object and image space were determined under the constraint that the lens perform to the Rayleigh criterion of 0.25-wavelength (Strehl ratio = 0.80). The spherical aberration-defocus balance to provide an optical path difference of 0.25 wavelength units was shown to define a constant coupling efficiency (i.e., 0.56). The relative numerical aperture capabilities of the ball lens were determined for a set of wavelengths and associated fiber-core diameters of particular interest for single-mode fiber-optic communication. The results support general continuing efforts in the optical fiber communications industry to improve coupling links within such systems with emphasis on manufacturing simplicity, system packaging flexibility, relaxation of assembly alignment tolerances, cost reduction of opto-electronic components and long term reliability and stability.

  3. Large area electron beam pumped krypton fluoride laser amplifier

    SciTech Connect

    Sethian, J.D.; Obenschain, S.P.; Gerber, K.A.; Pawley, C.J.; Serlin, V.; Sullivan, C.A. [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States)] [Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 (United States); Webster, W. [Research Support Instruments, 4325-B Forbes Boulevard, Lanham, Maryland 20706 (United States)] [Research Support Instruments, 4325-B Forbes Boulevard, Lanham, Maryland 20706 (United States); Deniz, A.V.; Lehecka, T. [Science Applications International Corporation, 1710 Goodridge Drive, McLean, Virginia 22102 (United States)] [Science Applications International Corporation, 1710 Goodridge Drive, McLean, Virginia 22102 (United States); McGeoch, M.W. [PLEX Corporation, 21 Addington Road, Brookline, Massachusetts 02146 (United States)] [PLEX Corporation, 21 Addington Road, Brookline, Massachusetts 02146 (United States); Altes, R.A.; Corcoran, P.A.; Smith, I.D. [Pulse Sciences, Incorporated, 600 McCormick Street, San Leandro, California 94577 (United States)] [Pulse Sciences, Incorporated, 600 McCormick Street, San Leandro, California 94577 (United States); Barr, O.C. [Pharos Technical Enterprises, 1603 Barcelona Street, Livermore, California 94550 (United States)] [Pharos Technical Enterprises, 1603 Barcelona Street, Livermore, California 94550 (United States)

    1997-06-01

    Nike is a recently completed multi-kilojoule krypton fluoride (KrF) laser that has been built to study the physics of direct drive inertial confinement fusion. This paper describes in detail both the pulsed power and optical performance of the largest amplifier in the Nike laser, the 60 cm amplifier. This is a double pass, double sided, electron beam-pumped system that amplifies the laser beam from an input of 50 J to an output of up to 5 kJ. It has an optical aperture of 60 cm {times} 60 cm and a gain length of 200 cm. The two electron beams are 60 cm high {times} 200 cm wide, have a voltage of 640 kV, a current of 540 kA, and a flat top power pulse duration of 250 ns. A 2 kG magnetic field is used to guide the beams and prevent self-pinching. Each electron beam is produced by its own Marx/pulse forming line system. The amplifier has been fully integrated into the Nike system and is used on a daily basis for laser-target experiments. {copyright} {ital 1997 American Institute of Physics.}

  4. Determining meteoroid bulk densities using a plasma scattering model with high-power large-aperture radar data

    NASA Astrophysics Data System (ADS)

    Close, Sigrid; Volz, Ryan; Loveland, Rohan; Macdonell, Alex; Colestock, Patrick; Linscott, Ivan; Oppenheim, Meers

    2012-09-01

    We present an improved technique for calculating bulk densities of low-mass (<1 g) meteoroids using a scattering model applied to the high-density plasma formed around the meteoroid as it enters Earth’s atmosphere. These plasmas, referred to as head echoes, travel at or near the speed of the meteoroid, thereby allowing the determination of the ballistic coefficient (mass divided by physical cross-section), which depends upon speed and deceleration. Concurrently, we apply a scattering model to the returned signal strength of the head echo in order to correlate radar-cross-section (RCS) to plasma density and meteoroid mass. In this way, we can uniquely solve for the meteoroid mass, radius and bulk density independently. We have applied this new technique to head echo data collected in 2007 and 2008 simultaneously at VHF (160 MHz) and UHF (422 MHz) at ALTAIR, which is a high-power large-aperture radar located on the Kwajalein Atoll. These data include approximately 20,000 detections with dual-frequency, dual-polarization, and monopulse (i.e. angle) returns. From 2000 detections with the smallest monopulse errors, we find a mean meteoroid bulk density of 0.9 g/cm3 with observations spanning almost three orders of magnitude from 0.01 g/cm3 to 8 g/cm3. Our results show a clear dependence between meteoroid bulk density and altitude of head echo formation, as well as dependence between meteoroid bulk density and 3D speed. The highest bulk densities are detected at the lowest altitudes and lowest speeds. Additionally, we stipulate that the approximations used to derive the ballistic parameter, in addition to neglecting fragmentation, suggest that the traditional ballistic parameter must be used with caution when determining meteoroid parameters.

  5. Single mode PT symmetric large area lasers

    NASA Astrophysics Data System (ADS)

    Hodaei, Hossein; Miri, Mohammad-Ali; Heinrich, Matthias; Christodoulides, Demetrios N.; Khajavikhan, Mercedeh

    2014-09-01

    We experimentally demonstrate single longitudinal mode operation in microring laser using the concept of PT symmetry. A PT-symmetric coupled resonator arrangement can considerably enhance the maximum achievable gain of single mode microring cavity. The method is broadband thus work well for inhomogenously broadened gain mediums. It doesn't rely on any additional component to ensure its mode selective performance, and it is robust with respect to fabrication inaccuracies. This result may pave the way for a novel way of designing integrated laser sources based on PT symmetry.

  6. Large mode-volume, large beta, photonic crystal laser resonator

    SciTech Connect

    Dezfouli, Mohsen Kamandar; Dignam, Marc M. [Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, ON K7L 3N6 (Canada)

    2014-12-15

    We propose an optical resonator formed from the coupling of 13, L2 defects in a triangular-lattice photonic crystal slab. Using a tight-binding formalism, we optimized the coupled-defect cavity design to obtain a resonator with predicted single-mode operation, a mode volume five times that of an L2-cavity mode and a beta factor of 0.39. The results are confirmed using finite-difference time domain simulations. This resonator is very promising for use as a single mode photonic crystal vertical-cavity surface-emitting laser with high saturation output power compared to a laser consisting of one of the single-defect cavities.

  7. [Transurethral noncontact laser ablation of the large prostate].

    PubMed

    Xue, J; Zhuang, H; Wang, J

    1996-08-01

    42 cases of the large benign hypertrophy of the prostate were treated by transurethral noncontact laser ablation. The results of the patients followed up no less than six months and treatment were reported. The technique of the procedure and its related problems were described and our experience was presented. If we use the technique of the procedure skill fully, noncontact laser ablation of large benign hypertrophy of the prostate is safe and effective. PMID:9594203

  8. Design and prototype tests of a large-aperture 37-53 MHz ferrite-tuned booster synchrotron cavity

    SciTech Connect

    Mark S. Champion et al.

    2001-07-12

    The Booster synchrotron at Fermilab employs eighteen 37-53 MHz ferrite-tuned double-gap coaxial radiofrequency cavities for acceleration of protons from 400 MeV to 8 GeV. The cavities have an aperture of 2.25 inches and operate at 55 kV per cavity. Future high duty factor operation of the Booster will be problematic due to unavoidable beam loss at the cavities resulting in excessive activation. The power amplifiers, high maintenance items, are mounted directly to the cavities in the tunnel. A proposed replacement for the Booster, the Proton Driver, will utilize the Booster radiofrequency cavities and requires not only a larger aperture, but also higher voltage. A research and development program is underway at Fermilab to modify the Booster cavities to provide a 5-inch aperture and a 20% voltage increase. A prototype has been constructed and high power tests have bee completed. The cavity design and test results is presented.

  9. A comparison of detection sensitivity between ALTAIR and Arecibo meteor observations: Can high power and large aperture radars detect low velocity meteor head-echoes

    Microsoft Academic Search

    Diego Janches; Sigrid Close; Jonathan T. Fentzke

    2008-01-01

    Meteor head-echo observations using High Power and Large Aperture (HPLA) radars have been routinely used for micrometeor studies for over a decade. The head-echo is a signal from the radar-reflective plasma region traveling with the meteoroid and its detection allows for very precise determination of instantaneous meteor altitude, velocity and deceleration. Unlike specular meteor radars (SMR), HPLA radars are diverse

  10. Evolution of ultrashort laser pulse in large amplitude plasma waves

    SciTech Connect

    Bu Zhigang [Department of Physics, Shanghai University, Shanghai 200444 (China); Ji Peiyong [Department of Physics, Shanghai University, Shanghai 200444 (China); The Shanghai Key Lab of Astrophysics, Shanghai 200234 (China)

    2012-11-15

    The propagation and evolution of an ultrashort laser pulse in a large amplitude plasma wave are investigated based on the photon kinetic theory. The photon number distribution function for a laser pulse in the phase space is analytically obtained by solving the photon kinetic equation in the background plasma wave. And then, the behavior of the laser pulse can be described by combining the single photon dynamics and the photon number distribution function. The evolutions of the photon number density in the coordinate and frequency domain space are discussed, and broadening or compressing of the laser pulse is also displayed in this paper. In particular, the frequency shift of the entire laser pulse is analyzed, which reflects a way of energy transformation between the laser pulse and the plasma wave.

  11. Study of 2-in1 large-aperture Nb3Sn IR quadrupoles for the LHC luminosity upgrade

    SciTech Connect

    Kashikhin, V.V.; Zlobin, A.V.; /Fermilab

    2006-06-01

    Double-aperture Nb{sub 3}Sn quadrupoles with asymmetric coils and with cold and warm iron yokes were studied for the dipole-first upgrade scenario of the LHC Interaction Regions (IR). This paper describes the magnet design concepts and discusses their performance parameters, including field gradient and field quality limitations.

  12. Laser processing system development of large area and high precision

    NASA Astrophysics Data System (ADS)

    Park, Hyeongchan; Ryu, Kwanghyun; Hwang, Taesang

    2013-03-01

    As industry of PCB (Printed Circuit Board) and display growing, this industry requires an increasingly high-precision quality so current cutting process in industry is preferred laser machining than mechanical machining. Now, laser machining is used almost "step and repeat" method in large area, but this method has a problem such as cutting quality in the continuity of edge parts, cutting speed and low productivity. To solve these problems in large area, on-the-fly (stagescanner synchronized system) is gradually increasing. On-the-fly technology is able to process large area with high speed because of stage-scanner synchronized moving. We designed laser-based high precision system with on-the-fly. In this system, we used UV nano-second pulse laser, power controller and scanner with telecentric f-theta lens. The power controller is consisted of HWP(Half Wave Plate), thin film plate polarizer, photo diode, micro step motor and control board. Laser power is possible to monitor real-time and adjust precision power by using power controller. Using this machine, we tested cutting of large area coverlay and sheet type large area PCB by applying on-the-fly. As a result, our developed machine is possible to process large area without the problem of the continuity of edge parts and by high cutting speed than competitor about coverlay.

  13. Large-aperture phosphate-neodymium-glass rod amplifiers for lasers with high radiation intensity

    NASA Astrophysics Data System (ADS)

    Baianov, V. I.; Bordachev, E. G.; Volynkin, V. M.; Kryzhanovskii, V. I.; Mak, A. A.

    1986-09-01

    The paper studies the amplifying and thermooptical parameters of rod amplifiers which use improved phosphate neodymium glass 85 and 100 mm in diameter. The effect of the number of lamps, the pumping pulse duration, the illuminator, and the neodymium ion concentration on the gain, its distribution over the active element cross section, and the amplifier efficiency is studied. Gains of 0.068 and 0.05/cm respectively were obtained.

  14. Phased-array electro-optic steering of large aperture laser beams using ferroelectrics

    E-print Network

    Gopalan, Venkatraman

    micropatterned scanner device with 13 beamlet channels was fabricated in LiTaO3 and was demonstrated to deflect-optic scanning using ferroelec- tric domain prisms10 is as follows: In LiNbO3 and LiTaO3 ferroelectric crystals

  15. Large-Aperture [O I] 6300 A Photometry of Comet Hale-Bopp: Implications for the Photochemistry of OH

    NASA Technical Reports Server (NTRS)

    Morgenthaler, Jeffrey P.; Harris, Walter M.; Scherb, Frank; Anderson, Christopher M.; Oliversen, Ronald J.; Doane, Nathaniel E.; Combi, Michael R.; Marconi, Maximus L.; Smyth, William H.

    2001-01-01

    Large-aperture photometric observations of comet Hale-Bopp (C/1995 O1) in the forbidden red line of neutral oxygen ([O I] 6300 angstroms) with the 150 mm dual-etalon Fabry-Perot spectrometer that comprises the Wisconsin H-alpha Mapper and a 50 mm dual-etalon Fabry-Perot spectrometer at the McMath-Pierce main telescope from 1997 late February to mid April yield a total metastable O((sup 1)D) production rate of (2.3-5.9) x 10(exp 30)/s. Applying the standard H2O and OH photodissociation branching ratios, we derive a water production rate, Q(H2O), of (2.6-6.1) x 10(exp 31)/s, which disagrees with Q(H2O = 1x10(exp 31)/s determined by independent H2O, OH, and H measurements. Furthermore, our own [O I] 6300 observations of the inner coma (< 30,000 km) using the 3.5 m Wisconsin-Indiana-Yale-NOAO telescope Hydra and Densepak multi-object spectrographs yield Q(H2O) = 1 x 10(exp 31)/s. Using our [O I] 6300 data, which cover spatial scales ranging from 2,000 to 1x10(exp 6) km, and a complementary set of wide-field ground-based OH images, we can constrain the sources of the apparent excess O((sup 1)D) emission to the outer coma, where photodissociation of OH is assumed to be the dominant O((sup 1)D) production mechanism. From production rates of other oxygen-bearing volatiles (e.g., CO and CO2), we can account for at most 30% of the observed excess O((sup 1)D) emission. Since even less O((sup 1)D) should be coming from other sources (e.g., electron excitation of neutral O and distributed nonnuclear sources of H2O), we hypothesize that the bulk of the excess O((sup 1)D) is likely coming from photodissociating OH. Using the experimental OH photo-dissociation cross section of Nee and Lee at Ly-alpha as a guide in modifying the theoretical OH cross sections of van Dishoeck and Dalgarno, we can account for approximately 60% of the observed O((sup 1)D) excess without requiring major modifications to the other OH branching ratios or the total OH photodissociation lifetime.

  16. Combining Measurements with Three-Dimensional Laser Scanning System and Coded Aperture Gamma-Ray Imaging Systems for International Safeguards Applications

    SciTech Connect

    Boehnen, Chris Bensing [ORNL] [ORNL; Bogard, James S [ORNL] [ORNL; Hayward, Jason P [ORNL] [ORNL; Raffo-Caiado, Ana Claudia [ORNL] [ORNL; Smith, Stephen E [ORNL] [ORNL; Ziock, Klaus-Peter [ORNL] [ORNL

    2010-01-01

    Being able to verify the operator's declaration in regards to technical design of nuclear facilities is an important aspect of every safeguards approach. In addition to visual observation, it is relevant to know if nuclear material is present or has been present in piping and ducts not declared. The possibility of combining different measurement techniques into one tool should optimize the inspection effort and increase safeguards effectiveness. Oak Ridge National Laboratory (ORNL) is engaged in a technical collaboration project involving two U.S. Department of Energy foreign partners to investigate combining measurements from a three-dimensional (3D) laser scanning system and gamma-ray imaging systems. ORNL conducted simultaneous measurements with a coded-aperture gamma-ray imager and the 3D laser scanner in an operational facility with complex configuration and different enrichment levels and quantities of uranium. This paper describes these measurements and their results.

  17. Large-aperture CCD x-ray detector for protein crystallography using a fiber-optic taper

    Microsoft Academic Search

    Michael G. Strauss; Edwin M. Westbrook; Istvan Naday; T. A. Coleman; Mary L. Westbrook; D. J. Travis; Robert M. Sweet; J. W. Pflugrath; Martin J. Stanton

    1991-01-01

    A detector with a 114 mm aperture, based on a charge-coupled device (CCD), has been designed for x-ray diffraction studies in protein crystallography. The detector was tested on a beamline of the National Synchrotron Light Source at Brookhaven National Laboratory with a beam intensity greater than 10(superscript 9) x-ray photons\\/s. A fiber-optic taper, an image intensifier, and a lens demagnify,

  18. New technologies and architectures for laser systems: revolutionary beam control (Keynote Address)

    NASA Astrophysics Data System (ADS)

    McManamon, Paul F.; Thompson, William E.

    2004-09-01

    This paper discusses revolutionary laser system architecture capable of dramatically reducing the complexity of laser systems while increasing capability. The architecture includes 3 major subsystems. The first is a phased array of laser sources. The second provides wavefront control and electronic beam steering. The third is sub-aperture receiver technology. Combining these three technologies into a new laser systems architecture results in a system that has graceful degradation, can steer to as wide an angle as individual optical phased array sub-apertures can steer, and can be scaled to high power and large apertures through phasing of a number of sub-apertures.

  19. Comparison between C band synthetic aperture radar and 3-D laser scanner statistics for the Baltic Sea ice

    Microsoft Academic Search

    M. Similä; M. Mäkynen; I. Heiler

    2010-01-01

    A statistical analysis was performed for nearly simultaneously acquired C band synthetic aperture radar (SAR) images and ice freeboard statistics. The data analyzed were collected during a CryoSat calibration-validation campaign in March 2005 in the Baltic Sea. The 3-D ice freeboard topography along transects with a total length about 150 km and width of 300 m was constructed from cross-track

  20. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: A wide-aperture Pockels cell with three ring electrodes

    Microsoft Academic Search

    N. F. Andreev; V. I. Bespalov; V. I. Bredikhin; Sergey G. Garanin; V. S. Davydov; Yu V. Dolgopolov; E. V. Katin; S. P. Kuznetsov; S. M. Kulikov; A. Z. Matveev; V. I. Rubakha; Stanislav A. Sukharev

    2004-01-01

    A wide-aperture Pockels cell based on a DKDP crystal having an optical diameter of 70 mm is studied. Three silver ring electrodes deposited on the side surface of the crystal were used to apply a high-voltage rectangular pulse of variable duration from 50 to 150 ns to the cell. Chains of KT6117A (2N5551) transistors operating in the avalanche regime served

  1. Synthetic aperture radiometer systems

    Microsoft Academic Search

    David M. Le Vine

    1999-01-01

    Aperture synthesis is an emerging technology for passive microwave remote sensing from space. It is an interferometric technique similar to earth rotation synthesis employed in radio astronomy in which pairs of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has the potential to overcome the barriers that antenna size has

  2. Large-screen projection displays with laser brightness amplifiers

    NASA Astrophysics Data System (ADS)

    Petrash, Gueorgii G.; Chvykov, Vladimir V.; Zemskov, Konstantin I.

    1997-05-01

    One of the most difficult problems of large-screen projection displays is overloading of a panel to be projected with illuminating light. The problem can be solved by using, on the way from a panel to be projected to a screen, an optical amplifier with high enough amplification. The prospects of using laser amplifiers in projection displays are discussed. Among all laser amplifiers the most suitable for application as optical amplifiers in projection systems are now pulsed metal vapor laser and metal halide laser amplifiers. They have rather high gain enabling amplification in the range from 102 to 104 and high average output power sufficient to illuminate a large screen. The main characteristics of these amplifiers are described. The results of experimental investigations of projection systems with copper, copper bromide, gold and some other metal vapor amplifiers are reported. In all cases good quality amplified images were obtained. Average power at the output of amplifiers was under typical conditions of operation comparable with the output power of a laser with the same amplifying element. Measurement of contrast of amplified images showed that under normal conditions of operation it is close to the contrast of the input picture even at strong saturation of the amplifying medium. The influence of the amplifier saturation is briefly discussed. The results of experiments with TV projection systems using two types of liquid crystal spatial light modulators are presented and prospects of large-screen projection displays development are discussed.

  3. A study program on large aperture electronic scanning phased array antennas for the shuttle imaging microwave system

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Fundamental phased array theory and performance parameters are discussed in terms of their application to microwave radiometry, and four scanning phased arrays representing current examples of state-of-the-art phased array technology are evaluated for potential use as components of the multispectral antenna system for the space shuttle imaging microwave system (SIMS). A discussion of problem areas, both in performance and fabrication is included, with extrapolations of performance characteristics for phased array antennas of increased sizes up to 20 m by 20 m. The possibility of interlacing two or more phased arrays to achieve a multifrequency aperture is considered, and, finally, a specific antenna system is recommended for use with SIMS.

  4. Laser-Induced Production of Large Carbon-Based Toriods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We report on the production of large carbon-based toroids (CBTs) from fullerencs. The process involves two step laser irradiation of a mixed fullcrene target (76% C-60, 22% C-70). Transmission electron microscopy (11M) clearly identifies toroidal-shaped structures as well as Q-shaped constructs. ...

  5. Laser Welding of Large Scale Stainless Steel Aircraft Structures

    NASA Astrophysics Data System (ADS)

    Reitemeyer, D.; Schultz, V.; Syassen, F.; Seefeld, T.; Vollertsen, F.

    In this paper a welding process for large scale stainless steel structures is presented. The process was developed according to the requirements of an aircraft application. Therefore, stringers are welded on a skin sheet in a t-joint configuration. The 0.6 mm thickness parts are welded with a thin disc laser, seam length up to 1920 mm are demonstrated. The welding process causes angular distortions of the skin sheet which are compensated by a subsequent laser straightening process. Based on a model straightening process parameters matching the induced welding distortion are predicted. The process combination is successfully applied to stringer stiffened specimens.

  6. Laser scanning system for inspecting large underwater hydroelectric structures

    NASA Astrophysics Data System (ADS)

    Mirallès, François; Beaudry, Julien; Blain, Michel; de Santis, Romano M.; Houde, Régis; Hurteau, Richard; Robert, André; Sarraillon, Serge; Soucy, Nathalie

    2010-04-01

    A novel robotic laser scanning system for the inspection of large underwater hydroelectric structures is proposed. This system has been developed at the Hydro Quebec Research Institute and consists of a laser camera mounted on a 2-D Cartesian manipulator. Mechanical, electronic, and software design aspects; overall operational modalities; and proof of concept results are presented. We evaluated the performances of the system in the course of laboratory experiments and inspection trials carried out under normal operating conditions at the site of three of Hydro Quebec's hydroelectric dams.

  7. Nuclear-pumped lasers for large-scale applications

    SciTech Connect

    Anderson, R.E.; Leonard, E.M.; Shea, R.E.; Berggren, R.R.

    1988-01-01

    Efficient initiation of large-volume chemical lasers may be achieved by neutron induced reactions which produce charged particles in the final state. When a burst mode nuclear reactor is used as the neutron source, both a sufficiently intense neutron flux and a sufficient short initiation pulse may be possible. Proof-of-principle experiments are planned to demonstrate lasing in a direct nuclear-pumped large-volume system: to study the effects of various neutron absorbing materials on laser performance; to study the effects of long initiation pulse lengths; to determine the performance of large-scale optics and the beam quality that may bo obtained; and to assess the performance of alternative designs of burst systems that increase the neutron output and burst repetition rate. 21 refs., 7 figs., 5 tabs.

  8. A non-contact technique providing improved accuracy in area measurements of radiometric apertures

    Microsoft Academic Search

    J. Hartmann; J. Fischer; J. Seidel

    2000-01-01

    Beam-limiting apertures with accurately known areas are required when measuring the radiance and irradiance of sources. We have already described a non-contact method for measuring aperture areas using a laser beam focused on the aperture surface. By shifting the aperture relative to the laser beam, and collecting and monitoring the reflected light, the onset of reflection was used to indicate

  9. Single-pulse driven plasma Pockels cell with 350mm×350mm aperture

    NASA Astrophysics Data System (ADS)

    Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Lin, Donghui; Zheng, Kuixing; Jing, Feng

    2010-08-01

    Large-aperture plasma Pockels cell is one of important components for inertial confinement fusion laser facility. We demonstrate a single-pulse driven PPC with 350mm×350mm aperture. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPC meets the optical switching requirement of SGII update laser facility. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, less the maintenance, and higher reliability.

  10. Laser Pointer System Intuitive Interaction for Large High-Res Displays

    E-print Network

    Reiterer, Harald

    Laser Pointer System Intuitive Interaction for Large High-Res Displays LEDs Accelerometer Vibration Buttons Laser & LEDs Unlike conventional input devices like mouse and keyboard, laser pointers do that are displayed on large high-resolution screens. The laser pointer technology was developed in cooperation

  11. Quantitative comparison of terahertz emission from (100) InAs surfaces and a GaAs large-aperture

    E-print Network

    Reid, Matthew

    - fast laser sources to excite photoconductive switches,1 to excite transient currents on semicon- ductor emitters of THz radiation, especially under the influence of a magnetic field.5­7 These studies were a 1-mm-thick (110) ZnTe electro-optic crystal, with the THz field. This induces a polarization

  12. Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles

    Microsoft Academic Search

    G. Charmaine Gilbreath; William S. Rabinovich; Timothy J. Meehan; Michael J. Vilcheck; Rita Mahon; Ray Burris; Mina Ferraro; Ilene Sokolsky; John A. Vasquez; Chris S. Bovais; Kerry Cochrell; Kim C. Goins; Robin Barbehenn; D. Scott Katzer; Kiki Ikossi-Anastasiou; Marcos J. Montes

    2001-01-01

    We describe progress in the development of a multiple quantum well modulating retroreflector, including a description of recent demonstrations of an infrared data link between a small rotary-wing unmanned airborne vehicle and a ground-based laser interrogator using the device designed and fabricated at the Naval Research Laboratory (NRL). Modulating retroreflector systems couple an optical retroreflector, such as a corner cube,

  13. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: A wide-aperture Pockels cell with three ring electrodes

    NASA Astrophysics Data System (ADS)

    Andreev, N. F.; Bespalov, V. I.; Bredikhin, V. I.; Garanin, Sergey G.; Davydov, V. S.; Dolgopolov, Yu V.; Katin, E. V.; Kuznetsov, S. P.; Kulikov, S. M.; Matveev, A. Z.; Rubakha, V. I.; Sukharev, Stanislav A.

    2004-04-01

    A wide-aperture Pockels cell based on a DKDP crystal having an optical diameter of 70 mm is studied. Three silver ring electrodes deposited on the side surface of the crystal were used to apply a high-voltage rectangular pulse of variable duration from 50 to 150 ns to the cell. Chains of KT6117A (2N5551) transistors operating in the avalanche regime served as fast electron switches. The duration of the leading and trailing edges of the pulse formed by these switches did not exceed 15 ns. The nonuniformity of the transmission coefficient over the cross section of the cell caused by the inhomogeneity of the electric field inside the crystal was close to 3.5%.

  14. Large Field of View, Modular, Stabilized, Adaptive-Optics-Based Scanning Laser Ophthalmoscope

    PubMed Central

    Burns, Stephen A.; Tumbar, Remy; Elsner, Ann E.; Ferguson, Daniel; Hammer, Daniel X.

    2007-01-01

    We describe the design and performance of an adaptive optics retinal imager that is optimized for use during dynamic correction for eye movements. The system incorporates a retinal tracker and stabilizer, a wide field line scan Scanning Laser Ophthalmocsope (SLO), and a high resolution MEMS based adaptive optics SLO. The detection system incorporates selection and positioning of confocal apertures, allowing measurement of images arising from different portions of the double pass retinal point spread function (psf). System performance was excellent. The adaptive optics increased the brightness and contrast for small confocal apertures by more than 2x, and decreased the brightness of images obtained with displaced apertures, confirming the ability of the adaptive optics system to improve the pointspread function. The retinal image was stabilized to within 18 microns 90% of the time. Stabilization was sufficient for cross-correlation techniques to automatically align the images. PMID:17429477

  15. Really Large Scale Computer Graphic Projection Using Lasers and Laser Substitutes

    NASA Astrophysics Data System (ADS)

    Rother, Paul

    1989-07-01

    This paper reflects on past laser projects to display vector scanned computer graphic images onto very large and irregular surfaces. Since the availability of microprocessors and high powered visible lasers, very large scale computer graphics projection have become a reality. Due to the independence from a focusing lens, lasers easily project onto distant and irregular surfaces and have been used for amusement parks, theatrical performances, concert performances, industrial trade shows and dance clubs. Lasers have been used to project onto mountains, buildings, 360° globes, clouds of smoke and water. These methods have proven successful in installations at: Epcot Theme Park in Florida; Stone Mountain Park in Georgia; 1984 Olympics in Los Angeles; hundreds of Corporate trade shows and thousands of musical performances. Using new ColorRayTM technology, the use of costly and fragile lasers is no longer necessary. Utilizing fiber optic technology, the functionality of lasers can be duplicated for new and exciting projection possibilities. The use of ColorRayTM technology has enjoyed worldwide recognition in conjunction with Pink Floyd and George Michaels' world wide tours.

  16. Combining Measurements with Three-Dimensional Laser Scanning System and Coded Aperture Gamma-Ray Imaging System for International Safeguards Applications

    SciTech Connect

    Boehnen, Chris Bensing [ORNL] [ORNL; Bogard, James S [ORNL] [ORNL; Hayward, Jason P [ORNL] [ORNL; Raffo-Caiado, Ana Claudia [ORNL] [ORNL; Smith, Steven E [ORNL] [ORNL; Ziock, Klaus-Peter [ORNL] [ORNL

    2010-01-01

    Being able to verify the operator's declaration in regard to the technical design of nuclear facilities is an important aspect of every safeguards approach. In addition to visual observation, it is necessary to know if nuclear material is present or has been present in undeclared piping and ducts. The possibility of combining the results from different measurement techniques into one easily interpreted product should optimize the inspection effort and increase safeguards effectiveness. A collaborative effort to investigate the possibility of combining measurements from a three-dimensional (3D) laser scanning system and gamma-ray imaging systems is under way. The feasibility of the concept has been previously proven with different laboratory prototypes of gamma-ray imaging systems. Recently, simultaneous measurements were conducted with a new highly portable, mechanically cooled, High Purity Germanium (HPGe), coded-aperture gamma-ray imager and a 3D laser scanner in an operational facility with complex configuration and different enrichment levels and quantities of uranium. With specially designed software, data from both instruments were combined and a 3D model of the facility was generated that also identified locations of radioactive sources. This paper provides an overview of the technology, describes the measurements, discusses the various safeguards scenarios addressed, and presents results of experiments.

  17. Picosecond laser fabrication of micro cutting tool geometries on polycrystalline diamond composites using a high-numerical aperture micro scanning system

    NASA Astrophysics Data System (ADS)

    Eberle, Gregory; Dold, Claus; Wegener, Konrad

    2015-03-01

    The generation of microsized components found in LEDs, watches, molds as well as other types of micromechanics and microelectronics require a corresponding micro cutting tool in order to be manufactured, typically by milling or turning. Micro cutting tools are made of cemented tungsten carbide and are conventionally fabricated either by electrical discharge machining (EDM) or by grinding. An alternative method is proposed through a laser-based solution operating in the picosecond pulse duration whereby the beam is deflected using a modified galvanometer-driven micro scanning system exhibiting a high numerical aperture. A micro cutting tool material which cannot be easily processed using conventional methods is investigated, which is a fine grain polycrystalline diamond composite (PCD). The generation of various micro cutting tool relevant geometries, such as chip breakers and cutting edges, are demonstrated. The generated geometries are subsequently evaluated using scanning electron microscopy (SEM) and quality is measured in terms of surface roughness and cutting edge sharpness. Additionally, two processing strategies in which the laser beam processes tangentially and orthogonally are compared in terms of quality.

  18. Experimental study of laser beam transmission and power accounting in a large scale length laser plasma

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; MacGowan, B. J.; Berger, R. L.; Estabrook, K. G.; Glenzer, S. H.; Kirkwood, R. K.; Kruer, W. L.; Stone, G. E.; Montgomery, D. S.

    2000-08-01

    It is shown that the measured laser power transmission through a large scale length, high temperature plasma (which emulates an indirect drive ignition-scale plasma) is in approximate agreement with the simulated transmission provided the simulations account for the power loss due to scattering from laser-plasma instabilities. Detailed accounting of the incident, transmitted, scattered, and absorbed powers is used to infer the likely location in the target where most of the scattering occurs along the incident beam trajectory. This location is near the incident laser side of the target at peak electron temperatures for a range of laser intensities. As a result, the backscattered light measurements at peak electron temperature do not require significant adjustment to account for attenuation of the backscattered light as it propagates out through the plasma.

  19. Laser-plasma interactions in large gas-filled hohlraums

    SciTech Connect

    Turner, R.E.; Powers, L.V.; Berger, R.L. [and others

    1996-06-01

    Indirect-drive targets planned for the National Ignition Facility (NIF) laser consist of spherical fuel capsules enclosed in cylindrical Au hohlraums. Laser beams, arranged in cylindrical rings, heat the inside of the Au wall to produce x rays that in turn heat and implode the capsule to produce fusion conditions in the fuel. Detailed calculations show that adequate implosion symmetry can be maintained by filling the hohlraum interior with low-density, low-Z gases. The plasma produced from the heated gas provides sufficient pressure to keep the radiating Au surface from expanding excessively. As the laser heats this gas, the gas becomes a relatively uniform plasma with small gradients in velocity and density. Such long-scale-length plasmas can be ideal mediums for stimulated Brillouin Scattering (SBS). SBS can reflect a large fraction of the incident laser light before it is absorbed by the hohlraum; therefore, it is undesirable in an inertial confinement fusion target. To examine the importance of SBS in NIF targets, the authors used Nova to measure SBS from hohlraums with plasma conditions similar to those predicted for high-gain NIF targets. The plasmas differ from the more familiar exploding foil or solid targets as follows: they are hot (3 keV); they have high electron densities (n{sub e}=10{sup 21}cm{sup {minus}3}); and they are nearly stationary, confined within an Au cylinder, and uniform over large distances (>2 mm). These hohlraums have <3% peak SBS backscatter for an interaction beam with intensities of 1-4 x 10{sup 15} W/cm{sup 2}, a laser wavelength of 0.351{micro}m, f/4 or f/8 focusing optics, and a variety of beam smoothing implementations. Based on these conditions the authors conclude that SBS does not appear to be a problem for NIF targets.

  20. High peak power amplification in large-core all-solid Yb fibers with an index-elevated pump clad and a low numerical aperture core

    NASA Astrophysics Data System (ADS)

    Leich, M.; He, W.; Grimm, S.; Kobelke, J.; Zhu, Y.; Müller, B.; Bierlich, J.; Bartelt, H.; Jäger, M.

    2015-03-01

    We report on the development of large-core Yb-doped fibers with up to 100 ?m core diameter and present first experimental results for high peak power amplification. The material for core and pump cladding was fabricated by Powder Sinter Technology. Using a high Al concentration we achieved a numerical aperture (NA) of 0.21 of the pump cladding and a core NA below 0.1. The rod-type fiber exhibits high pump absorption. Using a 0.55 m short fiber sample as the main amplifier in a 3-stage ns pulsed fiber Master Oscillator Power Amplifier system we achieved 3 ns output pulses with 360 kW peak power and 2 mJ pulse energy. We observed suppressed Stimulated Raman Scattering with respect to the signal pulses, which offers the possibility of further power scaling of such fiber amplifier systems.

  1. Development and Testing of a Power Trough System Using a Structurally-Efficient, High-Performance, Large-Aperture Concentrator with Thin Glass Reflector and Focal Point Rotation

    SciTech Connect

    May, E. K.; Forristall, R.

    2005-11-01

    Industrial Solar Technology has assembled a team of experts to develop a large-aperture parabolic trough for the electric power market that moves beyond cost and operating limitations of 1980's designs based on sagged glass reflectors. IST's structurally efficient space frame design will require nearly 50% less material per square meter than a Solel LS-2 concentrator and the new trough will rotate around the focal point. This feature eliminates flexhoses that increase pump power, installation and maintenance costs. IST aims to deliver a concentrator module costing less than $100 per square meter that can produce temperatures up to 400 C. The IST concentrator is ideally suited for application of front surface film reflectors and ensures that US corporations will manufacture major components, except for the high temperature receivers.

  2. Early laser operations at the Large Binocular Telescope Observatory

    NASA Astrophysics Data System (ADS)

    Rahmer, Gustavo; Lefebvre, Michael; Christou, Julian; Raab, Walfried; Rabien, Sebastian; Ziegleder, Julian; Borelli, José L.; Gässler, Wolfgang

    2014-08-01

    ARGOS is the GLAO (Ground-Layer Adaptive Optics) Rayleigh-based LGS (Laser Guide Star) facility for the Large Binocular Telescope Observatory (LBTO). It is dedicated for observations with LUCI1 and LUCI2, LBTO's pair of NIR imagers and multi-object spectrographs. The system projects three laser beams from the back of each of the two secondary mirror units, which create two constellations circumscribed on circles of 2 arcmin radius with 120 degree spacing. Each of the six Nd:YAG lasers provides a beam of green (532nm) pulses at a rate of 10kHz with a power of 14W to 18W. We achieved first on-sky propagation on the night of November 5, 2013, and commissioning of the full system will take place during 2014. We present the initial results of laser operations at the observatory, including safety procedures and the required coordination with external agencies (FAA, Space Command, and Military Airspace Manager). We also describe our operational procedures and report on our experiences with aircraft spotters. Future plans for safer and more efficient aircraft monitoring and detection are discussed.

  3. Yb-doped large-mode-area laser fiber fabricated by halide-gas-phase-doping technique

    NASA Astrophysics Data System (ADS)

    Peng, Kun; Wang, Yuying; Ni, Li; Wang, Zhen; Gao, Cong; Zhan, Huan; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

    2015-06-01

    In this manuscript, we designed a rare-earth-halide gas-phase-doping setup to fabricate a large-mode-area fiber for high power laser applications. YbCl3 and AlCl3 halides are evaporated, carried respectively and finally mixed with usual host gas material SiCl4 at the hot zone of MCVD system. Owing to the all-gas-phasing reaction process and environment, the home-made Yb-doped fiber preform has a homogeneous large core and modulated refractive index profile to keep high beam quality. The drawn fiber core has a small numerical aperture of 0.07 and high Yb concentration of 9500?ppm. By using a master oscillator power amplifier system, nearly kW-level (951?W) laser output power was obtained with a slope efficiency of 83.3% at 1063.8?nm, indicating the competition and potential of the halide-gas-phase-doping technique for high power laser fiber fabrication.

  4. Effect of the photon lifetime on the characteristics of 850-nm vertical-cavity surface-emitting lasers with fully doped distributed Bragg reflectors and an oxide current aperture

    SciTech Connect

    Bobrov, M. A.; Blokhin, S. A., E-mail: blokh@mail.ioffe.ru; Kuzmenkov, A. G.; Maleev, N. A. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Blokhin, A. A. [Saint Petersburg State Polytechnical University (Russian Federation); Zadiranov, Yu. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Nikitina, E. V. [Russian Academy of Sciences, Saint Petersburg Academic University—Nanotechnology Research and Education Center (Russian Federation); Ustinov, V. M. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2014-12-15

    The effect of the photon lifetime in an optical microcavity on the characteristics of 850-nm vertical-cavity surface-emitting lasers (VCSELs) with fully doped distributed Bragg reflectors (DBRs) and an oxide current aperture is studied. The photon lifetime in the microcavity is controlled by varying the upper DBR reflectance. It is found that the speed of VCSELs with a current-aperture diameter of 10 ?m is mainly limited by the self-heating effect, despite an increase in the relaxation-oscillation damping coefficient with increasing photon lifetime in the microcavity. At the same time, the higher level of internal optical loss in lasers with a current-aperture diameter of 1.5 ?m leads to dominance of the effect of relaxation-oscillation damping independently of the radiation output loss. In the case of devices with a current-aperture diameter of 5.5 ?m, both mechanisms limiting the speed operate, which allow an increase in the VCSEL effective modulation frequency from 21 to 24 GHz as the photon lifetime decreases from 3.7 to 0.8 ps.

  5. Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles

    NASA Astrophysics Data System (ADS)

    Gilbreath, G. Charmaine; Rabinovich, William S.; Meehan, Timothy J.; Vilcheck, Michael J.; Mahon, Rita; Burris, Ray; Ferraro, Mina; Sokolsky, Ilene; Vasquez, John A.; Bovais, Chris S.; Cochrell, Kerry; Goins, Kim C.; Barbehenn, Robin; Katzer, D. Scott; Ikossi-Anastasiou, Kiki; Montes, Marcos J.

    2001-07-01

    We describe progress in the development of a multiple quantum well modulating retroreflector, including a description of recent demonstrations of an infrared data link between a small rotary-wing unmanned airborne vehicle and a ground-based laser interrogator using the device designed and fabricated at the Naval Research Laboratory (NRL). Modulating retroreflector systems couple an optical retroreflector, such as a corner cube, and an electro-optic shutter to allow two-way optical communications using a laser, telescope, and pointer-tracker on only one platform. The NRL modulating retroreflector uses a semiconductor-based multiple quantum well shutter capable of modulation rates greater than 10 Mbps, depending on link characteristics. The technology enables the use of near-infrared frequencies, which is well known to provide covert communications immune to frequency allocation problems. This specific device has the added advantage of being compact, lightweight, covert, and requires very low paper. Up to an order of magnitude in onboard power can be saved using a small array of these devices instead of the radio frequency equivalent. In the described demonstration, a Mbps optical link to an unmanned aerial vehicle in flight at a range of 100 to 200 feet is shown. Near real-time compressed video was also demonstrated at the Mbps level and is described.

  6. Large-field-of-view, modular, stabilized, adaptive-optics-based scanning laser ophthalmoscope

    Microsoft Academic Search

    Stephen A. Burns; Remy Tumbar; Ann E. Elsner; Daniel Ferguson; Daniel X. Hammer

    2007-01-01

    We describe the design and performance of an adaptive optics retinal imager that is optimized for use during dynamic correction for eye movements. The system incorporates a retinal tracker and stabilizer, a wide-field line scan scanning laser ophthalmoscope (SLO), and a high-resolution microelectromechanical-systems-based adaptive optics SLO. The detection system incorporates selection and positioning of confocal apertures, allowing measurement of images

  7. Plasma-ion-assisted coatings for 15 femtosecond laser systems.

    PubMed

    Oliver, J B; Bromage, J; Smith, C; Sadowski, D; Dorrer, C; Rigatti, A L

    2014-02-01

    Large-aperture deposition of high-laser-damage-threshold, low-dispersion optical coatings for 15 femtosecond pulses have been developed using plasma-ion-assisted electron-beam evaporation. Coatings are demonstrated over 10 in. aperture substrates. PMID:24514219

  8. Laser beacon adaptive optics ophthalmoscope for retinal multilayer imaging

    Microsoft Academic Search

    Liu Ruixue; Li Dayu; Xia Mingliang; Kong Ningning; Qi Yue; Zheng Xianliang; Xuan Li

    2011-01-01

    A flood-illuminated adaptive optics ophthalmoscope for retinal multilayer imaging is introduced in this paper. By arranging an alterable stop in the illumination path, the illuminated area of retinal layer can be changed. A laser beacon for wavefront sensing is formed when the stop is a narrow aperture. The large aperture allows flood illumination and expands imaging field. A moveable imaging

  9. Design of a neutron penumbral-aperture microscope with 10-. mu. m resolution

    SciTech Connect

    Ress, D.; Lerche, R.A.; Ellis, R.J.; Lane, S.M.

    1990-05-01

    We are currently designing a 10-{mu}m resolution neutron penumbral-aperture microscope to diagnose high-convergence targets at the Nova laser facility. To achieve such high resolution, the new microscope will require substantial improvements in three areas. First, we have designed thick penumbral apertures with extremely sharp cutoffs over a useful ({approx}100 {mu}m) field of view; fabrication of such apertures appears feasible using gold electroplating techniques. Second, the limited field of view and required close proximity of the aperture to the target (2 cm) necessitates a durable mounting and alignment system with {plus}25 {mu}m accuracy. Finally, a neutron detector containing 160,000 scintillator elements is required; readout and optimization of this large array are outstanding issues. 5 refs., 3 figs.

  10. Lasers for coherent optical satellite links with large dynamics

    E-print Network

    Chiodo, Nicola; Acef, Ouali; Clairon, Andre; Wolf, Peter

    2013-01-01

    We present the experimental realization of a laser system for ground to satellite optical Doppler ranging at the atmospheric turbulence limit. Such a system needs to display good frequency stability (a few parts in 10^{-14}) whilst allowing large and well controlled frequency sweeps of +/- 12 GHz at rates exceeding 100 MHz/s. Furthermore it needs to be sufficiently compact and robust for transportation to different astronomical observation sites where it is to be interfaced with satellite ranging telescopes. We demonstrate that our system fulfills those requirements and should therefore allow operation of ground to low Earth orbit satellite coherent optical links limited only by atmospheric turbulence.

  11. Synthetic aperture microwave radiometer

    NASA Technical Reports Server (NTRS)

    Levine, D. M.

    1988-01-01

    Realizing the full potential of microwave remote sensing from space requires putting relatively large antennas in orbit. Research is being conducted to develop synthetic aperture antennas to reduce the physical collecting area required of sensors in space, and to possibly open the door to new applications of microwave remote sensing. The technique under investigation involves using a correlation interferometer with multiple baselines. The Microwave Sensors and Data Collection Branch has been engaged in research to develop this technique for applications to remote sensing of soil moisture from space. Soil moisture is important for agricultural applications and for understanding the global hydrologic cycle. An aircraft prototype of an instrument suitable for making such measurements was developed. This is an L-band radiometer called ESTAR which is hoped will become part of the Earth Observing System (EOS). ESTAR is a hybrid instrument which uses both real aperture antennas (long sticks to obtain resolution in the along-track dimension) and aperture synthesis (correlation between sticks to obtain resolution in the cross track dimension). The hybrid was chosen as a compromise to increase the sensitivity (T) of the instrument.

  12. Multi-Aperture 3D Imaging Systems

    Microsoft Academic Search

    Joseph C. Marron; R. L. Kendrick

    2008-01-01

    With a multi-aperture imaging system, one creates a large imaging aperture by combining the light from a series of distributed telescopes. In doing this, one can construct a fine-resolution imaging system with reduced volume. We present work on multi-aperture, active imaging systems that use coherent detection and digital image formation. In such a system, the image formation process incorporates digital

  13. Restoring aperture profile at sample plane

    Microsoft Academic Search

    John L. Jackson; Richard P. Hackel; Arnold W. Lungershausen

    2003-01-01

    Off-line conditioning of full-size optics for the National Ignition Facility required a beam delivery system to allow conditioning lasers to rapidly raster scan samples while achieving several technical goals. The main purpose of the optical system designed was to reconstruct at the sample plane the flat beam profile found at the laser aperture with significant reductions in beam wander to

  14. Study of the generation characteristics of laser converters with dye-based wide-aperture solid--liquid active elements

    SciTech Connect

    Eremenko, A.S.; Zemskii, V.I.; Kolesnikov, Y.L.; Malinin, B.G.; Meshkovsky, I.K.; Savkin, N.P.; Stepanov, V.E.; Shildyaev, V.S.

    1986-11-01

    The lasing characteristics of an active element, consisting of a fine porous silicate matrix, has been studied. Molecules of a dye (rhodamine 6G) and an ethanol solution of the same dye were introduced into the cells. It has been shown that under conditions of large heat release (when thermooptical distortions begin to appear in the dye solutions), the solid--liquid element preserves the stability of its own lasing characteristics.

  15. Potential dynamic range in a scheme of the acousto-optical spectrometer providing light beam apodization for a large-aperture crystalline cell with linear acoustic losses

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Alexandre S.; Luna Castellanos, Abraham; Tepichin Rodriguez, Eduardo; Balderas Mata, Sandra E.

    2008-02-01

    We develop our previous considerations for one of the most important problems related to optimizing the performance data of a new acousto-optical spectrometer for the analysis of radio-astronomical signals. The main attention is paid to estimating the side lobes of light distributions inherent in an individual resolvable spot in the output Fourier plane, governing the dynamic range of that spectrometer. At first, we analyze the Akhieser mechanism responsible for linear attenuation of both longitudinal and shear elastic waves in isotropic solid states. Similar analysis can be directly applied to crystalline materials as well in all the cases of passing elastic wave along the acoustic axis in crystals. Then, we estimate the influence of the acoustic attenuation along a large-aperture acousto-optical cells operating in a one- and two-phonon light scattering regimes. In so doing, the optimal operating points are discussed for both these regimes. Finally, the combined effect of the acoustic attenuation and the incident light beam apodization is studied from the points of view of optimizing the levels of side lobes and minima in light distribution of an individual resolvable spot in focal plane of the integrating lens and, consequently, estimating potential limitations of the dynamic range.

  16. Long-Term Evaluation of the Scintec Boundary-Layer Scintillometer and the Wageningen Large-Aperture Scintillometer: Implications for Scintillometer Users

    NASA Astrophysics Data System (ADS)

    Van Kesteren, B.; Beyrich, F.; Hartogensis, O. K.; Braam, M.

    2015-04-01

    We compare the structure parameter of the refractive index, C_{nn} , measured simultaneously with two large-aperture scintillometers: the WagLAS (Wageningen University, Wageningen, the Netherlands) and the BLS900 (Scintec, Rottenburg, Germany). A 3.5-year dataset shows a bias in C_{nn} of about 17 % between the instruments. Analysis of these data reveals firstly that the logarithmic amplifiers in the WagLAS exhibit a strong dependence on temperature, resulting in an overestimation of C_{nn} of up to 35 % for temperatures < 0° C. Secondly, high-pass filtering of the WagLAS and BLS900 intensity data artificially reduces C_{nn} for crosswinds < 2 {m s}^{-1} (error ? 25 and ? 5 % respectively). Thirdly, the BLS900 increasingly underestimates C_{nn} (up to 10-15 %) with increasing signal saturation. We demonstrate that Scintec's data processing relies too heavily on the assumption that the intensity data obey a log-normal distribution, which they do not in the case of saturation. Fourthly, both instruments ignore the dissipation range of the refractive-index spectrum, which leads to an overestimation of C_{nn} of up to 30 % for friction velocity < 0.2 {m s}^{-1} . Implications of these findings are discussed and placed into perspective for other scintillometer users. Furthermore, we present a tool for revealing saturation and other violations of Rytov theory for any given scintillometer type, including microwave scintillometers.

  17. Laser deposition of large-area thin films

    SciTech Connect

    Kuzanyan, A S; Petrosyan, V A; Pilosyan, S Kh; Nesterov, V M

    2011-03-31

    A new method for fabricating large-area thin films of uniform thickness on a rotating substrate is proposed. Its distinctive features are (i) the presence of a diaphragm, partially transmitting the evaporated material, between the target and substrate and (ii) the translatory motion of the rotating substrate with respect to the target at a certain velocity. The method proposed makes it possible to obtain thin films of uniform thickness on substrates with sizes limited by only the deposition chamber size. The method is experimentally verified by depositing thin CuO films on silicon substrates placed over the radius of a disk 300 mm in diameter. The deviation of the film thickness from the average value does not exceed {+-}3% throughout the entire radius, which confirms good prospects of this method for microelectronics, optical industry, and other modern technologies. (laser technology)

  18. Large Deformation Change in Iridium Isotopes from Laser Spectroscopy

    SciTech Connect

    D. Verney; L. Cabaret; J. Crawford; H.T. Duong; J. Genevey; G. Hubert; F. Ibrahim; M. Krieg; F. Le Blanc; J.K.P. Lee; G. Le Scornet; D. Lunney; J. Obert; J. Oms; J. Pinard; J.C. Putaux; B. Roussiere; J. Sauvage; V. Sebastian

    1999-12-31

    Laser spectroscopy measurements have been performed on neutron-deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2} {yields}5d{sup 7}6s6p {sup 6}F{sub 11/2} have been studied for the {sup 182-189}Ir, {sup 186}Ir{sup m} and {sup 191,193}Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the hyperfine splitting measurements and the changes of the mean square charge radii from the isotope shift measurements. A large deformation change between {sup 187}Ir and {sup 186}Ir and between {sup 186}Ir{sup m} and {sup 186}Ir{sup g} has been observed.

  19. Large deformation change in iridium isotopes from laser spectroscopy

    SciTech Connect

    Verney, D.; Le Blanc, F.; Obert, J.; Oms, J.; Putaux, J. C.; Roussiere, B.; Sauvage, J. [Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay Cedex (France); Cabaret, L.; Duong, H. T.; Pinard, J. [Laboratoire Aime Cotton, 91405 Orsay Cedex (France); Crawford, J.; Lee, J. K. P. [Physics Department, Mc Gill University, H3A2T8 Montreal (Canada); Genevey, J.; Ibrahim, F. [Institut des Sciences Nucleaires, IN2P3-CNRS, 38026 Grenoble Cedex (France); Hubert, G.; Krieg, M.; Sebastian, V. [Institut fuer Physik der Univeristaet Mainz (Germany); Le Scornet, G.; Lunney, D. [CSNSM, IN2P3-CNRS, 91405 Orsay Cedex (France)

    1999-11-16

    Laser spectroscopy measurements have been performed on neutron-deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d{sup 7}6s{sup 2} {sup 4}F{sub 9/2}{yields}5d{sup 7}6s6p {sup 6}F{sub 11/2} have been studied for the {sup 182-189}Ir, {sup 180}Ir{sup m} and {sup 191,193}Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the hyperfine splitting measurements and the changes of the mean square charge radii from the isotope shift measurements. A large deformation change between {sup 187}Ir and {sup 186}Ir and between {sup 186}Ir{sup m} and {sup 186}Ir{sup g} has been observed.

  20. Lasers for coherent optical satellite links with large dynamics.

    PubMed

    Chiodo, Nicola; Djerroud, Khelifa; Acef, Ouali; Clairon, André; Wolf, Peter

    2013-10-20

    We present the experimental realization of a laser system for ground-to-satellite optical Doppler ranging at the atmospheric turbulence limit. Such a system needs to display good frequency stability (a few parts in 10-14) while allowing large and well-controlled frequency sweeps of ±12??GHz at rates exceeding 100??MHz/s. Furthermore it needs to be sufficiently compact and robust for transportation to different astronomical observation sites, where it is to be interfaced with satellite ranging telescopes. We demonstrate that our system fulfills those requirements and should therefore allow operation of ground to low Earth orbit satellite coherent optical links limited only by atmospheric turbulence. PMID:24216589

  1. Laser microprocessing and nanoengineering of large-area functional micro/nanostructures

    NASA Astrophysics Data System (ADS)

    Tang, M.; Xie, X. Z.; Yang, J.; Chen, Z. C.; Xu, L.; Choo, Y. S.; Hong, M. H.

    2011-12-01

    Laser microprocessing and nanoengineering are of great interest to both scientists and engineers, since the inspired properties of functional micro/nanostructures over large areas can lead to numerous unique applications. Currently laser processing systems combined with high speed automation ensure the focused laser beam to process various materials at a high throughput and a high accuracy over large working areas. UV lasers are widely used in both laser microprocessing and nanoengineering. However by improving the processing methods, green pulsed laser is capable of replacing UV lasers to make high aspect ratio micro-grooves on fragile and transparent sapphire substrates. Laser micro-texturing can also tune the wetting property of metal surfaces from hydrophilic to super-hydrophobic at a contact angle of 161° without chemical coating. Laser microlens array (MLA) can split a laser beam into multiple laser beams and reduce the laser spot size down to sub-microns. It can be applied to fabricate split ring resonator (SRR) meta-materials for THz sensing, surface plasmonic resonance (SPR) structures for NIR and molding tools for soft lithography. Furthermore, laser interference lithography combined with thermal annealing can obtain a large area of sub-50nm nano-dot clusters used for SPR applications.

  2. Processing and Application of ICESat Large Footprint Full Waveform Laser Range Data

    Microsoft Academic Search

    V. H. Duong

    2010-01-01

    In the last two decades, laser scanning systems made the transition from scientific research to the commercial market. Laser scanning has a large variety of applications such as digital elevation models, forest inventory and man-made object reconstruction, and became the most required input data for flood plain and hydraulic models. This system is generally called as a discrete laser scanning

  3. Solar Central Receiver with an Irising Aperture 

    E-print Network

    Galal, T.; Kulaib, A. M.; Abuzaid, M.

    2010-01-01

    . If the aperture is small, it will be inefficient for periods when the solar isolation is inclined due to spillage. However, if the aperture is large, it will be inefficient for periods when the solar isolation is normal, due to excess heat radiation and convection...

  4. Nearly flat-top laser beams from unstable resonators with internal spatial filtering

    Microsoft Academic Search

    Reza Massudi; Michel Piché

    1997-01-01

    We theoretically show that negative branch confocal unstable resonators with an aperture at the confocal plane can be used to generate nearly flat-top laser beams at large Fresnel numbers. Such a behavior is due to the fact that these resonators can be viewed as image relay systems that provide magnified versions of the internal aperture. Modal discrimination increases with magnification

  5. Performance of a simplified slit spatial filter for large laser systems.

    PubMed

    Xiong, Han; Yuan, Xiao; Zhang, Xiang; Zou, Kuaisheng

    2014-09-01

    A new-type slit spatial filter system with three lenses was proposed, in which the focal spot was turned into focal line by adding cylindrical lenses to increase focal area and then lower the focal intensity. Its performances on image relay, aperture matching and spatial filtering are comprehended by detailed theoretical calculations and numerical simulation. According to transmission spatial filter in national ignition facility, we present a replaceable slit spatial filter, which can reduce the overall length of laser system, improve the beam quality and suppress or even avoid the pinhole (slit) closure in the spatial filter. PMID:25321597

  6. Electron microscope aperture system

    NASA Technical Reports Server (NTRS)

    Heinemann, K. (inventor)

    1976-01-01

    An electron microscope including an electron source, a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen, and an objective lens having an annular objective aperture, for focusing electrons passing through the specimen onto an image plane are described. The invention also entails a method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques.

  7. Large angle and high linearity two-dimensional laser scanner based on voice coil actuators

    Microsoft Academic Search

    Xin Wu; Sihai Chen; Wei Chen; Minghui Yang; Wen Fu

    2011-01-01

    A large angle and high linearity two-dimensional laser scanner with an in-house ingenious deflection angle detecting system is developed based on voice coil actuators direct driving mechanism. The specially designed voice coil actuators make the steering mirror moving at a sufficiently large angle. Frequency sweep method based on virtual instruments is employed to achieve the natural frequency of the laser

  8. Aperture masking behind AO systems

    NASA Astrophysics Data System (ADS)

    Ireland, Michael J.

    2012-07-01

    Sparse Aperture-Mask Interferometry (SAM or NRM) behind Adaptive Optics (AO) has now come of age, with more than a dozen astronomy papers published from several 5-10m class telescopes around the world. I will describe the reasons behind its success in achieving relatively high contrasts ( 1000:1 at lambda/ D) and repeatable binary astronomy at the diffraction limit, even when used behind laser-guide star adaptive optics. Placed within the context of AO calibration, the information in an image can be split into pupil-plane phase, Fourier amplitude and closure-phase. It is the closure-phase observable, or its generalisation to Kernel phase, that is immune to pupil-plane phase errors at first and second-order and has been the reason for the technique's success. I will outline the limitations of the technique and the prospects for aperture-masking and related techniques in the future.

  9. Large hollow-core fiber random dye laser

    Microsoft Academic Search

    R. J. R. Vieira; C. J. S. de Matos; A. Cerqueira S; F. Couny; F. Benabid; L. Gomes; N. U. Wetter

    2009-01-01

    Random lasers (RL) have several interesting features that cannot be achieved with common bulk or fiber lasers such as simultaneous emission of several different wavelengths at the same time and emission at new extremely low gain lines. They also permit miniaturization and very low cost. To make the random emission useful, some sort of guiding mechanism that collects the stimulated

  10. Comparability of spectral radiance calibrations of large aperture earth observing instruments based upon diffuse reflective panels and internally illuminated spherical integrator techniques

    Microsoft Academic Search

    Donald F. Heath; Zongying Wei; William K. Fowler; V. W. Nelson; Ernest Hilsenrath

    1994-01-01

    A comparison has been made of spectral radiance calibrations of SBUV-2 instruments using two techniques. In one, a source of spectral radiance is obtained by illuminating a spectralon panel diffuser whose BRDF has been measured by NIST with a 1000 W FEL quartz-tungsten- halogen standard of spectral irradiance from NIST. In the other, the spectral irradiance of the aperture of

  11. Measurement system for large size laser beam intensity distribution based on CCD diffuse transmission imaging

    NASA Astrophysics Data System (ADS)

    Pang, Miao; Rong, Jian; Yuan, Xuewen; Gao, Xueyan; Zhou, Shan

    2013-12-01

    We designed a measurement system to measure large size laser beam intensity distribution based on CCD diffuse transmission imaging. The measurement principle is presented. The configuration of the system is introduced. An emphasis is placed on the design of diffuse transmission target. The methods of spot geometry distortion correction and intensity distortion correction are described in detail. After laser spot correction, we can get the real laser beam intensity profile. The test results are given, which validate the correctness of the method. The paper provides a new way to measure quantitatively the profile of large size laser beam with high accuracy.

  12. An accurate and stable method of array element tiling for high-power laser facilities

    NASA Astrophysics Data System (ADS)

    Mu, Jie; Wang, Xiao; Jing, Feng; Li, Zhi-Lin; Cheng, Ning-Bo; Zhu, Qi-Hua; Su, Jing-Qin; Zhang, Jun-Wei; Zhou, Kai-Nan; Zeng, Xiao-Ming

    2015-07-01

    Due to laser-induced damage, the aperture of optics is one of the main factors limiting the output capability of high-power laser facilities. Because of the general difficulty in achieving large-aperture optics, an alternative solution is to tile some small-aperture ones together. We propose an accurate, stable, and automatic method of array element tiling and verify it on a double-pass 1 × 2 tiled-grating compressor in the XG-III laser facility. The test results show the accuracy and stability of the method. This research provides an efficient way to obtain large-aperture optics for high-power laser facilities. Project supported by the National Natural Science Foundation of China (Grant No. 61308040) and the National High Technology Research and Development Program of China (Grant No. 2013AA8043047).

  13. Compensation of the laser parameters fluctuations in large ring laser gyros: a Kalman filter approach

    E-print Network

    Beghi, Alessandro; Beverini, Nicolò; Bouhadef, B; Cuccato, D; Di Virgilio, Angela; Ortolan, Antonello

    2012-01-01

    He-Ne ring lasers gyroscopes are, at present, the most precise devices for absolute angular velocity measurements. Limitations to their performance come from the non--linear dynamics of the laser. According to the Lamb semi-classical theory of lasers, we individuate a set of critical parameters affecting the time stability of the system. We propose a method for estimating the long term drift of the laser parameters and for filtering out the laser dynamics effects from ring laser outputs. The parameter estimation procedure, based on the perturbative solutions of the laser dynamics, allow us to apply Kalman Filter theory for the estimation of the angular velocity. Results of a comprehensive Monte Carlo simulation, and results of a preliminary analysis on experimental data from the ring laser prototype G-Pisa are shown and discussed.

  14. Shearing interferometry for laser-guide-star atmospheric correction at large at large D\\/r0

    Microsoft Academic Search

    D. G. Sandler; L. Cuellar; M. Lefebvre; T. Barrett; R. Arnold; P. Johnson; A. Rego; G. Smith; G. Taylor; B. Spivey

    1994-01-01

    Shearing interferometry offers a possible method to scale wave-front sensors to the large number of subapertures that will be required for correction of the new generation of large 6-10-m-class telescopes at visible wavelengths. The authors discuss static shearing interferometers, which are prototype wave-front sensors for use with laser guide stars at large values of D\\/r0. The dc interferometers utilize low-noise

  15. Laser conditioning methods of hafnia silica multilayer mirrors

    Microsoft Academic Search

    Christopher J. Stolz; Lynn M. Sheehan; Stephen M. Maricle; Sheldon Schwartz; Mark R. Kozlowski; Richard T. Jennings; Jean Hue

    1998-01-01

    Large aperture multilayer hafnia silica high reflector coatings at 1064 nm, deposited by reactive electron-beam deposition, were prepared to examine different laser conditioning methods for manufacturing high fluence optics in the National Ignition Facility. Laser conditioning is a process where the damage threshold of the coating is increased or the damage that is created is minimized so that it does

  16. Large-area electron beam diode modeling for KrF Laser IFE

    Microsoft Academic Search

    D. V. Rose; D. R. Welch; J. D. Sethian; J. L. Guiliani; F. Hegeler; S. B. Swanekamp

    2003-01-01

    The KrF Laser Inertial Fusion Energy (IFE) scheme focuses ˜ 60 individually generated 58 kJ laser pulses symmetrically onto a high yield fusion target. The lasers are pumped by large-area electron beam diodes, the technology for which is presently being developed on the Electra^1 and Nike^2 facilities at the Naval Research Laboratory in Washington, DC. An IFE-level diode design is

  17. Active compensation of large dispersion of femtosecond pulses for precision laser ranging.

    PubMed

    Lee, Sang-Hyun; Lee, Joohyung; Kim, Young-Jin; Lee, Keunwoo; Kim, Seung-Woo

    2011-02-28

    We describe an active way of compensation for large dispersion induced in the femtosecond light pulses travelling in air for laser ranging. The pulse duration is consistently regulated at 250 fs by dispersion control, allowing sub-micrometer resolution in measuring long distances by means of time-of-flight measurement. This method could facilitate more reliable applications of femtosecond pulses for satellite laser ranging, laser altimetry and active LIDAR applications. PMID:21369227

  18. Continuous Earth Rotation Monitoring with the large Ring Laser G

    NASA Astrophysics Data System (ADS)

    Schreiber, Ulrich; Holdaway, John; Gebauer, André; Kluegel, Thomas; Wells, Jon-Paul

    2010-05-01

    Over the last decade, ring lasers have found their way back into the research laboratories. By scaling them up in size, they have gained several orders of magnitude over their commercial counterparts, both in sensitivity and stability. Unlike the established space geodetic techniques SLR/LLR and VLBI, ring lasers can be operated autonomous and continuously. While a single ring laser component already provides direct access to the instantaneous axis of rotation of the Earth, it is also susceptible to local perturbations both with respect to platform rotation and instrumental tilt caused by local wind load for example. These instrumental coupling issues are addressed in more detail in a separate paper (Gebauer et al.) in this conference. Currently the laser gyro G at the Geodetic Observatory Wettzell (Germany) can resolve rotation rates as small as 1 pico-rad/s requiring an integration time of less than 2 hours. This opens the door for the research of high frequency variations in Earth rotation. Over the last year we have improved the ring laser technology by as much as a factor of 3 in sensitivity, which makes the domain of ?Omega/Omega ? 10e-9 of Earth rotation accessible to a local rotation sensor. Currently it appears that the micro-seismic background activity of the Earth causes the major part from the observed deviation of the sensor performance with respect to the computed shot noise limit. Recent efforts concentrated on the improvement of the sensor stability against drift effects caused by the aging of the laser gas, scale factor instabilities induced by atmospheric pressure variations and the corresponding temperature changes from adiabatic expansion and compression of the local air around the instrument. Over the last year have introduced a pressure stabilizing vessel enclosing the entire ring laser structure. By monitoring the optical frequency in the ring laser cavity continuously and stabilizing the scale factor in a closed loop system, it became possible to extend the range of sensor stability from the short term (1-3 days) to at least well into the mid-term regime (>40 days) and possible even well beyond that. Once a sufficiently long time-series from ring laser data has become available, we will be able to define the range of temporal stability in more detail. The extension of the regime of stability gives access to geophysical signals at frequencies substantially lower than previously observable with ring lasers. This talk outlines this recent progress in Sagnac interferometry and presents the new data.

  19. Effects of large-area irradiated laser phototherapy on peripheral nerve regeneration across a large gap in a biomaterial conduit.

    PubMed

    Shen, Chiung-Chyi; Yang, Yi-Chin; Liu, Bai-Shuan

    2013-01-01

    This paper proposes a novel biodegradable nerve conduit comprising 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) cross-linked gelatin, annexed with ?-tricalcium phosphate (TCP) ceramic particles (EDC-Gelatin-TCP, EGT). In this study, the EGT-implant site in rats was irradiated using a large-area 660 nm AlGaInP diode laser (50 mW) to investigate the feasibility of laser stimulation in the regeneration of a 15-mm transected sciatic nerve. The animals were divided into three groups: a sham-irradiated group (EGT/sham); an experimental group undergoing low-level laser (LLL) therapy (EGT/laser); a control group undergoing autologous nerve grafts (autografts). Twelve weeks after implantation, walking track analysis showed a significantly higher sciatic functional index (p < 0.05) and improved toe spreading development in the EGT/laser and autograft groups than in the EGT/sham group. In electrophysiological measurement, both the mean peak amplitude and the area under the compound muscle action potential curves in the EGT/laser and autograft groups showed significantly improved functional recovery than the EGT/sham group (p < 0.05). Compared with the EGT/sham group, the EGT/laser and autograft groups displayed a reduction in muscular atrophy. Histomorphometric assessments revealed that the EGT/laser group had undergone more rapid nerve regeneration than the EGT/sham group. The laser-treated group also presented greater neural tissue area as well as larger axon diameter and thicker myelin sheath than the tube group without the laser treatment, indicating improved nerve regeneration. Thus, these assessments demonstrate that LLL therapy can accelerate the repair of a transected peripheral nerve in rats after being bridged with EGT conduit. PMID:22887896

  20. Micro-scanning mirrors for high-power laser applications in laser surgery

    NASA Astrophysics Data System (ADS)

    Sandner, Thilo; Kimme, Simon; Grasshoff, Thomas; Todt, Ulrich; Graf, Alexander; Tulea, Cristian; Lenenbach, Achim; Schenk, Harald

    2014-03-01

    We present two novel micro scanning mirrors with large aperture and HR dielectric coatings suitable for high power laser applications in a miniaturized laser-surgical instrument for neurosurgery to cut skull tissue. An electrostatic driven 2D-raster scanning mirror with 5x7.1mm aperture is used for dynamic steering of a ps-laser beam of the laser cutting process. A second magnetic 2D-beam steering mirror enables a static beam correction of a hand guided laser instrument. Optimizations of a magnetic gimbal micro mirror with 6 mm x 8 mm mirror plate are presented; here static deflections of 3° were reached. Both MEMS devices were successfully tested with a high power ps-laser at 532nm up to 20W average laser power.

  1. A Large-Area PVDF Pyroelectric Sensor for CO 2 Laser Beam Alignment

    Microsoft Academic Search

    Marina Mazzoni; Lorenzo Capineri; Leonardo Masotti

    2007-01-01

    We present the design of a large-area (50 mm times 50 mm) polyvynilidene fluoride (PVDF) pyroelectric sensor array for industrial CO2 (lambda = 10.6 mum) laser beam positioning. The array dimensions were chosen to match the area typically monitored in the alignment procedure of external optics (beam steering moving arm system, for example) used to redirect the laser beam from

  2. Application of laser velocimetry to unsteady flows in large scale high speed tunnels

    NASA Technical Reports Server (NTRS)

    Owen, F. K.

    1983-01-01

    Flowfield measurements obtained in several large scale, high speed facilities are presented. Sampling bias and seeding problems are addressed and solutions are outlined. The laser velocimeter systems and data reduction procedures which were used in the experiments are also described. The work demonstrated the potential of the laser velocimeter for applications in other than closely controlled, smallscale laboratory situations.

  3. Development and utilization of a laser velocimeter system for a large transonic wind tunnel

    Microsoft Academic Search

    R. J. Freedman; J. P. Greissing

    1982-01-01

    The need for measurements of the velocity flow field about spinner propeller nacelle configurations at Mach numbers to 0.8 was met by a specially developed laser velocimeter system. This system, which uses an argon ion laser and 4 beam 2 color optics, was required to operate in the hostile environment associated with the operation of a large transonic wind tunnel.

  4. Superresolving masks for incoherent high-numerical-aperture scanning

    E-print Network

    Bertero, Mario

    ) analysis, giving both the spectrum and the singular functions, of the imaging of the high-NA fluorescence kernel for three-dimensional fluorescent laser scan- ning microscopy at a high numerical aperture (NA

  5. Compensation of the laser parameter fluctuations in large ring-laser gyros: a Kalman filter approach

    NASA Astrophysics Data System (ADS)

    Beghi, Alessandro; Belfi, Jacopo; Beverini, Nicolò; Bouhadef, B.; Cuccato, D.; Di Virgilio, Angela; Ortolan, Antonello

    2012-11-01

    He-Ne ring laser gyroscopes are, at present, the most precise devices for absolute angular velocity measurements. Limitations to their performance come from the non--linear dynamics of the laser. Following the Lamb semi-classical theory, we find a set of critical parameters affecting the time stability of the system. We propose a method for estimating the long term drift of the laser parameters and for filtering out the laser dynamics effects from the rotation measurement. The parameter estimation procedure, based on the perturbative solutions of the laser dynamics, allow us to apply Kalman Filter theory for the estimation of the angular velocity. Results of a comprehensive Monte Carlo simulation and results of a preliminary analysis on experimental data from the ring laser prototype G-Pisa are shown and discussed.

  6. Rotating Aperture System

    SciTech Connect

    Rusnak, Brian; Hall, James M.; Shen, Stewart; Wood, Richard L.

    2005-01-18

    A rotating aperture system includes a low-pressure vacuum pumping stage with apertures for passage of a deuterium beam. A stator assembly includes holes for passage of the beam. The rotor assembly includes a shaft connected to a deuterium gas cell or a crossflow venturi that has a single aperture on each side that together align with holes every rotation. The rotating apertures are synchronized with the firing of the deuterium beam such that the beam fires through a clear aperture and passes into the Xe gas beam stop. Portions of the rotor are lapped into the stator to improve the sealing surfaces, to prevent rapid escape of the deuterium gas from the gas cell.

  7. Controlling synchronization in large laser networks using number theory

    E-print Network

    Micha Nixon; Moti Fridman; Eitan Ronen; Asher A. Friesem; Nir Davidson; Ido Kanter

    2011-12-18

    Synchronization in networks with delayed coupling are ubiquitous in nature and play a key role in almost all fields of science including physics, biology, ecology, climatology and sociology. In general, the published works on network synchronization are based on data analysis and simulations, with little experimental verification. Here we develop and experimentally demonstrate various multi-cluster phase synchronization scenarios within coupled laser networks. Synchronization is controlled by the network connectivity in accordance to number theory, whereby the number of synchronized clusters equals the greatest common divisor of network loops. This dependence enables remote switching mechanisms to control the optical phase coherence among distant lasers by local network connectivity adjustments. Our results serve as a benchmark for a broad range of coupled oscillators in science and technology, and offer feasible routes to achieve multi-user secure protocols in communication networks and parallel distribution of versatile complex combinatorial tasks in optical computers.

  8. Comparison of laser-induced surface damage density measurements with small and large beams: toward representativeness

    SciTech Connect

    Lamaignere, Laurent; Dupuy, Gabriel; Donval, Thierry; Grua, Pierre; Bercegol, Herve

    2011-02-01

    Pulsed laser damage density measurements obtained with diverse facilities are difficult to compare, due to the interplay of numerous parameters, such as beam area and pulse geometry, which, in operational large beam conditions, are very different from laboratory measurements. This discrepancy could have a significant impact; if so, one could not even pretend that laser damage density control is a real measurement process. In this paper, this concern is addressed. Tests with large beams of centimeter size on a high-power laser facility have beam performed according to a parametric study and are compared to small beam laboratory tests. It is shown that laser damage densities obtained with large and small beams are equal, within calculated error bars.

  9. Observation of the Earth's dynamic ellipticity with a large ring laser gyroscope

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Schreiber, Karl Ulrich; Kluegel, Thomas; Gebauer, Andre

    2015-04-01

    With the rapid advance of large ring laser gyroscopes, their promising applications in geoscience (such as, detection of Earth's tides, Earth's free oscillations and seismical waves etc.) have been demonstrated impressively by several ring laser groups. In this work we will report on one more application, which is the determination of the Earth's dynamical ellipticity by measuring the retrograde diurnal polar motion at the K1 wave with a single large ring laser. The Earth's astronomical dynamical ellipticity Hd = 0.00325(6) is estimated by means of 168 days of continuous data from the G-ring, located in Wettzell, Germany, which is the most stable one amongst the currently running large ring laser gyroscopes.

  10. Adaptive space\\/frequency processing for distributed aperture radars

    Microsoft Academic Search

    Raviraj Advea; Richard Schneibleb; Robert Mcmillan

    2003-01-01

    This paper deals a preliminary investigation into space-time-waveform adaptive processing for waveform diverse distributed apertures. The large baseline of such a distributed radar results in angular resolution that is orders of magnitude better than resolution of a monolithic system (single large radar) with the same power-aperture. This capability comes at the cost of grating lobes (multistatics with evenly spaced apertures)

  11. Large ring laser gyroscopes: towards absolute rotation rate sensing

    NASA Astrophysics Data System (ADS)

    Hurst, Robert B.; Rabeendran, Nishanthan; Wells, Jon-Paul R.; Schreiber, K. Ulrich

    2015-01-01

    Ring laser gyroscopes have increased in sensitivity by six orders of magnitude over the last several decades such that they are poised to make valuable contributions to geodesy and terrestrial tests of general relativity. To fully exploit their capabilities, residual (time varying) read out errors arising from backscatter coupling must be physically minimized or otherwise compensated. We present the results of a backscatter correction process for a 12.25 m2 gyroscope with a vast improvement in long term rotational sensitivity.

  12. Synthetic characteristics of large carbon cluster ions by laser ablation of polymers in vacuum

    NASA Astrophysics Data System (ADS)

    Shibagaki, K.; Takada, N.; Sasaki, K.; Kadota, K.

    2003-01-01

    The synthetic characteristics of large carbon cluster ions by laser ablation of polymers in vacuum were investigated. Time-of-flight mass spectrometry was used for analyzing the masses of ionic species produced by laser ablation. We found that large carbon cluster ions Cn+ with n up to 400 were synthesized in vacuum when copolymer of ethylene and tetrafluoroethylene, polyvinyliden fluoride, and chlorotrifluoroethylene were employed as the target material. Since the synthesis of large cluster ions in vacuum is a surprising phenomenon, we examined the synthesis efficiency in various experimental conditions. By comparing mass spectra obtained from various polymers containing hydrogen and/or halogen atoms, the existence of both hydrogen and halogen atoms in polymers do not directly contribute to enhance the synthesis efficiency of large carbon clusters. In addition, microscopic observations of surface morphologies of laser-ablated polymers revealed that the clustering reactions in eroded craters had little correlation with the synthesis efficiency of large carbon clusters.

  13. Continuous Earth Rotation Monitoring with the large Ring Laser G

    NASA Astrophysics Data System (ADS)

    Schreiber, K. U.; Klügel, T.; Wells, J. P.; Holdaway, J.; Gebauer, A.

    2010-12-01

    Over the last decade, ring lasers have found their way back into the research laboratories. By scaling them up in size, they have gained several orders of magnitude over their commercial counterparts, both in sensitivity and stability. Unlike the established space geodetic techniques SLR/LLR and VLBI, ring lasers can be operated autonomous and continuously. Furthermore laser gyros reach a resolution of 1 pico-rad/s already after an integration time of less than 2 hours. This opens the door for the research of high frequency variations in Earth rotation. Over the last year we have improved the sensor sensitivity by as much as a factor of 3 in order to reach the shot noise limit at 2.1x10-11 rad/s/sqrt(Hz). So the regime of ??/? ? 10-9 of Earth rotation becomes accessible to a local rotation sensor. Recent efforts concentrate on the reduction of scale factor instability by controlling the drift induced by atmospheric pressure variations and the corresponding temperature changes from adiabatic expansion and compression of the local air as well as a new approach to the modeling of the behavior of the sensor location. This talk outlines recent progress in Sagnac interferometry.

  14. Sub-Aperture Interferometers

    NASA Technical Reports Server (NTRS)

    Zhao, Feng

    2010-01-01

    Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

  15. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Y.W.; Wiedermann, A.H.; Ockert, C.E.

    1983-08-26

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  16. Shock wave absorber having apertured plate

    DOEpatents

    Shin, Yong W. (Western Springs, IL); Wiedermann, Arne H. (Chicago Heights, IL); Ockert, Carl E. (Vienna, VA)

    1985-01-01

    The shock or energy absorber disclosed herein utilizes an apertured plate maintained under the normal level of liquid flowing in a piping system and disposed between the normal liquid flow path and a cavity pressurized with a compressible gas. The degree of openness (or porosity) of the plate is between 0.01 and 0.60. The energy level of a shock wave travelling down the piping system thus is dissipated by some of the liquid being jetted through the apertured plate toward the cavity. The cavity is large compared to the quantity of liquid jetted through the apertured plate, so there is little change in its volume. The porosity of the apertured plate influences the percentage of energy absorbed.

  17. Bursts of Terahertz Radiation from Large-Scale Plasmas Irradiated by Relativistic Picosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Liao, G. Q.; Li, Y. T.; Li, C.; Su, L. N.; Zheng, Y.; Liu, M.; Wang, W. M.; Hu, Z. D.; Yan, W. C.; Dunn, J.; Nilsen, J.; Hunter, J.; Liu, Y.; Wang, X.; Chen, L. M.; Ma, J. L.; Lu, X.; Jin, Z.; Kodama, R.; Sheng, Z. M.; Zhang, J.

    2015-06-01

    Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime over 10 THz. The pulse energy of the radiation is found to be above 1 0 0 ? J per steradian in the laser specular direction at an optimal preplasma scale length around 40 - 50 ? m . Particle-in-cell simulations indicate that the radiation is mainly produced by linear mode conversion from electron plasma waves, which are excited successively via stimulated Raman scattering instability and self-modulated laser wakefields during the laser propagation in the preplasma. This radiation can be used not only as a powerful source for applications, but also as a unique diagnostic of parametric instabilities of laser propagation in plasmas.

  18. Parallel optical nanolithography using nanoscale bowtie apertures

    NASA Astrophysics Data System (ADS)

    Uppuluri, Sreemanth M. V.

    Over the past two decades various branches of science and engineering have developed techniques for producing nanoscopic light sources for different applications such as imaging, detection and fabrication. These areas include near-field scanning optical microscopy (NSOM), surface-enhanced Raman scattering and detection (SERS), plasmonics and so on. In particular nanolithography techniques have been developed to produce feature sizes in the sub-100 nm length scales. These processes include variations of standard photolithography process to achieve high resolution, optical fiber-based near-field lithography, surface plasmon assisted nanolithography, interference optical lithography and so on. This work presents a study of the viability of using nanoscale bowtie apertures for nanolithography. Bowtie apertures exhibit a unique property of supporting a propagating TE10 mode at wavelengths of light in the visible and near-UV regimes. The energy of this mode is concentrated in the gap region of the aperture and thus these apertures have the potential to produce high intensity nanoscale light spots that can be used for nano-patterning applications. We demonstrate this capability of nanoscale bowtie apertures by patterning photoresist to obtain resolution less than 100 nm. Initially we present the results from static lithography experiments and show that the ridge apertures of different shapes -- C, H and bowtie produce holes in the photoresist of dimensions around 50-60 nm. Subsequently we address the issues involved in using these apertures for nano directwriting. We show that chromium thin-films offer a viable solution to produce high quality metal films of surface roughness less than 1 nm over an area of 25 mum2. This is indeed important to achieve intimate contact between the apertures and the photoresist surface. We also explain ways to decrease friction between the mask and photoresist surfaces during nano direct-writing. In addition, to decrease the contact force needed to bring an array of bowtie apertures into intimate contact with the photoresist surface we present an optical interference based alignment system that aligns the mask and photoresist surfaces to within 0.1 mrad of parallelism. In this work we show that bowtie apertures can be used to produce patterns in the photoresist of dimensions in the order of 85-90 nm. We also demonstrate parallel optical nanolithography using an array of bowtie apertures that opens up the possibility of using arrays of bowtie apertures to produce a large number of nanoscale light spots for parallel nano-manufacturing.

  19. Variable-aperture screen

    DOEpatents

    Savage, G.M.

    1991-10-29

    Apparatus is described for separating material into first and second portions according to size including a plurality of shafts, a plurality of spaced disks radiating outwardly from each of the shafts to define apertures and linkage interconnecting the shafts for moving the shafts toward or away from one another to vary the size of the apertures while the apparatus is performing the separating function. 10 figures.

  20. High-performance blazed GxLTM device for large-area laser projector

    Microsoft Academic Search

    Yasuyuki Ito; Kunihiko Saruta; Hiroto Kasai; Masato Nishida; Masanari Yamaguchi; Keitaro Yamashita; Ayumu Taguchi; Kazunao Oniki; Hitoshi Tamada

    2006-01-01

    A blazed GxL device is described that has high optical efficiency (>70% for RGB lasers), and high contrast ratio (> 10,000:1), and that is highly reliable when used in a large-area laser projection system. The key features were a robust design and precise stress control technology to maintain a uniform shape (bow and tilt) of more than 6,000 ribbons, a

  1. Short Cavity DBR Laser Using Vertical Groove Gratings for Large-Scale Photonic Integrated Circuits

    Microsoft Academic Search

    Boudewijn Docter; Toru Segawa; Takaaki Kakitsuka; Shinji Matsuo; Tetsuyoshi Ishii; Yoshihiro Kawaguchi; Yasuhiro Kondo; Hiroyuki Suzuki; Fouad Karouta; Meint K. Smit

    2007-01-01

    We present a novel compact distributed Bragg reflector (DBR) laser using InP-InGaAsP deep ridge waveguides with vertical groove gratings. Stable single-mode laser operation was achieved with an active cavity length down to 25 mum and a threshold current of 14 mA. The devices are promising building blocks in large-scale photonic integrated circuits because of their simple structure and low power

  2. Self-similar erbium-doped fiber laser with large normal dispersion.

    PubMed

    Liu, Hui; Liu, Zhanwei; Lamb, Erin S; Wise, Frank

    2014-02-15

    We report a large normal dispersion erbium-doped fiber laser with self-similar pulse evolution in the gain fiber. The cavity is stabilized by the local nonlinear attractor in the gain fiber through the use of a narrow filter. Experimental results are accounted for by numerical simulations. This laser produces 3.5 nJ pulses, which can be dechirped to 70 fs with an external grating pair. PMID:24562267

  3. Large angle and high linearity two-dimensional laser scanner based on voice coil actuators

    NASA Astrophysics Data System (ADS)

    Wu, Xin; Chen, Sihai; Chen, Wei; Yang, Minghui; Fu, Wen

    2011-10-01

    A large angle and high linearity two-dimensional laser scanner with an in-house ingenious deflection angle detecting system is developed based on voice coil actuators direct driving mechanism. The specially designed voice coil actuators make the steering mirror moving at a sufficiently large angle. Frequency sweep method based on virtual instruments is employed to achieve the natural frequency of the laser scanner. The response shows that the performance of the laser scanner is limited by the mechanical resonances. The closed-loop controller based on mathematical model is used to reduce the oscillation of the laser scanner at resonance frequency. To design a qualified controller, the model of the laser scanner is set up. The transfer function of the model is identified with MATLAB according to the tested data. After introducing of the controller, the nonlinearity decreases from 13.75% to 2.67% at 50 Hz. The laser scanner also has other advantages such as large deflection mirror, small mechanical structure, and high scanning speed.

  4. Z-Beamlet: a multikilojoule, terawatt-class laser system

    SciTech Connect

    Rambo, Patrick K.; Smith, Ian C.; Porter, John L. Jr.; Hurst, Michael J.; Speas, C. Shane; Adams, Richard G.; Garcia, Antonio J.; Dawson, Ellis; Thurston, Benjamin D.; Wakefield, Colleen; Kellogg, Jeff W.; Slattery, Michael J.; Ives III, Harry C.; Broyles, Robin S.; Caird, John A.; Erlandson, Alvin C.; Murray, James E.; Behrendt, William C.; Neilsen, Norman D.; Narduzzi, Joseph M

    2005-04-20

    A large-aperture (30-cm) kilojoule-class Nd:glass laser system known as Z-Beamlet has been constructed to perform x-ray radiography of high-energy-density science experiments conducted on the Z facility at Sandia National Laboratories, Albuquerque, New Mexico. The laser, operating with typical pulse durations from 0.3 to 1.5 ns, employs a sequence of successively larger multipass amplifiers to achieve up to 3-kJ energy at 1054 nm. Large-aperture frequency conversion and long-distance beam transport can provide on-target energies of up to 1.5 kJ at 527 nm.

  5. Closed-loop Results from the MMT's Multi-Laser Guide Star Adaptive Optics System

    Microsoft Academic Search

    Michael Lloyd-Hart; Christoph Baranec; N. Mark Milton; Thomas Stalcup; M. Snyder

    2007-01-01

    Key advances in adaptive optics (AO) for both astronomical and military applications will be enabled through the deployment of multiple laser guide stars on a single large-aperture telescope. Wider compensated fields of view than are now seen with conventional AO systems, even those equipped with single laser beacons, will be achieved with less field dependence of the delivered point-spread function.

  6. Large area laser surface treatment of aluminium alloys for pitting corrosion protection

    NASA Astrophysics Data System (ADS)

    Chong, P. H.; Liu, Z.; Skeldon, P.; Thompson, G. E.

    2003-03-01

    Laser surface treatment has been recognised as a useful method for corrosion protection of surfaces as a result of improved microstructure/phase formation and compositions. In large area applications, overlapping of individual tracks corresponding to the width of the laser beam is often necessary. This involves re-melting and re-heating of a portion of the previous track and results in microstructural changes, such as precipitate coarsening and microsegregation, which may influence localised corrosion at the overlapped regions. The purpose of this work is to investigate the influence of overlapped regions on corrosion behaviour of laser-melted aluminium 2014-T6 alloy. Laser melting was carried out using a 3 kW CW Nd:YAG laser with a line beam profile. The microstructures of the central part and the overlapped region of the melt pool were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Pitting corrosion resistance was evaluated using potentiodynamic anodic polarisation in 1 M NaCl solution. The work revealed enhancement of the pitting potential by 170 mV compared with that of the untreated alloy, similar to that achieved by laser surface melting with a CO 2 laser in a Gaussian mode. The line beam profile results in elimination of the planar front zones at the treated surface, but this benefit was offset by a coarser microstructure.

  7. FUNDAMENTAL STUDIES OF IGNITION PROCESSES IN LARGE NATURAL GAS ENGINES USING LASER SPARK IGNITION

    SciTech Connect

    Azer Yalin; Morgan Defoort; Bryan Willson

    2005-01-01

    The current report details project progress made during the first quarterly reporting period of the DOE sponsored project ''Fundamental studies of ignition processes in large natural gas engines using laser spark ignition''. The goal of the overall research effort is to develop a laser ignition system for natural gas engines, with a particular focus on using fiber optic delivery methods. In this report we present our successful demonstration of spark formation using fiber delivery made possible though the use of novel coated hollow fibers. We present results of (high power) experimental characterizations of light propagation using hollow fibers using both a high power research grade laser as well as a more compact laser. Finally, we present initial designs of the system we are developing for future on-engine testing using the hollow fibers.

  8. OSNR enhancement utilizing large effective area fiber in a multiwavelength Brillouin-Raman fiber laser

    NASA Astrophysics Data System (ADS)

    Sonee Shargh, R.; Al-Mansoori, M. H.; Anas, S. B. A.; Sahbudin, R. K. Z.; Mahdi, M. A.

    2011-02-01

    We propose a simple Brillouin-Raman multi-channel fiber laser with supportive Rayleigh scattering in a linear cavity without employing any feedback mirrors at the end of cavity. Brillouin and the consequences of Rayleigh scattering work as virtual mirrors. We employ a section of large effective area fiber in addition to a section of dispersion compensating fiber to enhance the optical signal-to-noise ratio of multi-channel Brillouin-Raman comb fiber laser. We able to produce a flat comb fiber laser with 37 nm bandwidth from 1539 to 1576 nm built-in 460 Stokes lines with 0.08 nm spacing. Furthermore, this Brillouin-Raman comb fiber laser has acceptable optical signal-to-noise ratio value of 16.8 dB for the entire bandwidth with excellent flatness and low discrepancies in power levels of about 2.3 dB between odd and even channels.

  9. Beam characteristics of a large-bore copper laser with a radiatively cooled plasma

    SciTech Connect

    Chang, J.J.; Boley, C.D.; Molander, W.A.; Warner, B.E. [Lawrence Livermore National Lab., CA (United States); Martinez, M.W. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States)

    1994-01-18

    In a large-bore copper vapor laser (CVL), excessive gas heating at the axial region of the discharge lowers its efficiency by thermally populating the metastable lower laser levels. The associated lower gas density also lengthens the discharge field-diffusion time, leading to weaker axial pumping and undesired beam characteristics. The authors` laboratory has developed a novel approach to circumvent this obstacle by cooling the plasma radiatively via a series of segmented metal plates (septa) placed vertically along the length of the tube. This improved tube design significantly lowers the average gas temperature and shortens the radial delay. A 27% increase in laser power was observed with the addition of septa. The authors have characterized the beam intensity profile, spatial and temporal pulse variation, and beam polarization through extensive laboratory measurements. A detailed computational model of the laser has been used to characterize and interpret the laboratory results.

  10. Laser ablation and contact formation for Cu-plated large area C-silicon industrial solar cells

    Microsoft Academic Search

    J. L. Herna?ndez; C. Allebe?; L. Tous; J. John; J. Poortmans

    2010-01-01

    In this work we demonstrate the successful implementation of laser ablation of SiNx ARC to contact high ohmic emitters up to 120 ?\\/sq with an advanced metallization on large area substrates. We propose Suns-Voc measurements as a fast and effective method to characterize the potential laser damage. We look at the laser ablation factors that can compromise the solar cell

  11. Large-Scale Production of Single-Walled Carbon Nanotubes Using Ultrafast Pulses from a Free Electron Laser

    Microsoft Academic Search

    P. C. Eklund; B. K. Pradhan; U. J. Kim; Q. Xiong; J. E. Fischer; A. D. Friedman; B. C. Holloway; M. W. Smith

    2002-01-01

    We report the first use of ultrafast (subpicosecond) laser pulses for large-scale production of single wall carbon nanotubes (SWNT's) by the pulsed laser vaporization (PLV) technique. Very high production rates were achieved; using only 20% of the nominal average power of the 1 kW Jefferson Lab free electron laser (Jlab FEL), carbon soots rich in high quality bundles of SWNT's

  12. Development of large capacity holographic memory using blue laser

    NASA Astrophysics Data System (ADS)

    Okubo, Kaito; Nagao, Yuta; Nakajima, Akihito; Ozawa, Shouhei; Yamamoto, Manabu

    2012-06-01

    The method to do an shift multiplexing by using spherical reference light was examined. The density growth can be expected by overwriting the hologram using spherical reference light. The hologram recording is carried out by shifting the block where the multiplexed hologram was recorded. In addition, a further large capacity can be expected by using the transmission type together with the reflection type hologram recording. In this paper, the result of verifying fundamental proof of these methods was reported by the record reproduction experiment.

  13. Design of scanning spherical trireflector antennas with high aperture efficiency

    NASA Technical Reports Server (NTRS)

    Shen, Bing; Stutzman, Warren L.

    1993-01-01

    It is frequently desirable to scan the main beam of a large antenna system without moving the main aperture structure. Spherical reflectors have excellent potential in this application. However, they are not commonly used because of poor aperture efficiency and high side lobes in traditional implementations. This paper introduces a new dual-subreflector feed system design which does not require oversizing the spherical main reflector to accommodate scan and yet permits a controlled aperture illumination. The design yields high aperture efficiency, low cross-polarization, and low side lobes.

  14. Multiple aperture window and seeker concepts for endo KEW applications

    SciTech Connect

    Shui, V.H.; Reeves, B.L.; Thyson, N.A.; Mueffelmann, W.H.; Werner, J.S.; Jones, G. (Textron Defense Systems, Wilmington, MA (United States) Loral Infrared and Imaging Systems, Lexington, MA (United States) U.S. Army, Strategic Defense Command, Huntsville, AL (United States))

    1992-05-01

    Hypersonic interceptors performing endoatmospheric hit-to-kill missions require very high seeker angle measurement accuracies in very severe aero-thermal environments. Wall jet window/aperture cooling usually leads to significant aero-optic degradation in seeker and hence interceptor performance. This paper describes window/aperture concepts that have the potential of eliminating or significantly reducing the need for coolant injection, together with a multiple aperture sensor concept that can provide a high angle measurement accuracy and a large field of regard, with a small aperture size. 15 refs.

  15. Radius of Curvature Measurement of Large Optics Using Interferometry and Laser Tracker

    NASA Technical Reports Server (NTRS)

    Hagopian, John; Connelly, Joseph

    2011-01-01

    The determination of radius of curvature (ROC) of optics typically uses either a phase measuring interferometer on an adjustable stage to determine the position of the ROC and the optics surface under test. Alternatively, a spherometer or a profilometer are used for this measurement. The difficulty of this approach is that for large optics, translation of the interferometer or optic under test is problematic because of the distance of translation required and the mass of the optic. Profilometry and spherometry are alternative techniques that can work, but require a profilometer or a measurement of subapertures of the optic. The proposed approach allows a measurement of the optic figure simultaneous with the full aperture radius of curvature.

  16. Large-amplitude fluctuations due to longitudinal mode coupling in diode-pumped intracavity-doubled Nd:YAG lasers

    Microsoft Academic Search

    T. Baer

    1986-01-01

    The output of a laser-diode-pumped Nd:YAG laser with an intracavity-doubling crystal exhibits large-amplitude fluctuations and longitudinal-mode instabilities. The results of an experimental and theoretical investigation of these instabilities are described. The instabilities arise from coupling of the longitudinal modes of the laser oscillator by sum-frequency generation in the nonlinear crystal. A rate-equation theory of a multilongitudinal-mode laser oscillator with an

  17. Relative intensity noise transfer of large-bandwidth pump lasers in Raman fiber

    E-print Network

    Boyer, Edmond

    Relative intensity noise transfer of large-bandwidth pump lasers in Raman fiber amplifiers Kafing, such incoherent pumping sources must be considered for the purpose of low-noise Raman amplifiers. © 2006 Optical transfer for a fiber Raman amplifier when the pump beam has a bandwidth that may be much larger than

  18. Measuring earth rate perturbations with a large passive ring laser gyro

    Microsoft Academic Search

    James R. Rotge; Gerald L. Shaw; Harry W. Emrick

    1986-01-01

    The large (about 60 sq m) Passive Resonant Ring Laser Gyroscope (LPRRLG) now under design and construction at the Frank J. Seiler Research Laboratory is discussed. Detector shot noise calculations show this instrument has the potential for measuring changes in effective rotation rates of a few parts in 10 to the 10th for averaging times of a few seconds. A

  19. Large-scale high-resolution 3D laser scanner for solder-paste inspection

    Microsoft Academic Search

    Jef L. Horijon; Fred C. Couweleers; Willem D. van Amstel

    1996-01-01

    An industrial 3D laser scanner is presented for measurement of solder paste screening quality in an automated PCB assembly line. The scanner provides telecentric illumination and imaging in a 305 mm (12') long scan line at a maximum rate of more than 1000 scans per second. Synchronized height measurement is performed using a double triangulation scheme at large angles and

  20. High-resolution adaptive optics scanning laser ophthalmoscope with dual deformable mirrors for large aberration correction

    Microsoft Academic Search

    Diana C. Chen; Steven M. Jones; Dennis A. Silva; Scot S. Olivier

    2007-01-01

    Scanning laser ophthalmoscopes with adaptive optics (AOSLO) have been shown previously to provide a noninvasive, cellular-scale view of the living human retina. However, the clinical utility of these systems has been limited by the available deformable mirror technology. In this paper, we demonstrate that the use of dual deformable mirrors can effectively compensate large aberrations in the human retina, making

  1. Large area deposition of YBa2Cu3O7-x films by pulsed laser ablation

    Microsoft Academic Search

    B. Schey; T. Bollmeier; M. Kuhn; W. Biegel; B. Stritzker

    1998-01-01

    A special patented design is built up to produce homogeneous YBa2Cu3O7-x (YBCO) films by pulsed laser deposition (PLD) over areas as large as 7×20 cm2. The use of a line focus (8 cm) reduces the substrate movement to one dimension. The demands on plasma homogenization, substrate scanning and film temperature during the deposition process for large area PLD are discussed

  2. Large signal nonlinear distortion prediction for a single-mode laser diode under microwave intensity modulation

    Microsoft Academic Search

    1987-01-01

    The large-signal nonlinear distortions from a directly-modulated single-mode GaAlAs laser diode are closely predicted by using a large-signal equivalent circuit model. Criteria for determining intrinsic parameter values are described. The simulations are done in the time domain and then transformed to the frequency domain by FFT. Second harmonics, two-tone third-order intermodulation, multicarrier intermodulation, and intermodulation due to two arbitrarily separated

  3. Varying FM rates in adaptive processing for distributed radar apertures

    Microsoft Academic Search

    Earnest Lock; Raviraj S. Adve

    2007-01-01

    Previous work in waveform diversity for distributed apertures for target detection has focused largely on orthogonal transmissions. This paper investigates an alternative approach; implementing waveform diversity based on differing slopes of the linear FM pulse to the application of target detection for a distributed radar aperture system in the presence of noise and clutter. This paper add develop the required

  4. Ballistic effusion of normal liquid 3 He through nanoscale apertures

    E-print Network

    Packard, Richard E.

    Ballistic effusion of normal liquid 3 He through nanoscale apertures A. Marchenkov, R. W. Simmonds is decreased we observe the crossover from viscous flow to ballistic effusion transport by quasiparticles. In this ballistic regime the quasiparticle mean free path is large compared to both the aperture diameter

  5. LLNL medical and industrial laser isotope separation: large volume, low cost production through advanced laser technologies

    SciTech Connect

    Comaskey, B.; Scheibner, K. F.; Shaw, M.; Wilder, J.

    1998-09-02

    The goal of this LDRD project was to demonstrate the technical and economical feasibility of applying laser isotope separation technology to the commercial enrichment (>lkg/y) of stable isotopes. A successful demonstration would well position the laboratory to make a credible case for the creation of an ongoing medical and industrial isotope production and development program at LLNL. Such a program would establish LLNL as a center for advanced medical isotope production, successfully leveraging previous LLNL Research and Development hardware, facilities, and knowledge.

  6. Optofluidic laser for dual-mode sensitive biomolecular detection with a large dynamic range

    NASA Astrophysics Data System (ADS)

    Wu, Xiang; Oo, Maung Kyaw Khaing; Reddy, Karthik; Chen, Qiushu; Sun, Yuze; Fan, Xudong

    2014-04-01

    Enzyme-linked immunosorbent assay (ELISA) is a powerful method for biomolecular analysis. The traditional ELISA employing light intensity as the sensing signal often encounters large background arising from non-specific bindings, material autofluorescence and leakage of excitation light, which deteriorates its detection limit and dynamic range. Here we develop the optofluidic laser-based ELISA, where ELISA occurs inside a laser cavity. The laser onset time is used as the sensing signal, which is inversely proportional to the enzyme concentration and hence the analyte concentration inside the cavity. We first elucidate the principle of the optofluidic laser-based ELISA, and then characterize the optofluidic laser performance. Finally, we present the dual-mode detection of interleukin-6 using commercial ELISA kits, where the sensing signals are simultaneously obtained by the traditional and the optofluidic laser-based ELISA, showing a detection limit of 1?fg?ml-1 (38?aM) and a dynamic range of 6 orders of magnitude.

  7. Aperture averaging analysis and aperture shape invariance of received scintillation in free-space optical communication links

    NASA Astrophysics Data System (ADS)

    Yuksel, Heba; Davis, Christopher C.

    2006-08-01

    Intensity scintillation and beam wander caused by atmospheric turbulence are two significant phenomena that affect free space optical (FSO) communication links. We have constructed an imaging system for measuring the effects of atmospheric turbulence and obscuration on FSO links. A He-Ne laser beam propagates over a range of 863 meters in atmospheric turbulence conditions that vary diurnally and seasonally from weak to strong. A high performance digital camera with a frame-grabbing computer interface is used to capture received laser intensity distributions at rates up to 30 frames per second and various short shutter speeds, down to 1/16,000s per frame. The captured image frames are analyzed in Labview to evaluate the turbulence index parameter, temporal and spatial intensity variances, and aperture averaging. The aperture averaging results demonstrate the expected reduction in intensity fluctuations with increasing aperture diameter, and show quantitatively the differences in behavior between various strengths of turbulence. This paper will present the most accurate empirical data to date for the weak and intermediate turbulence regime. Such results can help build upon existing empirical data and lead to the development of new theories. Aperture averaging of the received irradiance is also shown to be independent of the shape of the receiver aperture, and depends only on its area. This finding allows the use of refractive or catadioptric receivers, whichever is convenient, and the same amount of aperture averaging will be achieved for equal unobscured aperture areas. This can make the telescope design for an FSO receiver more compact.

  8. Large Scale Laser Two-Photon Polymerization Structuring for Fabrication of Artificial Polymeric Scaffolds for Regenerative Medicine

    Microsoft Academic Search

    M. Malinauskas; V. Purlys; A. Zukauskas; M. Rutkauskas; P. Danilevicius; D. Paipulas; G. Bickauskaite; L. Bukelskis; D. Baltriukiene; R. Sirmenis; A. Gaidukeviciute; V. Bukelskiene; R. Gadonas; V. Sirvydis; A. Piskarskas

    2010-01-01

    We present a femtosecond Laser Two-Photon Polymerization (LTPP) system of large scale three-dimensional structuring for applications in tissue engineering. The direct laser writing system enables fabrication of artificial polymeric scaffolds over a large area (up to cm in lateral size) with sub-micrometer resolution which could find practical applications in biomedicine and surgery. Yb:KGW femtosecond laser oscillator (Pharos, Light Conversion. Co.

  9. Bistatic synthetic aperture radar

    Microsoft Academic Search

    A. M. Horne; G. Yates

    2002-01-01

    Synthetic aperture radar (SAR) is becoming increasingly important in many military ground surveillance and targeting roles because of its ability to operate in all weather, day and night, and to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and receiver are on separate platforms, is seen as a potential means of countering vulnerability. This

  10. Optica aperture synthesis

    Microsoft Academic Search

    Casper van der Avoort

    2006-01-01

    Optical long baseline stellar interferometry is an observational technique in astronomy that already exists for over a century, but is truly blooming during the last decades. The undoubted value of stellar interferometry as a technique to measure stellar parameters beyond the classical resolution limit is more and more spreading to the regime of synthesis imaging. With optical aperture synthesis imaging,

  11. Apertures & Viewpoints Hank Dietz

    E-print Network

    Dietz, Henry G. "Hank"

    a colorcoded aperture to directly capture a "3D" Anaglyph with a single shot, one lens Apparently used in Vivitar Qdos lens #12;My SingleShot Anaglyphs Anaglyph encodes left/right views by color Impose an appropriately colorshaped PSF and the anaglyph is directly captured Transformation from anaglyph into full

  12. Distributed aperture OFDM radar

    Microsoft Academic Search

    Byung Wook Jung; R aviraj S. Adve; Joohwan Chun

    2009-01-01

    This paper presents a new method of obtaining frequency diversity using orthogonal frequency division multiplexing (OFDM). Exploiting spatial diversity, the key advantage of a distributed aperture radar, requires orthogonality in, for example, the frequency, time, waveform, dimensions across sensors. This paper focuses on the simplest of these cases; frequency orthogonality. Here we address the key drawback associated with frequency diversity:

  13. High-energy dissipative solitons generation from a large normal dispersion Er-fiber laser.

    PubMed

    Tang, M; Wang, H; Becheker, R; Oudar, J-L; Gaponov, D; Godin, T; Hideur, A

    2015-04-01

    We report on a passively mode-locked erbium-doped fiber laser featuring a large normal dispersion and emitting high-energy dissipative solitons. Mode-locking is stabilized by the combined actions of a high nonlinearity amplitude modulator and a narrow band spectral filter. The laser routinely delivers highly chirped pulses with more than 38 nJ energy that can be compressed down to 700 fs duration using bulk gratings. Numerical simulations confirm the experimental results and reveal the self-similar pulse evolution along the normal dispersion fibers included inside the cavity. PMID:25831346

  14. Breaking and Moving Hotspots in a Large Grain Nb Cavity with a Laser Beam

    SciTech Connect

    Ciovati, G.; Cheng, G.; Flood, R. J.; Jordan, K.; Kneisel, P.; Morrone, M. L.; Turlington, L.; Wilson, K. M.; Zhang, S.; Anlage, S. M.; Gurevich, A. V.; Nemes, G.; Baldwin, C.

    2011-07-25

    Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.

  15. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  16. Aperture effects in squid jet propulsion.

    PubMed

    Staaf, Danna J; Gilly, William F; Denny, Mark W

    2014-05-01

    Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at a low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) because of a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect might be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes. PMID:24501132

  17. Implementation of swept synthetic aperture imaging

    NASA Astrophysics Data System (ADS)

    Bottenus, Nick; Jakovljevic, Marko; Boctor, Emad; Trahey, Gregg E.

    2015-03-01

    Ultrasound imaging of deep targets is limited by the resolution of current ultrasound systems based on the available aperture size. We propose a system to synthesize an extended effective aperture in order to improve resolution and target detectability at depth using a precisely-tracked transducer swept across the region of interest. A Field II simulation was performed to demonstrate the swept aperture approach in both the spatial and frequency domains. The adaptively beam-formed system was tested experimentally using a volumetric transducer and an ex vivo canine abdominal layer to evaluate the impact of clutter-generating tissue on the resulting point spread function. Resolution was improved by 73% using a 30.8 degree sweep despite the presence of varying aberration across the array with an amplitude on the order of 100 ns. Slight variations were observed in the magnitude and position of side lobes compared to the control case, but overall image quality was not significantly degraded as compared by a simulation based on the experimental point spread function. We conclude that the swept aperture imaging system may be a valuable tool for synthesizing large effective apertures using conventional ultrasound hardware.

  18. Multi-kW single fiber laser based on an extra large mode area fiber design

    NASA Astrophysics Data System (ADS)

    Langner, Andreas; Such, Mario; Schötz, Gerhard; Just, Florian; Leich, Martin; Schwuchow, Anka; Grimm, Stephan; Zimer, Hagen; Kozak, Marcin; Wedel, Björn; Rehmann, Georg; Bachert, Charley; Krause, Volker

    2012-02-01

    The quality of Yb-doped fused bulk silica produced by sintering of Yb-doped fused silica granulates has improved greatly in the past five years [1 - 4]. In particular, the refractive index and doping level homogeneity of such materials are excellent and we achieved excellent background fiber attenuation of the active core material down to about 20 dB/km at 1200 nm. The improvement of the Yb-doped fused bulk silica has enabled the development of multi-kW fiber laser systems based on a single extra large multimode laser fiber (XLMA fiber). When a single active fiber is used in combination with the XLMA multimode fiber of 1200 ?m diameter simple and robust high power fiber laser setups without complex fiber coupling and fiber combiner systems become possible. In this papper, we will discuss in detail the development of the core material based on Yb-doped bulk silica and the characterization of Yb-doped fibers with different core compositions. We will also report on the excellent performance of a 4 kW fiber laser based on a single XLMA-fiber and show the first experimental welding results of steel sheets achieved with such a laser.

  19. Scientific-research institute of radiophysics (SRIR) decimeter-wavelength aperture synthesis system

    Microsoft Academic Search

    V. S. Beagon; N. A. Dugin; A. A. Romanychev; L. R. Semenova; V. I. Turchin; N. M. Tseitlin

    1983-01-01

    The method of aperture synthesis started to be applied in radio astronomy approximately from the middle of the 1950's, and several large instruments have been placed into operation up to the present time in different countries of the world (one can find a review of aperture synthesis systems in [i], for example). In domestic radioastronomical technology aperture synthesis instruments have

  20. Aperture center energy showcase

    SciTech Connect

    Torres, J. J.

    2012-03-01

    Sandia and Forest City have established a Cooperative Research and Development Agreement (CRADA), and the partnership provides a unique opportunity to take technology research and development from demonstration to application in a sustainable community. A project under that CRADA, Aperture Center Energy Showcase, offers a means to develop exhibits and demonstrations that present feedback to community members, Sandia customers, and visitors. The technologies included in the showcase focus on renewable energy and its efficiency, and resilience. These technologies are generally scalable, and provide secure, efficient solutions to energy production, delivery, and usage. In addition to establishing an Energy Showcase, support offices and conference capabilities that facilitate research, collaboration, and demonstration were created. The Aperture Center project focuses on establishing a location that provides outreach, awareness, and demonstration of research findings, emerging technologies, and project developments to Sandia customers, visitors, and Mesa del Sol community members.

  1. Integrated electrochromic aperture diaphragm

    NASA Astrophysics Data System (ADS)

    Deutschmann, T.; Oesterschulze, E.

    2014-05-01

    In the last years, the triumphal march of handheld electronics with integrated cameras has opened amazing fields for small high performing optical systems. For this purpose miniaturized iris apertures are of practical importance because they are essential to control both the dynamic range of the imaging system and the depth of focus. Therefore, we invented a micro optical iris based on an electrochromic (EC) material. This material changes its absorption in response to an applied voltage. A coaxial arrangement of annular rings of the EC material is used to establish an iris aperture without need of any mechanical moving parts. The advantages of this device do not only arise from the space-saving design with a thickness of the device layer of 50?m. But it also benefits from low power consumption. In fact, its transmission state is stable in an open circuit, phrased memory effect. Only changes of the absorption require a voltage of up to 2 V. In contrast to mechanical iris apertures the absorption may be controlled on an analog scale offering the opportunity for apodization. These properties make our device the ideal candidate for battery powered and space-saving systems. We present optical measurements concerning control of the transmitted intensity and depth of focus, and studies dealing with switching times, light scattering, and stability. While the EC polymer used in this study still has limitations concerning color and contrast, the presented device features all functions of an iris aperture. In contrast to conventional devices it offers some special features. Owing to the variable chemistry of the EC material, its spectral response may be adjusted to certain applications like color filtering in different spectral regimes (UV, optical range, infrared). Furthermore, all segments may be switched individually to establish functions like spatial Fourier filtering or lateral tunable intensity filters.

  2. Ion shock acceleration by large amplitude slow ion acoustic double layers in laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Eliasson, B.

    2014-02-01

    A kinetic model for the shock acceleration of ions in laser-produced plasmas is developed. A fraction of the warm ions are accelerated by the large amplitude monotonic potential of the shock created due the plasma compression and electron heating by the laser. The kinetic model for the monotonic shock is based on the slow ion acoustic double layer (SIADL). It is found that the amplitude of the large amplitude SIADL is almost uniquely defined by the electron temperature. Therefore, a balance between electron heating and plasma compression is needed for optimal ion acceleration by this scheme. Typical Mach numbers of the monotonic shocks are close to 1.5. The scheme could potentially produce monoenergetic ions with a relative energy spread of less than 1%. The model is compared with recent simulations and experiments, where efficient shocks acceleration and production of monoenergetic protons have been observed. Similarities and differences with other shock models are pointed out and discussed.

  3. Ion shock acceleration by large amplitude slow ion acoustic double layers in laser-produced plasmas

    SciTech Connect

    Eliasson, B. [SUPA, Physics Department, University of Strathclyde, John Anderson Building, Glasgow G4 0NG (United Kingdom)] [SUPA, Physics Department, University of Strathclyde, John Anderson Building, Glasgow G4 0NG (United Kingdom)

    2014-02-15

    A kinetic model for the shock acceleration of ions in laser-produced plasmas is developed. A fraction of the warm ions are accelerated by the large amplitude monotonic potential of the shock created due the plasma compression and electron heating by the laser. The kinetic model for the monotonic shock is based on the slow ion acoustic double layer (SIADL). It is found that the amplitude of the large amplitude SIADL is almost uniquely defined by the electron temperature. Therefore, a balance between electron heating and plasma compression is needed for optimal ion acceleration by this scheme. Typical Mach numbers of the monotonic shocks are close to 1.5. The scheme could potentially produce monoenergetic ions with a relative energy spread of less than 1%. The model is compared with recent simulations and experiments, where efficient shocks acceleration and production of monoenergetic protons have been observed. Similarities and differences with other shock models are pointed out and discussed.

  4. Large-scale three-dimensional measurement via combining 3D scanner and laser rangefinder.

    PubMed

    Shi, Jinlong; Sun, Zhengxing; Bai, Suqin

    2015-04-01

    This paper presents a three-dimensional (3D) measurement method of large-scale objects by integrating a 3D scanner and a laser rangefinder. The 3D scanner, used to perform partial section measurement, is fixed on a robotic arm which can slide on a guide rail. The laser rangefinder, used to compute poses of the 3D scanner, is rigidly connected to the 3D scanner. During large-scale measurement, after measuring a partial section, the 3D scanner is straightly moved forward along the guide rail to measure another section. Meanwhile, the poses of the 3D scanner are estimated according to its moved distance for different partial section alignments. The performance and effectiveness are evaluated by experiments. PMID:25967194

  5. Synthetic aperture wavefront sensing

    NASA Astrophysics Data System (ADS)

    Bará, Salvador; Arines, Justo; Pailos, Eliseo

    2014-06-01

    We propose the synthetic aperture wavefront sensing approach. It is based on acquiring several sets of measurements of the wavefront slopes by displacing sequentially the microlens array with respect to the unknown wavefront. These measurements are stacked together and processed as if obtained with a single-sampling array with an effective number of subpupils equal to the product of the number of microlenses by the number of displacements. We analyze and compare the performance of this approach with the method of modal coefficient averaging. The comparison is made in terms of the squared wavefront reconstruction error, spatially averaged over the pupil and statistically averaged over the noise and the aberrations of the population. We focused our attention on its applications to eye aberrometry. Our numerical results were obtained for a population statistics consistent with a wide sample of young adult eyes using different sampling grids and with several signal-to-noise ratios. They indicate that the synthetic aperture wavefront sensing is affected by less bias and noise propagation than the averaging method, providing smaller mean-squared estimation error. The number of complete Zernike radial orders that can be estimated using the synthetic aperture approach is consistently higher than that allowed by the conventional method.

  6. Assembly of a large modular optical telescope (ALMOST)

    E-print Network

    Mohan, Swati

    Future space telescope programs need to assess in-space robotic assembly of large apertures at GEO and ESL2 to support ever increasing aperture sizes. Since such large apertures will not fit within a fairing, they must ...

  7. Quasi two-dimensional model of large-bore Cu lasers

    Microsoft Academic Search

    V. V. Ivanov; Konstantin Klopovsky; Yuri A. Mankelevich; Sergei A. Motovilov; N. A. Popov; O. V. Proshina; T. V. Rakhimova; Nikolay V. Suetin; A. A. Yudin; Boris P. Yatsenko

    2002-01-01

    Quasi two-dimensional (r,z) model of large bore copper vapor laser (CVL) was developed. Full set of heat and species (charged and neutral) transfer equations, Maxwell equations and electron energy balance equation were solved for different pulse repetition rate in a temporally self- consistent manner, with the long term evolution of plasma kinetics followed over multiple excitation\\/afterglow cycles. Electron rate constants

  8. Edge effect studies of a large area cathode for the Electra KrF laser

    Microsoft Academic Search

    F. Hegeler; M. Friedman; M. C. Myers; J. D. Sethian; S. B. Swanekamp

    2001-01-01

    Summary form only given. Electra is a repetitively pulsed, electron beam pumped krypton fluoride (KrF) laser that will be used to develop the technology required for an inertial fusion energy (IFE) power plant. The electron beams are generated by large area cathodes (2,500 to 10,000 cm2). This-paper presents experimental results on the spatial and temporal current distribution at the anode

  9. Automatic Recognition of Piping System from Large-Scale Terrestrial Laser Scan Data

    NASA Astrophysics Data System (ADS)

    Kawashima, K.; Kanai, S.; Date, H.

    2011-09-01

    Recently, changes in plant equipment have been becoming more frequent because of the short lifetime of the products, and constructing 3D shape models of existing plants (as-built models) from large-scale laser scanned data is expected to make their rebuilding processes more efficient. However, the laser scanned data of the existing plant has massive points, captures tangled objects and includes a large amount of noises, so that the manual reconstruction of a 3D model is very time-consuming and costs a lot. Piping systems especially, account for the greatest proportion of plant equipment. Therefore, the purpose of this research was to propose an algorithm which can automatically recognize a piping system from terrestrial laser scan data of the plant equipment. The straight portion of pipes, connecting parts and connection relationship of the piping system can be recognized in this algorithm. Eigenvalue analysis of the point clouds and of the normal vectors allows for the recognition. Using only point clouds, the recognition algorithm can be applied to registered point clouds and can be performed in a fully automatic way. The preliminary results of the recognition for large-scale scanned data from an oil rig plant have shown the effectiveness of the algorithm.

  10. Cooperative stimulated Brillouin scattering driven by overlapping, large spot laser beams

    NASA Astrophysics Data System (ADS)

    Kruer, William; Kirkwood, Robert; Michel, Pierre; Turnbull, David

    2013-10-01

    In NIF hohlraums, large regions of plasma are irradiated with intense overlapping and large spot laser beams. In this regime, cooperative excitation of stimulated scattering can become a significant effect. Indeed, the potential importance of cooperative scattering has already been illustrated in calculations of cross beam energy transfer, where many crossing laser beams enhance the energy of another beam- a form of (generally nonresonant) cooperative SBS in the forward direction. Similarly, cooperative interactions are thought to play some role in scattering in the backward direction. Here we consider an interesting special case in which all the beams in a cone resonantly drive an ion sound wave along the hohlraum axis. This results in laser light being scattered backward along the cone. The frequency of this scattered light differs from that of the light directly backscattered by each beam, although there may be cross talk if the frequency of the backscattered light is sufficiently broad. A simple theory is presented, and some experiments to isolate and characterize cooperative scattering are discussed. In NIF hohlraums, large regions of plasma are irradiated with intense overlapping and large spot laser beams. In this regime, cooperative excitation of stimulated scattering can become a significant effect. Indeed, the potential importance of cooperative scattering has already been illustrated in calculations of cross beam energy transfer, where many crossing laser beams enhance the energy of another beam- a form of (generally nonresonant) cooperative SBS in the forward direction. Similarly, cooperative interactions are thought to play some role in scattering in the backward direction. Here we consider an interesting special case in which all the beams in a cone resonantly drive an ion sound wave along the hohlraum axis. This results in laser light being scattered backward along the cone. The frequency of this scattered light differs from that of the light directly backscattered by each beam, although there may be cross talk if the frequency of the backscattered light is sufficiently broad. A simple theory is presented, and some experiments to isolate and characterize cooperative scattering are discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

  11. A New Approach for Structural Monitoring of Large Dams with a Three-Dimensional Laser Scanner

    PubMed Central

    González-Aguilera, Diego; Gómez-Lahoz, Javier; Sánchez, José

    2008-01-01

    Driven by progress in sensor technology, computer methods and data processing capabilities, 3D laser scanning has found a wide range of new application fields in recent years. Particularly, monitoring the static and dynamic behaviour of large dams has always been a topic of great importance, due to the impact these structures have on the whole landscape where they are built. The main goal of this paper is to show the relevance and novelty of the laserscanning methodology developed, which incorporates different statistical and modelling approaches not considered until now. As a result, the methods proposed in this paper have provided the measurement and monitoring of the large “Las Cogotas” dam (Avila, Spain).

  12. Optical Transmission Properties of Dielectric Aperture Arrays

    NASA Astrophysics Data System (ADS)

    Yang, Tao

    Optical detection devices such as optical biosensors and optical spectrometers are widely used in many applications for the functions of measurements, inspections and analysis. Due to the large dimension of prisms and gratings, the traditional optical devices normally occupy a large space with complicated components. Since cheaper and smaller optical devices are always in demand, miniaturization has been kept going for years. Thanks to recent fabrication advances, nanophotonic devices such as semiconductor laser chips have been growing in number and diversity. However, the optical biosensor chips and the optical spectrometer chips are seldom reported in the literature. For the reason of improving system integration, the study of ultra-compact, low-cost, high-performance and easy-alignment optical biosensors and optical spectrometers are imperative. This thesis is an endeavor in these two subjects and will present our research work on studying the optical transmission properties of dielectric aperture arrays and developing new optical biosensors and optical spectrometers. The first half of the thesis demonstrates that the optical phase shift associated with the surface plasmon (SP) assisted extraordinary optical transmission (EOT) in nano-hole arrays fabricated in a metal film has a strong dependence on the material refractive index value in close proximity to the holes. A novel refractive index sensor based on detecting the EOT phase shift is proposed by building a model. This device readily provides a 2-D biosensor array platform for non-labeled real-time detection of a variety of organic and biological molecules in a sensor chip format, which leads to a high packing density, minimal analyte volumes, and a large number of parallel channels while facilitating high resolution imaging and supporting a large space-bandwidth product (SBP). Simulation (FDTD Solutions, Lumerical Solutions Inc) results indicate an achievable sensitivity limit of 4.37x10-9 refractive index units (RIU) and a dynamic range as large as 0.17 RIU. Subsequently, optical transmission properties through a self-mixing interferometer array are studied and a novel high-resolution cost-effective optical spectrometer is proposed. The miniature interferometer-based spectrometer is made of polymethyl methacrylate (PMMA) with a CCD as the detector. The detected intensity of each CCD pixels contains the spectral information. Since each frequency component in the incoming beam corresponds to a unique phase difference of the two beam portions of each optical interferometer, the total intensity received by each CCD pixel, which is resulted from the addition of the interference signals from all the frequency components in the beam, should also be unique. Therefore, the spectrum calculation is a problem to solve an ill-posed linear system by using Tikhonov regularization method. Simulation results show that the resolution can reach picometer level. Apart from the choice of path difference between the interfering beams, the spectral resolution also depends on the signal-to-noise ratio and analogue-digital conversion resolution (dynamic range) of the CCD chip. In addition, the theory of uniform waveguide scattering is explored to expand the possibility of using such mini-interferometers for performing free-space spectral analysis of waveguide devices. At the same time, the method of least squares is used to correct the pixel non-uniformity of the CCD so as to improve the performance of the spectrometer. The sensor chip and spectrometer chip introduced here are based on the interference of light transmitted through dielectric aperture arrays. Their compact feature renders these devices ideal for miniaturization and integration as the systems in microfluidics architectures and lab-on-chip designs.

  13. Aperture shape optimization for IMRT treatment planning

    NASA Astrophysics Data System (ADS)

    Cassioli, A.; Unkelbach, J.

    2013-01-01

    We propose an algorithm for aperture shape optimization (ASO) for step and shoot delivery of intensity-modulated radiotherapy. The method is an approach to direct aperture optimization (DAO) that exploits gradient information to locally optimize the positions of the leafs of a multileaf collimator. Based on the dose-influence matrix, the dose distribution is locally approximated as a linear function of the leaf positions. Since this approximation is valid only in a small interval around the current leaf positions, we use a trust-region-like method to optimize the leaf positions: in one iteration, the leaf motion is confined to the beamlets where the leaf edges are currently positioned. This yields a well-behaved optimization problem for the leaf positions and the aperture weights, which can be solved efficiently. If, in one iteration, a leaf is moved to the edge of a beamlet, the leaf motion can be confined to the neighboring beamlet in the next iteration. This allows for large leaf position changes over the course of the algorithm. In this paper, the ASO algorithm is embedded into a column-generation approach to DAO. After a new aperture is added to the treatment plan, we use the ASO algorithm to simultaneously optimize aperture weights and leaf positions for the new set of apertures. We present results for a paraspinal tumor case, a prostate case and a head and neck case. The computational results indicate that, using this approach, treatment plans close to the ideal fluence map optimization solution can be obtained.

  14. Impact of a large negative gain-to-cavity wavelength detuning on the performance of InGaAlAs oxide-confined vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Blokhin, Sergey A.; Bobrov, Mikhail A.; Maleev, Nikolai A.; Kuzmenkov, Alexander G.; Sakharov, Alexey V.; Blokhin, Alexey A.; Moser, Philip; Lott, James A.; Bimberg, Dieter; Ustinov, Viktor M.

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) based on the InGaAlAs-materials system on GaAs substrates are the key component for short-reach data and computer communications systems. Several different modulation schemes have been developed to realize high data bit rates based on various oxide-confined near-infrared VCSEL designs operated under direct current modulation. However, one open question to resolve is the optimal gain-to-cavity wavelength detuning to employ for temperature-stable high-speed performance. We investigate the static and dynamic characteristics of 850 nm high-speed oxide-confined VCSELs with different negative gain-to-cavity wavelength detunings. Our oxideconfined 850 nm VCSELs with a more common ~10 nm negative gain-to-cavity detuning demonstrate the conventional optical mode behavior with a classical single-resonance frequency response. With a larger (? 20 nm) negative detuning, our devices with large oxide-aperture size (>6 ?m) show an anomalous start of lasing via higher order modes with a subsequent switching to lasing via the lowest order modes at higher currents. At intermediate currents, co-lasing via two types of transverse modes and a two-resonance modulation response is observed. The increase of operation temperature as well as the reduction in the oxide-aperture area resulted in classical lasing of index-guided VCSELs. The observed optical mode behavior can be attributed to the specific index guiding profile caused by the oxide-apertures, low internal optical losses, and the large gain-to-cavity detuning. Moreover, one can suggest that the complex shape of the modulation response results from the mode competition for the available gain during an interesting co-lasing operating regime.

  15. Wind Scanner: A full-scale Laser Facility for Wind and Turbulence Measurements around large Wind Turbines

    E-print Network

    Wind Scanner: A full-scale Laser Facility for Wind and Turbulence Measurements around large Wind measurements of the wind fields engulfing today's huge wind turbines. Our aim is to measure in real- time 3D have named "The Remote Sensing Full Scale Laser Wind Scanner Facility", viz.: The recent advent

  16. A tip\\/tilt mirror with large dynamic range for the ESO VLT Four Laser Guide Star Facility

    Microsoft Academic Search

    N. Rijnveld; R. Henselmans; B. Nijland

    2011-01-01

    One of the critical elements in the Four Laser Guide Star Facility (4LGSF) for the ESO Very Large Telescope (VLT) is the Optical Tube Assembly (OTA), consisting of a stable 20x laser beam expander and an active tip\\/tilt mirror, the Field Selector Mechanism (FSM). This paper describes the design and performance testing of the FSM. The driving requirement for the

  17. The spatial thickness distribution of metal films produced by large area pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Pryds, Nini; Schou, Jørgen; Linderoth, Søren

    2007-07-01

    Thin films of metals have been deposited in the large-area Pulsed Laser Deposition (PLD) Facility at Risø National Laboratory. Thin films of Ag and Ni were deposited with laser pulses from an excimer laser at 248 nm with a rectangular beam spot at a fluence of 10 J/cm 2 on glass substrates of 127 mm diameter positioned 80 mm from the target in vacuum. We have explored the distribution of deposited material on a stationary substrate from a fixed point of impact on the target relative to the substrate. In all cases the angular distribution of the deposited metal layers shows a distinct "flip-over" of the plume. The thickness of the deposited films over the full area has been determined by energy-dispersive X-ray spectrometry in a scanning electron microscope (SEM). The measured distributions were then compared with analytical expressions. Finally, the angular distribution of the film thickness has been utilized in an algorithm for production of films over large areas.

  18. Vertical emitting aperture nanoantennas.

    PubMed

    Yaacobi, Ami; Timurdogan, Erman; Watts, Michael R

    2012-05-01

    Herein we propose, theoretically investigate, and numerically demonstrate a compact design for a vertical emitter at a wavelength of 1.5 ?m based on nanophotonic aperture antennas coupled to a dielectric waveguide. The structure utilizes a plasmonic antenna placed above a Si3N4 waveguide with a ground plane for breaking the up-down symmetry and increasing the emission efficiency. Three-dimensional (3-D) finite-difference time-domain (FDTD) simulations reveal that up to 60% vertical emission efficiency is possible in a structure only four wavelengths long with a 3 dB bandwidth of over 300 nm. PMID:22555702

  19. Two-dimensional laser-optical concentration measurement in a large subsonic wind tunnel

    SciTech Connect

    Leitl, B. [Univ. of Dresden (Germany). Fluid Mechanics Dept.

    1995-12-31

    The present study was carried out in the subsonic wind tunnel of the Technical University of Dresden. A modified two-dimensional laser-optical concentration measurement technique for measuring within large planes has been developed. Using a laser light sheet, light scattering by small glycerine-water-droplets and digital image processing, concentrations can be measured within a plane of a flow field nonintrusively. The light scattered by particles moved within the light sheet is recorded using a CCD-camera. Using the developed software package OPTOKONZ the recordings can be corrected corresponding to the actual recording conditions without questionable calibrating images. Both time averaged concentrations and temporary recordings can be converted to concentration fields. The resulting data have the advantage of being both quantitative and visually interpretable. First results and comparisons with conventional concentrations measurements agree quite well.

  20. Broadly tunable multiwavelength fiber laser with bismuth-oxide EDF using large effective area fiber

    NASA Astrophysics Data System (ADS)

    Ramzia Salem, A. M.; Al-Mansoori, M. H.; Hizam, H.; Mohd Noor, S. B.; Mahdi, M. A.

    2011-02-01

    A multiwavelength laser comb using 2.49 m Bismuth-oxide erbium-doped fiber (Bi-EDF) with different lengths of large effective area fiber (LEAF) in a ring cavity configuration is realized. The Bi-EDF is used as the linear gain medium and LEAF is used as the non-linear gain medium for stimulated Brillouin scattering. Out of the four different lengths, the longest length of 25 km LEAF exhibits the widest tuning range of 44 nm (1576 to 1620 nm) in the L-band at 264 mW pump power and 5 mW Brillouin pump power. In addition, a total of 15 output channels are achieved with total average output power of -8 dBm from this laser structure. All Brillouin Stokes signals exhibit high peak power of above -20 dBm per signal and their optical signal-to-noise ratio of greater than 15 dB.

  1. 3D reconstruction of large target by range gated laser imaging

    NASA Astrophysics Data System (ADS)

    Li, Sining; Yan, Xu; Wang, Wei; Zhang, Dayong; Lu, Wei

    2014-11-01

    We have developed a whole set of range gated laser imaging system with ~3km maximum acquisition distance, the system uses a Nd:YAG electro-optical Q-switched 532nm laser as transmitter, a double micro channel plate as gated sensor, all the components are controlled by the a trigger control unit with accuracy of subnanosecond. A imaging scheme is designed for imaging the large building ~500m away, and a sequence of images are obtained in the experiment, which are the basic data for 3D reconstruction; to improve the range resolution, we study the temporal distribution of intensity of the received signal, and use centroid algorithm for data processing. We compare the 3D image with the theoretical model, and the results are corresponding.

  2. Numerical aperture dependence of damage and supercontinuum generation from femtosecond

    E-print Network

    Schaffer, Chris B.

    the critical power for self-focusing. © 2006 Optical Society of America OCIS codes: 320.2250, 260.5950, 140 pulse-induced damage is an intensity- dependent effect, self-focusing makes the unambiguousNumerical aperture dependence of damage and supercontinuum generation from femtosecond laser pulses

  3. Fiber Handling and Numerical Aperture Measurement To become familiar with fiber cleaving and the relation between

    E-print Network

    Collins, Gary S.

    Fiber Handling and Numerical Aperture Measurement Purpose: To become familiar with fiber cleaving · 16 7 socket/driver For the laser- HeNe laser short rod clamp (340C) laser mount for the fiber- · F-MLD fiber ( ~2 meters) · rotation stage · very small "micro-series" post holder · very small "micro

  4. Large-Spot Material Interactions with a High-Power Solid-State Laser Beam

    SciTech Connect

    Boley, C D; Fochs, S N; Rubenchik, A M

    2008-08-06

    We study the material interactions produced by the beam of a 25-kW solid-state laser, in experiments characterized by relatively large spot sizes ({approx}3 cm) and the presence of airflow. The targets are iron or aluminum slabs, of thickness 1 cm. In the experiments with iron, we show that combustion plays an important role in heating the material. In the experiments with aluminum, we observe a sharp transition from no melting to complete melt-through as the intensity on target increases. A layer of paint greatly reduces the requirements for melt-through. We explain these effects and incorporate them into an overall computational model.

  5. Development of a laser-based measurement system for modal testing of large space structures

    NASA Astrophysics Data System (ADS)

    Mitchell, A. K.; Hazell, C. R.; Soucy, Y.

    1991-10-01

    Conventional modal testing methods using rigidly mounted accelerometers to obtain the response of vibrating structures are considered inappropriate for testing of large space structures because of inherent mass loading effects and insufficient sensitivity at very low frequencies. As a result, a noncontacting vibration measuring system was developed based on a commercially available single channel laser vibrometer. Using two acoustooptic modulators as very rapid switching devices, it is expected that the single channel system can be expanded to accomodate up to 50 channels of virtually simultaneous vibration data via time division multiplexing. The modulators are computer controlled and allow random or sequential access to each channel. A working 10 channel system was successfully demonstrated.

  6. Selectively etched undercut apertures in AlAsSb-based VCSELs

    Microsoft Academic Search

    E. Hall; S. Nakagawa; G. Almuneau; J. K. Kim; L. A. Coldren

    2001-01-01

    Apertures were formed in single-growth, AsSb-based, long-wavelength (1.55 ?m) vertical-cavity surface-emitting lasers by laterally etching the active region. The materials contrast between the AlAsSb-based mirrors and the AlInGaAs-based active region leads to a high selectivity for the etch, allowing long apertures to be formed with minimal etching of the mirrors. Lasers showing reduced threshold currents and increased efficiencies were demonstrated

  7. Large spectral tuning of liquid microdroplets by local heating with a focused infrared laser

    NASA Astrophysics Data System (ADS)

    Kiraz, Alper; Karada?, Yasin; Yorulmaz, Saime Ç.; Murado?lu, Metin

    2008-08-01

    Large deformations can easily be introduced in liquid microdroplets by applying relatively small external forces or controlling the evaporation/condensation kinetics. This makes liquid microdroplets attractive to serve as the building blocks of largely tunable optical switches or filters that are essential in optical communication systems based on wavelength division multiplexing. Solid optical microcavities have not found large use in these applications, mainly due to their rigid nature. The fact that liquid microdroplets are low-cost and disposable can also prove to be important in mass production of these photonic devices. Here, we show that local heating with an infrared laser can be used to largely tune the whispering gallery modes (WGMs) of water/glycerol or salty water microdroplets standing on a superhydrophobic surface. In the scheme presented, a liquid microdroplet kept in a humidity chamber is stabilized on a superhydrophobic surface, and an infrared laser beam is focused near the center of the microdroplet. As a result of the local heating, the temperature of the liquid microdroplet increases, and the water content in the liquid microdroplet evaporates until a new equilibrium is reached. At the new equilibrium state, the non-volatile component (i.e. glycerol or salt) attains a higher concentration in the liquid microdroplet. We report tunability over large spectral ranges up to 30 nm at around 590 nm. For salty water microdroplets the reported spectral tuning mechanism is almost fully reversible, while for the case of glycerol/water microdroplets the spectral tuning mechanism can be made highly reversible when the chamber is saturated with glycerol vapor and the relative water humidity approaches unity.

  8. Large Aperture Systems: 2000-2004

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This custom bibliography from the NASA Scientific and Technical Information Program lists a sampling of records found in the NASA Aeronautics and Space Database. The scope of this topic includes technologies for next generation astronomical telescopes and detectors. This area of focus is one of the enabling technologies as defined by NASA s Report of the President s Commission on Implementation of United States Space Exploration Policy, published in June 2004.

  9. Large Aperture Multiplexed Diffractive Lidar Optics

    NASA Technical Reports Server (NTRS)

    Rallison, Richard D.; Schwemmer, Geary K. (Technical Monitor)

    1999-01-01

    We have delivered only 2 or 3 UV Holographic Optical Elements (HOEs) thus far and have fallen short of the intended goal in size and in dual wavelength function. Looking back, it has been fortuitous that we even made anything work in the UV region. It was our good fortune to discover that the material we work with daily was adequate for use at 355 nm, if well rinsed during processing. If we had stuck to our original plan of etching in small pieces of fused silica, we would still be trying to make the first small section in our ion mill, which is not yet operational. The original plan was far too ambitious and would take another 2 years to complete beginning where we left off this time. In order to make a HOE for the IR as well as the UV we will likely have to learn to sensitize some film to the 1064 line and we have obtained sensitizer that is reported to work in that region already. That work would also take an additional year to complete.

  10. Material Measurements Using Groundplane Apertures

    NASA Technical Reports Server (NTRS)

    Komisarek, K.; Dominek, A.; Wang, N.

    1995-01-01

    A technique for material parameter determination using an aperture in a groundplane is studied. The material parameters are found by relating the measured reflected field in the aperture to a numerical model. Two apertures are studied which can have a variety of different material configurations covering the aperture. The aperture cross-sections studied are rectangular and coaxial. The material configurations involved combinations of single layer and dual layers with or without a resistive exterior resistive sheet. The resistivity of the resistive sheet can be specified to simulate a perfect electric conductor (PEC) backing (0 Ohms/square) to a free space backing (infinity Ohms/square). Numerical parameter studies and measurements were performed to assess the feasibility of the technique.

  11. Initiation, Growth and Mitigation of UV Laser Induced Damage in Fused Silica

    SciTech Connect

    Rubenchik, A M; Feit, M D

    2003-06-10

    Laser damage of large fused silica optics initiates at imperfections. Possible initiation mechanisms are considered. We demonstrate that a model based on nanoparticle explosions is consistent with the observed initiation craters. Possible mechanisms for growth upon subsequent laser irradiation, including material modification and laser intensification, are discussed. Large aperture experiments indicate an exponential increase in damage size with number of laser shots. Physical processes associated with this growth and a qualitative explanation of self-accelerated growth is presented. Rapid growth necessitates damage growth mitigation techniques. Several possible mitigation techniques are mentioned, with special emphasis on CO{sub 2} processing. Analysis of material evaporation, crack healing, and thermally induced stress are presented.

  12. Initiation, Growth and Mitigation of UV Laser Induced Damage in Fused Silica

    SciTech Connect

    Rubenchik, A M; Feit, M D

    2001-12-21

    Laser damage of large fused silica optics initiates at imperfections. Possible initiation mechanisms are considered. We demonstrate that a model based on nanoparticle explosions is consistent with the observed initiation craters. Possible mechanisms for growth upon subsequent laser irradiation, including material modification and laser intensification, are discussed. Large aperture experiments indicate an exponential increase in damage size with number of laser shots. Physical processes associated with this growth and a qualitative explanation of self-accelerated growth is presented. Rapid growth necessitates damage growth mitigation techniques. Several possible mitigation techniques are mentioned, with special emphasis on CO{sub 2} processing. Analysis of material evaporation, crack healing, and thermally induced stress are presented.

  13. Multiple instrument distributed aperture sensor (MIDAS) evolved design concept

    Microsoft Academic Search

    David Stubbs; Alan Duncan; Joseph T. Pitman; Robert Sigler; Rick Kendrick; Eric H. Smith; James Mason

    2004-01-01

    An innovative approach to future space telescopes that enables order of magnitude increased science return for astronomical, Earth-observing and planetary science missions is described. Our concept, called Multiple Instrument Distributed Aperture Sensor (MIDAS), provides a large-aperture, wide-field, diffraction-limited telescope at a fraction of the cost, mass and volume of conventional space telescopes. MIDAS integrates many optical interferometry advances as an

  14. Scanning reflection and transmission photometer for large high power laser optics

    SciTech Connect

    Thomas, N.L.; Robinson, W.L.; Wirtenson, G.R.; Wallerstein, E.P.

    1981-12-11

    The Nova OTR (overall transmittance/reflectance) photometer operates at 1.064 nm, 528 nm, or 351 nm in order to closely simulate 1st, 2nd and 3rd harmonic frequencies of the Nova fusion laser. The optic is scanned on a large XY carriage while reflectance or transmittance data is taken on-the-fly. The system is controlled by an LSI 11/23 computer which processes the data and prints out the results in hard copy form, or stores data on a memory disk. The detectors are temperature controlled to within +- 0.01/sup 0/C which aids in achieving of an absolute accuracy of +- 0.1 to +- 0.5% of full scale, depending on the operating point. The photometer is capable of scanning a large optic (1 meter in diameter) in 20 to 30 minutes.

  15. Rotational long-period signals: From Ring Laser Data to Large Seismic Networks Array Derived Rotations.

    NASA Astrophysics Data System (ADS)

    Nader, M.; Bernauer, M.; Wassermann, J.; Ferreira, A. M.; Schreiber, U.; Igel, H.

    2012-04-01

    Rotational seismology is a recent and promising ?eld in active development that focuses on the study of all aspects concerning rotational ground motions induced by earthquakes, explosions, and ambient vibrations among others. The understanding of rotational ground motions is relevant to several disciplines: seismology, earthquake engineering, exploration geophysics, and even the decoupling of sensitive structures from ground motions (e.g., gravitational wave detection). Here, we show two different approaches in the attempt to obtain additional information from long period signals induced by rotational seismic motions. We show recent results in regards to long period data achieved using Ring Laser technology based on the Sagnac effect. The Ring Laser Data potential for long period seismology was proven useful as a complement to traditional measurements in the study of Earth free oscillations generated by Toroidal eigen-modes. In this study, we show evidence of possible coupling observations between Spheroidal and Toroidal modes in the rotational spectra recorded by the G-Ring laser located at the Geodetic Observatory Wettzell (Germany), measuring the vertical component of rotation rate. Additionally, we explore the possibility of long-period studies based on the array derivation of rotation. Although array derived rotations have been mainly used for strong-motion studies, we show that this method could be also applied in the low frequency range of seismic signals generated for large earthquakes if the network is dense enough. The seismic network used in this study is the USArray transportable seismic network. It consists of 400 broadband seismometers placed in a regular grid pattern across the United States with station spacing of about 70 km. ,We compare the two approaches for the most recent large earthquakes in order to get a better understanding of how long-period seismology studies can bene?t from rotational ground motion measurements in the future.

  16. Large diameter dual-axis MEMS-based mirror for laser beam steering

    NASA Astrophysics Data System (ADS)

    Ilias, S.; Picard, F.; Le Foulgoc, K.; Osouf, J.; Larouche, C.; Caron, J.-S.; Topart, P.; Garcia Blanco, S.; Vincent, D.; Lepage, J. F.; Gilbert, B.

    2011-03-01

    The main goals of this work is the development of a large dual-axis MEMS mirror, ~3mm in diameter, capable of steering a laser beam within an angular cone of 60°. The targeted application involves the control of a laser beam with a particular interest for the resulting far field beam direction and profile. Finite element simulations using ANSYS modeling program were conducted to optimize the mirror design and determine the main characteristics of the mirror. The voltage required to tilt the mirror by 15° around each of the two axes was evaluated to be in the range of 700 V. The construction of this device is based on high precision structural dies assembly which relies on innovative developments in the fields of selective electroplating, deep reactive ion etching (DRIE) and thermocompression flip-chip bonding. The fabrication process involved the microassembly of 4 mirror parts, i.e. address electrodes, thick pedestal, gimbals structure and mirror plate. Single crystal silicon was used as material for the fabrication of the thick pedestal and mirror plate which provided the required large mirror-electrode gap and a high quality mirror with high flatness and low roughness. Soldering based on SnAu was considered for the microassembly of the thick pedestal to the address electrodes die, while Au-Au thermocompression bonding was considered to achieve the assembly of gimbals and mirror. The gimbals were supported by a polyimide sacrificial film to avoid damaging the hinges during mirror plate assembly.

  17. Fracture-aperture alteration induced by calcite precipitation

    NASA Astrophysics Data System (ADS)

    Jones, T.; Detwiler, R. L.

    2013-12-01

    Mineral precipitation significantly alters the transport properties of fractured rock. Chemical solubility gradients that favor precipitation induce mineral growth, which decreases the local aperture and alters preferential flow paths. Understanding the resulting development of spatial heterogeneities is necessary to predict the evolution of transport properties in the subsurface. We present experimental results that quantify the relationship between mineral precipitation and aperture alteration in a transparent analog fracture, 7.62cm x 7.62cm, with a uniform aperture of ~200 ?m. Prior to flow experiments, a pump circulated a super-saturated calcite solution over the bottom glass, coating the glass surface with calcite. This method of seeding resulted in clusters of calcite crystals with large reactive surface area and provided micro-scale variability in the aperture field. A continuous flow syringe pump injected a reactive fluid into the fracture at 0.5 ml/min. The fluid was a mixture of sodium bicarbonate (NaHCO3, 0.02M) and calcium chloride (CaCl2 0.0004M) with a saturation index, ?, of 8.51 with respect to calcite. A strobed LED panel backlit the fracture and a high-resolution CCD camera monitored changes in transmitted light intensity. Light transmission techniques provided a quantitative measurement of fracture aperture over the flow field. Results from these preliminary experiments showed growth near the inlet of the fracture, with decreasing precipitation rates in the flow direction. Over a period of two weeks, the fracture aperture decreased by 17% within the first 4mm of the inlet. Newly precipitated calcite bridged individual crystal clusters and smoothed the reacting surface. This observation is an interesting contradiction to the expectation of surface roughening induced by mineral growth. Additionally, the aperture decreased uniformly across the width of the fracture due to the initial aperture distribution. Future experiments of precipitation within variable-aperture fields will investigate the dependency of growth patterns on heterogeneous aperture distributions. (a) Aperture strain (?b/bi) after 14 days. Precipitation is concentrated near the inlet and decreases in the flow direction. (b) Width-averaged profiles of the initial and final aperture field show changes in aperture and smoothing that results from calcite precipitation between the initial discrete crystals.

  18. High-power laser diodes using a large active core combined with mode control for high beam quality

    NASA Astrophysics Data System (ADS)

    Pai, David M.

    2015-03-01

    This paper presents a high power laser diode method using a large core combined with mode control. The large core allows for high power, while the mode control in an external cavity maintains the beam quality. Analysis shows beam quality can be kept at the ideal diffraction limit for cores as large as 100 microns (transverse dimensions). Such size cores can support hundreds of watts. This means a new class of laser diodes with brightness levels several orders higher than current devices. Such capabilities are unheard of and will have an overwhelming effect on applications.

  19. DAVINCI: Dilute Aperture VIsible Nulling Coronagraphic Imager

    NASA Technical Reports Server (NTRS)

    Shao, Michael; Levine, B. M.; Vasisht, G.; Lane, B. F.; Woodruff, R.; Vasudevan, G.; Samuele, R.; Lloyd, C. A.; Clampin, M.; Lyon, R.; Guyon, O.

    2008-01-01

    This slide presentation gives an overview of DAVINCI (Dilute Aperture VIsible Nulling Coronagraphic Imager). The presentation also includes information about dilute aperture coronagraph, and lyot efficiency.

  20. Versatile method for achieving 1% speckle contrast in large-venue laser projection displays using a stationary multimode optical fiber.

    PubMed

    Manni, Jeffrey G; Goodman, Joseph W

    2012-05-01

    We propose a method based on quantitative theoretical analysis for achieving speckle contrast of 1% or less in images created by a full-frame laser projection display system. The method employs a stationary multimode optical fiber to achieve the effect of using a rapidly moving diffuser, but without moving the fiber or any other system component. When a suitably large projector lens is used, low-speckle illumination light delivered through the fiber acts in conjunction with wavelength diversity at the projection screen to achieve speckle contrast of 1% in viewed images. We describe in detail how the proposed method might be used with most types of high-power visible lasers being considered for large-venue displays. When used with visible laser diodes, the method may also be suitable for use in laser-based television. PMID:22565751

  1. Development of large scale production of Nd-doped phosphate glasses for megajoule-scale laser systems

    SciTech Connect

    Ficini, G. [Centre d`Etudes de Limeil-Valenton, Villeneuve, St. Georges (France); Campbell, J.H. [Lawrence Livermore National Lab., CA (United States)

    1996-05-01

    Nd-doped phosphate glasses are the preferred gain medium for high-peak-power lasers used for Inertial Confinement Fusion research because they have excellent energy storage and extraction characteristics. In addition, these glasses can be manufactured defect-free in large sizes and at relatively low cost. To meet the requirements of the future mega-joule size lasers, advanced laser glass manufacturing methods are being developed that would enable laser glass to be continuously produced at the rate of several thousand large (790 x 440 x 44 mm{sup 3}) plates of glass per year. This represents more than a 10 to 100-fold improvement in the scale of the present manufacturing technology.

  2. Characterization of a high-density large scale pulsed gas jet for laser-gas interaction experiments

    Microsoft Academic Search

    T. Auguste; M. Bougeard; E. Caprin; P. D'Oliveira; P. Monot

    1999-01-01

    We present the characteristics of a high-density pulsed gas jet developed to study the interaction of a short-pulse, high-intensity laser with a large scale underdense plasma. The jet was characterized by laser interferometry. Measurements of density profile were performed for a 5 mm diam cylindrical nozzle and for a 20×1 mm slit. In this latter case, a systematic study of

  3. Large area mapping of non-metallic inclusions in stainless steel by an automated system based on laser ablation

    Microsoft Academic Search

    L. M. Cabal??n; M. P. Mateo; J. J. Laserna

    2004-01-01

    Large area compositional mapping (>6 mm2) using a fast and automated system based on laser-induced plasma spectrometry is presented. The second harmonic of a flat top Nd:YAG laser beam was used to generate a microline plasma on the sample surface. The emitted light from the microline plasma was imaged onto the entrance slit of an imaging spectrograph and was detected

  4. Comparison of pulse evolutions in low and ultra-large anomalous dispersion mode-locked fiber lasers

    Microsoft Academic Search

    L. N. Duan; X. M. Liu; L. R. Wang; D. Mao; G. X. Wang

    2011-01-01

    We have investigated and compared the pulse evolutions in low and ultra-large anomalous dispersion erbium-doped fiber lasers mode-locked by the nonlinear polarization rotation technique. Two lasers deliver the pulses that exhibit quite distinct characteristics such as pulse duration, spectral width, and spectral sidebands. Experimental observations show that the spectral width decreases from several nanometers to less than one nanometer whereas

  5. Comparison of pulse evolutions in low and ultra-large anomalous dispersion mode-locked fiber lasers

    Microsoft Academic Search

    L. N. Duan; X. M. Liu; L. R. Wang; D. Mao; G. X. Wang

    2011-01-01

    We have investigated and compared the pulse evolutions in low and ultra-large anomalous dispersion erbium-doped fiber lasers\\u000a mode-locked by the nonlinear polarization rotation technique. Two lasers deliver the pulses that exhibit quite distinct characteristics\\u000a such as pulse duration, spectral width, and spectral sidebands. Experimental observations show that the spectral width decreases\\u000a from several nanometers to less than one nanometer whereas

  6. Lasers

    Microsoft Academic Search

    Peter W. Milonni; Joseph H. Eberly

    1988-01-01

    Lasers A comprehensive introduction to the operating principles and applications of lasers. Explains basic principles, including the necessary elements of classical and quantum physics. Provides concise discussions of various laser types including gas, solid state, semiconductor, and free electron lasers, as well as of laser resonators, diffraction, optical coherence, and many applications including holography, phase conjugation, wave mixing, and nonlinear

  7. Dipole aperture and superconductor requirements

    SciTech Connect

    Wipf, S.L.

    1983-12-11

    The cost of an accelerator is not proportional to the aperture. A change in aperture by a certain percentage results in an overall accelerator cost change by only a fraction of that percentage; the fraction may be between 0.1 and 0.5 and is almost independent of the bending field. This estimate is obtained by analyzing the superconductor requirements as a function of aperture and by making rough estimates of the largest cost items of the accelerator such as magnets and ring tunnel.

  8. High-power one-, two-, and three-dimensional photonic crystal edge-emitting laser diodes for ultra-high brightness applications

    Microsoft Academic Search

    N. Yu. Gordeev; M. V. Maximov; Y. M. Shernyakov; I. I. Novikov; L. Ya. Karachinsky; V. A. Shchukin; T. Kettler; K. Posilovic; N. N. Ledentsov; D. Bimberg; R. Duboc; A. Sharon; D. B. Arbiv; U. Ben-Ami

    2008-01-01

    Direct laser diodes can typically provide only a limited single mode power, while ultrahigh-brightness is required for many of the market-relevant applications. Thus, multistage power conversion schemes are applied, when the laser diodes are used just as a pumping source. In this paper we review the recent advances in ultra-large output aperture edge-emitting lasers based on the photonic band crystal

  9. The physics of megajoule, large-scale, and ultrafast short-scale laser plasmas

    Microsoft Academic Search

    E. M. Campbell

    1992-01-01

    Recent advances in laser science and technology have opened new possibilities for the study of high energy density plasma physics. The advances include techniques to control the laser spatial and temporal coherence, and the development of laser architectures and optical materials that have led to the demonstration of compact, short pulse (??10?12 sec) high brightness lasers, capable of irradiating plasmas

  10. High-power high-brightness semiconductor lasers

    Microsoft Academic Search

    D. Botez

    2005-01-01

    Broad-stripe (greater than or equal to 100 microns) diode lasers have achieved CW powers as high as 15W, and wallplug efficiencies as high as 70%. For high coherent power photonic-crystal structures with modulated gain, that is active photonic crystals (APCs), of large index steps have been used, as early as 1988, for effective lateral-mode control range in large-aperture (100-200 microns)

  11. Compressive coded aperture imaging

    NASA Astrophysics Data System (ADS)

    Marcia, Roummel F.; Harmany, Zachary T.; Willett, Rebecca M.

    2009-02-01

    Nonlinear image reconstruction based upon sparse representations of images has recently received widespread attention with the emerging framework of compressed sensing (CS). This theory indicates that, when feasible, judicious selection of the type of distortion induced by measurement systems may dramatically improve our ability to perform image reconstruction. However, applying compressed sensing theory to practical imaging systems poses a key challenge: physical constraints typically make it infeasible to actually measure many of the random projections described in the literature, and therefore, innovative and sophisticated imaging systems must be carefully designed to effectively exploit CS theory. In video settings, the performance of an imaging system is characterized by both pixel resolution and field of view. In this work, we propose compressive imaging techniques for improving the performance of video imaging systems in the presence of constraints on the focal plane array size. In particular, we describe a novel yet practical approach that combines coded aperture imaging to enhance pixel resolution with superimposing subframes of a scene onto a single focal plane array to increase field of view. Specifically, the proposed method superimposes coded observations and uses wavelet-based sparsity recovery algorithms to reconstruct the original subframes. We demonstrate the effectiveness of this approach by reconstructing with high resolution the constituent images of a video sequence.

  12. Sparse aperture endoscope

    DOEpatents

    Fitch, J.P.

    1999-07-06

    An endoscope is disclosed which reduces the volume needed by the imaging part, maintains resolution of a wide diameter optical system, while increasing tool access, and allows stereographic or interferometric processing for depth and perspective information/visualization. Because the endoscope decreases the volume consumed by imaging optics such allows a larger fraction of the volume to be used for non-imaging tools, which allows smaller incisions in surgical and diagnostic medical applications thus produces less trauma to the patient or allows access to smaller volumes than is possible with larger instruments. The endoscope utilizes fiber optic light pipes in an outer layer for illumination, a multi-pupil imaging system in an inner annulus, and an access channel for other tools in the center. The endoscope is amenable to implementation as a flexible scope, and thus increases it's utility. Because the endoscope uses a multi-aperture pupil, it can also be utilized as an optical array, allowing stereographic and interferometric processing. 7 figs.

  13. Optica aperture synthesis

    NASA Astrophysics Data System (ADS)

    van der Avoort, Casper

    2006-05-01

    Optical long baseline stellar interferometry is an observational technique in astronomy that already exists for over a century, but is truly blooming during the last decades. The undoubted value of stellar interferometry as a technique to measure stellar parameters beyond the classical resolution limit is more and more spreading to the regime of synthesis imaging. With optical aperture synthesis imaging, the measurement of parameters is extended to the reconstruction of high resolution stellar images. A number of optical telescope arrays for synthesis imaging are operational on Earth, while space-based telescope arrays are being designed. For all imaging arrays, the combination of the light collected by the telescopes in the array can be performed in a number of ways. In this thesis, methods are introduced to model these methods of beam combination and compare their effectiveness in the generation of data to be used to reconstruct the image of a stellar object. One of these methods of beam combination is to be applied in a future space telescope. The European Space Agency is developing a mission that can valuably be extended with an imaging beam combiner. This mission is labeled Darwin, as its main goal is to provide information on the origin of life. The primary objective is the detection of planets around nearby stars - called exoplanets- and more precisely, Earth-like exoplanets. This detection is based on a signal, rather than an image. With an imaging mode, designed as described in this thesis, Darwin can make images of, for example, the planetary system to which the detected exoplanet belongs or, as another example, of the dust disk around a star out of which planets form. Such images will greatly contribute to the understanding of the formation of our own planetary system and of how and when life became possible on Earth. The comparison of beam combination methods for interferometric imaging occupies most of the pages of this thesis. Additional chapters will treat related subjects, being experimental work on beam combination optics, a description of a novel formalism for aberration retrieval and experimental work on nulling interferometry. The Chapters on interferometric imaging are organized in such a way that not only the physical principles behind a stellar interferometer are clear, but these chapters also form a basis for the method of analysis applied to the interferometers - -or rather beam combination methods- under consideration. The imaging process in a stellar interferometer will be treated as the inversion of a linear system of equations. The definition of interferometric imaging in this thesis can be stated to be the reconstruction of a luminosity distribution function on the sky, that is, in angular measure, larger than the angular diffraction limited spot size -or Point-Spread Function (PSF)- of a single telescope in the array and that contains, again in angular measure, spatial structure that is much smaller than the PSF of a single telescope. This reconstruction has to be based on knowledge of the dimensions of the telescope array and the detector. The detector collects intensity data that is formed by observation of the polychromatic luminosity distribution on the sky and is deteriorated by the quantum-nature of light and an imperfect electronic detection process. Therefore, the imaging study presented in this thesis can be regarded to be a study on the signal characteristics of various interferometers while imaging a polychromatic wide-field stellar source. The collection of beam combination methods under consideration consists of four types. Among these are two well-known types, having either co-axially combined beams as in the Michelson-Morley experiment to demonstrate the existence of ether, or beams that follow optical paths as if an aperture mask were placed in front of a telescope, making the beams combine in the focus of that telescope, as suggested by Fizeau. For separated apertures rather than an aperture mask, these optical paths are stated to be homothetic. In short, these two types wi

  14. Development of laser guide stars and adaptive optics for large astronomical telescopes

    Microsoft Academic Search

    C. E. Max; K. Avicola; H. Bissinger; J. M. Brase; D. T. Gavel; H. Friedman; J. R. Morris; S. S. Olivier; D. Rapp; J. T. Salmon; K. Waltjen

    1992-01-01

    We describe a feasibility experiment to demonstrate high-order adaptive optics using a sodium-layer laser guide star. We use the copper-vapor-pumped dye lasers developed for LLNL's atomic Vapor Laser Isotope Separation program to create the laser guide star. Closed-loop adaptive corrections will be accomplished using a 69-subaperture adaptive optics system on a one-meter telescope at LLNL. The laser bream is projected

  15. Reflex ring laser amplifier system

    DOEpatents

    Summers, M.A.

    1983-08-31

    The invention is a method and apparatus for providing a reflex ring laser system for amplifying an input laser pulse. The invention is particularly useful in laser fusion experiments where efficient production of high-energy and high power laser pulses is required. The invention comprises a large aperture laser amplifier in an unstable ring resonator which includes a combination spatial filter and beam expander having a magnification greater than unity. An input pulse is injected into the resonator, e.g., through an aperture in an input mirror. The injected pulse passes through the amplifier and spatial filter/expander components on each pass around the ring. The unstable resonator is designed to permit only a predetermined number of passes before the amplified pulse exits the resonator. On the first pass through the amplifier, the beam fills only a small central region of the gain medium. On each successive pass, the beam has been expanded to fill the next concentric non-overlapping region of the gain medium.

  16. Near-term feasibility demonstration of laser power beaming

    SciTech Connect

    Friedman, H.W.

    1994-01-01

    A mission to recharge batteries of satellites in geostationary orbits (geosats) may be a commercially viable application which could be achieved with laser systems somewhat larger than present state-of-the-art. The lifetime of batteries on geosats is limited by repetitive discharge cycles which occur when the satellites are eclipsed by the earth during the spring and fall equinoxes. By coupling high power lasers with modern, large aperture telescopes and laser guide star adaptive optics systems, present day communications satellites could be targeted. It is important that a near term demonstration of laser power beaming be accomplished using lasers in the kilowatt range so that issues associated with high average power be addressed. The Laser Guide Star Facility at LLNL has all the necessary subsystems needed for such a near term demonstration, including high power lasers for both the power beam and guide star, beam directors and satellite tracking system.

  17. Bore-sight calibration of the profile laser scanner using a large size exterior calibration field

    NASA Astrophysics Data System (ADS)

    Koska, Bronislav; K?emen, Tomáš; Štroner, Martin

    2014-10-01

    The bore-sight calibration procedure and results of a profile laser scanner using a large size exterior calibration field is presented in the paper. The task is a part of Autonomous Mapping Airship (AMA) project which aims to create s surveying system with specific properties suitable for effective surveying of medium-wide areas (units to tens of square kilometers per a day). As is obvious from the project name an airship is used as a carrier. This vehicle has some specific properties. The most important properties are high carrying capacity (15 kg), long flight time (3 hours), high operating safety and special flight characteristics such as stability of flight, in terms of vibrations, and possibility to flight at low speed. The high carrying capacity enables using of high quality sensors like professional infrared (IR) camera FLIR SC645, high-end visible spectrum (VIS) digital camera and optics in the visible spectrum and tactical grade INSGPS sensor iMAR iTracerRT-F200 and profile laser scanner SICK LD-LRS1000. The calibration method is based on direct laboratory measuring of coordinate offset (lever-arm) and in-flight determination of rotation offsets (bore-sights). The bore-sight determination is based on the minimization of squares of individual point distances from measured planar surfaces.

  18. Development and utilization of a laser velocimeter system for a large transonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Freedman, R. J.; Greissing, J. P.

    1982-01-01

    The need for measurements of the velocity flow field about spinner propeller nacelle configurations at Mach numbers to 0.8 was met by a specially developed laser velocimeter system. This system, which uses an argon ion laser and 4 beam 2 color optics, was required to operate in the hostile environment associated with the operation of a large transonic wind tunnel. To overcome the conditions present in locating the sensitive optics in close proximity to the wind tunnel, an isolation system was developed. The system protects the velocimeter from the high vibrations, elevated temperatures, destructive acoustic pressures and low atmospheric pressures attendant with the operation of the wind tunnel. The system was utilized to map the flow field in front of, behind and in between the rotating blades of an advanced swept blade propeller model at a Mach number of 0.8. The data collected by the system will be used to correlate and verify computer analyses of propeller nacelle flow fields and propeller performance.

  19. Space-Time-Waveform Adaptive Processing for Frequency Diverse Distributed Radar Apertures

    Microsoft Academic Search

    Raviraj S. Adve; Lorne Applebaum; Michael C. Wicks; Richard A. Schneible

    2006-01-01

    This paper reviews recent developments in the field of adaptive processing for frequency diverse, distributed, radar apertures. The large baseline of such a distributed radar results in angular resolution that is orders of magnitude better than the resolution of a single large radar. This capability comes at the cost of grating lobes (multistatics with evenly spaced apertures) or high sidelobes

  20. High-energy pulse generation from solid-state ultraviolet lasers using large Ce:fluoride crystals

    NASA Astrophysics Data System (ADS)

    Liu, Zhenlin; Shimamura, Kiyoshi; Fukuda, Tsuguo; Kozeki, Toshimasa; Suzuki, Yuji; Sarukura, Nobuhiko

    2002-02-01

    A large Ce 3+:LiCaAlF 6 (Ce:LiCAF) crystal with 15 mm diameter was grown successfully by the Czochralski method. Owing to its large size, 60 mJ, 289 nm pulses were generated directly from a quasi-coaxially pumped Ce:LiCAF laser. In addition, a new noncollinear Brewster-angle-pumping disk oscillator scheme was demonstrated for further output-energy scaling. An ultraviolet solid-state Ce 3+:LiLuF 4 (Ce:LLF) laser which was pumped transversely by a KrF excimer laser with the repetition rate of 1 Hz produced a 27 mJ, 309 nm pulse using a large Ce:LLF crystal which was grown by the Czochralski method, and the slope efficiency was approximately 17%.

  1. Extension of wavelength-modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases

    SciTech Connect

    Li Hejie; Rieker, Gregory B.; Liu Xiang; Jeffries, Jay B.; Hanson, Ronald K

    2006-02-10

    Tunable diode laser absorption measurements at high pressures by use of wavelength-modulation spectroscopy (WMS) require large modulation depths for optimum detection of molecular absorption spectra blended by collisional broadening or dense spacing of the rovibrational transitions. Diode lasers have a large and nonlinear intensity modulation when the wavelength is modulated over a large range by injection-current tuning. In addition to this intensity modulation, other laser performance parameters are measured, including the phase shift between the frequency modulation and the intensity modulation. Following published theory, these parameters are incorporated into an improved model of the WMS signal. The influence of these nonideal laser effects is investigated by means of wavelength-scanned WMS measurements as a function of bath gas pressure on rovibrational transitions of water vapor near 1388 nm. Lock-in detection of the magnitude of the 2f signal is performed to remove the dependence on detection phase. We find good agreement between measurements and the improved model developed for the 2f component of the WMS signal. The effects of the nonideal performance parameters of commercial diode lasers are especially important away from the line center of discrete spectra, and these contributions become more pronounced for 2f signals with the large modulation depths needed for WMS at elevated pressures.

  2. Large-Scale Hollow Retroreflectors for Lunar Laser Ranging at Goddard Space Flight Center

    NASA Technical Reports Server (NTRS)

    Preston, Alix

    2012-01-01

    Laser ranging to the retroreflector arrays placed on the lunar surface by the Apollo astronauts and the Soviet Luna missions have dramatically increased our understanding of gravitational physics along with Earth and Moon geophysics, geodesy, and dynamics. Although the precision of the range measurements has historically been limited by the ground station capabilities, advances in the APOLLO instrument at the Apache Point facility in New Mexico is beginning to be limited by errors associated with the lunar arrays. We report here on efforts at Goddard Space Flight Center to develop the next generation of lunar retroreflectors. We will describe a new facility that is being used to design, assemble, and test large-scale hollow retroreflectors. We will also describe results from investigations into various bonding techniques used to assemble the open comer cubes and mirror coatings that have dust mitigation properties.

  3. High resolution beamforming for small aperture arrays

    NASA Astrophysics Data System (ADS)

    Clark, Chris; Null, Tom; Wagstaff, Ronald A.

    2003-04-01

    Achieving fine resolution bearing estimates for multiple sources using acoustic arrays with small apertures, in number of wavelengths, is a difficult challenge. It requires both large signal-to-noise ratio (SNR) gains and very narrow beam responses. High resolution beamforming for small aperture arrays is accomplished by exploiting acoustical fluctuations. Acoustical fluctuations in the atmosphere are caused by wind turbulence along the propagation path, air turbulence at the sensor, source/receiver motion, unsteady source level, and fine scale temperature variations. Similar environmental and source dependent phenomena cause fluctuations in other propagation media, e.g., undersea, optics, infrared. Amplitude fluctuations are exploited to deconvolve the beam response functions from the beamformed data of small arrays to achieve high spatial resolution, i.e., fine bearing resolution, and substantial SNR gain. Results are presented for a six microphone low-frequency array with an aperture of less than three wavelengths. [Work supported by U.S. Army Armament Research Development and Engineering Center.

  4. Bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Yates, Gillian

    Synthetic aperture radar (SAR) allows all-weather, day and night, surface surveillance and has the ability to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and the receiver are on separate platforms, is seen as a potential means of countering the vulnerability of conventional monostatic SAR to electronic countermeasures, particularly directional jamming, and avoiding physical attack of the imaging platform. As the receiving platform can be totally passive, it does not advertise its position by RF emissions. The transmitter is not susceptible to jamming and can, for example, operate at long stand-off ranges to reduce its vulnerability to physical attack. This thesis examines some of the complications involved in producing high-resolution bistatic SAR imagery. The effect of bistatic operation on resolution is examined from a theoretical viewpoint and analytical expressions for resolution are developed. These expressions are verified by simulation work using a simple 'point by point' processor. This work is extended to look at using modern practical processing engines for bistatic geometries. Adaptations of the polar format algorithm and range migration algorithm are considered. The principal achievement of this work is a fully airborne demonstration of bistatic SAR. The route taken in reaching this is given, along with some results. The bistatic SAR imagery is analysed and compared to the monostatic imagery collected at the same time. Demonstrating high-resolution bistatic SAR imagery using two airborne platforms represents what I believe to be a European first and is likely to be the first time that this has been achieved outside the US (the UK has very little insight into US work on this topic). Bistatic target characteristics are examined through the use of simulations. This also compares bistatic imagery with monostatic and gives further insight into the utility of bistatic SAR.

  5. Evaluation of a laser scanner for large volume coordinate metrology: a comparison of results before and after factory calibration

    NASA Astrophysics Data System (ADS)

    Ferrucci, M.; Muralikrishnan, B.; Sawyer, D.; Phillips, S.; Petrov, P.; Yakovlev, Y.; Astrelin, A.; Milligan, S.; Palmateer, J.

    2014-10-01

    Large volume laser scanners are increasingly being used for a variety of dimensional metrology applications. Methods to evaluate the performance of these scanners are still under development and there are currently no documentary standards available. This paper describes the results of extensive ranging and volumetric performance tests conducted on a large volume laser scanner. The results demonstrated small but clear systematic errors that are explained in the context of a geometric error model for the instrument. The instrument was subsequently returned to the manufacturer for factory calibration. The ranging and volumetric tests were performed again and the results are compared against those obtained prior to the factory calibration.

  6. On the fabrication of three-dimensional silicon-on-insulator based optical phased array for agile and large angle laser beam steering systems

    E-print Network

    Texas at Austin, University of

    , such as limited steering angles 5° , were discussed in detail in Ref. 2. Applications such as free-space laser optical communications in data centers or laser beam scanning radar systems3 require fast and much larger and large angle laser beam steering systems Amir Hosseini,a David Kwong, and Yang Zhang Microelectronic

  7. Group-velocity dispersion analysis of large mode-area doped fibers implemented in a laser cavity during operation

    NASA Astrophysics Data System (ADS)

    Baselt, T.; Taudt, Ch.; Hartmann, P.

    2015-03-01

    Developments in the field of high-power fiber lasers require extensive knowledge of the fiber structure parameters in various operating states. In an effort to gather such knowledge, this paper presents the results of dispersion characterization measurements using ytterbium-doped large mode area double-clad fibers implemented in the cavity of a high power fiber laser during operation. The laser cavity is built into one arm of a Mach-Zehnder interferometer. Using dichroic mirrors the radiation of a supercontinuum light source is coupled into the fiber sample. Various types of large mode-area fibers were examined under different operating conditions of the laser setup. Group-velocity dispersion characteristics of two large mode-area double-clad fiber amplifiers with various launching laser power levels were analyzed. The dispersion parameters for different fiber designs and various doping levels are investigated over a broad spectral range of about 1.3 ?m. The experiment utilizes a supercontinuum source developed within this laboratory, as well as a Mach-Zehnder interferometer with a dual-channel spectral-detection system sensitive to wavelengths from 0.4 ?m to 1.7 ?m. Temporally resolved spectrograms recorded at distinct delay positions enable the detection of interference fringes for the equalization-wavelength. By applying a Sellmeier polynomial fit to the wavelength dependent differential group-delay function, the group-velocity dispersion has been derived.

  8. The physics of megajoule, large-scale, and ultrafast short-scale laser plasmas

    Microsoft Academic Search

    E. M. Campbell

    1992-01-01

    Recent advances in laser science and technology have opened new possibilities for the study of high energy density plasma physics. The advances include techniques to control the laser spatial and temporal coherence, and the development of laser architectures and optical materials that have led to the demonstration of compact, short pulse ([tau][le]10[sup [minus]12] sec) high brightness lasers, capable of irradiating

  9. Locking lasers with large FM noise to high-Q Lingze Duan and Kurt Gibble

    E-print Network

    Gibble, Kurt

    a conventional servo. A series of experiments has locked diode lasers to successively narrower cavity resonances linewidth is much greater than the cavity linewidth. We lock an external-cavity diode laser with more than 1 is to a narrow cav- ity the free-running laser linewidth may be much greater than the cavity linewidth, so

  10. A CIRCUIT MODEL OF QUANTUM CASCADE LASERS APPLICABLE TO BOTH SMALL AND LARGE CURRENT DRIVES

    Microsoft Academic Search

    M. K. Haldar; J. F. Webb

    2010-01-01

    In this paper, a circuit model is devised to analyze nonlinear behaviour of quantum cascade lasers. Such nonlinear behavior influences the light output when the laser is driven by currents comparable to the average (DC) current. The simplified 2-level rate equations are first improved. Next, the circuit model is obtained following the approach for interband lasers. The difference between the

  11. a Circuit Model of Quantum Cascade Lasers Applicable to both Small and Large Current Drives

    Microsoft Academic Search

    M. K. Haldar; J. F. Webb

    2010-01-01

    In this paper, a circuit model is devised to analyze nonlinear behaviour of quantum cascade lasers. Such nonlinear behavior influences the light output when the laser is driven by currents comparable to the average (DC) current. The simplified 2-level rate equations are first improved. Next, the circuit model is obtained following the approach for interband lasers. The difference between the

  12. First Measurement of Short Length-Scale Density Fluctuations in a Large Laser Plasma

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; MacGowan, B. J.; Glenzer, S. H.; Kirkwood, R. K.; Kruer, W. L.; Schmitt, A. J.; Williams, E. A.; Stone, G. F.

    1999-08-01

    The technique of near forward laser scattering is used for the first time in an ignition-relevant laser plasma to obtain a background and laser driven fluctuation spectrum. The fluctuations cause beam spray which can affect the symmetry in an inertial confinement fusion experiment. These results provide a benchmark for developing numerical models of beam spray.

  13. Evidence for Ureterorenoscopy and Laser Fragmentation (URSL) for Large Renal Stones in the Modern Era.

    PubMed

    Geraghty, Robert; Abourmarzouk, Omar; Rai, Bhavan; Biyani, Chandra Shakhar; Rukin, Nicholas J; Somani, Bhaskar K

    2015-08-01

    Large renal stones (>2 cm) are managed with percutaneous nephrolithotomy (PCNL), which has a good stone-free rate (SFR) but a relatively high incidence of complications graded Clavien ?3. We wanted to review the literature for the use of ureterorenoscopy and laser fragmentation (URSL) for the management of these stones. A systematic review was done from 1990 to April 2014 for all English language articles reporting on a minimum of 10 patients for stones >2 cm in size (done by 2 reviewers independently) in accordance with the PRISMA and Cochrane review guidelines. A total of 379 articles were identified and after screening for the titles (54) and abstracts (29), 12 papers (651 patients) were included. The male to female ratio was 356:232 with a mean age of 54 years (range 16-86 years). With a mean stone size of 2.7 cm (2-3.15 cm) and the mean operating time of 96 min (28-238 min); the SFR was 91 % (1.45 procedures/patient). The overall number of complications was 58 (8.6 %) of which 26 (4.5 %) were complications classed Clavien ?3 (haematuria with subcapsular haematoma/clot retention-7; ureteral perforation-7; steinstrasse-5; sepsis/pyelonephritis-5; prostatitis-1; cerebrovascular accident-1). Ureterorenoscopy for large renal stones in the modern era has good SFR with a small risk of major complications. PMID:26077357

  14. [Study on large-scale regional laser detection methods for water vapor concentration].

    PubMed

    He, Ying; Zhang, Yu-Jun; Wang, Li-Ming; You, Kun; Zhou, Yi; Sun, Xiao-Min; Liu, Zhen-Min

    2013-03-01

    Water vapor is an important meteorological parameter in the atmosphere, TDLAS direct absorption technology combined with open-path monitoring was used in order to achieve large-scale regional atmospheric water vapor concentration detection with high sensitivity, high accuracy and fast response, and to correct the remote sensing data. The large-scale regional laser detection system for water vapor was designed and the absorption line of water vapor molecules near 1.27 microm was chosen as the goal line. The system performance was verified in conjunction with a multiple reflection cell, that the system limit sensitivity was 14.803 mmol.mol-1 in optical path of 40 m. The continuous field experiment in 1,420 m optical path at the Yucheng Integrated Experimental Station, CAS was completed with this system which worked stably. Then the measured data was compared with the data of a gas analyzer LI-7500 in eddy correlation observation system at the same site, and the data consistency was good. A new method for water vapor concentration monitoring in the complex field of non-uniform underlying surface was provided. PMID:23705417

  15. Scan mirrors relay for high resolution laser scanning systems

    NASA Astrophysics Data System (ADS)

    Kessler, David

    2014-09-01

    Two dimensional beam deflection is often required in medical laser scanning systems such as OCT or confocal microscopy. Commonly two linear galvo mirrors are used for performance in terms of their large apertures and scan angles. The galvo mirrors are placed at the vicinity of entrance pupil of the scan lens with a "displacement distance" separating them. This distance limits the scan fields and/or reduces the effective aperture of the scan lens. Another option is to use a beam or pupil relay, and image one galvo mirror onto the other. However, beam (or pupil) relays are notoriously complicated, expensive and can add significant aberrations. This paper discusses a simple, all reflective, diffraction limited, color corrected, beam relay, capable of large scan angles and large deflecting mirrors. The design is based on a unique combination of an Offner configuration with a Schmidt aspheric corrector. The design is highly corrected up to large scan mirrors and large scan angles down to milliwaves of aberrations. It allows significantly larger scan field and or scan lenses with higher numerical aperture as compared with scanners using galvos separated by the displacement distance. While this relay is of exceptionally high performance, it has one element located where the beam is focused which may present a problem for high power lasers. Thus modifications of the above design are introduced where the beam is focused in mid air thus making it usable for high power systems such including laser marking and fabrication systems.

  16. Two-wavelength scanning spot interferometer using single-frequency diode lasers.

    PubMed

    Boef, A J

    1988-01-15

    A two-wavelength interferometer is described that can be used to measure distances to rough surfaces with micrometer resolution. The measuring range can be made as large as several centimeters. Owing to the small numerical aperture of the object beam, the interferometer is particularly suitable in applications where a long working distance is required. The interferometer uses two single-frequency diode lasers to create a virtual two-wavelength laser. The equivalent wavelength of this laser can be easily tuned by changing the temperature of the laser diodes in opposite directions. PMID:20523591

  17. Massively parallel synthetic-aperture radar autofocus

    NASA Astrophysics Data System (ADS)

    Mastin, Gary A.; Plimpton, Steven J.; Ghiglia, Dennis C.

    1991-12-01

    The iterative phase gradient autofocus (PGA) algorithm for automatically focusing synthetic aperture radar images has been implemented on both a 16384-processor Connection Machine and the 1024-processor nCUBE 2 hypercube. Massive parallelism has proven its value by dramatically reducing processing times over those achieved on sequential machines by an order of magnitude or more. This is especially important for very large images or where high volumes of input and output are encountered. We provide an overview of the PGA algorithm, highlighting opportunities for significant speed-up in parallel architectures. This is followed by implementation details and timing results.

  18. Stochastic Analysis of Precipitation/Dissolution and Aperture Alteration in Variable Aperture Fractures Under Gradient-Reaction Conditions

    NASA Astrophysics Data System (ADS)

    Chaudhuri, A.; Rajaram, H.

    2007-12-01

    Precipitation and Dissolution reactions within fractures alter fracture apertures, which in turn affects their flow and transport properties. Different types of aperture alteration patterns occur in different flow and reaction regimes. One class of regimes encountered in geological systems is the "gradient reaction" regime, where fluids are essentially in chemical equilibrium with a mineral everywhere, but precipitation-dissolution reactions are driven by solubility gradients that result from variations in temperature or salinity. In many such cases, the solubility gradient is invariant over very long periods of time, and largely unaffected by medium alteration. For instance in a sparsely fractured rock mass, heat transfer is largely conduction-dominated, due to the large heat capacity of the rock, and not significantly modified by fluid flow or the feedback between aperture alteration and fluid flow. Similar behavior has also been postulated during the emplacement of ocean-bed methane hydrates. We present a stochastic analysis to develop equations for the evolution of the mean aperture, aperture variance, spectrum/covariance and effective transmissivity under gradient-reaction conditions. The stochastic analysis consistently predicts (i) a runaway growth of transmissivity in the case of dissolution and (ii) a much slower rate of transmissivity decrease in a variable-aperture fracture than in a parallel-plate fracture. In the case of dissolution, an increase in initial aperture variance leads to a faster rate of transmissivity growth, while in the case of precipitation it leads to a slower rate of transmissivity reduction. Dissolution leads to an enhancement of anisotropy in the aperture correlation structure, with more persistent correlation in the direction of flow. The behavior is opposite in the case of precipitation. The predictions of the stochastic analysis are verified based on high-resolution Monte-Carlo simulations in computer-generated random initial aperture fields. We discuss potential applications of our results to natural and engineered geological processes incuding hypogene karstification, methane hydrates and geothermal systems. We also present preliminary results from ongoing work evaluating the role of convective heat transfer and hydromechanical coupling on aperture alteration in a gradient reaction regime

  19. Parameters affecting the power distribution in the radio frequency discharge of large-area diffusion-cooled CO2 lasers

    Microsoft Academic Search

    A. Lapucci; S. Mascalchi; R. Ringressi

    1998-01-01

    An efficient power extraction from radio frequency (RF) excited CO 2 lasers can only be obtained by means of a uniform discharge power distribution. This distribution is mainly determined by the line-effect produced by the discharge structure. In this paper we report on a set of measurements performed on the luminosity of a large-area discharge showing the role played by

  20. Computational Investigation of Dipole Traps Formed by the Projection of Diffraction Patterns from a Circular Aperture

    NASA Astrophysics Data System (ADS)

    Gillen, Glen D.; Gillen-Christandl, Katharina

    2011-05-01

    Previously we have shown that laser light incident upon a circular diffracting aperture produces intensity distributions suitable for either red-detuned (RDT) or blue-detuned (BDT) optical dipole traps for cold neutral atoms. Typically, the calculated traps are located within a millimeter of the diffracting aperture, which requires the aperture to be located inside of the vacuum chamber. Using a combination of scalar diffraction theory and beam propagation techniques, a mathematical model has been developed to project the diffraction pattern away from the aperture. Projected intensity distributions allow for the diffracting aperture and optics to be located outside of the vacuum chamber. We will present calculations which show that the properties of the RDT and BDT sites are not only maintained through the projection, but also can be manipulated using a simple single-lens optical system. Work supported by the NSF Grant No. PHY-0855524.

  1. Laboratory demonstrations of interferometric and spotlight synthetic aperture ladar techniques.

    PubMed

    Crouch, Stephen; Barber, Zeb W

    2012-10-22

    A variety of synthetic-aperture ladar (SAL) imaging techniques are investigated on a table-top laboratory setup using an ultra-broad bandwidth (>3 THz) actively linearized chirp laser centered at 1.55 microns. Stripmap and spotlight mode demonstrations of SAL in monstatic and bistatic geometries are presented. Interferometric SAL for 3D topographical relief imaging is demonstrated highlighting the coherent properties of the SAL imaging technique. PMID:23187186

  2. Large-core tube-leaky waveguide for delivery of high-powered Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Kobayashi, S.; Katagiri, T.; Matsuura, Y.

    2014-02-01

    A tube-leaky fiber that consists of only dielectric thin-film tubing for delivery of Er:YAG laser light is presented. The tube-leaky fiber confines light in the airy core when the film thickness is properly chosen for target wavelength. Transmission properties of the fibers are derived by using a ray optic method and designed the optimum wall thickness for the Er:YAG laser wavelength of 2.94 micron. In fabrication of the tube leaky fiber, we use a microstructural tube made of glass to enhance mechanical strength. The central bore and surrounding glass thin layer that is held by the microstructure function as a tube-leaky fiber. We fabricate a large-core fiber for delivery of high-power medical lasers by stack-and-draw method and we use borosilicate-glass as a fiber material for low cost fabrication. Fabricated fibers have a diameter over 400 ?m and from the loss measurements for Er:YAG laser, and the fibers deliver laser light with a transmission loss of 0.85 dB/m that is comparable to 0.7 dB/m of conventional hollow-optical fibers. The fibers withstand transmission of laser pulses with energy higher than 120 mJ. We confirm that these energies are enough to ablate biological tissues in surgical operations.

  3. Metamaterial Apertures for Computational Imaging

    NASA Astrophysics Data System (ADS)

    Hunt, John; Driscoll, Tom; Mrozack, Alex; Lipworth, Guy; Reynolds, Matthew; Brady, David; Smith, David R.

    2013-01-01

    By leveraging metamaterials and compressive imaging, a low-profile aperture capable of microwave imaging without lenses, moving parts, or phase shifters is demonstrated. This designer aperture allows image compression to be performed on the physical hardware layer rather than in the postprocessing stage, thus averting the detector, storage, and transmission costs associated with full diffraction-limited sampling of a scene. A guided-wave metamaterial aperture is used to perform compressive image reconstruction at 10 frames per second of two-dimensional (range and angle) sparse still and video scenes at K-band (18 to 26 gigahertz) frequencies, using frequency diversity to avoid mechanical scanning. Image acquisition is accomplished with a 40:1 compression ratio.

  4. Aperture impedance of flared horns

    NASA Technical Reports Server (NTRS)

    Silvestro, J. W.; Collin, R. E.

    1989-01-01

    The method of moments is often used when solving for the mutual coupling in arrays of aperture antennas. For elements that are waveguides or gradually flared horns the aperture fields can be approximated by a finite sum of waveguide modal functions. To solve for the flared horn case an approximation for the aperture impedances of the modes in the horn is needed. The WKB approach can be used to find these impedances, but this technique has an important limitation. It is known to fail in the vicinity of its turning points. The turning point is the cutoff point of the mode being considered. To overcome this limitation a different technique, the spherical mode approach, is discussed. This approach has no cutoff problems and works well for conical and pyramidal horns. Comparisons between the impedances and the resulting dominant mode reflection coefficient found using the two techniques are presented to illustrate this point.

  5. Rapid adaptive optical recovery of optimal resolution over large volumes.

    PubMed

    Wang, Kai; Milkie, Daniel E; Saxena, Ankur; Engerer, Peter; Misgeld, Thomas; Bronner, Marianne E; Mumm, Jeff; Betzig, Eric

    2014-06-01

    Using a descanned, laser-induced guide star and direct wavefront sensing, we demonstrate adaptive correction of complex optical aberrations at high numerical aperture (NA) and a 14-ms update rate. This correction permits us to compensate for the rapid spatial variation in aberration often encountered in biological specimens and to recover diffraction-limited imaging over large volumes (>240 mm per side). We applied this to image fine neuronal processes and subcellular dynamics within the zebrafish brain. PMID:24727653

  6. Note: Computer controlled rotation mount for large diameter optics

    NASA Astrophysics Data System (ADS)

    Rakonjac, Ana; Roberts, Kris O.; Deb, Amita B.; Kjærgaard, Niels

    2013-02-01

    We describe the construction of a motorized optical rotation mount with a 40 mm clear aperture. The device is used to remotely control the power of large diameter laser beams for a magneto-optical trap. A piezo-electric ultrasonic motor on a printed circuit board provides rotation with a precision better than 0.03° and allows for a very compact design. The rotation unit is controlled from a computer via serial communication, making integration into most software control platforms straightforward.

  7. Development of the Synthetic Aperture Radiometer ESTAR and the Next Generation

    NASA Technical Reports Server (NTRS)

    LeVine, David M.; Haken, Michael; Swift, Calvin T.

    2004-01-01

    ESTAR is a research instrument built to develop the technology of aperture synthesis for passive remote sensing of Earth from space. Aperture synthesis is an interferometric technology that addresses the problem of putting large antenna apertures in space to achieve the spatial resolution needed for remote sensing at long wavelengths ESTAR was a first step (synthesis only across track and only at horizontal polarization). The development has progressed to a new generation instrument that is dual polarized and does aperture synthesis in two dimensions. Among the plans for the future is technology to combine active and passive remote sensing.

  8. Plasmonic nanofocusing with a metallic pyramid and an integrated C-shaped aperture

    PubMed Central

    Lindquist, Nathan C.; Johnson, Timothy W.; Nagpal, Prashant; Norris, David J.; Oh, Sang-Hyun

    2013-01-01

    We demonstrate the design, fabrication and characterization of a near-field plasmonic nanofocusing probe with a hybrid tip-plus-aperture design. By combining template stripping with focused ion beam lithography, a variety of aperture-based near-field probes can be fabricated with high optical performance. In particular, the combination of large transmission through a C-shaped aperture aligned to the sharp apex (<10?nm radius) of a template-stripped metallic pyramid allows the efficient delivery of light—via the C-shaped aperture—while providing a nanometric hotspot determined by the sharpness of the tip itself. PMID:23676841

  9. Elliptical Bessel-like diffraction pattern produced by circular apertures with different radius

    NASA Astrophysics Data System (ADS)

    Andrés-Zárate, Esteban; Angulo-Córdova, Quintiliano; Hernández-Nolasco, J. Adán.; Gutiérrez-Tepach, Gerardo; Treviño-Palacios, Carlos Gerardo

    2013-11-01

    We present the results of the amplitude diffraction pattern produced by two circular apertures. It was found that on the Fraunhofer plane there are is a diffraction pattern with an elliptical geometry with a Bessel-like spatial distribution modulated by Young fringes. The model was experimentally confirmed using circular apertures illuminated with a Helium-Neon laser and propagating to either the divergent Fresnel zone and the Fraunhofer plane using an achromatic cemented doublet as transforming lens.

  10. High-quality, large-area monolayer graphene for efficient bulk laser mode-locking near 1.25 ?m.

    PubMed

    Cho, Won Bae; Kim, Jun Wan; Lee, Hwang Woon; Bae, Sukang; Hong, Byung Hee; Choi, Sun Young; Baek, In Hyung; Kim, Kihong; Yeom, Dong-Il; Rotermund, Fabian

    2011-10-15

    High-quality monolayer graphene as large as 1.2×1.2?cm2 was synthesized by chemical vapor deposition and used as a transmitting saturable absorber for efficient passive mode-locking of a femtosecond bulk solid-state laser. The monolayer graphene mode-locked Cr:forsterite laser was tunable around 1.25??m and delivered sub-100?fs pulses with output powers up to 230?mW. The nonlinear optical characteristics of the monolayer graphene saturable absorber and the mode-locked operation were then compared with the case of the bilayer graphene saturable absorber. PMID:22002395

  11. A Newly Developed Large Diameter Diaphragmless Shock Tube for Studies on CO2-N2 Gas-Dynamic Laser

    NASA Astrophysics Data System (ADS)

    Rêgo, Israel Da Silveira; Sato, Kohnosuke; Miyoshi, Yoriaki; Ando, Taketora; Goto, Kentaro; Sakamoto, Mizuki; Kawasaki, Shoji; TRIAM Exp. Group

    A large diameter diaphragmless shock tube has been recently developed and designed to perform detailed studies of CO2-N2 gas-dynamic laser (GDL). This large diameter diaphragmless shock tube offers various advantages over the conventional shock tubes (diaphragm-type) as longer test times, higher degree of reproducibility of shock-tube data, and especially low-impurity operation condition. The latter advantage is experimentally demonstrated herein, which is very critical issue in the CO2-N2 GDL studies. A supersonic nozzle section was mounted at the end wall of the shock tube and instrumented for simultaneous measurement of laser output power and energy. The GDL action in a CO2-N2 mixture under low impurity condition has been obtained by using the large diameter diaphragmless shock tube for the first time.

  12. Large-area imager of hydrogen leaks in fuel cells using laser-induced breakdown spectroscopy

    Microsoft Academic Search

    M. Hori; R. S. Hayano; M. Fukuta; T. Koyama; H. Nobusue; J. Tanaka

    2009-01-01

    We constructed a simple device, which utilized laser-induced breakdown spectroscopy to image H2 gas leaking from the surfaces of hydrogen fuel cells to ambient air. Nanosecond laser pulses of wavelength lambda=532 nm emitted from a neodymium-doped yttrium aluminum garnet laser were first compressed to a pulse length Deltat<1 ns using a stimulated Brillouin backscattering cell. Relay-imaging optics then focused this

  13. Measurements of near forward scattered laser light in a large inertial confinement fusion plasma (invited)

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; MacGowan, B. J.; Glenzer, S. H.; Kirkwood, R. K.; Kruer, W. L.; Pollaine, S. M.; Williams, E. A.; Stone, G. F.; Afeyan, B. B.; Schmitt, A. J.

    1999-01-01

    We describe an instrument which measures the angular spread and spectrum of near forward scattered laser light from a probe beam in a long scalelength laser plasma. The instrument consists of a combination of time integrating and time resolving detectors which measure the scattered light amplitude over four orders of magnitude for a range of angles. These measurements allow us to study the beam spray resulting from various laser and plasma conditions and determine the density fluctuations associated with this beam spray.

  14. Large odd-even staggering in the very light platinum isotopes from laser spectroscopy

    SciTech Connect

    Le Blanc, F.; Obert, J.; Oms, J.; Putaux, J. C.; Roussiere, B.; Sauvage, J. [Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay Cedex (France); Pinard, J.; Cabaret, L.; Duong, H. T. [Laboratoire Aime Cotton, 91405 Orsay Cedex (France); Crawford, J. E.; Lee, J. K. P. [Foster Radiation Laboratory, Mc Gill University, H3A2T8 Montreal (Canada); Genevey, J. [Institut des Sciences Nuceaires, IN2P3-CNRS, 38026 Grenoble Cedex (France); Girod, M.; Peru, S. [C.E.A, Service de Physique Nucleaire, BP 12, 91680 Bruyeres-le-Chatel (France); Huber, G.; Krieg, M.; Sebastian, V. [Institut fuer Physik der Universitaet Mainz, 55099 Mainz (Germany); Lettry, J. [CERN, 1211 Geneve 23 (Switzerland); Lunney, D. [C.S.N.S.M., IN2P3-CNRS, 91405 Orsay Cedex (France); Zemlyanoi, S. [Flerov Laboratory of Nuclear Reaction, JINR, Dubna 141980, Moscow Region (Russian Federation)

    1998-12-21

    Laser spectroscopy measurements have been carried out on very neutron-deficient platinum isotopes with the COMPLIS experimental set-up on line with the ISOLDE-Booster facility. For the first time, Hg {alpha}-decay was exploited to extend the very light platinum chain. Using the 5d{sup 9}6s {sup 3}D{sub 3}{yields}5d{sup 9}6p {sup 3}P{sub 2} optical transition, hyperfine spectra of {sup 182,181,180,179,178}Pt and {sup 183}Pt{sup m} were recorded for the first time. The variation of the mean square charge radius between these nuclei, the magnetic moments of the odd isotopes and the quadrupole moment of {sup 183}Pt{sup m} were thus measured. A large deformation change between {sup 183}Pt{sup g} and {sup 183}Pt{sup m}, an odd-even staggering of the charge radius and a deformation drop from A=179 are clearly observed. All these results are discussed and compared with microscopic theoretical predictions using Hartree-Fock-Bogolyubov calculations using the Gogny force.

  15. Lasers

    SciTech Connect

    Eberly, J.H.; Milonni, P.W.

    1988-01-01

    This book explains the operating principles and applications of lasers, including central background material. It incorporates many intuitive explanations and practical examples. Introduces basic principles, including the necessary classical and quantum physics, and provides discussions of specific lasers, laser resonators, and applications, including nonlinear optics.

  16. Spin-lasers: From threshold reduction to large-signal analysis

    SciTech Connect

    Lee, Jeongsu; Bearden, Sean; Wasner, Evan; Žuti?, Igor, E-mail: zigor@buffalo.edu [Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260 (United States)

    2014-07-28

    Lasers in which spin-polarized carriers are injected provide paths to different practical room temperature spintronic devices, not limited to magnetoresistive effects. Unlike the conventional understanding of spintronic devices, an optimal performance of such spin-lasers can arise for finite, not infinite, spin relaxation time. By considering spin-relaxation times of both electrons and holes, we elucidate advantages of spin-lasers over their conventional (spin-unpolarized) counterparts. In addition to the steady-state threshold reduction, spin-lasers can improve transient operation leading to shorter turn-on delay times, reduced ringing of emitted light, and an enhanced bandwidth.

  17. Short-length large-mode-area photonic crystal fiber laser operating at 978 nm

    NASA Astrophysics Data System (ADS)

    He, Jing; Wang, Ziwei; Wu, Wendi; Du, Songtao; Lou, Qihong; Zhou, Jun; Li, Xiaojun

    2013-05-01

    The laser performance of a short-length Yb-doped rod-type photonic crystal fiber (PCF) laser is studied experimentally both in the three-level scheme and quasi-four-level scheme in this contribution. In the free oscillation mode, the rod-type PCF laser produce 13.6 W output power on the quasi-four-level system with center wavelength of 1030 nm. The laser operating on the three-level system is obtained with the introduction of specialized feedback around the 976 nm radiation. Up to 7 W output power is generated with wavelength centered in 978 nm.

  18. The physics of megajoule, large-scale, and ultrafast short-scale laser plasmas

    SciTech Connect

    Campbell, E.M. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

    1992-11-01

    Recent advances in laser science and technology have opened new possibilities for the study of high energy density plasma physics. The advances include techniques to control the laser spatial and temporal coherence, and the development of laser architectures and optical materials that have led to the demonstration of compact, short pulse ([tau][le]10[sup [minus]12] sec) high brightness lasers, capable of irradiating plasmas with intensities [ge]10[sup 18] W/cm[sup 2]. Experiments with reduced laser coherence have shown a substantial decrease in laser-driven parametric instabilities and have extended the parameter range where inverse bremsstrahlung absorption is the dominant coupling process. Beam smoothing with short wavelength lasers should result in inverse bremsstrahlung dominated coupling in the irradiance parameter regimes of the millimeter scale-length plasmas envisioned for the megajoule class lasers for ignition and gain in inertial fusion. In addition new regimes of laser--plasma coupling will become experimentally accessible when plasmas are irradiated with [ital I][ge]10[sup 18] W/cm[sup 2]. Relativistic effects, extreme profile modification, and electrons heated to energies exceeding 1 MeV are several of the phenomena that are expected. Numerous applications in basic and applied plasma physics will result from these new capabilities.

  19. Effects of activity pattern on eye size and orbital aperture size in primates

    Microsoft Academic Search

    E. Christopher Kirk

    2006-01-01

    Among primates, nocturnal species exhibit relatively larger orbital apertures than diurnal species. Most researchers have considered this disparity in orbital aperture size to reflect differences in eye size, with nocturnal primates having relatively large eyes in order to maximize visual sensitivity. Presumed changes in eye size due to shifts in activity pattern are an integral part of theoretical explanations for

  20. High numerical aperture tabletop soft x-ray diffraction microscopy with 70-nm resolution

    PubMed Central

    Sandberg, Richard L.; Song, Changyong; Wachulak, Przemyslaw W.; Raymondson, Daisy A.; Paul, Ariel; Amirbekian, Bagrat; Lee, Edwin; Sakdinawat, Anne E.; La-O-Vorakiat, Chan; Marconi, Mario C.; Menoni, Carmen S.; Murnane, Margaret M.; Rocca, Jorge J.; Kapteyn, Henry C.; Miao, Jianwei

    2008-01-01

    Light microscopy has greatly advanced our understanding of nature. The achievable resolution, however, is limited by optical wavelengths to ?200 nm. By using imaging and labeling technologies, resolutions beyond the diffraction limit can be achieved for specialized specimens with techniques such as near-field scanning optical microscopy, stimulated emission depletion microscopy, and photoactivated localization microscopy. Here, we report a versatile soft x-ray diffraction microscope with 70- to 90-nm resolution by using two different tabletop coherent soft x-ray sources—a soft x-ray laser and a high-harmonic source. We also use field curvature correction that allows high numerical aperture imaging and near-diffraction-limited resolution of 1.5?. A tabletop soft x-ray diffraction microscope should find broad applications in biology, nanoscience, and materials science because of its simple optical design, high resolution, large depth of field, 3D imaging capability, scalability to shorter wavelengths, and ultrafast temporal resolution. PMID:18162534

  1. Fractal structure of large-scale variability of wind-driven waves according to laser-scanning data

    NASA Astrophysics Data System (ADS)

    Zosimov, V. V.; Naugol'nykh, K. A.

    1994-03-01

    Results are presented for experimental laser-scanning investigations of the statistical characteristics of wind-driven ocean waves. The method involves counting the number of specular points during scanning of the sea surface by a narrow laser beam on a moving ship. The data analyzed are the set of specular points recorded along a track traced out by the laser beam as a result of the motion of the ship and the scanning beam. A prominent feature is the large-scale variability of the number of specular points and the self-similar nature of the process over a rather wide range of spatial scales. A fractal analysis of the process shows a clear power-law interval in the spatial spectrum of the distribution of specular points.

  2. Fractal structure of large-scale variability of wind-driven waves according to laser-scanning data.

    PubMed

    Zosimov, V. V.; Naugol'nykh, K. A.

    1994-03-01

    Results are presented for experimental laser-scanning investigations of the statistical characteristics of wind-driven ocean waves. The method involves counting the number of specular points during scanning of the sea surface by a narrow laser beam on a moving ship. The data analyzed are the set of specular points recorded along a track traced out by the laser beam as a result of the motion of the ship and the scanning beam. A prominent feature is the large-scale variability of the number of specular points and the self-similar nature of the process over a rather wide range of spatial scales. A fractal analysis of the process shows a clear power-law interval in the spatial spectrum of the distribution of specular points. PMID:12780082

  3. Hard X-ray generation and plasma filament formation under interaction of femtosecond laser pulses with large molecular clusters

    NASA Astrophysics Data System (ADS)

    Gordienko, Vyacheslav M.; Dzhidzhoev, Murat S.; Zhvaniya, Irina A.; Platonenko, Viktor T.; Trubnikov, Dmitriy N.; Fedorov, Denis O.

    2013-03-01

    We have demonstrated that the efficiency of hard X-ray generation (with energy 2 - 4 keV) from the femtosecond laser excitation (intensity I ˜ 1016 W/cm2, pulse energy E ˜ 5 mJ) of large molecular clusters (SF6, CF3I) can reach ˜ 10-6 (with yield ˜ 109 photons/J). It was shown that at maximal X-ray yield, the plasma filament is essentially non-uniform and has a multifocal structure. It was observed that the amplitude of the central and trailing spectral components of the chirped laser pulse decreases after its interaction with the cluster target as a result of efficient laser energy absorption under self-focusing conditions.

  4. Sensitivity function analysis of gravitational wave detection with single-laser and large-momentum-transfer atomic sensors

    NASA Astrophysics Data System (ADS)

    Tang, Biao; Zhang, Bao-Cheng; Zhou, Lin; Wang, Jin; Zhan, Ming-Sheng

    2015-03-01

    Recently, a configuration using atomic interferometers (AIs) had been suggested for the detection of gravitational waves. A new AI with some additional laser pulses for implementing large momentum transfer was also put forward, in order to reduce the effect of shot noise and laser frequency noise. We use a sensitivity function to analyze all possible configurations of the new AI and to distinguish how many momenta are transferred in a specific configuration. By analyzing the new configuration, we further explore a detection scheme for gravitational waves, in particular, that ameliorates laser frequency noise. We find that the amelioration occurs in such a scheme, but novelly, in some cases, the frequency noise can be canceled completely by using a proper data processing method. Supported by the National Natural Science Foundation of China.

  5. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  6. Accurate measurement of large optical frequency differences with a mode-locked laser

    Microsoft Academic Search

    J. Reichert; R. Holzwarth; T. W. Hänsch

    1999-01-01

    We have used the comb of optical frequencies emitted by a mode-locked laser as a ruler to measure differences of as much as 20 THz between laser frequencies. This is to our knowledge the largest gap measured with a frequency comb, with high potential for further improvements. To check the accuracy of this approach we show that the modes are

  7. REVIEW ARTICLE Interferometric Synthetic Aperture Radar

    E-print Network

    Kansas, University of

    REVIEW ARTICLE Interferometric Synthetic Aperture Radar Christopher T. Allen Department of Electrical Engineering and Computer Science and Radar Systems and Remote Sensing Laboratory University of Kansas Abstract. This paper provides a brief review of interferometric synthetic aperture radar (In

  8. Fresnel diffraction of aperture with rough edge

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The Fresnel diffraction of an aperture with a rough edge is studied in this paper. Circular and elliptical apertures with sinusoidal and random edges are chosen as examples to investigate the influence of the aperture edge on the diffraction. The numerical calculation results indicate intuitively the variations of the transverse and longitude diffraction intensity distributions with the edge parameters of the aperture. The data files of aperture models are obtained through the numerical calculations, and the aperture samples are obtained with the help of a liquid crystal light modulator (LCLM). Thus, the practical experiments of the diffractions of apertures with rough edges are carried out. The measured results are consistent with the calculated ones. The approximate analytic expressions of the diffraction by the modified aperture are deduced on the basis of the Fresnel diffraction theory and the statistic optics, and the reasonable explanations for the influence of edge parameters on the diffraction are given through the theoretical analysis.

  9. Optical properties of plastically bent large-diameter sapphire fiber tips for laser tissue ablations

    NASA Astrophysics Data System (ADS)

    Tong, Limin

    2000-10-01

    Aiming to facilitate laser surgery applications, six 0.75mm- diameter 90mm-length sapphire fiber tips were plastically bent by means of CO2 lasers with bending radii from 1.7mm to 3.6mm and bending angles of 15-120 degree(s). The average bending loss caused by the bending process of the tips is about 0.03dB with the minimum loss less than 0.02dB, the damage thresholds of these tips are higher than 160MW/cm2 for Nd:YAG laser pulses at 1.06micrometers and 2MW/cm2 for CuBr laser pulses at 510.6nm. Satisfactory optical properties of these sapphire fiber tips show that they are promising for use in laser surgery applications such as tissue ablations. 16

  10. Phase locking and supermode selection in multicore photonic crystal fiber lasers with a large doped area.

    PubMed

    Michaille, L; Bennett, C R; Taylor, D M; Shepherd, T J; Broeng, J; Simonsen, H R; Petersson, A

    2005-07-01

    We report on the laser properties of multicore photonic crystal fiber lasers. A stable phase locking of six- and seven-core structures through evanescent coupling is observed. Effective supermode selection is obtained by using both diffraction losses and the Talbot effect. A pure in-phase supermode is obtained (1.1 times diffraction limited). The laser operating in this mode has a slope efficiency of 70% with up to 44 W of output power. The modal area of the in-phase supermode multicore fiber is 1150 microm2, which makes it, to our knowledge, the single-mode fiber laser with the largest mode field area. In-phase laser action is stable when the fiber is bent. PMID:16075532

  11. Image simulation of geometric targets for spaceborne synthetic aperture radar

    Microsoft Academic Search

    J. M. Nasr; D. Vidal-Madjar

    1991-01-01

    A technique of synthetic aperture radar (SAR) image simulation is proposed. The method is based upon embedding of simulated man-made targets in a real background taken among the scenes captured by a spaceborne SAR. Scenes observed at 30 and 3 cm wavelength are used and the target dimensions are large enough with respect to the wavelength in order to compute

  12. Simulation and Realization of a Focus Shifting Unit using a Tunable Lens for 3D Laser Material Processing

    NASA Astrophysics Data System (ADS)

    Eberle, G.; Chiron, V.; Wegener, K.

    3D laser microprocessing using current market available technologies reveals itself to be a cost intensive and complex undertaking which is mostly due to the control architecture and use of moving components. Recent market appearance of electronically tunable lenses exhibiting NIR transmission, large aperture, high damage threshold and fast response times are available for laser based applications. Hence, enabling usage in the field of laser microprocessing. This paper thus introduces the functional principle of electrically tunable lenses, setup arrangement for 3D laser microprocessing, computational simulation of system parameters and comparison with experimental results.

  13. Distributed synthetic apertures for digital holographic imaging

    Microsoft Academic Search

    Yue Gao; Da-Yong Wang; Hua-Kun Cui; Zhi-Wei Zhou; Yun-Xin Wang

    2011-01-01

    A key problem for the digital holography is to improve the resolution of digital holographic system. We present a system for long-range digital holographic imaging with improved resolution using synthetic aperture method. Imaging system is formed by three sub-apertures, and each sub-aperture receiver contains independently telescope lenses and a CCD device. Through every sub-aperture system, a hologram is obtained. Subsequently,

  14. Modern radioastronomical aperture synthesis systems (review)

    Microsoft Academic Search

    N. M. Tseytlin

    1984-01-01

    Although sequential aperture synthesis is based on an analogy to synthesis of antenna arrays it is not adequate for analysis of signals and radioluminance distributions which vary during movement of the antennas. Parallel aperture synthesis is performed by an interferometer with fixed antennas so that not only stationary processes but also transient ones can be simultaneously observed. The aperture synthesis

  15. Lunar Laser Ranging Experiment for Japanese SELENE-2 landing mission

    NASA Astrophysics Data System (ADS)

    Noda, H.; Kunimori, H.; Araki, H.; Fuse, T.; Hanada, H.; Katayama, M.; Otsubo, T.; Sasaki, S.; Tazawa, S.; Tsuruta, S.; Funazaki, K.; Taniguchi, H.; Murata, K.

    2012-04-01

    We present the development status of the Lunar Laser Ranging experiment proposed to Japanese SELENE-2 lunar landing mission. The Lunar Laser Ranging measures the distance between laser link stations on the Earth and retroreflectors on the Moon, by detecting the time of flight of photons of high-powered laser emitted from the ground station. Since the Earth-Moon distance contains information of lunar orbit, lunar solid tides, and lunar orientation and rotation, we can estimate the inner structure of the Moon through orientation, rotation and tide. Retroreflectors put by the Apollo and Luna missions in 1970's are arrays of many small Corner Cube Prisms (CCP). Because of the tilt of these arrays from the Earth direction due to the optical libration, the returned laser pulse is broaden, causing the main range error of more than 1.5 cm ([1]). Therefore retroreflectors with larger single aperture are necessary for more accurate ranging, and we propose a large single retroreflector of hollow-type with 15 cm aperture. Larger aperture up to 20 cm might be favorable if more mass is permitted for payloads. To cancel the velocity aberration, a large, single aperture retroreflector needs small amount of offset angle between the reflecting planes to spoil the return beam pattern. This angle offset, called Dihedral Angle Offset (DAO) must be optimized to be less than 1 second of arc with 0.1 seconds of arc accuracy to accumulate more photons [2, 3]. The realization of such small DAO is challenging with current technology, therefore the development of fabrication method is important. As for the mirror material, some ceramic products (ZPF: Zero-expansion Pore-free ceramics or SiC: silicon carbide) are under consideration in terms of weight, hardness and handling. The thermal quality of the material can be evaluated by both the thermal conductivity and the coefficient of thermal expansion. The method to fasten three planes each other with precise DAO must be developed.

  16. Large field double Kirkpatrick-Baez microscope with nonperiodic multilayers for laser plasma imaging

    NASA Astrophysics Data System (ADS)

    Bridou, F.; Mercier, R.; Raynal, A.; Clotaire, J. Y.; Colas, C.; Fournet, P.; Idir, M.; Soullié, G.; Remond, C.; Troussel, P.

    2002-11-01

    The double Kirkpatrick-Baez (DBA) microscope is derived from the grazing x-ray Kirkpatrick-Baez (KB) microscope. The KB is compound of two concave spherical mirrors working at grazing incidence and in an energy range about 100 eV-10 keV. The combination of two similar mirrors in the DKB increases the useful field. This device only requires spherical mirrors, more easy to manufacture (precision and roughness) than aspherical ones. In order to image a laser plasma source in a large field of view and within a bandpass of 0.6 keV around 3.4 keV, a KB optic covered with multilayers is developed. In fact, a compromise has to be found between the resolution of the optic (better with a less grazing angle), and the reflectivity (better with more grazing angle). We have chosen to keep the average grazing incidence on the four mirrors around 2°-3° just as for a first uncoated DKB made in our laboratory. This allows us to keep the same radius of curvature for the mirrors. At this energy multilayers are needed, due to the required reflectivity of better than 7% for each mirror. A difficulty appears concerning the energy and angular acceptance of multilayers. It is shown that a nonperiodic multilayer structure can be calculated to solve this problem, in spite of the absorption of the layers at the low energy of our application. The variation of periods is not continuous as in known classical supermirrors, and all the experimental parameters such as complex index of refraction and roughness have to be known. Thicknesses can then be optimized individually. The multilayers were deposited, tested, and the defects identified and corrected. Final experimental results of such stacks are given.

  17. Controlling the nonlinear intracavity dynamics of large He-Ne laser gyroscopes

    E-print Network

    Cuccato, Davide; Belfi, Jacopo; Beverini, Nicolò; Ortolan, Antonello; Di Virgilio, Angela

    2013-01-01

    A model based on Lamb's theory of gas lasers is applied to a He-Ne ring laser gyroscope in order to estimate and remove the laser dynamics contribution from the rotation measurements. The intensities of the counter-propagating laser beams exiting one cavity mirror are continuously observed together with a monitor of the laser population inversion. These observables, once properly calibrated with a dedicated procedure, allow us to estimate cold cavity and active medium parameters driving the main part of the nonlinearities of the system. The parameters identification and noise subtraction procedure has been verified by means of a Monte Carlo study of the system, and experimentally tested on the G-Pisa ring laser oriented with the normal to the ring plane almost parallel to the Earth rotation axis. In this configuration the Earth rotation-rate provides the maximum Sagnac effect while the contribution of the orientation error is reduced at minimum. After the subtraction of laser dynamics by a Kalman filter, the ...

  18. Vacuum isostatic micro/macro molding of PTFE materials for laser beam shaping in environmental applications: large scale UV laser water purification

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd; Ohar, Orest

    2009-08-01

    Accessibility to fresh clean water has determined the location and survival of civilizations throughout the ages [1]. The tangible economic value of water is demonstrated by industry's need for water in fields such as semiconductor, food and pharmaceutical manufacturing. Economic stability for all sectors of industry depends on access to reliable volumes of good quality water. As can be seen on television a nation's economy is seriously affected by water shortages through drought or mismanagement and as such those water resources must therefore be managed both for the public interest and the economic future. For over 50 years ultraviolet water purification has been the mainstay technology for water treatment, killing potential microbiological agents in water for leisure activities such as swimming pools to large scale waste water treatment facilities where the UV light photo-oxidizes various pollutants and contaminants. Well tailored to the task, UV provides a cost effective way to reduce the use of chemicals in sanitization and anti-biological applications. Predominantly based on low pressure Hg UV discharge lamps, the system is plagued with lifetime issues (~1 year normal operation), the last ten years has shown that the technology continues to advance and larger scale systems are turning to more advanced lamp designs and evaluating solidstate UV light sources and more powerful laser sources. One of the issues facing the treatment of water with UV lasers is an appropriate means of delivering laser light efficiently over larger volumes or cross sections of water. This paper examines the potential advantages of laser beam shaping components made from isostatically micro molding microstructured PTFE materials for integration into large scale water purification and sterilization systems, for both lamps and laser sources. Applying a unique patented fabrication method engineers can form micro and macro scale diffractive, holographic and faceted reflective structures into fused and semi-fused PTFE materials and compounds for use in UV Reactors. The materials unique attributes provide an unusual but effective hybrid element, by combining Lambertian diffusion and spectral reflective attributes. This paper will provide examples of the applications where this technology could be applied and typical constructions. An overview of UV sources commonly used in water treatment, including high power UV lasers and solid state UV light sources will be discussed. The paper will summarize how beam shaping elements produced in PTFE materials would provide further benefits to the emerging water disinfection or treatment market.

  19. Dynamic evolution of temporal dissipative-soliton molecules in large normal path-averaged dispersion fiber lasers

    SciTech Connect

    Liu Xueming [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119 (China)

    2010-12-15

    The robust dissipative soliton molecules (DSM's) exhibiting as the quasirectangular spectral profile are investigated numerically and observed experimentally in mode-locked fiber lasers with the large normal path-averaged dispersion and the large net cavity dispersion. These DSM's have an independently evolving phase with a pulse duration T{sub 0} of about 20 ps and a peak-to-peak separation of about 8T{sub 0}. Under laboratory conditions, the proposed laser delivers vibrating DSM's with an oscillating amplitude of less than a percent of peak separation. Numerical simulations show that DSM's are characterized by a spectral modulation pattern with about a 3-dB modulation depth measured as an averaged value. The experimental observations are in excellent agreement with the numerical predictions.

  20. Large Signal Circuit Model of Two-Section Gain Lever Quantum Dot Laser

    NASA Astrophysics Data System (ADS)

    Ashkan, Horri; Seyedeh Zahra, Mirmoeini; Rahim, Faez

    2012-11-01

    An equivalent circuit model for the design and analysis of two-section gain lever quantum dot (QD) laser is presented. This model is based on the three level rate equations with two independent carrier populations and a single longitudinal optical mode. By using the presented model, the effect of gain lever on QD laser performances is investigated. The results of simulation show that the main characteristics of laser such as threshold current, transient response, output power and modulation response are affected by differential gain ratios between the two-sections.

  1. Thickness determination of large-area films of yttria-stabilized zirconia produced by pulsed laser deposition

    Microsoft Academic Search

    N. Pryds; B. Toftmann; J. B. Bilde-Sørensen; J. Schou; S. Linderoth

    2006-01-01

    Films of yttria-stabilized zirconia (YSZ) on a polished silicon substrate of diameter up to 125mm have been produced in a large-area pulsed laser deposition (PLD) setup under typical PLD conditions. The film thickness over the full film area has been determined by energy-dispersive X-ray spectrometry in a scanning electron microscope (SEM) with use of a method similar to one described

  2. Large-angle electro-optic laser scanner on LiTaO3 fabricated by in situ monitoring of

    E-print Network

    Gopalan, Venkatraman

    Large-angle electro-optic laser scanner on LiTaO3 fabricated by in situ monitoring of ferroelectric LiTaO3 wafer that is capable of scanning 632.8-nm light by an unprecedented 14.88° angle such as LiNbO3 and LiTaO3 have several ad- vantages over mechanical and other systems including small device

  3. Self-channelling of relativistic laser pulses in large-scale underdense plasmas

    SciTech Connect

    Naseri, N.; Bochkarev, S. G.; Rozmus, W. [Department of Physics, University of Alberta, Edmonton, AB T6G 2G7 (Canada)

    2010-03-15

    Relativistic self-focusing and channelling of intense laser pulses have been studied in underdense plasma using two-dimensional particle-in-cell (PIC) simulations, for different laser powers and plasma densities. Analytical solutions for the stationary evacuated channels have been recovered in PIC simulations. It is shown that otherwise stable channels can accelerate electrons due to surface waves on the walls of the channels. Relativistic filaments with finite electron density are unstable to transverse modulations which lead in the nonlinear stage to the breakup of laser pulses into independent filaments. Different regimes of relativistic self-focusing and channelling, including electron heating, transverse instability, and break-up of the filaments, have been discussed and characterized using plasma density and laser power.

  4. Self-Channeling of Relativistic Laser Pulses in Large-Scale Underdense Plasmas

    E-print Network

    Naseri, N; Rozmus, W

    2009-01-01

    Relativistic self-focusing and channeling of intense laser pulses have been studied in underdense plasma using 2D PIC simulations, for different laser powers and plasma densities. Analytical solutions for the stationary evacuated channels have been recovered in PIC simulations. It is shown that otherwise stable channels can accelerate electrons due to surface waves on the walls of the channels. Relativistic filaments with finite electron density are unstable to transverse modulations which lead in the nonlinear stage to the break-up of laser pulses into independent filaments. Different regimes of relativistic self-focusing and channeling, including electron heating, transverse instability and break-up of the filaments have been discussed and characterized using plasma density and laser power.

  5. Effects of large laser bandwidth on stimulated Raman scattering instability in underdense plasma

    NASA Astrophysics Data System (ADS)

    Zhao, Yao; Yu, Lu-Le; Zheng, Jun; Weng, Su-Ming; Ren, Chuang; Liu, Chuan-Sheng; Sheng, Zheng-Ming

    2015-05-01

    The effects of laser bandwidth on stimulated Raman scattering (SRS) instability in underdense plasma are studied by particle-in-cell simulations. In the simulations, sinusoidal frequency modulation of the incident laser pulse is used. By changing the size of bandwidth, it is shown that the linear growth of SRS can be suppressed considerably, provided the laser bandwidth is much larger than the SRS linear growth rate. Simulations also show that by choosing the proper frequency modulation parameters or decreasing the linear growth rate of SRS, the inhibitory effects become more obvious. The plasma electron temperature tends to weaken the bandwidth effects especially when it is over a keV level. The laser bandwidth can only increase the time duration for linear growth but cannot diminish the instability completely.

  6. Large area fabrication of tuned polystyrene/poly(methylmethacrylate) periodic structures using laser interference patterning.

    PubMed

    Acevedo, Diego F; Lasagni, Andrés F; Cornejo, Marina; Politano, Meline; Barbero, Cesar; Mücklich, Frank

    2009-08-18

    The fabrication of advanced architectures in poly(methylmethacrylate-co-styrene) (PMMA-S) copolymers (ranging from 12 to 66% mol content of methylmethacrylate) using direct laser interference patterning is reported. For all copolymer compositions, two different regimes were observed. At low laser intensities, the irradiated surfaces swell up due to the formation of microbubbles that result from the degradation of the methylmetacrylate (MMA) component. While laser ablation produces concave holes, the swelling process permits fabrication of convex hemispherical dots. At higher intensities the bubbles release from the surface forming a periodic micropored structure. In addition, the laser fluence necessary to swell the polymeric surface (swelling threshold) does not depend on polymer composition, while the ablation threshold, which determines the transition to the periodic micropored structure, strongly depends on the MMA content. This observation can be explained by the mechanical and chemical properties of the copolymer. The method provides a unique way to produce periodical structures protruding from the polymer surface. PMID:19585964

  7. Fundamental Studies of Ignition Process in Large Natural Gas Engines Using Laser Spark Ignition

    Microsoft Academic Search

    Azer Yalin; Bryan Willson

    2008-01-01

    Past research has shown that laser ignition provides a potential means to reduce emissions and improve engine efficiency of gas-fired engines to meet longer-term DOE ARES (Advanced Reciprocating Engine Systems) targets. Despite the potential advantages of laser ignition, the technology is not seeing practical or commercial use. A major impediment in this regard has been the 'open-path' beam delivery used

  8. Development of a laser velocimeter for a large transonic wind tunnel

    Microsoft Academic Search

    J. P. Greissing; D. L. Whipple

    1982-01-01

    On a 8 x 6 Foot Supersonic Wind Tunnel a laser velocimeter was utilized in the testing of advanced high speed turbopropellers. The system, using a 15-W argon-ion laser, a 3-beam 2-axis transmitting-receiving optics package, a zoom lens with 1- to 4-m focal lengths, and a 0.4-m corner mirror was initially assembled and tested in the checkout room. During the

  9. Controlling the non-linear intracavity dynamics of large He-Ne laser gyroscopes

    NASA Astrophysics Data System (ADS)

    Cuccato, D.; Beghi, A.; Belfi, J.; Beverini, N.; Ortolan, A.; Di Virgilio, A.

    2014-02-01

    A model based on Lamb's theory of gas lasers is applied to a He-Ne ring laser (RL) gyroscope to estimate and remove the laser dynamics contribution from the rotation measurements. The intensities of the counter-propagating laser beams exiting one cavity mirror are continuously observed together with a monitor of the laser population inversion. These observables, once properly calibrated with a dedicated procedure, allow us to estimate cold cavity and active medium parameters driving the main part of the non-linearities of the system. The quantitative estimation of intrinsic non-reciprocal effects due to cavity and active medium non-linear coupling plays a key role in testing fundamental symmetries of space-time with RLs. The parameter identification and noise subtraction procedure has been verified by means of a Monte Carlo study of the system, and experimentally tested on the G-PISA RL oriented with the normal to the ring plane almost parallel to the Earth's rotation axis. In this configuration the Earth's rotation rate provides the maximum Sagnac effect while the contribution of the orientation error is reduced to a minimum. After the subtraction of laser dynamics by a Kalman filter, the relative systematic errors of G-PISA reduce from 50 to 5 parts in 103 and can be attributed to the residual uncertainties on geometrical scale factor and orientation of the ring.

  10. Sparse Aperture Masking on Paranal

    NASA Astrophysics Data System (ADS)

    Lacour, S.; Tuthill, P.; Ireland, M.; Amico, P.; Girard, J.

    2011-12-01

    The new operational mode of aperture-masking interferometry was added to the CONICA camera four years ago. Over the years, the masks - pieces of metal only two centimetres wide - have opened an unprecedented observational window for the NACO instrument. In comparison to the full aperture, they deliver superior point source function calibration, rejection of atmospheric noise and robust recovery of phase information through the use of closure phases. In the resolution range from about half to several resolution elements, masking interferometry sets the benchmark for the present state of the art worldwide in delivering high fidelity imaging and direct detection of faint companions. The technique and observational applications to imaging of circumstellar discs and exoplanets are outlined.

  11. Controlled-aperture wave-equation migration

    SciTech Connect

    Huang, L. (Lian-Jie); Fehler, Michael C.; Sun, H. (Hongchuan); Li, Z. (Zhiming)

    2003-01-01

    We present a controlled-aperture wave-equation migration method that no1 only can reduce migration artiracts due to limited recording aperlurcs and determine image weights to balance the efl'ects of limited-aperture illumination, but also can improve thc migration accuracy by reducing the slowness perturbations within thc controlled migration regions. The method consists of two steps: migration aperture scan and controlled-aperture migration. Migration apertures for a sparse distribution of shots arc determined using wave-equation migration, and those for the other shots are obtained by interpolation. During the final controlled-aperture niigration step, we can select a reference slowness in c;ontrollecl regions of the slowness model to reduce slowncss perturbations, and consequently increase the accuracy of wave-equation migration inel hods that makc use of reference slownesses. In addition, the computation in the space domain during wavefield downward continuation is needed to be conducted only within the controlled apertures and therefore, the computational cost of controlled-aperture migration step (without including migration aperture scan) is less than the corresponding uncontrolled-aperture migration. Finally, we can use the efficient split-step Fourier approach for migration-aperture scan, then use other, more accurate though more expensive, wave-equation migration methods to perform thc final controlled-apertio.ee migration to produce the most accurate image.

  12. Large Scale Laser Two-Photon Polymerization Structuring for Fabrication of Artificial Polymeric Scaffolds for Regenerative Medicine

    SciTech Connect

    Malinauskas, M.; Purlys, V.; Zukauskas, A.; Rutkauskas, M.; Danilevicius, P.; Paipulas, D.; Bickauskaite, G.; Gadonas, R.; Piskarskas, A. [Vilnius University, Physics Faculty, Department of Quantum Electronics, Laser Research Center, Sauletekio ave. 10, LT-10223 Vilnius (Lithuania); Bukelskis, L.; Baltriukiene, D.; Bukelskiene, V. [Institute of Biochemistry, Vivarium, Mokslininkuo str. 12, LT-08662 Vilnius (Lithuania); Sirmenis, R. [Vilnius University Hospital Santariskiuo Klinikos, Santariskiuo g. 2, LT-08661 Vilnius (Lithuania); Gaidukeviciute, A. [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Vassilika Vouton, 711 10 Heraklion, Crete (Greece); Sirvydis, V. [Vilnius University, Faculty of Medicine, Heart Surgery Center, Santariskiuo 2, LT-08661, Vilnius (Lithuania)

    2010-11-10

    We present a femtosecond Laser Two-Photon Polymerization (LTPP) system of large scale three-dimensional structuring for applications in tissue engineering. The direct laser writing system enables fabrication of artificial polymeric scaffolds over a large area (up to cm in lateral size) with sub-micrometer resolution which could find practical applications in biomedicine and surgery. Yb:KGW femtosecond laser oscillator (Pharos, Light Conversion. Co. Ltd.) is used as an irradiation source (75 fs, 515 nm (frequency doubled), 80 MHz). The sample is mounted on wide range linear motor driven stages having 10 nm sample positioning resolution (XY--ALS130-100, Z--ALS130-50, Aerotech, Inc.). These stages guarantee an overall travelling range of 100 mm into X and Y directions and 50 mm in Z direction and support the linear scanning speed up to 300 mm/s. By moving the sample three-dimensionally the position of laser focus in the photopolymer is changed and one is able to write complex 3D (three-dimensional) structures. An illumination system and CMOS camera enables online process monitoring. Control of all equipment is automated via custom made computer software ''3D-Poli'' specially designed for LTPP applications. Structures can be imported from computer aided design STereoLihography (stl) files or programmed directly. It can be used for rapid LTPP structuring in various photopolymers (SZ2080, AKRE19, PEG-DA-258) which are known to be suitable for bio-applications. Microstructured scaffolds can be produced on different substrates like glass, plastic and metal. In this paper, we present microfabricated polymeric scaffolds over a large area and growing of adult rabbit myogenic stem cells on them. Obtained results show the polymeric scaffolds to be applicable for cell growth practice. It exhibit potential to use it for artificial pericardium in the experimental model in the future.

  13. Hypersonic gasdynamic laser system

    SciTech Connect

    Foreman, K.M.; Maciulaitis, A.

    1990-05-22

    This patent describes a visible, or near to mid infra-red, hypersonic gas dynamic laser system. It comprises: a hypersonic vehicle for carrying the hypersonic gas dynamic laser system, and also providing high energy ram air for thermodynamic excitation and supply of the laser gas; a laser cavity defined within the hypersonic vehicle and having a laser cavity inlet for the laser cavity formed by an opening in the hypersonic vehicle, such that ram air directed through the laser cavity opening supports gas dynamic lasing operations at wavelengths less than 10.6{mu} meters in the laser cavity; and an optical train for collecting the laser radiation from the laser cavity and directing it as a substantially collimated laser beam to an output aperture defined by an opening in the hypersonic vehicle to allow the laser beam to be directed against a target.

  14. The development of a laser safety program for a large academic research institution using Texas A&M University as a model

    E-print Network

    Johnson, Douglas Allen

    1995-01-01

    This thesis presents a model for developing a laser safety program for a large academic research institution. It is based on the standards and requirements of the 1993 American National Standards Institute document Z136.1, The Safe Use of Lasers...

  15. Laser beam shaping techniques

    SciTech Connect

    DICKEY,FRED M.; WEICHMAN,LOUIS S.; SHAGAM,RICHARD N.

    2000-03-16

    Industrial, military, medical, and research and development applications of lasers frequently require a beam with a specified irradiance distribution in some plane. A common requirement is a laser profile that is uniform over some cross-section. Such applications include laser/material processing, laser material interaction studies, fiber injection systems, optical data image processing, lithography, medical applications, and military applications. Laser beam shaping techniques can be divided into three areas: apertured beams, field mappers, and multi-aperture beam integrators. An uncertainty relation exists for laser beam shaping that puts constraints on system design. In this paper the authors review the basics of laser beam shaping and present applications and limitations of various techniques.

  16. Prototype development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR

    NASA Technical Reports Server (NTRS)

    Tanner, A. B.; Wilson, W. J.; Kangaslahti, P. P.; Lambrigsten, B. H.; Dinardo, S. J.; Piepmeier, J. R.; Ruf, C. S.; Rogacki, S.; Gross, S. M.; Musko, S.

    2004-01-01

    Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 55 GHz will be presented. The laboratory prototype is being developed to demonstrate the technologies and system design needed to do millimeter-wave atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large thinned aperture Y-array on a geostationary satellite, and to use aperture synthesis to obtain images of the Earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system.

  17. Microscopic mechanisms of laser spallation and ablation of metal targets from large-scale molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Wu, Chengping; Zhigilei, Leonid V.

    2014-01-01

    The microscopic mechanisms of femtosecond laser ablation of an Al target are investigated in large-scale massively parallel atomistic simulations performed with a computational model combining classical molecular dynamics technique with a continuum description of the laser excitation and subsequent relaxation of conduction band electrons. The relatively large lateral size of the computational systems used in the simulations enables a detailed analysis of the evolution of multiple voids generated in a sub-surface region of the irradiated target in the spallation regime, when the material ejection is driven by the relaxation of laser-induced stresses. The nucleation, growth, and coalescence of voids take place within a broad (100 nm) region of the target, leading to the formation of a transient foamy structure of interconnected liquid regions and eventual separation (or spallation) of a thin liquid layer from the bulk of the target. The thickness of the spalled layer is decreasing from the maximum of 50 nm while the temperature and ejection velocity are increasing with increasing fluence. At a fluence of 2.5 times the spallation threshold, the top part of the target reaches the conditions for an explosive decomposition into vapor and small clusters/droplets, marking the transition to the phase explosion regime of laser ablation. This transition is signified by a change in the composition of the ablation plume from large liquid droplets to a mixture of vapor-phase atoms and clusters/droplets of different sizes. The clusters of different sizes are spatially segregated in the expanding ablation plume, where small/medium size clusters present in the middle of the plume are followed by slower (velocities of less than 3 km/s) large droplets consisting of more than 10,000 atoms. The similarity of some of the characteristics of laser ablation of Al targets (e.g., evolution of voids in the spallation regime and cluster size distributions in the phase explosion regime) to the ones observed in earlier simulations performed for different target materials points to the common mechanical and thermodynamic origins of the underlying processes.

  18. Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

    PubMed

    Macleod, Neil A; Molero, Francisco; Weidmann, Damien

    2015-01-26

    A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers. PMID:25835851

  19. The application and research of the multi-receiving telescopes technology in laser ranging to space targets

    NASA Astrophysics Data System (ADS)

    Wu, Zhibo; Zhang, Haifeng; Zhang, Zhongping; Deng, Huarong; Li, Pu; Meng, Wendong; Cheng, Zhien; Shen, Lurun; Tang, Zhenhong

    2014-11-01

    Laser ranging technology can directly measure the distance between space targets and ground stations with the highest measurement precision and will play an irreplaceable role in orbit check and calibrating microwave measurement system. The precise orbit determination and accurate catalogue of space targets can also be realized by laser ranging with multi-stations. Among space targets, most of ones are inactive targets and space debris, which should be paid the great attentions for the safety of active spacecrafts. Because of laser diffuse reflection from the surface of targets, laser ranging to space debris has the characteristics of wide coverage and weak strength of laser echoes, even though the powerful laser system is applied. In order to increase the receiving ability of laser echoes, the large aperture telescope should be adopted. As well known, some disadvantages for one set of large aperture telescope, technical development difficulty and system running and maintenance complexity, will limit its flexible applications. The multi-receiving telescopes technology in laser ranging to space targets is put forward to realize the equivalent receiving ability produced by one larger aperture telescope by way of using multi-receiving telescopes, with the advantages of flexibility and maintenance. The theoretical analysis of the feasibility and key technologies of multi-receiving telescopes technology in laser ranging to space targets are presented in this paper. The experimental measurement system based on the 60cm SLR system and 1.56m astronomical telescopes with a distance of about 50m is established to provide the platform for researching on the multi-receiving telescopes technology. The laser ranging experiments to satellites equipped with retro-reflectors are successfully performed by using the above experimental system and verify the technical feasibility to increase the ability of echo detection. And the multi-receiving telescopes technology will become a novel effective way to improve the detection ability of laser ranging to space debris.

  20. Perturbative analysis of coherent combining efficiency with mismatched lasers.

    PubMed

    Goodno, Gregory D; Shih, Chun-Ching; Rothenberg, Joshua E

    2010-11-22

    Coherent combining efficiency is examined analytically for large arrays of non-ideal lasers combined using filled aperture elements with nonuniform splitting ratios. Perturbative expressions are developed for efficiency loss from combiner splitting ratios, power imbalance, spatial misalignments, beam profile nonuniformities, pointing and wavefront errors, depolarization, and temporal dephasing of array elements. It is shown that coupling efficiency of arrays is driven by non-common spatial aberrations, and that common-path aberrations have no impact on coherent combining efficiency. We derive expressions for misalignment losses of Gaussian beams, providing tolerancing metrics for co-alignment and uniformity of arrays of single-mode fiber lasers. PMID:21164888

  1. Observation of Large-Angle Quasimonoenergetic Electrons from a Laser Wakefield

    SciTech Connect

    Kaganovich, D.; Gordon, D. F.; Ting, A. [Plasma Physics Division, Naval Research Laboratory, Washington, D.C. 20375 (United States)

    2008-05-30

    A relativistically intense laser pulse is focused into a helium jet and quasimonoenergetic electrons emitted at a 40 deg. angle with respect to the laser axis are observed. The average electron energy is between 1 and 2 MeV and the total accelerated charge is about 1 nC emitted in a 10 deg. cone angle. Three dimensional particle-in-cell simulations reproduce key features of the experimental results and show that the interaction between ionization heating and nonlinear cavitation wakefields is responsible for the acceleration.

  2. Large-area YBCO films with low-Rs prepared by excimer-laser-assisted MOD (ELAMOD) on sapphire substrates

    NASA Astrophysics Data System (ADS)

    Sohma, Mitsugu; Tsuchiya, Tetsuo; Yamaguchi, Iwao; Matsui, Hiroaki; Kumagai, Toshiya; Manabe, Takaaki; Terao, Katsuhiro; Kitada, Noritaka; Sato, Ryosuke; Nakamura, Tetsunari; Hirota, Noriaki; Ebisawa, Takashi; Ohtsu, Hidehiko

    2013-01-01

    High performance YBa2Cu3O7-y (YBCO) films with large area (50 mm-square) and 300 nm-thick were prepared by a combination of excimer-laser-assisted metalorganic deposition (ELAMOD) and conventional MOD using a fluorine-free coating solution. A characteristic feature in the ELAMOD process is that KrF excimer laser is irradiated on the solution-coated surface of specimen in an ambient atmosphere. The YBCO films on CeO2-buffered r-cut sapphire substrates showed low surface resistance (Rs), high superconducting current density (Jc), and good reproducibility in both Rs and Jc. The Rs and Jc values of the films were 0.6 m? (12 GHz) and around 2.0 MA/cm2 at 77.3 K, respectively.

  3. A laser-sheet flow visualization technique for the large wind tunnels of the National Full-Scale Aerodynamics Complex

    NASA Technical Reports Server (NTRS)

    Reinath, M. S.; Ross, J. C.

    1990-01-01

    A flow visualization technique for the large wind tunnels of the National Full Scale Aerodynamics Complex (NFAC) is described. The technique uses a laser sheet generated by the NFAC Long Range Laser Velocimeter (LRLV) to illuminate a smoke-like tracer in the flow. The LRLV optical system is modified slightly, and a scanned mirror is added to generate the sheet. These modifications are described, in addition to the results of an initial performance test conducted in the 80- by 120-Foot Wind Tunnel. During this test, flow visualization was performed in the wake region behind a truck as part of a vehicle drag reduction study. The problems encountered during the test are discussed, in addition to the recommended improvements needed to enhance the performance of the technique for future applications.

  4. Passively Q-switched Nd:YAG ceramic laser towards large pulse energy and short pulse width

    NASA Astrophysics Data System (ADS)

    Lan, R.; Wang, Z.; Liu, H.; Yu, H.; Guo, L.; Chen, L.; Zhuang, S.; Xu, X.; Wang, J.

    2010-01-01

    A large pulse energy and high peak power passively Q-switched ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG) laser has been demonstrated with Cr4+:YAG crystals as the saturable absorbers. By employing a continuous wave (CW) laser-diode (LD) as the pump source, as high as 11.3 W CW output power of 1064 nm was obtained under the pump power of 21.6 W, with an optical conversion efficiency of 52.3%. Inserting different initial transmissions Cr4+:YAG as saturable absorbers, under the incident pump power of 15.6 W, the largest pulse energy, shortest pulse width, and highest peak power are measured to be 188 µJ, 3.16 ns, and 59.5 kW, respectively. As we has known, this is the best passively Q-switched results ever reported by Nd:YAG ceramic material.

  5. Compact Fiber Laser for 589nm Laser Guide Star Generation

    NASA Astrophysics Data System (ADS)

    Pennington, D.; Drobshoff, D.; Mitchell, S.; Brown, A.

    Laser guide stars are crucial to the broad use of astronomical adaptive optics, because they facilitate access to a large fraction of possible locations on the sky. Lasers tuned to the 589 nm atomic sodium resonance can create an artificial beacon at altitudes of 95-105 km, thus coming close to reproducing the light path of starlight. The deployment of multiconjugate adaptive optics on large aperture telescopes world-wide will require the use of three to nine sodium laser guide stars in order to achieve uniform correction over the aperture with a high Strehl value. Current estimates place the minimum required laser power at > 10 W per laser for a continuous wave source, though a pulsed format, nominally 6?s in length at ~ 16.7 kHz, is currently preferred as it would enable tracking the laser through the Na layer to mitigate spot elongation. The lasers also need to be compact, efficient, robust and turnkey. We are developing an all-fiber laser system for generating a 589 nm source for laser-guided adaptive optics. Fiber lasers are more compact and insensitive to alignment than their bulk laser counterparts, and the heat-dissipation characteristics of fibers, coupled with the high efficiencies demonstrated and excellent spatial mode characteristics, make them a preferred candidate for many high power applications. Our design is based on sum-frequency mixing an Er/Yb:doped fiber laser operating at 1583 nm with a 938 nm Nd:silica fiber laser in a periodically poled crystal to generate 589 nm. We have demonstrated 14 W at 1583 nm with an Er/Yb:doped fiber laser, based on a Koheras single frequency fiber oscillator amplified in an IPG Photonics fiber amplifier. The Nd:silica fiber laser is a somewhat more novel device, since the Nd3+ ions must operate on the resonance transition (i.e. 4F3/2-4I9/2), while suppressing ASE losses at the more conventional 1088 nm transition. Optimization of the ratio of the fiber core and cladding permits operation of the laser at room temperature by minimizing the 1088 nm gain, along with induced bend loss. A 938 nm seed beam is provided by a 0.2 W diode laser, frequency broadened to 400 MHz by DC modulating the diode. This seeds a two stage double-clad, Nd:doped fiber amplifier, producing 16 W of 938 nm light with M2~ 1.05. Over 3.5 W at 589 nm in continuous wave (CW) format has been generated by sumfrequency mixing the two lasers in periodically poled potassium dihydrogen phosphate (PPKTP). To convert the system to a pulsed format, we added amplitude modulators after both the 1583 nm and 938 nm oscillators and a pre-amplifier in each line to restore the average power to the level prior to modulation. Frequency mixing is simplified by using a pulsed format as the higher peak power facilitates more efficient conversion. To date we have demonstrated 3.8 W at 589 nm in periodically poled stoichiometric lithium tantalate (PPSLT) using a 1 ?s pulse length and a 10% duty cycle. Additional bandwidth, pre-compensation for square pulse distortion (SPD) and polarization maintaining amplifier fiber is currently being implemented to enable scaling to higher output power and lower repetition rate. Details of these experiments, system design and performance will be presented.

  6. Large-Angle Electron Diffraction Structure in Laser-Induced Rescattering from Rare Gases

    SciTech Connect

    Ray, D.; Bocharova, I.; Maharjan, C.; Ranitovic, P.; Gramkow, B.; Magrakvelidze, M.; De, S.; Litvinyuk, I. V.; Le, A. T.; Lin, C. D.; Cocke, C. L. [J. R. Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506-2601 (United States); Ulrich, B. [Institut fuer Kernphysik, University Frankfurt, Max von Laue Str. 1, D-60438 Frankfurt (Germany); Morishita, T. [J. R. Macdonald Laboratory, Physics Department, Kansas State University, Manhattan, Kansas 66506-2601 (United States); Department of Applied Physics and Chemistry, The University of Electro-Communications, 1-5-1 Chofu-ga-oka, Chofu-shi, Tokyo 182-8585 (Japan) and PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012 (Japan); Paulus, G. G. [Institute of Optics and Quantum Electronics, 07743, Jena, Germany and Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States)

    2008-04-11

    We have measured full momentum images of electrons rescattered from Xe, Kr, and Ar following the liberation of the electrons from these atoms by short, intense laser pulses. At high momenta the spectra show angular structure (diffraction) which is very target dependent and in good agreement with calculated differential cross sections for the scattering of free electrons from the corresponding ionic cores.

  7. Large area avalanche photodiode detector array upgrade for a ruby-laser Thomson scattering system

    E-print Network

    Biewer, Theodore

    system have facilitated first-time measurements of the evolution of the electron temperature profile detectors. Over time, the system has evolved through minor and major technological upgrades, but the laser to pump the flashlamps and dissipate the excess heat. It can be operated in ``double pulse mode,'' however

  8. Large-area imager of hydrogen leaks in fuel cells using laser-induced breakdown spectroscopy.

    PubMed

    Hori, M; Hayano, R S; Fukuta, M; Koyama, T; Nobusue, H; Tanaka, J

    2009-10-01

    We constructed a simple device, which utilized laser-induced breakdown spectroscopy to image H2 gas leaking from the surfaces of hydrogen fuel cells to ambient air. Nanosecond laser pulses of wavelength lambda=532 nm emitted from a neodymium-doped yttrium aluminum garnet laser were first compressed to a pulse length Deltat<1 ns using a stimulated Brillouin backscattering cell. Relay-imaging optics then focused this beam onto the H(2) leak and initiated the breakdown plasma. The Balmer-alpha (H-alpha) emission that emerged from this was collected with a 2-m-long macrolens assembly with a 90-mm-diameter image area, which covered a solid angle of approximately 1 x 10(-3)pi steradians seen from the plasma. The H-alpha light was isolated by two 100-mm-diameter interference filters with a 2 nm bandpass, and imaged by a thermoelectrically cooled charge-coupled device camera. By scanning the position of the laser focus, the spatial distribution of H2 gas over a 90-mm-diameter area was photographed with a spatial resolution of < or = 5 mm. Photoionization of the water vapor in the air caused a strong H-alpha background. By using pure N2 as a buffer gas, H2 leaks with rates of <1 cc/min were imaged. We also studied the possibilities of detecting He, Ne, or Xe gas leaks. PMID:19895051

  9. Large Mode Area All-Solid Optical Fiber Lasers with Tailored Microstructured Cladding

    Microsoft Academic Search

    Ph. Roy; S. Février; L. Lavoute; D. Gaponov; R. Jamier; C. Lecaplain; G. Martel; A. Hideur; M. E. Likhachev; M. M. Bubnov; E. M. Dianov; M. Yu. Salganskii; V. F. Khopin; M. Yu. Yashkov; A. N. Guryanov; K. Schuster; J. Kobelke; S. Grimm

    2008-01-01

    Improvements, in terms of output power, spatial beam quality, bend insensitivity ... are still required in the field of single-mode fiber lasers. A major trend is to increase the active core area to increase the thresholds of nonlinear effects while ensuring a transverse single-mode behavior. Actually, increasing the active ions' concentration is also demanded since it allows a drastic reduction

  10. 4D Light Field Imaging System Using Programmable Aperture

    NASA Technical Reports Server (NTRS)

    Bae, Youngsam

    2012-01-01

    Complete depth information can be extracted from analyzing all angles of light rays emanated from a source. However, this angular information is lost in a typical 2D imaging system. In order to record this information, a standard stereo imaging system uses two cameras to obtain information from two view angles. Sometimes, more cameras are used to obtain information from more angles. However, a 4D light field imaging technique can achieve this multiple-camera effect through a single-lens camera. Two methods are available for this: one using a microlens array, and the other using a moving aperture. The moving-aperture method can obtain more complete stereo information. The existing literature suggests a modified liquid crystal panel [LC (liquid crystal) panel, similar to ones commonly used in the display industry] to achieve a moving aperture. However, LC panels cannot withstand harsh environments and are not qualified for spaceflight. In this regard, different hardware is proposed for the moving aperture. A digital micromirror device (DMD) will replace the liquid crystal. This will be qualified for harsh environments for the 4D light field imaging. This will enable an imager to record near-complete stereo information. The approach to building a proof-ofconcept is using existing, or slightly modified, off-the-shelf components. An SLR (single-lens reflex) lens system, which typically has a large aperture for fast imaging, will be modified. The lens system will be arranged so that DMD can be integrated. The shape of aperture will be programmed for single-viewpoint imaging, multiple-viewpoint imaging, and coded aperture imaging. The novelty lies in using a DMD instead of a LC panel to move the apertures for 4D light field imaging. The DMD uses reflecting mirrors, so any light transmission lost (which would be expected from the LC panel) will be minimal. Also, the MEMS-based DMD can withstand higher temperature and pressure fluctuation than a LC panel can. Robotics need near complete stereo images for their autonomous navigation, manipulation, and depth approximation. The imaging system can provide visual feedback

  11. Reconstruction of coded aperture images

    NASA Technical Reports Server (NTRS)

    Bielefeld, Michael J.; Yin, Lo I.

    1987-01-01

    Balanced correlation method and the Maximum Entropy Method (MEM) were implemented to reconstruct a laboratory X-ray source as imaged by a Uniformly Redundant Array (URA) system. Although the MEM method has advantages over the balanced correlation method, it is computationally time consuming because of the iterative nature of its solution. Massively Parallel Processing, with its parallel array structure is ideally suited for such computations. These preliminary results indicate that it is possible to use the MEM method in future coded-aperture experiments with the help of the MPP.

  12. Synthetic aperture interferometry: error analysis.

    PubMed

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt. 42, 701 (2003)]. A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt. 47, 1705 (2008)]. Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process. PMID:20648161

  13. High-contrast imaging with an arbitrary aperture: Active compensation of aperture discontinuities

    SciTech Connect

    Pueyo, Laurent; Norman, Colin, E-mail: lap@pha.jhu.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD (United States)

    2013-06-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential deformable mirrors (DMs) to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of DM surfaces that yield high-contrast point-spread functions is not linear, and nonlinear methods are needed to find the true minimum in the optimization topology. We solve the highly nonlinear Monge-Ampere equation that is the fundamental equation describing the physics of phase-induced amplitude modulation. We determine the optimum configuration for our two sequential DM system and show that high-throughput and high-contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to the James Webb Space Telescope, ACAD can attain at least 10{sup –7} in contrast and an order of magnitude higher for both the future extremely large telescopes and on-axis architectures reminiscent of the Hubble Space Telescope. We show that the converging nonlinear mappings resulting from our DM shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus, ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and struts while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the nonlinear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking, the ACAD technique can be used to significantly improve a broad class of telescope designs for a variety of problems.

  14. Aperture Efficiencies of Impulse Radiating Antennas

    Microsoft Academic Search

    C. Jerald Buchenauer; J. Scott Tyo; Jon S. H. Schoenberg

    A concept of aperture efficiency is introduced for the purpose of comparing and optimizing the performance of impulse radiating\\u000a antennas (IRAs). The aperture efficiencies of popular lens and reflector IRAs are computed as the ratios of peak radiated\\u000a power densities on boresight compared with that produced by anideal IRA with an aperture of equal area and equal total input\\u000a power.

  15. Status of the SG-III solid state laser project

    NASA Astrophysics Data System (ADS)

    Peng, Hansheng; Zhang, Xiao Min; Wei, XiaoFeng; Zheng, Wanguo; Jing, Feng; Sui, Zhan; Fan, Dianyuan; Lin, Zunqi

    1999-07-01

    High power solid state laser technologies for application to inertial confinement fusion have been developed over the past three decades in China. The XG-1 laser facility was built in 1984 and upgraded into XG-II in 1993. The SG-1 was completed in 1985 and the upgrade into SG-II will be finished in a few months. As the next step, the SG-III laser facility has been proposed to produce 60-kJ blue light for ICF target physics experiments and is one being conceptually designed. A preliminary baseline design suggest that he SG- III be a 64-beam facility with an output beam size of 25 cm X 25cm. The main amplifier column of 4 high by 2 wide has been chosen as a module. New laser technologies, including multipass amplification, large aperture plasma electrode switches, fast growth of KDP, laser glass with fewer platinum grains, Ce-doped quartz long flash lamps, capacitors with higher energy density, Ce-doped quartz long flash lamps, capacitors with higher energy density and precision manufacturing technique of large optical components have been developed to meet the requirements of the SG-III Project. In addition, numerical simulations are being conducted to optimize the optical design of the facility. The technical integration line with a 4 X 2 segmented aperture array of the amplifiers as a prototype beamline of the SG-III has been scheduled for the next few years.

  16. Large change in dielectric constant of CaCu3Ti4O12 under violet laser

    NASA Astrophysics Data System (ADS)

    Masingboon, C.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-03-01

    This work reports the influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals which exhibit giant dielectric constant. When the CCTO samples were exposed to 405-nm laser light, the enhancement in capacitance as high as 22% was observed for the first time, suggesting application of light-sensitive capacitance devices. To understand this change better microscopically, we also performed electronic-structure measurements using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. All these measurements suggest that this large change is driven by oxygen vacancy induced by the irradiation.

  17. Scaling of dissipative soliton fiber lasers to megawatt peak powers by use of large-area photonic crystal fiber.

    PubMed

    Lefrançois, Simon; Kieu, Khanh; Deng, Yujun; Kafka, James D; Wise, Frank W

    2010-05-15

    We report an all-normal dispersion femtosecond laser based on large-mode-area Yb-doped photonic crystal fiber. Self-starting mode-locked pulses are obtained with an average power of 12 W at 84 MHz repetition rate, corresponding to 140 nJ of chirped pulse energy. These are dechirped to a near transform-limited duration of 115 fs. Experimental results are consistent with numerical simulations of dissipative soliton intra-cavity pulse evolution, and demonstrate scaling of 100 fs pulses to megawatt peak powers. PMID:20479811

  18. Negative transconductance in apertured electron guns

    NASA Astrophysics Data System (ADS)

    Harris, John R.; O'Shea, Patrick G.

    2008-06-01

    Passing an electron beam through an aperture can serve to reduce the beam current or change the transverse beam profile. For a sufficiently intense beam, space charge will drive a radial expansion of the beam, which may cause the current passing through the aperture to decrease even though the current arriving at the aperture is increasing. When a gridded electron gun is used, this may be expressed by stating that the transconductance of the apertured gun is negative. Here, we explain this effect and explore some of the key factors governing when it can occur and influencing its strength.

  19. Negative Transconductance in Apertured Electron Guns

    SciTech Connect

    Harris, J R; O'Shea, P G

    2007-09-21

    Passing an electron beam through an aperture can serve to reduce the beam current or change the transverse beam profile. For a sufficiently intense beam, space charge will drive a radial expansion of the beam, which may cause the current passing through the aperture to increase even though the current arriving at the aperture is decreasing. When a gridded electron gun is used, this may be expressed by stating that the transconductance of the apertured gun is negative. Here we explain this effect, and explore some of the key factors governing when it can occur and influencing its strength.

  20. Ion mobility spectrometer with virtual aperture grid

    DOEpatents

    Pfeifer, Kent B. (Los Lunas, NM); Rumpf, Arthur N. (Albuquerque, NM)

    2010-11-23

    An ion mobility spectrometer does not require a physical aperture grid to prevent premature ion detector response. The last electrodes adjacent to the ion collector (typically the last four or five) have an electrode pitch that is less than the width of the ion swarm and each of the adjacent electrodes is connected to a source of free charge, thereby providing a virtual aperture grid at the end of the drift region that shields the ion collector from the mirror current of the approaching ion swarm. The virtual aperture grid is less complex in assembly and function and is less sensitive to vibrations than the physical aperture grid.

  1. Finite-aperture wire grid polarizers.

    PubMed

    Jensen, M A; Nordin, G P

    2000-12-01

    The transmission characteristics of wire grid polarizers fabricated in finite apertures are investigated by using a three-dimensional finite-difference time-domain formulation. Specifically, the optical transmissivity and extinction ratio are characterized for a wide variety of geometrical parameters including aperture size in both dimensions, conducting wire fill factor, and polarizer thickness. A dispersive material model is used to investigate the performance of polarizers fabricated by using realistic metals at infrared wavelengths. The results indicate that the aperture dimension significantly impacts the polarizer transmission behavior and that the extinction of the unwanted polarization is often limited by depolarizing scattering that is due to the finite aperture size. PMID:11140477

  2. Large-area nanoimprinting on various substrates by reconfigurable maskless laser direct writing

    NASA Astrophysics Data System (ADS)

    Lee, Daeho; Pan, Heng; Sherry, Alex; Ko, Seung Hwan; Lee, Ming-Tsang; Kim, Eunpa; Grigoropoulos, Costas P.

    2012-08-01

    Laser-assisted, one-step direct nanoimprinting of metal and semiconductor nanoparticles (NPs) was investigated to fabricate submicron structures including mesh, line, nanopillar and nanowire arrays. Master molds were fabricated with high-speed (200 mm s-1) laser direct writing (LDW) of negative or positive photoresists on Si wafers. The fabrication was completely free of lift-off or reactive ion etching processes. Polydimethylsiloxane (PDMS) stamps fabricated from master molds replicated nanoscale structures (down to 200 nm) with no or negligible residual layers on various substrates. The low temperature and pressure used for nanoimprinting enabled direct nanofabrication on flexible substrates. With the aid of high-speed LDW, wafer scale 4 inch direct nanoimprinting was demonstrated.

  3. GV /m Single-Cycle Terahertz Fields from a Laser-Driven Large-Size Partitioned Organic Crystal

    NASA Astrophysics Data System (ADS)

    Vicario, Carlo; Monoszlai, Balazs; Hauri, Christoph P.

    2014-05-01

    We report on compact and efficient laser-based THz generation in the terahertz frequency gap (1-10 THz). The radiation is generated by optical rectification of a midinfrared laser in a large-size, partitioned nonlinear organic crystal assembly. This enables up-scaling of presently field-limited tabletop THz sources to GV /m electric and several tesla magnetic field at millijoule pulse energy. In agreement with simulations, the THz beam properties at focus are shown to be not deteriorated by the discontinuity of the emitter surface. The high laser-to-THz energy conversion efficiency exceeds the Manley-Rowe limit and is explained by a cascaded ?(2) process in the organic crystals accompanied by a significant redshift of the pump spectrum. The scheme provides a compact, tabletop THz source for single-cycle transients at field strength equivalent or even higher to linear accelerator and FEL-based THz sources. This opens an avenue toward novel nonlinear THz applications.

  4. Can Stream Rating Curves be Modeled from Large-Scale, Low-Resolution Airborne Laser Scanning Data?

    NASA Astrophysics Data System (ADS)

    Lyon, S. W.; Nathanson, M.; Lam, N.; Dahlke, H. E.; Rutzinger, M.; Kean, J. W.; Laudon, H.

    2014-12-01

    This study explores the potential of using large-scale, low-resolution airborne laser scanning (ALS) derived elevation data to model stream rating curves. Rating curves, which allow the functional translation of stream water depth into discharge making them integral to water resource monitoring efforts, were modeled using a physics-based approach that captures basic geometric measurements to establish flow resistance due to implicit channel roughness. We tested synthetically thinned high-resolution airborne laser scanning data (topographic LiDAR data) as a proxy for low-resolution data at a point density equivalent to that obtained within most national-scale ALS strategies. Our results show that the errors incurred due to the effect of low-resolution versus high-resolution ALS data were less than those due to flow measurement and curve fitting uncertainties or uncertainty pertaining to vegetation densities. As such, although there still are some scale and technical limitations to consider, it appears theoretically possible to generate rating curves for any point in a river network from airborne laser scanning data of the resolution anticipated within national-scale ALS schemes. This would greatly enhance our ability to monitor streamflow globally by simplifying the effort required.

  5. Particle-in-Cell Simulations of Large-Area Electron Beam Diodes for KrF Laser Driven IFE

    NASA Astrophysics Data System (ADS)

    Swanekamp, S. B.; Friedman, M.; Smithe, D.; Ludeking, L.

    2001-10-01

    Large-area electron beam diodes are being developed to pump high-power krypton-fluoride (KrF) lasers that are suitable for inertial fusion energy. In a recent paper it was shown that the electron beam diode used on the Nike laser at NRL is susceptible to the transit time instability.(M. Friedman, S. Swanekamp, S. Obenschain, Y. Chan, L. Ludeking, and D. Smithe, Appl. Phys. Lett. 77), 2000 (1053). This instability introduces an energy spread on the electron beam as it leaves the diode. In this paper, we will show that experiments with the smaller diode used on the Electra laser are not affected by the transit time instability. We will show analysis and simulations that support these experimental observations that indicate growing waves are supported only when wave growth in the diode exceeds the losses out the ends of diode. We will further show that there is a critical diode length, L_crit, for which the diode in unstable when L > L_crit. We will also show that the growth rate is proportional to L?V/d^2 where L is the diode length, V is the voltage, and d is the anode-cathode gap spacing.

  6. Use of Zernike polynomials and interferometry in the optical design and assembly of large carbon-dioxide laser systems

    SciTech Connect

    Viswanathan, V.K.

    1981-01-01

    This paper describes the need for non-raytracing schemes in the optical design and analysis of large carbon-dioxide lasers like the Gigawatt, Gemini, and Helios lasers currently operational at Los Alamos, and the Antares laser fusion system under construction. The scheme currently used at Los Alamos involves characterizing the various optical components with a Zernike polynomial set obtained by the digitization of experimentally produced interferograms of the components. A Fast Fourier Transform code then propagates the complex amplitude and phase of the beam through the whole system and computes the optical parameters of interest. The analysis scheme is illustrated through examples of the Gigawatt, Gemini, and Helios systems. A possible way of using the Zernike polynomials in optical design problems of this type is discussed. Comparisons between the computed values and experimentally obtained results are made and it is concluded that this appears to be a valid approach. As this is a review article, some previously published results are also used where relevant.

  7. Large Area Parallel Surface Nanostructuring with Laser Irradiation Through Microlens Arrays

    Microsoft Academic Search

    C. S. Lim; M. H. Hong; Y. Lin; L. S. Tan; A. Senthil Kumar; M. Rahman

    2010-01-01

    In the past decade, the development of nanoelectronics and nano-optics has attracted much interest in surface nanostructuring of semiconductor materials. The irradiation of a microlens array by a laser beam generates many focused light spots, which can act as a direct writing tool on photo-polymer materials. This maskless surface nanostructuring technique enables thousands to millions of identical nano-features to be

  8. LARGE AREA PARALLEL SURFACE NANOSTRUCTURING WITH LASER IRRADIATION THROUGH MICROLENS ARRAYS

    Microsoft Academic Search

    C. S. LIM; M. H. HONG; Y. LIN; L. S. TAN; A. SENTHIL KUMAR; M. RAHMAN

    2010-01-01

    In the past decade, the development of nanoelectronics and nano-optics has attracted much interest in surface nanostructuring of semiconductor materials. The irradiation of a microlens array by a laser beam generates many focused light spots, which can act as a direct writing tool on photo-polymer materials. This maskless surface nanostructuring technique enables thousands to millions of identical nano-features to be

  9. Discharge impedance variations in large area radio frequency excited CO2 lasers

    NASA Astrophysics Data System (ADS)

    Lapucci, A.; Rossetti, F.; Mascalchi, S.; Ringressi, R.

    1997-10-01

    Some results from a systematic study on the impedance matching conditions and on the longitudinal power distributions in planar rf discharges for CO2 lasers, are given. They show that both plasma impedance and voltage distribution are different in cw and pulsed discharge modes revealing the importance of parameters such as the interelectrode temperature distribution and the local gas density and composition. These parameters have to be taken into account when designing matching networks and voltage smoothing schemes.

  10. 5cm aperture dipole studies

    SciTech Connect

    McInturff, A.D.; Bossert, R.; Carson, J.; Fisk, H.E.; Hanft, R.; Kuchnir, M.; Lundy, R.; Mantech, P.; Strait, J.

    1986-09-30

    The results obtained during the evolution of the design, construction, and testing program of the design ''B'' dipole are presented here. Design ''B'' is one of the original three competing designs for the Superconducting Super Collider ''SSC'' arc dipoles. The final design parameters were as follows: air cored (less than a few percent of the magnetic field derived from any iron present), aluminum collared, two layered winding, 5.5T maximum operating field, and a 5 cm cold aperture. There have been fourteen 64 cm long 5 cm aperture model dipoles cold tested (at 4.3K and less) in this program so far. There was a half length full size (6m) mechanical analog (M-10) built and tested to check the cryostat's mechanical design under ramping and quench conditions. Several deviations from the ''Tevatron'' dipole fabrication technique were incorporated, for example the use of aluminum collars instead of stainless steel. The winding technique variations explored were ''dry welding,'' a technique with the cable covered with Kapton insulation only and ''wet winding'' where the Kapton was covered with a light coat of ''B'' stage epoxy. Test data include quench currents, field quality (Fourier multipole co-efficients), coil magnetization, conductor current performance, and coil loading. Quench current, loss per cycle, and harmonics were measured as a function of the magnitude and rate of change of the magnetic field, and helium bath temperature.

  11. DAVINCI a Dilute Aperture Coronagraph

    NASA Astrophysics Data System (ADS)

    Shao, Michael

    2009-01-01

    The motivation for DAVINCI was originally to make use of the technology developed for space interferometers like SIM to build a coronagraph from four 1.1m telescopes that was dramatically lower in cost than a 4 5m filled aperture offaxis coronagraph. Our initial studies through team X have shown this cost savings to be real. But a more careful analysis showed that DAVINCI would have an inner working angle of 35mas a factor of 2 smaller than a 2 lambda/D 4 meter coronagraph or 70m external occulter, resulting in a 10X increase in the number of potential Earth-Clone targets. DAVINCI uses a nulling interferometer as a coronagraph, a nulling interferometer is one the few coronagraph architectures that are compatible with segmented and dilute aperture telescopes. Combined with a post coronagraph wavefront sensor several ultra-demanding tolerances of conventional coronagraphs can be relaxed by factors of 100. The post coronagraph wavefront sensor is also much less affected by local and exozodi background than wavefront sensors that use the science camera as the wavefront sensor. The post coronagraph interferometer is also used on ground based extreme AO coronagraphs, GPI, and P1640.

  12. Matrix shaped pulsed laser deposition: New approach to large area and homogeneous deposition

    NASA Astrophysics Data System (ADS)

    Akkan, C. K.; May, A.; Hammadeh, M.; Abdul-Khaliq, H.; Aktas, O. C.

    2014-05-01

    Pulsed laser deposition (PLD) is one of the well-established physical vapor deposition methods used for synthesis of ultra-thin layers. Especially PLD is suitable for the preparation of thin films of complex alloys and ceramics where the conservation of the stoichiometry is critical. Beside several advantages of PLD, inhomogeneity in thickness limits use of PLD in some applications. There are several approaches such as rotation of the substrate or scanning of the laser beam over the target to achieve homogenous layers. On the other hand movement and transition create further complexity in process parameters. Here we present a new approach which we call Matrix Shaped PLD to control the thickness and homogeneity of deposited layers precisely. This new approach is based on shaping of the incoming laser beam by a microlens array and a Fourier lens. The beam is split into much smaller multi-beam array over the target and this leads to a homogenous plasma formation. The uniform intensity distribution over the target yields a very uniform deposit on the substrate. This approach is used to deposit carbide and oxide thin films for biomedical applications. As a case study coating of a stent which has a complex geometry is presented briefly.

  13. Multidiagnostic analysis of ion dynamics in ultrafast laser ablation of metals over a large fluence range

    NASA Astrophysics Data System (ADS)

    Anoop, K. K.; Polek, M. P.; Bruzzese, R.; Amoruso, S.; Harilal, S. S.

    2015-02-01

    The dynamics of ions in ultrafast laser ablation of metals is studied over fluences ranging from the ablation threshold up to ?75 J/cm2 by means of three well-established diagnostic techniques. Langmuir probe, Faraday cup, and spectrally resolved intensified charge coupled device imaging simultaneously monitored the ions produced during ultrafast laser ablation of a pure copper target with 800 nm, ?50 fs, Ti: Sapphire laser pulses. The fluence dependence of ion yield is analyzed, resulting in the observance of three different regimes. The specific ion yield shows a maximum at about 4-5 J/cm2, followed by a gradual reduction and a transition to a high-fluence regime above ?50 J/cm2. The fluence dependence of the copper ions angular distribution is also analyzed, observing a gradual increase in forward-peaking of Cu ions for fluences up to ?10 J/cm2. A broader ion component is observed at larger angles for fluences larger than ?10 J/cm2. Finally, an experimental characterization of the ionic angular distribution for several metallic targets (Mg, Al, Cr, Fe, Cu, and W) is carried out at a relatively high fluence of ?66 J/cm2. Interestingly, the ion emission from the volatile metals shows a narrow, forward-peaked distribution, and a high peak ion yield compared to the refractory metals. Moreover, the width of ionic angular distributions presents a striking correlation with the peak ion yield.

  14. On the modeling of a large-scale electro-optic system

    Microsoft Academic Search

    Stephen J. Walsh

    1986-01-01

    Through this examination of a three-aperture bench laser experiment, a large-scale system realization model has been obtained. This realization model represents a valuable investigative tool for further control analysis and phased array experimental research. The experimental system was decomposed into five weakly coupled control loops that contained six components each. Transfer-function matrices for individual components were obtained through analysis of

  15. Rapid Adaptive Optical Recovery of Optimal Resolution over LargeVolumes

    PubMed Central

    Wang, Kai; Milkie, Dan; Saxena, Ankur; Engerer, Peter; Misgeld, Thomas; Bronner, Marianne E.; Mumm, Jeff; Betzig, Eric

    2014-01-01

    Using a de-scanned, laser-induced guide star and direct wavefront sensing, we demonstrate adaptive correction of complex optical aberrations at high numerical aperture and a 14 ms update rate. This permits us to compensate for the rapid spatial variation in aberration often encountered in biological specimens, and recover diffraction-limited imaging over large (> 240 ?m)3 volumes. We applied this to image fine neuronal processes and subcellular dynamics within the zebrafish brain. PMID:24727653

  16. Wide band dual circularly polarized aperture coupled microstrip patch antenna with bow tie shaped apertures

    Microsoft Academic Search

    A. K. Sharma; R. Singh; A. Mittal

    2004-01-01

    A wide band aperture coupled microstrip antenna with dual circular polarization operation is proposed. The antenna is designed and simulated to enable the transmission and reception of different circularly polarized wide band signals simultaneously with a single antenna. Instead of conventional rectangular apertures, two orthogonally placed bow-tie shaped apertures fed by a 3 dB branch line coupler are used to

  17. Adaptive Full Aperture Wavefront Sensor Study

    NASA Technical Reports Server (NTRS)

    Robinson, William G.

    1997-01-01

    This grant and the work described was in support of a Seven Segment Demonstrator (SSD) and review of wavefront sensing techniques proposed by the Government and Contractors for the Next Generation Space Telescope (NGST) Program. A team developed the SSD concept. For completeness, some of the information included in this report has also been included in the final report of a follow-on contract (H-27657D) entitled "Construction of Prototype Lightweight Mirrors". The original purpose of this GTRI study was to investigate how various wavefront sensing techniques might be most effectively employed with large (greater than 10 meter) aperture space based telescopes used for commercial and scientific purposes. However, due to changes in the scope of the work performed on this grant and in light of the initial studies completed for the NGST program, only a portion of this report addresses wavefront sensing techniques. The wavefront sensing techniques proposed by the Government and Contractors for the NGST were summarized in proposals and briefing materials developed by three study teams including NASA Goddard Space Flight Center, TRW, and Lockheed-Martin. In this report, GTRI reviews these approaches and makes recommendations concerning the approaches. The objectives of the SSD were to demonstrate functionality and performance of a seven segment prototype array of hexagonal mirrors and supporting electromechanical components which address design issues critical to space optics deployed in large space based telescopes for astronomy and for optics used in spaced based optical communications systems. The SSD was intended to demonstrate technologies which can support the following capabilities: Transportation in dense packaging to existing launcher payload envelopes, then deployable on orbit to form a space telescope with large aperture. Provide very large (greater than 10 meters) primary reflectors of low mass and cost. Demonstrate the capability to form a segmented primary or quaternary mirror into a quasi-continuous surface with individual subapertures phased so that near diffraction limited imaging in the visible wavelength region is achieved. Continuous compensation of optical wavefront due to perturbations caused by imperfections, natural disturbances, and equipment induced vibrations/deflections to provide near diffraction limited imaging performance in the visible wavelength region. Demonstrate the feasibility of fabricating such systems with reduced mass and cost compared to past approaches.

  18. New military uses for synthetic aperture radar (SAR)

    NASA Astrophysics Data System (ADS)

    Reamer, Richard E.; Stockton, Wayne; Stromfors, Richard D.

    1993-02-01

    Loral Defense Systems-Arizona, holder of the original patent for the invention of Synthetic Aperture Radar (SAR), developed SAR to meet the military's need for an all-weather, day/night sensor that could produce high quality reconnaissance imagery in adverse weather and restricted visibility conditions. These features, and the ability to image large areas with fine resolution in a relatively short period of time make this sensor useful for many military applications. To date, however, SARs for military use have been hampered by the fact that they've been large, complex, and expensive. Additionally, they have been mounted on special purpose, single mission aircraft which are costly to operate. That situation has changed. A small, modular SAR, called Miniature Synthetic Aperture Radar (MSAR) developed by Loral can be mounted with relative ease on Unmanned Aerial Vehicles (UAV) or on multi-mission aircraft such as the F-16, F/A-18, or on the F-14.

  19. Measuring and optimizing the momentum aperture in a particle accelerator.

    PubMed

    Steier, C; Robin, D; Nadolski, L; Decking, W; Wu, Y; Laskar, J

    2002-05-01

    Particle motion in storage rings is confined by various aperture limits, the size of which restricts the performance of the ring in terms of injection efficiency, lifetime, etc. Intrabeam scattering makes particles sweep a large portion of the phase space, where their motion may eventually be resonantly or chaotically excited to large amplitudes leading to collision with the vacuum chamber. We report here the studies performed at the Advanced Light Source (ALS) on the on- and off-momentum particle motion that provides a good understanding of these limitations. Using off-momentum simulations and experiments together with frequency map analysis, we could precisely correlate beam loss areas with resonance locations. The very good agreement between simulations and experiments allowed us to provide guidance for avoiding these dangerous areas. This analysis results in predictive improvements of the momentum aperture, which actually led to a lifetime increase of 25% at the ALS for very high bunch charge. PMID:12059724

  20. A Mechanically-Cooled, Highly-Portable, HPGe-Based, Coded-Aperture Gamma-Ray Imager

    SciTech Connect

    Ziock, Klaus-Peter [ORNL] [ORNL; Boehnen, Chris Bensing [ORNL] [ORNL; Hayward, Jason P [ORNL] [ORNL; Raffo-Caiado, Ana Claudia [ORNL] [ORNL

    2010-01-01

    Coded-aperture gamma-ray imaging is a mature technology that is capable of providing accurate and quantitative images of nuclear materials. Although it is potentially of high value to the safeguards and arms-control communities, it has yet to be fully embraced by those communities. One reason for this is the limited choice, high-cost, and low efficiency of commercial instruments; while instruments made by research organizations are frequently large and / or unsuitable for field work. In this paper we present the results of a project that mates the coded-aperture imaging approach with the latest in commercially-available, position-sensitive, High Purity Germanium (HPGe) detec-tors. The instrument replaces a laboratory prototype that, was unsuitable for other than demonstra-tions. The original instrument, and the cart on which it is mounted to provide mobility and pointing capabilities, has a footprint of ~ 2/3 m x 2 m, weighs ~ 100 Kg, and requires cryogen refills every few days. In contrast, the new instrument is tripod mounted, weighs of order 25 Kg, operates with a laptop computer, and is mechanically cooled. The instrument is being used in a program that is ex-ploring the use of combined radiation and laser scanner imaging. The former provides information on the presence, location, and type of nuclear materials while the latter provides design verification information. To align the gamma-ray images with the laser scanner data, the Ge imager is fitted and aligned to a visible-light stereo imaging unit. This unit generates a locus of 3D points that can be matched to the precise laser scanner data. With this approach, the two instruments can be used completely independently at a facility, and yet the data can be accurately overlaid based on the very structures that are being measured.