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Sample records for 850nm vertical cavity

  1. 850-nm Zn-diffusion vertical-cavity surface-emitting lasers with with oxide-relief structure for high-speed and energy-efficient optical interconnects from very-short to medium (2km) reaches

    NASA Astrophysics Data System (ADS)

    Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jason (Jyehong); Yang, Ying-Jay

    2015-03-01

    High-speed and "green" ~850 nm vertical-cavity surface-emitting lasers (VCSELs) have lately attracted lots of attention due to their suitability for applications in optical interconnects (OIs). To further enhance the speed and its maximum allowable linking distance of VCSELs are two major trends to meet the requirement of OI in next generation data centers. Recently, by use of the advanced 850 nm VCSEL technique, data rate as high as 64 Gbit/sec over 57m and 20 Gbit/sec over 2km MMF transmission have been demonstrated, respectively. Here, we will review our recent work about 850 nm Zn-diffusion VCSELs with oxide-relief apertures to further enhance the above-mentioned performances. By using Zn-diffusion, we can not only reduce the device resistance but also manipulate the number of optical modes to benefit transmission. Combing such device, which has excellent single-mode (SMSR >30 dB) and high-power (~7mW) performance, with advanced modulation format (OFDM), record-high bit-rate-distance-product through MMF (2.3 km×28 Gbit/sec) has been demonstrated. Furthermore, by selective etching away the oxide aperture inside Zn-diffusion VCSEL, significant enhancement of device speed, D-factor, and reliability can be observed. With such unique VCSEL structure, >40 Gbit/sec energy-efficient transmission over 100m MMF under extremely low-driving current density (<10kA/cm2) has been successfully demonstrated.

  2. 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. Kuzmenkov, A. G.; Maleev, N. A.; Blokhin, A. A.; Zadiranov, Yu. M.; Nikitina, E. V.; Ustinov, V. M.

    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 μm 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 μm 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 μm, 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.

  3. On high speed transmission with the 850nm VCSELs

    NASA Astrophysics Data System (ADS)

    Turkiewicz, Jarosław P.; Chorchos, Łukasz; Puerta Ramirez, Rafael; Vegas Olmos, Juan Jose; Ledentsov, Nikolay

    2016-09-01

    One of the key research challenges is development of energy efficient high bit rate data interconnects. The most promising solutions are based on 850 nm vertical cavity surface emitting lasers (VCSEL) and multi mode fibre (MMF). In this paper options to realize energy efficient 850 nm data interconnects are discussed and evaluated.

  4. Oxide confined 850-nm VCSELs for high-speed datacom applications

    NASA Astrophysics Data System (ADS)

    Moser, Philip; Mutig, Alex; Lott, James A.; Blokhin, Sergey; Fiol, Gerrit; Nadtochiy, Alexey M.; Ledentsov, Nikolai N.; Bimberg, Dieter

    2010-04-01

    Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and all other short-reach high-speed data transfer applications. The intrinsic limitations of copper-based electrical links at data rates exceeding 10 Gbit/s leads to a progressive movement wherein optical communication links replace traditional short-reach (300 m or shorter) copper interconnects. The wavelength of 850 nm is the standard for LAN/SAN applications as well as for several other evolving short-reach application areas including Fibre Channel, InfiniBand, Universal Serial Bus (optical USB), and active optical cables. Here we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s at low current densities of ~10 kA/cm2 ensuring device reliability and long-term stability based on conventional industry certification specifications. The relaxation resonance frequencies, damping factors, and parasitic cut-off frequencies are determined for VCSELs with oxide-confined apertures of various diameters. At the highest optical modulation rates the VCSELs' high speed operation is limited by parasitic cut-off frequencies of 24-28 GHz. We believe that by further reducing device parasitics we will produce current modulated VCSELs with optical modulation bandwidths larger than 30 GHz and data bit rates beyond 40 Gbit/s.

  5. High-speed 850 nm oxide-confined VCSELs for DATACOM applications

    NASA Astrophysics Data System (ADS)

    Mutig, Alex; Blokhin, Sergey; Nadtochiy, Alexey M.; Fiol, Gerrit; Lott, James A.; Shchukin, Vitaly A.; Ledenstov, Nikolai N.; Bimberg, Dieter

    2010-02-01

    Vertical cavity surface emitting lasers (VCSELs) are low cost and reliable light sources for high-speed local area and storage area network (LAN/SAN) optical fiber data communication systems and short-reach computer interconnects. The continuing rapid increase of serial transmission data rates driven by multi-core microprocessor's bandwidth upgrades cannot be sustained via conventional copper-based links as bit rates move beyond 10 Gbit/s and distances greater than 1 m. The intrinsic limitation of copper at high single-channel data rates facilitates the need to transition to optical fiberbased links at ever shorter distances. For LAN/SAN applications the 850 nm wavelength is standard. This same wavelength is also the standard for several other evolving short-reach application areas including Fibre Channel, CEI, USB, InfiniBand, and HDMI optical link systems. Herein we present our recent results on 850 nm oxide-confined VCSELs operating at data bit rates up to 40 Gbit/s. The low operational current density in the range of ~10 kA/cm2 ensures viable device reliability and long-term stability based on well-known industry certification specifications. Key VCSEL device parameters including the relaxation resonance frequency, damping, and parasitic cut-off frequency are determined for VCSELs with oxide-confined apertures of various diameters. We find that a parasitic cut-off frequency of 24-28 GHz limits the VCSEL's high speed operation at the highest optical modulation rates. We believe that with some effort the device parasitics can be further reduced such that current modulated VCSELs can be realized with larger than 30 GHz optical modulation bandwidth and reliable and practical operation beyond 40 Gbit/s.

  6. Dynamic Range of Vertical Cavity Surface Emitting Lasers in Multimode Links

    SciTech Connect

    Lee, H.L.T.; Dalal, R.V.; Ram, R.J.; Choquette, K.D.

    1999-07-07

    The authors report spurious free dynamic range measurements of 850nm vertical cavity surface emitting lasers in short multimode links for radio frequency communication. For a 27m fiber link, the dynamic range at optimal bias was greater than 95dB-Hz{sup 2/3} for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free space link, they have measured the highest dynamic range in an 850nm vertical cavity surface emitting laser of 113dB-Hz{sup 2/3} at 900MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.

  7. Coupled resonator vertical cavity laser

    SciTech Connect

    Choquette, K.D.; Chow, W.W.; Hou, H.Q.; Geib, K.M.; Hammons, B.E.

    1998-01-01

    The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.

  8. Large-sensitive-area superconducting nanowire single-photon detector at 850 nm with high detection efficiency.

    PubMed

    Li, Hao; Zhang, Lu; You, Lixing; Yang, Xiaoyan; Zhang, Weijun; Liu, Xiaoyu; Chen, Sijing; Wang, Zhen; Xie, Xiaoming

    2015-06-29

    Satellite-ground quantum communication requires single-photon detectors of 850-nm wavelength with both high detection efficiency and large sensitive area. We developed superconducting nanowire single-photon detectors (SNSPDs) on one-dimensional photonic crystals, which acted as optical cavities to enhance the optical absorption, with a sensitive-area diameter of 50 μm. The fabricated multimode fiber coupled NbN SNSPDs exhibited a maximum system detection efficiency (DE) of up to 82% and a DE of 78% at a dark count rate of 100 Hz at 850-nm wavelength as well as a system jitter of 105 ps.

  9. Composite resonator vertical cavity laser diode

    SciTech Connect

    Choquette, K.D.; Hou, H.Q.; Chow, W.W.; Geib, K.M.; Hammons, B.E.

    1998-05-01

    The use of two coupled laser cavities has been employed in edge emitting semiconductor lasers for mode suppression and frequency stabilization. The incorporation of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. Composite resonators can be utilized to control spectral and temporal properties within the laser; previous studies of coupled cavity vertical cavity lasers have employed photopumped structures. The authors report the first composite resonator vertical cavity laser diode consisting of two optical cavities and three monolithic distributed Bragg reflectors. Cavity coupling effects and two techniques for external modulation of the laser are described.

  10. Progress and issues for high-speed vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Lear, Kevin L.; Al-Omari, Ahmad N.

    2007-02-01

    Extrinsic electrical, thermal, and optical issues rather than intrinsic factors currently constrain the maximum bandwidth of directly modulated vertical cavity surface emitting lasers (VCSELs). Intrinsic limits based on resonance frequency, damping, and K-factor analysis are summarized. Previous reports are used to compare parasitic circuit values and electrical 3dB bandwidths and thermal resistances. A correlation between multimode operation and junction heating with bandwidth saturation is presented. The extrinsic factors motivate modified bottom-emitting structures with no electrical pads, small mesas, copper plated heatsinks, and uniform current injection. Selected results on high speed quantum well and quantum dot VCSELs at 850 nm, 980 nm, and 1070 nm are reviewed including small-signal 3dB frequencies up to 21.5 GHz and bit rates up to 30 Gb/s.

  11. Vertical-Cavity Surface-Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Wilmsen, Carl W.; Temkin, Henryk; Coldren, Larry A.

    2002-01-01

    1. Introduction to VCSELs L. A. Coldren, C. W. Wilmsen and H. Temkin; 2. Fundamental issues in VCSEL design L. A. Coldren and Eric R. Hegblom; 3. Enhancement of spontaneous emission in microcavities E. F. Schubert and N. E. J. Hunt; 4. Epitaxy of vertical-cavity lasers R. P. Schneider Jr and Y. H. Young; 5. Fabrication and performance of vertical-cavity surface-emitting lasers Kent D. Choquette and Kent Geib; 6. Polarization related properties of vertical cavity lasers Dmitri Kuksenkov and Henryk Temkin; 7. Visible light emitting vertical cavity lasers Robert L. Thornton; 8. Long-wavelength vertical-cavity lasers Dubrakovo I. Babic, Joachim Piprek and John E. Bowers; 9. Overview of VCSEL applications Richard C. Williamson; 10. Optical interconnection applications and required characteristics Kenichi Kasahara; 11. VCSEL-based fiber-optic data communications Kenneth Hahn and Kirk Giboney; 12. VCSEL-based smart pixels for free space optoelectronic processing C. W. Wilmsen.

  12. Coupled Resonator Vertical Cavity Laser Diode

    SciTech Connect

    CHOQUETTE, KENT D.; CHOW, WENG W.; FISCHER, ARTHUR J.; GEIB, KENT M.; HOU, HONG Q.

    1999-09-16

    We report the operation of an electrically injected monolithic coupled resonator vertical cavity laser which consists of an active cavity containing In{sub x}Ga{sub 1{minus}x}As quantum wells optically coupled to a passive GaAs cavity. This device demonstrates novel modulation characteristics arising from dynamic changes in the coupling between the active and passive cavities. A composite mode theory is used to model the output modulation of the coupled resonator vertical cavity laser. It is shown that the laser intensity can be modulated by either forward or reverse biasing the passive cavity. Under forward biasing, the modulation is due to carrier induced changes in the refractive index, while for reverse bias operation the modulation is caused by field dependent cavity enhanced absorption.

  13. Articular Cartilage Optical Properties in the Spectral Range 300-850 nm.

    PubMed

    Ebert, D W; Roberts, C; Farrar, S K; Johnston, W M; Litsky, A S; Bertone, A L

    1998-07-01

    Measurements of absolute total reflectance were recorded from weight-bearing (n=9) and nonweight-bearing (n=9) equine articular cartilage specimens from 300 to 850 nm using a spectrophotometer with integrating sphere attachment. Following correction of measured spectra for interfacial reflections and edge losses, Kubelka-Munk theory was applied to estimate absorption and scattering coefficient, one-dimensional light intensity distribution, and light penetration depth. Kubelka-Munk absorption coefficients ranged from ∼7 cm-1 at 330 nm to ∼1 cm-1 at 850 nm. A localized absorption peak was noted at ∼340 nm. Above 510 nm, weight-bearing cartilage demonstrated significantly higher absorption coefficients than nonweight-bearing tissue (paired t-test, p<0.05). Kubelka-Munk scattering coefficients ranged from ∼40 cm-1 at 360 nm to ∼6 cm-1 at 850 nm. No statistical differences in scattering coefficient were noted between weight-bearing and nonweight-bearing tissue. Penetration depths predicted by Kubelka-Munk theory ranged from 0.6 mm at 350 nm to over 3 mm at 850 nm. Stronger absorption in weight-bearing cartilage compared to nonweight-bearing tissue resulted in lower light penetration depths in weight-bearing cartilage at all wavelengths longer than 510 nm. © 1998 Society of Photo-Optical Instrumentation Engineers.

  14. Articular cartilage optical properties in the spectral range 300--850 nm

    NASA Astrophysics Data System (ADS)

    Ebert, Daniel W.; Roberts, Cynthia J.; Farrar, Stuart K.; Johnston, William M.; Litsky, Alan S.; Bertone, Alicia L.

    1998-07-01

    Measurements of absolute total reflectance were recorded from weight-bearing (n equals 9) and nonweight-bearing (n equals 9) equine articular cartilage specimens from 300 to 850 nm using a spectrophotometer with integrating sphere attachment. Following correction of measured spectra for interfacial reflections and edge losses, Kubelka-Munk theory was applied to estimate absorption and scattering coefficient, 1D light intensity distribution, and light penetration depth. Kubelka-Munk absorption coefficients ranged from approximately 7 cm-1 at 330 nm to approximately 1 cm-1 at 850 nm. A localized absorption peak was noted at approximately 340 nm. Above 510 nm, weight-bearing cartilage demonstrated significantly higher absorption coefficients than nonweight-bearing tissue (paired t-test, p < 0.05). Kubelka-Munk scattering coefficients ranged from approximately 40 cm-1 at 360 nm to approximately 6 cm-1 at 850 nm. No statistical differences in scattering coefficient were noted between weight-bearing and nonweight-bearing tissue. Penetration depths predicted by Kubelka-Munk theory ranged from 0.6 mm at 350 nm to over 3 mm at 850 nm. Stronger absorption in weight-bearing cartilage compared to nonweight-bearing tissue resulted in lower light penetration depths in weight-bearing cartilage at all wavelengths longer than 510 nm.

  15. Simulation and fabrication of monolithically integrated MSM/PHEMT 850 nm optical receiver front end

    NASA Astrophysics Data System (ADS)

    Fan, Chao; Chen, Tang-Sheng; Jiao, Shi-Long; Liu, Lin; Chen, Zhen-Long; Wang, Yu-Lin; Wu, Yun-Feng; Ye, Yu-Tang

    2007-12-01

    An 850 nm monolithically integrated optical receiver front end has been simulated by ATLAS and developed based on 0.5 μm GaAs PHEMT process, which comprises a metal-semiconductor-metal (MSM) photodetector and a distributed amplifier.The output eye diagrams for 2.5 Gb/s and 5Gb/s NRZ pseudorandom binary sequence are attained. Compared to the characteristics of actual device, this contribution details a simulation strategy for accurate prediction of the unilluminated performances of the devices.

  16. 30 Gbps 4-PAM transmission over 200 m of MMF using an 850 nm VCSEL.

    PubMed

    Szczerba, Krzysztof; Westbergh, Petter; Karout, Johnny; Gustavsson, Johan; Haglund, Åsa; Karlsson, Magnus; Andrekson, Peter; Agrell, Erik; Larsson, Anders

    2011-12-12

    We present high speed real time, error free 4-PAM transmission for short range optical links based on a VCSEL operating at 850 nm, a multimode fibre and a simple intensity detector. Transmission speeds of 25 Gbps and 30 Gbps are demonstrated, and the maximum fibre reaches were 300 m and 200 m, respectively. The 4-PAM is also compared with OOK transmission at 25 Gbps, and we find that at this bit rate 4-PAM increases the error free transmission distance in the multimode fibre by 100 m, compared to OOK.

  17. SC-FDE for MMF short reach optical interconnects using directly modulated 850 nm VCSELs.

    PubMed

    Teichmann, Victor S C; Barreto, Andre N; Pham, Tien-Thang; Rodes, Roberto; Monroy, Idelfonso T; Mello, Darli A A

    2012-11-05

    We propose the use of single-carrier frequency-domain equalization (SC-FDE) for the compensation of modal dispersion in short distance optical links using multimode fibers and 850 nm VCSELs. By post-processing of experimental data, we demonstrate, at 7.9% overhead, the error-free transmission (over a 4 Mbit sequence) of OOK-modulated 5 Gbps over 2443 meters of OM3 fiber (with a nominal 3300 MHz×km bandwidth). The proposed solution may be applied as a low cost alternative for data center and supercomputer interconnects.

  18. Engineering high-performance vertical cavity lasers

    SciTech Connect

    Lear, K.L.; Hou, H.Q.; Hietala, V.M.; Choquette, K.D.; Schneider, R.P. Jr.

    1996-12-31

    The cw and high-speed performance of vertical cavity surface emitting laser diodes (VCSELs) are affected by both electrical and optical issues arising from the geometry and fabrication of these devices. Structures with low resistance semiconductor mirrors and Al-oxide confinement layers address these issues and have produced record performance including 50% power conversion efficiency and modulation bandwidths up to 20 GHz at small bias currents.

  19. Long wavelength vertical cavity surface emitting laser

    DOEpatents

    Choquette, Kent D.; Klem, John F.

    2005-08-16

    Selectively oxidized vertical cavity lasers emitting near 1300 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave below, at and above room temperature. The lasers employ two n-type Al.sub.0.94 Ga.sub.0.06 As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the active region, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55.degree. C.

  20. Optimal design of 850 nm 2×2 multimode interference polymer waveguide coupler by imprint technique

    NASA Astrophysics Data System (ADS)

    Shao, Yuchen; Han, Xiuyou; Han, Xiaonan; Lu, Zhili; Wu, Zhenlin; Teng, Jie; Wang, Jinyan; Morthier, Geert; Zhao, Mingshan

    2016-09-01

    A 2×2 optical waveguide coupler at 850 nm based on the multimode interference (MMI) structure with the polysilsesquioxanes liquid series (PSQ-Ls) polymer material and the imprint technique is presented. The influence of the structural parameters, such as the single mode condition, the waveguide spacing of input/output ports, and the width and length of the multimode waveguide, on the optical splitting performance including the excess loss and the uniformity is simulated by the beam propagation method. By inserting a taper section of isosceles trapezoid between the single mode and multimode waveguides, the optimized structural parameters for low excess loss and high uniformity are obtained with the excess loss of‒0.040 dB and the uniformity of‒0.007 dB. The effect of the structure deviations induced during the imprint process on the optical splitting performance at different residual layer thicknesses is also investigated. The analysis results provide useful instructions for the waveguide device fabrication.

  1. Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design

    SciTech Connect

    Wang, Haipeng; Cheng, Guangfeng; Clemens, William; Davis, G; Macha, Kurt; Overton, Roland; Spell, D.

    2015-09-01

    After the electromagnetic design and the mechanical design of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported.

  2. High-speed vertical cavity surface emitting lasers

    SciTech Connect

    Lear, K.L.; Ochiai, M.; Hietala, V.M.

    1997-03-01

    High speed modulation and pulsing are reported for oxide-confined vertical cavity surface emitting laser diodes (VCSELs) with inverted doping and proton implantation to reduce the extrinsic limitations.

  3. Electrically injected visible vertical cavity surface emitting laser diodes

    DOEpatents

    Schneider, R.P.; Lott, J.A.

    1994-09-27

    Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors. 5 figs.

  4. Highly uniform and reproducible visible to near-infrared vertical-cavity surface-emitting lasers grown by MOVPE

    SciTech Connect

    Hou, H.Q.; Choquette, K.D.; Hammons, B.E.; Breiland, W.G.; Crawford, M.H.; Lear, K.L.

    1997-05-01

    The authors present the growth and characterization of vertical-cavity surface emitting lasers (VCSELs) from visible to near-infrared wavelength grown by metalorganic vapor phase epitaxy. Discussions on the growth issue of VCSEL materials include the control on growth rate and composition using an in situ normal-incidence reflectometer, optimization of ultra-high material uniformity, and comprehensive p- and n-type doping study in AlGaAs by CCl{sub 4} and Si{sub 2}H{sub 6} over the entire Al composition range. They will also demonstrate the recent achievements of selectively-oxidized VCSELs which include the first room-temperature continuous-wave demonstration of all-AlGaAs 700-nm red VCSELs, high-performance n-side up 850-nm VCSELs, and low threshold current and low-threshold voltage 1.06 {micro}m VCSELs using InGaAs/GaAsP strain-compensated quantum wells.

  5. Optimum conditions of the distributed bragg reflector in 850-nm GaAs infrared light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Ahn, Su-Chang; Lee, Byung-Teak; An, Won-Chan; Kim, Dae-Kwang; Jang, In-Kyu; So, Jin-Su; Lee, Hyung-Joo

    2016-07-01

    In this paper, a distributed Bragg reflector (DBR) for a bottom reflector in 850-nm GaAs infrared light-emitting diodes (Ir-LEDs) was developed and optimized. At an 850-nm wavelength, markedly improved reflection spectra were observed from DBRs consisting of Al1-xGaxAs/AlxGa1-xAs materials. In addition, the reflection spectra of Al1-xGaxAs/AlxGa1-xAs-based DBRs was found to increase with increasing difference between the high and the low refractive indices. At multiple layers of 10 pairs, maximal reflection spectra having about a 92% reflectivity were obtained from DBRs consisting of GaAs/AlAs. At 20 pairs, however, outstanding reflection spectra having a higher reflectivity and broader width were clearly observed from DBRs consisting of Al0.1Ga0.9As/Al0.9Ga0.1As. Some incident light appears to have been absorbed and confined by the narrow bandgap of the GaAs material used in DBRs consisting of GaAs/AlAs. This fact could be supported by the decrease in the reflectivity of the shorter wavelength region in DBRs consisting of GaAs/AlAs. For this reason, a remarkable output power could be obtained from the 850-nm GaAs Ir-LED chip having a DBR consisting of Al0.1Ga0.9As/Al0.9Ga0.1As.

  6. Simultaneous amplification of terahertz difference frequencies by an injection-seeded semiconductor laser amplifier at 850 nm

    NASA Technical Reports Server (NTRS)

    Matsuura, S.; Chen, P.; Blake, G. A.; Pearson, J. C.; Pickett, H. M.

    1998-01-01

    Two-frequency operation of an 850 nm semiconductor optical amplifier was achieved by simultaneously injection seeding it with two diode lasers. The two frequencies could be independently amplified without strong interference when they were separated by more than 10 GHz, and the spectral purity was preserved by the amplification process. At frequency differences below 10 GHz, unbalanced two-frequency output was observed, which can be explained by a two-mode interaction driven by the refractive index modulation at the beat frequency. The laser system is suitable for the difference-frequency generation of coherent terahertz radiation in ultra-fast photoconductors or nonlinear optical media.

  7. Vertical-cavity in-plane heterostructures: Physics and applications

    SciTech Connect

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2015-11-02

    We show that in-plane (lateral) heterostructures realized in vertical cavities with high contrast grating reflectors can be used to significantly modify the anisotropic dispersion curvature, also interpreted as the photon effective mass. This design freedom enables exotic configurations of heterostructures and many interesting applications. The effects of the anisotropic photon effective mass on the mode confinement, mode spacing, and transverse modes are investigated. As a possible application, the method of boosting the speed of diode lasers by engineering the photon-photon resonance is discussed. Based on this platform, we propose a system of two laterally coupled cavities, which shows the breaking of parity-time symmetry in vertical cavity structures.

  8. Plasmon resonant cavities in vertical nanowire arrays

    SciTech Connect

    Bora, M; Bond, T; Behymer, E; Chang, A

    2010-02-23

    We investigate tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides. Resonances are observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors over 103 are possible due to plasmon focusing in the inter-wire space.

  9. Magnetic shielding for the Fermilab Vertical Cavity Test Facility

    SciTech Connect

    Ginsburg, Camille M.; Reid, Clark; Sergatskov, Dmitri A.; /Fermilab

    2008-09-01

    A superconducting RF cavity has to be shielded from magnetic fields present during cool down below the critical temperature to avoid freezing in the magnetic flux at localized impurities, thereby degrading the cavity intrinsic quality factor Q{sub 0}. The magnetic shielding designed for the Fermilab vertical cavity test facility (VCTF), a facility for CW RF vertical testing of bare ILC 1.3 GHz 9-cell SRF cavities, was recently completed. For the magnetic shielding design, we used two cylindrical layers: a room temperature 'outer' shield of Amumetal (80% Ni alloy), and a 2K 'inner' shield of Cryoperm 10. The magnetic and mechanical design of the magnetic shielding and measurement of the remanent magnetic field inside the shielding are described.

  10. Plasmon resonant cavities in vertical nanowire arrays

    DOEpatents

    Bora, Mihail; Bond, Tiziana C.; Fasenfest, Benjamin J.; Behymer, Elaine M.

    2014-07-15

    Tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides are presented. Resonances can be observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides can satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors of over 10.sup.3 are possible due to plasmon focusing in the inter-wire space.

  11. Vector cavity solitons in broad area Vertical-Cavity Surface-Emitting Lasers

    PubMed Central

    Averlant, Etienne; Tlidi, Mustapha; Thienpont, Hugo; Ackemann, Thorsten; Panajotov, Krassimir

    2016-01-01

    We report the experimental observation of two-dimensional vector cavity solitons in a Vertical-Cavity Surface-Emitting Laser (VCSEL) under linearly polarized optical injection when varying optical injection linear polarization direction. The polarization of the cavity soliton is not the one of the optical injection as it acquires a distinct ellipticity. These experimental results are qualitatively reproduced by the spin-flip VCSEL model. Our findings open the road to polarization multiplexing when using cavity solitons in broad-area lasers as pixels in information technology. PMID:26847004

  12. Cryogenic infrastructure for Fermilab's ILC vertical cavity test facility

    SciTech Connect

    Carcagno, R.; Ginsburg, C.; Huang, Y.; Norris, B.; Ozelis, J.; Peterson, T.; Poloubotko, V.; Rabehl, R.; Sylvester, C.; Wong, M.; /Fermilab

    2006-06-01

    Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R&D and pre-production testing of bare 9-cell, 1.3-GHz superconducting RF (SRF) cavities for the International Linear Collider (ILC) program. This facility is located in the existing Industrial Building 1 (IB1) where the Magnet Test Facility (MTF) also resides. Helium and nitrogen cryogenics are shared between the VCTF and MTF including the existing 1500-W at 4.5-K helium refrigerator with vacuum pumping for super-fluid operation (125-W capacity at 2-K). The VCTF is being constructed in multiple phases. The first phase is scheduled for completion in mid 2007, and includes modifications to the IB1 cryogenic infrastructure to allow helium cooling to be directed to either the VCTF or MTF as scheduling demands require. At this stage, the VCTF consists of one Vertical Test Stand (VTS) cryostat for the testing of one cavity in a 2-K helium bath. Planning is underway to provide a total of three Vertical Test Stands at VCTF, each capable of accommodating two cavities. Cryogenic infrastructure improvements necessary to support these additional VCTF test stands include a dedicated ambient temperature vacuum pump, a new helium purification skid, and the addition of helium gas storage. This paper describes the system design and initial cryogenic operation results for the first VCTF phase, and outlines future cryogenic infrastructure upgrade plans for expanding to three Vertical Test Stands.

  13. Cryogenic vertical test facility for the SRF cavities at BNL

    SciTech Connect

    Than, R.; Liaw, CJ; Porqueddu, R.; Grau, M.; Tuozzolo, J.; Tallerico, T.; McIntyre, G.; Lederle, D.; Ben-Zvi, I.; Burrill, A.; Pate, D.

    2011-03-28

    A vertical test facility has been constructed to test SRF cavities and can be utilized for other applications. The liquid helium volume for the large vertical dewar is approximate 2.1m tall by 1m diameter with a clearance inner diameter of 0.95m after the inner cold magnetic shield installed. For radiation enclosure, the test dewar is located inside a concrete block structure. The structure is above ground, accessible from the top, and equipped with a retractable concrete roof. A second radiation concrete facility, with ground level access via a labyrinth, is also available for testing smaller cavities in 2 smaller dewars. The cryogenic transfer lines installation between the large vertical test dewar and the cryo plant's sub components is currently near completion. Controls and instrumentations wiring are also nearing completion. The Vertical Test Facility will allow onsite testing of SRF cavities with a maximum overall envelope of 0.9 m diameter and 2.1 m height in the large dewar and smaller SRF cavities and assemblies with a maximum overall envelope of 0.66 m diameter and 1.6 m height.

  14. Research of the use of silver nanowires as a current spreading layer on vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Guo, Xia; Shi, Lei; Li, Chong; Dong, Jian; Liu, Bai; Hu, Shuai; He, Yan

    2016-11-01

    Silver nanowire (AgNW) film was proposed to apply on the surface of the vertical-cavity surface-emitting lasers (VCSELs) with large aperture in order to obtain a uniform current distribution in the active region and a better optical beam quality. Optimization of the AgNW film was carried out with the sheet resistance of 28.4 Ω/sq and the optical transmission of 94.8% at 850 nm. The performance of VCSELs with and without AgNW film was studied. When the AgNW film was applied to the surface of VCSELs, due to its better current spreading effect, the maximum output optical power increased from 23.4 mW to 24.4 mW, the lasing wavelength redshift decreased from 0.085 nm/mA to 0.077 nm/mA, the differential resistance decreased from 23.95 Ω to 21.13 Ω, and the far field pattern at 50 mA decreased from 21.6° to 19.2°. At the same time, the near field test results showed that the light in the aperture was more uniform, and the far field exhibited a better single peak characteristic. Various results showed that VCSELs with AgNW on the surface showed better beam quality. Project supported by the National Natural Science Foundation of China (Grant Nos. 61335004 and 61505003), the National High Technology Research and Development Program of China (Grant No. 2015AA017101), and the National Key Research and Development of China (Grant No. 2016YFB0400603).

  15. Spectroscopic refractive indices of monoclinic single crystal and ceramic Lutetium oxyorthosilicate (LSO) from 200 to 850 nm

    SciTech Connect

    Jellison Jr, Gerald Earle; Specht, Eliot D; Boatner, Lynn A; Singh, David J; Melcher, Charles L

    2012-01-01

    The four real values of the dielectric function tensor of the monoclinic crystal Lu2SiO5 or lutetium oxyorthosilicate (LSO) have been determined using generalized ellipsometry from 200 to 850 nm. The three principal values are fit to the Sellmeier model, and they indicate that the band gap of LSO is less than ~9 eV. The off-diagonal element 12 is non-zero over the entire spectrum, but it is very close to zero for wavelengths longer than ~400 nm, indicating that structurally monoclinic LSO is nearly optically orthorhombic in this wavelength region. The spectroscopic dielectric functions of three isotropic ceramic LSO samples are presented, which are consistent with the dielectric functions of single-crystal LSO when the effects of porosity are included. As a comparison, the dielectric functions are also determined using relativistic electronic structure and optical calculations based on the recently developed potential functional of Tran and Blaha (Phys. Rev. Lett. 102, 226401 (2009).)

  16. Dynamics of a vertical cavity quantum cascade phonon laser structure

    NASA Astrophysics Data System (ADS)

    Maryam, W.; Akimov, A. V.; Campion, R. P.; Kent, A. J.

    2013-07-01

    Driven primarily by scientific curiosity, but also by the potential applications of intense sources of coherent sound, researchers have targeted the phonon laser (saser) since the invention of the optical laser over 50 years ago. Here we fabricate a vertical cavity structure designed to operate as a saser oscillator device at a frequency of 325 GHz. It is based on a semiconductor superlattice gain medium, inside a multimode cavity between two acoustic Bragg reflectors. We measure the acoustic output of the device as a function of time after applying electrical pumping. The emission builds in intensity reaching a steady state on a timescale of order 0.1 μs. We show that the results are consistent with a model of the dynamics of a saser cavity exactly analogous to the models used for describing laser dynamics. We also obtain estimates for the gain coefficient, steady-state acoustic power output and efficiency of the device.

  17. FM transmission of video signals beyond of the baseband of a 1-km 62.5 μm MMF at the 850 nm wavelength

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Marcin

    2009-06-01

    The paper presents the first, to the best knowledge of the author, successful transmission of the video signal beyond of the baseband of the multimode fibre at the 850 nm wavelength using the subcarrier multiplexing technology (SCM). The transmission system has been built on the basis of generally available, inexpensive optical and electronic components.

  18. Engineering of optical modes in vertical-cavity microresonators by aperture placement: applications to single-mode and near-field lasers

    NASA Astrophysics Data System (ADS)

    Shchukin, V. A.; Ledentsov, N. N.; Kropp, J.-R.; Steinle, G.; Ledentsov, N. N.; Choquette, K. D.; Burger, S.; Schmidt, F.

    2015-03-01

    Oxide-confined vertical cavity surface emitting lasers (VCSEL) are inherently leaky structures, despite the fact that the oxidized periphery region surrounding the all-semiconductor core has a lower refractive index. The reason is that the VCSEL modes in the non-oxidized core region can be coupled to tilted modes in the selectively oxidized periphery as the orthogonality between the core mode and the modes at the periphery is broken by the oxidation-induced optical field redistribution. Engineered VCSEL designs show that the overlap between the VCSEL mode of the core and the tilted mode in the periphery can reach >30% resulting in significant leakage. Three-dimensional modeling confirms that the leakage losses are much stronger for high order transverse modes which have a higher field intensity close to the oxidized region. Single mode lasing in the fundamental mode can thus proceed up to large aperture diameters. A 850-nm GaAlAs leaky VCSEL based on this concept is designed, modeled and fabricated, showing single-mode lasing with aperture diameters up to 5 μm. Side mode suppression ratio >20dB is realized at the current density of 10kA/cm2 in devices with the series resistance of 90 Ω.

  19. Short-wavelength vertical-cavity surface-emitting laser applications: from high-throughput multimode fiber links to two-dimensional interchip interconnections

    NASA Astrophysics Data System (ADS)

    Michalzik, Rainer; King, Roger; Mederer, Felix; Kicherer, Max; Giaretta, Giorgio; Ebeling, Karl J.

    2001-07-01

    An overview is given of recent experiments employing 850 or 980 nm emission wavelength vertical-cavity surface-emitting laser diodes (VCSELs) for high-throughput very short reach optical data transmission. For future high-speed building backbones, we demonstrate the first transport of 40 Gbit/s data rates over 300 m of a new generation multimode fiber by means of a four-channel coarse wavelength-division multiplexing system. As an attractive route to overcoming high-speed electrical signaling problems on printed circuit boards, we show 10 Gbit/s per channel data transmission for densely spaced integrated polymer waveguides. Error-free VCSEL operation at 2.5 Gbit/s with a temperature range from -20 to +100 degree(s)C indicates compatibility with most industrial requirements. Finally, we demonstrate 850-nm bottom-emitting VCSEL arrays for direct flip-chip bonding, which might prove useful for two-dimensional future silicon chip-to-chip interconnect solutions.

  20. Vertical Cavity Surface Emitting Laser sources for gas detection

    NASA Astrophysics Data System (ADS)

    Cerutti, L.; Garnache, A.; Ouvrard, A.; Garcia, M.; Genty, F.

    2005-03-01

    The molecular beam epitaxy growth conditions of a GaInAsSb/AlGaAsSb multi-quantum wells stack have been successfully optimised. This included minimising the full-width at half-maximum of the high resolution X-ray diffraction satellites and maximising the photoluminescence peak intensity collected at room temperature. Then, the optimised gain structures were successfully inserted in a) a microcavity and b) an external-cavity Vertical Cavity Surface Emitting Laser. In both cases, room temperature laser operation near 2.3 µm in the continuous wave regime, with a circular single transverse mode output beam, was demonstrated. An output power larger than 1 mW at room temperature was measured.

  1. Diffraction from oxide confinement apertures in vertical-cavity lasers

    SciTech Connect

    Roos, P.A.; Carlsten, J.L.; Kilper, D.C.; Lear, K.L.

    1999-08-01

    Direct measurement of scattered fields from oxide confinement apertures in vertical-cavity lasers is presented. Diffraction fringes associated with each transverse lasing mode are detected in the far field from devices with varying oxide aperture dimensions and with quantum efficiencies as high as 48{percent}. The diffracted pattern symmetries match the rectangular symmetry of the oxide apertures present in the devices and fringe locations are compared to Fraunhofer theory. The fraction of power diffracted from the lasing mode remains roughly constant as a function of relative pump rate, but is shown to depend on both transverse mode order and oxide aperture size. {copyright} {ital 1999 American Institute of Physics.}

  2. Vertical-cavity surface-emitting laser with liquid crystal external cavity

    NASA Astrophysics Data System (ADS)

    Xie, Y.; Beeckman, J.; Panajotov, K.; Neyts, K.

    2014-10-01

    We have developed a technology to integrate a thin layer of liquid crystal (LC) on top of a Vertical-Cavity Surface- Emitting Laser (VCSEL). Based on this technology, we demonstrate VCSELs with a chiral liquid crystal (CLC) layer, which acts as a tuneable mirror. The reflection properties of the CLC layer are controlled by temperature. Next we demonstrate VCSEL devices with tuneable external cavity using a nematic LC layer incorporated with an additional dielectric mirror (SiO2/Ta2O5). The VCSEL and the LC layer can be electrically driven independently and the optical length in the external cavity can be tuned by the applied voltage on the LC layer. In both configurations we show that the emission properties of the VCSEL can be changed, in terms of emission wavelength, polarization state and/or lasing threshold.

  3. Electro-thermo-optical simulation of vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Smagley, Vladimir Anatolievich

    Three-dimensional electro-thermal simulator based on the double-layer approximation for the active region was coupled to optical gain and optical field numerical simulators to provide a self-consistent steady-state solution of VCSEL current-voltage and current-output power characteristics. Methodology of VCSEL modeling had been established and applied to model a standard 850-nm VCSEL based on GaAs-active region and a novel intracavity-contacted 400-nm GaN-based VCSEL. Results of GaAs VCSEL simulation were in a good agreement with experiment. Correlations between current injection and radiative mode profiles have been observed. Physical sub-models of transport, optical gain and cavity optical field were developed. Carrier transport through DBRs was studied. Problem of optical fields in VCSEL cavity was treated numerically by the effective frequency method. All the sub-models were connected through spatially inhomogeneous rate equation system. It was shown that the conventional uncoupled analysis of every separate physical phenomenon would be insufficient to describe VCSEL operation.

  4. A fully-integrated 12.5-Gb/s 850-nm CMOS optical receiver based on a spatially-modulated avalanche photodetector.

    PubMed

    Lee, Myung-Jae; Youn, Jin-Sung; Park, Kang-Yeob; Choi, Woo-Young

    2014-02-10

    We present a fully integrated 12.5-Gb/s optical receiver fabricated with standard 0.13-µm complementary metal-oxide-semiconductor (CMOS) technology for 850-nm optical interconnect applications. Our integrated optical receiver includes a newly proposed CMOS-compatible spatially-modulated avalanche photodetector, which provides larger photodetection bandwidth than previously reported CMOS-compatible photodetectors. The receiver also has high-speed CMOS circuits including transimpedance amplifier, DC-balanced buffer, equalizer, and limiting amplifier. With the fabricated optical receiver, detection of 12.5-Gb/s optical data is successfully achieved at 5.8 pJ/bit. Our receiver achieves the highest data rate ever reported for 850-nm integrated CMOS optical receivers.

  5. Rate equations for vertical-cavity surface-emitting lasers

    SciTech Connect

    Sande, Guy van der; Danckaert, Jan; Veretennicoff, Irina; Erneux, Thomas

    2003-01-01

    By applying a multiple time scale perturbation method, we simplify the spin-flip model equations [San Miguel et al., Phys. Rev. A 52, 1728 (1995)] describing the polarization behavior of vertical-cavity surface-emitting lasers. The reduced problem consists of three rate equations for a two-mode semiconductor laser. The asymptotic theory is based on the natural values of the laser parameters and considers the case of large values of the spin-flip rate and birefringence with respect to the relaxation oscillation frequency. Our analysis corrects and complements previous derivations of rate equations from the spin-flip model equations. We find that the cross-gain saturation coefficients due to spin-flip processes are not symmetric and may become negative. As a result, a new physical interpretation of polarization switching from the high-frequency mode to the low-frequency mode and for high values of the birefringence is possible.

  6. High-temperature long-wavelength vertical-cavity lasers

    NASA Astrophysics Data System (ADS)

    Margalit, Near Moses

    Vertical cavity lasers(VCLs) have recently been the subject of much research effort around the world. These lasers hold the promise of inexpensive, low threshold, high speed sources for optical communication. Short wavelength lasers have many applications, including free space optical interconnects and short distance datacom, but have limited potential for longer distances due to the absorption and dispersion spectrum of standard optical fiber. The longer wavelength sources near 1.3 or 1.5 /mu m are ideally suited for medium and long distance applications. Interoperability as well as compatibility with existing fiber optic infrastructure also call for longer wavelength sources. However, large volume commercialization of such devices, for applications such as FTTH(fiber to the home), requires a wide temperature range of operation ([-]40o C to 85o C). Historically, the realization of such high performance long-wavelength vertical cavity- lasers has been difficult. Nonetheless, advances in fabrication techniques, such as wafer fusion, have allowed for ever increasing device performance. In this thesis, we present recent results that include devices with multigigahetz frequency responses, hundred of microwatts of cw output powers, as well as 65o C continuous-wave operating temperatures. In addition, these devices have now been demonstrated as sources in link transmission experiment at 2.5 Gb/s over 200 km of optical fiber, far surpassing the record distance-bandwidth products of any other VCL experiment. We analyze here the design and fabrication of these record performance devices. Further advancements may soon lead to commercial level performance.

  7. Visible light emitting vertical cavity surface emitting lasers

    DOEpatents

    Bryan, Robert P.; Olbright, Gregory R.; Lott, James A.; Schneider, Jr., Richard P.

    1995-01-01

    A vertical cavity surface emitting laser that emits visible radiation is built upon a substrate, then having mirrors, the first mirror on top of the substrate; both sets of mirrors being a distributed Bragg reflector of either dielectrics or other materials which affect the resistivity or of semiconductors, such that the structure within the mirror comprises a plurality of sets, each having a thickness of .lambda./2n where n is the index of refraction of each of the sets; each of the mirrors adjacent to spacers which are on either side of an optically active bulk or quantum well layer; and the spacers and the optically active layer are from one of the following material systems: In.sub.z (Al.sub.y Ga.sub.1-y).sub.1-z P, InAlGaAs, AlGaAs, InGaAs, or AlGaP/GaP, wherein the optically active region having a length equal to m .lambda./2n.sub.eff where m is an integer and n.sub.eff is the effective index of refraction of the laser cavity, and the spacer layer and one of the mirrors being transmissive to radiation having a wavelength of .lambda./n, typically within the green to red portion of the visible spectrum.

  8. Visible light emitting vertical cavity surface emitting lasers

    DOEpatents

    Bryan, R.P.; Olbright, G.R.; Lott, J.A.; Schneider, R.P. Jr.

    1995-06-27

    A vertical cavity surface emitting laser that emits visible radiation is built upon a substrate, then having mirrors, the first mirror on top of the substrate; both sets of mirrors being a distributed Bragg reflector of either dielectrics or other materials which affect the resistivity or of semiconductors, such that the structure within the mirror comprises a plurality of sets, each having a thickness of {lambda}/2n where n is the index of refraction of each of the sets; each of the mirrors adjacent to spacers which are on either side of an optically active bulk or quantum well layer; and the spacers and the optically active layer are from one of the following material systems: In{sub z}(Al{sub y}Ga{sub 1{minus}y}){sub 1{minus}z}P, InAlGaAs, AlGaAs, InGaAs, or AlGaP/GaP, wherein the optically active region having a length equal to m {lambda}/2n{sub eff} where m is an integer and n{sub eff} is the effective index of refraction of the laser cavity, and the spacer layer and one of the mirrors being transmissive to radiation having a wavelength of {lambda}/n, typically within the green to red portion of the visible spectrum. 10 figs.

  9. Time-dependent numerical simulation of vertical cavity lasers

    SciTech Connect

    Thode, L.E.; Csanak, G.; So, L.L.; Kwan, T.J.T.; Campbell, M.

    1994-12-31

    To simulate vertical cavity surface emitting lasers (VCSELs), the authors are developing a three-dimensional, time-dependent field-gain model with absorption in bulk dielectric regions and gain in quantum well regions. Since the laser linewidth is narrow, the bulk absorption coefficient is assumed to be independent of frequency with a value determined by the material and the lattice temperature. In contrast, the frequency-dependent gain regions must be solved consistently in the time domain. Treatment of frequency-dependent media in a finite-difference time-domain code is computationally intensive. However, because the volume of the quantum well regions is small relative to the volume of the multilayer dielectric (MLD) mirror regions, the computational overhead is reasonable. A key issue is the calculation of the fields in the MLD mirror regions. Although computationally intensive, good agreement has been obtained between simulation results and matrix equation solutions for the reflection coefficient, transmission coefficient, and bandwidth of MLD mirrors. The authors discuss the development and testing of the two-dimensional field-gain model. This field-gain model will be integrated with a carrier transport model to form the self-consistent laser code, VCSEL.

  10. Integration of photoactive and electroactive components with vertical cavity surface emitting lasers

    DOEpatents

    Bryan, R.P.; Esherick, P.; Jewell, J.L.; Lear, K.L.; Olbright, G.R.

    1997-04-29

    A monolithically integrated optoelectronic device is provided which integrates a vertical cavity surface emitting laser and either a photosensitive or an electrosensitive device either as input or output to the vertical cavity surface emitting laser either in parallel or series connection. Both vertical and side-by-side arrangements are disclosed, and optical and electronic feedback means are provided. Arrays of these devices can be configured to enable optical computing and neural network applications. 9 figs.

  11. Integration of photoactive and electroactive components with vertical cavity surface emitting lasers

    DOEpatents

    Bryan, Robert P.; Esherick, Peter; Jewell, Jack L.; Lear, Kevin L.; Olbright, Gregory R.

    1997-01-01

    A monolithically integrated optoelectronic device is provided which integrates a vertical cavity surface emitting laser and either a photosensitive or an electrosensitive device either as input or output to the vertical cavity surface emitting laser either in parallel or series connection. Both vertical and side-by-side arrangements are disclosed, and optical and electronic feedback means are provided. Arrays of these devices can be configured to enable optical computing and neural network applications.

  12. Red vertical cavity surface emitting lasers (VCSELs) for consumer applications

    NASA Astrophysics Data System (ADS)

    Duggan, Geoffrey; Barrow, David A.; Calvert, Tim; Maute, Markus; Hung, Vincent; McGarvey, Brian; Lambkin, John D.; Wipiejewski, Torsten

    2008-02-01

    There are many potential applications of visible, red (650nm - 690nm) vertical cavity surface emitting lasers (VCSELs) including high speed (Gb) communications using plastic optical fiber (POF), laser mouse sensors, metrology, position sensing. Uncertainty regarding the reliability of red VCSELs has long been perceived as the most significant roadblock to their commercialization. In this paper we will present data on red VCSELs optimized for performance and reliability that will allow exploitation of this class of VCSEL in a wide range of high volume consumer, communication and medical applications. VCSELs operating at ~665nm have been fabricated on 4" GaAs substrates using MOCVD as the growth process and using standard VCSEL processing technology. The active region is AlGaInP-based and the DBR mirrors are made from AlGaAs. Threshold currents are typically less than 2mA, the devices operate up to >60C and the light output is polarized in a stable, linear characteristic over all normal operating conditions. The 3dB modulation bandwidth of the devices is in excess of 3GHz and we have demonstrated the operation of a transceiver module operating at 1.25Gb/s over both SI-POF and GI-POF. Ageing experiments carried out using a matrix of current and temperature stress conditions allows us to estimate that the time to failure of 1% of devices (TT1%F) is over 200,000h for reasonable use conditions - making these red VCSELs ready for commercial exploitation in a variety of consumer-type applications. Experiments using appropriate pulsed driving conditions have resulted in operation of 665nm VCSELs at a temperature of 85°C whilst still offering powers useable for eye-safe free space and POF communications.

  13. Heterogeneously bonded vertical cavity surface emitting lasers and thermal modeling

    NASA Astrophysics Data System (ADS)

    Jeong, Hyejin

    Typically semiconductor materials used for photonic devices have been limited to those exhibiting a direct bandgap. In order to incorporate indirect bandgap and non-semiconducting materials, extensive research efforts have been put into developing hybrid photonic devices, which consist of different materials for the light emitting region and the substrate. In this dissertation, a post-fabrication bonding technique for integrating semiconductor vertical cavity surface emitting lasers (VCSELs) onto hybrid substrates is demonstrated. This approach provides flexibility regarding the choice of device fabrication and hybrid substrate materials. Light output versus injected current and applied voltage characteristics of lasers are measured before and after the transfer process. VCSEL arrays transferred onto Si substrate show that the transfer technique does not degrade the laser performance. VCSEL transfer onto a polyethylene terephthalate (PET) substrate allows for flexible arrays, but with degraded performance due to excessive thermal dissipation. A VCSEL array with an area of 1.0 x 1.2 mm2 is transferred onto a Cu substrate which has a higher thermal conductivity compared to both GaAs and PET. For the transfer bonding process, the final device yield is enhanced by including an etch stop layer in the epitaxial wafer. In order to study the effect of the thermal conductivity of the substrate on the dissipation of heat from the VCSELs, we present a simple VCSEL electro-thermal model, in which an agreement is obtained between simulation and experiment for lasing wavelength with varying laser diameter. Using this model, the thermal limitations of the VCSEL output on different substrates is discussed.

  14. Result of MHI 2-Cell Seamless Dumb-Bell Cavity Vertical Test

    SciTech Connect

    Okihira, K.; Hara, H.; Ikeda, N.; Inoue, F.; Sennyu, K.; Geng, Rongli; Rimmer, Robert A.; Kako, E.

    2014-12-01

    MHI have supplied several 9-cell cavities for STF (R&D of ILC project at KEK) and have been considering production method for stable quality and cost reduction, seamless dumb-bell cavity was one of them. We had fabricated a 2 cell seamless dumb-bell cavity for cost reduction and measured RF performance in collaboration with JLab, KEK and MHI. Surface treatment recipe for ILC was applied for MHI 2-cell cavity and vertical test was performed at JLab. The cavity reached Eacc=32.4MV/m after BCP and EP. Details of the result are reported.

  15. Coupled-resonator vertical-cavity lasers with two active gain regions

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-05-20

    A new class of coupled-resonator vertical-cavity semiconductor lasers has been developed. These lasers have multiple resonant cavities containing regions of active laser media, resulting in a multi-terminal laser component with a wide range of novel properties.

  16. Bistable output from a coupled-resonator vertical-cavity laser diode

    NASA Astrophysics Data System (ADS)

    Fischer, A. J.; Choquette, K. D.; Chow, W. W.; Allerman, A. A.; Geib, K. M.

    2000-11-01

    We report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits bistable behavior in the light output versus injection current. Large bistability regions over current ranges as wide as 18 mA have been observed with on/off contrast ratios of greater than 20 dB. The position and width of the bistability region can be varied by changing the bias to the top cavity. Switching between on and off states can be accomplished with changes as small as 250 μW to the electrical power applied to the top cavity. The bistable behavior is the response of the nonlinear susceptibility in the top cavity to the changes in the bottom intracavity laser intensity as the bottom cavity reaches the thermal rollover point.

  17. 3.9 GHz superconducting accelerating 9-cell cavity vertical test results

    SciTech Connect

    Khabiboulline, Timergali; Cooper, Charles; Dhanaraj, Nandhini; Edwards, Helen; Foley, Mike; Harms, Elvin; Mitchell, Donald; Rowe, Allan; Solyak, Nikolay; Moeller, Wolf-Dietrich; /DESY

    2007-06-01

    The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve the beam performance of the FLASH (TTF/DESY) facility [1]. In the frame of a collaborative agreement, Fermilab will provide DESY with a cryomodule containing a string of four cavities. In addition, a second cryomodule with one cavity will be fabricated for installation in the Fermilab photo-injector, which will be upgraded for the ILC accelerator test facility. The first 9-cell Nb cavities were tested in a vertical setup and they didn't reach the designed accelerating gradient [2]. The main problem was a multipactor in the HOM couplers, which lead to overheating and quenching of the HOM couplers. New HOM couplers with improved design are integrated in the next 9-cell cavities. In this paper we present all results of the vertical tests.

  18. Vertical and horizontal test results of 3.9-GHz accelerating cavities at FNAL

    SciTech Connect

    Khabiboulline, T.; Edwards, H.; Foley, M.; Harms, E.; Hocker, James Andrew; Mitchell, D.; Rowe, A.; Solyak, N.; /Fermilab

    2008-06-01

    The 3rd harmonic 3.9GHz accelerating cavity was proposed to improve the beam performance of the VUV FEL, FLASH. In the frame of a collaborative agreement, Fermilab will provide DESY with a cryomodule containing a string of four cavities. Seven 9-cell Nb cavities were tested and six of them did reach accelerating gradient up to 24 MV/m almost twice more than design value of 14 MV/m. Two of these cavities are with new HOM couplers with improved design. In this paper we present all results of the vertical and horizontal tests.

  19. Sub-gigahertz beam switching of vertical-cavity surface-emitting laser with transverse coupled cavity

    NASA Astrophysics Data System (ADS)

    Nakahama, M.; Gu, X.; Sakaguchi, T.; Matsutani, A.; Ahmed, M.; Bakry, A.; Koyama, F.

    2015-08-01

    We report a high-speed electrical beam switching of vertical cavity surface emitting laser with a transverse coupled cavity. A high speed (sub-gigahertz) and large deflection angle (>30°) beam switching is demonstrated by employing the transverse mode switching. The angular switching speed of 900 MHz is achieved with narrow beam divergence of below 4° and extinction ratio of 8 dB. We also measured the near- and far-field patterns to clarify the origin of the beam switching. We present a simple one-dimensional Bragg reflector waveguide model, which well predicts the beam switching characteristic.

  20. Sub-gigahertz beam switching of vertical-cavity surface-emitting laser with transverse coupled cavity

    SciTech Connect

    Nakahama, M.; Gu, X.; Sakaguchi, T.; Matsutani, A.; Ahmed, M.; Bakry, A.; Koyama, F.

    2015-08-17

    We report a high-speed electrical beam switching of vertical cavity surface emitting laser with a transverse coupled cavity. A high speed (sub-gigahertz) and large deflection angle (>30°) beam switching is demonstrated by employing the transverse mode switching. The angular switching speed of 900 MHz is achieved with narrow beam divergence of below 4° and extinction ratio of 8 dB. We also measured the near- and far-field patterns to clarify the origin of the beam switching. We present a simple one-dimensional Bragg reflector waveguide model, which well predicts the beam switching characteristic.

  1. Stimulation of 450, 650 and 850-nm optical emissions from custom designed silicon LED devices by utilizing carrier energy and carrier momentum engineering

    NASA Astrophysics Data System (ADS)

    Snyman, L. W.; Polleux, J.-L.; Xu, K.

    2016-02-01

    Optical emission probabilities from silicon were analyzed by appropriate modelling, taking the silicon energy band structure, available carrier energy spread, and available carrier momentum spreads that can be realized with typical device design and operating conditions as available in current silicon technologies. The analyses showed that creation of micron-dimensioned conduction channels as made possible by using a RF bipolar fabrication process, appropriate doping and variations in the channel utilizing Boron, Phosphorous and Germanium doping, and using reversed biased junctions to energize specifically electrons, appropriately controlling carrier energy and carrier density, and control over carrier momentum through appropriate impurity scattering technology; particularly, 280nm, 650nm and 850nm emissions can be stimulated. Particularly, using p+nn and p+np+ device designs with appropriate control over carrier energy, carrier type balancing and implementing enhanced impurity scattering in some device regions, show the greatest potential to enhance these emissions. First iteration empirically conducted device realizations results show interesting peaking features and nonuniform high intensity behaviors. Particularly, it was succeeded to increase the emissions at 650nm with about two orders of magnitude. Internal electrical- to- optical conversion efficiencies of up to 10-4 and intensity emissions of up to 200 nW μm2 are derived, with further prospects to increase emissions further. The attained results compare extremely favorable, and in some cases exceeds, results as published by Venter et al, Kuindersma et al and Du Plessis et al using related technologies.

  2. Optical amplification in Er{sup 3+}-doped transparent Ba{sub 2}NaNb{sub 5}O{sub 15} single crystal at 850 nm

    SciTech Connect

    Haro-Gonzalez, P.; Martin, I. R.; Lahoz, F.; Gonzalez-Perez, S.; Cavalli, E.

    2009-12-01

    Positive optical gain around 5 cm{sup -1} (approx21 dB/cm) has been observed in Er{sup 3+}-doped Ba{sub 2}NaNb{sub 5}O{sub 15} single crystal using a pump and probe experimental setup. High power laser pulses at 532 nm have been used as the pump source in order to strongly populate the {sup 4}S{sub 3/2}({sup 2}H{sub 11/2}) levels of the Er{sup 3+} ions due to ground state absorption. Low signal beam cw laser radiation at 850 nm has been used as the probe beam to stimulate the emission associated with the {sup 4}S{sub 3/2}({sup 2}H{sub 11/2})->{sup 4}I{sub 13/2} electronic transition of the Er{sup 3+} ions. The process has been modelized as a four level system, and its population has been analyzed and simulated in order to study the gain dynamics. Optical amplification of the probe signal has been observed during the first 60 mus, which represents a good agreement between the measured lifetime of the {sup 4}S{sub 3/2}({sup 2}H{sub 11/2}) levels and the reported simulation.

  3. RF and Data Acquisition Systems for Fermilab's ILC SRF Cavity Vertical Test Stand

    SciTech Connect

    Joseph P. Ozelis; Roger Nehring; Christiana Grenoble; Thomas J. Powers

    2007-06-01

    Fermilab is developing a facility for vertical testing of SRF cavities as part of a program to improve cavity performance reproducibility for the ILC. The RF system for this facility, using the classic combination of oscillator, phase detector/mixer, and loop amplifier to detect the resonant cavity frequency and lock onto the cavity, is based on the proven production cavity test systems used at Jefferson Lab for CEBAF and SNS cavity testing. The design approach is modular in nature, using commercial-off-the-shelf (COTS) components. This yields a system that can be easily debugged and modified, and with ready availability of spares. Data acquisition and control is provided by a PXI-based hardware platform in conjunction with software developed in the LabView programming environment. This software provides for amplitude and phase adjustment of incident RF power, and measures all relevant cavity power levels, cavity thermal environment parameters, as well as field emission-produced radiation. It also calculates the various cavity performance parameters and their associated errors. Performance during system commissioning and initial cavity tests will be presented.

  4. 29 GHz directly modulated 980 nm vertical-cavity surface emitting lasers with bow-tie shape transverse coupled cavity

    NASA Astrophysics Data System (ADS)

    Dalir, Hamed; Koyama, Fumio

    2013-08-01

    A concept for the bandwidth enhancement of directly modulated vertical-cavity surface emitting lasers (VCSELs) using a transverse-coupled-cavity (TCC) scheme is proposed, which enables us to tailor the modulation-transfer function. A bow-tie shaped oxide aperture forms the transverse-coupled cavity resulting in optical feedback to boost the modulation speed. While the bandwidth of conventional VCSELs is 9-10 GHz, the 3 dB-bandwidth of the TCC VCSEL is increased by a factor of 3 far beyond the relaxation-oscillation frequency. The maximum bandwidth is currently limited by the photo-detector used in the experiment. Clear 36 Gbps eye opening was attained with an extinction ratio of 4 dB.

  5. Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy

    SciTech Connect

    Gargas, D.J.; Toimil-Molares, M.E.; Yang, P.

    2008-11-17

    We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal microscopy. In addition, three-dimensional (3D) mapping of the photoluminescence emission performed in both planar and vertical dimensions demonstrates height-selective imaging useful for vertical nanowires and heteronanostructures emerging in the field of optoelectronics and nanophotonics.

  6. The variable input coupler for the Fermilab Vertical Cavity Test Facility

    SciTech Connect

    Champion, Mark; Ginsburg, Camille M.; Lunin, Andrei; Moeller, Wolf-Dietrich; Nehring, Roger; Poloubotko, Valeri; /Fermilab

    2008-09-01

    A variable input coupler has been designed for the Fermilab vertical cavity test facility (VCTF), a facility for CW RF vertical testing of bare ILC 1.3 GHz 9-cell SRF cavities at 2K, to provide some flexibility in the test stand RF measurements. The variable coupler allows the cavity to be critically coupled for all RF tests, including all TM010 passband modes, which will simplify or make possible the measurement of those modes with very low end-cell fields, e.g., {pi}/9 mode. The variable coupler assembly mounts to the standard input coupler port on the cavity, and uses a cryogenic motor submerged in superfluid helium to control the antenna position. The RF and mechanical design and RF test results are described.

  7. RF and data acquisition systems for Fermilab's ILC SRF cavity vertical test stand

    SciTech Connect

    Ozelis, Joseph P.; Nehring, Roger; Grenoble, Christiana; Powers, Thomas J.; /Jefferson Lab

    2007-06-01

    Fermilab is developing a facility for vertical testing of SRF cavities as part of its ILC program. The RF system for this facility is based on the proven production cavity test systems used at Jefferson Lab for CEBAF and SNS cavity testing. The design approach is modular in nature, using commercial-off-the-shelf (COTS) components. This yields a system that can be easily debugged and modified, and with ready availability of spares. Comprehensive data acquisition and control is provided by a PXI-based hardware platform in conjunction with software developed in the LabView programming environment.

  8. Vertical-cavity saturable-absorber intensity modulator

    NASA Astrophysics Data System (ADS)

    Guina, M.; Vainionpää, A.; Harkonen, A.; Orsila, L.; Lyytikäinen, J.; Okhotnikov, O. G.

    2003-01-01

    We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture, that exploits the optical saturation of absorption in semiconductor quantum wells. The modulation section of the modulator, which is composed of quantum wells placed within a Fabry-Perot cavity, is optically controlled by an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer and grown in a single epitaxial step. The modulation section and the in-plane laser share the same medium; therefore, efficient coupling between the control beam and the signal beam is achieved. The device was successfully used for active mode locking of an erbium-doped fiber laser.

  9. Novel 980-nm and 490-nm light sources using vertical cavity lasers with extended coupled cavities

    NASA Astrophysics Data System (ADS)

    McInerney, John G.; Mooradian, Aram; Lewis, Alan; Shchegrov, Andrei V.; Strzelecka, Eva M.; Lee, Dicky; Watson, Jason P.; Liebman, Michael K.; Carey, Glen P.; Umbrasas, Arvydas; Amsden, Charles A.; Cantos, Brad D.; Hitchens, William R.; Heald, David L.; Doan, Vincent V.; Cannon, J. L.

    2003-04-01

    We have developed novel electrically pumped, surface-emitting lasers emitting at 980 nm with an extended coupled cavity. The concept is scalable from monolithic low power devices all the way to high power extended cavity lasers. The latter have demonstrated 1W cw multi-mode and 0.5 W cw in a TEM00 mode and a single frequency, with 90% coupling efficiency into a single-mode fiber. By inserting a nonlinear optical medium in the external cavity, efficient and compact frequency doubling has been achieved with CW output powers 5-40 mW demonstrated at 490 nm. The latter devices are especially noteworthy due to their very low noise, sub 10 μrad beam pointing stability combined with small size, low power consumption and high efficiency.

  10. Close to 100 Gbps discrete multitone transmission over 100m of multimode fiber using a single transverse mode 850nm VCSEL

    NASA Astrophysics Data System (ADS)

    Wu, Bo; Zhou, Xian; Ma, Yanan; Luo, Jun; Zhong, Kangping; Qiu, Shaofeng; Feng, Zhiyong; Luo, Yazhi; Agustin, Mikel; Ledentsov, Nikolay; Kropp, Joerg; Shchukin, Vitaly; Ledentsov, Nikolay N.; Eddie, Iain; Chao, Lu

    2016-03-01

    Discrete Multitone Transmission (DMT) transmission over standard multimode fiber (MMF) using high-speed single (SM) and multimode (MM) Vertical-Cavity Surface-Emitting Lasers (VCSELs) is studied. Transmission speed in the range of 72Gbps to 82Gbps over 300m -100m distances of OM4 fiber is realized, respectively, at Bit-Error-Ratio (BER) <5e-3 and the received optical power of only -5dBm. Such BER condition requires only 7% overhead for the conversion to error-free operation using single Bose-Chaudhuri-Hocquenghem forward error correction (BCH-FEC) coding and decoding. SM VCSEL is demonstrated to provide a much higher data transmission capacity over MMF. For 100m MMF transmission SM VCSEL allows 82Gbps as compared to MM VCSEL resulting in only 34Gbps at the same power (-5dBm). Furthermore, MM VCSEL link at 0dBm is still restricted at 100m distance by 63Gbps while SM VCSEL can exceed 100Gbps at such power levels. We believe that with further improvement in SM VCSELs and fiber coupling >100Gbps data transmission over >300m MMF distances at the BER levels matching the industry standards will become possible.

  11. Transverse Mode Structure and Pattern Formation in Oxide Confined Vertical Cavity Semiconductor Lasers

    SciTech Connect

    Choquette, K.D.; Geib, K.M.; Hegarty, S.P.; Hou, H.Q.; Huyet, G.; McInerney, J.G.; Porta, P.

    1999-07-06

    We analyze the transverse profiles of oxide-confined vertical cavity laser diodes as a function of aperture size. For small apertures we demonstrate that thermal lensing can be the dominant effect in determining the transverse resonator properties. We also analyze pattern formation in lasers with large apertures where we observe the appearance of tilted waves.

  12. Transverse Mode Dynamics and Ultrafast Modulation of Vertical-Cavity Surface-Emitting Lasers

    NASA Technical Reports Server (NTRS)

    Ning, Cun-Zheng; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    We show that multiple transverse mode dynamics of VCSELs (Vertical-Cavity Surface-Emitting Lasers) can be utilized to generate ultrafast intensity modulation at a frequency over 100 GHz, much higher than the relaxation oscillation frequency. Such multimode beating can be greatly enhanced by taking laser output from part of the output facet.

  13. Highly uniform and reproducible vertical-cavity surface emitting lasers grown by metalorganic chemical vapor deposition

    SciTech Connect

    Hou, H.Q.; Chui, H.C.; Choquette, K.D.; Hammons, B.E.; Breiland, W.G.; Geib, K.M.

    1996-01-01

    We show that the uniformity of the lasing wavelength of vertical-cavity surface emitting lasers (VCSELs) can be as good as {plus_minus}0.3% across a entire 3 in. wafer in MOCVD growth with a similar run-to-run reproducibility.

  14. Monolithic integration of vertical-cavity surface-emitting lasers with in-plane waveguides

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy; Scherer, Axel; Pickrell, Gregory; Louderback, Duane; Guilfoyle, Peter

    2005-03-01

    The ability to couple light from a vertical-cavity surface-emitting laser into a planar, on-chip waveguide creates new opportunities for achieving higher levels of integration and functionality. Here we propose to use a strong grating etched into a waveguide defined into the top layer of the epitaxially grown structure, so that epitaxial regrowth is not required. By introducing a defect mode into the cavity we were able to achieve a 40% coupling efficiency even though light is coupled through a ninety degrees bend. We also show that polarization control of the vertical-cavity surface-emitting laser is enhanced by coupling to the defect mode. Calculations were performed using the finite-difference time-domain method.

  15. The CAV program for numerical evaluation of laminar natural convection heat transfer in vertical rectangular cavities

    NASA Astrophysics Data System (ADS)

    Novak, Milos H.; Nowak, Edwin S.

    1993-12-01

    To analyze the laminar natural convection heat transfer and fluid flow distribution in vertical rectangular cavities with or without inner partitions, the personal computer finite difference program entitled CAV is used. The CAV program was tested successfully for slender cavities with aspect ratios as high as R = H/ L = 90 and for the Grashof numbers, based on the cavity height, up to GrH = 3 x10 9. To make the CAV program useful for a number of applications, various types of boundary conditions can also be imposed on the program calculations. Presented are program applications dealing with the 2-D numerical analysis of natural convection heat transfer in very slender window cavities with and without small inner partitions and recommendations are made for window design.

  16. Modeling of optically controlled reflective bistability in a vertical cavity semiconductor saturable absorber

    NASA Astrophysics Data System (ADS)

    Mishra, L.

    2015-05-01

    Bistability switching between two optical signals has been studied theoretically utilizing the concept of cross absorption modulation in a vertical cavity semiconductor saturable absorber (VCSSA). The probe beam is fixed at a wavelength other than the low power cavity resonance wavelength, which exhibits bistable characteristic by controlling the power of a pump beam (λpump≠λprobe). The cavity nonlinear effects that arises simultaneously from the excitonic absorption bleaching, and the carrier induced nonlinear index change has been considered in the model. The high power absorption in the active region introduces thermal effects within the nonlinear cavity due to which the effective cavity length changes. This leads to a red-shift of the cavity resonance wavelength, which results a change in phase of the optical fields within the cavity. In the simulation, the phase-change due to this resonance shifting is considered to be constant over time, and it assumes the value corresponding to the maximum input power. Further, an initial phase detuning of the probe beam has been considered to investigate its effect on switching. It is observed from the simulated results that, the output of the probe beam exhibits either clockwise or counter-clockwise bistability, depending on its initial phase detuning.

  17. Method for accurate growth of vertical-cavity surface-emitting lasers

    DOEpatents

    Chalmers, S.A.; Killeen, K.P.; Lear, K.L.

    1995-03-14

    The authors report a method for accurate growth of vertical-cavity surface-emitting lasers (VCSELs). The method uses a single reflectivity spectrum measurement to determine the structure of the partially completed VCSEL at a critical point of growth. This information, along with the extracted growth rates, allows imprecisions in growth parameters to be compensated for during growth of the remaining structure, which can then be completed with very accurate critical dimensions. Using this method, they can now routinely grow lasing VCSELs with Fabry-Perot cavity resonance wavelengths controlled to within 0.5%. 4 figs.

  18. Method for accurate growth of vertical-cavity surface-emitting lasers

    DOEpatents

    Chalmers, Scott A.; Killeen, Kevin P.; Lear, Kevin L.

    1995-01-01

    We report a method for accurate growth of vertical-cavity surface-emitting lasers (VCSELs). The method uses a single reflectivity spectrum measurement to determine the structure of the partially completed VCSEL at a critical point of growth. This information, along with the extracted growth rates, allows imprecisions in growth parameters to be compensated for during growth of the remaining structure, which can then be completed with very accurate critical dimensions. Using this method, we can now routinely grow lasing VCSELs with Fabry-Perot cavity resonance wavelengths controlled to within 0.5%.

  19. CONTROL OF LASER RADIATION PARAMETERS: Conditions for two-frequency lasing in coupled-cavity vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Logginov, Aleksandr S.; Rzhanov, A. G.; Skorov, D. V.

    2007-06-01

    A self-consistent model of a semiconductor coup-led-cavity vertical-cavity surface-emitting laser is presented. The electromagnetic field distribution in the laser is found by the effective-frequency method. The dynamic model is constructed on coupled rate equations for two active cavities. Dynamic, threshold and spectral parameters of the laser are studied. The applicability of the model is confirmed by the good agreement with the experimental data available in the literature.

  20. Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

    NASA Astrophysics Data System (ADS)

    Jin, S.; Wu, A. T.; Lu, X. Y.; Rimmer, R. A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

    2013-09-01

    This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I-V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson-Superfish and Solidworks respectively. With the optimal cathode shape, BEP shows a much faster polishing rate of ∼2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

  1. Effect of cathode shape on vertical buffered electropolishing for niobium SRF cavities

    SciTech Connect

    Jin, S.; Wu, A. T.; Lu, X. Y.; Rimmer, R. A.; Lin, L.; Zhao, K.; Mammosser, J.; Gao, J.

    2013-09-01

    This paper reports the research results of the effect of cathode shape during vertical buffered electropolishing (BEP) by employing a demountable single cell niobium (Nb) superconducting radio frequency (SRF) cavity. Several different cathode shapes such as, for instance, bar, ball, ellipsoid, and wheels of different diameters have been tested. Detailed electropolishing parameters including I–V characteristic, removal rate, surface roughness, and polishing uniformity at different locations inside the demountable cavity are measured. Similar studies are also done on conventional electropolishing (EP) for comparison. It is revealed that cathode shape has dominant effects for BEP especially on the obtaining of a suitable polishing condition and a uniform polishing rate in an Nb SRF single cell cavity. EP appears to have the same tendency. This paper demonstrates that a more homogeneous polishing result can be obtained by optimizing the electric field distribution inside the cavity through the modification of the cathode shape given the conditions that temperature and electrolyte flow are kept constant. Electric field distribution and electrolyte flow patterns inside the cavity are simulated via Poisson–Superfish and Solidworks respectively. Finally, with the optimal cathode shape, BEP shows a much faster polishing rate of ~2.5 μm/min and is able to produce a smoother surface finish in the treatments of single cell cavities in comparison with EP.

  2. Integration of diffractive lenses with addressable vertical-cavity laser arrays

    SciTech Connect

    Warren, M.E.; Du, T.C.; Wendt, J.R.; Vawter, G.A.; Carson, R.F.; Lear, K.L.; Kilcoyne, S.P.; Schneider, R.P.; Zolper, J.C.

    1995-04-01

    An optical interconnection system is being developed to provide vertical, digital data channels for stacked multichip modules. A key component of the system is an array of individually addressable vertical-cavity surface-emitting lasers with diffractive lenses integrated into the substrate to control beam divergence and direction. The lenses were fabricated by direct-write e-beam lithography and reactive ion beam etching into the GaAs substrate. Preliminary device performance data and the design and fabrication issues are discussed.

  3. Effective index model predicts modal frequencies of vertical-cavity lasers

    SciTech Connect

    SERKLAND,DARWIN K.; HADLEY,G. RONALD; CHOQUETTE,KENT D.; GEIB,KENT M.; ALLERMAN,ANDREW A.

    2000-04-18

    Previously, an effective index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. The authors show that the resultant transverse equation is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. The solution to the transverse equation yields the lateral dependence of the optical field and, as is recognized in this paper, the discrete frequencies of the microcavity modes. As an example, they apply this technique to the analysis of vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains the experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

  4. Synchronization of chaotic outputs in multi-transverse-mode vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lin, Hong; Valles, Matthew M.; Zhang, Yu

    2013-11-01

    We have experimentally explored synchronization of chaotic outputs in unidirectionally coupled vertical-cavity surface-emitting lasers in the multi-transverse mode regime. The beam from the transmitter is orthogonally injected into the receiver. High cross correlation between the injection and the Y polarization of the receiver can be achieved for appropriate frequency detuning and injection power. The modal property in synchronization is examined as well.

  5. Monolithic excitation and manipulation of surface plasmon polaritons on a vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Lamy, J.-M.; Justice, J.; Lévêque, G.; Corbett, B.

    2011-06-01

    We report the manipulation of surface plasmon polaritons (SPPs) on a thin Au layer integrated on top of the mirror of a vertical-cavity surface-emitting laser (VCSEL). Gratings etched into the Au layer to different depths are used to couple the light into and out of the film, and to bend the trajectory of the SPP. The result paves the way to compact integrated plasmonic devices.

  6. Bistable laser device with multiple coupled active vertical-cavity resonators

    DOEpatents

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-08-19

    A new class of bistable coupled-resonator vertical-cavity semiconductor laser devices has been developed. These bistable laser devices can be switched, either electrically or optically, between lasing and non-lasing states. A switching signal with a power of a fraction of a milliwatt can change the laser output of such a device by a factor of a hundred, thereby enabling a range of optical switching and data encoding applications.

  7. Polarization switching and polarization mode hopping in quantum dot vertical-cavity surface-emitting lasers.

    PubMed

    Olejniczak, Lukasz; Panajotov, Krassimir; Thienpont, Hugo; Sciamanna, Marc; Mutig, Alex; Hopfer, Friedhelm; Bimberg, Dieter

    2011-01-31

    We show experimentally that polarization mode hopping in quantum dot vertical cavity surface emitting lasers (VCSELs) takes place between nonorthogonal elliptically polarized modes. In contrast to quantum well VCSELs the average dwell time decreases with injection current. This decrease is by 8 orders of magnitude: from seconds to nanoseconds and is achieved without any modifications of the VCSEL internal anisotropies. The observed scaling happens in a range of currents as wide as 8 times the threshold value.

  8. Delayed feedback control of cavity solitons in a broad area vertical cavity surface emitting laser with saturable absorbtion

    NASA Astrophysics Data System (ADS)

    Gurevich, S. V.; Schelte, C.; Tlidi, M.; Panajotov, K.

    2016-04-01

    We are interested in spatio-temporal dynamics of cavity solitons (CSs) in a transverse section of a broad area vertical cavity surface emitting laser (VCSEL) with saturable absorbtion subjected to time-delayed optical feedback. In the absence of delayed feedback, a single branch of localized solutions appears in the parameter space. However, in the presence of the delayed feedback, multistability of CS solutions emerges; The branches of CSs fill the surface of the "solution tube" in the parameter space, which is filled densely with increasing delay time. Further, our study reveals that the multistability of stationary solutions is caused by a delayed-induced phase bifurcation of CSs. Furthermore, it was shown that stability properties of CSs strongly depend on the delayed feedback parameters. In particular, the thresholds of the drift and phase bifurcations as well as corresponding bifurcation diagrams are obtained by a combination of analytical and numerical continuation methods. It turns out that both thresholds tend to zero in the limit of large delay times. In addition, we demonstrate that the presence of the delayed optical feedback can induce Andronov-Hopf bifurcation and a period doubling route to chaos. Moreover, a coupling between this bifurcation scenario with aforementioned delay-induced multistability leads to a complex spatio-temporal behavior of the system in question. The results of analytical bifurcation analysis are in agreement with those obtained by direct numerical integration of the model equation.

  9. Stability Analysis of Natural Convection in Vertical Cavities with Lateral Heating

    NASA Astrophysics Data System (ADS)

    Yahata, Hideo

    1999-02-01

    Thermal convection of air in two-dimensional vertical cavities is considered under the boundary conditions of the left and right vertical walls kept at different temperatures and the top and bottom horizontal walls subject to thermal insulation. Linear stability analysis of thermal convection is made with the aid of the Galerkin method in which the field variables are expanded in terms of Chebyshev polynomials and linear growth rates of steady states are computed using the QR algorithm.The results of the stability analysis for air with the Prandtl number 0.71 over the range of the cavity aspect ratio A from 1 to 10 show that with increase of the temperature difference between the two vertical walls the oscillatory motion first generated by the instability of steady convection is in the form of the Tollmien-Schlichting or the internal gravity waves according as A > 3.65 or A < 3.41 while for 3.41 < A < 3.65 the internal gravity waves are first generated after the preceding spatial flow transition of the hydraulic jump.

  10. Femtosecond synchronously mode-locked vertical-external cavity surface-emitting laser.

    PubMed

    Zhang, Wei; Ackemann, Thorsten; Schmid, Marc; Langford, Nigel; Ferguson, Allister

    2006-03-06

    The behavior of a room temperature synchronously mode-locked vertical-external cavity surface-emitting laser (VECSEL) operating at 980 nm is reported. The laser performance was found to be qualitatively the same for different pump pulse duration (3.6 ps and 70 fs). The pulse duration of the laser is limited by strong self-phase modulation to around 10-40 ps. By compressing the strongly chirped pulses generated directly from the laser, ultrashort pulses with duration of around 200 fs with maximum peak powers of 1.3 kW at 80 MHz were obtained. Multiple pulsing of the laser was observed and the effects of cavity length detuning on pulse width and spectral bandwidth have been investigated.

  11. Controllable spiking patterns in long-wavelength vertical cavity surface emitting lasers for neuromorphic photonics systems

    SciTech Connect

    Hurtado, Antonio; Javaloyes, Julien

    2015-12-14

    Multiple controllable spiking patterns are achieved in a 1310 nm Vertical-Cavity Surface Emitting Laser (VCSEL) in response to induced perturbations and for two different cases of polarized optical injection, namely, parallel and orthogonal. Furthermore, reproducible spiking responses are demonstrated experimentally at sub-nanosecond speed resolution and with a controlled number of spikes fired. This work opens therefore exciting research avenues for the use of VCSELs in ultrafast neuromorphic photonic systems for non-traditional computing applications, such as all-optical binary-to-spiking format conversion and spiking information encoding.

  12. Investigation of vertical cavity surface emitting laser dynamics for neuromorphic photonic systems

    NASA Astrophysics Data System (ADS)

    Hurtado, A.; Schires, K.; Henning, I. D.; Adams, M. J.

    2012-03-01

    We report an approach based upon vertical cavity surface emitting lasers (VCSELs) to reproduce optically different behaviors exhibited by biological neurons but on a much faster timescale. The technique proposed is based on the polarization switching and nonlinear dynamics induced in a single VCSEL under polarized optical injection. The particular attributes of VCSELs and the simple experimental configuration used in this work offer prospects of fast, reconfigurable processing elements with excellent fan-out and scaling potentials for use in future computational paradigms and artificial neural networks.

  13. Degradation studies of proton-implanted vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Y. Michael; Herrick, Robert W.; Petroff, Pierre M.; Hibbs-Brenner, Mary K.; Morgan, Robert A.

    1995-09-01

    We analyze the degradation process of proton-implanted, top-emitting vertical cavity surface emitting lasers using cross-sectional cathodoluminescence. The spatially resolved luminescence characteristics of the active regions, and p- and n-distributed Bragg reflector (DBR) mirrors before and after degradation of the devices are presented. Degradation has been observed not only in the active regions, but also remarkably in the p-DBR mirror stacks. We show that a significant minority carrier population is present in the p mirror under normal operating conditions to drive the degradation observed in the p mirror.

  14. 1300 nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Alharthi, S. S.; Orchard, J.; Clarke, E.; Henning, I. D.; Adams, M. J.

    2015-10-01

    We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3 μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11 mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization.

  15. Optimisation of fundamental transverse mode output in electrically pumped vertical external cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Jin, Xiao; Ivanov, Pavlo; Childs, David T. D.; Babazadeh, Nasser; Orchard, John; Stevens, Benjamin J.; Hogg, Richard A.

    2015-03-01

    In this work we report on the simulation of electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). We simulate an etched mesa structure (substrate emission) with the substrate acting as the current spreading layer. The effect of contact misalignment on the carrier distribution within the active element is explored and confirms the validity of the model in describing the carrier distribution. We go on to discuss the effects of the substrate thickness and trench depth on the intensity profile. Simulation results show that a thicker substrate and a trench partially etched into the substrate may improve the intensity profile in future devices.

  16. Design and characterization of electrically pumped vertical external cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Orchard, J. R.; Childs, D. T. D.; Lin, L. C.; Stevens, B. J.; Williams, D. M.; Hogg, R. A.

    2011-03-01

    The design of electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs) for high power applications require a number of optimisations in design trade-offs, mainly that of doping for improved electrical performance and optical loss. Devices with diameter greater than 70μm and current spreading layer thickness of 100μm suffer from non-uniform carrier injection into the active region, below this diameter output power scales linearly with device area. We show CW powers of 133mW from a 150μm device with 4x1017cm-3 substrate doping at 0°C can be obtained.

  17. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Liu, W. J.; Hu, X. L.; Ying, L. Y.; Chen, S. Q.; Zhang, J. Y.; Akiyama, H.; Cai, Z. P.; Zhang, B. P.

    2015-04-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400 nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355 nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355 nm pulsed laser. These were explained by taking into account of the significant heating effect under 355 nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs.

  18. Optical Phased Array Antennas using Coupled Vertical Cavity Surface Emitting Lasers

    NASA Technical Reports Server (NTRS)

    Mueller, Carl H.; Rojas, Roberto A.; Nessel, James A.; Miranda, Felix A.

    2007-01-01

    High data rate communication links are needed to meet the needs of NASA as well as other organizations to develop space-based optical communication systems. These systems must be robust to high radiation environments, reliable, and operate over a wide temperature range. Highly desirable features include beam steering capability, reconfigurability, low power consumption, and small aperture size. Optical communication links, using coupled vertical cavity surface emitting laser radiating elements are promising candidates for the transmit portion of these communication links. In this talk we describe a mission scenario, and how the antenna requirements are derived from the mission needs. We describe a potential architecture for this type of antenna, and outline the advantages and drawbacks of this approach relative to competing technologies. The technology we are proposing used coupled arrays of 1550 nm vertical cavity surface emitting lasers for transmission. The feasibility of coupling these arrays together, to form coherent high-power beams that can be modulated at data rates exceeding 1 Gbps, will be explored. We will propose an architecture that enables electronic beam steering, thus mitigating the need for ancillary acquisition, tracking and beam pointing equipment such as needed for current optical communicatin systems. The beam-steering capability we are proposing also opens the possibility of using this technology for inter-satellite communicatin links, and satellite-to-surface links.

  19. Temperature-insensitive vertical-cavity surface-emitting lasers and method for fabrication thereof

    DOEpatents

    Chow, Weng W.; Choquette, Kent D.; Gourley, Paul L.

    1998-01-01

    A temperature-insensitive vertical-cavity surface-emitting laser (VCSEL) and method for fabrication thereof. The temperature-insensitive VCSEL comprises a quantum-well active region within a resonant cavity, the active region having a gain spectrum with a high-order subband (n.gtoreq.2) contribution thereto for broadening and flattening the gain spectrum, thereby substantially reducing any variation in operating characteristics of the VCSEL over a temperature range of interest. The method for forming the temperature-insensitive VCSEL comprises the steps of providing a substrate and forming a plurality of layers thereon for providing first and second distributed Bragg reflector (DBR) mirror stacks with an active region sandwiched therebetween, the active region including at least one quantum-well layer providing a gain spectrum having a high-order subband (n.gtoreq.2) gain contribution, and the DBR mirror stacks having predetermined layer compositions and thicknesses for providing a cavity resonance within a predetermined wavelength range substantially overlapping the gain spectrum.

  20. Temperature-insensitive vertical-cavity surface-emitting lasers and method for fabrication thereof

    DOEpatents

    Chow, W.W.; Choquette, K.D.; Gourley, P.L.

    1998-01-27

    A temperature-insensitive vertical-cavity surface-emitting laser (VCSEL) and method for fabrication thereof are disclosed. The temperature-insensitive VCSEL comprises a quantum-well active region within a resonant cavity, the active region having a gain spectrum with a high-order subband (n {>=} 2) contribution thereto for broadening and flattening the gain spectrum, thereby substantially reducing any variation in operating characteristics of the VCSEL over a temperature range of interest. The method for forming the temperature-insensitive VCSEL comprises the steps of providing a substrate and forming a plurality of layers thereon for providing first and second distributed Bragg reflector (DBR) mirror stacks with an active region sandwiched therebetween, the active region including at least one quantum-well layer providing a gain spectrum having a high-order subband (n {>=} 2) gain contribution, and the DBR mirror stacks having predetermined layer compositions and thicknesses for providing a cavity resonance within a predetermined wavelength range substantially overlapping the gain spectrum. 12 figs.

  1. Vertical cavity lasing from melt-grown crystals of cyano-substituted thiophene/phenylene co-oligomer

    NASA Astrophysics Data System (ADS)

    Tanaka, Yosuke; Goto, Kaname; Yamashita, Kenichi; Yamao, Takeshi; Hotta, Shu; Sasaki, Fumio; Yanagi, Hisao

    2015-10-01

    Vertical-cavity organic lasers are fabricated with melt-grown crystals of a cyano-substituted thiophene-phenylene co-oligomer. Due to lying molecular orientation, surface-emitting lasing is achieved even in the half-cavity crystal grown on a distributed Bragg reflector (DBR) under optical pumping at room temperature. Anticrossing splits in angle-resolved photoluminescence spectra suggest the formation of exciton-polaritons between the cavity photons and the confined Frenkel excitons. By constructing the full-cavity structure sandwiched between the top and bottom DBRs, the lasing threshold is reduced to one order, which is as low as that of the half cavity. Around the threshold, the time profile of the full-cavity emission is collapsed to a pulsed shape accompanied by a finite turn-on delay. We discuss these observed characteristics in terms of a polariton contribution to the conventional photon lasing.

  2. Vertical cavity lasing from melt-grown crystals of cyano-substituted thiophene/phenylene co-oligomer

    SciTech Connect

    Tanaka, Yosuke; Yanagi, Hisao; Goto, Kaname; Yamashita, Kenichi; Yamao, Takeshi; Hotta, Shu; Sasaki, Fumio

    2015-10-19

    Vertical-cavity organic lasers are fabricated with melt-grown crystals of a cyano-substituted thiophene-phenylene co-oligomer. Due to lying molecular orientation, surface-emitting lasing is achieved even in the half-cavity crystal grown on a distributed Bragg reflector (DBR) under optical pumping at room temperature. Anticrossing splits in angle-resolved photoluminescence spectra suggest the formation of exciton-polaritons between the cavity photons and the confined Frenkel excitons. By constructing the full-cavity structure sandwiched between the top and bottom DBRs, the lasing threshold is reduced to one order, which is as low as that of the half cavity. Around the threshold, the time profile of the full-cavity emission is collapsed to a pulsed shape accompanied by a finite turn-on delay. We discuss these observed characteristics in terms of a polariton contribution to the conventional photon lasing.

  3. Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy

    SciTech Connect

    Hou, Hong Q.; Coltrin, Michael E.; Choquette, Kent D.

    2001-01-01

    A process for forming an array of vertical cavity optical resonant structures wherein the structures in the array have different detection or emission wavelengths. The process uses selective area growth (SAG) in conjunction with annular masks of differing dimensions to control the thickness and chemical composition of the materials in the optical cavities in conjunction with a metalorganic vapor phase epitaxy (MOVPE) process to build these arrays.

  4. Frequency-doubled vertical-external-cavity surface-emitting laser

    DOEpatents

    Raymond, Thomas D.; Alford, William J.; Crawford, Mary H.; Allerman, Andrew A.

    2002-01-01

    A frequency-doubled semiconductor vertical-external-cavity surface-emitting laser (VECSEL) is disclosed for generating light at a wavelength in the range of 300-550 nanometers. The VECSEL includes a semiconductor multi-quantum-well active region that is electrically or optically pumped to generate lasing at a fundamental wavelength in the range of 600-1100 nanometers. An intracavity nonlinear frequency-doubling crystal then converts the fundamental lasing into a second-harmonic output beam. With optical pumping with 330 milliWatts from a semiconductor diode pump laser, about 5 milliWatts or more of blue light can be generated at 490 nm. The device has applications for high-density optical data storage and retrieval, laser printing, optical image projection, chemical-sensing, materials processing and optical metrology.

  5. Selective oxidation of buried AlGaAs for fabrication of vertical-cavity lasers

    SciTech Connect

    Choquette, K.D.; Geib, K.M.; Chui, H.C.; Hou, H.Q.; Hull, R.

    1996-06-01

    The authors discuss the selective conversion of buried layers of AlGaAs to a stable oxide and the implementation of this oxide into high performance vertical-cavity surface emitting lasers (VCSELs). The rate of lateral oxidation is shown to be linear with an Arrhenius temperature dependence. The measured activation energies vary with Al composition, providing a high degree of oxidation selectivity between AlGaAs alloys. Thus buried oxide layers can be selectively fabricated within the VCSEL through small compositional variations in the AlGaAs layers. The oxidation of AlGaAs alloys, as opposed to AlAs, is found to provide robust processing of reliable lasers. The insulating and low refractive index oxide provides enhanced electrical and optical confinement for ultralow threshold currents in oxide-apertured VCSELs.

  6. All-optical flip-flop based on vertical cavity semiconductor optical amplifiers.

    PubMed

    Song, Deqiang; Gauss, Veronica; Zhang, Haijiang; Gross, Matthias; Wen, Pengyue; Esener, Sadik

    2007-10-15

    We report the operation of an all-optical set-reset (SR) flip-flop based on vertical cavity semiconductor optical amplifiers (VCSOAs). This flip-flop is cascadable, has low optical switching power (~10 microW), and has the potential to be integrated on a small footprint (~100 microm(2)). The flip-flop is composed of two cross-coupled electrically pumped VCSOA inverters and uses the principles of cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics to achieve flip-flop functionality. We believe that, when integrated on chip, this type of all-optical flip-flop opens new prospects for implementing all-optical fast memories and timing regeneration circuits.

  7. Flow patterns of natural convection in an air-filled vertical cavity

    NASA Astrophysics Data System (ADS)

    Wakitani, Shunichi

    1998-08-01

    Flow patterns of two-dimensional natural convection in a vertical air-filled tall cavity with differentially heated sidewalls are investigated. Numerical simulations based on a finite difference method are carried out for a wide range of Rayleigh numbers and aspect ratios from the onset of the steady multicellular flow, through the reverse transition to the unicellular pattern, to the unsteady multicellular flow. For aspect ratios (height/width) from 10 to 24, the various cellular structures characterized by the number of secondary cells are clarified from the simulations by means of gradually increasing Rayleigh number to 106. Unsteady multicellular solutions are found in some region of Rayleigh numbers less than those at which the reverse transition has occurred.

  8. Commercial manufacturing of vertical-cavity surface-emitting laser arrays

    NASA Astrophysics Data System (ADS)

    Swirhun, Stan E.; Bryan, Robert P.; Fu, Winston S.; Quinn, William E.; Jewell, Jack L.; Olbright, Greg R.

    1994-06-01

    Optoelectronic integrated circuits based on arrays of vertical- cavity surface emitting lasers (VCSELs) are evolving into functional chips enhancing the performance of fiber optic networks, optical data storage, laser printing and scanning, visual displays, and optoelectronic computing and other systems. This evolution involves the development of advanced manufacturing technology germane to packaged arrays of VCSELs comprising micro- optic lens arrays and interface electronics. In this paper we describe Photonics Research's LASE-ARRAY commercial manufacturing efforts. Specifically we will discuss commercial manufacturing advancements in molecular beam epitaxial growth, full-wafer processing, interface electronics, microoptic lens arrays, packaging and implementation of statistical process control. Yield and reliability will also be discussed. Last we discuss emerging applications for the LASE-ARRAY technology.

  9. Matrices of 960-nm vertical-cavity surface-emitting lasers

    SciTech Connect

    Maleev, N. A.; Kuzmenkov, A. G.; Shulenkov, A. S.; Blokhin, S. A.; Kulagina, M. M.; Zadiranov, Yu. M.; Tikhomirov, V. G.; Gladyshev, A. G.; Nadtochiy, A. M.; Nikitina, E. V.; Lott, J. A.; Svede-Shvets, V. N.; Ledentsov, N. N.; Ustinov, V. M.

    2011-06-15

    Matrices of vertical-cavity surface-emitting lasers with individual addressing of elements and radiation output through a gallium arsenide substrate are implemented. Individual laser emitters with a current aperture diameter of 6-7 {mu}m exhibit continuous-wave room-temperature lasing at a wavelength of 958-962 nm with threshold currents of 1.1-1.3 mA, differential efficiency of 0.5-0.8 mW/mA, and a maximum output power of 7.5-9 mW. The parameter variation of individual emitters within a matrix chip containing 5 Multiplication-Sign 7 elements does not exceed {+-}20%.

  10. Densely Packed 2-D Matrix-Addressable Vertical-Cavity Surface-Emitting Laser Arrays

    NASA Astrophysics Data System (ADS)

    Gadallah, Abdel-Sattar; Michalzik, Rainer

    2013-03-01

    We report on design, manufacturing, and characterization of densely packed top-emitting 16 × 16 elements wire-bonded matrix-addressable vertical-cavity surface-emitting laser (VCSEL) arrays, which may find future applications such as non-mechanical particle movement with optical multi-tweezers, confocal microscopy or free-space communications with beam steering capability. The factors that control the packing density such as layer structure, mask design, and VCSEL processing are investigated, aiming to minimize the pitch between VCSELs in the array. Both wet-etched and dry-etched arrays are presented and discussed. The single transverse mode VCSELs in the two-dimensional (2-D) matrix-addressable architecture have threshold currents which vary from 0.5 to 1.6 mA and maximum output powers between 2.4 and 4 mW. A simple analysis of the parasitic ohmic resistances is made.

  11. Cascadable all-optical inverter based on a nonlinear vertical-cavity semiconductor optical amplifier.

    PubMed

    Zhang, Haijiang; Wen, Pengyue; Esener, Sadik

    2007-07-01

    We report, for the first time to our knowledge, the operation of a cascadable, low-optical-switching-power(~10 microW) small-area (~100 microm(2)) high-speed (80 ps fall time) all-optical inverter. This inverter employs cross-gain modulation, polarization gain anisotropy, and highly nonlinear gain characteristics of an electrically pumped vertical-cavity semiconductor optical amplifier (VCSOA). The measured transfer characteristics of such an optical inverter resemble those of standard electronic metal-oxide semiconductor field-effect transistor-based inverters exhibiting high noise margin and high extinction ratio (~9.3 dB), making VCSOAs an ideal building block for all-optical logic and memory.

  12. Ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting laser devices

    NASA Astrophysics Data System (ADS)

    Gerhardt, N. C.; Li, M.; Jaehme, H.; Soldat, H.; Hofmann, M. R.; Ackemann, T.

    2010-02-01

    Spin-polarized lasers offer new encouraging possibilities for future devices. We investigate the polarization dynamics of electrically pumped vertical-cavity surface-emitting lasers after additional spin injection at room temperature. We find that the circular polarization degree exhibits faster dynamics than the emitted light. Moreover the experimental results demonstrate a strongly damped ultrafast circular polarization oscillation due to spin injection with an oscillation frequency of approximately 11GHz depending on the birefringence in the VCSEL device. We compare our experimental results with theoretical calculations based on rate-equations. This allows us to predict undamped long persisting ultrafast polarization oscillations, which reveal the potential of spin-VCSELs for ultrafast modulation applications.

  13. Spin induced gigahertz polarization oscillations in vertical-cavity surface-emitting laser devices

    NASA Astrophysics Data System (ADS)

    Li, M. Y.; Jaehme, H.; Soldat, H.; Gerhardt, N. C.; Hofmann, M. R.; Ackemann, T.

    2011-03-01

    Spin-controlled vertical-cavity surface-emitting lasers (VCSELs) have been intensively studied in recent years because of the low threshold feasibility and the nonlinearity above threshold, which make spin-VCSELs very promising for spintronic devices. Here we investigate the circular polarization dynamics of VCSELs on a picosecond time scale after pulsed optical spin injection at room temperature. A hybrid excitation technique combining continuous-wave (cw) unpolarized electrical excitation slightly above threshold and pulsed polarized optical excitation is applied. The experimental results demonstrate ultrafast circular polarization oscillations with a frequency of about 11 GHz. The oscillations last inside the first undulation of the intensity relaxation oscillations. Via theoretical calculations based on a rate equation model we analyze these oscillations as well as the underlying physical mechanisms.

  14. 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-μm-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%.

  15. Design Rules and Characterisation of Electrically Pumped Vertical External Cavity Surface Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Orchard, Jonathan R.; Childs, David T. D.; Chih Lin, Li; Stevens, Ben J.; Williams, David M.; Hogg, Richard A.

    2011-04-01

    We present an experimental study of the effect of substrate doping on the operating characteristics of substrate emitting electrically pumped vertical external cavity surface emitting lasers. We demonstrate a reduction in substrate doping from 2×1018 to 4×1017 cm-3 leads to reduced optical loss and enhanced current-gain characteristics. Spatial carrier distributions, evidenced by near field profiling of devices without external feedback indicates essentially identical behavior for the two substrate dopings. Devices with diameter greater than 100 µm and current spreading layer thickness of 100 µm suffer from non-uniform carrier injection into the active region, below this diameter output power scales linearly with device diameter. We show CW powers of 130 mW from a 100 µm device with 4×1017 cm-3 substrate doping at 0 °C can be obtained.

  16. Evolution of multi-mode operation in vertical-external-cavity surface-emitting lasers.

    PubMed

    Wichmann, Matthias; Shakfa, Mohammad Khaled; Zhang, Fan; Heinen, Bernd; Scheller, Maik; Rahimi-Iman, Arash; Stolz, Wolfgang; Moloney, Jerome V; Koch, Stephan W; Koch, Martin

    2013-12-30

    The longitudinal multi-mode emission in a vertical-external-cavity surface-emitting laser is investigated using both single shot streak camera measurements and interferometric measurement techniques. For this, the laser is operated in the single- and two-color emission regime using both an etalon and a free-running configuration without etalon, respectively. The laser emission is analyzed with respect to pump power and output coupling losses for a long and for a short resonator. We observe a steep increase of emission bandwidth close to the laser threshold and monitor the transition between longitudinal single- and multi-mode operation. Additionally, the results indicate that a stable two-color operation is related to a sufficiently high number of oscillating longitudinal modes within each color.

  17. Characterization of vertical-cavity surface-emitting laser structures by modulation spectroscopy: A status report

    NASA Astrophysics Data System (ADS)

    Klar, P. J.; Karcher, C.; Metzger, B.; Hosea, T. J. C.

    2005-05-01

    The present issue of physica status solidi (a) contains contributions from the International Workshop on Modulation Spectroscopy of Semiconductor Structures (MS3), held in Wrocaw, Poland, 1-3 July 2004.Editor's Choice is the article by P. J. Klar et al. [1] in which the advantages of these techniques are used to characterize optoelectronic devices. For a vertical-cavity surface-emitting laser structure (shown schematically in the lower part) to operate, the emission wavelength qw of its active region and the cavity mode at cav of its resonator structure need to coincide. The photomodulated reflectance spectrum (upper left part, bottom) shows clear features at both wavelengths whereas a feature at qw cannot be distinguished in the corresponding reflectance spectrum (top) due to its complicated photonic nature.The first author, Peter J. Klar is currently a lecturer of Physics at the Philipps-University of Marburg, Germany. His research interests include the physics of magnetic semiconductors and hybrids for spintronics, of III-N-V semiconductor structures for optoelectronics, and of novel nanostructures ranging from nanomagnetism to applications in catalysis.

  18. Comparative analysis of energy-efficient long wavebands vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Dahiya, Sandeep; Mishra, Hemant Kumar; Kumar, Suresh; Kaushik, Brajesh Kumar

    2016-10-01

    Vertical cavity surface emitting laser (VCSEL) is an important laser source for their evident plentiful applications in optical communication. The present investigation reports a comparison of the modeling and optimization of long wavelengths 1310 nm and 1550 nm high speed short cavity VCSEL for continuous wave operation at various temperature (283-3230K) for various diameters. The continuous wave lasing is demonstrated for the device diameter from 2 to 5 μm with threshold current of 1.07-1.33 mA with threshold power consumption of 1.86-2.57 mW for 1310 nm and threshold current of 0.94-1.24 mA and threshold power consumption 1.67-2.1 mW for 1550 nm VCSEL. The results demonstrate that the threshold current, peak emitted power and power consumption increases with the increase in device diameter. The results confirm that VCSELs with 2 μm diameter is most suitable to achieve energy-efficient operation. Although rollover current increases with the diameter, but, due to the advantage of lower threshold current and power consumption, VCSEL having smaller diameter is best suited. The power conversion efficiency for proposed long wavelength VCSELs is approximately 50% which is extremely useful for low power applications. The proposed VCSELs are suitable for very short reach (<2 m) optical interconnects such as chip-to-chip and board-to-board communication in high performance computers.

  19. Experimental evidence of single round-trip oscillation in polarization self-modulated vertical-cavity surface emitting lasers

    SciTech Connect

    Ropars, G.; Langot, P.; Brunel, M.; Vallet, M.; Bretenaker, F.; Le Floch, A.; Choquette, K.D.

    1997-05-01

    The polarizations and frequencies of the two eigenstates of a vertical cavity surface emitting laser with an external cavity containing a quarter-wave plate are theoretically and experimentally analyzed. It is shown that the polarizations of these eigenstates are fixed by the neutral axes of the quarter-wave plate. The optical pulses at a frequency equal to a half of the free spectral range of the external cavity, observed through a linear polarizer, are due to beats between the two eigenstates. All these features show that such polarization self-modulated lasers oscillate in a single round trip. {copyright} {ital 1997 American Institute of Physics.}

  20. High reflectivity III-nitride UV-C distributed Bragg reflectors for vertical cavity emitting lasers

    NASA Astrophysics Data System (ADS)

    Franke, A.; Hoffmann, M. P.; Kirste, R.; Bobea, M.; Tweedie, J.; Kaess, F.; Gerhold, M.; Collazo, R.; Sitar, Z.

    2016-10-01

    UV-C distributed Bragg reflectors (DBRs) for vertical cavity surface emitting laser applications and polariton lasers are presented. The structural integrity of up to 25 layer pairs of AlN/Al0.65Ga0.35N DBRs is maintained by balancing the tensile and compressive strain present between the single layers of the multilayer stack grown on top of an Al0.85Ga0.35N template. By comparing the structural and optical properties for DBRs grown on low dislocation density AlN and AlGaN templates, the criteria for plastic relaxation by cracking thick nitride Bragg reflectors are deduced. The critical thickness is found to be limited mainly by the accumulated strain energy during the DBR growth and is only negligibly affected by the dislocations. A reflectance of 97.7% at 273 nm is demonstrated. The demonstrated optical quality and an ability to tune the resonance wavelength of our resonators and microcavity structures open new opportunities for UV-C vertical emitters.

  1. Room temperature continuous wave InGaAsN quantum well vertical cavity lasers emitting at 1.3 um

    SciTech Connect

    CHOQUETTE,KENT D.; KLEM,JOHN F.; FISCHER,ARTHUR J.; SPAHN,OLGA B.; ALLERMAN,ANDREW A.; FRITZ,IAN J.; KURTZ,STEVEN R.; BREILAND,WILLIAM G.; SIEG,ROBERT M.; GEIB,KENT M.; SCOTT,J.W.; NAONE,R.L.

    2000-06-05

    Selectively oxidized vertical cavity lasers emitting at 1294 nm using InGaAsN quantum wells are reported for the first time which operate continuous wave at and above room temperature. The lasers employ two n-type Al{sub 0.94}Ga{sub 0.06}As/GaAs distributed Bragg reflectors each with a selectively oxidized current aperture adjacent to the optical cavity, and the top output mirror contains a tunnel junction to inject holes into the active region. Continuous wave single mode lasing is observed up to 55 C. These lasers exhibit the longest wavelength reported to date for vertical cavity surface emitting lasers grown on GaAs substrates.

  2. Polarization dynamics in spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Gerhardt, Nils C.; Höpfner, Henning; Lindemann, Markus; Hofmann, Martin R.

    2014-08-01

    Spin-polarized lasers and especially spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) are at- tractive novel spintronic devices providing functionalities and characteristics superior to their conventional purely charge-based counterparts. This applies in particular to ultrafast dynamics, modulation capability and chirp control of directly modulated lasers. Here we demonstrate that ultrafast oscillations of the circular polarization degree can be generated in VCSELs by pulsed spin injection which have the potential to reach frequencies beyond 100 GHz. These oscillations are due to the coupling of the carrier-spin-photon system via the optical birefringence for the linearly polarized laser modes in the micro-cavity and are principally decoupled from conventional relaxation oscillations of the carrier-photon system. Utilizing these polarization oscillations is a very promising path to ultrafast directly modulated spin-VCSELs in the near future as long as an effective concept can be developed to modulate or switch these polarization oscillations. After briefly reviewing the state of research in the emerging field of spin-VCSELs, we present a novel concept for controlled switching of polarization oscillations by use of multiple optical spin injection pulses. Depending on the amplitude and phase conditions of the excitation pulses, constructive or destructive interference of polarization oscillations leads to an excitation, stabilization or switch-off of these oscillations. Furthermore even short single polarization bursts can be generated with pulse widths only limited by the resonance frequency of the polarization oscillation. Consequently, this concept is an important building block for using spin controlled polarization oscillations for future communication applications.

  3. On the importance of cavity-length and heat dissipation in GaN-based vertical-cavity surface-emitting lasers

    PubMed Central

    Liu, W. J.; Hu, X. L.; Ying, L. Y.; Chen, S. Q.; Zhang, J. Y.; Akiyama, H.; Cai, Z. P.; Zhang, B. P.

    2015-01-01

    Cavity-length dependence of the property of optically pumped GaN-based vertical-cavity surface-emitting lasers (VCSELs) with two dielectric distributed Bragg reflectors was investigated. The cavity lengths were well controlled by employing etching with inductively coupled plasma and chemical mechanical polishing. It was found that the lasing characteristics including threshold, slope efficiency and spontaneous emission coupling factor were substantially improved with reducing the cavity length. In comparison with the device pumped by a 400 nm pulsed laser, the lasing spectrum was featured by a red shift and simultaneous broadening with increasing the pumping energy of a 355 nm pulsed laser. Moreover, the lasing threshold was much higher when pumped by a 355 nm pulsed laser. These were explained by taking into account of the significant heating effect under 355 nm pumping. Our results demonstrate that a short cavity length and good heat-dissipation are essential to GaN-based VCSELs. PMID:25873327

  4. Novel 980-nm and 490-nm light sources using vertical-cavity lasers with extended coupled cavities

    NASA Astrophysics Data System (ADS)

    McInerney, John G.; Mooradian, Aram; Lewis, Alan; Shchegrov, Andrei V.; Strzelecka, Eva M.; Lee, Dicky; Watson, Jason P.; Liebman, Michael K.; Carey, Glen P.; Umbrasas, Arvydas; Amsden, Charles A.; Cantos, Brad D.; Hitchens, William R.; Heald, David L.; Doan, Vincent

    2003-06-01

    We have developed novel electrically pumped, surface-emitting lasers emitting at 980 nm with an extended coupled cavity. The concept is scalable from monolithic low power (~10 mW) devices all the way to high power extended cavity lasers. The latter have demonstrated ~1 W cw multi-mode and 0.5 W cw in a TEM00 mode and a single frequency, with 90% coupling efficiency into a single-mode fiber. By inserting a nonlinear optical medium in the external cavity, efficient and compact frequency doubling has been achieved with CW output powers 5-40 mW demonstrated at 490 nm. The latter devices are especially noteworthy due to their very low noise (0.05% rms from dc-2 MHz), sub 10 mrad beam pointing stability combined with small size, low power consumption (<10 W) and high efficiency.

  5. Phase-locked arrays of vertical-cavity surface-emitting lasers

    SciTech Connect

    Warren, M.E.; Hadley, G.R.; Lear, K.L.; Gourley, P.L.; Vawter, G.A.; Zolper, J.C.; Brennan, T.M.; Hammons, B.E.

    1994-05-01

    Vertical Cavity Surface-Emitting Lasers (VCSELs) are of increasing interest to the photonics community because of their surface-emitting structure, simple fabrication and packaging, wafer-level testability and potential for low cost. Scaling VCSELs to higher power outputs requires increasing the device area, which leads to transverse mode control difficulties if devices become larger than 10-15 microns. One approach to increasing the device size while maintaining a well controlled transverse mode profile is to form coupled or phase-locked, two-dimensional arrays of VCSELs that are individually single-transverse mode. The authors have fabricated and characterized both photopumped and electrically injected two-dimensional VCSEL arrays with apertures over 100 microns wide. Their work has led to an increased understanding of these devices and they have developed new types of devices, including hybrid semiconductor/dielectric mirror VCSEL arrays, VCSEL arrays with etched trench, self-aligned, gold grid contacts and arrays with integrated phase-shifters to correct the far-field pattern.

  6. Integrated plasmonic circuitry on a vertical-cavity surface-emitting semiconductor laser platform

    NASA Astrophysics Data System (ADS)

    McPolin, Cillian P. T.; Bouillard, Jean-Sebastien; Vilain, Sebastien; Krasavin, Alexey V.; Dickson, Wayne; O'Connor, Daniel; Wurtz, Gregory A.; Justice, John; Corbett, Brian; Zayats, Anatoly V.

    2016-08-01

    Integrated plasmonic sources and detectors are imperative in the practical development of plasmonic circuitry for bio- and chemical sensing, nanoscale optical information processing, as well as transducers for high-density optical data storage. Here we show that vertical-cavity surface-emitting lasers (VCSELs) can be employed as an on-chip, electrically pumped source or detector of plasmonic signals, when operated in forward or reverse bias, respectively. To this end, we experimentally demonstrate surface plasmon polariton excitation, waveguiding, frequency conversion and detection on a VCSEL-based plasmonic platform. The coupling efficiency of the VCSEL emission to waveguided surface plasmon polariton modes has been optimized using asymmetric plasmonic nanostructures. The plasmonic VCSEL platform validated here is a viable solution for practical realizations of plasmonic functionalities for various applications, such as those requiring sub-wavelength field confinement, refractive index sensitivity or optical near-field transduction with electrically driven sources, thus enabling the realization of on-chip optical communication and lab-on-a-chip devices.

  7. Integrated plasmonic circuitry on a vertical-cavity surface-emitting semiconductor laser platform

    PubMed Central

    McPolin, Cillian P. T.; Bouillard, Jean-Sebastien; Vilain, Sebastien; Krasavin, Alexey V.; Dickson, Wayne; O'Connor, Daniel; Wurtz, Gregory A.; Justice, John; Corbett, Brian; Zayats, Anatoly V.

    2016-01-01

    Integrated plasmonic sources and detectors are imperative in the practical development of plasmonic circuitry for bio- and chemical sensing, nanoscale optical information processing, as well as transducers for high-density optical data storage. Here we show that vertical-cavity surface-emitting lasers (VCSELs) can be employed as an on-chip, electrically pumped source or detector of plasmonic signals, when operated in forward or reverse bias, respectively. To this end, we experimentally demonstrate surface plasmon polariton excitation, waveguiding, frequency conversion and detection on a VCSEL-based plasmonic platform. The coupling efficiency of the VCSEL emission to waveguided surface plasmon polariton modes has been optimized using asymmetric plasmonic nanostructures. The plasmonic VCSEL platform validated here is a viable solution for practical realizations of plasmonic functionalities for various applications, such as those requiring sub-wavelength field confinement, refractive index sensitivity or optical near-field transduction with electrically driven sources, thus enabling the realization of on-chip optical communication and lab-on-a-chip devices. PMID:27491686

  8. Towards monolithic integration of mode-locked vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Aldaz, Rafael I.

    2007-12-01

    The speed and performance of today's high end computing and communications systems have placed difficult but still feasible demands on off-chip electrical interconnects. However, future interconnect systems may need aggregate bandwidths well into the terahertz range thereby making electrical bandwidth, density, and power targets impossible to meet. Optical interconnects, and specifically compact semiconductor mode-locked lasers, could alleviate this problem by providing short pulses in time at 10s of GHz repetition rates for Optical Time Division Multiplexing (OTDM) and clock distribution applications. Furthermore, the characteristic spectral comb of frequencies of these lasers could also serve as a multi-wavelength source for Wavelength Division Multiplexing (WDM) applications. A fully integrated mode-locked Vertical Cavity Surface Emitting Laser (VCSEL) is proposed as a low-cost high-speed source for these applications. The fundamental laser platform for such a device has been developed and a continuous-wave version of these lasers has been fabricated and demonstrated excellent results. Output powers close to 60mW have been obtained with very high beam quality factor of M2 < 1.07. The mode-locked laser utilizes a passive mode-locking region provided by a semiconductor saturable absorber integrated together with the gain region. Such an aggressive integration forces the resonant beam in the cavity to have the same area on the gain and absorber sections, placing high demands on the saturation fluence and absorption coefficient for the saturable absorber. Quantum Wells (QWs), excitons in QWs and Quantum Dots (QDs) have been investigated as possible saturable absorbers for the proposed device. QDs have been found to have the lowest saturation fluence and total absorption, necessary to meet the mode-locking requirements for this configuration. The need to further understand QDs as saturable absorbers has led to the development of a theoretical model on the dynamics of

  9. Intra-cavity cryogenic optical refrigeration using high power vertical external-cavity surface-emitting lasers (VECSELs).

    PubMed

    Ghasemkhani, Mohammadreza; Albrecht, Alexander R; Melgaard, Seth D; Seletskiy, Denis V; Cederberg, Jeffrey G; Sheik-Bahae, Mansoor

    2014-06-30

    A 7% Yb:YLF crystal is laser cooled to 131 ± 1 K from room temperature by placing it inside the external cavity of a high power InGaAs/GaAs VECSEL operating at 1020 nm with 0.15 nm linewidth. This is the lowest temperature achieved in the intracavity geometry to date and presents major progress towards realizing an all-solid-state compact optical cryocooler.

  10. Spectral condensation near molecular transitions in intracavity laser spectroscopy with vertical external cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Bertseva, Elena; Campargue, Alain

    2004-03-01

    Vertical external cavity surface emitting lasers (VeCSELs) are ideal amplification media for intracavity laser absorption spectroscopy (ICLAS) around 1 μm. However, we noted that, in some spectra recorded by ICLAS-VeCSEL, the observed line profiles of very weak overtone transitions were clearly asymmetric, this distortion being more pronounced for the strongest lines. More spectacular effects were observed when we investigated the acetylene spectrum: while the weakest absorption lines appeared as dips superimposed on the baseline as usual in ICLAS, the strongest lines mostly disappeared and were replaced by emission lines slightly blue shifted from the absorption line center. This effect, called "spectral condensation", was, in fact, discovered near atomic transitions, more than 30 years ago, using pulsed lasers. Using acetylene and water as absorbers, we have systematically studied the different factors of importance for spectral condensation and showed that it increases with the pumping rate, the generation time and the line intensity. Spectral condensation was also found to increase with the pressure of the intracavity gas sample up to a value of a few Torrs, and to decrease afterwards. The appearance of spectral condensation has been shown to be highly correlated to time oscillations of the total laser power. Of importance for intensity measurements, this systematic study has showed that condensation effects may appear for long generation times even at low pumping rate and even with extremely weak absorption lines. A discussion of the results in relation with different interpretations available in the literature is presented with a particular emphasis on the theory based on the coherent interaction of electro-magnetic field with optically dense resonant extended medium leading to a parametrical amplification without population inversion.

  11. Proton damage effects on GaAs/GaAlAs vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Le Metayer, P.; Gilard, O.; Germanicus, R.; Campillo, D.; Ledu, F.; Cazes, J.; Falo, W.; Chatry, C.

    2003-12-01

    A series of proton irradiations of GaAs/GaAlAs vertical cavity surface emitting lasers (VCSELs) has been carried out for the purpose of assessing the suitability of these devices for space applications. The irradiations were performed on biased and unbiased devices at energies of 30, 40, 50, and 60 MeV. Both current versus voltage (I-V) and optical power versus current (P-I) characteristics were measured before and after each irradiation phase. A simple circuit equivalent model for the VCSEL has been developed to analyze proton damage effects through the extraction of electrical parameters. The current threshold of VCSEL is shown to be the only important parameter modified by a high fluence (up to 1012 protons/cm2) irradiation. Changes in the threshold current show radiation generated recombination centers to be the main cause of degradation. Due to carrier injection annealing related effects, we observed that unbiased devices show the greatest relative threshold increase (between 15% and 20% at 1013 protons/cm2). The threshold current damage factor was also calculated. The analysis of the I-V characteristics shows that in the range of low fluences (1010-1012 protons/cm2) radiation induced ordering effects may compete with the usual radiation degradation that we observed at higher fluences. Consequently, the nonionizing energy loss approach, which is extensively used to predict the degradation of electronic devices under a full spectrum of energetic particles, is deemed to be not yet applicable for prediction of end-of-life performances of VCSELs.

  12. Impact of strain on periodic gain structures in vertical external cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Jasik, Agata; Sokół, Adam Kacper; Broda, Artur; Sankowska, Iwona; Wójcik-Jedlińska, Anna; Wasiak, Michał; Trajnerowicz, Artur; Kubacka-Traczyk, Justyna; Muszalski, Jan

    2016-10-01

    In this article, the impact of strain relaxation on the emission properties of InGaAs/GaAs multiple quantum wells without strain compensation was examined. Structures consisting of different numbers of quantum wells, namely 4, 8, 12 and 16, on top of distributed Bragg reflectors were grown by molecular beam epitaxy as a typical vertical external cavity surface-emitting laser (VECSEL). The relation between emission parameters in the lasing regime and strain relaxation were investigated. A two-step control of the growth rate allowed for obtaining fixed spectral detuning in all structures regardless of the number of quantum wells. The heterostructures varied in its strain and the microcavity length. The other parameters remained unchanged. In consequence, for the first time a unique set of VECSEL-like heterostructures was investigated. The strain was analyzed by reciprocal space mapping using high-resolution X-ray diffractometry. It was found that the degree of structure relaxation caused by misfit dislocation generation depends linearly on the number of quantum wells. By fitting numerical simulations to the experimental results, we have quantitatively determined the extent to which output power was suppressed by increase in non-radiative recombination arising from misfit dislocations. The non-radiative coefficients were determined. Taking output power as a criterion, we determined the optimal number of QWs to be 12 and the maximum tolerable relaxation value of 0.27 for InGaAs/GaAs VECSEL structures with uniformly distributed quantum wells in microcavity. The dependence of the monomolecular recombination coefficient on structure relaxation has been determined.

  13. Optical Injection Locking of Vertical Cavity Surface-Emitting Lasers: Digital and Analog Applications

    NASA Astrophysics Data System (ADS)

    Parekh, Devang

    With the rise of mobile (cellphones, tablets, notebooks, etc.) and broadband wireline communications (Fiber to the Home), there are increasing demands being placed on transmitters for moving data from device to device and around the world. Digital and analog fiber-optic communications have been the key technology to meet this challenge, ushering in ubiquitous Internet and cable TV over the past 20 years. At the physical layer, high-volume low-cost manufacturing of semiconductor optoelectronic devices has played an integral role in allowing for deployment of high-speed communication links. In particular, vertical cavity surface emitting lasers (VCSEL) have revolutionized short reach communications and are poised to enter more markets due to their low cost, small size, and performance. However, VCSELs have disadvantages such as limited modulation performance and large frequency chirp which limits fiber transmission speed and distance, key parameters for many fiber-optic communication systems. Optical injection locking is one method to overcome these limitations without re-engineering the VCSEL at the device level. By locking the frequency and phase of the VCSEL by the direct injection of light from another laser oscillator, improved device performance is achieved in a post-fabrication method. In this dissertation, optical injection locking of VCSELs is investigated from an applications perspective. Optical injection locking of VCSELs can be used as a pathway to reduce complexity, cost, and size of both digital and analog fiber-optic communications. On the digital front, reduction of frequency chirp via bit pattern inversion for large-signal modulation is experimentally demonstrated showing up to 10 times reduction in frequency chirp and over 90 times increase in fiber transmission distance. Based on these results, a new reflection-based interferometric model for optical injection locking was established to explain this phenomenon. On the analog side, the resonance

  14. Vertical cavity surface emitting laser emitting at 1.56 microns with AlGaAsSb/AlAsSb distributed Bragg reflectors

    SciTech Connect

    Blum, O.; Klem, J.F.; Lear, K.L.; Vawter, G.A.; Kurtz, S.R.

    1998-07-01

    The authors report 77K operation of an optically pumped vertical cavity surface emitting laser with an Sb-based cavity. The structure consists of 15 and 20 pair AlGaAsSb/AlAsSb top and bottom reflectors and a bulk InGaAs active region.

  15. Phase dynamics in vertical-cavity surface-emitting lasers with delayed optical feedback and cross-polarized reinjection

    NASA Astrophysics Data System (ADS)

    Javaloyes, J.; Marconi, M.; Giudici, M.

    2014-08-01

    We study theoretically the nonlinear polarization dynamics of vertical-cavity surface-emitting lasers in the presence of an external cavity providing delayed optical feedback and cross-polarized reinjection. We show that, far from the laser threshold, the dynamics remains confined close to the equatorial plane of a Poincaré sphere with a fixed radius. It entails that the evolution of the system is described by two phase variables: the orientation phase of the quasilinear polarization and the optical phase of the field. We explore the complex modal structure given by the double reinjection configuration and how it evolves between the cases of single cross-polarized reinjection and single optical feedback, hence disclosing the relationship with the Lang-Kobayashi model. We also reinterpret the square-wave switching observed by J. Mulet et al. [Phys. Rev. A 76, 043801 (2007), 10.1103/PhysRevA.76.043801] in terms of phase kinks.

  16. Steady-state characteristics of lateral p-n junction vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Ryzhii, V.; Tsutsui, N.; Khmyrova, I.; Ikegami, T.; Vaccaro, P. O.; Taniyama, H.; Aida, T.

    2001-09-01

    We developed an analytical device model for lateral p-n junction vertical-cavity surface-emitting lasers (LJVCSELs) with a quantum well active region. The model takes into account the features of the carrier injection, transport, and recombination in LJVCSELs as well as the features of the photon propagation in the cavity. This model is used for the calculation and analysis of the LJVCSEL steady-state characteristics. It is shown that the localization of the injected electrons primarily near the p-n junction and the reabsorption of lateral propagating photons significantly effects the LJVCSELs performance, in particular, the LJVCSEL threshold current and power-current characteristics. The reincarnation of electrons and holes due to the reabsorption of lateral propagating photons can substantially decrease the threshold current.

  17. Long-wavelength vertical-cavity surface-emitting lasers with selectively etched thin apertures

    NASA Astrophysics Data System (ADS)

    Feezell, Daniel F.

    Long-wavelength vertical-cavity surface-emitting lasers (VCSELs) emitting in the 1300--1600nm wavelength window are attractive light sources for short to mid-range optical fiber communications. These devices target low-loss and low-dispersion minima in standard optical fibers and are expected to provide a low-cost alternative to the existing edge-emitting infrastructure. With low-power consumption, on wafer testing; simple packaging, and high fiber-coupling efficiency, VCSELs are ideal transmitters for CWDM, metro, local area, and storage area networks. Recently, much attention has been devoted to a rich variety of approaches to long-wavelength VCSELs. One underlying problem, however, has been the need to match a reliable high-gain active region with high-index-contrast distributed Bragg reflectors (DBRs) over the full 1300--1600nm wavelength range. One solution to this problem is to utilize well-established InAlGaAs active-region technology coupled with AlGaAsSb DBRs. This combination facilitates monolithic all-epitaxial InP-based devices spanning the entire 1300--1600nm wavelength range. Previously, Dr. Shigeru Nakagawa and Dr. Eric Hall have demonstrated long-wavelength VCSELs with Sb-based technology operating at 1550nm. This dissertation demonstrates the first high-performance InP-based VCSELs with Sb-based DBRs operating at 1310nm, thus solidifying Sb-based technology as a wavelength flexible platform for long-wavelength devices. Also developed is a novel and efficient tunnel-junction aperturing technology for generating extremely low-loss optical and electrical confinement. Lastly, it is shown that the benefits from such an aperturing scheme produce marked improvements in device operation versus previously demonstrated Sb-based VCSELs. The devices from this research generated over 1.6mW single-mode continuous-wave (CW) output power at room temperature (>2mW multi-mode), displayed threshold currents down to 1mA, and operated CW up to 90°C. Furthermore, world

  18. Controlled switching of ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Höpfner, Henning; Lindemann, Markus; Gerhardt, Nils C.; Hofmann, Martin R.

    2014-01-01

    We demonstrate a scheme for controlled switching of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers (spin-VCSEL). Under hybrid electrical and optical pumping conditions, our VCSEL devices show polarization oscillations with frequencies far above the VCSEL's electrical modulation bandwidth. Using multiple optical pulses, we are able to excite and amplify these polarization oscillations. When specific phase and amplitude conditions for the optical excitation pulses are met, destructive interference leads to switch-off of the polarization oscillation, enabling the generation of controlled short polarization bursts.

  19. Frequency scanning interferometry with nanometer precision using a vertical-cavity surface-emitting laser diode under scanning speed control

    NASA Astrophysics Data System (ADS)

    Kakuma, Seiichi

    2015-12-01

    Frequency scanning interferometry technique with a nanometer precision using a vertical-cavity surface-emitting laser diode (VCSEL) is presented. Since the frequency scanning of the VCSEL is linearized by the phase-locked-loop technique, the gradient of the interference fringe order can be precisely determined using linear least squares fitting. This enables a length measurement with a precision better than a quarter wavelength, and the absolute fringe number including the integer part at the atomic transition spectrum (rubidium-D2 line) is accurately determined. The validity of the method is demonstrated by excellent results of block gauge measurement with a root mean square error better than 5 nm.

  20. Characteristics of polarization switching from the low to the high frequency mode in vertical-cavity surface-emitting lasers

    SciTech Connect

    Ackemann, T.; Sondermann, M.

    2001-06-04

    Polarization selection in small-area vertical-cavity surface-emitting lasers is studied experimentally in dependence of injection current and substrate temperature in the vicinity of the minimum threshold condition. Polarization switching from the low to the high frequency fundamental spatial mode is demonstrated. The effective birefringence displays a minimum in the transition region. The observation of dynamical transition states hints to the relevance of nonlinear effects. A comparison to the predictions of the San Miguel{endash}Feng{endash}Moloney model based on phase-amplitude coupling is given. {copyright} 2001 American Institute of Physics.

  1. Parallel self-mixing imaging system based on an array of vertical-cavity surface-emitting lasers

    SciTech Connect

    Tucker, John R.; Baque, Johnathon L.; Lim, Yah Leng; Zvyagin, Andrei V.; Rakic, Aleksandar D

    2007-09-01

    In this paper we investigate the feasibility of a massively parallel self-mixing imaging system based on an array of vertical-cavity surface-emitting lasers (VCSELs) to measure surface profiles of displacement,distance, velocity, and liquid flow rate. The concept of the system is demonstrated using a prototype to measure the velocity at different radial points on a rotating disk, and the velocity profile of diluted milk in a custom built diverging-converging planar flow channel. It is envisaged that a scaled up version of the parallel self-mixing imaging system will enable real-time surface profiling, vibrometry, and flowmetry.

  2. Controlled switching of ultrafast circular polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers

    SciTech Connect

    Höpfner, Henning Lindemann, Markus; Gerhardt, Nils C.; Hofmann, Martin R.

    2014-01-13

    We demonstrate a scheme for controlled switching of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers (spin-VCSEL). Under hybrid electrical and optical pumping conditions, our VCSEL devices show polarization oscillations with frequencies far above the VCSEL's electrical modulation bandwidth. Using multiple optical pulses, we are able to excite and amplify these polarization oscillations. When specific phase and amplitude conditions for the optical excitation pulses are met, destructive interference leads to switch-off of the polarization oscillation, enabling the generation of controlled short polarization bursts.

  3. 1300 nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

    SciTech Connect

    Alharthi, S. S. Henning, I. D.; Adams, M. J.; Orchard, J.; Clarke, E.

    2015-10-12

    We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3 μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11 mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization.

  4. Analysis of Multi-Polarization Switching in Vertical-Cavity Surface-Emitting Lasers Using Multi-peak gain model

    NASA Astrophysics Data System (ADS)

    Hsu, Chuan; Chen, Yu-Fong; Chin, Pei-Hou; Quadir, Shaham; Li, Yueh-Chen; Wu, Yu-Heng; Yen, Tsu-Chiang

    2013-03-01

    This research investigated the mulit-polarization switching (MPS) in vertical-cavity surface-emitting lasers (VCSELs) at constant temperature by simple multi-peak gain model.In experimental results, the phenomenon of the polarization switching (PS) in the VCSEL were arduous to definite quantitative analysis. A simple multi-peak gain model which included the temperature effect and current effect was established to match the MPS in the VCSEL. Simulation results match the experimental results well and shoe that the variation of temperature is a affecting factor of MPS. Therefore, the simple multi-peak gain model contributed a good understanding of multi-polarization switching in VCSELs.

  5. Fabrication and characterization of the Si-photonics-integrated vertical resonant-cavity light-emitting diode

    NASA Astrophysics Data System (ADS)

    Kong, Duanhua; Kim, Taek; Kim, Sihan; Hong, Hyungi; Shcherbatko, Igor; Park, Youngsoo; Shin, Dongjae; Ha, Kyoung-Ho; Jeong, Gitae

    2014-03-01

    We designed and fabricated a 1.3-um hybrid vertical Resonant-Cavity Light-Emitting Diode for optical interconnect by using direct III-V wafer bonding on silicon on insulator (SOI). The device included InP based front distributed Bragg reflector (DBR), InGaAlAs based active layer, and SOI-based high-contrast-grating (HCG) as a back reflector. 42-uW continuous wave optical power was achieved at 20mA at room temperature.

  6. Rapid multiexposure in vivo brain imaging system using vertical cavity surface emitting lasers as a light source.

    PubMed

    Atchia, Yaaseen; Levy, Hart; Dufour, Suzie; Levi, Ofer

    2013-03-01

    We demonstrate an imaging technique implementing vertical cavity lasers with extremely low transient times for a greatly simplified realization of a multiexposure laser speckle contrast imaging system. Data from multiexposure laser speckle imaging was observed to more closely agree with absolute velocity measurements using time of flight technique, when compared to long-exposure laser speckle imaging. Furthermore, additional depth information of the vasculature morphology was inferred by accounting for the change in the static scattering from tissue above vessels with respect to the total scattering from blood flow and tissue.

  7. Development of vertical external cavity surface emitting lasers (VECSELs) for use as monochromatic and polychromatic sodium guidestars

    NASA Astrophysics Data System (ADS)

    Hackett, Shawn; Albrecht, Alexander R.; Yang, Zhou; Cederberg, Jeffrey G.; Sheik-Bahae, Mansoor; McGraw, John T.; Johnson, Robert L.; Richey, Jeff W.

    2016-07-01

    The work of Pique showed that multiple guidestars emitting at 1140 nm and 589 nm simultaneously could be utilized to correct for Tip and Tilt aberrations [1]. Such a guidestar is hence known as a PLGS (Polychromatic Laser Guidestar). However, no current high power (> 5W) narrow bandwidth (< 1GHz) exist for 1140 nm emission. A Vertical External Cavity Surface Emitting Laser (VECSEL) is shown with high power > 12W and narrow bandwidth emission which has been successfully used to pump the sodium 3P3/2 to 4S1/2 sodium transition as a testbed for the development of a CW PLGS system.

  8. GaN-based vertical-cavity laser performance improvements using tunnel-junction-cascaded active regions

    SciTech Connect

    Piprek, Joachim

    2014-07-07

    This Letter investigates the output power enhancement achieved by tunnel junction insertion into the InGaN multi-quantum well (MQW) active region of a 410 nm vertical-cavity surface-emitting laser which enables the repeated use of carriers for light generation (carrier recycling). While the number of quantum wells remains unchanged, the tunnel junction eliminates absorption caused by the non-uniform MQW carrier distribution. The thermal resistance drops and the excess bias lead to a surprisingly small rise in self-heating.

  9. Progress in GaInNAs/GaAs long-wavelength vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Larson, Michael C.; Kondow, Masahiko; Kitatani, Takeshi; Nakahara, Kouji; Tamura, K.; Yazawa, Yoshiaki; Okai, Makoto O.; Inoue, Hiroaki; Uomi, Kazuhisa

    1998-04-01

    GaInNAs is a novel laser diode active layer material which holds great promise for low-cost optical fiber transmission applications requiring emission wavelengths near 1.3 micrometers . GaInNAs permits the realization of a long-wavelength vertical-cavity laser grown directly on a GaAs substrate. Continuous-wave room-temperature photo-pumped laser oscillation has been demonstrated in vertical cavity laser designs employing single or multiple GaInNAs quantum wells, with lasing wavelengths as long as 1.256 micrometers . Electrically-injected devices have achieved pulsed operation at room temperature and above, with a minimum threshold current density of 3.1 kA/cm2, slope efficiency above 0.04 W/A, and output power above 5 mW for 45 micrometers -diameter devices. Threshold current has exhibited minimal dependence on temperature from 20 degrees C to 60 degrees C, and laser oscillation is observed for temperatures as high as 95 degrees C.

  10. Lateral carrier confinement of GaN-based vertical-cavity surface-emitting diodes using boron ion implantation

    NASA Astrophysics Data System (ADS)

    Hamaguchi, Tatsushi; Nakajima, Hiroshi; Ito, Masamichi; Mitomo, Jugo; Satou, Susumu; Fuutagawa, Noriyuki; Narui, Hironobu

    2016-12-01

    Boron ion implantation, which is used for confining carriers in gallium nitride (GaN)-based vertical-cavity surface-emitting laser diodes (VCSELs), was studied. Detailed analysis indicated that boron ion implantation of GaN increases GaN’s absorption coefficient from zero to 800 cm-1 and its refractive index from 2.45 to 2.51 at the surface of the wafer at a wavelength of 453 nm. The depth profile of boron obtained by secondary ion mass spectroscopy (SIMS) showed an exponential decrease toward the bottom of the wafer. Assuming that the changes in optical parameters caused by implantation are proportional to the concentration of boron in GaN, the boron ion implantation applied to GaN-VCSELs causes optical absorption of 0.04% per round trip in the cavity and extends the light path of the cavity by 2.2 nm, both of which apparently have negligible impact on the operation of GaN-VCSELs. The implanted boron ions pass through the active regions, introducing non-radiative recombination centers at the edges of those active regions made of InGaN multi-quantum wells, which, however, does not cause significant current injection loss.

  11. Temperature stable mid-infrared GaInAsSb/GaSb Vertical Cavity Surface Emitting Lasers (VCSELs)

    NASA Astrophysics Data System (ADS)

    Ikyo, A. B.; Marko, I. P.; Hild, K.; Adams, A. R.; Arafin, S.; Amann, M.-C.; Sweeney, S. J.

    2016-01-01

    GaInAsSb/GaSb based quantum well vertical cavity surface emitting lasers (VCSELs) operating in mid-infrared spectral range between 2 and 3 micrometres are of great importance for low cost gas monitoring applications. This paper discusses the efficiency and temperature sensitivity of the VCSELs emitting at 2.6 μm and the processes that must be controlled to provide temperature stable operation. We show that non-radiative Auger recombination dominates the threshold current and limits the device performance at room temperature. Critically, we demonstrate that the combined influence of non-radiative recombination and gain peak – cavity mode de-tuning determines the overall temperature sensitivity of the VCSELs. The results show that improved temperature stable operation around room temperature can only be achieved with a larger gain peak – cavity mode de-tuning, offsetting the significant effect of increasing non-radiative recombination with increasing temperature, a physical effect which must be accounted for in mid-infrared VCSEL design.

  12. Numerical investigation of the aerodynamic performance for the newly designed cavity vane type vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Suffer, K. H.; Usubamatov, R.; Quadir, G. A.; Ismail, K. A.

    2015-05-01

    Research and development activities in the field of renewable energy, especially wind and solar, have been considerably increased, due to the worldwide energy crisis and high global emission. However, the available technical designs are not yet adequate to develop a reliable distributed wind energy converter for low wind speed conditions. The last few years have proved that Vertical Axis Wind Turbines (VAWTs) are more suitable for urban areas than Horizontal Axis Wind Turbines (HAWTs). To date, very little has been published in this area to assess good performance and lifetime of VAWTs either in open or urban areas. The power generated by vertical axis wind turbines is strongly dependent on the aerodynamic performance of the turbines. The main goal of this current research is to investigate numerically the aerodynamic performance of a newly designed cavity type vertical axis wind turbine. In the current new design the power generated depends on the drag force generated by the individual blades and interactions between them in a rotating configuration. For numerical investigation, commercially available computational fluid dynamic (CFD) software GAMBIT and FLUENT were used. In this numerical analysis the Shear Stress Transport (SST) k-ω turbulence model is used which is better than the other turbulence models available as suggested by some researchers. The computed results show good agreement with published experimental results.

  13. Design and Characterization of Optically Pumped Vertical Cavity Surface Emitting Lasers

    DTIC Science & Technology

    1992-12-01

    3-7 3.4. Bottom Mirror Reflectivity as seen in GaAs Spacer ...... ........... 3-8 3.5. Top Mirror (22 layers) Reflectivity as...seen from GaAs Cavity Spacer 3-10 3.6. Fabry-Perot Effect in Designed 950 nm VCSEL .................... 3-11 3.7. Gain Guiding and Index Guiding in VCSEL...affected by the desired gain for the region, the absorption of the spacer and the active regions, the lasing wavelength, and lattice matching

  14. Membrane Reflector Vertical Cavity Lasers at Near- and Midwave-Infrared

    DTIC Science & Technology

    2014-05-30

    Mingyu Lu, Huiqing Zhai, Deyin Zhao, Weidong Zhou. Design of a compact grating coupler with controllable linewidths via transverse resonance and...H. Zhai, D. Zhao, W. D. Zhou and Z. Ma, “Design of a compact grating coupler with controllable linewidths via transverse resonance and evanescent...Francisco, CA. 51. A. Chadha, Y. Shuai, and W. Zhou, “High Performance Second-Order Surface-Normal Vertical to In-plane Optical Coupler ”, Photonics West

  15. Development of a high-power vertical-cavity surface-emitting laser array with ion-implanted current apertures

    NASA Astrophysics Data System (ADS)

    Naito, Hideyuki; Miyamoto, Masahiro; Aoki, Yuta; Higuchi, Akira; Torii, Kousuke; Nagakura, Takehito; Morita, Takenori; Maeda, Junya; Miyajima, Hirofumi; Yoshida, Harumasa

    2013-03-01

    Vertical-Cavity Surface-Emitting Lasers (VCSELs) are very attractive to high power light sources owing to the advantageous configuration of two-dimensional arrays and being free from catastrophic optical damage. Although oxideconfined VCSELs have been employed in most of applications with VCSELs, ion-implanted VCSELs have a potential to be the better light sources for high power applications. In spite of the fact, the detailed characteristics of the ionimplanted VCSELs had been researched only in ten milliwatt-class output power. Here we report on a high power VCSEL-array with proton-implanted current apertures. A peak output power of over 40 W under short-pulse operation has been achieved. This is the first demonstration of ten watt-class output power for ion-implanted VCSELs.

  16. Design concepts of monolithic metamorphic vertical-cavity surface-emitting lasers for the 1300–1550 nm spectral range

    SciTech Connect

    Egorov, A. Yu. Karachinsky, L. Ya.; Novikov, I. I.; Babichev, A. V.; Nevedomskiy, V. N.; Bugrov, V. E.

    2015-11-15

    Possible design concepts for long-wavelength vertical-cavity surface-emitting lasers for the 1300–1550 nm spectral range on GaAs substrates are suggested. It is shown that a metamorphic GaAs–InGaAs heterostructure with a thin buffer layer providing rapid transition from the lattice constant of GaAs to that of In{sub x}Ga{sub 1–x}As with an indium fraction of x < 0.3 can be formed by molecular-beam epitaxy. Analysis by transmission electron microscopy demonstrated the effective localization of mismatch dislocations in the thin buffer layer and full suppression of their penetration into the overlying InGaAs metamorphic layer.

  17. Noise performance of high-speed radio over fiber links employing vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Ahmed, M.; Bakry, A.; Mahmoud, S. W. Z.

    2015-05-01

    This study investigates the intensity noise in high-speed vertical-cavity surface-emitting lasers (VCSELs) and its contribution to the noise performance of radio over fiber (RoF) links. We evaluate the sinusoidal modulation of VCSELs in terms of the second-order harmonic distortion (2HD) and third-order intermodulation distortion (IMD3) in additions to the relative intensity noise (RIN). The spurious-free dynamic range of the proposed VCSEL is estimated. The noise performance of the RoF link is assessed by the noise figure. The modulation characteristics of the VCSEL and the gain and noise factor (NF) of the fiber link are compared under conventional and high-speed modulations of VCSELs. Also, we present comparison of the NF between short (300 m) and relatively long (2 km) fibers.

  18. High-power vertical-cavity surface-emitting laser with an optimized p-contact diameter.

    PubMed

    Zhang, Yan; Ning, Yongqiang; Qin, Li; Wang, Ye; Cui, Jinjiang; Liu, Guangyu; Zhang, Xing; Wang, Zhenfu; Sun, Yanfang; Liu, Yun; Wang, Lijun

    2010-07-01

    A 980 nm bottom-emitting vertical-cavity surface-emitting laser (VCSEL) with a p-contact diameter is reported to achieve high power and good beam quality. A numerical simulation is conducted on the current spreading in a VCSEL with oxidation between the active region and the p-type distributed Bragg reflector. It is found that, for a particular oxide aperture diameter, somewhat homogeneous current distribution can be achieved for a VCSEL with an optimized p-contact diameter. The far-field divergence angle from a 600 microm diameter VCSEL is suppressed from 30 degrees to 15 degrees, and no strong sidelobe is observed in the far-field pattern by using the optimized p-contact diameter. There is a slight rise in threshold and optical output power that is due to the p-contact optimization. By improving the device packaging method, the maximum optical output power of the device is 2.01 W.

  19. Quantum well intermixing technique using proton implantation for carrier confinement of vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Moriwaki, Shouhei; Saitou, Minoru; Miyamoto, Tomoyuki

    2016-08-01

    We investigated quantum well intermixing (QWI) using proton implantation to form the carrier confinement structure in the active layer of a vertical-cavity surface-emitting laser (VCSEL). The required potential barrier height is discussed referring to the result of numerical analysis. The bandgap change due to the QWI was investigated experimentally for various quantum well structures, proton dose densities, and thermal annealing conditions. A potential barrier height of 30 meV was observed using a high-indium and thin-well structure. High crystalline quality was confirmed by photoluminescence intensity measurement, even after the QWI process, and the lasing of the fabricated QWI-VCSEL was observed without any deterioration. The proposed technique would be effective in improving the device performance in a simple fabrication process.

  20. Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

    SciTech Connect

    Alharthi, S. S. Henning, I. D.; Adams, M. J.; Hurtado, A.; Korpijarvi, V.-M.; Guina, M.

    2015-01-12

    We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in future optical systems.

  1. Single-exposure two-dimensional superresolution in digital holography using a vertical cavity surface-emitting laser source array.

    PubMed

    Granero, Luis; Zalevsky, Zeev; Micó, Vicente

    2011-04-01

    We present a new implementation capable of producing two-dimensional (2D) superresolution (SR) imaging in a single exposure by aperture synthesis in digital lensless Fourier holography when using angular multiplexing provided by a vertical cavity surface-emitting laser source array. The system performs the recording in a single CCD snapshot of a multiplexed hologram coming from the incoherent addition of multiple subholograms, where each contains information about a different 2D spatial frequency band of the object's spectrum. Thus, a set of nonoverlapping bandpass images of the input object can be recovered by Fourier transformation (FT) of the multiplexed hologram. The SR is obtained by coherent addition of the information contained in each bandpass image while generating an enlarged synthetic aperture. Experimental results demonstrate improvement in resolution and image quality.

  2. Vertical external cavity surface emitting PbTe/CdTe quantum dot lasers for the mid-infrared spectral region.

    PubMed

    Khiar, A; Eibelhuber, M; Volobuev, V; Witzan, M; Hochreiner, A; Groiss, H; Springholz, G

    2014-12-01

    Optically pumped vertical external cavity surface emitting lasers (VECSELS) emitting in the mid-infrared range are demonstrated with an active structure based on PbTe quantum dots (QDs) embedded in CdTe. In contrast to Stranski-Krastanov QDs, the PbTe QDs are fabricated by a strain-free synthesis method consisting of a molecular beam epitaxy growth step followed by a post-growth-annealing step. The laser emission of the VECSELs covers a wavelength range between 3.5 and 4.3 μm by changing the temperature from 85 to 240 K. The threshold power is lower than 100  mW(P) and the output power is more than 50  mW(P) at low temperature.

  3. Measurement of groove features and dimensions of the vertical test cathode and the choke joint of the superconducting electron gun cavity of the Energy Recovery LINAC

    SciTech Connect

    Hammons, L.; Ke, M.

    2011-10-13

    A testing program for the superconducting electron gun cavity that has been designed for the Energy Recovery LINAC is being planned. The goal of the testing program is to characterize the RF properties of the gun cavity at superconducting temperatures and, in particular, to study multipacting that is suspected to be occurring in the choke joint of the cavity where the vertical test cathode is inserted. The testing program will seek to understand the nature and cause of this multipacting and attempt to eliminate it, if possible, by supplying sufficient voltage to the cavity. These efforts are motivated by the multipacting issues that have been observed in the processing of the fine-grain niobium gun cavity. This cavity, which is being processed at Thomas Jefferson National Laboratory for Brookhaven, has encountered multipacting at a gradient of approximately 3 MV/m and, to date, has resisted efforts at elimination. Because of this problem, a testing program is being established here in C-AD that will use the large-grain niobium gun cavity that currently resides at Brookhaven and has been used for room-temperature measurements. The large-grain and fine-cavities are identical in every aspect of construction and only differ in niobium grain size. Thus, it is believed that testing and conditioning of the large-grain cavity should yield important insights about the fine-grain cavity. One element of this testing program involves characterizing the physical features of the choke joint of the cavity where the multipacting is believed to be occurring and, in particular the grooves of the joint. The configuration of the cavity and the vertical test cathode is shown in Figure 1. In addition, it is important to characterize the groove of the vertical test cathode. The grooved nature of these two components was specifically designed to prevent multipacting. However, it is suspected that, because of the chemical processing that the fine-grain gun cavity underwent along with the

  4. Analysis of the static and dynamic characteristics of 1310 nm vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Bäcker, Alexandra; Odermatt, Stefan; Römer, Friedhard; Streiff, Matthias; Witzigmann, Bernd

    2006-02-01

    We present the static and dynamic simulation of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) operating at around 1310 nm. The device consists of AlGaAs/GaAs distributed Bragg reflectors (DBRs) which are wafer-fused to both sides of the InP-based cavity with InAlGaAs quantum wells. A tunnel junction is used for current injection into the active region. The structure is simulated with a modified version of the commercial device simulator Synopsys Sentaurus Device. The fully-coupled two-dimensional electro-opto-thermal simulations use a microscopic physics-based model. Carrier transport is described by the continuity and Poisson equations and self-heating effects are accounted for by a thermodynamic equation. To obtain the opticalmodes, the wave equation is solved using a finite element approach. The optical gain model includes many-body effects. The equations are solved self-consistently. Calibrations of static (L-I, V-I curves) and dynamic characteristics (RIN) show good agreement with measurements at different temperatures. On this basis, the simulations reveal the critical factors that determine the modulation-current efficiency factor (MCEF) of the device.

  5. Surface-emitting vertical cavity with vapor-grown single crystal of cyano-substituted thiophene/phenylene co-oligomer

    NASA Astrophysics Data System (ADS)

    Hatano, Ryota; Goto, Kaname; Yamashita, Kenichi; Sasaki, Fumio; Yanagi, Hisao

    2017-04-01

    Photoluminescence from an organic microcavity is investigated using vapor-grown single crystals of 5,5‧-bis(4‧-cyano-biphenyl-4-yl)-2,2‧-bithiophene (BP2T-CN). A vertical half-cavity structure is fabricated with thin platelet crystals of BP2T-CN placed on a distributed Bragg reflector (DBR). Lying orientation of the BP2T-CN molecules is suitable for effective surface emission from the cavity. Angle-resolved photoluminescence spectra show anticrossing splits, suggesting the formation of cavity polaritons induced by coupling between confined photons and excitons. Phenomenological analysis well reproduces the dispersion characteristics with a Rabi splitting energy of 90 meV at room temperature. With increasing excitation fluence under optical pumping, one of the cavity photon modes is gain-narrowed, and amplified emission is obtained from the surface-emitting half-cavity structure.

  6. Bipolar Cascade Vertical-Cavity Surface-Emitting Lasers for RF Photonic Link Applications

    DTIC Science & Technology

    2007-09-01

    advisor position with very short notice, and Dr . Thomas R. Nelson, Jr. whose scientific curiosity always brings more out of me than I ever realized I...growth expertise. I also want to acknowledge Dr . John Albrecht, Dr . John Loehr, Dr . Robert Bedford, Lt. Col. Michael Estes, PhD, for sharing their...Allerman, S. Kurtz I. Fritz, W. Brei- land, K. Geib R. Sieg, J. Scott, and R. Naone. “Room temperature continuous wave InGaAsN quantum well vertical

  7. Ultrafast pulse amplification in mode-locked vertical external-cavity surface-emitting lasers

    SciTech Connect

    Böttge, C. N. Hader, J.; Kilen, I.; Moloney, J. V.; Koch, S. W.

    2014-12-29

    A fully microscopic many-body Maxwell–semiconductor Bloch model is used to investigate the influence of the non-equilibrium carrier dynamics on the short-pulse amplification in mode-locked semiconductor microlaser systems. The numerical solution of the coupled equations allows for a self-consistent investigation of the light–matter coupling dynamics, the carrier kinetics in the saturable absorber and the multiple-quantum-well gain medium, as well as the modification of the light field through the pulse-induced optical polarization. The influence of the pulse-induced non-equilibrium modifications of the carrier distributions in the gain medium and the saturable absorber on the single-pulse amplification in the laser cavity is identified. It is shown that for the same structure, quantum wells, and gain bandwidth the non-equilibrium carrier dynamics lead to two preferred operation regimes: one with pulses in the (sub-)100 fs-regime and one with multi-picosecond pulses. The recovery time of the saturable absorber determines in which regime the device operates.

  8. Operation of a novel hot-electron vertical-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Balkan, Naci; O'Brien-Davies, Angela; Thoms, A. B.; Potter, Richard J.; Poolton, Nigel; Adams, Michael J.; Masum, J.; Bek, Alpan; Serpenguzel, Ali; Aydinli, Atilla; Roberts, John S.

    1998-07-01

    The hot Electron Light Emission and Lasing in Semiconductor Heterostructures devices (HELLISH-1) is novel surface emitter consisting of a GaAs quantum well, within the depletion region, on the n side of Ga1-xAlxAs p- n junction. It utilizes hot electron transport parallel to the layers and injection of hot electron hole pairs into the quantum well through a combination of mechanisms including tunnelling, thermionic emission and diffusion of `lucky' carriers. Super Radiant HELLISH-1 is an advanced structure incorporating a lower distributed Bragg reflector (DBR). Combined with the finite reflectivity of the upper semiconductor-air interface reflectivity it defines a quasi- resonant cavity enabling emission output from the top surface with a higher spectral purity. The output power has increased by two orders of magnitude and reduced the full width at half maximum (FWHM) to 20 nm. An upper DBR added to the structure defines HELLISH-VCSEL which is currently the first operational hot electron surface emitting laser and lases at room temperature with a 1.5 nm FWHM. In this work we demonstrate and compare the operation of UB-HELLISH-1 and HELLISH-VCSEL using experimental and theoretical reflectivity spectra over an extensive temperature range.

  9. All-epitaxial, lithographically defined, current- and mode-confined vertical-cavity surface-emitting laser based on selective interfacial fermi-level pinning

    SciTech Connect

    Ahn, J.; Lu, D.; Deppe, D.G.

    2005-01-10

    An approach is presented to fabricate a current- and mode-confined vertical-cavity surface-emitting laser that is all-epitaxial and lithographically defined. The device uses selective Fermi level pinning to self-align the electrical injection to a mode-confining intracavity phase-shifting mesa.

  10. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Zaugg, C. A.; Gronenborn, S.; Moench, H.; Mangold, M.; Miller, M.; Weichmann, U.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U.

    2014-03-01

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM00 mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiNx and SiO2) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm2 to 1.1 μJ/cm2, respectively.

  11. Absorber and gain chip optimization to improve performance from a passively modelocked electrically pumped vertical external cavity surface emitting laser

    SciTech Connect

    Zaugg, C. A. Mangold, M.; Pallmann, W. P.; Golling, M.; Tilma, B. W.; Keller, U.; Gronenborn, S.; Moench, H.; Weichmann, U.; Miller, M.

    2014-03-24

    We present an electrically pumped vertical-external-cavity surface-emitting laser (EP-VECSEL) modelocked with a semiconductor saturable absorber mirror (SESAM) with significantly improved performance. In different cavity configurations, we present the shortest pulses (2.5 ps), highest average output power (53.2 mW), highest repetition rate (18.2 GHz), and highest peak power (4.7 W) to date. The simple and low-cost concept of EP-VECSELs is very attractive for mass-market applications such as optical communication and clocking. The improvements result from an optimized gain chip from Philips Technologie GmbH and a SESAM, specifically designed for EP-VECSELs. For the gain chip, we found a better trade-off between electrical and optical losses with an optimized doping scheme in the substrate to increase the average output power. Furthermore, the device's bottom contact diameter (60 μm) is smaller than the oxide aperture diameter (100 μm), which favors electro-optical conversion into a TEM{sub 00} mode. Compared to optically pumped VECSELs we have to increase the field enhancement in the active region of an EP-VECSEL which requires a SESAM with lower saturation fluence and higher modulation depth for modelocking. We therefore used a resonant quantum well SESAM with a 3.5-pair dielectric top-coating (SiN{sub x} and SiO{sub 2}) to enhance the field in the absorber at the lasing wavelength of 980 nm. The absorption bandedge at room temperature is detuned (965 nm) compared to the resonance (980 nm), which enables temperature-tuning of the modulation depth and saturation fluence from approximately 2.5% up to 15% and from 20 μJ/cm{sup 2} to 1.1 μJ/cm{sup 2}, respectively.

  12. Low-threshold lasing of InGaN vertical-cavity surface-emitting lasers with dielectric distributed Bragg reflectors

    NASA Astrophysics Data System (ADS)

    Tawara, Takehiko; Gotoh, Hideki; Akasaka, Tetsuya; Kobayashi, Naoki; Saitoh, Tadashi

    2003-08-01

    Lasing action is achieved in InGaN vertical-cavity surface-emitting lasers (VCSELs) with dielectric distributed Bragg reflectors (DBRs). We fabricated III-nitride VCSELs by removing a SiC substrate from a III-nitride cavity with a dry etching technique and then wafer bonding the cavity and SiO2/ZrO2 DBRs. These VCSELs have a high quality factor of 460 and a spontaneous emission factor of 10-2. We observed lasing at a wavelength of 401 nm at room temperature with optical pumping. This lasing action was demonstrated at a low threshold of 5.1 mJ/cm2 by using a high-quality crystalline cavity and quantum-well layers without surface roughening or cracking.

  13. Retinal, anterior segment and full eye imaging using ultrahigh speed swept source OCT with vertical-cavity surface emitting lasers

    PubMed Central

    Grulkowski, Ireneusz; Liu, Jonathan J.; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Lu, Chen D.; Jiang, James; Cable, Alex E.; Duker, Jay S.; Fujimoto, James G.

    2012-01-01

    We demonstrate swept source OCT utilizing vertical-cavity surface emitting laser (VCSEL) technology for in vivo high speed retinal, anterior segment and full eye imaging. The MEMS tunable VCSEL enables long coherence length, adjustable spectral sweep range and adjustable high sweeping rate (50–580 kHz axial scan rate). These features enable integration of multiple ophthalmic applications into one instrument. The operating modes of the device include: ultrahigh speed, high resolution retinal imaging (up to 580 kHz); high speed, long depth range anterior segment imaging (100 kHz) and ultralong range full eye imaging (50 kHz). High speed imaging enables wide-field retinal scanning, while increased light penetration at 1060 nm enables visualization of choroidal vasculature. Comprehensive volumetric data sets of the anterior segment from the cornea to posterior crystalline lens surface are also shown. The adjustable VCSEL sweep range and rate make it possible to achieve an extremely long imaging depth range of ~50 mm, and to demonstrate the first in vivo 3D OCT imaging spanning the entire eye for non-contact measurement of intraocular distances including axial eye length. Swept source OCT with VCSEL technology may be attractive for next generation integrated ophthalmic OCT instruments. PMID:23162712

  14. Study on effect of quantum well number on performance characteristics of GaN-based vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Zandi Goharrizi, A.; Alahyarizadeh, Gh.; Hassan, Z.; Abu Hassan, H.

    2013-05-01

    The effect of number of quantum wells and quantum well thickness on the optical performance of InGaN vertical cavity surface emitting laser (VCSEL) was numerically investigated using Integrated System Engineering Technical Computer Aided Design (ISE TCAD) simulation program. The simulation results indicated that the output power and differential quantum efficiency of the double quantum well (DQW) laser were increased and threshold current decreased as compared to the single and triplet quantum wells VCSEL. Threshold current enhancement in the single quantum well (SQW) is attributed to the electron carrier leakage increasing from active layers because of the lower optical confinement factor. Simulation results show that in the double quantum well, the optical material gain and electron and hole carrier densities are approximately uniform with respect to the SQW and TQW. Also these results indicated that the electron current density in the DQW is the lowest. In the active region, electrical field decreased for the double quantum well because of the built-in electrical field reduction inside the quantum well. Finally the effect of quantum well thickness in DQW GaN-based VCSEL was investigated and it was observed that DQW VCSEL with 3 nm quantum wells thickness had the optimum threshold current.

  15. Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback

    SciTech Connect

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

    2016-01-15

    In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θ{sub p}. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θ{sub p}. The maximum value of the cross-correlation coefficient achieved is −0.99 with a zero time delay over a wide range of θ{sub p} beyond 65° with a poor synchronization dynamic at θ{sub p} less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θ{sub p}. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

  16. Nonlinear dynamics of the polarization of multitransverse mode vertical-cavity surface-emitting lasers under current modulation.

    PubMed

    Valle, A; Sciamanna, M; Panajotov, K

    2007-10-01

    In this paper we report on a theoretical investigation of the nonlinear dynamics of the polarization of multitransverse mode vertical-cavity surface-emitting lasers (VCSELs) under current modulation. Special attention is given to the comparison with a previously studied case of single-transverse mode VCSEL emitting in two orthogonal polarizations. The consideration of spatial effects in VCSEL modifies the polarization dynamics that accompanies the period doubling route to chaos for large modulation amplitudes. Depending on the modulation parameters, the excitation of a higher order transverse mode may either induce chaotic pulsing in an otherwise regularly pulsating VCSEL, or induce a time-periodic pulsing dynamics in an otherwise chaotic VCSEL. Bifurcation diagrams obtained for different modulation frequencies, several values of the dichroism, and different transverse mode characteristics allow us to identify the different scenarios of polarization dynamics in a directly modulated VCSEL. Temporal analysis of carrier number radial profile reveals considerable changes for the multitransverse mode case only constituting the physical origin of the reported changes in the temporal and polarization dynamics.

  17. Birefringence controlled room-temperature picosecond spin dynamics close to the threshold of vertical-cavity surface-emitting laser devices

    NASA Astrophysics Data System (ADS)

    Li, M. Y.; Jähme, H.; Soldat, H.; Gerhardt, N. C.; Hofmann, M. R.; Ackemann, T.

    2010-11-01

    We analyze the spin-induced circular polarization dynamics at the threshold of vertical-cavity surface-emitting lasers at room-temperature using a hybrid excitation combining electrically pumping without spin preference and spin-polarized optical injection. After a short pulse of spin-polarized excitation, fast oscillations of the circular polarization degree (CPD) are observed within the relaxation oscillations. A theoretical investigation of this behavior on the basis of a rate equation model shows that these fast oscillations of CPD could be suppressed by means of a reduction of the birefringence of the laser cavity.

  18. Characteristics of bistable localized emission states in broad-area vertical-cavity surface-emitting lasers with frequency-selective feedback

    SciTech Connect

    Tanguy, Y.; Ackemann, T.; Jaeger, R.

    2006-11-15

    Small-area bistable lasing spots (about 10 {mu}m full width at half maximum) can be created at different positions within the aperture of a broad-area vertical-cavity surface-emitting laser (aperture diameter 80 {mu}m) with frequency-selective feedback from a grating in Littrow configuration, and an additional pinhole localizing feedback to a part of the laser. Their characteristics are analyzed depending on the grating tuning, injection current, and feedback strength. These spots are considered to be good candidates for self-localized cavity solitons, if the perturbation by boundaries can be reduced using devices with larger diameter.

  19. Analysis of fluid-solid interaction in MHD natural convection in a square cavity equally partitioned by a vertical flexible membrane

    NASA Astrophysics Data System (ADS)

    Mehryan, S. A. M.; Ghalambaz, Mohammad; Ismael, Muneer A.; Chamkha, Ali J.

    2017-02-01

    This paper investigates numerically the problem of unsteady natural convection inside a square cavity partitioned by a flexible impermeable membrane. The finite element method with the arbitrary Lagrangian-Eulerian (ALE) technique has been used to model the interaction of the fluid and the membrane. The horizontal walls of the cavity are kept adiabatic while the vertical walls are kept isothermal at different temperatures. A uniform magnetic field is applied onto the cavity with different orientations. The cavity has been provided by two eyelets to compensate volume changes due the movement of the flexible membrane. A parametric study is carried out for the pertinent parameters, which are the Rayleigh number (105-108), Hartmann number (0-200) and the orientation of the magnetic field (0-180°). The change in the Hartmann number affects the shape of the membrane and the heat transfer in the cavity. The angle of the magnetic field orientation also significantly affects the shape of the membrane and the heat transfer in the cavity.

  20. Vertical cavity surface emitting laser based on gallium arsenide/air-gap distributed Bragg reflectors: From concept to working devices

    NASA Astrophysics Data System (ADS)

    Mo, Qingwei

    Vertical-cavity surface-emitting lasers (VCSELs) have created new opportunities in optoelectronics. However, VCSELs have so far been commercialized mainly for operation at 0.85 mum, despite their potential importance at other wavelengths, such as 1.3 mum and 1.55 mum. The limitations at these longer wavelengths come from material characteristics, such as a low contrast ratio in mirror materials, lower mirror reflectivity, and smaller optical gain for longer wavelength materials versus AlGaAs/GaAs quantum wells. A similar situation, insufficient gain relative to the cavity loss, existed in the past for shorter wavelength VCSELs before high quality epitaxial mirrors were developed. Semiconductor/air-gap Distributed Bragg Reflectors (DBRs) are attractive due to their high index contrast, which leads to a high reflectivity, wide stop band and low optical loss mirror with a small number of pairs. This concept is ready to be integrated into material systems other than AlGaAs/GaAs, which is studied in this work. Therefore, the impact of these DBRs can be extended into both visible and longer infrared wavelengths as a solution to the trade-off between DBR and active region materials. Air-gap DBRs can also be used as basic building blocks of micro-opto-electro-mechanical systems (MOEMS). The high Q microcavity formed by the air-gap DBRs also provide a good platform for microcavity physics study. Air-gap DBRs are modeled using the transmission matrix formulae of the Maxwell equations. A comparison to existing DBR technology shows the great advantage and potential that the air-gap DBR possesses. Two types of air-gap are proposed and developed. The first one includes multiple GaAs/air pairs while the second one combines a single air-gap with metal and dielectric mirrors. New device structures and processing designs, especially an all-epitaxial lateral current and optical confinement technique, are carried out to incorporate air-gap DBRs into VCSEL structures. The first VCSEL

  1. In-well pumped mid-infrared PbTe/CdTe quantum well vertical external cavity surface emitting lasers

    SciTech Connect

    Khiar, A. Witzan, M.; Hochreiner, A.; Eibelhuber, M.; Springholz, G.; Volobuev, V.

    2014-06-09

    Optical in-well pumped mid-infrared vertical external cavity surface emitting lasers based on PbTe quantum wells embedded in CdTe barriers are realized. In contrast to the usual ternary barrier materials of lead salt lasers such as PbEuTe of PbSrTe, the combination of narrow-gap PbTe with wide-gap CdTe offers an extremely large carrier confinement, preventing charge carrier leakage from the quantum wells. In addition, optical in-well pumping can be achieved with cost effective and readily available near infrared lasers. Free carrier absorption, which is a strong loss mechanism in the mid-infrared, is strongly reduced due to the insulating property of CdTe. Lasing is observed from 85 K to 300 K covering a wavelength range of 3.3–4.2 μm. The best laser performance is achieved for quantum well thicknesses of 20 nm. At low temperature, the threshold power is around 100 mW{sub P} and the output power more than 700 mW{sub P}. The significance of various charge carrier loss mechanisms are analyzed by modeling the device performance. Although Auger losses are quite low in IV–VI semiconductors, an Auger coefficient of C{sub A} = 3.5 × 10{sup −27} cm{sup 6} s{sup −1} was estimated for the laser structure, which is attributed to the large conduction band offset.

  2. Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture

    SciTech Connect

    Leonard, J. T. Yonkee, B. P.; Cohen, D. A.; Megalini, L.; Speck, J. S.; Lee, S.; DenBaars, S. P.; Nakamura, S.

    2016-01-18

    We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC) etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PEC etch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PEC etch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm{sup 2} (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP{sub 12,1}), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.

  3. Two-dimensional pseudo-random optical phased array based on tandem optical injection locking of vertical cavity surface emitting lasers.

    PubMed

    Sayyah, Keyvan; Efimov, Oleg; Patterson, Pamela; Schaffner, James; White, Carson; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander

    2015-07-27

    We demonstrate, both theoretically and experimentally, a pseudo-random, two-dimensional optical phased array (OPA) concept based on tandem injection locking of 64-element vertical cavity surface emitting laser (VCSEL) arrays. A low cavity-Q VCSEL design resulted in an injection locking optical power of less than 1 μW per VCSEL, providing large OPA scaling potential. Tandem injection locking of two VCSEL arrays resulted in measured controllable optical phase change of 0-1.6π. A high quality beam formed with suppressed grating lobes due to the pseudo-random array design was demonstrated with performance close to simulated results. A preliminary 2.2° x 1.2° beam steering example using the tandem arrays was also demonstrated.

  4. Room-temperature continuous-wave operation of GaN-based vertical-cavity surface-emitting lasers fabricated using epitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

    Izumi, Shouichiro; Fuutagawa, Noriyuki; Hamaguchi, Tatsushi; Murayama, Masahiro; Kuramoto, Masaru; Narui, Hironobu

    2015-06-01

    We have successfully demonstrated the room-temperature continuous-wave operation of GaN-based vertical-cavity surface-emitting lasers (VCSELs) with all-dielectric reflectors, which were fabricated using epitaxial lateral overgrowth. The VCSELs exhibited a threshold current of 8 mA and a threshold voltage of 4.5 V at a lasing wavelength of 446 nm. The maximum output power was 0.9 mW for an 8-µm-diameter current aperture, which was made possible because of the high thermal conductivity of the GaN substrate.

  5. Analysis of mode stability in a concave mirror vertical-cavity surface-emitting laser with an oxide aperture.

    PubMed

    Ju, Young-Gu

    2005-05-16

    We applied the Fox-Li resonator theory to analyze the mode stability of concave mirror surface-emitting lasers. The numerical modeling incorporates the oxide aperture in the simple classical cavity by adding a non-uniform phase shifting layer to the flat mirror side. The calculation shows that there is a modal loss difference between the fundamental mode and the competing modes. The amount of loss difference depends upon cavity length and the thickness of the oxide aperture. In addition to loss difference, modal gain difference plays a key role in discriminating between the fundamental mode and the higher order transverse modes. The modal gain difference heavily depends upon the size of the oxide aperture and the field intensity distribution. To summarize, the geometry of the concave cavity affects the mode profile and the unique field profile of each transverse mode makes a difference in both modal loss and gain. Finally, this leads to a side-mode suppression.

  6. Analysis of bistability conditions between lasing and nonlasing states for a vertical-cavity surface-emitting laser with frequency-selective optical feedback using an envelope approximation

    SciTech Connect

    Naumenko, A. V.; Loiko, N. A.; Ackemann, T.

    2007-08-15

    The emission characteristics of a vertical-cavity surface-emitting laser (VCSEL) coupled to an external cavity with a diffraction grating as a frequency-selective element are theoretically analyzed. We introduce envelope functions for the set of external-cavity modes based on the loci of modes with extremal gain or frequency in the proper parameter space. Replacing the set of discrete stationary solutions by these envelope functions, simple analytical expressions are derived for the existence of bistability between a lasing state strongly affected by the feedback and a state close to the solitary laser emission (in particular the nonlasing state) and for the frequency of the VCSEL in the grating-controlled regime. It is shown how the initial jump of the laser intensity during abrupt turn-on can be maximized. By a control of the feedback change, the width of the hysteresis loop can be increased significantly. The scheme under consideration can be useful in all-optical photonic switching applications.

  7. In-vitro detection of artificial caries on vertical dental cavity walls using infrared photothermal radiometry and modulated luminescence

    NASA Astrophysics Data System (ADS)

    Kim, Jungho; Mandelis, Andreas; Abrams, Stephen H.; Vu, Jaclyn T.; Amaechi, Bennett T.

    2012-12-01

    The main objective of the study was to investigate the ability of frequency-domain photothermal radiometry (PTR) and modulated luminescence (LUM) to detect secondary caries lesions on the walls of restorations (wall lesions). Changes in experimental PTR-LUM signals due to sequential demineralization on entire vertical walls of sectioned tooth samples were investigated. In addition, transverse micro-radiography (TMR) analysis (used as a gold standard) was conducted to measure the degree of demineralization that occurred in each sample. Statistical correlation between TMR results and PTR-LUM signals was determined using Pearson's correlation coefficient. LUM signals were found to be dominated by the scattered component of the incident laser beam. The more clinically relevant cases of localized demineralization and remineralization on vertical walls were also investigated to examine whether PTR-LUM signals are sensitive to demineralization and remineralization of much smaller areas. The overall results demonstrated that PTR-LUM is sensitive to progressive demineralization and remineralization on vertical walls of sectioned tooth samples.

  8. Square-wave switching in vertical-cavity surface-emitting lasers with polarization-rotated optical feedback: Experiments and simulations

    NASA Astrophysics Data System (ADS)

    Sukow, David W.; Gilfillan, Taylor; Pope, Brenton; Torre, Maria S.; Gavrielides, Athanasios; Masoller, Cristina

    2012-09-01

    We study experimentally the dynamics of vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated (PR) optical feedback, such that the natural lasing polarization of a VCSEL is rotated by 90 deg and then is reinjected into the laser. We observe noisy, square-wave-like polarization switchings with periodicity slightly longer than twice the delay time, which degrade to (or alternate with) bursts of irregular oscillations. We present results of simulations that are in good agreement with the observations. The simulations demonstrate that close to threshold the regular switching is very sensitive to noise, while well above threshold is less affected by the noise strength. The frequency splitting between the two polarizations plays a key role in the switching regularity, and we identify wide parameter regions where deterministic and robust switching can be observed.

  9. Room-temperature vertical-cavity surface-emitting lasers at 4 μm with GaSb-based type-II quantum wells

    NASA Astrophysics Data System (ADS)

    Veerabathran, G. K.; Sprengel, S.; Andrejew, A.; Amann, M.-C.

    2017-02-01

    We report electrically pumped λ = 4 μm vertical-cavity surface-emitting lasers (VCSELs) that significantly extend the wavelength range covered with electrically pumped VCSELs into the mid infrared. A single stage active region with eight type-II quantum wells provides sufficient gain, while lateral current confinement and waveguiding are accomplished with the proven buried tunnel junction technology. These devices operate in continuous wave (CW) up to -7 °C and in pulsed operation up to 45 °C. Their CW threshold pump power levels are below 10 mW at temperatures well accessible by thermo-electric cooling, and their maximum single-mode output power is around 0.18 mW. Single-mode operation with side-mode suppression ratio of more than 20 dB and a continuous electro-thermal tuning range as large as 19.2 nm are achieved.

  10. Frequency-modulated continuous-wave laser radar using dual vertical-cavity surface-emitting laser diodes for real-time measurements of distance and radial velocity

    NASA Astrophysics Data System (ADS)

    Kakuma, Seiichi

    2017-02-01

    A frequency-modulated continuous-wave (FMCW) laser radar capable of real-time displaying the distance to a target object and its radial velocity as their corresponding frequency spectra is developed. The system employs a pair of oppositely frequency-swept vertical-cavity surface-emitting laser diodes (VCSELs). This makes possible simultaneous detection of beat signals induced by the increment (up-ramp) and decrement (down-ramp) in laser frequencies. By mixing these two beat signals, their sum and difference frequencies are directly obtained without arithmetic processing such as averaging and subtraction. Results of the test experiments adopting axially moving block gauges as target objects show that both the distance and given velocities are accurately determined from the spectrum of the frequency mixer.

  11. Control of emitted light polarization in a 1310 nm dilute nitride spin-vertical cavity surface emitting laser subject to circularly polarized optical injection

    SciTech Connect

    Alharthi, S. S. Hurtado, A.; Al Seyab, R. K.; Henning, I. D.; Adams, M. J.; Korpijarvi, V.-M.; Guina, M.

    2014-11-03

    We experimentally demonstrate the control of the light polarization emitted by a 1310 nm dilute nitride spin-Vertical Cavity Surface Emitting Laser (VCSEL) at room temperature. This is achieved by means of a combination of polarized optical pumping and polarized optical injection. Without external injection, the polarization of the optical pump controls that of the spin-VCSEL. However, the addition of the externally injected signal polarized with either left- (LCP) or right-circular polarization (RCP) is able to control the polarization of the spin-VCSEL switching it at will to left- or right-circular polarization. A numerical model has been developed showing a very high degree of agreement with the experimental findings.

  12. AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasers.

    PubMed

    Xiang, Y; Reuterskiöld-Hedlund, C; Yu, X; Yang, C; Zabel, T; Hammar, M; Akram, M N

    2015-06-15

    We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60°C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection for reduced extrinsic resistances.

  13. Multiple-Wavelength Vertical-Cavity Surface-Emitting Lasers by Grading a Spacer Layer for Short-Reach Wavelength Division Multiplexing Applications

    NASA Astrophysics Data System (ADS)

    Dayal, Padullaparthi Babu; Sakaguchi, Takahiro; Matsutani, Akihiro; Koyama, Fumio

    2009-09-01

    We propose and demonstrate a simple and unique method to fabricate the multiple-wavelength vertical-cavity surface-emitting lasers (VCSELs) emitting at 980 nm by grading only the first low-index spacer layer of SiO2/Ta2O5 dielectric mirror. A multi step exposure to UV lithography followed by selective wet chemical etching has been applied to create spacer layer gradients. We have successfully realized equally spaced four-channel VCSELs with wavelength span exceeding 30.0 nm by grading a 230.0 nm spacer layer and achieved single mode lasing with a side mode suppression ratio in excess of 30.0 dB.

  14. Ultrafast and widely tuneable vertical-external-cavity surface-emitting laser, mode-locked by a graphene-integrated distributed Bragg reflector.

    PubMed

    Zaugg, C A; Sun, Z; Wittwer, V J; Popa, D; Milana, S; Kulmala, T S; Sundaram, R S; Mangold, M; Sieber, O D; Golling, M; Lee, Y; Ahn, J H; Ferrari, A C; Keller, U

    2013-12-16

    We report a versatile way of controlling the unsaturated loss, modulation depth and saturation fluence of graphene-based saturable absorbers (GSAs), by changing the thickness of a spacer between a single layer graphene (SLG) and a high-reflection mirror. This allows us to modulate the electric field intensity enhancement at the GSA from 0 up to 400%, due to the interference of incident and reflected light at the mirror. The unsaturated loss of the SLG-mirror-assembly can be reduced to ∼0. We use this to mode-lock a vertical-external-cavity surface-emitting laser (VECSEL) from 935 to 981 nm. This approach can be applied to integrate SLG into various optical components, such as output coupler mirrors, dispersive mirrors or dielectric coatings on gain materials. Conversely, it can also be used to increase the absorption (up to 10%) in various graphene based photonics and optoelectronics devices, such as photodetectors.

  15. Compact electro-absorption modulator integrated with vertical-cavity surface-emitting laser for highly efficient millimeter-wave modulation

    SciTech Connect

    Dalir, Hamed; Ahmed, Moustafa; Bakry, Ahmed; Koyama, Fumio

    2014-08-25

    We demonstrate a compact electro-absorption slow-light modulator laterally-integrated with an 850 nm vertical-cavity surface-emitting laser (VCSEL), which enables highly efficient millimeter-wave modulation. We found a strong leaky travelling wave in the lateral direction between the two cavities via widening the waveguide width with a taper shape. The small signal response of the fabricated device shows a large enhancement of over 55 dB in the modulation amplitude at frequencies beyond 35 GHz; thanks to the photon-photon resonance. A large group index of over 150 in a Bragg reflector waveguide enables the resonance at millimeter wave frequencies for 25 μm long compact modulator. Based on the modeling, we expect a resonant modulation at a higher frequency of 70 GHz. The resonant modulation in a compact slow-light modulator plays a significant key role for high efficient narrow-band modulation in the millimeter wave range far beyond the intrinsic modulation bandwidth of VCSELs.

  16. Optical levitation and translation of a microscopic particle by use of multiple beams generated by vertical-cavity surface-emitting laser array sources.

    PubMed

    Ogura, Yusuke; Shirai, Nobuhiro; Tanida, Jun

    2002-09-20

    An optical levitation and translation method for a microscopic particle by use of the resultant force induced by multiple light beams is studied. We show dependence of the radiation pressure force on the illuminating distribution by numerical calculation, and we find that the strongest axial force is obtained by a specific spacing period of illuminating beams. Extending the optical manipulation technique by means of vertical-cavity surface-emitting laser (VCSEL) array sources [Appl. Opt. 40, 5430 (2001)], we are the first, to our knowledge, to demonstrate levitation of a particle and its translation while levitated by using a VCSEL array. The vertical position of the target particle can be controlled in a range of a few tens of micrometers with an accuracy of 2 microm or less. The analytical and experimental results suggest that use of multiple beams is an effective method to levitate a particle with low total illumination power. Some issues on the manipulation method that uses multiple beams are discussed.

  17. Phase noise analysis of a 10-GHz optical injection-locked vertical-cavity surface-emitting laser-based optoelectronic oscillator

    NASA Astrophysics Data System (ADS)

    Coronel, Juan; Varón, Margarita; Rissons, Angélique

    2016-09-01

    The optical injection locking (OIL) technique is proposed to reduce the phase noise of a carrier generated for a vertical-cavity surface-emitting laser (VCSEL)-based optoelectronic oscillator. The OIL technique permits the enhancement of the VCSEL direct modulation bandwidth as well as the stabilization of the optical noise of the laser. A 2-km delay line, 10-GHz optical injection-locked VCSEL-based optoelectronic oscillator (OILVBO) was implemented. The internal noise sources of the optoelectronic oscillator components were characterized and analyzed to understand the noise conversion of the system into phase noise in the oscillator carrier. The implemented OILVBO phase noise was -105.7 dBc/Hz at 10 kHz from the carrier; this value agrees well with the performed simulated analysis. From the computed and measured phase noise curves, it is possible to infer the noise processes that take place inside the OILVBO. As a second measurement of the oscillation quality, a time-domain analysis was done through the Allan's standard deviation measurement, reported for first time for an optoelectronic oscillator using the OIL technique.

  18. The influence of quaternary electron blocking layer on the performance characteristics of intracavity-contacted oxide-confined InGaN-based vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Goharrizi, A. Zandi; Alahyarizadeh, Gh.; Hassan, Z.; Hassan, H. Abu

    2015-11-01

    The effect of electron blocking layer (EBL) on the performance characteristics of InGaN-based vertical cavity surface emitting lasers (VCSELs) was numerically investigated using an integrated system engineering technical computer aided design (ISE TCAD) simulation program. Simulation results indicated that the performance characteristics of InGaN quantum well VCSEL were improved by the ternary Al0.17Ga0.83N EBL. Better performance was also obtained when Al0.17Ga0.83N EBL was replaced by a polarization-matched Al0.275In0.115Ga0.61N EBL having the same energy bandgap. The quaternary EBL enhances the output power and differential quantum efficiency (DQE) as well as reduces the threshold current compared with the ternary EBL. Enhancement in the value of the optical intensity was also observed in the VCSEL structure with quaternary EBL. Furthermore, the effect of Al composition of AlInGaN EBL on the performance of InGaN-based VCSEL structure that uses the quaternary AlInGaN EBL was studied. In mole fraction was 0.115, Al mole fraction changed from 0.260 to 0.290 by step 0.005, and optimum performance was achieved in 0.275 Al mole fraction of AlInGaN EBL.

  19. Continuous wave vertical cavity surface emitting lasers at 2.5 μm with InP-based type-II quantum wells

    SciTech Connect

    Sprengel, S.; Andrejew, A.; Federer, F.; Veerabathran, G. K.; Boehm, G.; Amann, M.-C.

    2015-04-13

    A concept for electrically pumped vertical cavity surface emitting lasers (VCSEL) for emission wavelength beyond 2 μm is presented. This concept integrates type-II quantum wells into InP-based VCSELs with a buried tunnel junction as current aperture. The W-shaped quantum wells are based on the type-II band alignment between GaInAs and GaAsSb. The structure includes an epitaxial GaInAs/InP and an amorphous AlF{sub 3}/ZnS distributed Bragg reflector as bottom and top (outcoupling) mirror, respectively. Continuous-wave operation up to 10 °C at a wavelength of 2.49 μm and a peak output power of 400 μW at −18 °C has been achieved. Single-mode emission with a side-mode suppression ratio of 30 dB for mesa diameters up to 14 μm is presented. The long emission wavelength and current tunability over a wavelength range of more than 5 nm combined with its single-mode operation makes this device ideally suited for spectroscopy applications.

  20. Vertical-cavity surface-emitting laser in the long-wavelength (700 nm) region in the visible by energy transfer between organic dyes

    NASA Astrophysics Data System (ADS)

    Liao, Zhifu; Zhou, Yuan; Cui, Yuanjing; Yang, Yu; Wang, Zhiyu; Qian, Guodong

    2014-06-01

    In this work, organic vertical-cavity surface-emitting lasers (VCSELs) with single-mode laser output in the long-wavelength region (~700 nm) of the visible were reported based on the energy transfer between dye pairs consisting of pyrromethene 597 (PM597) and rhodamine 700 (LD700). By co-doping PM597 into the polymeric hosts, the fluorescence intensity of LD700 was enhanced by 30-fold and the photophysical parameters of the donor-acceptor pairs were investigated, indicating the involvement of non-radiative resonance energy transfer processes between PM597 and LD700. Active distributed Bragg reflectors (DBR) were made by alternately spin-coating dye-doped polyvinylcarbazole and cellulose acetate thin films as the high and low refractive index layers, respectively. By sandwiching the active layer with 2 DBR mirrors, VCSEL emission at 698.9 nm in the biological first window (650-950 nm) was observed under the 532-nm laser pulses. The laser slope efficiency and threshold were also measured.

  1. Demonstration of a III-nitride vertical-cavity surface-emitting laser with a III-nitride tunnel junction intracavity contact

    SciTech Connect

    Leonard, J. T. Young, E. C.; Yonkee, B. P.; Cohen, D. A.; Margalith, T.; Speck, J. S.; DenBaars, S. P.; Nakamura, S.

    2015-08-31

    We report on a III-nitride vertical-cavity surface-emitting laser (VCSEL) with a III-nitride tunnel junction (TJ) intracavity contact. The violet nonpolar VCSEL employing the TJ is compared to an equivalent VCSEL with a tin-doped indium oxide (ITO) intracavity contact. The TJ VCSEL shows a threshold current density (J{sub th}) of ∼3.5 kA/cm{sup 2}, compared to the ITO VCSEL J{sub th} of 8 kA/cm{sup 2}. The differential efficiency of the TJ VCSEL is also observed to be significantly higher than that of the ITO VCSEL, reaching a peak power of ∼550 μW, compared to ∼80 μW for the ITO VCSEL. Both VCSELs display filamentary lasing in the current aperture, which we believe to be predominantly a result of local variations in contact resistance, which may induce local variations in refractive index and free carrier absorption. Beyond the analyses of the lasing characteristics, we discuss the molecular-beam epitaxy (MBE) regrowth of the TJ, as well as its unexpected performance based on band-diagram simulations. Furthermore, we investigate the intrinsic advantages of using a TJ intracavity contact in a VCSEL using a 1D mode profile analysis to approximate the threshold modal gain and general loss contributions in the TJ and ITO VCSEL.

  2. Cavity-resonator-integrated guided-mode resonance filter for aperture miniaturization.

    PubMed

    Kintaka, Kenji; Majima, Tatsuya; Inoue, Junichi; Hatanaka, Koji; Nishii, Junji; Ura, Shogo

    2012-01-16

    A guided-mode resonance filter integrated in a waveguide cavity resonator constructed by two distributed Bragg reflectors is designed and fabricated for miniaturization of aperture size. Reflection efficiency of >90% and wavelength selectivity of 0.4 nm are predicted in the designed SiO(2)-based filter with 50-μm aperture by a numerical calculation using the finite-difference time-domain method. A maximum reflectance of 67% with 0.5-nm bandwidth is experimentally demonstrated by the fabricated device at around 850-nm wavelength.

  3. Failure mode analysis of degraded InGaAs-AlGaAs strained quantum well multi-mode vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Lingley, Zachary; Brodie, Miles; Huang, Michael; Bushmaker, Adam; Theiss, Jesse; Presser, Nathan; Foran, Brendan; Moss, Steven C.

    2016-03-01

    Remarkable progress made in vertical cavity surface emitting lasers (VCSELs) emitting at 850 and 980 nm has led them to find an increasing number of applications in high speed data communications as well as in potential space satellite systems. However, little has been reported on reliability and failure modes of InGaAs VCSELs emitting at ~980 nm although it is crucial to understand failure modes and underlying degradation mechanisms in developing these VCSELs that exceed lifetime requirements for space missions. The active layer of commercial VCSELs that we studied consisted of two or three InGaAs quantum wells. The laser structures were fabricated into deep mesas followed by a steam oxidation process to form oxide-apertures for current and optical confinements. Our multi- mode VCSELs showed a laser threshold of ~ 0.5 mA at RT. Failures were generated via accelerated life-testing of VCSELs. For the present study, we report on failure mode analysis of degraded oxide-VCSELs using various techniques. We employed nondestructive techniques including electroluminescence (EL), optical beam induced current (OBIC), and electron beam induced current (EBIC) techniques as well as destructive techniques including focused ion beam (FIB) and high-resolution TEM techniques to study VCSELs that showed different degradation behaviors. Especially, we employed FIB systems to locally remove a portion of top-DBR mirrors of degraded VCSELs, which made it possible for our subsequent EBIC and OBIC techniques to locate damaged areas that were generated as a result of degradation processes and also for our HR-TEM technique to prepare TEM cross sections from damaged areas. Our nondestructive and destructive physical analysis results are reported including defect and structural analysis results from pre-aged VCSELs as well as from degraded VCSELs life-tested under different test conditions.

  4. Swept-source optical coherence tomography powered by a 1.3-μm vertical cavity surface emitting laser enables 2.3-mm-deep brain imaging in mice in vivo

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2015-01-01

    Abstract. We report noninvasive, in vivo optical imaging deep within a mouse brain by swept-source optical coherence tomography (SS-OCT), enabled by a 1.3-μm vertical cavity surface emitting laser (VCSEL). VCSEL SS-OCT offers a constant signal sensitivity of 105 dB throughout an entire depth of 4.25 mm in air, ensuring an extended usable imaging depth range of more than 2 mm in turbid biological tissue. Using this approach, we show deep brain imaging in mice with an open-skull cranial window preparation, revealing intact mouse brain anatomy from the superficial cerebral cortex to the deep hippocampus. VCSEL SS-OCT would be applicable to small animal studies for the investigation of deep tissue compartments in living brains where diseases such as dementia and tumor can take their toll. PMID:26447860

  5. Swept-source optical coherence tomography powered by a 1.3-μm vertical cavity surface emitting laser enables 2.3-mm-deep brain imaging in mice in vivo

    NASA Astrophysics Data System (ADS)

    Choi, Woo June; Wang, Ruikang K.

    2015-10-01

    We report noninvasive, in vivo optical imaging deep within a mouse brain by swept-source optical coherence tomography (SS-OCT), enabled by a 1.3-μm vertical cavity surface emitting laser (VCSEL). VCSEL SS-OCT offers a constant signal sensitivity of 105 dB throughout an entire depth of 4.25 mm in air, ensuring an extended usable imaging depth range of more than 2 mm in turbid biological tissue. Using this approach, we show deep brain imaging in mice with an open-skull cranial window preparation, revealing intact mouse brain anatomy from the superficial cerebral cortex to the deep hippocampus. VCSEL SS-OCT would be applicable to small animal studies for the investigation of deep tissue compartments in living brains where diseases such as dementia and tumor can take their toll.

  6. Bloch-wave engineering of quantum dot micropillars for cavity quantum electrodynamics experiments.

    PubMed

    Lermer, M; Gregersen, N; Dunzer, F; Reitzenstein, S; Höfling, S; Mørk, J; Worschech, L; Kamp, M; Forchel, A

    2012-02-03

    We have employed Bloch-wave engineering to realize submicron diameter high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced scattering loss leads to record-high vacuum Rabi splitting of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13, 600 and a splitting of 85  μeV with an estimated visibility v of 0.41 are observed for a small mode volume MP with a diameter d{c} of 850 nm.

  7. Characterization of commercially available vertical-cavity surface-emitting lasers tuned on Cs D1 line at 894.6  nm for miniature atomic clocks.

    PubMed

    Kroemer, Eric; Rutkowski, Jaroslaw; Maurice, Vincent; Vicarini, Rémy; Hafiz, Moustafa Abdel; Gorecki, Christophe; Boudot, Rodolphe

    2016-11-01

    We report on the metrological characterization of novel commercially available 894.6 nm vertical-cavity surface-emitting lasers (VCSELs), dedicated to Cs D1 line spectroscopy experiments. The thermal behavior of the VCSELs is reported, highlighting the existence of a minimum threshold current and maximum output power in the 55°C-60°C range. The laser relative intensity noise, measured to be -108  dB/Hz at 10 Hz Fourier frequency f for a laser power of 25 μW, is reduced with increased power. The VCSELs frequency noise is 108  Hz2/Hz at f=100  Hz. The spectral linewidth of the VCSELs is about 30 MHz. VCSELs injection current can be directly modulated at 4.596 GHz with microwave power in the range of -10 to +0  dBm to generate optical sidebands. A VCSEL was used in a microcell-based Cs atomic clock based on coherent population trapping. A preliminary clock short-term fractional frequency stability of 8×10-11τ-1/2 up to about 100 s is reported, demonstrating the suitability of these VCSELs for miniature atomic clock applications.

  8. A Novel, Free-Space Optical Interconnect Employing Vertical-Cavity Surface Emitting Laser Diodes and InGaAs Metal-Semiconductor-Metal Photodetectors for Gbit/s RF/Microwave Systems

    NASA Technical Reports Server (NTRS)

    Savich, Gregory R.; Simons, Rainee N.

    2006-01-01

    Emerging technologies and continuing progress in vertical-cavity surface emitting laser (VCSEL) diode and metal-semiconductor-metal (MSM) photodetector research are making way for novel, high-speed forms of optical data transfer in communication systems. VCSEL diodes operating at 1550 nm have only recently become commercially available, while MSM photodetectors are pushing the limits of contact lithography with interdigitated electrode widths reaching sub micron levels. We propose a novel, free-space optical interconnect operating at about 1Gbit/s utilizing VCSEL diodes and MSM photodetectors. We report on development, progress, and current work, which are as follows: first, analysis of the divergent behavior of VCSEL diodes for coupling to MSM photodetectors with a 50 by 50 m active area and second, the normalized frequency response of the VCSEL diode as a function of the modulating frequency. Third, the calculated response of MSM photodetectors with varying electrode width and spacing on the order of 1 to 3 m as well as the fabrication and characterization of these devices. The work presented here will lead to the formation and characterization of a fully integrated 1Gbit/s free-space optical interconnect at 1550 nm and demonstrates both chip level and board level functionality for RF/microwave digital systems.

  9. Single-photon emission at a rate of 143 MHz from a deterministic quantum-dot microlens triggered by a mode-locked vertical-external-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Schlehahn, A.; Gaafar, M.; Vaupel, M.; Gschrey, M.; Schnauber, P.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Stolz, W.; Rahimi-Iman, A.; Heindel, T.; Koch, M.; Reitzenstein, S.

    2015-07-01

    We report on the realization of a quantum dot (QD) based single-photon source with a record-high single-photon emission rate. The quantum light source consists of an InGaAs QD which is deterministically integrated within a monolithic microlens with a distributed Bragg reflector as back-side mirror, which is triggered using the frequency-doubled emission of a mode-locked vertical-external-cavity surface-emitting laser (ML-VECSEL). The utilized compact and stable laser system allows us to excite the single-QD microlens at a wavelength of 508 nm with a pulse repetition rate close to 500 MHz at a pulse width of 4.2 ps. Probing the photon statistics of the emission from a single QD state at saturation, we demonstrate single-photon emission of the QD-microlens chip with g(2)(0) < 0.03 at a record-high single-photon flux of (143 ± 16) MHz collected by the first lens of the detection system. Our approach is fully compatible with resonant excitation schemes using wavelength tunable ML-VECSELs, which will optimize the quantum optical properties of the single-photon emission in terms of photon indistinguishability.

  10. Single-photon emission at a rate of 143 MHz from a deterministic quantum-dot microlens triggered by a mode-locked vertical-external-cavity surface-emitting laser

    SciTech Connect

    Schlehahn, A.; Gschrey, M.; Schnauber, P.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Heindel, T. Reitzenstein, S.; Gaafar, M.; Vaupel, M.; Stolz, W.; Rahimi-Iman, A.; Koch, M.

    2015-07-27

    We report on the realization of a quantum dot (QD) based single-photon source with a record-high single-photon emission rate. The quantum light source consists of an InGaAs QD which is deterministically integrated within a monolithic microlens with a distributed Bragg reflector as back-side mirror, which is triggered using the frequency-doubled emission of a mode-locked vertical-external-cavity surface-emitting laser (ML-VECSEL). The utilized compact and stable laser system allows us to excite the single-QD microlens at a wavelength of 508 nm with a pulse repetition rate close to 500 MHz at a pulse width of 4.2 ps. Probing the photon statistics of the emission from a single QD state at saturation, we demonstrate single-photon emission of the QD-microlens chip with g{sup (2)}(0) < 0.03 at a record-high single-photon flux of (143 ± 16) MHz collected by the first lens of the detection system. Our approach is fully compatible with resonant excitation schemes using wavelength tunable ML-VECSELs, which will optimize the quantum optical properties of the single-photon emission in terms of photon indistinguishability.

  11. High-speed Si resonant cavity enhanced photodetectors and arrays

    NASA Astrophysics Data System (ADS)

    Ünlü, M. S.; Emsley, M. K.; Dosunmu, O. I.; Muller, P.; Leblebici, Y.

    2004-05-01

    Over the past decade a new family of optoelectronic devices has emerged whose performance is enhanced by placing the active device structure inside a Fabry-Perot resonant microcavity [P. E. Green, IEEE Spectrum 13 (2002)]. The increased optical field allows photodetectors to be made thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. We have demonstrated a variety of resonant cavity enhanced (RCE) photodetectors in compound semiconductors [B. Yang, J. D. Schaub, S. M. Csutak, D. J. Rogers, and J. C. Campbell, IEEE Photonics Technol. Lett. 15, 745 (2003)] and Si [M. K. Emsley, O. I. Dosunmu, and M. S. Ünlü, IEEE J. Selected Topics Quantum Electron. 8, 948 (2002)], operating at optical communication wavelengths ranging from 850 nm to 1550 nm. The focus of this article is on Si photodetectors and arrays. High bandwidth short distance communications standards are being developed based on parallel optical interconnect fiber arrays to meet the needs of increasing data rates of interchip communication in modern computer architecture. To ensure that this standard becomes an attractive option for computer systems, low cost components must be implemented on both the transmitting and receiving end of the fibers. To meet this low cost requirement silicon based receiver circuits are the most viable option, however, high speed, high efficiency silicon photodetectors present a technical challenge. Commercially reproducible silicon wafers with a high reflectance buried distributed Bragg reflector (DBR) have been designed and fabricated [M. K. Emsley, O. I. Dosunmu, and M. S. Ünlü, IEEE J. Selected Topics Quantum Electron. 8, 948 (2002)]. The substrates consist of a two-period, 90% reflecting, DBR fabricated using a double silicon-on-insulator (SOI) process. Resonant-cavity-enhanced (RCE) Si photodetectors have been fabricated with 40% quantum efficiency at 850 nm and a FWHM of 29 ps suitable for 10 Gbps data

  12. 850-nm hybrid fiber/free-space optical communications using orbital angular momentum modes.

    PubMed

    Jurado-Navas, Antonio; Tatarczak, Anna; Lu, Xiaofeng; Olmos, Juan José Vegas; Garrido-Balsells, José María; Monroy, Idelfonso Tafur

    2015-12-28

    Light beams can carry orbital angular momentum (OAM) associated to the helicity of their phasefronts. These OAM modes can be employed to encode information onto a laser beam for transmitting not only in a fiber link but also in a free-space optical (FSO) one. Regarding this latter scenario, FSO communications are considered as an alternative and promising mean complementing the traditional optical communications in many applications where the use of fiber cable is not justified. This next generation FSO communication systems have attracted much interest recently, and the inclusion of beams carrying OAM modes can be seen as an efficient solution to increase the capacity and the security in the link. In this paper, we discuss an experimental demonstration of a proposal for next generation FSO communication system where a light beam carrying different OAM modes and affected by ℳ turbulence is coupled to the multimode fiber link. In addition, we report a better and more robust behavior of higher order OAM modes when the intermodal dispersion is dominant in the fiber after exceeding its maximum range of operation.

  13. Chromospheric polarimetry through multiline observations of the 850-nm spectral region

    NASA Astrophysics Data System (ADS)

    Quintero Noda, C.; Shimizu, T.; Katsukawa, Y.; de la Cruz Rodríguez, J.; Carlsson, M.; Anan, T.; Oba, T.; Ichimoto, K.; Suematsu, Y.

    2017-02-01

    Future solar missions and ground-based telescopes aim to understand the magnetism of the solar chromosphere. We performed a supporting study in Quintero Noda et al. focused on the infrared Ca II 8542 Å line and we concluded that it is one of the best candidates because it is sensitive to a large range of atmospheric heights, from the photosphere to the middle chromosphere. However, we believe that it is worth trying to improve the results produced by this line observing additional spectral lines. In that regard, we examined the neighbourhood solar spectrum looking for spectral lines which could increase the sensitivity to the atmospheric parameters. Interestingly, we discovered several photospheric lines which greatly improve the photospheric sensitivity to the magnetic field vector. Moreover, they are located close to a second chromospheric line which also belongs to the Ca II infrared triplet, i.e. the Ca II 8498 Å line, and enhances the sensitivity to the atmospheric parameters at chromospheric layers. We conclude that the lines in the vicinity of the Ca II 8542 Å line not only increase its sensitivity to the atmospheric parameters at all layers, but also they constitute an excellent spectral window for chromospheric polarimetry.

  14. Metasurface external cavity laser

    SciTech Connect

    Xu, Luyao Curwen, Christopher A.; Williams, Benjamin S.; Hon, Philip W. C.; Itoh, Tatsuo; Chen, Qi-Sheng

    2015-11-30

    A vertical-external-cavity surface-emitting-laser is demonstrated in the terahertz range, which is based upon an amplifying metasurface reflector composed of a sub-wavelength array of antenna-coupled quantum-cascade sub-cavities. Lasing is possible when the metasurface reflector is placed into a low-loss external cavity such that the external cavity—not the sub-cavities—determines the beam properties. A near-Gaussian beam of 4.3° × 5.1° divergence is observed and an output power level >5 mW is achieved. The polarized response of the metasurface allows the use of a wire-grid polarizer as an output coupler that is continuously tunable.

  15. Visible Vertical Cavity Surface Emitting Lasers

    DTIC Science & Technology

    1993-01-01

    Van Nostrand Reinhold:New York, 1986). Baba, T ., Y. Yogo, K. Suzuki, F. Koyama, and K. Iga, "Near Room Temperature Continuous Wave Lasing...Alloys", Semiconductor Science Technology, 6, p. 27-31 (1991). Liedenbaum, C. T . H. F., A. Valster, A. L. G. J. Severens, and G. W. t ’ Hooft ...Chris P. Tigges, Harry T . Weaver, and Joel R. Wendt. Sincere appreciation also goes to the managers of the Microelectronics and Photonics Research Center

  16. Cavity magnomechanics

    PubMed Central

    Zhang, Xufeng; Zou, Chang-Ling; Jiang, Liang; Tang, Hong X.

    2016-01-01

    A dielectric body couples with electromagnetic fields through radiation pressure and electrostrictive forces, which mediate phonon-photon coupling in cavity optomechanics. In a magnetic medium, according to the Korteweg-Helmholtz formula, which describes the electromagnetic force density acting on a medium, magneostrictive forces should arise and lead to phonon-magnon interaction. We report such a coupled phonon-magnon system based on ferrimagnetic spheres, which we term as cavity magnomechanics, by analogy to cavity optomechanics. Coherent phonon-magnon interactions, including electromagnetically induced transparency and absorption, are demonstrated. Because of the strong hybridization of magnon and microwave photon modes and their high tunability, our platform exhibits new features including parametric amplification of magnons and phonons, triple-resonant photon-magnon-phonon coupling, and phonon lasing. Our work demonstrates the fundamental principle of cavity magnomechanics and its application as a new information transduction platform based on coherent coupling between photons, phonons, and magnons. PMID:27034983

  17. Control and elimination of cracking in aluminum(0.20) gallium(0.80) nitrogen using aluminum(x) gallium(1-x) nitrogen interlayers and application toward a near ultraviolet vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Waldrip, Karen Elizabeth

    -continuous wave optically pumped near ultraviolet vertical cavity surface emitting laser operating at 384 nm. This device employs a crack-free epitaxially grown mirror that consists of 120 pairs of Al 0.20Ga0.80N/GaN and is over five microns thick.

  18. Status of the ILC Crab Cavity Development

    SciTech Connect

    Burt, G.; Dexter, A.; Beard, C.; Goudket, P.; McIntosh, P.; Bellantoni, L.; Grimm, T.; Li, Z.; Xiao, L.; /SLAC

    2011-10-20

    The International Linear Collider (ILC) will require two dipole cavities to 'crab' the electron and positron bunches prior to their collision. It is proposed to use two 9 cell SCRF dipole cavities operating at a frequency of 3.9 GHz, with a transverse gradient of 3.8MV/m in order to provide the required transverse kick. Extensive numerical modelling of this cavity and its couplers has been performed. Aluminium prototypes have been manufactured and tested to measure the RF properties of the cavity and couplers. In addition single cell niobium prototypes have been manufactured and tested in a vertical cryostat. The International Collider (ILC) [1] collides bunches of electrons and positrons at a crossing angle of 14 mrad. The angle between these bunches causes a loss in luminosity due to geometric effects [2]. The luminosity lost from this geometric effect can be recovered by rotating the bunches into alignment prior to collision. One possible method of rotating the bunches is to use a crab cavity [3]. A crab cavity is a transverse defecting cavity, where the phase of the cavity is such that the head and tail of the bunch receive equal and opposite kicks. As the bunches are only 500 nm wide in the horizontal plane, the cavity phase must be strictly controlled to avoid the bunch centre being deflected too much. In order to keep the phase stability within the required limits it is required that the cavity be superconducting to avoid thermal effects in both the cavity and its RF source. At the location of the crab cavity in the ILC there is only 23 cm separation between the centre of the cavity and the extraction line, hence the cavity must be small enough to fit in this space. This, along with the difficulty of making high frequency SRF components, set the frequency of the cavity to 3.9 GHz.

  19. Mounting system for optical frequency reference cavities

    NASA Technical Reports Server (NTRS)

    Notcutt, Mark (Inventor); Hall, John L. (Inventor); Ma, Long-Sheng (Inventor)

    2008-01-01

    A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.

  20. THE VERTICAL

    NASA Technical Reports Server (NTRS)

    Albert, Stephen L.; Spencer, Jeffrey B.

    1994-01-01

    'THE VERTICAL' computer keyboard is designed to address critical factors which contribute to Repetitive Motion Injuries (RMI) (including Carpal Tunnel Syndrome) in association with computer keyboard usage. This keyboard splits the standard QWERTY design into two halves and positions each half 90 degrees from the desk. In order to access a computer correctly. 'THE VERTICAL' requires users to position their bodies in optimal alignment with the keyboard. The orthopaedically neutral forearm position (with hands palms-in and thumbs-up) reduces nerve compression in the forearm. The vertically arranged keypad halves ameliorate onset occurrence of keyboard-associated RMI. By utilizing visually-reference mirrored mylar surfaces adjustable to the user's eye, the user is able to readily reference any key indicia (reversed) just as they would on a conventional keyboard. Transverse adjustability substantially reduces cumulative musculoskeletal discomfort in the shoulders. 'THE VERTICAL' eliminates the need for an exterior mouse by offering a convenient finger-accessible curser control while the hands remain in the vertically neutral position. The potential commercial application for 'THE VERTICAL' is enormous since the product can effect every person who uses a computer anywhere in the world. Employers and their insurance carriers are spending hundreds of millions of dollars per year as a result of RMI. This keyboard will reduce the risk.

  1. Terrace-microsphere lasers: spherical cavity lasers for multiwavelength emission

    NASA Astrophysics Data System (ADS)

    Uehara, Hiyori; Yano, Tetsuji; Shibata, Shuichi

    2010-02-01

    We have successfully made terrace-microspheres for laser emission: micrometer size spherical cavity laser having terrace shaped pumping light entrance. "Terrace-microsphere" is a high refractive index glass sphere (nD=1.93) of 30μm in diameter with terrace portion of organic-inorganic materials. The glass sphere is in BaO-SiO2-TiO2 glass system and contain a few ppm of Nd3+. Organic-inorganic hybrid materials of refractive index nD=1.45 were prepared by sol-gel technique using 3-methacryloxypropyltrimethoxysilane and tetramethoxysilane as starting materials. To make terrace portion, a pico-liter of sol droplet was supplied with a micro-capillary into the boundary between a glass sphere and a Teflon sheet. The sol-derived part attached to a sphere showed the flat portion like a terrace structure. The terrace-microspheres were pumped with a tunable CW Ti:sapphire laser (λ=700nm-850nm) for choosing the suitable pumping wavelengths to WGMs. Pumping the terrace portion at around 800nm wavelength, strong resonances due to WGMs were demonstrated. The resonances originated from Raman scattering and Nd3+ fluorescence were observed at 840-880nm and 880-940nm wavelength region respectively. Consequently, we can show the potential application for a multi-wavelength laser (about 100 lines) at the extended wavelength range (840-940nm) in the near-infrared. Stimulated Raman emission of WGMs was performed with threshold of 4mW.

  2. What's a Cavity?

    MedlinePlus

    ... cavity (say: KA-vuh-tee) develops when a tooth decays (say: dih-KAZE), or breaks down. A cavity ... and deeper over time. Cavities are also called dental caries (say: KARE-eez), and if you have a ...

  3. Dual frequency optical cavity

    DOEpatents

    George, E.V.; Schipper, J.F.

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a T configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  4. Dual frequency optical cavity

    DOEpatents

    George, E. Victor; Schipper, John F.

    1985-01-01

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a "T" configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  5. Design of half-reentrant SRF cavities

    NASA Astrophysics Data System (ADS)

    Meidlinger, M.; Grimm, T. L.; Hartung, W.

    2006-07-01

    The shape of a TeSLA inner cell can be improved to lower the peak surface magnetic field at the expense of a higher peak surface electric field by making the cell reentrant. Such a single-cell cavity was designed and tested at Cornell, setting a world record accelerating gradient [V. Shemelin et al., An optimized shape cavity for TESLA: concept and fabrication, 11th Workshop on RF Superconductivity, Travemünde, Germany, September 8-12, 2003; R. Geng, H. Padamsee, Reentrant cavity and first test result, Pushing the Limits of RF Superconductivity Workshop, Argonne National Laboratory, September 22-24, 2004]. However, the disadvantage to a cavity is that liquids become trapped in the reentrant portion when it is vertically hung during high pressure rinsing. While this was overcome for Cornell’s single-cell cavity by flipping it several times between high pressure rinse cycles, this may not be feasible for a multi-cell cavity. One solution to this problem is to make the cavity reentrant on only one side, leaving the opposite wall angle at six degrees for fluid drainage. This idea was first presented in 2004 [T.L. Grimm et al., IEEE Transactions on Applied Superconductivity 15(6) (2005) 2393]. Preliminary designs of two new half-reentrant (HR) inner cells have since been completed, one at a high cell-to-cell coupling of 2.1% (high- kcc HR) and the other at 1.5% (low- kcc HR). The parameters of a HR cavity are comparable to a fully reentrant cavity, with the added benefit that a HR cavity can be easily cleaned with current technology.

  6. Mode analysis of photonic crystal L3 cavities in self-suspended lithium niobate membranes

    SciTech Connect

    Diziain, Séverine Geiss, Reinhard; Zilk, Matthias; Schrempel, Frank; Kley, Ernst-Bernhard; Pertsch, Thomas; Tünnermann, Andreas

    2013-12-16

    We report on a multimodal analysis of photonic crystal L3 cavities milled in lithium niobate free-standing membranes. The classical L3 cavity geometry is compared to an L3 cavity containing a second lattice superimposed on the primary one. Those two different geometries are investigated in terms of vertical radiation and quality (Q) factor for each mode of the cavities. Depending on the cavity geometry, some modes undergo an enhancement of their vertical radiation into small angles while other modes experience a higher Q factor. Experimental characterizations are corroborated by three-dimensional finite difference time domain simulations.

  7. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  8. Electromagnetic SCRF Cavity Tuner

    SciTech Connect

    Kashikhin, V.; Borissov, E.; Foster, G.W.; Makulski, A.; Pischalnikov, Y.; Khabiboulline, T.; /Fermilab

    2009-05-01

    A novel prototype of SCRF cavity tuner is being designed and tested at Fermilab. This is a superconducting C-type iron dominated magnet having a 10 mm gap, axial symmetry, and a 1 Tesla field. Inside the gap is mounted a superconducting coil capable of moving {+-} 1 mm and producing a longitudinal force up to {+-} 1.5 kN. The static force applied to the RF cavity flanges provides a long-term cavity geometry tuning to a nominal frequency. The same coil powered by fast AC current pulse delivers mechanical perturbation for fast cavity tuning. This fast mechanical perturbation could be used to compensate a dynamic RF cavity detuning caused by cavity Lorentz forces and microphonics. A special configuration of magnet system was designed and tested.

  9. Cavity enhanced terahertz modulation

    SciTech Connect

    Born, N.; Scheller, M.; Moloney, J. V.; Koch, M.

    2014-03-10

    We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%.

  10. Optically measuring interior cavities

    SciTech Connect

    Stone, Gary Franklin

    2008-12-21

    A method of measuring the three-dimensional volume or perimeter shape of an interior cavity includes the steps of collecting a first optical slice of data that represents a partial volume or perimeter shape of the interior cavity, collecting additional optical slices of data that represents a partial volume or perimeter shape of the interior cavity, and combining the first optical slice of data and the additional optical slices of data to calculate of the three-dimensional volume or perimeter shape of the interior cavity.

  11. High efficiency oxide confined vertical cavity surface emitting lasers

    SciTech Connect

    Lear, K.L.; Kilcoyne, S.P.; Schneider, R.P. Jr.; Choquette, K.D.; Hadley, G.R.

    1995-08-01

    Optical loss is studied in devices with either two aligned apertures above and below the active region or with a single effective aperture above the active region. The latter exhibit slope efficiencies of up to 1 W/A.

  12. Optical glucose monitoring using vertical cavity surface emitting lasers (VCSELs)

    NASA Astrophysics Data System (ADS)

    Talebi Fard, Sahba; Hofmann, Werner; Talebi Fard, Pouria; Kwok, Ezra; Amann, Markus-Christian; Chrostowski, Lukas

    2009-08-01

    Diabetes Mellitus is a common chronic disease that has become a public health issue. Continuous glucose monitoring improves patient health by stabilizing the glucose levels. Optical methods are one of the painless and promising methods that can be used for blood glucose predictions. However, having accuracies lower than what is acceptable clinically has been a major concern. Using lasers along with multivariate techniques such as Partial Least Square (PLS) can improve glucose predictions. This research involves investigations for developing a novel optical system for accurate glucose predictions, which leads to the development of a small, low power, implantable optical sensor for diabetes patients.

  13. Different optical properties in different periodic slot cavity geometrical morphologies

    NASA Astrophysics Data System (ADS)

    Zhou, Jing; Shen, Meng; Du, Lan; Deng, Caisong; Ni, Haibin; Wang, Ming

    2016-09-01

    In this paper, optical properties of two-dimensional periodic annular slot cavity arrays in hexagonal close-packing on a silica substrate are theoretically characterized by finite difference time domain (FDTD) simulation method. By simulating reflectance spectra, electric field distribution, and charge distribution, we confirm that multiple cylindrical surface plasmon resonances can be excited in annular inclined slot cavities by linearly polarized light, in which the four reflectance dips are attributed to Fabry-Perot cavity resonances in the coaxial cavity. A coaxial waveguide mode TE11 will exist in these annular cavities, and the wavelengths of these reflectance dips are effectively tailored by changing the geometrical pattern of slot cavity and the dielectric materials filled in the cavities. These resonant wavelengths are localized in annular cavities with large electric field enhancement and dissipate gradually due to metal loss. The formation of an absorption peak can be explained from the aspect of phase matching conditions. We observed that the proposed structure can be tuned over the broad spectral range of 600-4000 nm by changing the outer and inner radii of the annular gaps, gap surface topography. Meanwhile, different lengths of the cavity may cause the shift of resonance dips. Also, we study the field enhancement at different vertical locations of the slit. In addition, dielectric materials filling in the annular gaps will result in a shift of the resonance wavelengths, which make the annular cavities good candidates for refractive index sensors. The refractive index sensitivity of annular cavities can also be tuned by the geometry size and the media around the cavity. Annular cavities with novel applications can be implied as surface enhanced Raman spectra substrates, refractive index sensors, nano-lasers, and optical trappers. Project supported by the National Natural Science Foundation of China (Grant No. 61178044), the Natural Science Foundation

  14. What's a Cavity?

    MedlinePlus

    ... and deeper over time. Cavities are also called dental caries (say: KARE-eez), and if you have a cavity, it's important to get it repaired. But why would your ... and when plaque clings to your teeth, the acids can eat away at the outermost ...

  15. CAVITY EXCITATION CIRCUIT

    DOEpatents

    Franck, J.V.

    1959-10-20

    An electronic oscillator is described for energizing a resonant cavity and to a system for stabilizing the operatin g frequency of the oscillator at the particular frequency necessary to establish a particular preferred field configuration or mode in the cavity, in this instance a linear accelerator. A freely rnnning oscillator has an output coupled to a resonant cavity wherein a field may be built up at any one of several adjacent frequencies. A pickup loop in the cavity is suitably shielded and positioned in the cavity so that only energy at the panticular desired frequency is fed back to stabilize the oscillator. A phase and gain control is in cluded in the feedback line.

  16. Passivated niobium cavities

    DOEpatents

    Myneni, Ganapati Rao; Hjorvarsson, Bjorgvin; Ciovati, Gianluigi

    2006-12-19

    A niobium cavity exhibiting high quality factors at high gradients is provided by treating a niobium cavity through a process comprising: 1) removing surface oxides by plasma etching or a similar process; 2) removing hydrogen or other gases absorbed in the bulk niobium by high temperature treatment of the cavity under ultra high vacuum to achieve hydrogen outgassing; and 3) assuring the long term chemical stability of the niobium cavity by applying a passivating layer of a superconducting material having a superconducting transition temperature higher than niobium thereby reducing losses from electron (cooper pair) scattering in the near surface region of the interior of the niobium cavity. According to a preferred embodiment, the passivating layer comprises niobium nitride (NbN) applied by reactive sputtering.

  17. Theory and Practice of Cavity RF Test Systems

    SciTech Connect

    Tom Powers

    2006-08-28

    Over the years Jefferson Lab staff members have performed about 2500 cold cavity tests on about 500 different superconducting cavities. Most of these cavities were later installed in 73 different cryomodules, which were used in three different accelerators. All of the cavities were tested in our vertical test area. About 25% of the cryomodules were tested in our cryomodule test facility and later commissioned in an accelerator. The remainder of the cryomodules were tested and commissioned after they were installed in their respective accelerator. This paper is an overview which should provide a practical background in the RF systems used to test the cavities as well as provide the mathematics necessary to convert the raw pulsed or continuous wave RF signals into useful information such as gradient, quality factor, RF-heat loads and loaded Q?s. Additionally, I will provide the equations necessary for determining the measurement error associated with these values.

  18. Magnetic Flux Expulsion Studies in Niobium SRF Cavities

    SciTech Connect

    Posen, Sam; Checchin, Mattia; Crawford, Anthony; Grassellino, Anna; Martinello, Martina; Melnychuk, Oleksandr; Romanenko, Alexander; Sergatskov, Dmitri; Trenikhina, Yulia

    2016-06-01

    With the recent discovery of nitrogen doping treatment for SRF cavities, ultra-high quality factors at medium accelerating fields are regularly achieved in vertical RF tests. To preserve these quality factors into the cryomodule, it is important to consider background magnetic fields, which can become trapped in the surface of the cavity during cooldown and cause Q₀ degradation. Building on the recent discovery that spatial thermal gradients during cooldown can significantly improve expulsion of magnetic flux, a detailed study was performed of flux expulsion on two cavities with different furnace treatments that are cooled in magnetic fields amplitudes representative of what is expected in a realistic cryomodule. In this contribution, we summarize these cavity results, in order to improve understanding of the impact of flux expulsion on cavity performance.

  19. Lithographic wavelength control of an external cavity laser with a silicon photonic crystal cavity-based resonant reflector.

    PubMed

    Liles, Alexandros A; Debnath, Kapil; O'Faolain, Liam

    2016-03-01

    We report the experimental demonstration of a new design for external cavity hybrid lasers consisting of a III-V semiconductor optical amplifier (SOA) with fiber reflector and a photonic crystal (PhC)-based resonant reflector on SOI. The silicon reflector is composed of an SU8 polymer bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and side-mode suppression ratios of more than 25 dB.

  20. Hydroforming of elliptical cavities

    NASA Astrophysics Data System (ADS)

    Singer, W.; Singer, X.; Jelezov, I.; Kneisel, P.

    2015-02-01

    Activities of the past several years in developing the technique of forming seamless (weldless) cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with results of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients Eacc up to 35 MV /m after buffered chemical polishing (BCP) and up to 42 MV /m after electropolishing (EP). More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients Eacc of 30 - 35 MV /m were measured after BCP and Eacc up to 40 MV /m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of Eacc=30 - 35 MV /m . One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and double-cell cavities of the TESLA shape have been

  1. Tuned optical cavity magnetometer

    DOEpatents

    Okandan, Murat; Schwindt, Peter

    2010-11-02

    An atomic magnetometer is disclosed which utilizes an optical cavity formed from a grating and a mirror, with a vapor cell containing an alkali metal vapor located inside the optical cavity. Lasers are used to magnetically polarize the alkali metal vapor and to probe the vapor and generate a diffracted laser beam which can be used to sense a magnetic field. Electrostatic actuators can be used in the magnetometer for positioning of the mirror, or for modulation thereof. Another optical cavity can also be formed from the mirror and a second grating for sensing, adjusting, or stabilizing the position of the mirror.

  2. Hydroforming of elliptical cavities

    DOE PAGES

    Singer, W.; Singer, X.; Jelezov, I.; ...

    2015-02-27

    Activities of the past several years in developing the technique of forming seamless (weldless) cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with resultsmore » of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients Eacc up to 35 MV/m after buffered chemical polishing (BCP) and up to 42 MV/m after electropolishing (EP). More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients Eacc of 30–35 MV/m were measured after BCP and Eacc up to 40 MV/m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of Eacc = 30–35 MV/m. One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and double-cell cavities of the TESLA shape have

  3. Hydroforming of elliptical cavities

    SciTech Connect

    Singer, W.; Singer, X.; Jelezov, I.; Kneisel, Peter

    2015-02-27

    Activities of the past several years in developing the technique of forming seamless (weldless) cavity cells by hydroforming are summarized. An overview of the technique developed at DESY for the fabrication of single cells and multicells of the TESLA cavity shape is given and the major rf results are presented. The forming is performed by expanding a seamless tube with internal water pressure while simultaneously swaging it axially. Prior to the expansion the tube is necked at the iris area and at the ends. Tube radii and axial displacements are computer controlled during the forming process in accordance with results of finite element method simulations for necking and expansion using the experimentally obtained strain-stress relationship of tube material. In cooperation with industry different methods of niobium seamless tube production have been explored. The most appropriate and successful method is a combination of spinning or deep drawing with flow forming. Several single-cell niobium cavities of the 1.3 GHz TESLA shape were produced by hydroforming. They reached accelerating gradients Eacc up to 35 MV/m after buffered chemical polishing (BCP) and up to 42 MV/m after electropolishing (EP). More recent work concentrated on fabrication and testing of multicell and nine-cell cavities. Several seamless two- and three-cell units were explored. Accelerating gradients Eacc of 30–35 MV/m were measured after BCP and Eacc up to 40 MV/m were reached after EP. Nine-cell niobium cavities combining three three-cell units were completed at the company E. Zanon. These cavities reached accelerating gradients of Eacc = 30–35 MV/m. One cavity is successfully integrated in an XFEL cryomodule and is used in the operation of the FLASH linear accelerator at DESY. Additionally the fabrication of bimetallic single-cell and multicell NbCu cavities by hydroforming was successfully developed. Several NbCu clad single-cell and double

  4. Electromechanical tuning of vertically-coupled photonic crystal nanobeams.

    PubMed

    Midolo, L; Yoon, S N; Pagliano, F; Xia, T; van Otten, F W M; Lermer, M; Höfling, S; Fiore, A

    2012-08-13

    We present the design, the fabrication and the characterization of a tunable one-dimensional (1D) photonic crystal cavity (PCC) etched on two vertically-coupled GaAs nanobeams. A novel fabrication method which prevents their adhesion under capillary forces is introduced. We discuss a design to increase the flexibility of the structure and we demonstrate a large reversible and controllable electromechanical wavelength tuning (> 15 nm) of the cavity modes.

  5. CIRCULAR CAVITY SLOT ANTENNA

    DOEpatents

    Kerley, P.L.

    1959-01-01

    A small-size antenna having a doughnut-shaped field pattern and which can act both as an antenna and a resonant circuit is described. The antenna is of the slotted type and comprises a resonant cavity with a center hole. A circular slot is provided in one wall of the cavity concentric with the hole and a radio frequency source is connected across the slot. The pattern and loading of the antenna are adjusted by varying the position and shape of a center element slidably disposed within the hole and projecting from the slotted side of the resonant cavity. The disclosed structure may also be used to propagate the oscillator signal down a transniission line by replacing the center element with one leg of the transmission line in a spaced relation from the walls of the cavity.

  6. Engineering design of vertical test stand cryostat

    SciTech Connect

    Suhane, S.K.; Sharma, N.K.; Raghavendra, S.; Joshi, S.C.; Das, S.; Kush, P.K.; Sahni, V.C.; Gupta, P.D.; Sylvester, C.; Rabehl, R.; Ozelis, J.; /Fermilab

    2011-03-01

    Under Indian Institutions and Fermilab collaboration, Raja Ramanna Centre for Advanced Technology and Fermi National Accelerator Laboratory are jointly developing 2K Vertical Test Stand (VTS) cryostats for testing SCRF cavities at 2K. The VTS cryostat has been designed for a large testing aperture of 86.36 cm for testing of 325 MHz Spoke resonators, 650 MHz and 1.3 GHz multi-cell SCRF cavities for Fermilab's Project-X. Units will be installed at Fermilab and RRCAT and used to test cavities for Project-X. A VTS cryostat comprises of liquid helium (LHe) vessel with internal magnetic shield, top insert plate equipped with cavity support stand and radiation shield, liquid nitrogen (LN{sub 2}) shield and vacuum vessel with external magnetic shield. The engineering design and analysis of VTS cryostat has been carried out using ASME B&PV Code and Finite Element Analysis. Design of internal and external magnetic shields was performed to limit the magnetic field inside LHe vessel at the cavity surface <1 {micro}T. Thermal analysis for LN{sub 2} shield has been performed to check the effectiveness of LN{sub 2} cooling and for compliance with ASME piping code allowable stresses.

  7. STANDARDIZATION OF CEBAF 12 GEV UPGRADE CAVITY TESTING

    SciTech Connect

    Tiffany Bass, G. Davis, Christiana Wilson, Mircea Stirbet

    2012-07-01

    CEBAF 12GeV upgrade project includes 80 new 7-cell cavities to form 10 cryomodules. Each cavity underwent RF qualification at 2.07K using a high power accelerating gradient test and an HOM survey in Jefferson Lab's Vertical Testing Area (VTA) before cavity string assembly. In order to ensure consistently high quality data, updated cavity testing procedures and analysis were implemented and used by a group of VTA operators. For high power tests, a cavity testing procedure was developed and used in conjunction with a LabVIEW program to collect the test data. Additionally while the cavity was at 2.07K, an HOM survey was performed using a network analyzer and a combination of Excel and Mathematica programs. Data analysis was standardized and an online logbook, Pansophy, was used for data storage and mining. The Pansophy system allowed test results to be easily summarized and searchable across all cavity tests. In this presentation, the CEBAF 12GeV upgrade cavity testing procedure, method for data analysis, and results reporting results will be discussed.

  8. Results of Cavity Series Fabrication at Jefferson Laboratory for the Cryomodule “R100”

    SciTech Connect

    F. Marhauser, W.A. Clemens, M.A. Drury, D. Forehand, J. Henry, S. Manning, R.B. Overton, R.S. Williams

    2011-09-01

    A series production of eight superconducting RF cavities for the cryomodule R100 was conducted at JLab in 2010. The cavities underwent chemical post-processing prior to vertical high power testing and routinely exceeded the envisaged performance specifications. After cryomodule assembly, cavities were successfully high power acceptance tested. In this paper, we present the achievements paving the way for the first demonstration of 100 MV (and beyond) in a single cryomodule to be operated at CEBAF.

  9. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, R.N.; Martin, J.; Paldus, B.A.; Xie, J.

    1999-06-15

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS). 6 figs.

  10. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, Richard N.; Martin, Juergen; Paldus, Barbara A.; Xie, Jinchun

    1999-01-01

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS).

  11. Vertical bounce of two vertically aligned balls

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2007-11-01

    When a tennis ball rests on top of a basketball and both drop to the floor together, the tennis ball is projected vertically at high speed. A mass-spring model of the impact, as well as air track data, suggest that the tennis ball should be projected at relatively low speed. Measurements of the forces on each ball and the bounce of vertically aligned superballs are used to resolve the discrepancy.

  12. Video Toroid Cavity Imager

    DOEpatents

    Gerald, II, Rex E.; Sanchez, Jairo; Rathke, Jerome W.

    2004-08-10

    A video toroid cavity imager for in situ measurement of electrochemical properties of an electrolytic material sample includes a cylindrical toroid cavity resonator containing the sample and employs NMR and video imaging for providing high-resolution spectral and visual information of molecular characteristics of the sample on a real-time basis. A large magnetic field is applied to the sample under controlled temperature and pressure conditions to simultaneously provide NMR spectroscopy and video imaging capabilities for investigating electrochemical transformations of materials or the evolution of long-range molecular aggregation during cooling of hydrocarbon melts. The video toroid cavity imager includes a miniature commercial video camera with an adjustable lens, a modified compression coin cell imager with a fiat circular principal detector element, and a sample mounted on a transparent circular glass disk, and provides NMR information as well as a video image of a sample, such as a polymer film, with micrometer resolution.

  13. Vertical axis wind turbines

    DOEpatents

    Krivcov, Vladimir [Miass, RU; Krivospitski, Vladimir [Miass, RU; Maksimov, Vasili [Miass, RU; Halstead, Richard [Rohnert Park, CA; Grahov, Jurij [Miass, RU

    2011-03-08

    A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

  14. Multiple scattering of surface waves by cavities in a half-space

    SciTech Connect

    Phan, Haidang; Cho, Younho; Ju, Taeho; Achenbach, Jan D.

    2014-02-18

    Scattering of surface waves from multiple two-dimensional cavities at the surface of a homogenous, isotropic, linearly elastic half-space is analyzed in this work. For the case of multiple cavities, the scattered field is shown to be equivalent to the total radiation from the distributions of tractions, calculated from the incident wave, over the surfaces of the cavities. The multiple-scattering model is obtained from known single-scattering calculation for a cavity by the use of the self-consistent method. The second order approximation to the multiple-scattering problem by a random distribution of cavities is then considered and solved analytically. The vertical displacement at some distance from the cavities is calculated and verified by the solution of the same problem obtained by the boundary element method (BEM). The analytical and BEM results are graphically displayed and show good agreement when the depths of the cavities are small compared to the wavelength.

  15. Craters and Granular Jets Generated by Underground Cavity Collapse

    NASA Astrophysics Data System (ADS)

    Loranca-Ramos, F. E.; Carrillo-Estrada, J. L.; Pacheco-Vázquez, F.

    2015-07-01

    We study experimentally the cratering process due to the explosion and collapse of a pressurized air cavity inside a sand bed. The process starts when the cavity breaks and the liberated air then rises through the overlying granular layer and produces a violent eruption; it depressurizes the cavity and, as the gas is released, the sand sinks under gravity, generating a crater. We find that the crater dimensions are totally determined by the cavity volume; the pressure does not affect the morphology because the air is expelled vertically during the eruption. In contrast with impact craters, the rim is flat and, regardless of the cavity shape, it evolves into a circle as the cavity depth increases or if the chamber is located deep enough inside the bed, which could explain why most of the subsidence craters observed in nature are circular. Moreover, for shallow spherical cavities, a collimated jet emerges from the collision of sand avalanches that converge concentrically at the bottom of the depression, revealing that collapse under gravity is the main mechanism driving the jet formation.

  16. Filling a Conical Cavity

    NASA Astrophysics Data System (ADS)

    Nye, Kyle; Eslam-Panah, Azar

    2016-11-01

    Root canal treatment involves the removal of infected tissue inside the tooth's canal system and filling the space with a dense sealing agent to prevent further infection. A good root canal treatment happens when the canals are filled homogeneously and tightly down to the root apex. Such a tooth is able to provide valuable service for an entire lifetime. However, there are some examples of poorly performed root canals where the anterior and posterior routes are not filled completely. Small packets of air can be trapped in narrow access cavities when restoring with resin composites. Such teeth can cause trouble even after many years and lead the conditions like acute bone infection or abscesses. In this study, the filling of dead-end conical cavities with various liquids is reported. The first case studies included conical cavity models with different angles and lengths to visualize the filling process. In this investigation, the rate and completeness at which a variety of liquids fill the cavity were observed to find ideal conditions for the process. Then, a 3D printed model of the scaled representation of a molar with prepared post spaces was used to simulate the root canal treatment. The results of this study can be used to gain a better understanding of the restoration for endodontically treated teeth.

  17. Melatonin and Oral Cavity

    PubMed Central

    Cengiz, Murat İnanç; Cengiz, Seda; Wang, Hom-Lay

    2012-01-01

    While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers. PMID:22792106

  18. Thermal Impacts of Vertical Greenery Systems

    NASA Astrophysics Data System (ADS)

    Safikhani, Tabassom; Abdullah, Aminatuzuhariah Megat; Ossen, Dilshan Remaz; Baharvand, Mohammad

    2014-12-01

    - Using vertical greenery systems to reduce heat transmission is becoming more common in modern architecture. Vertical greenery systems are divided into two main categories; green facades and living walls. This study aims to examine the thermal performance of vertical greenery systems in hot and humid climates. An experimental procedure was used to measure indoor temperature and humidity. These parameters were also measured for the gap between the vertical greenery systems and wall surfaces. Three boxes were used as small-scale rooms. Two boxes were provided with either a living wall or a green facade and one box did not have any greenery (benchmark). Blue Trumpet Vine was used in the vertical greenery systems. The data were recorded over the course of three sunny days in April 2013. An analyses of the results showed that the living wall and green facade reduced indoor temperature up to 4.0 °C and 3.0 °C, respectively. The living wall and green facade also reduced cavity temperatures by 8.0 °C and 6.5 °C, respectively.

  19. Broadband cavity electromagnetically induced transparency

    SciTech Connect

    Wei Xiaogang; Wang Yanhua; Zhang Jiepeng; Zhu Yifu

    2011-10-15

    Cavity electromagnetically induced transparency (EIT) is created in a three-level atomic system confined in a cavity and coupled to a free-space control laser and is manifested as a narrow transmission peak of a probe laser coupled into the cavity mode and tuned to the two-photon Raman resonance with the control laser. Cavity EIT can be observed with a control laser detuned from the atomic transition frequency in a range limited by the vacuum Rabi splitting of two cavity-atom normal modes. This leads to the broadband cavity EIT obtained in the coupled-cavity-atom system with a free-space, broadband control laser. We report an experimental observation of broadband cavity EIT in cold Rb atoms with a frequency-modulated control laser and discuss its application in multichannel and multifrequency light memory.

  20. First attempt of at-cavity cryogenic X-ray detection in a CEBAF cryomodule for field emission monitoring

    SciTech Connect

    Geng, Rongli; Daly, Edward; Drury, Michael; Palczewski, Ari

    2015-09-01

    We report on the first result of at-cavity X-ray detection in a CEBAF cryomodule for field emission monitoring. In the 8-cavity cryomodule F100, two silicon diodes were installed near the end flange of each cavity. Each cavity was individually tested during the cryomodule test in JLab’s cryomodule test facility. The behaviors of these at-cavity cryogenic X-ray detectors were compared with those of the standard ‘in air’ Geiger-Muller (G-M) tubes. Our initial experiments establish correlation between X-ray response of near diodes and the field emission source cavity in the 8-cavity string. For two out of these eight cavities, we also carried out at-cavity X-ray detection experiment during their vertical testing. The aim is to track field emission behavior uniquely from vertical cavity testing to horizontal cavity testing in the cryomodule. These preliminary results confirmed our expectation and warrant further effort toward the establishment of permanent at-cavity cryogenic X-ray detection for SRF development and operation.

  1. Compressibility effects in the shear layer over a rectangular cavity

    DOE PAGES

    Beresh, Steven J.; Wagner, Justin L.; Casper, Katya M.

    2016-10-26

    we studied the influence of compressibility on the shear layer over a rectangular cavity of variable width in a free stream Mach number range of 0.6–2.5 using particle image velocimetry data in the streamwise centre plane. As the Mach number increases, the vertical component of the turbulence intensity diminishes modestly in the widest cavity, but the two narrower cavities show a more substantial drop in all three components as well as the turbulent shear stress. Furthermore, this contrasts with canonical free shear layers, which show significant reductions in only the vertical component and the turbulent shear stress due to compressibility.more » The vorticity thickness of the cavity shear layer grows rapidly as it initially develops, then transitions to a slower growth rate once its instability saturates. When normalized by their estimated incompressible values, the growth rates prior to saturation display the classic compressibility effect of suppression as the convective Mach number rises, in excellent agreement with comparable free shear layer data. The specific trend of the reduction in growth rate due to compressibility is modified by the cavity width.« less

  2. Compressibility effects in the shear layer over a rectangular cavity

    SciTech Connect

    Beresh, Steven J.; Wagner, Justin L.; Casper, Katya M.

    2016-10-26

    we studied the influence of compressibility on the shear layer over a rectangular cavity of variable width in a free stream Mach number range of 0.6–2.5 using particle image velocimetry data in the streamwise centre plane. As the Mach number increases, the vertical component of the turbulence intensity diminishes modestly in the widest cavity, but the two narrower cavities show a more substantial drop in all three components as well as the turbulent shear stress. Furthermore, this contrasts with canonical free shear layers, which show significant reductions in only the vertical component and the turbulent shear stress due to compressibility. The vorticity thickness of the cavity shear layer grows rapidly as it initially develops, then transitions to a slower growth rate once its instability saturates. When normalized by their estimated incompressible values, the growth rates prior to saturation display the classic compressibility effect of suppression as the convective Mach number rises, in excellent agreement with comparable free shear layer data. The specific trend of the reduction in growth rate due to compressibility is modified by the cavity width.

  3. Offset vertical radar profiling

    USGS Publications Warehouse

    Witten, A.; Lane, J.

    2003-01-01

    Diffraction tomography imaging was applied to VRP data acquired by vertically moving a receiving antenna in a number of wells. This procedure simulated a vertical downhole receiver array. Similarly, a transmitting antenna was sequentially moved along a series of radial lines extending outward from the receiver wells. This provided a sequence of multistatic data sets and, from each data set, a two-dimensional vertical cross-sectional image of spatial variations in wave speed was reconstructed.

  4. Vertical Axis Wind Turbine

    SciTech Connect

    Homicz, Greg

    2002-04-01

    Blade fatigue life is an important element in determining the economic viability of the Vertical-Axis Wind Turbine (VAWT). VAWT-SAL Vertical Axis Wind Turbine- Stochastic Aerodynamic Loads Ver 3.2 numerically simulates the stochastic (random0 aerodynamic loads of the Vertical-Axis Wind Turbine (VAWT) created by the atomspheric turbulence. The program takes into account the rotor geometry, operating conditions, and assumed turbulence properties.

  5. Single-cavity SLED device

    SciTech Connect

    Lippmann, B.A.

    1984-09-01

    The conventional SLED device used at SLAC requires two cavities. However, the same effect can be obtained with a single cavity; the theory and operation of the device is the same, only the hardware is changed. The single-cavity device is described here.

  6. [Myxofibrosarcoma in the abdominal cavity].

    PubMed

    Janů, F

    2016-01-01

    A number of benign and malignant tumors may develop in the abdominal cavity. Sarcomas are rather rare tumors of the abdominal cavity. They are often diagnosed at advanced growth stages as their local growth can cause clinical problems to the patients. The author presents a case report of myxofibrosarcoma in the abdominal cavity.Key words: myxofibrosarcoma.

  7. Hollow waveguide cavity ringdown spectroscopy

    NASA Technical Reports Server (NTRS)

    Dreyer, Chris (Inventor); Mungas, Greg S. (Inventor)

    2012-01-01

    Laser light is confined in a hollow waveguide between two highly reflective mirrors. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, and/or optical elements.

  8. [Malignant melanoma of the oral cavity].

    PubMed

    A, Burgos; R, Kaplan; N, Rodríguez; Meza, Vetanzo; Morelatto, R; Piccinni, D

    2008-01-01

    Malignant melanoma of the oral cavity is a rare neoplasm and it is only 0.5% of the malignant neoplasms of the oral cavity, and less than 10% of all the malignant melanomas. The mean age for patients with oral melanoma is from 40 to 70 years; with a higher frequency between the 50 and 60 years. Pigmentation areas are frequently noted before diagnosis of this neoplasm. Some predisposing factors are mechanical traumas resulting from not well adapted prostheses, solar radiation, and chem-icals. Although oral cavity melanomas can remain asymptomatic during a time, the clinical presentations include hemorrhage, ulceration and pain. Melanomas grow fast, generally in a vertical growth phase, with early invasion of bones and lymphatic nodes. The prognosis for patients with melanoma is poor with a 5-year survival rate. The election treatment is surgical. The early diagnosis, the recognition of the lesions for doctors and odontologists, and the biopsy of recent or old pigmentation areas in the mouth that they have some changes (ulceration, bleeding, etc.) will contribute to offer patients a more effective treatment and a higher survival rate. We will present the case study of a 78-year-old male patient with a tumor in the dental ridge surrounded by melanotic spots, which was diagnosed as invasive melanoma and confirmed with immunohistochemical techniques.

  9. Digital Cavity Resonance Monitor, alternative method of measuring cavity microphonics

    SciTech Connect

    Tomasz Plawski; G. Davis; Hai Dong; J. Hovater; John Musson; Thomas Powers

    2005-09-20

    As is well known, mechanical vibration or microphonics in a cryomodule causes the cavity resonance frequency to change at the vibration frequency. One way to measure the cavity microphonics is to drive the cavity with a Phase Locked Loop. Measurement of the instantaneous frequency or PLL error signal provides information about the cavity microphonic frequencies. Although the PLL error signal is available directly, precision frequency measurements require additional instrumentation, a Cavity Resonance Monitor (CRM). The analog version of such a device has been successfully used for several cavity tests [1]. In this paper we present a prototype of a Digital Cavity Resonance Monitor designed and built in the last year. The hardware of this instrument consists of an RF downconverter, digital quadrature demodulator and digital processor motherboard (Altera FPGA). The motherboard processes received data and computes frequency changes with a resolution of 0.2 Hz, with a 3 kHz output bandwidth.

  10. CAVITY CONTROL ALGORITHM

    SciTech Connect

    Tomasz Plawski, J. Hovater

    2010-09-01

    A digital low level radio frequency (RF) system typically incorporates either a heterodyne or direct sampling technique, followed by fast ADCs, then an FPGA, and finally a transmitting DAC. This universal platform opens up the possibilities for a variety of control algorithm implementations. The foremost concern for an RF control system is cavity field stability, and to meet the required quality of regulation, the chosen control system needs to have sufficient feedback gain. In this paper we will investigate the effectiveness of the regulation for three basic control system algorithms: I&Q (In-phase and Quadrature), Amplitude & Phase and digital SEL (Self Exciting Loop) along with the example of the Jefferson Lab 12 GeV cavity field control system.

  11. Cavity enhanced atomic magnetometry.

    PubMed

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-10-20

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  12. Cavity enhanced atomic magnetometry

    PubMed Central

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations. PMID:26481853

  13. Vertical axis windmill

    SciTech Connect

    Campbell, J.S.

    1980-04-08

    A vertical axis windmill is described which involves a rotatable central vertical shaft having horizontal arms pivotally supporting three sails that are free to function in the wind like the main sail on a sail boat, and means for disabling the sails to allow the windmill to be stopped in a blowing wind.

  14. RF Cavity Characterization with VORPAL

    SciTech Connect

    C. Nieter, C. Roark, P. Stoltz, C.D. Zhou, F. Marhauser

    2011-03-01

    When designing a radio frequency (RF) accelerating cavity structure various figures of merit are considered before coming to a final cavity design. These figures of merit include specific field and geometry based quantities such as the ratio of the shunt impedance to the quality factor (R/Q) or the normalized peak fields in the cavity. Other important measures of cavity performance include the peak surface fields as well as possible multipacting resonances in the cavity. High fidelity simulations of these structures can provide a good estimate of these important quantities before any cavity prototypes are built. We will present VORPAL simulations of a simple pillbox structure where these quantities can be calculated analytically and compare them to the results from the VORPAL simulations. We will then use VORPAL to calculate these figures of merit and potential multipacting resonances for two cavity designs under development at Jefferson National Lab for Project X.

  15. Crab Cavities for Linear Colliders

    SciTech Connect

    Burt, G.; Ambattu, P.; Carter, R.; Dexter, A.; Tahir, I.; Beard, C.; Dykes, M.; Goudket, P.; Kalinin, A.; Ma, L.; McIntosh, P.; Shulte, D.; Jones, Roger M.; Bellantoni, L.; Chase, B.; Church, M.; Khabouline, T.; Latina, A.; Adolphsen, C.; Li, Z.; Seryi, Andrei; /SLAC

    2011-11-08

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  16. Deterministic coupling of delta-doped nitrogen vacancy centers to a nanobeam photonic crystal cavity

    SciTech Connect

    Lee, Jonathan C.; Cui, Shanying; Zhang, Xingyu; Russell, Kasey J.; Magyar, Andrew P.; Hu, Evelyn L.; Bracher, David O.; Ohno, Kenichi; McLellan, Claire A.; Alemán, Benjamin; Bleszynski Jayich, Ania; Andrich, Paolo; Awschalom, David; Aharonovich, Igor

    2014-12-29

    The negatively charged nitrogen vacancy center (NV) in diamond has generated significant interest as a platform for quantum information processing and sensing in the solid state. For most applications, high quality optical cavities are required to enhance the NV zero-phonon line (ZPL) emission. An outstanding challenge in maximizing the degree of NV-cavity coupling is the deterministic placement of NVs within the cavity. Here, we report photonic crystal nanobeam cavities coupled to NVs incorporated by a delta-doping technique that allows nanometer-scale vertical positioning of the emitters. We demonstrate cavities with Q up to ∼24 000 and mode volume V ∼ 0.47(λ/n){sup 3} as well as resonant enhancement of the ZPL of an NV ensemble with Purcell factor of ∼20. Our fabrication technique provides a first step towards deterministic NV-cavity coupling using spatial control of the emitters.

  17. Dusty plasma cavities: Probe-induced and natural.

    PubMed

    Harris, B J; Matthews, L S; Hyde, T W

    2015-06-01

    A comprehensive exploration of regional dust evacuation in complex plasma crystals is presented. Voids created in three-dimensional crystals on the International Space Station have provided a rich foundation for experiments, but cavities in dust crystals formed in ground-based experiments have not received as much attention. Inside a modified Gaseous Electronics Conference rf cell, a powered vertical probe was used to clear the central area of a dust crystal, producing a cavity with high cylindrical symmetry. Cavities generated by three mechanisms are examined. First, repulsion of micrometer-sized particles by a negatively charged probe is investigated. A model of this effect developed for a dc plasma is modified and applied to explain experimental data in rf plasma. Second, the formation of natural cavities is surveyed; a radial ion drag proposed to occur due to a curved sheath is considered in conjunction with thermophoresis and a flattened confinement potential above the center of the electrode. Finally, cavity formation upon increasing the probe potential above the plasma floating potential is justified by a combination of ion drag and sheath edge modification. The cavities produced by these methods appear similar, but each is shown to be facilitated by fundamentally different processes.

  18. Resonant-cavity apparatus for cytometry or particle analysis

    DOEpatents

    Gourley, Paul L.

    1998-01-01

    A resonant-cavity apparatus for cytometry or particle analysis. The apparatus comprises a resonant optical cavity having an analysis region within the cavity for containing one or more biological cells or dielectric particles to be analyzed. In the presence of a cell or particle, a light beam in the form of spontaneous emission or lasing is generated within the resonant optical cavity and is encoded with information about the cell or particle. An analysis means including a spectrometer and/or a pulse-height analyzer is provided within the apparatus for recovery of the information from the light beam to determine a size, shape, identification or other characteristics about the cells or particles being analyzed. The recovered information can be grouped in a multi-dimensional coordinate space for identification of particular types of cells or particles. In some embodiments of the apparatus, the resonant optical cavity can be formed, at least in part, from a vertical-cavity surface-emitting laser. The apparatus and method are particularly suited to the analysis of biological cells, including blood cells, and can further include processing means for manipulating, sorting, or eradicating cells after analysis thereof.

  19. Camera assembly design proposal for SRF cavity image collection

    SciTech Connect

    Tuozzolo, S.

    2011-10-10

    This project seeks to collect images from the inside of a superconducting radio frequency (SRF) large grain niobium cavity during vertical testing. These images will provide information on multipacting and other phenomena occurring in the SRF cavity during these tests. Multipacting, a process that involves an electron buildup in the cavity and concurrent loss of RF power, is thought to be occurring near the cathode in the SRF structure. Images of electron emission in the structure will help diagnose the source of multipacting in the cavity. Multipacting sources may be eliminated with an alteration of geometric or resonant conditions in the SRF structure. Other phenomena, including unexplained light emissions previously discovered at SLAC, may be present in the cavity. In order to effectively capture images of these events during testing, a camera assembly needs to be installed to the bottom of the RF structure. The SRF assembly operates under extreme environmental conditions: it is kept in a dewar in a bath of 2K liquid helium during these tests, is pumped down to ultra-high vacuum, and is subjected to RF voltages. Because of this, the camera needs to exist as a separate assembly attached to the bottom of the cavity. The design of the camera is constrained by a number of factors that are discussed.

  20. Resonant-cavity apparatus for cytometry or particle analysis

    DOEpatents

    Gourley, P.L.

    1998-08-11

    A resonant-cavity apparatus for cytometry or particle analysis is described. The apparatus comprises a resonant optical cavity having an analysis region within the cavity for containing one or more biological cells or dielectric particles to be analyzed. In the presence of a cell or particle, a light beam in the form of spontaneous emission or lasing is generated within the resonant optical cavity and is encoded with information about the cell or particle. An analysis means including a spectrometer and/or a pulse-height analyzer is provided within the apparatus for recovery of the information from the light beam to determine a size, shape, identification or other characteristics about the cells or particles being analyzed. The recovered information can be grouped in a multi-dimensional coordinate space for identification of particular types of cells or particles. In some embodiments of the apparatus, the resonant optical cavity can be formed, at least in part, from a vertical-cavity surface-emitting laser. The apparatus and method are particularly suited to the analysis of biological cells, including blood cells, and can further include processing means for manipulating, sorting, or eradicating cells after analysis. 35 figs.

  1. Dusty plasma cavities: Probe-induced and natural

    NASA Astrophysics Data System (ADS)

    Harris, B. J.; Matthews, L. S.; Hyde, T. W.

    2015-06-01

    A comprehensive exploration of regional dust evacuation in complex plasma crystals is presented. Voids created in three-dimensional crystals on the International Space Station have provided a rich foundation for experiments, but cavities in dust crystals formed in ground-based experiments have not received as much attention. Inside a modified Gaseous Electronics Conference rf cell, a powered vertical probe was used to clear the central area of a dust crystal, producing a cavity with high cylindrical symmetry. Cavities generated by three mechanisms are examined. First, repulsion of micrometer-sized particles by a negatively charged probe is investigated. A model of this effect developed for a dc plasma is modified and applied to explain experimental data in rf plasma. Second, the formation of natural cavities is surveyed; a radial ion drag proposed to occur due to a curved sheath is considered in conjunction with thermophoresis and a flattened confinement potential above the center of the electrode. Finally, cavity formation upon increasing the probe potential above the plasma floating potential is justified by a combination of ion drag and sheath edge modification. The cavities produced by these methods appear similar, but each is shown to be facilitated by fundamentally different processes.

  2. Preparation of dental amalgam and spectral diagnosis of mercury in plasmas-laser in the region of 250 nm - 850 nm

    NASA Astrophysics Data System (ADS)

    De la Ossa, A.; Pacheco, P.; Sarmiento, R.

    2013-11-01

    In this paper we presents results of the spectral study of plasmas-laser of dental amalgam by technique Laser-induced Breakdown Spectroscopy (LIBS). Plasmas were generated focusing the beam of a Nd: YAG laser on the matrix of the mixture Ag-Sn-Cu and on amalgams with different proportions of mercury (3:2, 5:2, 6:2). Based on the spectral results and reported atomic parameters, became estimation of electron temperature plasmas- laser and their behavior with the concentration of Hg. The estimated values of the electron temperature for the respective proportions were 20 846 K, 19 139 K and 16 872 K, using the distribution of population of Boltzmann energy levels associated with spectral lines, considering conditions Local Thermodinamic Equilibrium (LTE) of plasmas.

  3. Power and Efficiency Scaling of Fiber OPO Around 700 to 850 nm and Power-scaling of High Coherence Fiber Raman Amplifiers

    DTIC Science & Technology

    2013-10-01

    jn@orc.soton.ac.uk www.orc.soton.ac.uk Phone +44 23 8059 3101 Fax +44 23 8059 3142 Mobile +44 795 753 6468 Final report, EOARD award...Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, United Kingdom Phone (JN) +44 23 8059 3101 (office), +44 795 753...University of Southampton Southampton SO17 1BJ, England jn@orc.soton.ac.uk www.orc.soton.ac.uk Phone +44 23 8059 3101 Fax +44 23 8059 3142

  4. Beam Dynamics Studies of Parallel-Bar Deflecting Cavities

    SciTech Connect

    S. Ahmed, G. Krafft, K. Detrick, S. Silva, J. Delayen, M. Spata ,M. Tiefenback, A. Hofler ,K. Beard

    2011-03-01

    We have performed three-dimensional simulations of beam dynamics for parallel-bar transverse electromagnetic mode (TEM) type RF separators: normal- and super-conducting. The compact size of these cavities as compared to conventional TM$_{110}$ type structures is more attractive particularly at low frequency. Highly concentrated electromagnetic fields between the parallel bars provide strong electrical stability to the beam for any mechanical disturbance. An array of six 2-cell normal conducting cavities or a one- or two-cell superconducting structure are enough to produce the required vertical displacement at the Lambertson magnet. Both the normal and super-conducting structures show very small emittance dilution due to the vertical kick of the beam.

  5. Cavity soliton billiards

    SciTech Connect

    Prati, F.; Lugiato, L. A.; Tissoni, G.; Brambilla, M.

    2011-11-15

    The motion of a self-propelled cavity soliton in a laser where the pump profile acts as a square billiard is investigated. In the long-term dynamics, only closed trajectories are possible, exhibiting nonspecular reflections with striking similarities to walking droplets in a vibrated liquid bath. Open orbits can be achieved either by introducing scattering defects in the pump profile or in the presence of more than two solitons, due to their interaction. Such dynamical properties can be exploited for applications such as a compact soliton-force microscope.

  6. Cavity optomechanical magnetometer.

    PubMed

    Forstner, S; Prams, S; Knittel, J; van Ooijen, E D; Swaim, J D; Harris, G I; Szorkovszky, A; Bowen, W P; Rubinsztein-Dunlop, H

    2012-03-23

    A cavity optomechanical magnetometer is demonstrated. The magnetic-field-induced expansion of a magnetostrictive material is resonantly transduced onto the physical structure of a highly compliant optical microresonator and read out optically with ultrahigh sensitivity. A peak magnetic field sensitivity of 400  nT  Hz(-1/2) is achieved, with theoretical modeling predicting the possibility of sensitivities below 1  pT  Hz(-1/2). This chip-based magnetometer combines high sensitivity and large dynamic range with small size and room temperature operation.

  7. S0 Tight Loop Studies on ICHIRO 9-Cell Cavities

    SciTech Connect

    Furuta, Fumio; Konomi, T.; Saito, Kenji; Bice, Damon; Crawford, Anthony C.; Geng, Rongli

    2009-11-01

    We have continued high gradient R&D of ICHIRO 9-cell cavities at KEK. ICHIRO 9-cell cavity #5 (I9#5) that has no end groups on beam tube to focus on high gradient sent to Jlab as S0 tight loop study. Surface treatments and vertical test were repeated 3 times at Jlab, and then I9#5 sent back to KEK. We also repeated surface treatments and test at KEK. Maximum gradients were 36.5MV/m at Jlab, and 33.7MV/m at KEK so far. Now we are struggling with the puzzle why the results of singles do not work well on 9-cell cavities.

  8. SUPERCONDUCTING RF-DIPOLE DEFLECTING AND CRABBING CAVITIES

    SciTech Connect

    Delayen, Jean; De Silva, Paygalage Subashini

    2013-09-01

    Recent interests in designing compact deflecting and crabbing structures for future accelerators and colliders have initiated the development of novel rf structures. The superconducting rf-dipole cavity is one of the first compact designs with attractive properties such as higher gradients, higher shunt impedance, the absence of lower order modes and widely separated higher order modes. Two rf-dipole designs of 400 MHz and 499 MHz have been designed, fabricated and tested as proof-of-principle designs of compact deflecting and crabbing cavities for the LHC high luminosity upgrade and Jefferson Lab 12 GeV upgrade. The first rf tests have been performed on the rf-dipole geometries at 4.2 K and 2.0 K in a vertical test assembly with excellent results. The cavities have achieved high gradients with high intrinsic quality factors, and multipacting levels were easily processed.

  9. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P.; Sommargren, Gary E.; McConaghy, Charles F.; Krulevitch, Peter A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  10. Applications of cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Metcalfe, Michael

    2014-09-01

    "Cavity-optomechanics" aims to study the quantum properties of mechanical systems. A common strategy implemented in order to achieve this goal couples a high finesse photonic cavity to a high quality factor mechanical resonator. Then, using feedback forces such as radiation pressure, one can cool the mechanical mode of interest into the quantum ground state and create non-classical states of mechanical motion. On the path towards achieving these goals, many near-term applications of this field have emerged. After briefly introducing optomechanical systems and describing the current state-of-the-art experimental results, this article summarizes some of the more exciting practical applications such as ultra-sensitive, high bandwidth accelerometers and force sensors, low phase noise x-band integrated microwave oscillators and optical signal processing such as optical delay-lines, wavelength converters, and tunable optical filters. In this rapidly evolving field, new applications are emerging at a fast pace, but this article concentrates on the aforementioned lab-based applications as these are the most promising avenues for near-term real-world applications. New basic science applications are also becoming apparent such as the generation of squeezed light, testing gravitational theories and for providing a link between disparate quantum systems.

  11. JLEIC SRF cavity RF Design

    SciTech Connect

    Wang, Shaoheng; Guo, Jiquan; Wang, Haipeng; Rimmer, Robert A.

    2016-05-01

    The initial design of a low higher order modes (HOM) impedance superconducting RF (SRF) cavity is presented in this paper. The design of this SRF cavity is for the proposed Jefferson Lab Electron Ion Collider (JLEIC). The electron ring of JLEIC will operate with electrons of 3 to 10 GeV energy. The ion ring of JLEIC will operate with protons of up to 100 GeV energy. The bunch lengths in both rings are ~12 mm (RMS). In order to maintain the short bunch length in the ion ring, SRF cavities are adopted to provide large enough gradient. In the first phase of JLEIC, the PEP II RF cavities will be reused in the electron ring to lower the initial cost. The frequency of the SRF cavities is chosen to be the second harmonic of PEP II cavities, 952.6 MHz. In the second phase of JLEIC, the same frequency SRF cavities may replace the normal conducting PEP II cavities to achieve higher luminosity at high energy. At low energies, the synchro-tron radiation damping effect is quite weak, to avoid the coupled bunch instability caused by the intense closely-spaced electron bunches, low HOM impedance of the SRF cavities combined with longitudinal feedback sys-tem will be necessary.

  12. Nanofriction in Cavity Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Fogarty, T.; Cormick, C.; Landa, H.; Stojanović, Vladimir M.; Demler, E.; Morigi, Giovanna

    2015-12-01

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

  13. Nanofriction in Cavity Quantum Electrodynamics.

    PubMed

    Fogarty, T; Cormick, C; Landa, H; Stojanović, Vladimir M; Demler, E; Morigi, Giovanna

    2015-12-04

    The dynamics of cold trapped ions in a high-finesse resonator results from the interplay between the long-range Coulomb repulsion and the cavity-induced interactions. The latter are due to multiple scatterings of laser photons inside the cavity and become relevant when the laser pump is sufficiently strong to overcome photon decay. We study the stationary states of ions coupled with a mode of a standing-wave cavity as a function of the cavity and laser parameters, when the typical length scales of the two self-organizing processes, Coulomb crystallization and photon-mediated interactions, are incommensurate. The dynamics are frustrated and in specific limiting cases can be cast in terms of the Frenkel-Kontorova model, which reproduces features of friction in one dimension. We numerically recover the sliding and pinned phases. For strong cavity nonlinearities, they are in general separated by bistable regions where superlubric and stick-slip dynamics coexist. The cavity, moreover, acts as a thermal reservoir and can cool the chain vibrations to temperatures controlled by the cavity parameters and by the ions' phase. These features are imprinted in the radiation emitted by the cavity, which is readily measurable in state-of-the-art setups of cavity quantum electrodynamics.

  14. Cavity coalescence in superplastic deformation

    SciTech Connect

    Stowell, M.J.; Livesey, D.W.; Ridley, N.

    1984-01-01

    An analysis of the probability distribution function of particles randomly dispersed in a solid has been applied to cavitation during superplastic deformation and a method of predicting cavity coalescence developed. Cavity size distribution data were obtained from two microduplex nickel-silver alloys deformed superplastically to various extents at elevated temperature, and compared to theoretical predictions. Excellent agreement occurred for small void sizes but the model underestimated the number of voids in the largest size groups. It is argued that the discrepancy results from a combination of effects due to non-random cavity distributions and to enhanced growth rates and incomplete spheroidization of the largest cavities.

  15. SRF CAVITY PERFORMANCE OVERVIEW FOR THE 12 GeV UPGRADE

    SciTech Connect

    A. Burrill, G.K. Davis, C.E. Reece, A.V. Reilly, M. Stirbet

    2012-07-01

    The CEBAF accelerator, a recirculating CW electron accelerator that is currently operating at Jefferson Laboratory, is in the process of having 10 new cryomodules installed to allow for the maximum beam energy to be increased from 6 GeV to 12 GeV. This upgrade required the fabrication, processing and RF qualification of 80, seven cell elliptical SRF cavities, a process that was completed in February 2012. The RF performance achieve in the vertical testing dewars has exceeded the design specification by {approx}25% and is a testament to the cavity design and processing cycle that has been implemented. This paper will provide a summary of the cavity RF performance in the vertical tests, as well as review the overall cavity processing cycle and duration for the project.

  16. High Gradient Results of ICHIRO 9-Cell Cavity in Collaboration With KEK and Jlab

    SciTech Connect

    Furuta, F.; Konomi, T.; Saito, K.; Eremeev, G. V.; Geng, R. L.

    2011-07-01

    KEK and Jlab have continued S0-study collaboration on ICHIRO 9-cell cavities since 2008. In 2010, we have started S0 study on ICHIRO#7, full 9-cell cavity with end groups. Surface treatments and vertical tests have been repeated at Jlab. Maximum gradient of 40MV/m was achieved so far. We will describe the details of that and further plan of S0-study on ICHIRO 9-cell.

  17. Cryogenic test of double quarter wave crab cavity for the LHC High luminosity upgrade

    SciTech Connect

    Xiao, B.; Alberty, L.; Belomestnykh, S.; Ben-Zvi, I.; Calaga, R.; Cullen, C.; Capatina, O.; Hammons, L.; Li, Z.; Marques, C.; Skaritka, J.; Verdu-Andres, S.; Wu, Q.

    2015-05-03

    A Proof-of-Principle (PoP) Double Quarter Wave Crab Cavity (DQWCC) was designed and fabricated for the Large Hadron Collider (LHC) luminosity upgrade. A vertical cryogenic test has been done at Brookhaven National Lab (BNL). The cavity achieved 4.5 MV deflecting voltage with a quality factor above 3×109. We report the test results of this design.

  18. Climate Modeling: Ocean Cavities below Ice Shelves

    SciTech Connect

    Petersen, Mark Roger

    2016-09-12

    The Accelerated Climate Model for Energy (ACME), a new initiative by the U.S. Department of Energy, includes unstructured-mesh ocean, land-ice, and sea-ice components using the Model for Prediction Across Scales (MPAS) framework. The ability to run coupled high-resolution global simulations efficiently on large, high-performance computers is a priority for ACME. Sub-ice shelf ocean cavities are a significant new capability in ACME, and will be used to better understand how changing ocean temperature and currents influence glacial melting and retreat. These simulations take advantage of the horizontal variable-resolution mesh and adaptive vertical coordinate in MPAS-Ocean, in order to place high resolution below ice shelves and near grounding lines.

  19. Shock induced cavity collapse

    NASA Astrophysics Data System (ADS)

    Skidmore, Jonathan; Doyle, Hugo; Tully, Brett; Betney, Matthew; Foster, Peta; Ringrose, Tim; Ramasamy, Rohan; Parkin, James; Edwards, Tom; Hawker, Nicholas

    2016-10-01

    Results from the experimental investigation of cavity collapse driven by a strong planar shock (>6km/s) are presented. Data from high speed framing cameras, laser backlit diagnostics and time-resolved pyromety are used to validate the results of hydrodynamic front-tracking simulations. As a code validation exercise, a 2-stage light gas gun was used to accelerate a 1g Polycarbonate projectile to velocities exceeding 6km/s; impact with a PMMA target containing a gas filled void results in the formation of a strong shockwave with pressures exceeding 1Mbar. The subsequent phenomena associated with the collapse of the void and excitation of the inert gas fill are recorded and compared to simulated data. Variation of the mass density and atomic number of the gas fill is used to alter the plasma parameters furthering the extent of the code validation.

  20. A scanning cavity microscope

    PubMed Central

    Mader, Matthias; Reichel, Jakob; Hänsch, Theodor W.; Hunger, David

    2015-01-01

    Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm2; we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems. PMID:26105690

  1. HOM/LOM Coupler Study for the ILC Crab Cavity

    SciTech Connect

    Xiao, L.; Li, Z.; Ko, K.; /SLAC

    2007-04-16

    The FNAL 9-cell 3.9GHz deflecting mode cavity designed for the CKM experiment was chosen as the baseline design for the ILC BDS crab cavity. The full 9-cell CKM cavity including the coupler end-groups was simulated using the parallel eigensolver Omega3P and scattering parameter solver S3P. It was found that both the notch filters for the HOM/LOM couplers are very sensitive to the notch gap, which is about 1.6MHz/micron and is more than 10 times more sensitive than the TTF cavity. It was also found in the simulation that the unwanted vertical {pi}-mode (SOM) is strongly coupled to the horizontal 7{pi}/9 mode which causes x-y coupling and reduces the effectiveness of the SOM damping. To meet the ILC requirements, the HOM/LOM couplers are redesigned to address these issues. With the new designs, the damping of the HOM/LOM modes is improved. The sensitivity of the notch filter for the HOM coupler is reduced by one order of magnitude. The notch filter for the LOM coupler is eliminated in the new design which significantly simplifies the geometry. In this paper, we will present the simulation results of the original CKM cavity and the progresses on the HOM/LOM coupler re-design and optimization.

  2. Quench studies of ILC cavities

    SciTech Connect

    Eremeev, Grigory; Geng, Rongli; Palczewski, Ari; Dai, Jin

    2011-07-01

    Quench limits accelerating gradient in SRF cavities to a gradient lower than theoretically expected for superconducting niobium. Identification of the quenching site with thermometry and OST, optical inspection, and replica of the culprit is an ongoing effort at Jefferson Lab aimed at better understanding of this limiting phenomenon. In this contribution we present our finding with several SRF cavities that were limited by quench.

  3. Superconducting Storage Cavity for RHIC

    SciTech Connect

    Ben-Zvi,I.

    2009-01-02

    This document provides a top-level description of a superconducting cavity designed to store hadron beams in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It refers to more detailed documents covering the various issues in designing, constructing and operating this cavity. The superconducting storage cavity is designed to operate at a harmonic of the bunch frequency of RHIC at a relatively low frequency of 56 MHz. The current storage cavities of RHIC operate at 197 MHz and are normal-conducting. The use of a superconducting cavity allows for a high gap voltage, over 2 MV. The combination of a high voltage and low frequency provides various advantages stemming from the resulting large longitudinal acceptance bucket.

  4. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, Salvatore

    1985-01-01

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  5. Monochromatic radio frequency accelerating cavity

    DOEpatents

    Giordano, S.

    1984-02-09

    A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

  6. Mechanical Properties of Niobium Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Matalevich, Joseph R.; Myneni, Ganapati Rao

    2015-09-01

    The mechanical stability of bulk Nb cavity is an important aspect to be considered in relation to cavity material, geometry and treatments. Mechanical properties of Nb are typically obtained from uniaxial tensile tests of small samples. In this contribution we report the results of measurements of the resonant frequency and local strain along the contour of single-cell cavities made of ingot and fine-grain Nb of different purity subjected to increasing uniform differential pressure, up to 6 atm. Measurements have been done on cavities subjected to different heat treatments. Good agreement between finite element analysis simulations and experimental data in the elastic regime was obtained with a single set of values of Young’s modulus and Poisson’s ratio. The experimental results indicate that the yield strength of medium-purity ingot Nb cavities is higher than that of fine-grain, high-purity Nb.

  7. Reactor cavity seal ring

    SciTech Connect

    Hankinson, M.F.

    1986-04-22

    A hydrostatic seal is described for sealing an annular gap between two flat substantially horizontal coplanar surfaces comprising, in combination: a generally flat annular plate of a width sufficient to span a gap between two surfaces: compressible annular sealing means disposed on the bottom surface of the flat annular plate for sealingly engaging the two flat surfaces in response to a downward force exerted on the plate; and fastening means, distributed along the center line of the plate, for releasably fastening the plate in a position to span the gap to be sealed and exert a downward force on the plate, each fastening means including a pair of elongated members of a size to fit into the gap to be sealed, means for mounting the members on the bottom surface of the plate so that at least a portion of each member is radially moveable in a direction toward a respective one of the vertical side surfaces defining the gap to be sealed to engage same and so that the plate is moveable relative to the members in a downward direction in response to hydrostatic pressure applied to the upper surface of the plate when the members are engaging the vertical side surfaces of an annular gap, and an actuating means, mounted on the plate for movement therewith in response to hydrostatic pressure, for radially moving the members, the actuating means extending through a bore in the plate to the upper surface of the plate.

  8. A vertical cephalometric analysis.

    PubMed

    Alió Sanz, Juan J; Iglesias Conde, Carmen

    2007-01-01

    Correctly assessing open-bite malocclusions has remained problematic because clinicians have not had entirely reliable methods of determining the exact amount of skeletal and dental contributions to the problem. A new cephalometric technique, the vertical cephalometric analysis, offers orthodontists a system that precisely identifies the percentage of skeletal and dentoalveolar components that open-bite patients have. The vertical cephalometric analysis offers a discriminating diagnostic method for evaluating, diagnosing, and treatment planning for patients with open bite. This technique will allow clinicians to classify patients with accuracy, as well as to establish prognoses and select therapies.

  9. Buffer Chemical Polishing and RF Testing of the 56 MHz SRF Cavity

    SciTech Connect

    Burrill,A.

    2009-01-01

    The 56 MHz cavity presents a unique challenge in preparing it for RF testing prior to construction of the cryomodule. This challenge arises due to the physical dimensions and subsequent weight of the cavity, and is further complicated by the coaxial geometry, and the need to properly chemically etch and high pressure rinse the entire inner surface prior to RF testing. To the best of my knowledge, this is the largest all niobium SRF cavity to be chemically etched and subsequently tested in a vertical dewar at 4K, and these processes will be the topic of this technical note.

  10. Vertical and horizontal seismometric observations of tides

    NASA Astrophysics Data System (ADS)

    Lambotte, S.; Rivera, L.; Hinderer, J.

    2006-01-01

    Tidal signals have been largely studied with gravimeters, strainmeters and tiltmeters, but can also be retrieved from digital records of the output of long-period seismometers, such as STS-1, particularly if they are properly isolated. Horizontal components are often noisier than the vertical ones, due to sensitivity to tilt at long periods. Hence, horizontal components are often disturbed by local effects such as topography, geology and cavity effects, which imply a strain-tilt coupling. We use series of data (duration larger than 1 month) from several permanent broadband seismological stations to examine these disturbances. We search a minimal set of observable signals (tilts, horizontal and vertical displacements, strains, gravity) necessary to reconstruct the seismological record. Such analysis gives a set of coefficients (per component for each studied station), which are stable over years and then can be used systematically to correct data from these disturbances without needing heavy numerical computation. A special attention is devoted to ocean loading for stations close to oceans (e.g. Matsushiro station in Japon (MAJO)), and to pressure correction when barometric data are available. Interesting observations are made for vertical seismometric components; in particular, we found a pressure admittance between pressure and data 10 times larger than for gravimeters for periods larger than 1 day, while this admittance reaches the usual value of -3.5 nm/s 2/mbar for periods below 3 h. This observation may be due to instrumental noise, but the exact mechanism is not yet understood.

  11. High-Temperature Heat Treatment Study on a Large-Grain Nb Cavity

    SciTech Connect

    G. Ciovati, P. Dhakal, R. Myneni, P. Maheshwari, F.A. Stevie

    2011-07-01

    Improvement of the cavity performance by a high-temperature heat-treatment without subsequent chemical etching have been reported for large-grain Nb cavities treated by buffered chemical polishing, as well as for a fine-grain cavity treated by vertical electropolishing. Changes in the quality factor, Q{sub 0}, and maximum peak surface magnetic field achieved in a large-grain Nb single-cell cavity have been determined as a function of the heat treatment temperature, between 600 °C and 1200 °C. The highest Q{sub 0} improvement of about 30% was obtained after heat-treatment at 800 °C-1000 °C. Measurements by secondary ion mass spectrometry on large-grain samples heat-treated with the cavity showed large reduction of hydrogen concentration after heat treatment.

  12. An equivalent circuit model and power calculations for the APS SPX crab cavities.

    SciTech Connect

    Berenc, T. )

    2012-03-21

    An equivalent parallel resistor-inductor-capacitor (RLC) circuit with beam loading for a polarized TM110 dipole-mode cavity is developed and minimum radio-frequency (rf) generator requirements are calculated for the Advanced Photon Source (APS) short-pulse x-ray (SPX) superconducting rf (SRF) crab cavities. A beam-loaded circuit model for polarized TM110 mode crab cavities was derived. The single-cavity minimum steady-state required generator power has been determined for the APS SPX crab cavities for a storage ring current of 200mA DC current as a function of external Q for various vertical offsets including beam tilt and uncontrollable detuning. Calculations to aid machine protection considerations were given.

  13. Vertical shaft windmill

    NASA Technical Reports Server (NTRS)

    Grana, D. C.; Inge, S. V., Jr. (Inventor)

    1983-01-01

    A vertical shaft has several equally spaced blades mounted. Each blade consists of an inboard section and an outboard section skew hinged to the inboard section. The inboard sections automatically adjust their positions with respect to the fixed inboard sections with changes in velocity of the wind. This windmill design automatically governs the maximum rotational speed of shaft.

  14. Aiding Vertical Guidance Understanding

    NASA Technical Reports Server (NTRS)

    Feary, Michael; McCrobie, Daniel; Alkin, Martin; Sherry, Lance; Polson, Peter; Palmer, Everett; McQuinn, Noreen

    1998-01-01

    A two-part study was conducted to evaluate modern flight deck automation and interfaces. In the first part, a survey was performed to validate the existence of automation surprises with current pilots. Results indicated that pilots were often surprised by the behavior of the automation. There were several surprises that were reported more frequently than others. An experimental study was then performed to evaluate (1) the reduction of automation surprises through training specifically for the vertical guidance logic, and (2) a new display that describes the flight guidance in terms of aircraft behaviors instead of control modes. The study was performed in a simulator that was used to run a complete flight with actual airline pilots. Three groups were used to evaluate the guidance display and training. In the training, condition, participants went through a training program for vertical guidance before flying the simulation. In the display condition, participants ran through the same training program and then flew the experimental scenario with the new Guidance-Flight Mode Annunciator (G-FMA). Results showed improved pilot performance when given training specifically for the vertical guidance logic and greater improvements when given the training and the new G-FMA. Using actual behavior of the avionics to design pilot training and FMA is feasible, and when the automated vertical guidance mode of the Flight Management System is engaged, the display of the guidance mode and targets yields improved pilot performance.

  15. Laser Scanner for Tile-Cavity Measurement

    NASA Technical Reports Server (NTRS)

    Yoshino, Stanley Y.; Wykes, Donald H.; Hagen, George R.; Lotgering, Gene E.; Gaynor, Michael B.; Westerlund, Paul G.; Baal, Thomas A.

    1987-01-01

    Irregular surfaces mapped and digitized for numerical-control machinery. Fast, accurate laser scanning system measures size and shape of cavity without making any physical contact with cavity and walls. Measurements processed into control signals for numerically controlled machining of tile or block to fit cavity. System generates map of grid points representing cavity and portion of outer surface surrounding cavity. Map data used to control milling machine, which cuts tile or block to fit in cavity.

  16. Frequency-feedback cavity enhanced spectrometer

    DOEpatents

    Hovde, David Christian; Gomez, Anthony

    2015-08-18

    A spectrometer comprising an optical cavity, a light source capable of producing light at one or more wavelengths transmitted by the cavity and with the light directed at the cavity, a detector and optics positioned to collect light transmitted by the cavity, feedback electronics causing oscillation of amplitude of the optical signal on the detector at a frequency that depends on cavity losses, and a sensor measuring the oscillation frequency to determine the cavity losses.

  17. Nonlocal Intracranial Cavity Extraction

    PubMed Central

    Manjón, José V.; Eskildsen, Simon F.; Coupé, Pierrick; Romero, José E.; Collins, D. Louis; Robles, Montserrat

    2014-01-01

    Automatic and accurate methods to estimate normalized regional brain volumes from MRI data are valuable tools which may help to obtain an objective diagnosis and followup of many neurological diseases. To estimate such regional brain volumes, the intracranial cavity volume (ICV) is often used for normalization. However, the high variability of brain shape and size due to normal intersubject variability, normal changes occurring over the lifespan, and abnormal changes due to disease makes the ICV estimation problem challenging. In this paper, we present a new approach to perform ICV extraction based on the use of a library of prelabeled brain images to capture the large variability of brain shapes. To this end, an improved nonlocal label fusion scheme based on BEaST technique is proposed to increase the accuracy of the ICV estimation. The proposed method is compared with recent state-of-the-art methods and the results demonstrate an improved performance both in terms of accuracy and reproducibility while maintaining a reduced computational burden. PMID:25328511

  18. Cavity-state preparation using adiabatic transfer

    NASA Astrophysics Data System (ADS)

    Larson, Jonas; Andersson, Erika

    2005-05-01

    We show how to prepare a variety of cavity field states for multiple cavities. The state preparation technique used is related to the method of stimulated adiabatic Raman passage. The cavity modes are coupled by atoms, making it possible to transfer an arbitrary cavity field state from one cavity to another and also to prepare nontrivial cavity field states. In particular, we show how to prepare entangled states of two or more cavities, such as an Einstein-Podolsky-Rosen state and a W state, as well as various entangled superpositions of coherent states in different cavities, including Schrödinger cat states. The theoretical considerations are supported by numerical simulations.

  19. Acoustic confinement in superlattice cavities

    NASA Astrophysics Data System (ADS)

    Garcia-Sanchez, Daniel; Déleglise, Samuel; Thomas, Jean-Louis; Atkinson, Paola; Lagoin, Camille; Perrin, Bernard

    2016-09-01

    The large coupling rate between the acoustic and optical fields confined in GaAs/AlAs superlattice cavities makes them appealing systems for cavity optomechanics. We have developed a mathematical model based on the scattering matrix that allows the acoustic guided modes to be predicted in nano and micropillar superlattice cavities. We demonstrate here that the reflection at the surface boundary considerably modifies the acoustic quality factor and leads to significant confinement at the micropillar center. Our mathematical model also predicts unprecedented acoustic Fano resonances on nanopillars featuring small mode volumes and very high mechanical quality factors, making them attractive systems for optomechanical applications.

  20. Novel Crab Cavity RF Design

    SciTech Connect

    Dudas, A.; Neubauer, M. L.; Sah, R.; Rimmer, B.; Wang, H.

    2011-03-01

    A 20-50 MV integrated transverse voltage is required for the Electron-Ion Collider. The most promising of the crab cavity designs that have been proposed in the last five years are the TEM type crab cavities because of the higher transverse impedance. The TEM design approach is extended here to a hybrid crab cavity that includes the input power coupler as an integral part of the design. A prototype was built with Phase I monies and tested at JLAB. The results reported on, and a system for achieving 20-50 MV is proposed.

  1. Light storage and cavity supermodes in two coupled optomechanical cavities

    NASA Astrophysics Data System (ADS)

    He, Yong

    2016-12-01

    We theoretically investigate a hybrid optomechanical system including two coupled optomechanical cavities in the presence of two strong pump fields and a weak probe field. The photon-hopping coupling of the cavities gives rise to two cavity supermodes whose resonant frequencies can be obtained in the probe transmission spectrum. In a strong photon-hopping coupling regime, there is a large coupling rate between the probe field and one of the two cavity supermodes that is called a bright mode. The optomechanical couplings between the bright mode and two mechanical resonators can cause double optomechanically induced transparency (OMIT), which can be employed to both separately and simultaneously store two weak probe pulses with different central frequencies. We obtain the group delay (light storage time) of the probe field in the hybrid optomechanical system. The results suggest that compared with that of a single cavity optomechanical system, the maximum value of the storage time roughly quadrupled in a particular case. The physical origin of the results is discussed. The hybrid optomechanical system opens an avenue of light storage in cavity optomechanics.

  2. Effects of a rectangular cavity on a subsurface layer using elastic finite-difference modeling: implications for seismic determination of gasification cavities

    SciTech Connect

    Becker, D.F.; Hoskins, E.R.; Russell, J.E.

    1983-03-01

    Two-dimensional, finite-difference elastic modeling aids in planning an optimum seismic-acquisition scheme to define the extent of subsurface cavities resulting from in situ gasification. To understand the seismic effects of a cavity, two models are compared and contrasted. Model A consists of a low-velocity layer (LVL) in a half space; Model B contains a rectangular water-filled cavity in the LVL. Amplitude differences are the dominant effect on the surface records for each model. Cavity resonance and diffraction effects are more definitive in vertical seismic profiles (VSP's) and in a ''snapshot'' of the wave field. Interpretation and subtraction of corresponding records for both models shows the need for preand post-gasification seismic recording. Also VSP data are more informative than surface records.

  3. Geometry-invariant resonant cavities

    PubMed Central

    Liberal, I.; Mahmoud, A. M.; Engheta, N.

    2016-01-01

    Resonant cavities are one of the basic building blocks in various disciplines of science and technology, with numerous applications ranging from abstract theoretical modelling to everyday life devices. The eigenfrequencies of conventional cavities are a function of their geometry, and, thus, the size and shape of a resonant cavity is selected to operate at a specific frequency. Here we demonstrate theoretically the existence of geometry-invariant resonant cavities, that is, resonators whose eigenfrequencies are invariant with respect to geometrical deformations of their external boundaries. This effect is obtained by exploiting the unusual properties of zero-index metamaterials, such as epsilon-near-zero media, which enable decoupling of the temporal and spatial field variations in the lossless limit. This new class of resonators may inspire alternative design concepts, and it might lead to the first generation of deformable resonant devices. PMID:27010103

  4. CRAB Cavity in CERN SPS

    SciTech Connect

    Kim, H.J.; Sen, T.; /Fermilab

    2010-05-01

    Beam collisions with a crossing angle at the interaction point are often necessary in colliders to reduce the effects of parasitic collisions which induce emittance growth and decrease beam lifetime. The crossing angle reduces the geometrical overlap of the beams and hence the luminosity. Crab cavity offer a promising way to compensate the crossing angle and to realize effective head-on collisions. Moreover, the crab crossing mitigates the synchro-betatron resonances due to the crossing angle. A crab cavity experiment in SPS is proposed as a proof of principle before deciding on a full crab-cavity implementation in the LHC. In this paper, we investigate the effects of a single crab cavity on beam dynamics in the SPS and life time.

  5. Geometry-invariant resonant cavities

    NASA Astrophysics Data System (ADS)

    Liberal, I.; Mahmoud, A. M.; Engheta, N.

    2016-03-01

    Resonant cavities are one of the basic building blocks in various disciplines of science and technology, with numerous applications ranging from abstract theoretical modelling to everyday life devices. The eigenfrequencies of conventional cavities are a function of their geometry, and, thus, the size and shape of a resonant cavity is selected to operate at a specific frequency. Here we demonstrate theoretically the existence of geometry-invariant resonant cavities, that is, resonators whose eigenfrequencies are invariant with respect to geometrical deformations of their external boundaries. This effect is obtained by exploiting the unusual properties of zero-index metamaterials, such as epsilon-near-zero media, which enable decoupling of the temporal and spatial field variations in the lossless limit. This new class of resonators may inspire alternative design concepts, and it might lead to the first generation of deformable resonant devices.

  6. [Radiotherapy for oral cavity cancers].

    PubMed

    Lapeyre, M; Biau, J; Racadot, S; Moreira, J F; Berger, L; Peiffert, D

    2016-09-01

    Intensity modulated radiation therapy (IMRT) and brachytherapy are standard techniques for the irradiation of oral cavity cancers. These techniques are detailed in terms of indication, preparation, delineation and selection of the volumes, dosimetry and patient positioning control.

  7. Vertical orbital dystopia.

    PubMed

    Tan, S T; Ashworth, G; Czypionka, S; Poole, M D; Briggs, M

    1996-06-01

    Many pathologic processes may lead to vertical orbital dystopia. We reviewed 47 consecutive cases seen over a 13-year period. Twenty-nine patients underwent eye leveling procedures to improve cosmesis, 2 of these by camouflage procedures and 27 by orbital translocation. Ten patients had 16 secondary operations. There was one death, serious complications occurred in 3 patients, and nuisance complications occurred in 20 others. Seven patients developed diplopia postoperatively, and in 6 patients it was troublesome. In these, it resolved fully in 2 patients, improved to be of no consequence in 2, and in the remaining 2 troublesome symptoms persisted requiring inferior oblique muscle recession in 1. Binocular vision was never restored when not present preoperatively, and in 3 patients temporary loss occurred. There was an overall modest but significant improvement in appearance after surgery. It is concluded that vertical orbital translocation is rewarding and worthwhile.

  8. Active Control of Open Cavities

    NASA Technical Reports Server (NTRS)

    UKeiley, Lawrence

    2010-01-01

    Open loop edge blowing was demonstrated as an effective method for reducing the broad band and tonal components of the fluctuating surface pressure in open cavities. Closed loop has been successfully applied to low Mach number open cavities. Need to push actuators that are viable for closed loop control in bandwidth and output. Need a better understanding of the effects of control on the flow through detailed measurements so better actuation strategies can be developed.

  9. Hilly Surroundings (vertical)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This 360-degree view of the terrain surrounding NASA's Mars Exploration Rover Spirit was taken on the rover's 189th sol on Mars (July 15, 2004). It was assembled from images taken by the rover's navigation camera at a position referred to as Site 72, which is at the base of the 'West Spur' portion of the 'Columbia Hills.'' The view is presented in a vertical projection with geometrical seam correction.

  10. Protective Vertical Shelters.

    DTIC Science & Technology

    1983-06-29

    on Generic MX Structures" by John Betz. 5. (AFCMD/82-013) "Finite Element Dynamic Analysis of th, DCT-2 Models" by Barry Bingham . 61 (AFCMD/82-017) "MX...facility to define the HEST structure for the GOVS tests. A SAMSON dynamic finite-element computer code provided pretest predictions of strdsses and...as piecewise linear, elastic- plastic materials. TEST DESCRIPTION Shel ter Models The generic MX vertical shelter is basically a large, reinforced

  11. Vertical bloch line memory

    NASA Technical Reports Server (NTRS)

    Katti, Romney R. (Inventor); Stadler, Henry L. (Inventor); Wu, Jiin-chuan (Inventor)

    1995-01-01

    A new read gate design for the vertical Bloch line (VBL) memory is disclosed which offers larger operating margin than the existing read gate designs. In the existing read gate designs, a current is applied to all the stripes. The stripes that contain a VBL pair are chopped, while the stripes that do not contain a VBL pair are not chopped. The information is then detected by inspecting the presence or absence of the bubble. The margin of the chopping current amplitude is very small, and sometimes non-existent. A new method of reading Vertical Bloch Line memory is also disclosed. Instead of using the wall chirality to separate the two binary states, the spatial deflection of the stripe head is used. Also disclosed herein is a compact memory which uses vertical Bloch line (VBL) memory technology for providing data storage. A three-dimensional arrangement in the form of stacks of VBL memory layers is used to achieve high volumetric storage density. High data transfer rate is achieved by operating all the layers in parallel. Using Hall effect sensing, and optical sensing via the Faraday effect to access the data from within the three-dimensional packages, an even higher data transfer rate can be achieved due to parallel operation within each layer.

  12. Numerical study of natural convection in fully open tilted cavities

    SciTech Connect

    Elsayed, M.M.; Al-Najem, N.M.; El-Refaee, M.M.; Noor, A.A.

    1999-09-01

    A numerical simulation of two-dimensional laminar natural convection in a fully open tilted square cavity with an isothermally heated back wall is conducted. The remaining two walls of the cavity are adiabatic. Steady-state solutions are presented for Grashof numbers between 10{sup 2} and 10{sup 5} and for tilt angles ranging from {minus}60{degree} to 90{degree} (where 90{degree} represents a cavity with the opening facing down). The fluid properties are assumed to be constant except for the density variation with temperature that gives rise to the buoyancy forces, which is treated by the Boussinesq approximation. The fluid concerned is air with Prandtl number fixed at 0.71. The governing equations are expressed in a normalized primitive variables formulation. Numerical predictions of the velocity and temperature fields are obtained using the finite-volume-based power law (SIMPLER: Semi-Implicit Method for Pressure-Linked Equations Revised) algorithm. For a vertical open cavity ({alpha} = 0{degree}), the algorithm generated results that were in good agreement with those previously published. Flow patterns and isotherms are shown in order to give a better understanding of the heat transfer and flow mechanisms inside the cavity. Effects of the controlling parameters-Grashof number and tilt angle-on the heat transfer (average Nusselt number) are presented and analyzed. The results also revealed that the open-cavity Nusselt number approaches the flat-plate solution when either Grashof number or tilt angle increases. In addition, a correlation of the Nusselt number in terms of the Grashof number and tilt angle is developed and presented; a comparison is made with available data from other literature.

  13. Cavity alignment using fringe scanning

    NASA Astrophysics Data System (ADS)

    Sinkunaite, Laura Paulina; Kawabe, Keita; Landry, Michael

    2017-01-01

    LIGO employs two 4-km long Fabry-Pérot arm cavities, which need to be aligned in order for an interferometer to be locked on a TEM00 mode. Once the cavity is locked, alignment signals can be derived from wave-front sensors which measure the TEM01 mode content. However, the alignment state is not always good enough for locking on TEM00. Even when this is the case, the alignment can be evaluated using a free swinging cavity, that shows flashes when higher-order modes become resonant. By moving test masses, small changes are made to the mirror orientation, and hence the TEM00 mode can be optimized iteratively. Currently, this is a manual procedure, and thus it is very time-consuming. Therefore, this project is aimed to study another possible way to lock the cavity on the TEM00 mode. Misalignment information can also be extracted from the power of the higher-order modes transmitted through the cavity. This talk will present an algorithm for this alternative and faster way to derive the alignment state of the arm cavities. Supported by APS FIP, NSF, and Caltech SFP.

  14. VCSEL-based flexible opto-fluidic fluorescence sensors

    NASA Astrophysics Data System (ADS)

    Kang, Dongseok; Gai, Boju; Yoon, Jongseung

    2016-03-01

    Flexible opto-fluidic fluorescence sensors based on microscale vertical cavity surface emitting lasers (micro-VCSELs) and silicon photodiodes (Si-PDs) are demonstrated, where arrays of 850 nm micro-VCSELs and thin film Si-PDs are heterogeneously integrated on a polyethylene terephthalate (PET) substrate by transfer printing, in conjunction with elastomeric fluidic channel. Enabled with optical isolation trenches together with wavelength- and angle-selective spectral filters implemented to suppress the absorption of excitation light, the integrated flexible fluorescence sensors exhibited significantly enhanced signal-to-background ratio, resulting in a maximum sensitivity of 5 × 10-5 wt% of infrared-absorbing organic dyes.

  15. 1310nm VCSELs in 1-10Gb/s commercial applications

    NASA Astrophysics Data System (ADS)

    Jewell, Jack; Graham, Luke; Crom, Max; Maranowski, Kevin; Smith, Joseph; Fanning, Tom

    2006-02-01

    Beginning with 4 Gigabit/sec Fibre-Channel, 1310nm vertical-cavity surface-emitting lasers (VCSELs) are now entering the marketplace. Such VCSELs perform like distributed feedback lasers but have drive currents and heat dissipation like 850nm VCSELs, making them ideal for today's high-performance interconnects and the only choice for the next step in increased interconnection density. Transceiver performances at 4 and 10 Gigabits/sec over fiber lengths 10-40km are presented. The active material is extremely robust, resulting in excellent reliability.

  16. Radiation shielding for superconducting RF cavity test facility at A0

    SciTech Connect

    Dhanaraj, N.; Ginsburg, C.; Rakhno, I.; Wu, G.; /Fermilab

    2008-11-01

    The results of Monte Carlo radiation shielding study performed with the MARS15 code for the vertical test facility at the A0 north cave enclosure at Fermilab are presented and discussed. The vertical test facility at the A0 north cave is planned to be used for testing 1.3 GHz single-cell superconducting RF cavities with accelerating length of 0.115 m. The operations will be focused on high accelerating gradients--up to 50 MV/m. In such a case the facility can be a strong radiation source [1]. When performing a radiation shielding design for the facility one has to take into account gammas generated due to interactions of accelerated electrons with cavity walls and surroundings (for example, range of 3.7-MeV electrons in niobium is approximately 3.1 mm while the thickness of the niobium walls of such RF cavities is about 2.8 mm). The electrons are usually the result of contamination in the cavity. The radiation shielding study was performed with the MARS15 Monte Carlo code [2]. A realistic model of the source term has been used that describes spatial, energy and angular distributions of the field-emitted electrons inside the RF cavities. The results of the calculations are normalized using the existing experimental data on measured dose rate in the vicinity of such RF cavities.

  17. Fabrication of elliptical SRF cavities

    NASA Astrophysics Data System (ADS)

    Singer, W.

    2017-03-01

    The technological and metallurgical requirements of material for high-gradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10 μg g-1. The hydrogen content should be kept below 2 μg g-1 to prevent degradation of the quality factor (Q-value) under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Traditional and alternative cavity mechanical fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and electron beam welding. The welding of half-cells is a delicate procedure, requiring intermediate cleaning steps and a careful choice of weld parameters to achieve full penetration of the joints. A challenge for a welded construction is the tight mechanical and electrical tolerances. These can be maintained by a combination of mechanical and radio-frequency measurements on half-cells and by careful tracking of weld shrinkage. The main aspects of quality assurance and quality management are mentioned. The experiences of 800 cavities produced for the European XFEL are presented. Another cavity fabrication approach is slicing discs from the ingot and producing cavities by deep drawing and electron beam welding. Accelerating gradients at the level of 35-45 MV m-1 can be achieved by applying electrochemical polishing treatment. The single-crystal option (grain boundary free) is discussed. It seems that in this case, high performance can be achieved by a simplified treatment procedure. Fabrication of the elliptical resonators from a seamless pipe as an alternative is briefly described. This technology has yielded good

  18. Developments of 700-Mhz 5-Cell Superconducting Cavities for APT

    SciTech Connect

    T. Tajima; K. C. D. Chan; R. C. Gentzlinger; W. B. Haynes; J. P. Kelley; F. L. Krawczyk; M. A. Madrid; D. I. Montoya; D. L. Schrage; A. H. Shapiro; J. Mammosser

    2001-07-01

    We have manufactured a total of six {beta} = 0.64, 700-MHz 5-cell cavities. The APT (Accelerator Production of Tritium) specification requires Q{sub 0} > 5 x 10{sup 9} at an accelerating field of 5 MV/m. So far, the results of vertical tests have shown maximum accelerating fields of 12 MV/m (peak surface field of 41 MV/m) and maximum low-field Q{sub 0} of 3.6 x 10{sup 10} at 2 K. The present limitations are available input power, field emission and quench. This type of cavities will also be used for an ADTF (Accelerator-Driven Test Facility) for AAA (Advanced Accelerator Applications) project.

  19. Normal Conducting RF Cavity for MICE

    SciTech Connect

    Li, D.; DeMello, A.; Virostek, S.; Zisman, M.; Summers, D.

    2010-05-23

    Normal conducting RF cavities must be used for the cooling section of the international Muon Ionization Cooling Experiment (MICE), currently under construction at Rutherford Appleton Laboratory (RAL) in the UK. Eight 201-MHz cavities are needed for the MICE cooling section; fabrication of the first five cavities is complete. We report the cavity fabrication status including cavity design, fabrication techniques and preliminary low power RF measurements.

  20. The ESS elliptical cavity cryomodules

    SciTech Connect

    Darve, Christine; Bosland, Pierre; Devanz, Guillaume; Renard, Bertrand; Olivier, Gilles; Thermeau, Jean-Pierre

    2014-01-29

    The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today’s leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. The superconducting section of the Linac accelerates the beam from 80 MeV to 2.0 GeV. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. These cryomodules contain four elliptical Niobium cavities operating at 2 K and at a frequency of 704.42 MHz. This paper introduces the thermo-mechanical design, the prototyping and the expected operation of the ESS elliptical cavity cryomodules. An Elliptical Cavity Cryomodule Technology Demonstrator (ECCTD) will be built and tested in order to validate the ESS series production.

  1. The ESS spoke cavity cryomodules

    SciTech Connect

    Bousson, Sebastien; Duthil, Patxi; Reynet, Denis; Thermeau, Jean-Pierre

    2014-01-29

    The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today’s leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. This paper introduces the thermo-mechanical design and expected operation of the ESS spoke cavity cryomodules. These cryomodules contain two double spoke bulk Niobium cavities operating at 2 K and at a frequency of 352.21 MHz. The superconducting section of the Spoke Linac accelerates the beam from 90 MeV to 220 MeV. A Spoke Cavity Cryomodule Technology Demonstrator will be built and tested in order to validate the ESS series production.

  2. Coupling of an overdriven cavity

    SciTech Connect

    Garbin, H D

    1993-11-01

    It is well known that when a nuclear test is conducted in a sufficiently large cavity, the resulting seismic signal is sharply reduced when compared to a normal tamped event. Cavity explosions are of interest in the seismic verification community because of this possibility of reducing the seismic energy generated which can lower signal amplitudes and make detection difficult. Reduced amplitudes would also lower seismic yield estimates which has implications in a Threshold Test Ban Treaty (TTBT). In the past several years, there have been a number of nuclear tests at NTS (Nevada Test Site) inside hemispherical cavities. Two such tests were MILL YARD and MISTY ECHO which had instrumentation at the surface and in the free-field. These two tests differ in one important aspect. MILL YARD was completely decoupled i.e., the cavity wall behaved in an elastic manner. It was estimated that MILL YARD`s ground motion was reduced by a factor of at least 70. In contrast, MISTY ECHO was detonated in a hemispherical cavity with the same dimensions as MILL YARD, but with a much larger device yield. This caused an inelastic behavior on the wall and the explosion was not fully decoupled.

  3. Effects of dentin depth and cavity configuration on bond strength.

    PubMed

    Yoshikawa, T; Sano, H; Burrow, M F; Tagami, J; Pashley, D H

    1999-04-01

    During polymerization of resin composites, shrinkage stresses compete with resin-dentin bonds in a manner that can cause failure of the bond, depending upon the configuration of the cavity, its depth, and the restorative technique. The hypothesis tested in this study was that the effect of cavity configuration (C) and remaining dentin thickness (RDT) influence resin bond strength to the dentin of Class I cavity floors. The occlusal enamel was ground to expose a flat superficial dentin surface as a control (superficial dentin, C-factor = 1) in human extracted third molars. Cavities 3 mm long x 4 mm wide were prepared to a depth 2 mm below the ground dentin surfaces (deep dentin within cavity floor, C-factor = 3). To assess the relationship between C-factor and RDT, we removed the walls of cavities, making a deep flat surface for bonding (deep dentin, C-factor = 1). The teeth were restored with either Clearfil Liner Bond II (LB II), One-Step (OS), or Super-Bond D Liner (DL), followed by Clearfil Photo Posterior resin composite. After 24 hrs' storage in water, the teeth were sectioned vertically into 3 or 4 slabs (0.7 mm thick) and trimmed for the micro-tensile bond test so that we could determine the strength of the resin bonds to the pulpal floor. All groups gave high bond strengths to superficial dentin, but OS and DL gave significantly lower bond strengths to flat deep dentin when the C-factor was 1. When the C-factor was increased to 3 by the creation of a three-dimensional cavity preparation, the bond strengths of all materials fell (range, 21 to 35%), but the difference was significant (p < 0.05) only with DL. SEM observations of failure patterns showed that specimens with high bond strengths tended to exhibit cohesive failures within the hybrid layer, while specimens exhibiting low bond strengths showed failures at the top of the hybrid layer. Some adhesives do not bond well to deep dentin, making them more susceptible to polymerization shrinkage stress that

  4. Optical Material Characterization Using Microdisk Cavities

    NASA Astrophysics Data System (ADS)

    Michael, Christopher P.

    Since Jack Kilby recorded his "Monolithic Idea" for integrated circuits in 1958, microelectronics companies have invested billions of dollars in developing the silicon material system to increase performance and reduce cost. For decades, the industry has made Moore's Law, concerning cost and transistor density, a self-fulfilling prophecy by integrating technical and material requirements vertically down their supply chains and horizontally across competitors in the market. At recent technology nodes, the unacceptable scaling behavior of copper interconnects has become a major design constraint by increasing latency and power consumption---more than 50% of the power consumed by high speed processors is dissipated by intrachip communications. Optical networks at the chip scale are a potential low-power high-bandwidth replacement for conventional global interconnects, but the lack of efficient on-chip optical sources has remained an outstanding problem despite significant advances in silicon optoelectronics. Many material systems are being researched, but there is no ideal candidate even though the established infrastructure strongly favors a CMOS-compatible solution. This thesis focuses on assessing the optical properties of materials using microdisk cavities with the intention to advance processing techniques and materials relevant to silicon photonics. Low-loss microdisk resonators are chosen because of their simplicity and long optical path lengths. A localized photonic probe is developed and characterized that employs a tapered optical-fiber waveguide, and it is utilized in practical demonstrations to test tightly arranged devices and to help prototype new fabrication methods. A case study in AlxGa1-xAs illustrates how the optical scattering and absorption losses can be obtained from the cavity-waveguide transmission. Finally, single-crystal Er2O3 epitaxially grown on silicon is analyzed in detail as a potential CMOS-compatable gain medium due to its high Er3

  5. A SURVEY OF CORONAL CAVITY DENSITY PROFILES

    SciTech Connect

    Fuller, J.; Gibson, S. E.

    2009-08-01

    Coronal cavities are common features of the solar corona that appear as darkened regions at the base of coronal helmet streamers in coronagraph images. Their darkened appearance indicates that they are regions of lowered density embedded within the comparatively higher density helmet streamer. Despite interfering projection effects of the surrounding helmet streamer (which we refer to as the cavity rim), Fuller et al. have shown that under certain conditions it is possible to use a Van de Hulst inversion of white-light polarized brightness (pB) data to calculate the electron density of both the cavity and cavity rim plasma. In this article, we apply minor modifications to the methods of Fuller et al. in order to improve the accuracy and versatility of the inversion process, and use the new methods to calculate density profiles for both the cavity and cavity rim in 24 cavity systems. We also examine trends in cavity morphology and how departures from the model geometry affect our density calculations. The density calculations reveal that in all 24 cases the cavity plasma has a flatter density profile than the plasma of the cavity rim, meaning that the cavity has a larger density depletion at low altitudes than it does at high altitudes. We find that the mean cavity density is over four times greater than that of a coronal hole at an altitude of 1.2 R{sub sun} and that every cavity in the sample is over twice as dense as a coronal hole at this altitude. Furthermore, we find that different cavity systems near solar maximum span a greater range in density at 1.2 R{sub sun} than do cavity systems near solar minimum, with a slight trend toward higher densities for systems nearer to solar maximum. Finally, we found no significant correlation of cavity density properties with cavity height-indeed, cavities show remarkably similar density depletions-except for the two smallest cavities that show significantly greater depletion.

  6. RRR Characteristics for SRF cavities

    NASA Astrophysics Data System (ADS)

    Jung, Yoochul; Hyun, Myungook; Joung, Mijoung

    2015-10-01

    The first heavy ion accelerator is being constructed by the rare isotope science project (RISP) launched by the Institute of Basic Science (IBS) in South Korea. Four different types of superconducting cavities were designed, and prototypes such as a quarter-wave resonator (QWR), a half-wave resonator (HWR) and a single-spoke resonator (SSR) were fabricated. One of the critical factors determining the performances of superconducting cavities is the residual resistance ratio (RRR). The RRR values essentially represent how pure niobium is and how fast niobium can transmit heat. In general, the RRR degrades during electron beam welding due to impurity incorporation. Thus, it is important to maintain the RRR above a certain value at which a niobium cavity shows target performance. In this study, RRR degradation related with electron beam welding conditions, for example, the welding power, welding speed, and vacuum level, will be discussed.

  7. MHD natural convection in an inclined square porous cavity with a heat conducting solid block

    NASA Astrophysics Data System (ADS)

    Sivaraj, C.; Sheremet, M. A.

    2017-03-01

    This paper deals with natural convection in an inclined porous cavity with a heat conducting solid body placed at its center under the influence of the applied magnetic field of different orientations. The left and right vertical walls of the cavity are maintained at different temperatures Th and Tc, respectively, while the horizontal walls are adiabatic. The governing coupled partial differential equations were solved using a finite volume method on a uniformly staggered grid system. The effects of the inclination angles of the magnetic field and cavity and the Hartmann number on the flow and thermal fields are investigated in detail. Numerical results are presented in terms of isotherms, streamlines and average Nusselt numbers. In general, the results indicate that the inclusion of the magnetic field reduces the convective heat transfer rate in the cavity. It is also found that an increase in the angle of the applied magnetic field produces a non-linear variation in the average Nusselt numbers.

  8. Cavity-controlled spectral singularity.

    PubMed

    Nireekshan Reddy, K; Dutta Gupta, S

    2014-08-01

    We study theoretically a parity-time (PT)-symmetric, saturable, balanced gain-loss system in a ring-cavity configuration. The saturable gain and loss are modeled by a two-level medium with or without population inversion. We show that the specifics of the spectral singularity can be fully controlled by the cavity and the atomic detuning parameters. The theory is based on the mean-field approximation, as in the standard theory of optical bistability. Further, in the linear regime we demonstrate the regularization of the singularity in detuned systems, while larger input power levels are shown to be adequate to limit the infinite growth in absence of detunings.

  9. Synchronization in an optomechanical cavity

    NASA Astrophysics Data System (ADS)

    Shlomi, Keren; Yuvaraj, D.; Baskin, Ilya; Suchoi, Oren; Winik, Roni; Buks, Eyal

    2015-03-01

    We study self-excited oscillations (SEO) in an on-fiber optomechanical cavity. Synchronization is observed when the optical power that is injected into the cavity is periodically modulated. A theoretical analysis based on the Fokker-Planck equation evaluates the expected phase space distribution (PSD) of the self-oscillating mechanical resonator. A tomography technique is employed for extracting PSD from the measured reflected optical power. Time-resolved state tomography measurements are performed to study phase diffusion and phase locking of the SEO. The detuning region inside which synchronization occurs is experimentally determined and the results are compared with the theoretical prediction.

  10. Temperature optimization for superconducting cavities

    SciTech Connect

    Rode, Claus

    1999-06-01

    Since our previous analysis of optimized operating temperature of superconducting cavities in an accelerator a decade ago, significant additional information has been discovered about SRF cavities. The most significant is the Q0 (quality factor) shift across the Lambda line at higher gradients as a result of a slope in Q0 vs. Eacc above Lambda. This is a result of the changing heat conduction conditions. We discuss temperature optimizations as a function of gradient and frequency. The refrigeration hardware impacts and changes in cycle efficiency are presented.

  11. Experimental cavity pressure distributions at supersonic speeds

    NASA Technical Reports Server (NTRS)

    Stallings, Robert L., Jr.; Wilcox, Floyd J., Jr.

    1987-01-01

    An investigation was conducted to define pressure distributions for rectangular cavities over a range of free-stream Mach numbers and cavity dimensions. These pressure distributions together with schlieren photographs are used to define the critical values of cavity length-to-depth ratio that separate open type cavity flows from closed type cavity flows. For closed type cavity flow, the shear layer expands over the cavity leading edge and impinges on the cavity floor, whereas for open type cavity flow, the shear layer bridges the cavity. The tests were conducted by using a flat-plate model permitting the cavity length to be remotely varied from 0.5 to 12 in. Cavity depths and widths were varied from 0.5 to 2.5 in. The flat-plate boundary layer approaching the cavity was turbulent and had a thickness of approximately 0.2 in. at the cavity front face for the range of test Mach numbers from 1.5 to 2.86. Presented are a discussion of the results and a complete tabulation of the experimental data.

  12. A World Vertical Network.

    DTIC Science & Technology

    1980-02-01

    and continental levelling nets into a unifiled World Vertical Network. OD ,~ 173 OITON F I OV 5 I OSOLEI tnc las 9if led SECURITY CLASSIP CATION O T...rp,0p,Xp is T(P) = V(P) - U (P) (2.2) The gravity potential of the Earth is W(P) = V(P) + ((P) (2.3) where o ( P) = w rp’ cos 2 Op corresponds to the...is, therefore, A W(P,Q) = U(P) + T(P) + 0 (P) - U(Q) - T(Q) - o (Q) (2.4) With both P and Q on the Earth’s surface, the uncertainties in the calculated

  13. Multicolored Vertical Silicon Nanowires

    SciTech Connect

    Seo, Kwanyong; Wober, Munib; Steinvurzel, P.; Schonbrun, E.; Dan, Yaping; Ellenbogen, T.; Crozier, K. B.

    2011-04-13

    We demonstrate that vertical silicon nanowires take on a surprising variety of colors covering the entire visible spectrum, in marked contrast to the gray color of bulk silicon. This effect is readily observable by bright-field microscopy, or even to the naked eye. The reflection spectra of the nanowires each show a dip whose position depends on the nanowire radii. We compare the experimental data to the results of finite difference time domain simulations to elucidate the physical mechanisms behind the phenomena we observe. The nanowires are fabricated as arrays, but the vivid colors arise not from scattering or diffractive effects of the array, but from the guided mode properties of the individual nanowires. Each nanowire can thus define its own color, allowing for complex spatial patterning. We anticipate that the color filter effect we demonstrate could be employed in nanoscale image sensor devices.

  14. Analog detection for cavity lifetime spectroscopy

    DOEpatents

    Zare, Richard N.; Harb, Charles C.; Paldus, Barbara A.; Spence, Thomas G.

    2001-05-15

    An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

  15. Analog detection for cavity lifetime spectroscopy

    DOEpatents

    Zare, Richard N.; Harb, Charles C.; Paldus, Barbara A.; Spence, Thomas G.

    2003-01-01

    An analog detection system for determining a ring-down rate or decay rate 1/.tau. of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

  16. Progress on a Be Cavity Design

    SciTech Connect

    Li, D.; Virostek, S.; Zisman, M. S.; Palmer, R.; Stratakis, D.

    2011-10-06

    Previous RF experiments with normal-conducting cavities have demonstrated that there is a significant degradation in maximum gradient when the cavity is subjected to a strong axial magnetic field. We have developed a model suggesting that a cavity with beryllium walls may perform better than copper cavities. In this paper we outline the issues that led us to propose fabricating a Be-wall cavity. We also discuss a concept for fabricating such a cavity and mention some of the manufacturing issues we expect to face.

  17. Progress on a Be Cavity Design

    SciTech Connect

    Li, D.; Palmer, R.; Stratakis, D.; Virostek, S.; Zisman, Michael S.

    2010-12-24

    Previous RF experiments with normal-conducting cavities have demonstrated that there is a significant degradation in maximum gradient when the cavity is subjected to a strong axial magnetic field. We have developed a model suggesting that a cavity with beryllium walls may perform better than copper cavities. In this paper we outline the issues that led us to propose fabricating a Be-wall cavity. We also discuss a concept for fabricating such a cavity and mention some of the manufacturing issues we expect to face.

  18. Direct Observation of Ultralow Vertical Emittance using a Vertical Undulator

    SciTech Connect

    Wootton, Kent

    2015-09-17

    In recent work, the first quantitative measurements of electron beam vertical emittance using a vertical undulator were presented, with particular emphasis given to ultralow vertical emittances [K. P. Wootton, et al., Phys. Rev. ST Accel. Beams, 17, 112802 (2014)]. Using this apparatus, a geometric vertical emittance of 0.9 #6;± 0.3 pm rad has been observed. A critical analysis is given of measurement approaches that were attempted, with particular emphasis on systematic and statistical uncertainties. The method used is explained, compared to other techniques and the applicability of these results to other scenarios discussed.

  19. First Test Results of the bERLinPro 2-cell Booster Cavities

    SciTech Connect

    Burrill, Andrew; Anders, W.; Frahm, A.; Knobloch, Jens; Neumann, Axel; Ciovati, Gianluigi; Clemens, William; Kneisel, Peter; Turlington, Larry

    2015-09-01

    The bERLinPro Energy Recovery Linac (ERL) is currently being built at Helmholtz-Zentrum Berlin in order to study the physics of operating a high-current, a 100 mA, 50 MeV ERL utilizing all SRF cavity technology. This machine will utilize three unique SRF cryomodules for the photoinjector, booster and linac cryomodules respectively. The focus of this paper will be on the cavities contained within the booster cryomodule. Here there will be three 2-cell SRF cavities, based on the original design by Cornell University, but optimized to meet the needs of the project. All of the cavity fabrication, processing and testing was carried out at Jefferson Laboratory, where 4 cavities were produced, and the 3 cavities with the best RF performance were fitted with helium vessels for installation in the cryomodule. This paper will report on the test results of the cavities as measured in the vertical testing dewar at JLab after fabrication and again after outfitting with the helium vessels.

  20. Apparatus For Linewidth Reduction in Distributed Feedback or Distributed Bragg Reflector Semiconductor Lasers Using Vertical Emission

    NASA Technical Reports Server (NTRS)

    Cook, Anthony L. (Inventor); Hendricks, Herbert D. (Inventor)

    2000-01-01

    The linewidth of a distributed feedback semiconductor laser or a distributed Bragg reflector laser having one or more second order gratings is reduced by using an external cavity to couple the vertical emission back into the laser. This method and device prevent disturbance of the main laser beam, provide unobstructed access to laser emission for the formation of the external cavity, and do not require a very narrow heat sink. Any distributed Bragg reflector semiconductor laser or distributed feedback semiconductor laser that can produce a vertical emission through the epitaxial material and through a window in the top metallization can be used. The external cavity can be formed with an optical fiber or with a lens and a mirror or grating.

  1. Subhertz linewidth diode lasers by stabilization to vibrationally and thermally compensated ultralow-expansion glass Fabry-Pérot cavities

    NASA Astrophysics Data System (ADS)

    Alnis, J.; Matveev, A.; Kolachevsky, N.; Udem, Th.; Hänsch, T. W.

    2008-05-01

    We achieved a 0.5 Hz optical beat note linewidth with ˜0.1Hz/s frequency drift at 972 nm between two external cavity diode lasers independently stabilized to two vertically mounted Fabry-Pérot (FP) reference cavities with a finesse of 400 000. Vertical FP reference cavities are suspended in midplane such that the influence of vertical vibrations to the mirror separation is significantly suppressed. This makes the setup virtually immune for vertical vibrations that are more difficult to isolate than horizontal vibrations. To compensate for thermal drifts the FP spacers are made from ultralow-expansion (ULE) glass which possesses a zero linear expansion coefficient. A design using Peltier elements in vacuum allows operation at an optimal temperature where the quadratic temperature expansion of ULE could be eliminated as well. The measured linear drift of such ULE FP cavity of 63 mHz/s was due to material aging and the residual frequency fluctuations were less than ±20Hz during 16 h of measurement. Some part of the temperature-caused drift is attributed to the thermal expansion of the mirror coatings. Thermally induced fluctuations that cause vibrations of the mirror surfaces limit the stability of our cavity. By comparing two similar laser systems we obtain an Allan instability of 2×10-15 between 0.1 and 10 s averaging time, which is close to the theoretical thermal noise limit.

  2. Facing rim cavities fluctuation modes

    NASA Astrophysics Data System (ADS)

    Casalino, Damiano; Ribeiro, André F. P.; Fares, Ehab

    2014-06-01

    Cavity modes taking place in the rims of two opposite wheels are investigated through Lattice-Boltzmann CFD simulations. Based on previous observations carried out by the authors during the BANC-II/LAGOON landing gear aeroacoustic study, a resonance mode can take place in the volume between the wheels of a two-wheel landing gear, involving a coupling between shear-layer vortical fluctuations and acoustic modes resulting from the combination of round cavity modes and wheel-to-wheel transversal acoustic modes. As a result, side force fluctuations and tonal noise side radiation take place. A parametric study of the cavity mode properties is carried out in the present work by varying the distance between the wheels. Moreover, the effects due to the presence of the axle are investigated by removing the axle from the two-wheel assembly. The azimuthal properties of the modes are scrutinized by filtering the unsteady flow in narrow bands around the tonal frequencies and investigating the azimuthal structure of the filtered fluctuation modes. Estimation of the tone frequencies with an ad hoc proposed analytical formula confirms the observed modal properties of the filtered unsteady flow solutions. The present study constitutes a primary step in the description of facing rim cavity modes as a possible source of landing gear tonal noise.

  3. A STUDY OF FERRITE CAVITY.

    SciTech Connect

    ZHAO, Y.

    2002-04-19

    This note addresses the general concerns for the design of a ferrite cavity. The parameters are specified for the RCMS, for which the frequency ramp is in the range of 1.27 MHz to 6.44 MHz, or a ratio of 1:5.

  4. Fibre ring cavity semiconductor laser

    SciTech Connect

    Duraev, V P; Medvedev, S V

    2013-10-31

    This paper presents a study of semiconductor lasers having a polarisation maintaining fibre ring cavity. We examine the operating principle and report main characteristics of a semiconductor ring laser, in particular in single- and multiple-frequency regimes, and discuss its application areas. (lasers)

  5. "Grinding" cavities in polyurethane foam

    NASA Technical Reports Server (NTRS)

    Brower, J. R.; Davey, R. E.; Dixon, W. F.; Robb, P. H.; Zebus, P. P.

    1980-01-01

    Grinding tool installed on conventional milling machine cuts precise cavities in foam blocks. Method is well suited for prototype or midsize production runs and can be adapted to computer control for mass production. Method saves time and materials compared to bonding or hot wire techniques.

  6. Piezoelectric tunable microwave superconducting cavity

    NASA Astrophysics Data System (ADS)

    Carvalho, N. C.; Fan, Y.; Tobar, M. E.

    2016-09-01

    In the context of engineered quantum systems, there is a demand for superconducting tunable devices, able to operate with high-quality factors at power levels equivalent to only a few photons. In this work, we developed a 3D microwave re-entrant cavity with such characteristics ready to provide a very fine-tuning of a high-Q resonant mode over a large dynamic range. This system has an electronic tuning mechanism based on a mechanically amplified piezoelectric actuator, which controls the resonator dominant mode frequency by changing the cavity narrow gap by very small displacements. Experiments were conducted at room and dilution refrigerator temperatures showing a large dynamic range up to 4 GHz and 1 GHz, respectively, and were compared to a finite element method model simulated data. At elevated microwave power input, nonlinear thermal effects were observed to destroy the superconductivity of the cavity due to the large electric fields generated in the small gap of the re-entrant cavity.

  7. Cavity Enhanced Velocity Modulation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Siller, Brian; Mills, Andrew; McCall, Benjamin J.

    2010-06-01

    Velocity modulation spectroscopy has traditionally been used with a unidirectional multipass White cell to obtain several passes through a plasma in order to obtain strong signals from the absorption of ions, but the total number of passes allowed by this type of setup is limited to ˜8. By placing an optical cavity around an N_2^+ plasma and locking the cavity to a Ti:Sapphire laser, the effective number of passes has been increased to several hundred. Demodulating the signal from the transmitted light at twice the plasma frequency (due to the symmetric nature of the cavity) gives a 2nd derivative lineshape for ions and a Gaussian lineshape for excited neutrals. N_2^+ and N_2^* have been observed to be 78° out of phase with one another. The different lineshapes and phases allow for discrimination and separation of the ion and neutral signals. The high intensity laser light within the cavity causes the transitions to saturate, which allows for the observation of lamb dips; this opens the door to sub-Doppler spectroscopy, as well as to studies of ion-neutral collisional rate coefficients.

  8. ON-LINE TOOLS FOR PROPER VERTICAL POSITIONING OF VERTICAL SAMPLING INTERVALS DURING SITE ASSESSMENT

    EPA Science Inventory

    This presentation presents on-line tools for proper vertical positioning of vertical sampling intervals during site assessment. Proper vertical sample interval selection is critical for generate data on the vertical distribution of contamination. Without vertical delineation, th...

  9. Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing.

    PubMed

    Liao, C R; Hu, T Y; Wang, D N

    2012-09-24

    We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 × 10(-6) RIU/°C.

  10. External-cavity solid-state organic lasers: Design rules and application perspectives (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chénais, Sébastien; Gallinelli, Thomas; Mhibik, Oussama; Blanchard, Cédric; Forget, Sébastien

    2016-09-01

    Among various laser architectures currently used to make lasers out of organic materials (distributed feedback lasers or organic vertical cavity surface-emitting lasers, ....), vertical EXTERNAL cavities have several distinctive features that enable making lasers with a high brightness, resulting from a combination of high efficiency and good beam quality, and also offer a superior flexibility to monitor the laser spectrum. In this talk I will highlight a few recent results on external-cavity organic lasers and reveal their potential through the example of a single mode organic laser device with an ultranarrow linewidth (< pm) corresponding to coherence lengths of several meters under diode pumping (typically 2-3 orders of magnitude longer than the state-of-the-art). From the material point of view, I will also show how ink-jet printing can be successfully used in vertical external-cavity organic lasers to make thick and optical-quality films that have the potential to be easily produced with a high throughput.

  11. Vertical landing on an asteroid

    NASA Technical Reports Server (NTRS)

    Harel, D.; Geulman, M.

    1992-01-01

    This work is concerned with the final approach phase and vertical landing on an asteroid with a power-limited, electrically propelled spacecraft. With gravitational effects taken into account, a new solution to the fuel optimal vertical landing on an asteroid was obtained. In this solution, the spacecraft commanded acceleration is explicitly expressed as a function of vehicle velocity and time to go. Based on qualitative methods of analysis, the guidance strategy and the resulting trajectories were studied. It is shown that these fuel-optimal trajectories effectively assure a vertical soft landing on the asteroid. Results of numerical simulations for the vertical landing, starting from an elliptical orbit are presented.

  12. Optical cavity furnace for semiconductor wafer processing

    DOEpatents

    Sopori, Bhushan L.

    2014-08-05

    An optical cavity furnace 10 having multiple optical energy sources 12 associated with an optical cavity 18 of the furnace. The multiple optical energy sources 12 may be lamps or other devices suitable for producing an appropriate level of optical energy. The optical cavity furnace 10 may also include one or more reflectors 14 and one or more walls 16 associated with the optical energy sources 12 such that the reflectors 14 and walls 16 define the optical cavity 18. The walls 16 may have any desired configuration or shape to enhance operation of the furnace as an optical cavity 18. The optical energy sources 12 may be positioned at any location with respect to the reflectors 14 and walls defining the optical cavity. The optical cavity furnace 10 may further include a semiconductor wafer transport system 22 for transporting one or more semiconductor wafers 20 through the optical cavity.

  13. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... DENTAL DEVICES Prosthetic Devices § 872.3260 Cavity varnish. (a) Identification. Cavity varnish is a... restorative materials. The device is intended to prevent penetration of restorative materials, such as...

  14. 4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe ...

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

    4. VIEW OF VERTICAL BORING MACHINE. (Bullard) Vertical turning lathe (VTL). Machining the fixture for GE Turboshroud. G.S. O'Brien, operator. - Juniata Shops, Machine Shop No. 1, East of Fourth Avenue at Third Street, Altoona, Blair County, PA

  15. Observations of pockmark flow structure in Belfast Bay, Maine, Part 2: evidence for cavity flow

    NASA Astrophysics Data System (ADS)

    Fandel, Christina L.; Lippmann, Thomas C.; Foster, Diane L.; Brothers, Laura L.

    2017-02-01

    Pockmark flow circulation patterns were investigated through current measurements along the rim and center of two pockmarks in Belfast Bay, Maine. Observed time-varying current profiles have a complex vertical and directional structure that rotates significantly with depth and is strongly dependent on the phase of the tide. Observations of the vertical profiles of horizontal velocities in relation to relative geometric parameters of the pockmark are consistent with circulation patterns described qualitatively by cavity flow models (Ashcroft and Zhang 2005). The time-mean behavior of the shear layer is typically used to characterize cavity flow, and was estimated using vorticity thickness to quantify the growth rate of the shear layer horizontally across the pockmark. Estimated positive vorticity thickness spreading rates are consistent with cavity flow predictions, and occur at largely different rates between the two pockmarks. Previously modeled flow (Brothers et al. 2011) and laboratory measurements (Pau et al. 2014) over pockmarks of similar geometry to those examined herein are also qualitatively consistent with cavity flow circulation, suggesting that cavity flow may be a good first-order flow model for pockmarks in general.

  16. Observations of pockmark flow structure in Belfast Bay, Maine, Part 2: evidence for cavity flow

    USGS Publications Warehouse

    Fandel, Christina L.; Lippmann, Thomas C.; Foster, Diane L.; Brothers, Laura L.

    2017-01-01

    Pockmark flow circulation patterns were investigated through current measurements along the rim and center of two pockmarks in Belfast Bay, Maine. Observed time-varying current profiles have a complex vertical and directional structure that rotates significantly with depth and is strongly dependent on the phase of the tide. Observations of the vertical profiles of horizontal velocities in relation to relative geometric parameters of the pockmark are consistent with circulation patterns described qualitatively by cavity flow models (Ashcroft and Zhang 2005). The time-mean behavior of the shear layer is typically used to characterize cavity flow, and was estimated using vorticity thickness to quantify the growth rate of the shear layer horizontally across the pockmark. Estimated positive vorticity thickness spreading rates are consistent with cavity flow predictions, and occur at largely different rates between the two pockmarks. Previously modeled flow (Brothers et al. 2011) and laboratory measurements (Pau et al. 2014) over pockmarks of similar geometry to those examined herein are also qualitatively consistent with cavity flow circulation, suggesting that cavity flow may be a good first-order flow model for pockmarks in general.

  17. Multipacting analysis for JLAB ampere class cavities

    SciTech Connect

    Genfa Wu; Mircea Stirbet; Haipeng Wang; Robert Rimmer; Evan Donoghue

    2005-07-10

    JLAB's ampere class 5-cell cavities require a moderate accelerating gradient (16.7 {approx} 20MV/m). Electron multipacting activity in the machine operating range can degrade the expected performance. A survey was conducted in the area of multipacting analysis for beta=1 electron cavity shapes, including options for the new high current cavity shape. The results obtained provided useful guidance to the final cavity shape adopted and to its expected performance.

  18. Vertical 2D Heterostructures

    NASA Astrophysics Data System (ADS)

    Lotsch, Bettina V.

    2015-07-01

    Graphene's legacy has become an integral part of today's condensed matter science and has equipped a whole generation of scientists with an armory of concepts and techniques that open up new perspectives for the postgraphene area. In particular, the judicious combination of 2D building blocks into vertical heterostructures has recently been identified as a promising route to rationally engineer complex multilayer systems and artificial solids with intriguing properties. The present review highlights recent developments in the rapidly emerging field of 2D nanoarchitectonics from a materials chemistry perspective, with a focus on the types of heterostructures available, their assembly strategies, and their emerging properties. This overview is intended to bridge the gap between two major—yet largely disjunct—developments in 2D heterostructures, which are firmly rooted in solid-state chemistry or physics. Although the underlying types of heterostructures differ with respect to their dimensions, layer alignment, and interfacial quality, there is common ground, and future synergies between the various assembly strategies are to be expected.

  19. Vertically reciprocating auger

    NASA Technical Reports Server (NTRS)

    Etheridge, Mark; Morgan, Scott; Fain, Robert; Pearson, Jonathan; Weldi, Kevin; Woodrough, Stephen B., Jr.

    1988-01-01

    The mathematical model and test results developed for the Vertically Reciprocating Auger (VRA) are summarized. The VRA is a device capable of transporting cuttings that result from below surface drilling. It was developed chiefly for the lunar surface, where conventional fluid flushing while drilling would not be practical. The VRA uses only reciprocating motion and transports material through reflections with the surface above. Particles are reflected forward and land ahead of radially placed fences, which prevent the particles from rolling back down the auger. Three input wave forms are considered to drive the auger. A modified sawtooth wave form was chosen for testing, over a modified square wave or sine wave, due to its simplicity and effectiveness. The three-dimensional mathematical model predicted a sand throughput rate of 0.2667 pounds/stroke, while the actual test setup transported 0.075 pounds/stroke. Based on this result, a correction factor of 0.281 is suggested for a modified sawtooth input.

  20. Modeling and cavity optimization of an external cavity semiconductor laser

    NASA Astrophysics Data System (ADS)

    Feies, Valentin I.; Montrosset, Ivo

    2004-09-01

    Semiconductor external cavity lasers (ECL) have a wide range of applications in the field of DWDM and measurement systems. One of their most important features is the continuous tuning without mode hopping in a wide wavelength range. In this paper we present a modelling approach for an ECL in Littman-Metcalf configuration carried out for optimising: 1) the laser diode position inside the cavity in order to maximize the range of continuous wavelength tuning without mode hopping and without cavity-length adjustment and 2) the choice of the detuning of the operating wavelength respect to the Bragg condition in order to minimize the four-wave mixing (FWM) effects and the effect of a non-perfect antireflection coating (ARC). A realistic example has been analyzed and therefore we considered: the wavelength dependence of the modal gain, linewidth enhancement factor and grating selectivity, as well as the modal refractive index change with carrier injection, operating wavelength and temperature. The implemented numerical tools allow also to obtain some specifications on the grating selectivity and the ARC design.

  1. Discrete wavelength-locked external cavity laser

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S. (Inventor); Silver, Joel A. (Inventor)

    2005-01-01

    An external cavity laser (and method of generating laser light) comprising: a laser light source; means for collimating light output by the laser light source; a diffraction grating receiving collimated light; a cavity feedback mirror reflecting light received from the diffraction grating back to the diffraction grating; and means for reliably tuning the external cavity laser to discrete wavelengths.

  2. Photonic crystal cavities and integrated optical devices

    NASA Astrophysics Data System (ADS)

    Gan, Lin; Li, ZhiYuan

    2015-11-01

    This paper gives a brief introduction to our recent works on photonic crystal (PhC) cavities and related integrated optical structures and devices. Theoretical background and numerical methods for simulation of PhC cavities are first presented. Based on the theoretical basis, two relevant quantities, the cavity mode volume and the quality factor are discussed. Then the methods of fabrication and characterization of silicon PhC slab cavities are introduced. Several types of PhC cavities are presented, such as the usual L3 missing-hole cavity, the new concept waveguide-like parallel-hetero cavity, and the low-index nanobeam cavity. The advantages and disadvantages of each type of cavity are discussed. This will help the readers to decide which type of PhC cavities to use in particular applications. Furthermore, several integrated optical devices based on PhC cavities, such as optical filters, channel-drop filters, optical switches, and optical logic gates are described in both the working principle and operation characteristics. These devices designed and realized in our group demonstrate the wide range of applications of PhC cavities and offer possible solutions to some integrated optical problems.

  3. Power coupler for the ILC crab cavity

    SciTech Connect

    Burt, G.; Dexter, A.; Jenkins, R.; Beard, C.; Goudket, P.; McIntosh, P.A.; Bellantoni, Leo; /Fermilab

    2007-06-01

    The ILC crab cavity will require the design of an appropriate power coupler. The beam-loading in dipole mode cavities is considerably more variable than accelerating cavities, hence simulations have been performed to establish the required external Q. Simulations of a suitable coupler were then performed and were verified using a normal conducting prototype with variable coupler tips.

  4. Many-atom-cavity QED system with homogeneous atom-cavity coupling.

    PubMed

    Lee, Jongmin; Vrijsen, Geert; Teper, Igor; Hosten, Onur; Kasevich, Mark A

    2014-07-01

    We demonstrate a many-atom-cavity system with a high-finesse dual-wavelength standing wave cavity in which all participating rubidium atoms are nearly identically coupled to a 780-nm cavity mode. This homogeneous coupling is enforced by a one-dimensional optical lattice formed by the field of a 1560-nm cavity mode.

  5. Latitude and longitude vertical disparity

    PubMed Central

    Read, Jenny C. A.; Phillipson, Graeme P.; Glennerster, Andrew

    2010-01-01

    The literature on vertical disparity is complicated by the fact that several different definitions of the term “vertical disparity” are in common use, often without a clear statement about which is intended or a widespread appreciation of the properties of the different definitions. Here, we examine two definitions of retinal vertical disparity: elevation-latitude and elevation-longitude disparity. Near the fixation point, these definitions become equivalent, but in general, they have quite different dependences on object distance and binocular eye posture, which have not previously been spelt out. We present analytical approximations for each type of vertical disparity, valid for more general conditions than previous derivations in the literature: we do not restrict ourselves to objects near the fixation point or near the plane of regard, and we allow for non-zero torsion, cyclovergence and vertical misalignments of the eyes. We use these expressions to derive estimates of the latitude and longitude vertical disparity expected at each point in the visual field, averaged over all natural viewing. Finally, we present analytical expressions showing how binocular eye position – gaze direction, convergence, torsion, cyclovergence, and vertical misalignment – can be derived from the vertical disparity field and its derivatives at the fovea. PMID:20055544

  6. Measuring Growth with Vertical Scales

    ERIC Educational Resources Information Center

    Briggs, Derek C.

    2013-01-01

    A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from…

  7. The School Library Vertical File.

    ERIC Educational Resources Information Center

    Smallwood, Carol

    1990-01-01

    Discusses the maintenance of vertical files in the school library. Topics covered include circulation, weeding, using materials for special displays, acquiring materials, policies on advertising and controversial issues, cross-references, subject headings, introducing students to vertical files, beginning a collection, and preservation. (MES)

  8. A micropillar for cavity optomechanics

    SciTech Connect

    Kuhn, Aurélien; Neuhaus, Leonhard; Deléglise, Samuel; Briant, Tristan; Cohadon, Pierre-François; Heidmann, Antoine; Van Brackel, Emmanuel; Chartier, Claude; Ducloux, Olivier; Le Traon, Olivier; Michel, Christophe; Pinard, Laurent; Flaminio, Raffaele

    2014-12-04

    Demonstrating the quantum ground state of a macroscopic mechanical object is a major experimental challenge in physics, at the origin of the rapid emergence of cavity optomechanics. We have developed a new generation of optomechanical devices, based on a microgram quartz micropillar with a very high mechanical quality factor. The structure is used as end mirror in a Fabry-Perot cavity with a high optical finesse, leading to ultra-sensitive interferometric measurement of the resonator displacement. We expect to reach the ground state of this optomechanical resonator by combining cryogenic cooling in a dilution fridge at 30 mK and radiation-pressure cooling. We have already carried out a quantum-limited measurement of the micropillar thermal noise at low temperature.

  9. A micropillar for cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Kuhn, Aurélien; Neuhaus, Leonhard; Van Brackel, Emmanuel; Chartier, Claude; Ducloux, Olivier; Le Traon, Olivier; Michel, Christophe; Pinard, Laurent; Flaminio, Raffaele; Deléglise, Samuel; Briant, Tristan; Cohadon, Pierre-François; Heidmann, Antoine

    2014-12-01

    Demonstrating the quantum ground state of a macroscopic mechanical object is a major experimental challenge in physics, at the origin of the rapid emergence of cavity optomechanics. We have developed a new generation of optomechanical devices, based on a microgram quartz micropillar with a very high mechanical quality factor. The structure is used as end mirror in a Fabry-Perot cavity with a high optical finesse, leading to ultra-sensitive interferometric measurement of the resonator displacement. We expect to reach the ground state of this optomechanical resonator by combining cryogenic cooling in a dilution fridge at 30 mK and radiation-pressure cooling. We have already carried out a quantum-limited measurement of the micropillar thermal noise at low temperature.

  10. Computational fluid dynamics in the oral cavity of ram suspension-feeding fishes.

    PubMed

    Cheer, A Y; Ogami, Y; Sanderson, S L

    2001-06-21

    We have modeled steady, three-dimensional flow with a no-slip boundary condition in cylindrical and conical oral cavities possessing vertical or slanted branchial slits. These numerical simulations illustrate the transport of food particles toward the esophagus, as well as the velocity profiles of water exiting the oral cavity via the branchial slits. The maximum and average velocities are highest for flow exiting the most posterior branchial slit. The highest volume flow rates also occur in the most posterior slit for the cylindrical simulations, but occur in the most anterior slit for the conical simulations. Along the midline, there is a pronounced bilaterally symmetrical vortex in the posterodorsal region of the cylindrical and conical oral cavities and a second bilaterally symmetrical vortex in the posteroventral region of the cylinder. Particles entrained in the vortices will recirculate in the posterior oral cavity, increasing the probability of encounter with sticky, mucus-covered surfaces such as the oral roof, gill arches, or gill rakers. The posterodorsal vortex could serve to concentrate particles near the entrances of the epibranchial organs. The ventral vortex could be involved in sequestering dense inorganic particles that sink toward the floor of the oral cavity. All vortices are absent in the conical simulation with vertical branchial slits, indicating that the slanted branchial slits between the gill arches are responsible for the formation of the vortex in the conical oral cavity. Experiments using in vivo flow visualization techniques are needed to determine whether ram suspension feeders, pump suspension feeders, and non-suspension-feeding fishes possess vortices in the posterior oral cavity that contribute to particle transport, food particle encounter with sticky surfaces, and inorganic particle rejection.

  11. Magnetic spheres in microwave cavities

    NASA Astrophysics Data System (ADS)

    Zare Rameshti, Babak; Cao, Yunshan; Bauer, Gerrit E. W.

    2015-06-01

    We apply Mie scattering theory to study the interaction of magnetic spheres with microwaves in cavities beyond the magnetostatic and rotating wave approximations. We demonstrate that both strong and ultrastrong coupling can be realized for stand alone magnetic spheres made from yttrium iron garnet (YIG), acting as an efficient microwave antenna. The eigenmodes of YIG spheres with radii of the order mm display distinct higher angular momentum character that has been observed in experiments.

  12. Grinding Inside A Toroidal Cavity

    NASA Technical Reports Server (NTRS)

    Mayer, Walter; Adams, James F.; Burley, Richard K.

    1987-01-01

    Weld lines ground smooth within about 0.001 in. Grinding tool for smoothing longitudinal weld lines inside toroidal cavity includes curved tunnel jig to guide grinding "mouse" along weld line. Curvature of tunnel jig matched to shape of toroid so grinding ball in mouse follows circular arc of correct radius as mouse is pushed along tunnel. Tool enables precise control of grindout shape, yet easy to use.

  13. Botryomycosis in a lung cavity

    PubMed Central

    Vinay, D; Ramasubramanian, V; Gopalakrishnan, Ram; Jessani, Laxman G

    2016-01-01

    Botryomycosis is a rare pyogranulomatous disease characterized by suppurative and often granulomatous bacterial infection of the skin, soft tissues and viscera. Only about 90 cases have been reported in world literature till date: 75% of them are cases of cutaneous botryomycosis. Of the 18 reported cases of primary pulmonary botryomycosis, only one had histologically proven botryomycosis in a lung cavity. We report here a case of primary pulmonary botryomycosis occurring in a lung cavity, which is to the best of our knowledge first such case from India. The index case was a 62 year old female who presented to us with recurrent episodes of non-massive streaky hemoptysis with CT chest revealing ‘Air Crescent’ sign with a probable fungal ball in a left upper lobe cavity. Left upper pulmonary lobectomy was done and histopathology of the cavitary tissue revealed Splendore-Hoeppli phenomenon and features suggestive of Botryomycosis. Tissue culture from the cavitary specimen grew Pseudomonas aeruginosa. Botryomycosis can mimic Aspergilloma radiologically as was seen in our case, but therapy is often a combination of both medical and surgical measures unlike Aspergilloma. PMID:27625451

  14. Optomechanic interactions in phoxonic cavities

    SciTech Connect

    Djafari-Rouhani, Bahram; Oudich, Mourad; Pennec, Yan; El-Jallal, Said

    2014-12-15

    Phoxonic crystals are periodic structures exhibiting simultaneous phononic and photonic band gaps, thus allowing the confinement of both excitations in the same cavity. The phonon-photon interaction can be enhanced due to the overlap of both waves in the cavity. In this paper, we discuss some of our recent theoretical works on the strength of the optomechanic coupling, based on both photoelastic and moving interfaces mechanisms, in different (2D, slabs, strips) phoxonic crystals cavities. The cases of two-dimensional infinite and slab structures will enable us to mention the important role of the symmetry and degeneracy of the modes, as well as the role of the materials whose photoelastic constants can be wavelength dependent. Depending on the phonon-photon pair, the photoelastic and moving interface mechanisms can contribute in phase or out-of-phase. Then, the main part of the paper will be devoted to the optomechanic interaction in a corrugated nanobeam waveguide exhibiting dual phononic/photonic band gaps. Such structures can provide photonic modes with very high quality factor, high frequency phononic modes of a few GHz inside a gap and optomechanical coupling rate reaching a few MHz.

  15. Superconducting cavities for particle accelerators

    NASA Astrophysics Data System (ADS)

    Padamsee, H.

    1992-02-01

    RF Superconductivity has become an important technology for particle accelerators for high energy physics, nuclear physics, and free electron lasers. More than 100 MVolts of Superconducting RF (SRF) cavities have been installed in accelerators for heavy ions and operated at gradients of 2-3 MV/m in excess of 105 hours. More than 500 MVolts are installed in electron accelerators and operated at gradients of 4-6 MV/m in excess of 104 hours. Encouraged by this success, another 500 meters of SRF cavities are in the production line. New applications for High Energy Physics are forthcoming for high current e+e- colliders in the B-quark energy range (B-factory). For the next linear collider in the TeV energy range, there are many compelling attractions to use SRF, if the gradients can be improved substantially and the costs lowered. Substantial progress has been made in understanding performance limitations and in inventing cures through better cavity geometries, materials, and processes. Techniques are now in hand to reach 15-20 MV/m accelerating. In light of this progress, the potential of high gradient SRF for a TeV Energy Superconducting Linear Accelerator (TESLA) will be explored.

  16. Acoustic cavity technology for high performance injectors

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The feasibility of damping more than one mode of rocket engine combustion instability by means of differently tuned acoustic cavities sharing a common entrance was shown. Analytical procedures and acoustic modeling techniques for predicting the stability behavior of acoustic cavity designs in hot firings were developed. Full scale testing of various common entrance, dual cavity configurations, and subscale testing for the purpose of obtaining motion pictures of the cavity entrance region, to aid in determining the mechanism of cavity damping were the two major aspects of the program.

  17. Vented Cavity Radiant Barrier Assembly And Method

    DOEpatents

    Dinwoodie, Thomas L.; Jackaway, Adam D.

    2000-05-16

    A vented cavity radiant barrier assembly (2) includes a barrier (12), typically a PV module, having inner and outer surfaces (18, 22). A support assembly (14) is secured to the barrier and extends inwardly from the inner surface of the barrier to a building surface (14) creating a vented cavity (24) between the building surface and the barrier inner surface. A low emissivity element (20) is mounted at or between the building surface and the barrier inner surface. At least part of the cavity exit (30) is higher than the cavity entrance (28) to promote cooling air flow through the cavity.

  18. Controlled directional scattering cavity for tubular absorbers

    DOEpatents

    Winston, Roland

    1982-01-01

    A specular cavity is provided in which an optical receiver is emplaced. The cavity is provided with a series of V groove-like indentations (or pyramidal-type indentations) which redirect energy entering between the receiver and cavity structure onto the receiver. The aperture opening of each V groove is less than half the cavity opening and in most preferred embodiments, much less than half. This enables the optical receiver to be emplaced a distance g from the cavity wherein 0.414r

  19. LHC crab-cavity aspects and strategy

    SciTech Connect

    Calaga, R.; Tomas, R.; Zimmermann, F.

    2010-05-23

    The 3rd LHC Crab Cavity workshop (LHC-CC09) took place at CERN in October 2009. It reviewed the current status and identified a clear strategy towards a future crab-cavity implementation. Following the success of crab cavities in KEK-B and the strong potential for luminosity gain and leveling, CERN will pursue crab crossing for the LHC upgrade. We present a summary and outcome of the variousworkshop sessions which have led to the LHC crab-cavity strategy, covering topics like layout, cavity design, integration, machine protection, and a potential validation test in the SPS.

  20. Novel Geometries for the LHC Crab Cavity

    SciTech Connect

    Hall, B.; Burt, G.; Smith, J. D.A.; Rimmer, R.; Wang, H.; Delayen, J.; Calaga, R.

    2009-05-01

    In 2017 the LHC is envisioned to increase its luminosity via an upgrade. This upgrade is likely to require a large crossing angle hence a crab cavity is required to align the bunches prior to collision. There are two possible schemes for crab cavity implementation, global and local. In a global crab cavity the crab cavity is far from the IP and the bunch rotates back and forward as it traverses around the accelerator in a closed orbit. For this scheme a two-cell elliptical squashed cavity at 800 MHz is preferred. To avoid any potential beam instabilities all the parasitic modes of the cavities must be damped strongly, however crab cavities have lower order and same order modes in addition to the usual higher order modes and hence a novel damping scheme must be used to provide sufficient damping of these modes. In the local scheme two crab cavities are placed at each side of the IP two start and stop rotation of the bunches. This would require crab cavities much smaller transversely than in the global scheme but the frequency cannot be increased any higher due to the long bunch length of the LHC beam. This will require a novel compact crab cavity design. A superconducting version of a two rod coaxial deflecting cavity as a suitable design is proposed in this paper.

  1. Control of Cavity Resonance Using Oscillatory Blowing

    NASA Technical Reports Server (NTRS)

    Scarfe, Alison Lamp; Chokani, Ndaona

    2000-01-01

    The near-zero net mass oscillatory blowing control of a subsonic cavity flow has been experimentally investigated. An actuator was designed and fabricated to provide both steady and oscillatory blowing over a range of blowing amplitudes and forcing frequencies. The blowing was applied just upstream of the cavity front Wall through interchangeable plate configurations These configurations enabled the effects of hole size, hole shape, and blowing angle to be examined. A significant finding is that in terms of the blowing amplitude, the near zero net mass oscillatory blowing is much more effective than steady blowing; momentum coefficients Lip two orders of magnitude smaller than those required for steady blowing are sufficient to accomplish the same control of cavity resonance. The detailed measurements obtained in the experiment include fluctuating pressure data within the cavity wall, and hot-wire measurements of the cavity shear layer. Spectral and wavelet analysis techniques are applied to understand the dynamics and mechanisms of the cavity flow with control. The oscillatory blowing, is effective in enhancing the mixing in the cavity shear layer and thus modifying the feedback loop associated with the cavity resonance. The nonlinear interactions in the cavity flow are no longer driven by the resonant cavity modes but by the forcing associated with the oscillatory blowing. The oscillatory blowing does not suppress the mode switching behavior of the cavity flow, but the amplitude modulation is reduced.

  2. Plasmonic Coupled Cavities on Moire Surfaces

    NASA Astrophysics Data System (ADS)

    Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla

    2010-03-01

    We investigate surface plasmon polariton (SPP) coupled cavity modes on Moire surfaces. An experimental study has been made of the propagation of SPPs on a thin silver surface that is textured with Moire surface pattern using interference lithography. The Moire surface contains periodic array of one dimensional cavities. The distance between the cavities can be controlled by changing the periodicities of Moire surface. When the SPP cavity separation is sufficiently small, we show splitting of strongly coupled plasmonic cavity modes through numerical simulations. Conversely, when the SPP cavity separation is sufficiently large, SPP cavity modes are found to be localized and do not show splitting of SPP cavity modes . This splitting of SPP cavity modes are well explained with a tight binding model that has been succesfully applied in photonic coupled cavities. Reflection measurements and numerical simulation of a large number of adjacent SPP cavities have shown a coupled resonator optical waveguide (CROW) type plasmonic waveguide band formation within the band gap region of unperturbed uniform grating.

  3. Novel Geometries for the LHC Crab Cavity

    SciTech Connect

    B. Hall,G. Burt,C. Lingwood,Robert Rimmer,Haipeng Wang; Hall, B.; Burt, G.; Lingwood, C.; Rimmer, Robert; Wang, Haipeng

    2010-05-01

    The planned luminosity upgrade to LHC is likely to necessitate a large crossing angle and a local crab crossing scheme. For this scheme crab cavities align bunches prior to collision. The scheme requires at least four such cavities, a pair on each beam line either side of the interaction point (IP). Upstream cavities initiate rotation and downstream cavities cancel rotation. Cancellation is usually done at a location where the optics has re-aligned the bunch. The beam line separation near the IP necessitates a more compact design than is possible with elliptical cavities such as those used at KEK. The reduction in size must be achieved without an increase in the operational frequency to maintain compatibility with the long bunch length of the LHC. This paper proposes a suitable superconducting variant of a four rod coaxial deflecting cavity (to be phased as a crab cavity), and presents analytical models and simulations of suitable designs.

  4. Novel Geometries for the LHC Crab Cavity

    SciTech Connect

    B. Hall, G. Burt, C. Lingwood, R. Rimmer, H. Wang

    2010-05-23

    The planned luminosity upgrade to LHC is likely to necessitate a large crossing angle and a local crab crossing scheme. For this scheme crab cavities align bunches prior to collision. The scheme requires at least four such cavities, a pair on each beam line either side of the interaction point (IP). Upstream cavities initiate rotation and downstream cavities cancel rotation. Cancellation is usually done at a location where the optics has re-aligned the bunch. The beam line separation near the IP necessitates a more compact design than is possible with elliptical cavities such as those used at KEK. The reduction in size must be achieved without an increase in the operational frequency to maintain compatibility with the long bunch length of the LHC. This paper proposes a suitable superconducting variant of a four rod coaxial deflecting cavity (to be phased as a crab cavity), and presents analytical models and simulations of suitable designs.

  5. Shape Determination for Deformed Electromagnetic Cavities

    SciTech Connect

    Akcelik, Volkan; Ko, Kwok; Lee, Lie-Quan; Li, Zhenghai; Ng, Cho-Kuen; Xiao, Liling; /SLAC

    2007-12-10

    The measured physical parameters of a superconducting cavity differ from those of the designed ideal cavity. This is due to shape deviations caused by both loose machine tolerances during fabrication and by the tuning process for the accelerating mode. We present a shape determination algorithm to solve for the unknown deviations from the ideal cavity using experimentally measured cavity data. The objective is to match the results of the deformed cavity model to experimental data through least-squares minimization. The inversion variables are unknown shape deformation parameters that describe perturbations of the ideal cavity. The constraint is the Maxwell eigenvalue problem. We solve the nonlinear optimization problem using a line-search based reduced space Gauss-Newton method where we compute shape sensitivities with a discrete adjoint approach. We present two shape determination examples, one from synthetic and the other from experimental data. The results demonstrate that the proposed algorithm is very effective in determining the deformed cavity shape.

  6. Vertical bloch line memory

    NASA Technical Reports Server (NTRS)

    Katti, R.; Wu, J.; Stadler, H.

    1990-01-01

    Vertical Bloch Line (VBL) memory is a recently conceived, integrated, solid-state, block-access, VLSI memory which offers the potential of 1Gbit/sq cm real storage density, gigabit per second data rates, and sub-millisecond average access times simultaneously at relatively low mass, volume, and power values when compared to alternative technologies. VBL's are micromagnetic structures within magnetic domain walls which can be manipulated using magnetic fields from integrated conductors. The presence or absence of VBL pairs are used to store binary information. At present, efforts are being directed at developing a single-chip memory using 25Mbit/sq cm technology in magnetic garnet material which integrates, at a single operating point, the writing, storage, reading, and amplification functions needed in a memory. This paper describes the current design architecture, functional elements, and supercomputer simulation results which are used to assist the design process. The current design architecture uses three metal layers, two ion implantation steps for modulating the thickness of the magnetic layer, one ion implantation step for assisting propagation in the major line track, one NiFe soft magnetic layer, one CoPt hard magnetic layer, and one reflective Cr layer for facilitating magneto-optic observation of magnetic structure. Data are stored in a series of elongated magnetic domains, called stripes, which serve as storage sites for arrays of VBL pairs. The ends of these stripes are placed near conductors which serve as VBL read/write gates. A major line track is present to provide a source and propagation path for magnetic bubbles. Writing and reading, respectively, are achieved by converting magnetic bubbles to VBL's and vice versa. The output function is effected by stretching a magnetic bubble and detecting it magnetoresistively. Experimental results from the past design cycle created four design goals for the current design cycle. First, the bias field ranges

  7. Cavity Optomechanics at Millikelvin Temperatures

    NASA Astrophysics Data System (ADS)

    Meenehan, Sean Michael

    The field of cavity optomechanics, which concerns the coupling of a mechanical object's motion to the electromagnetic field of a high finesse cavity, allows for exquisitely sensitive measurements of mechanical motion, from large-scale gravitational wave detection to microscale accelerometers. Moreover, it provides a potential means to control and engineer the state of a macroscopic mechanical object at the quantum level, provided one can realize sufficiently strong interaction strengths relative to the ambient thermal noise. Recent experiments utilizing the optomechanical interaction to cool mechanical resonators to their motional quantum ground state allow for a variety of quantum engineering applications, including preparation of non-classical mechanical states and coherent optical to microwave conversion. Optomechanical crystals (OMCs), in which bandgaps for both optical and mechanical waves can be introduced through patterning of a material, provide one particularly attractive means for realizing strong interactions between high-frequency mechanical resonators and near-infrared light. Beyond the usual paradigm of cavity optomechanics involving isolated single mechanical elements, OMCs can also be fashioned into planar circuits for photons and phonons, and arrays of optomechanical elements can be interconnected via optical and acoustic waveguides. Such coupled OMC arrays have been proposed as a way to realize quantum optomechanical memories, nanomechanical circuits for continuous variable quantum information processing and phononic quantum networks, and as a platform for engineering and studying quantum many-body physics of optomechanical meta-materials. However, while ground state occupancies (that is, average phonon occupancies less than one) have been achieved in OMC cavities utilizing laser cooling techniques, parasitic absorption and the concomitant degradation of the mechanical quality factor fundamentally limit this approach. On the other hand, the high

  8. Quantum dot insertions in VCSELs from 840 to 1300 nm: growth, characterization, and device performance

    NASA Astrophysics Data System (ADS)

    Ledentsov, N. N.; Lott, J. A.; Shchukin, V. A.; Quast, H.; Hopfer, F.; Fiol, G.; Mutig, A.; Moser, P.; Germann, T.; Strittmatter, A.; Karachinsky, L. Y.; Blokhin, S. A.; Novikov, I. I.; Nadtochi, A. M.; Zakharov, N. D.; Werner, P.; Bimberg, D.

    2009-02-01

    Presently VCSELs covering a significant spectral range (840-1300 nm) can be produced based on quantum dot (QD) active elements. Herein we report progress on selected QD based vertical-cavity surface-emitting lasers (VCSELs) suitable for high-speed operation. An open eye diagram at 20 Gb/s with error-free transmission (a bit-error-rate < 10-15) is achieved at 850 nm. The 850 nm QD VCSELs also achieve error-free 20 Gb/s single mode transmission operation through multimode fiber without the use of optical isolation. Our 980 nm-range QD VCSELs achieve error free transmission at 25 Gb/s at up to 150°C. These 980 nm devices operate in a temperature range of 25-85°C without current or modulation voltage adjustment. We anticipate that the primary application areas of QD VCSELs are those that require degradation-robust operation under extremely high current densities. Temperature stability at ultrahigh current densities, a forte of QDs, is needed for ultrahigh-speed (> 40 Gb/s) current-modulated VCSELs for a new generation of local and storage area networks. Finally we discuss aspects of QD vertical extended-cavity surface emitting lasers with ultra high power density per emitting surface for high power (material processing) and frequency conversion (display) applications.

  9. Performance of a CEBAF production cavity after high-temperature heat treatment

    SciTech Connect

    Kneisel, P.; Rao, M.

    1993-06-01

    CEBAF`s production cavities are tested in a vertical configuration after appropriate chemical surface treatment prior to installation into the accelerator. The performance of these cavities is excellent, often exceeding the specifications of E{sub acc}=5 MV/m at 2 K by factors of 2 to 3. In such cases the cavities are often limited by thermal-magnetic breakdown. A cavity that exhibited a limiting gradient of E{sub acc} {le} 16.4 MV/m has been heat-treated at 1400{degrees}C for 6 hours in the presence of titanium as a solid state gettering material to improve the thermal stability of the niobium. After the heat treatment a gradient of E{sub acc}=20.5 MV/m corresponding to a peak surface electric field of E{sub peak}=52 MV/m has been measured. In addition to the cavity results, data on thermal conductivity and tensile properties of samples which have undergone the same treatments as the cavity are reported.

  10. Cavities

    MedlinePlus

    ... decay at an early stage helps maintain the strength of the tooth and limits the chance of damage to the pulp. Fillings Fillings are made of various materials and may be put inside the tooth or ...

  11. X-Band Crab Cavities for the CLIC Beam Delivery System

    SciTech Connect

    Burt, G.; Ambattu, P.K.; Dexter, A.C.; Abram, T.; Dolgashev, V.; Tantawi, S.; Jones, R.M.; /Cockcroft Inst. Accel. Sci. Tech. /Manchester U.

    2011-11-22

    The CLIC machine incorporates a 20 mrad crossing angle at the IP to aid the extraction of spent beams. In order to recover the luminosity lost through the crossing angle a crab cavity is proposed to rotate the bunches prior to collision. The crab cavity is chosen to have the same frequency as the main linac (11.9942 GHz) as a compromise between size, phase stability requirements and beam loading. It is proposed to use a HE11 mode travelling wave structure as the CLIC crab cavity in order to minimise beam loading and mode separation. The position of the crab cavity close to the final focus enhances the effect of transverse wake-fields so effective wake-field damping is required. A damped detuned structure is proposed to suppress and de-cohere the wake-field hence reducing their effect. Design considerations for the CLIC crab cavity will be discussed as well as the proposed high power testing of these structures at SLAC. Design of a crab cavity for CLIC is underway at the Cockcroft Institute in collaboration with SLAC. This effort draws on a large degree of synergy with the ILC crab cavity developed at the Cockcroft Institute and other deflecting structure development at SLAC. A study of phase and amplitude variations in the cavity suggests that the tolerances are very tight and require a 'beyond state of the art' LLRF control system. A study of cavity geometry and its effect on the cavity fields has been performed using Microwave studio. This study has suggested that for our cavity an iris radius between 4-5 mm is optimum with an iris thickness of 2-3 mm based on group velocity and peak fields. A study of the cavity wakefields show that the single bunch wakes are unlikely to be a problem but the short bunch spacing may cause the multi-bunch wakefields to be an issue. This will require some of the modes to be damped strongly so that the wake is damped significantly before any following bunch arrives. Various methods of damping have been investigated and suggest that

  12. Vertical Beam Polarization at MAMI

    NASA Astrophysics Data System (ADS)

    Schlimme, B. S.; Achenbach, P.; Aulenbacher, K.; Baunack, S.; Bender, D.; Beričič, J.; Bosnar, D.; Correa, L.; Dehn, M.; Distler, M. O.; Esser, A.; Fonvieille, H.; Friščić, I.; Gutheil, B.; Herrmann, P.; Hoek, M.; Kegel, S.; Kohl, Y.; Kolar, T.; Kreidel, H.-J.; Maas, F.; Merkel, H.; Mihovilovič, M.; Müller, J.; Müller, U.; Nillius, F.; Nuck, A.; Pochodzalla, J.; Schoth, M.; Schulz, F.; Sfienti, C.; Širca, S.; Spruck, B.; Štajner, S.; Thiel, M.; Tioukine, V.; Tyukin, A.; Weber, A.

    2017-04-01

    For the first time a vertically polarized electron beam has been used for physics experiments at MAMI in the energy range between 180 and 855 MeV. The beam-normal single-spin asymmetry An, which is a direct probe of higher-order photon exchange beyond the first Born approximation, has been measured in the reaction 12C (e → , e ‧)12C . Vertical polarization orientation was necessary to measure this asymmetry with the existing experimental setup. In this paper we describe the procedure to orient the electron polarization vector vertically, and the concept of determining both its magnitude and orientation with the available setup. A sophisticated method has been developed to overcome the lack of a polarimeter setup sensitive to the vertical polarization component.

  13. Vertical axis wind turbine airfoil

    DOEpatents

    Krivcov, Vladimir; Krivospitski, Vladimir; Maksimov, Vasili; Halstead, Richard; Grahov, Jurij Vasiljevich

    2012-12-18

    A vertical axis wind turbine airfoil is described. The wind turbine airfoil can include a leading edge, a trailing edge, an upper curved surface, a lower curved surface, and a centerline running between the upper surface and the lower surface and from the leading edge to the trailing edge. The airfoil can be configured so that the distance between the centerline and the upper surface is the same as the distance between the centerline and the lower surface at all points along the length of the airfoil. A plurality of such airfoils can be included in a vertical axis wind turbine. These airfoils can be vertically disposed and can rotate about a vertical axis.

  14. Vertically scanned laser sheet microscopy.

    PubMed

    Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

    2014-01-01

    Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction.

  15. High Q-factor colloidal nanocrystal-based vertical microcavity by hot embossing technology

    NASA Astrophysics Data System (ADS)

    Martiradonna, Luigi; Carbone, Luigi; De Giorgi, Milena; Manna, Liberato; Gigli, Giuseppe; Cingolani, Roberto; De Vittorio, Massimo

    2006-05-01

    We report on the fabrication and optical characterization of vertical hybrid microcavities in which a layer of colloidal nanocrystals dispersed in an organic matrix is embedded between two inorganic mirrors. The devices are fabricated by a technique based on the unconventional use of the hot embossing technology, which allows a very fine control of the cavity length. The technique exploits a λ-thick microstructured dielectric top mirror pressed onto the bottom one, previously coated with the active layer, to sandwich the cavity and precisely control its thickness. Room-temperature photoluminescence measurements show a Q factor as high as 146 for our devices.

  16. Tumours of the nasal cavity*

    PubMed Central

    Stünzi, H.; Hauser, B.

    1976-01-01

    Tumours of the nasal cavity are rare in domestic animals, most cases occurring in the dog. Epithelial tumours are the most common type in carnivores (dogs and cats). In general, the same types of tumour occur in domestic animals as occur in man. There was no significant predisposition for breed in dogs, but in both dogs and cats far more males than females were affected. Metastases occurred only rarely. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 9Fig. 10Fig. 11Fig. 12Fig. 5Fig. 6Fig. 7Fig. 8 PMID:1086156

  17. Cancer of the oral cavity.

    PubMed

    Montero, Pablo H; Patel, Snehal G

    2015-07-01

    Cancer of the oral cavity is one of the most common malignancies worldwide. Although early diagnosis is relatively easy, presentation with advanced disease is not uncommon. The standard of care is primary surgical resection with or without postoperative adjuvant therapy. Improvements in surgical techniques combined with the routine use of postoperative radiation or chemoradiation therapy have resulted in improved survival. Successful treatment is predicated on multidisciplinary treatment strategies to maximize oncologic control and minimize impact of therapy on form and function. Prevention of oral cancer requires better education about lifestyle-related risk factors, and improved awareness and tools for early diagnosis.

  18. [Dirofilaria in the abdominal cavity].

    PubMed

    Révész, Erzsébet; Markovics, Gabriella; Darabos, Zoltán; Tóth, Ildikó; Fok, Eva

    2008-10-01

    Number of cases of filariasis have been recently reported in the Hungarian medical literature, most of them caused by Dirofilaria repens . Dirofilaria repens is a mosquito-transmitted filarioid worm in the subcutaneous tissue of dogs and cats. Human infection manifests as either subcutaneous nodules or lung parenchymal disease, which may even be asymptomatic. The authors report a human Dirofilaria repens infection of the abdominal cavity in a 61-year-old man,who underwent laparotomy for acute abdomen. Intraoperatively, local peritonitis was detected caused by a white nemathhelminth, measured 8 cm in size. Histocytology confirmed that the infection was caused by Dirofilaria repens.

  19. Mass renormalization in cavity QED

    SciTech Connect

    Matloob, Reza

    2011-01-15

    We show that the presence of a background medium and a boundary surface or surfaces in cavity QED produces no change in the energy shift of a free charged particle due to its coupling to the fluctuating electromagnetic field of the vacuum. This clarifies that the electromagnetic and the observed mass of the charged particle are not affected by the modification of the field of the vacuum. The calculations are nonrelativistic and restricted to the dipole approximation but are otherwise based on the general requirements of causality.

  20. Basketballs as spherical acoustic cavities

    NASA Astrophysics Data System (ADS)

    Russell, Daniel A.

    2010-06-01

    The sound field resulting from striking a basketball is found to be rich in frequency content, with over 50 partials in the frequency range of 0-12 kHz. The frequencies are found to closely match theoretical expectations for standing wave patterns inside a spherical cavity. Because of the degenerate nature of the mode shapes, explicit identification of the modes is not possible without internal investigation with a microphone probe. A basketball proves to be an interesting application of a boundary value problem involving spherical coordinates.

  1. Cavity-based high-efficiency and wideband 90° polarization rotator

    NASA Astrophysics Data System (ADS)

    Wang, Jiang; Shen, Zhongxiang; Wu, Wen

    2016-10-01

    We present a high-efficiency wideband 90° polarization rotator based on 2D array of substrate integrated waveguide cavities etched with three twisted slots, which can rotate a horizontally polarized incident wave into an outgoing vertically polarized wave. The twisted slots etched on the surface of the cavity are utilized to couple the wave into and out of the cavity with the polarization direction rotated. As a proof-of-concept, a prototype of the proposed rotator is fabricated and measured in the microwave regime. The proposed 90° polarization rotator features a low insertion loss of about 0.5 dB in the pass band with a factional bandwidth of 28.6%, as well as high polarization rotation efficiency of over 90%.

  2. Experimental and analytical study of contact melting in a rectangular cavity

    NASA Astrophysics Data System (ADS)

    Dong, Z. F.; Chen, Z. Q.; Wang, Q. J.; Ebadian, M. A.

    1991-09-01

    A detailed investigation is presented of analytical and experimental findings for contact melting in a rectangular cavity for the phase change materials n-heptadecane and n-eicosane. The temperature of the two side walls and bottom surface of the cavity are maintained by circulating water through a highly sensitive thermostat. The other surfaces are subjected to adiabatic conditions. The time-dependent solid-liquid interface contour is measured photographically during the melting process. The experimental data, such as the melting rate and the dimensionless height of the solid, are compared with predicted values of the theoretical model, and good agreement is observed. It is demonstrated that the height of the microchannel at the bottom is constant. This shows that the heat transfer across the channel is dominated by conduction. Results also indicate that the melting on the vertical wall is controlled by conduction. It is concluded, therefore, that heat conduction is the main contact melting mechanism in a rectangular cavity.

  3. EVALUATION OF SILICON DIODES AS IN-SITU CRYOGENIC FIELD EMISSION DETECTORS FOR SRF CAVITY DEVELOPMENT

    SciTech Connect

    Ari Palczewski, Rongli Geng

    2012-07-01

    We performed in-situ cryogenic testing of four silicon diodes as possible candidates for field emission (FE) monitors of superconducting radio frequency (SRF) cavities during qualification testing and in accelerator cryo-modules. We evaluated diodes from 2 companies - from Hamamatsu corporation model S1223-01; and from OSI Optoelectronics models OSD35-LR-A, XUV-50C, and FIL-UV20. The measurements were done by placing the diodes in superfluid liquid helium near the top of a field emitting 9-cell cavity during its vertical test. For each diode, we will discuss their viability as a 2K cryogenic detector for FE mapping of SRF cavities and the directionality of S1223-01 in such environments. We will also present calibration curves between the diodes and JLab's standard radiation detector placed above the Dewar's top plate.

  4. A note on multiple and unsteady solutions in two-dimensional convection in a tall cavity

    SciTech Connect

    Le Quere, P. )

    1990-11-01

    Two-dimensional natural convection in a vertical differentially heated air-filled cavity is investigated numerically from the onset of the multicellular flow structure to the return of the unicellular pattern. Several branches of solutions characterized by different numbers of cells in the flow structure are found. The return to the unicellular flow structure occurs through a gradual decrease in the number of cells and each change in the number of cells is characterized by hysteresis. Also, unsteady solutions are found.

  5. Performance of Single Crystal Niobium Cavities

    SciTech Connect

    Kneisel, Peter; Ciovati, Gianluigi; Singer, Waldemar; Singer, Xenia; Reschke, Detlef; Brinkmann, A.

    2008-07-01

    We have fabricated and tested a total of six single cell niobium cavities, made from single crystal, high purity niobium. Two of the three cavities of the TESLA shape (1300 MHz) were made from Heraeus niobium by extending a smaller single crystal by rolling and annealing steps; the third cavity was made by spinning from CBMM material. The three other cavities of the scaled "Low Loss" (LL) shape (two) and "High Gradient" (HG) shape (one) resonated at 2.3 GHz and were fabricated from "as received" single crystals, both from Heraeus and CBMM niobium. After appropriate surface treatments by buffered chemical polishing and electropolishing most cavities performed quite nicely and peak surface magnetic fields of ~ 160 mT or above corresponding to accelerating gradients between 38 MV/m and 45 MV/m were reached. This paper reports about the performance of these cavities.

  6. Subwavelength Nanopatch Cavities for Semiconductor Plasmon Lasers

    NASA Astrophysics Data System (ADS)

    Manolatou, Christina; Rana, Farhan

    2008-05-01

    We propose and analyze a family of nanoscale cavities for electrically-pumped surface-emitting semiconductor lasers that use surface plasmons to provide optical mode confinement in cavities which have dimensions in the 100-300 nm range. The proposed laser cavities are in many ways nanoscale optical versions of micropatch antennas that are commonly used at microwave/RF frequencies. Surface plasmons are not only used for mode confinement but also for output beam shaping to realize single-lobe far-field radiation patterns with narrow beam waists from subwavelength size cavities. We identify the cavity modes with the largest quality factors and modal gain, and show that in the near-IR wavelength range (1.0-1.6 microns) cavity losses (including surface plasmon losses) can be compensated by the strong mode confinement in the gain region provided by the surface plasmons themselves and the required material threshold gain values can be smaller than 700 1/cm.

  7. Cavity-enhanced spectroscopy in optical fibers.

    PubMed

    Gupta, Manish; Jiao, Hong; O'Keefe, Anthony

    2002-11-01

    Cavity-enhanced methods have been extended to fiber optics by use of fiber Bragg gratings (FBGs) as reflectors. High-finesse fiber cavities were fabricated from FBGs made in both germanium/boron-co-doped photosensitive fiber and hydrogen-loaded Corning SMF-28 fiber. Optical losses in these cavities were determined from the measured Fabry-Perot transmission spectra and cavity ring-down spectroscopy. For a 10-m-long single-mode fiber cavity, ring-down times in excess of 2 ms were observed at 1563.6 nm, and individual laser pulses were resolved. An evanescent-wave access block was produced within a fiber cavity, and an enhanced sensitivity to optical loss was observed as the external medium's refractive index was altered.

  8. Turbine disk cavity aerodynamics and heat transfer

    NASA Technical Reports Server (NTRS)

    Johnson, B. V.; Daniels, W. A.

    1992-01-01

    Experiments were conducted to define the nature of the aerodynamics and heat transfer for the flow within the disk cavities and blade attachments of a large-scale model, simulating the Space Shuttle Main Engine (SSME) turbopump drive turbines. These experiments of the aerodynamic driving mechanisms explored the following: (1) flow between the main gas path and the disk cavities; (2) coolant flow injected into the disk cavities; (3) coolant density; (4) leakage flows through the seal between blades; and (5) the role that each of these various flows has in determining the adiabatic recovery temperature at all of the critical locations within the cavities. The model and the test apparatus provide close geometrical and aerodynamic simulation of all the two-stage cavity flow regions for the SSME High Pressure Fuel Turbopump and the ability to simulate the sources and sinks for each cavity flow.

  9. Cavity-Dumped Communication Laser Design

    NASA Technical Reports Server (NTRS)

    Roberts, W. T.

    2003-01-01

    Cavity-dumped lasers have significant advantages over more conventional Q-switched lasers for high-rate operation with pulse position modulation communications, including the ability to emit laser pulses at 1- to 10-megahertz rates, with pulse widths of 0.5 to 5 nanoseconds. A major advantage of cavity dumping is the potential to vary the cavity output percentage from pulse to pulse, maintaining the remainder of the energy in reserve for the next pulse. This article presents the results of a simplified cavity-dumped laser model, establishing the requirements for cavity efficiency and projecting the ultimate laser efficiency attainable in normal operation. In addition, a method of reducing or eliminating laser dead time is suggested that could significantly enhance communication capacity. The design of a laboratory demonstration laser is presented with estimates of required cavity efficiency and demonstration potential.

  10. Rebuild of Capture Cavity 1 at Fermilab

    SciTech Connect

    Harms, E.; Arkan, T.; Borissov, E.; Dhanaraj, N.; Hocker, A.; Orlov, Y.; Peterson, T.; Premo, K.

    2014-01-01

    The front end of the proposed Advanced Superconducting Test Accelerator at Fermilab employs two single cavity cryomodules, known as 'Capture Cavity 1' and 'Capture Cavity 2', for the first stage of acceleration. Capture Cavity 1 was previously used as the accelerating structure for the A0 Photoinjector to a peak energy of ~14 MeV. In its new location a gradient of ~25 MV/m is required. This has necessitated a major rebuild of the cryomodule including replacement of the cavity with a higher gradient one. Retrofitting the cavity and making upgrades to the module required significant redesign. The design choices and their rationale, summary of the rebuild, and early test results are presented.

  11. Coupled-cavity drift-tube linac

    DOEpatents

    Billen, James H.

    1996-01-01

    A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the .pi.-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is .beta..lambda., where .lambda. is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a .pi./2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range.

  12. Coupled-cavity drift-tube linac

    DOEpatents

    Billen, J.H.

    1996-11-26

    A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the {pi}-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is {beta}{lambda}, where {lambda} is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a {pi}/2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range. 5 figs.

  13. Experimental and numerical analysis of convective flow in a square cavity with internal protuberances

    NASA Astrophysics Data System (ADS)

    Lizardi, A.; Terres, H.; López, R.; Vaca, M.; Chávez., S.; Lara, A.; Morales, J. R.

    2017-01-01

    A comparison between experimental and numerical results for natural convection flow generated inside a square cavity filled with water, which has internal protuberances, is presented. The cavity is formed by vertical-isothermal and horizontal-adiabatic walls. The built prototype is integrated by: a clear glass square cavity, where internal protuberances are located; a cavity with water which maintains one of its walls at low temperature; an electrical resistance which preserves another wall at high temperature; and an array of mirrors. The experimental flow development was studied with a Particle Image Velocimetry (PIV) device. Furthermore, ANSYS software was used and mass, momentum and energy equations were numerically solved. Results were compared using a system with rectangular, semi-circular, and triangular protuberances versus a system without protuberances; it was found that: a) the maximum positive value of the vertical velocity decreased 7.12, 3.33 and 3.03%, respectively, for the experimental case, and 4.52, 2.26 and 1.27%, respectively, for the numerical case; b) the maximum positive value of the horizontal velocity decreased 18.37, 11.89 and 4.59%, respectively, for the experimental case, and 6.46, 4.75 and 2.47%, respectively, for the numerical case; c) the average Nusselt number decreased 10.52, 7.95 and 6.06%, respectively, for the experimental case, and 12.01, 9.06 and 3.02%, respectively, for the numerical case.

  14. Breakthrough: Record-Setting Cavity

    ScienceCinema

    Ciovati, Gianluigi

    2016-07-12

    Gianluigi "Gigi" Ciovati, a superconducting radiofrequency scientist, discusses how scientists at the U.S. Department of Energy's Jefferson Lab in Newport News, VA, used ARRA funds to fabricate a niobium cavity for superconducting radiofrequency accelerators that has set a world record for energy efficiency. Jefferson Lab's scientists developed a new, super-hot treatment process that could soon make it possible to produce cavities more quickly and at less cost, benefitting research and healthcare around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.

  15. SPINNING MOTIONS IN CORONAL CAVITIES

    SciTech Connect

    Wang, Y.-M.; Stenborg, G. E-mail: guillermo.stenborg.ctr.ar@nrl.navy.mi

    2010-08-20

    In movies made from Fe XII 19.5 nm images, coronal cavities that graze or are detached from the solar limb appear as continually spinning structures, with sky-plane projected flow speeds in the range 5-10 km s{sup -1}. These whirling motions often persist in the same sense for up to several days and provide strong evidence that the cavities and the immediately surrounding streamer material have the form of helical flux ropes viewed along their axes. A pronounced bias toward spin in the equatorward direction is observed during 2008. We attribute this bias to the poleward concentration of the photospheric magnetic flux near sunspot minimum, which leads to asymmetric heating along large-scale coronal loops and tends to drive a flow from higher to lower latitudes; this flow is converted into an equatorward spinning motion when the loops pinch off to form a flux rope. As sunspot activity increases and the polar fields weaken, we expect the preferred direction of the spin to reverse.

  16. Breakthrough: Record-Setting Cavity

    SciTech Connect

    Ciovati, Gianluigi

    2012-03-01

    Gianluigi "Gigi" Ciovati, a superconducting radiofrequency scientist, discusses how scientists at the U.S. Department of Energy's Jefferson Lab in Newport News, VA, used ARRA funds to fabricate a niobium cavity for superconducting radiofrequency accelerators that has set a world record for energy efficiency. Jefferson Lab's scientists developed a new, super-hot treatment process that could soon make it possible to produce cavities more quickly and at less cost, benefitting research and healthcare around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.around the world. Accelerators are critical to our efforts to study the structure of matter that builds our visible universe. They also are used to produce medical isotopes and particle beams for diagnosing and eradicating disease. And they offer the potential to power future nuclear power plants that produce little or no radioactive waste.

  17. Compact Superconducting Crabbing and Deflecting Cavities

    SciTech Connect

    De Silva, Payagalage Subashini Uddika

    2012-09-01

    Recently, new geometries for superconducting crabbing and deflecting cavities have been developed that have significantly improved properties over those the standard TM{sub 110} cavities. They are smaller, have low surface fields, high shunt impedance and, more importantly for some of them, no lower-order-mode with a well-separated fundamental mode. This talk will present the status of the development of these cavities.

  18. Continuously tunable, split-cavity gyrotrons

    NASA Astrophysics Data System (ADS)

    Brand, G. F.; Gross, M.

    1985-12-01

    Attention is given to a gyrotron cavity configuration which is split in halves longitudinally, to allow any frequency lying between the fixed cavity resonance to be assessed by mechanically changing the separation of the two halves. Experimental results are presented which demonstrate that the rate-of-change in resonant frequency with separation is greatest if the minor axis of the cavity cross section is the one undergoing change. Excellent agreement with theory is noted for these results.

  19. Resonant-cavity antenna for plasma heating

    DOEpatents

    Perkins, Jr., Francis W.; Chiu, Shiu-Chu; Parks, Paul; Rawls, John M.

    1987-01-01

    Disclosed is a resonant coil cavity wave launcher for energizing a plasma immersed in a magnetic field. Energization includes launching fast Alfven waves to excite ion cyclotron frequency resonances in the plasma. The cavity includes inductive and capacitive reactive members spaced no further than one-quarter wavelength from a first wall confinement chamber of the plasma. The cavity wave launcher is energized by connection to a waveguide or transmission line carrying forward power from a remote radio frequency energy source.

  20. Outbursts and cavities in comets

    NASA Astrophysics Data System (ADS)

    Ipatov, Sergei

    Based on analysis of the images made during the first 13 minutes after the collision of the impact module of the Deep Impact (DI) spacecraft with Comet 9P/Tempel 1, Ipatov & A'Hearn [1] studied time variations of ejection of material after this impact. They showed that, besides the normal ejection, at time t_{e} after the DI collision between 8 s and 60 s there was a considerable additional ejection (a triggered outburst) of small (micron size) particles. It increased the mean velocities of observed small ejected particles (compared with the normal ejection). The outburst could be caused by excavation of a large cavity with dust and gas under pressure. The largest cavity excavated after the collision could be relatively deep because a considerable excess ejection lasted during about 50 s. Schultz et al. [2] concluded that the diameter d_{tc} of the DI transient crater was about 200 m. Some authors support smaller values of d_{tc}. The depth of the DI crater at t_{e}=8 s was estimated in [3] to be about 6 m for d_{tc}=200 m and 4 m for d_{tc}=100 m. The distance between the pre-impact surface of Comet 9P/Tempel 1 and the upper border of the largest excavated cavity equal to about 4-6 m, and sizes of particles inside the cavities of a few microns are in good agreement with the results obtained by Kossacki & Szutowicz [4]. In their models of the explosion of Comet 17P/Holmes, the initial sublimation front of the CO ice was located at a depth of 4 m, 10 m, or 20 m, and calculations were finished when the CO pressure exceeded the threshold value 10 kPa. It was shown that the pressure of CO vapor can rise to this value only when the nucleus is composed of very fine grains, a few microns in radius. The porous structure of comets provides enough space for sublimation. The projection of the velocity of the leading edge of the DI cloud (onto the plane perpendicular to the line of sight) was about 100-200 m/s and is typical for outburst particles ejected from comets

  1. Developments of VCSELs for printers and optical communications at Fuji Xerox

    NASA Astrophysics Data System (ADS)

    Kondo, Takashi; Takeda, Kazutaka; Otoma, Hiromi; Murakami, Akemi; Sakurai, Jun; Nakayama, Hideo; Gu, Xiaodong; Koyama, Fumio

    2016-03-01

    We review the characteristics of vertical-cavity surface-emitting lasers (VCSELs) for use in printers and optical communications. In 2003, we launched the world's first laser printer with a 780-nm single-mode 8×4 VCSEL array introduced to the light exposure system in order to meet the market demands for improving the image quality and speed for laser printers. The design of the VCSEL array enabled us to increase the pixel density and the printing speed by projecting 32 beams at a time to the photoconductor in the exposure process. High uniformity with less than 5% of variation has been achieved for both the optical output and the divergence angle. Currently, our high-end color printer is capable of producing the resolution of 2400 dpi (dots per inch) at the speed of 137 ppm (pages per minute). In the field of optical interconnections and networks, 850-nm VCSELs are needed as high-speed optical transmitters (>=10Gbps). In order to address communication traffic that will increase further as well as to reduce their power consumption to an even lower level, we assessed the lasing characteristics of 850-nm VCSELs with InGaAs strained quantum-well (QW) active layers by changing the ratio of Indium composition. As a result, we succeeded in reducing the power consumption per bit to 43 fJ/bit at 10-Gbps, which is much lower than that of commercial GaAs QW VCSELs. Also, we studied 850-nm transverse-coupled-cavity VCSELs, which enabled us to achieve a high 3dB modulation bandwidth (>23 GHz) and realize eye-openings at the large-signal modulation rate of 36 Gbps.

  2. Cavity quantum electrodynamics: coherence in context.

    PubMed

    Mabuchi, H; Doherty, A C

    2002-11-15

    Modern cavity quantum electrodynamics (cavity QED) illuminates the most fundamental aspects of coherence and decoherence in quantum mechanics. Experiments on atoms in cavities can be described by elementary models but reveal intriguing subtleties of the interplay of coherent dynamics with external couplings. Recent activity in this area has pioneered powerful new approaches to the study of quantum coherence and has fueled the growth of quantum information science. In years to come, the purview of cavity QED will continue to grow as researchers build on a rich infrastructure to attack some of the most pressing open questions in micro- and mesoscopic physics.

  3. Quantum teleportation with atoms trapped in cavities

    SciTech Connect

    Cho, Jaeyoon; Lee, Hai-Woong

    2004-09-01

    We propose a scheme to implement the quantum teleportation protocol with single atoms trapped in cavities. The scheme is based on the adiabatic passage and the polarization measurement. We show that it is possible to teleport the internal state of an atom trapped in a cavity to an atom trapped in another cavity with the success probability of 1/2 and the fidelity of 1. The scheme is resistant to a number of considerable imperfections such as the violation of the Lamb-Dicke condition, weak atom-cavity coupling, spontaneous emission, and detection inefficiency.

  4. Mechanical Properties of Ingot Nb Cavities

    SciTech Connect

    Ciovati, Gianluigi; Dhakal, Pashupati; Kneisel, Peter; Mammosser, John; Matalevich, Joseph; Rao Myneni, Ganapati

    2014-07-01

    This contribution presents the results of measurements of the resonant frequency and of strain along the contour of a single-cell cavity made of ingot Nb subjected to increasing uniform differential pressure, up to 6 atm. The data were used to infer mechanical properties of this material after cavity fabrication, by comparison with the results from simulation calculations done with ANSYS. The objective is to provide useful information about the mechanical properties of ingot Nb cavities which can be used in the design phase of SRF cavities intended to be built with this material.

  5. Cavity-locked ring down spectroscopy

    DOEpatents

    Zare, Richard N.; Paldus, Barbara A.; Harb, Charles C.; Spence, Thomas

    2000-01-01

    Distinct locking and sampling light beams are used in a cavity ring-down spectroscopy (CRDS) system to perform multiple ring-down measurements while the laser and ring-down cavity are continuously locked. The sampling and locking light beams have different frequencies, to ensure that the sampling and locking light are decoupled within the cavity. Preferably, the ring-down cavity is ring-shaped, the sampling light is s-polarized, and the locking light is p-polarized. Transmitted sampling light is used for ring-down measurements, while reflected locking light is used for locking in a Pound-Drever scheme.

  6. Design of the ILC Crab Cavity System

    SciTech Connect

    Adolphsen, C.; Beard, C.; Bellantoni, L.; Burt, G.; Carter, R.; Chase, B.; Church, M.; Dexter, A.; Dykes, M.; Edwards, H.; Goudket, P; Jenkins, R.; Jones, R.M.; Kalinin, A.; Khabiboulline, T.; Ko, K.; Latina, A.; Li, Z.; Ma, L.; McIntosh, P.; Ng, C.; /SLAC /Daresbury /Fermilab /Cockcroft Inst. Accel. Sci. Tech. /CERN

    2007-08-15

    The International Linear Collider (ILC) has a 14 mrad crossing angle in order to aid extraction of spent bunches. As a result of the bunch shape at the interaction point, this crossing angle at the collision causes a large luminosity loss which can be recovered by rotating the bunches prior to collision using a crab cavity. The ILC baseline crab cavity is a 9-cell superconducting dipole cavity operating at a frequency of 3.9 GHz. In this paper the design of the ILC crab cavity and its phase control system, as selected for the RDR in February 2007 is described in fuller detail.

  7. Self-mode-locked quantum-dot vertical-external-cavity surface-emitting laser.

    PubMed

    Gaafar, Mahmoud; Nakdali, Dalia Al; Möller, Christoph; Fedorova, Ksenia A; Wichmann, Matthias; Shakfa, Mohammad Khaled; Zhang, Fan; Rahimi-Iman, Arash; Rafailov, Edik U; Koch, Martin

    2014-08-01

    We present the first self-mode-locked optically pumped quantum-dot semiconductor disk laser. Our mode-locked device emits sub-picosecond pulses at a wavelength of 1040 nm and features a record peak power of 460 W at a repetition rate of 1.5 GHz. In this work, we also investigate the temperature dependence of the pulse duration as well as the time-bandwidth product for stable mode locking.

  8. Four-Wave Mixing and Optical Phase Conjugation in Vertical Cavity Surface Emitting Devices

    DTIC Science & Technology

    1997-01-01

    1990). Osinski , Marek and Jens Buus. "Linewidth Broadening Factor in Semiconductor Lasers- An Overview," IEEE Journal of Quantum Electronics QE-23(1): 9...above threshold. But as pointed out in the definitive document on the linewidth enhancement factor ( Osinski , 1987), for low carrier densities one can

  9. Recent Vertical External Cavity Surface Emitting Lasers (VECSELs) Developments for Sensor Applications (POSTPRINT)

    DTIC Science & Technology

    2013-02-01

    films, which are all nominally 5 μm thick. Our research has shown that sputter-deposited indium films are far smoother than evaporated films. RMS ...remain smaller, only a couple of microns in size. The surface can further be smoothed by a subsequent reflow process (down to ∼200 nm RMS roughness...SPIE 7325, pp. 73250L–1, (USA), 2009. [21] J. Hader, G. Hardesty , T.-L. Wang, M. J. Yarborough, Y. Kaneda, J. V. Moloney, B. Kunert, W. Stolz, and S

  10. Vertical cavity surface-emitting laser scanning cytometer for high speed analysis of cells

    SciTech Connect

    Gourley, P.L.; McDonald, A.E.; Gourley, M.F.

    1995-12-31

    We have constructed a new semiconductor laser device that may be useful in high speed characterization of cell morphology for diagnosis of disease. This laser device has critical advantages over conventional cell fluorescence detection methods since it provides intense, monochromatic, low-divergence fight signals that are emitted from lasing modes confined by a cell. Further, the device integrates biological structures with semiconductor materials at the wafer level to reduce device size and simplify cell preparation. In this paper we discuss operational characteristics of the prototype cytometer and present preliminary data for blood cells and dielectric spheres.

  11. Carbon nanotube mode-locked vertical external-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Seger, K.; Meiser, N.; Choi, S. Y.; Jung, B. H.; Yeom, D.-I.; Rotermund, F.; Okhotnikov, O.; Laurell, F.; Pasiskevicius, V.

    2014-03-01

    Mode-locking an optically pumped semiconductor disk laser has been demonstrated using low-loss saturable absorption containing a mixture of single-walled carbon nanotubes in PMM polymer. The modulator was fabricated by a simple spin-coating technique on fused silica substrate and was operating in transmission. Stable passive fundamental modelocking was obtained at a repetition rate of 613 MHz with a pulse length of 1.23 ps. The mode-locked semiconductor disk laser in a compact geometry delivered a maximum average output power of 136 mW at 1074 nm.

  12. 1.55 Vertical Cavity Surface Emitting Laser With Dielectric Mirrors

    DTIC Science & Technology

    2007-11-02

    was achieved with a polymer coating and a planarization coating etch-back to expose dielectric top. Then, the etch chemistry was switched to etch...densities respectively, q are the electronic charge, G is the generation rate of carriers and R is the recombination rate of carriers. Python Script...Modification CFDRC has developed python script for data flow management and control of coupled electromagnetic optics/semiconductor physics simulation

  13. Proton Irradiation Effects in Oxide-Confined Vertical Cavity Surface Emitting Laser (VCSEL) Diodes

    SciTech Connect

    Armendariz, M.G.; Barnes, C.E.; Choquette, K.D.; Guertin, S.; Hash, G.L.; Schwank, J.R.; Swift, G.M.

    1999-03-11

    Recent space experience has shown that the use of commercial optocouplers can be problematic in spacecraft, such as TOPEX/Poseidon, that must operate in significant radiation environments. Radiation--induced failures of these devices have been observed in space and have been further documented at similar radiation doses in the laboratory. The ubiquitous use of optocouplers in spacecraft systems for a variety of applications, such as electrical isolation, switching and power transfer, is indicative of the need for optocouplers that can withstand the space radiation environment. In addition, the distributed nature of their use implies that it is not particularly desirable to shield optocouplers for use in radiation environments. Thus, it will be important for the space community to have access to radiation hardened/tolerant optocouplers. For many microelectronic and photonic devices, it is difficult to achieve radiation hardness without sacrificing performance. However, in the case of optocouplers, one should be able to achieve both superior radiation hardness and performance for such characteristics as switching speed, current transfer ratio (CTR), minimum power usage and array power transfer, if standard light emitting diodes (LEDs), such as those in the commercial optocouplers mentioned above, are avoided, and VCSELs are employed as the emitter portion of the optocoupler. The physical configuration of VCSELs allows one to achieve parallel use of an array of devices and construct a multichannel optocoupler in the standard fashion with the emitters and detectors looking at each other. In addition, detectors similar in structure to the VCSELs can be fabricated which allows bidirectional functionality of the optocoupler. Recent discussions suggest that VCSELs will enjoy widespread applications in the telecommunications and data transfer fields.

  14. Ultra-Low Threshold Vertical-Cavity Surface-Emitting Lasers for USAF Applications

    DTIC Science & Technology

    2005-01-01

    initiated by Dr . John Loehr, with AFOSR Program Manager Dr . Alan Craig. In 2001, Dr . Thomas Nelson became the in-house project lead on this effort, with...AFOSR management transferred first to Dr . Kent Miller, and most recently to Dr . Gernot Pomrenke. This task was initiated in March 1996, and this report...NUMBER OF PAGES 108 Dr . Thomas R. Nelson 19b. TELEPHONE NUMBER (Include Area Code) (937) 255-1874 x3361 Standard Form 298 (Rev. 8

  15. Comparison of electromagnetic, thermal and mechanical calculations with rf test results in rf-dipole deflecting/crabbing cavities

    SciTech Connect

    Park, HyeKyoung; De Silva, Subashini U.; Delayen, Jean R.

    2013-12-01

    The current requirements of higher gradients and strict dimensional constraints in the emerging applications have required the designing of compact deflecting and crabbing rf structures. The superconducting rf-dipole cavity is one of the first novel compact designs with attractive properties such as higher gradients, higher shunt impedance and widely separated higher order modes. The recent tests performed on proof-of-principle designs of the rf-dipole geometry at 4.2 K and 2.0 K in the vertical test area at Jefferson Lab have proven the designs to achieve higher gradients with higher intrinsic quality factors and easily processed multipacting conditions. The cavity characteristics, such as pressure sensitivity and Lorentz force detuning, were studied using ANSYS before the fabrication. These characteristics were measured during the cavity test. The comparison between the simulation and the measurement provides insight how the simulation can be used for design and fabrication of future cavities.

  16. Comparison of coherently coupled multi-cavity and quantum dot embedded single cavity systems.

    PubMed

    Kocaman, Serdar; Sayan, Gönül Turhan

    2016-12-12

    Temporal group delays originating from the optical analogue to electromagnetically induced transparency (EIT) are compared in two systems. Similar transmission characteristics are observed between a coherently coupled high-Q multi-cavity array and a single quantum dot (QD) embedded cavity in the weak coupling regime. However, theoretically generated group delay values for the multi-cavity case are around two times higher. Both configurations allow direct scalability for chip-scale optical pulse trapping and coupled-cavity quantum electrodynamics (QED).

  17. Method and Apparatus for Linewidth Reduction in Distributed Feedback or Distributed Bragg Reflector Semiconductor Lasers using Vertical Emission

    NASA Technical Reports Server (NTRS)

    Cook, Anthony L. (Inventor); Hendricks, Herbert D. (Inventor)

    1998-01-01

    The linewidth of a distributed feedback semiconductor laser or a distributed Bragg reflector laser having one or more second order gratings is reduced by using an external cavity to couple the vertical emission back into the laser. This method and device prevent disturbance of the main laser beam. provide unobstructed access to laser emission for the formation of the external cavity. and do not require a very narrow heat sink. Any distributed Bragg reflector semiconductor laser or distributed feedback semiconductor laser that can produce a vertical emission through the epitaxial material and through a window in the top metallization can be used. The external cavity can be formed with an optical fiber or with a lens and a mirror of grating.

  18. Mini-cavity-dumped laser

    NASA Technical Reports Server (NTRS)

    Reed, E.

    1981-01-01

    Lasers for use in high precision satellite ranging systems consist typically of an oscillator followed by several amplifier stages. While the shortest optical pulses are achieved by using a mode locked oscillator, such an oscillator is incompatible with the compact design needed in future, highly mobile systems. The laser oscillator achieves pulse lengths approaching those obtainable by mode locking, but in a much more compact and stable design. The oscillator uses two LiNbO3 Pockels cells inside the resonator. One Q-switches the oscillator, and the other is used in a pulse slicing scheme to cavity dump a portion of the circulating optical energy. The length of the optical output pulse measured at 425 + or - 50 picoseconds.

  19. Slow plasmons in grating cavities

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  20. The Heliosphere as Resonant Cavity

    NASA Technical Reports Server (NTRS)

    Bames, Aaron

    1999-01-01

    If a disturbance in the supersonic solar wind reaches the heliospheric shock, a number of events ensue. First, the shock itself responds with inward or outward motion. Secondly, the disturbance propagates outward through the heliosheath as a sound or magnetoacoustic wave; eventually it reaches the heliopause and is (partially) reflected back toward the termination shock. The reflected wave can return to the shock, affecting the shock's motion, and be reflected yet again. The repetition of these processes can produce a 'ringing' in the heliosheath. This suggests that it may be useful to regard the heliosheath as a resonant acoustic cavity with inner and outer boundaries at the termination shock and heliopause, respectively. To evaluate this concept we have developed a simple model of small-amplitude resonant oscillations in an outwardly flowing gas, with appropriate boundary conditions (shock on the interior, tangential discontinuity on the exterior boundary). The fundamental mode of oscillation has a period of order T approx. 2D/C, where C is the speed of sound in the heliosheath and D is the distance between the two boundaries. Typical numerical models of the heliosphere give C approx. 200-500 km/s and D approx. 20 - 100 AU, giving T approx. 0.5 - 2.5 years. Hence we suggest that motions of the heliosheath and termination shock will occur with time scales of the order of a year, and are the consequence of the resonant nature of the heliospheric cavity rather than the history of variation at the Sun and/or in the solar wind. In particular, we suggest that the motion of the termination shock may be unrelated to solar variations over the time scale of the sunspot cycle.

  1. Geophysical observations at cavity collapse

    NASA Astrophysics Data System (ADS)

    Jousset, Philippe; Bazargan-Sabet, Behrooz; Lebert, François; Bernardie, Séverine; Gourry, Jean-Christophe

    2010-05-01

    In Lorraine region (France) salt layers at about 200 meters depth are exploited by Solvay using solution mining methodology which consists in extracting the salt by dissolution, collapsing the cavern overburden during the exploitation phase and finally reclaiming the landscape by creating a water area. In this process, one of the main challenges for the exploiting company is to control the initial 120-m diameter collapse so as to minimize possible damages. In order to detect potential precursors and understand processes associated with such collapses, a wide series of monitoring techniques including micro seismics, broad-band seismology, hydro-acoustic, electromagnetism, gas probing, automatic leveling, continuous GPS, continuous gravity and borehole extensometry was set-up in the frame of an in-situ study carried out by the "Research Group for the Impact and Safety of Underground Works" (GISOS, France). Equipments were set-up well before the final collapse, giving a unique opportunity to analyze a great deal of information prior to and during the collapse process which has been successfully achieved on February the 13th, 2009 by controlling the cavity internal pressure. In this work, we present the results of data recorded by a network of 3 broadband seismometers, 2 accelerometers, 2 tilt-meters and a continuously gravity meter. We relate the variations of the brine pumping rate with the evolutions of the induced geophysical signals and finally we propose a first mechanical model for describing the controlled collapse. Beyond the studied case, extrapolation of the results obtained might contribute to the understanding of uncontrolled cavity collapses, such as pit-craters or calderas at volcanoes.

  2. Vertical motion simulator familiarization guide

    NASA Technical Reports Server (NTRS)

    Danek, George L.

    1993-01-01

    The Vertical Motion Simulator Familiarization Guide provides a synoptic description of the Vertical Motion Simulator (VMS) and descriptions of the various simulation components and systems. The intended audience is the community of scientists and engineers who employ the VMS for research and development. The concept of a research simulator system is introduced and the building block nature of the VMS is emphasized. Individual sections describe all the hardware elements in terms of general properties and capabilities. Also included are an example of a typical VMS simulation which graphically illustrates the composition of the system and shows the signal flow among the elements and a glossary of specialized terms, abbreviations, and acronyms.

  3. Measurements of vertical bar Vcb vertical bar and vertical bar Vub vertical bar at BaBar

    SciTech Connect

    Rotondo, M.

    2005-10-12

    We report results from the BABAR Collaboration on the semileptonic B decays, highlighting the measurements of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix elements Vub and Vcb. We describe the techniques used to obtain the matrix element |Vcb| using the measurement of the inclusive B {yields} Xclv process and a large sample of exclusive B {yields} D*lv decays. The vertical bar Vub vertical bar matrix elements has been measured studying different kinematic variables of the B {yields} Xulv process, and also with the exclusive reconstruction of B {yields} {pi}({rho})lv decays.

  4. Survival analysis of a critical resource for cavity-nesting communities: patterns of tree cavity longevity.

    PubMed

    Edworthy, Amanda B; Wiebe, Karen L; Martin, Kathy

    2012-09-01

    Tree cavities are a vital multi-annual resource used by cavity-nesting birds and mammals for nesting and shelter. The abundance of this resource will be influenced by the rates at which cavities are created and destroyed. We applied the demographic concepts of survival and longevity to populations of tree holes to investigate rates of loss for cavities in three tree species, as well as how characteristics of nest trees, habitat type, and species of excavator affected the persistence of tree cavities in trembling aspen, Populus tremuloides (95% of cavities were in aspen trees), in interior British Columbia, Canada. By modeling survival of 1635 nesting cavities in aspen over a time span of 16 years, we found that the decay stage of the nest tree was the most important factor determining cavity longevity. Cavities in trees with advanced decay had a relatively short median longevity of 7 years (95% CI 6-9 years), whereas those in living trees had a median longevity of more than 15 years. We found that cavity longevity was greater in continuous forest than in aspen grove habitat. Interestingly, cavities formed by weak excavators survived as long as those created by Northern Flickers (Colaptes auratus), despite occurring in more decayed tree stems. Thus, weak excavators may be selecting for characteristics that make a tree persistent, such as a broken top. Our results indicate that retention of cavities in large, live aspen trees is necessary to conserve persistent cavities, and that cavity longevity will have a large effect on the structure and function of cavity-using vertebrate communities.

  5. Hydrogen masers with cavity frequency switching servos

    NASA Technical Reports Server (NTRS)

    Peters, Harry E.; Owings, H. B.; Koppang, Paul A.

    1990-01-01

    The stability of the free-running hydrogen maser is limited by pulling of the unperturbed hydrogen transition frequency due to instability of the cavity resonance frequency. While automatic spin-exchange tuning is in principle the more basic and accurate method, the required beam intensity switching and the long servo time constant result in reduced stability for measuring intervals up to 10(exp 6) seconds. More importantly, the spin-exchange tuning method requires a second stable frequency source as a reference, ideally a second hydrogen maser, to get the best results. The cavity frequency switching servo, on the other hand, has very little effect on the maser short term stability, and is fast enough to correct for cavity drift while maintaining the cavity at the spin-exchange tuned offset required to minimize instability due to beam intensity fluctuations. Not only does the cavity frequency switching servo not require a second stable frequency source, but the frequency reference is the atomic hydrogen radiated beam signal, so that no extra RF connections need be made to the cavity, and externally generated signals that would perturb the hydrogen atom need not be transmitted through the cavity. The operation of the cavity frequency switching stabilization method is discussed and the transient response of the servo and certain other aspects of the technique that have potential for achieving improved basic accuracy are illustrated.

  6. Geometric Model of a Coronal Cavity

    NASA Technical Reports Server (NTRS)

    Kucera, Therese A.; Gibson, S. E.; Ratawicki, D.; Dove, J.; deToma, G.; Hao, J.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Reeves, K. K.; Schmidt, D. J.; Sterling, A. C.; Tripathi, D. K.; Williams, D. R.; Zhang, M.

    2010-01-01

    We observed a coronal cavity from August 8-18 2007 during a multi-instrument observing campaign organized under the auspices of the International Heliophysical Year (IHY). Here we present initial efforts to model the cavity with a geometrical streamer-cavity model. The model is based the white-light streamer mode] of Gibson et a]. (2003 ), which has been enhanced by the addition of a cavity and the capability to model EUV and X-ray emission. The cavity is modeled with an elliptical cross-section and Gaussian fall-off in length and width inside the streamer. Density and temperature can be varied in the streamer and cavity and constrained via comparison with data. Although this model is purely morphological, it allows for three-dimensional, multi-temperature analysis and characterization of the data, which can then provide constraints for future physical modeling. Initial comparisons to STEREO/EUVI images of the cavity and streamer show that the model can provide a good fit to the data. This work is part of the effort of the International Space Science Institute International Team on Prominence Cavities

  7. Compact microwave cavity for hydrogen atomic clock

    NASA Technical Reports Server (NTRS)

    Zhang, Dejun; Zhang, Yan; Fu, Yigen; Zhang, Yanjun

    1992-01-01

    A summary is presented that introduces the compact microwave cavity used in the hydrogen atomic clock. Special emphasis is placed on derivation of theoretical calculating equations of main parameters of the microwave cavity. A brief description is given of several methods for discriminating the oscillating modes. Experimental data and respective calculated values are also presented.

  8. The ADMX Microwave Cavity: Present and future

    NASA Astrophysics Data System (ADS)

    Woollett, Nathan; ADMX Collaboration

    2017-01-01

    The Axion Dark Matter eXperiment (ADMX), a direct-detection axion search, uses a tunable resonant cavity to enhance axion to photon conversion rates to a detectable level when the cavity resonance matches the mass of the axion. It has successfully taken data in the 460 - 890 MHz frequency range and is now probing a similar range with much higher sensitivity. However the axion mass is unknown and may be at higher frequencies than the currently operating system. In anticipation of future runs with an increased mass range, ADMX is conducting extensive research and development of microwave cavities. These developments include photonic band-gap cavities, multi-vane cavities, partitioned cavities, in-phase coupled cavities, and superconducting hybrid cavities. Many of these projects are in different stages between simulations and testing of physical prototypes. The status and current objectives of these projects will be presented. Supported by DOE Grants DE-SC0010280, DE-FG02-96ER40956, DE-AC52-07NA27344, DE-AC03-76SF00098, the Heising-Simons Foundation and the LLNL, FNAL and PNNL LDRD program.

  9. Fast tuning of superconducting microwave cavities

    SciTech Connect

    Sandberg, M.; Wilson, C. M.; Persson, F.; Johansson, G.; Shumeiko, V.; Bauch, T.; Duty, T.; Delsing, P.

    2008-11-07

    Photons are fundamental excitations of electromagnetic fields and can be captured in cavities. For a given cavity with a certain size, the fundamental mode has a fixed frequency f which gives the photons a specific 'color'. The cavity also has a typical lifetime {tau}, which results in a finite linewidth {delta}f. If the size of the cavity is changed fast compared to {tau}, and so that the frequency change {delta}f>>{delta}f, then it is possible to change the 'color' of the captured photons. Here we demonstrate superconducting microwave cavities, with tunable effective lengths. The tuning is obtained by varying a Josephson inductance at one end of the cavity. We show data on four different samples and demonstrate tuning by several hundred linewidths in a time {delta}t<<{tau}. Working in the few photon limit, we show that photons stored in the cavity at one frequency will leak out from the cavity with the new frequency after the detuning. The characteristics of the measured devices make them suitable for different applications such as dynamic coupling of qubits and parametric amplification.

  10. Large grain cavities from pure niobium ingot

    DOEpatents

    Myneni, Ganapati Rao [Yorktown, VA; Kneisel, Peter [Williamsburg, VA; Cameiro, Tadeu [McMurray, PA

    2012-03-06

    Niobium cavities are fabricated by the drawing and ironing of as cast niobium ingot slices rather than from cold rolled niobium sheet. This method results in the production of niobium cavities having a minimum of grain boundaries at a significantly reduced cost as compared to the production of such structures from cold rolled sheet.

  11. Folded cavity design for a ruby resonator

    NASA Technical Reports Server (NTRS)

    Arunkumar, K. A.; Trolinger, James D.

    1988-01-01

    A folded cavity laser resonator operating in the TEM(00) mode has been built and tested. The new oscillator configuration leads to an increase in efficiency and to better line narrowing due to the increased number of passes through the laser rod and tuning elements, respectively. The modification is shown to lead to cavity ruggedization.

  12. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  13. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  14. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  15. 21 CFR 872.3260 - Cavity varnish.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cavity varnish. 872.3260 Section 872.3260 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... device that consists of a compound intended to coat a prepared cavity of a tooth before insertion...

  16. Developing of superconducting niobium cavities for accelerators

    NASA Astrophysics Data System (ADS)

    Pobol, I. L.; Yurevich, S. V.

    2015-11-01

    The results of a study of structure and mechanical properties of welding joints, superconducting characteristics of the material after joining of welded components of superconducting radio frequency cavities are presented. The paper also describes the results of testing of the RF 1.3 GHz single-cell niobium cavity manufactured in the PTI NAS Belarus.

  17. Tunable Microwave Cavity For Ion Source

    NASA Technical Reports Server (NTRS)

    Nakanishi, Shigeo; Calco, Frank S.; Scarpelli, August R.

    1988-01-01

    Movable probe and tuning wall adjusted to obtain resonance at microwave frequency used to generate plasma in cell at one end of microwave cavity. Electroless discharge without disadvantages of dc-cathode-discharge and RF-induction methods. To achieve precise positioning, coaxial probe extends into microwave cavity through tube.

  18. Performance Of Superconducting-Cavity Maser

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Wang, Rabi T.

    1991-01-01

    Report describes experiments on operation of superconducting-cavity maser - all-cryogenic oscillator. Operates with degree of stability, at short measuring times, superior to that achievable by any other means. All components designed for cryogenic operation and stabilizing cavity very rigid, consisting of sapphire filling coated with lead.

  19. Integration of Geomatic Techniques for the Urban Cavity Survey

    NASA Astrophysics Data System (ADS)

    Deidda, M.; Sanna, G.

    2013-07-01

    Cagliari, county seat of Sardinia Region (Italy), situated in the southern part of the island, is characterized by a subsoil full of cavities. The excavations in fact, which lasted more than 4000 years, had a great development due also to the special geological characteristics of the city subsoil. The underground voids, which the city is rich in, belong to different classes such as hydraulic structures (aqueducts, cisterns, wells, etc.), settlement works (tunnels, bomb shelters, tombs etc.) and various works (quarries, natural caves, etc.). This paper describes the phases of the survey of a large cavity below a high-traffic square near the Faculty of Engineering in the city of Cagliari, where the research team works. The cave, which is part of a larger complex, is important because it was used in the thirteenth century (known as the Pisan age) as a stone quarry. There are traces of this activity that have to be protected. Moreover, during the last forty years the continuous crossover of vehicles cracked the roof of the cave compromising the stability of the entire area. Consequently a plan was developed to make the whole cavity safe and usable for visits. The study of the safety of the cave has involved different professionals among which geologists, engineers, constructors. The goal of the University of Cagliari geomatic team was to solve two problems: to obtain geometrical information about the void and correctly place the cave in the context of existing maps. The survey and the products, useful for the investigation of the technicians involved, had to comply with tolerances of 3 cm in the horizontal and 5 cm in the vertical component. The approach chosen for this purpose was to integrate different geomatic techniques. The cave was surveyed using a laser scanner (Faro Photon 80) in order to obtain a 3D model of the cave from which all the geometrical information was derived, while both classic topography and GPS techniques were used to include the cave in the

  20. Laboratory scale simulation of spontaneous vertical convective vortex generation

    NASA Astrophysics Data System (ADS)

    Sharifulin, Albert; Poludnitsin, Anatoly

    2009-11-01

    The new mechanism of spontaneous vertical vortex generation in stratified fluid is under consideration. This phenomenon was discovered in the framework of experimental attempt [1] to proof the hypothesis of universal character of bifurcation curve formulated in [2]. The experiment with slow cubic cell inclination from bottom heating position was performed. The theoretically predicted curve form had been proved; but in the transition process from abnormal convection flow to normal one during bifurcation curve crossing the unexpected spontaneous vertical convective vortex motion has been discovered. Possibility of spontaneous vertical convective vortex generation application to atmospheric behavior explanation and to Earth's mantle one is discussed. New non-local hurricane generation mechanism and observed oceanic volcano archipelago's form explanation attempt are formulated and speculated. [1] AN Sharifulin, AN Poludnitsin, AS Kravchuk Laboratory Scale Simulation of Nonlocal Generation of a Tropical Cyclone. Journal of Experimental and Theoretical Physics, 2008, V.107, No.6, p.1090. [2] AI Nikitin, AN Sharifulin, Concerning the bifurcations of steady-state thermal convection regimes in a closed cavity due to the Whitney folding-type singularity. Heat Transfer -- Soviet Research, v.21, no.2, 1989, p.213.

  1. Subglacial Silicic Eruptions: Wet Cavities and Moist Cavities.

    NASA Astrophysics Data System (ADS)

    Stevenson, J. A.; McGarvie, D. W.; Gilbert, J. S.; Smellie, J. L.

    2007-05-01

    ice produces water, however in the Kerlingarfjöll eruption (which is thought to have been relatively brief and the vesicular magma is likely to have contained less heat per unit volume) the volumes were small and the subglacial cavity could be appropriately described as 'moist'. The Prestahnúkur eruption occurred in a 'wet' cavity but 'lacustrine' conditions were never developed and the ice was always close to the edifice. Poor sorting and structure in the subglacial deposits are due to a lack of time and space for sorting to occur. In contrast to more mafic eruptions, which are characterised by very strong meltwater-ice interactions, the main influence of the ice during subglacial rhyolite eruptions is reflected in the confinement of eruptive products.

  2. Mechanical failure of cavities in poroelastic media

    SciTech Connect

    Ozkan, G.; Ortoleva, P.

    1998-12-31

    The stress-induced failure of cavities in poroelastic media is investigated using an analytical solution of the elastic matrix inclusion problem of Eshelby and a rock failure criterion. The elastic properties of the porous matrix surrounding the cavity are modeled using a self-consistent version of the theory of Berryman while the cavity collapse criterion is based on a failure condition calibrated as a function of matrix mineralogy, grain size and porosity. The influence of the latter textural variables as well as pore fluid pressure and cavity shape and orientation relative to the far-field stress are evaluated. The region of failure on the cavity surface is identified. These results are applied to the prediction of vug stability in a sedimentary basin in the context of vuggy reservoir exploration and production.

  3. Air flow in a collapsing cavity

    NASA Astrophysics Data System (ADS)

    Peters, Ivo R.; Gekle, Stephan; Lohse, Detlef; van der Meer, Devaraj

    2013-03-01

    We experimentally study the airflow in a collapsing cavity created by the impact of a circular disc on a water surface. We measure the air velocity in the collapsing neck in two ways: Directly, by means of employing particle image velocimetry of smoke injected into the cavity and indirectly, by determining the time rate of change of the volume of the cavity at pinch-off and deducing the air flow in the neck under the assumption that the air is incompressible. We compare our experiments to boundary integral simulations and show that close to the moment of pinch-off, compressibility of the air starts to play a crucial role in the behavior of the cavity. Finally, we measure how the air flow rate at pinch-off depends on the Froude number and explain the observed dependence using a theoretical model of the cavity collapse.

  4. Performance of 3-cell Seamless Niobium cavities

    SciTech Connect

    Kneisel, Peter K.; Ciovati, Gianluigi; Jelezov, I.; Singer, W.; Singer, X.

    2009-11-01

    In the last several months we have surface treated and cryogenically tested three TESLA-type 3-cell cavities, which had been manufactured at DESY as seamless assemblies by hydroforming. The cavities were completed at JLab with beam tube/flange assemblies. All three cavities performed very well after they had been post-purified with titanium at 1250C for 3 hrs. The cavities, two of which consisted of an end cell and 2 center cells and one was a center cell assembly, achieved gradients of Eacc = 32 MV/m, 34 MV/m and 35 MV/m without quenches. The performance was limited by the appearance of the “Q-drop” in the absence of field emission. This contribution reports about the various measurements undertaken with these cavities.

  5. Cavity cooling below the recoil limit.

    PubMed

    Wolke, Matthias; Klinner, Julian; Keßler, Hans; Hemmerich, Andreas

    2012-07-06

    Conventional laser cooling relies on repeated electronic excitations by near-resonant light, which constrains its area of application to a selected number of atomic species prepared at moderate particle densities. Optical cavities with sufficiently large Purcell factors allow for laser cooling schemes, avoiding these limitations. Here, we report on an atom-cavity system, combining a Purcell factor above 40 with a cavity bandwidth below the recoil frequency associated with the kinetic energy transfer in a single photon scattering event. This lets us access a yet-unexplored regime of atom-cavity interactions, in which the atomic motion can be manipulated by targeted dissipation with sub-recoil resolution. We demonstrate cavity-induced heating of a Bose-Einstein condensate and subsequent cooling at particle densities and temperatures incompatible with conventional laser cooling.

  6. Automated Hydroforming of Seamless Superconducting RF Cavity

    SciTech Connect

    Nagata, Tomohiko; Shinozawa, Seiichi; Abe, Noriyuki; Nagakubo, Junki; Murakami, Hirohiko; Tajima, Tsuyoshi; Inoue, Hitoshi; Yamanaka, Masashi; Ueno, Kenji

    2012-07-31

    We are studying the possibility of automated hydroforming process for seamless superconducting RF cavities. Preliminary hydroforming tests of three-cell cavities from seamless tubes made of C1020 copper have been performed. The key point of an automated forming is to monitor and strictly control some parameters such as operation time, internal pressure and material displacements. Especially, it is necessary for our studies to be able to control axial and radial deformation independently. We plan to perform the forming in two stages to increase the reliability of successful forming. In the first stage hydroforming by using intermediate constraint dies, three-cell cavities were successfully formed in less than 1 minute. In parallel, we did elongation tests on cavity-quality niobium and confirmed that it is possible to achieve an elongation of >64% in 2 stages that is required for our forming of 1.3 GHz cavities.

  7. Fast thermometry for superconducting rf cavity testing

    SciTech Connect

    Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N.; Kotelnikov, Sergey; Makulski, Andrzej; Nehring, Roger; Pischalnikov, Yuriy; /Fermilab

    2007-06-01

    Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity.

  8. Casimir forces of metallic microstructures into cavities

    NASA Astrophysics Data System (ADS)

    Kenanakis, George; Soukoulis, Costas M.; Economou, Eleftherios N.

    2015-08-01

    A theoretical estimate of the Casimir force of a metallic structure embedded into a cubic cavity is proposed. We demonstrate that by calculating the eigenmodes of the system we can determine the Casimir force, which can be either attractive or repulsive, by simply changing the geometry of the structures relative to the walls of the cavity. In this analysis, several cases of structures are taken into account, from rectangular slabs to chiral "omega" particles, and the predicted data are consistent with recent literature. We demonstrate that the sidewalls of the studied cavity contribute decisively to the repulsive Casimir force between the system and the nearby top surface of the cavity. Finally, we provide evidence that the medium embedded into the studied cavity (and especially its permittivity) can change the intensity of the Casimir force, while its repulsive nature, once established (owing to favorable geometrical features), remains quite robust.

  9. Interaction of copper with cavities in silicon

    NASA Astrophysics Data System (ADS)

    Myers, S. M.; Follstaedt, D. M.

    1996-02-01

    Copper in Si was shown to be strongly bound at cavities formed by He ion implantation and annealing. Evolution of this system during heating was observed by Rutherford backscattering spectrometry and transmission electron microscopy. Results were mathematically modeled to characterize quantitatively the binding of Cu in the cavities and, for comparison, in precipitates of the equilibrium silicide, η-Cu3Si. Binding of Cu to cavities occurred by chemisorption on the walls, and the binding energy was determined to be 2.2±0.2 eV relative to solution in Si. The heat of solution from the silicide was found to be 1.7 eV, consistent with the published phase diagram. These findings suggest the use of cavities for metal-impurity gettering in Si devices. Hydrogen in solution in equilibrium with external H2 gas displaced Cu atoms from cavity walls, a mechanistically illuminating effect that is also of practical concern for gettering applications.

  10. Optomechanical photon shuttling between photonic cavities.

    PubMed

    Li, Huan; Li, Mo

    2014-11-01

    Mechanical motion of photonic devices driven by optical forces provides a profound means of coupling between optical fields. The current focus of these optomechanical effects has been on cavity optomechanics systems in which co-localized optical and mechanical modes interact strongly to enable wave mixing between photons and phonons, and backaction cooling of mechanical modes. Alternatively, extended mechanical modes can also induce strong non-local effects on propagating optical fields or multiple localized optical modes at distances. Here, we demonstrate a multicavity optomechanical device in which torsional optomechanical motion can shuttle photons between two photonic crystal nanocavities. The resonance frequencies of the two cavities, one on each side of this 'photon see-saw', are modulated antisymmetrically by the device's rotation. Pumping photons into one cavity excites optomechanical self-oscillation, which strongly modulates the inter-cavity coupling and shuttles photons to the other empty cavity during every oscillation cycle in a well-regulated fashion.

  11. Microphonics Measurements in SRF Cavities for RIA

    SciTech Connect

    Kelly, M.P.; Fuerst, Joel; Kedzie, M.; Sharamentov, S.I.; Shepard, Kenneth; Delayen, Jean

    2003-05-01

    Phase stabilization of the RIA drift tube cavities in the presence of microphonics will be a key issue for RIA. Due to the relatively low beam currents (lte 0.5 pmA) required for the RIA driver, microphonics will impact the rf power required to control the cavity fields. Microphonics measurements on the ANL Beta=0.4 single spoke cavity and on the ANL Beta=0.4 two-cell spoke cavity have been performed many at high fields and using a new "cavity resonance monitor" device developed in collaboration with JLAB. Tests on a cold two-cell spoke are the first ever on a multi-cell spoke geometry. The design is essentially a production model with an integral stainless steel housing to hold the liquid helium bath.

  12. Cavity solitons and localized patterns in a finite-size optical cavity

    NASA Astrophysics Data System (ADS)

    Kozyreff, G.; Gelens, L.

    2011-08-01

    In appropriate ranges of parameters, laser-driven nonlinear optical cavities can support a wide variety of optical patterns, which could be used to carry information. The intensity peaks appearing in these patterns are called cavity solitons and are individually addressable. Using the Lugiato-Lefever equation to model a perfectly homogeneous cavity, we show that cavity solitons can only be located at discrete points and at a minimal distance from the edges. Other localized states which are attached to the edges are identified. By interpreting these patterns in an information coding frame, the information capacity of this dynamical system is evaluated. The results are explained analytically in terms of the the tail characteristics of the cavity solitons. Finally, the influence of boundaries and of cavity imperfections on cavity solitons are compared.

  13. Physics and the Vertical Jump

    ERIC Educational Resources Information Center

    Offenbacher, Elmer L.

    1970-01-01

    The physics of vertical jumping is described as an interesting illustration for motivating students in a general physics course to master the kinematics and dynamics of one dimensional motion. The author suggests that mastery of the physical principles of the jump may promote understanding of certain biological phenomena, aspects of physical…

  14. Vertical Instability at IPNS RCS.

    SciTech Connect

    Wang, S.; Brumwell, F. R.; Dooling, J. C.; Harkay, K. C.; Kustom, R.; McMichael, G. E.; Middendorf, M. E.; Nassiri, A.; Accelerator Systems Division

    2008-01-01

    The rapid cycling synchrotron (RCS) of the intense pulsed neutron source (IPNS) at ANL accelerates > 3.0 times 10{sup 12} protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During the acceleration cycle, the rf frequency varies from 2.21 MHz to 5.14 MHz. Presently, the beam current is limited by a vertical instability. By analyzing turn-by-turn beam position monitor (BPM) data, large- amplitude mode 0 and mode 1 vertical beam centroid oscillations were observed in the later part of the acceleration cycle. The oscillations start in the tail of the bunch, build up, and remain localized in the tail half of the bunch. This vertical instability was compared with a head-tail instability that was intentionally induced in the RCS by adjusting the trim sextupoles. It appears that our vertical instability is not a classical head-tail instability [1]. More data analysis and experiments were performed to characterize the instability.

  15. Vertical reactor coolant pump instabilities

    NASA Technical Reports Server (NTRS)

    Jones, R. M.

    1985-01-01

    The investigation conducted at the Tennessee Valley Authority's Sequoyah Nuclear Power Plant to determine and correct increasing vibrations in the vertical reactor coolant pumps is described. Diagnostic procedures to determine the vibration causes and evaluate the corrective measures taken are also described.

  16. The possibility of vertical transmission of human papillomavirus through maternal milk.

    PubMed

    Yoshida, K; Furumoto, H; Abe, A; Kato, T; Nishimura, M; Kuwahara, A; Maeda, K; Matsuzaki, T; Irahara, M

    2011-08-01

    Human papillomavirus (HPV) DNA has been detected in the oral cavity of infants and breast cancer tissue, suggesting its vertical transmission through maternal milk. We determined whether HPV is detected in maternal milk and is vertically transmitted by breast-feeding. Informed consent was obtained, and maternal milk samples (n=80) were analysed for high-risk HPV DNA. In 43 women, this DNA was measured in the uterine cervix. In women with positive samples, this DNA was measured in the oral cavities of their children. The domain including HPV E6 and E7 was amplified by polymerase chain reaction using consensus primers, and HPV serotype determined by electrophoresis after restriction enzyme digestion. High-risk HPV-16 was detected in two of 80 samples (2.5%), and in these two cases, high-risk HPV was not detected in the uterine cervix or oral cavity of the child. It was concluded that the infection of HPV in maternal milk is rare (2/80); vertical transmission through maternal milk was not detected in this study (0/80). HPV infection through maternal milk may occur, but its likelihood is low.

  17. Vertical Sextants give Good Sights

    NASA Astrophysics Data System (ADS)

    Dixon, Mark

    Many texts stress the need for marine sextants to be held precisely vertical at the instant that the altitude of a heavenly body is measured. Several authors lay particular emphasis on the technique of the instrument in a small arc about the horizontal axis to obtain a good sight. Nobody, to the author's knowledge, however, has attempted to quantify the errors involved, so as to compare them with other errors inherent in determining celestial position lines. This paper sets out to address these issues and to pose the question: what level of accuracy of vertical alignment can reasonably be expected during marine sextant work at sea ?When a heavenly body is brought to tangency with the visible horizon it is particularly important to ensure that the sextant is held in a truly vertical position. To this end the instrument is rocked gently about the horizontal so that the image of the body describes a small arc in the observer's field of vision. As Bruce Bauer points out, tangency with the horizon must be achieved during the process of rocking and not a second or so after rocking has been discontinued. The altitude is recorded for the instant that the body kisses the visible horizon at the lowest point of the rocking arc, as in Fig. 2. The only other visual clue as to whether the sextant is vertical is provided by the right angle made by the vertical edge of the horizon glass mirror with the horizon. There may also be some input from the observer's sense of balance and his hand orientation.

  18. Shrinkage of dental composite in simulated cavity measured with digital image correlation.

    PubMed

    Li, Jianying; Thakur, Preetanjali; Fok, Alex S L

    2014-07-21

    Polymerization shrinkage of dental resin composites can lead to restoration debonding or cracked tooth tissues in composite-restored teeth. In order to understand where and how shrinkage strain and stress develop in such restored teeth, Digital Image Correlation (DIC) was used to provide a comprehensive view of the displacement and strain distributions within model restorations that had undergone polymerization shrinkage. Specimens with model cavities were made of cylindrical glass rods with both diameter and length being 10 mm. The dimensions of the mesial-occlusal-distal (MOD) cavity prepared in each specimen measured 3 mm and 2 mm in width and depth, respectively. After filling the cavity with resin composite, the surface under observation was sprayed with first a thin layer of white paint and then fine black charcoal powder to create high-contrast speckles. Pictures of that surface were then taken before curing and 5 min after. Finally, the two pictures were correlated using DIC software to calculate the displacement and strain distributions. The resin composite shrunk vertically towards the bottom of the cavity, with the top center portion of the restoration having the largest downward displacement. At the same time, it shrunk horizontally towards its vertical midline. Shrinkage of the composite stretched the material in the vicinity of the "tooth-restoration" interface, resulting in cuspal deflections and high tensile strains around the restoration. Material close to the cavity walls or floor had direct strains mostly in the directions perpendicular to the interfaces. Summation of the two direct strain components showed a relatively uniform distribution around the restoration and its magnitude equaled approximately to the volumetric shrinkage strain of the material.

  19. Verticality perception during off-vertical axis rotation.

    PubMed

    Vingerhoets, R A A; Van Gisbergen, J A M; Medendorp, W P

    2007-05-01

    During prolonged rotation about a tilted yaw axis, often referred to as off-vertical axis rotation (OVAR), a percept of being translated along a conical path slowly emerges as the sense of rotation subsides. Recently, we found that these perceptual changes are consistent with a canal-otolith interaction model that attributes the illusory translation percept to improper interpretation of the ambiguous otolith signals. The model further predicts that the illusory translation percept must be accompanied by slowly worsening tilt underestimates. Here, we tested this prediction in six subjects by measuring the time course of the subjective visual vertical (SVV) during OVAR stimulation at three different tilt-rotation speed combinations, in complete darkness. Throughout the 2-min run, at each left-ear-down and right-ear-down position, the subject indicated whether a briefly flashed line deviated clockwise or counterclockwise from vertical to determine the SVV with an adaptive staircase procedure. Typically, SVV errors indicating tilt underestimation were already present at rotation onset and then increased exponentially to an asymptotic value, reached at about 60 s after rotation onset. The initial error in the SVV was highly correlated to the response error in a static tilt control experiment. The subsequent increase in error depended on both rotation speed and OVAR tilt angle, in a manner predicted by the canal-otolith interaction model. We conclude that verticality misjudgments during OVAR reflect a dynamic component linked to canal-otolith interaction, superimposed on a tilt-related component that is also expressed under stationary conditions.

  20. Resonant-cavity antenna for plasma heating

    SciTech Connect

    Perkins, F.W. Jr.; Chiu, S.C.; Rawls, J.M.

    1987-04-28

    This patent describes a magnetic confinement plasma device having a plasma. The plasma is immersed in a strong magnetic field and confined within an evacuated plasma chamber. A wave launcher for launching electromagnetic waves in the range of frequencies of 10 MHz to 200 MHz energizes and thereby heats the plasma. The wave launcher is spaced-apart from the plasma. The wave launcher comprises: a resonant cavity, including resonant chamber walls for containing electromagnetic fields; connection means connecting the resonant cavity to a transmission line carrying electromagnetic wave energy to the resonant cavity; at least one capacitive reactive element, and at least one inductive reactive element disposed within the resonant cavity; the capacitive reactive member separated from the chamber walls of the resonant cavity by a first predefined gap, with the capacitive reactive member and the chamber walls of the resonant cavity oriented approximately tangential to the strong magnetic field; the capacitive and the inductive reactive elements spaced apart from the plasma a second predetermined distance which at least partially determines the frequency of the launched waves; and the resonant cavity cooperating with the capacitive and the inductive reactive elements so as to launch electromagnetic waves in the range of frequencies, toward the plasma.