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Sample records for addressable vertical-cavity laser

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Vertical Cavity Surface Emitting Lasers for communications

    NASA Astrophysics Data System (ADS)

    Rorison, J. M.

    2000-12-01

    Vertical Cavity Surface Emitting Lasers (VCSELs) are a novel type of laser in which the lasing light is emitted from the surface of the device, perpendicular to the gain layer, rather than from the edge of the laser, parallel to the gain layer. These lasers show interesting behavior, particularly involving mode dynamics and polarization. They show promising characteristics for use in communications applications but their behavior needs to be further understood before they can reach their potential. This chapter attempts to review VCSELs generally and discuss their use in communications systems.

  6. Numerical modeling of vertical cavity semiconductor lasers

    SciTech Connect

    Chow, W.W.; Hadley, G.R.

    1996-08-01

    A vertical cavity surface emitting laser (VCSEL) is a diode laser whose optical cavity is formed by growing or depositing DBR mirror stacks that sandwich an active gain region. The resulting short cavity supports lasing into a single longitudinal mode normal to the wafer, making these devices ideal for a multitude of applications, ranging from high-speed communication to high-power sources (from 2D arrays). This report describes the development of a numerical VCSEL model, whose goal is to both further their understanding of these complex devices and provide a tool for accurate design and data analysis.

  7. 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.

  8. Selectively oxidized vertical-cavity laser performance and technology

    SciTech Connect

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

    1998-02-01

    The authors discuss revolutionary performance advances in selectively oxidized vertical-cavity surface emitting lasers (VCSELs), which have enabled low operating power laser diodes appropriate for aerospace applications. Incorporating buried oxide layers converted from AIGaAs layers within the laser cavity produces enhanced optical and electrical confinement enabling superior laser performance, such as high efficiency and modulation bandwidth. VCSELs also shown to be viable over varied environmental conditions such as ambient temperature and ionized radiation. The development of novel VCSEL technologies for advanced system applications is also described. Two dimensional individually addressable VCSEL arrays exhibit uniform threshold and operating characteristics. Bottom emitting 850 nm VCSEL arrays fabricated using wafer fusion are also reported.

  9. Vertical-cavity surface-emitting laser device

    DOEpatents

    Hadley, G. Ronald; Lear, Kevin L.; Awyoung, Adelbert; Choquette, Kent D.

    1999-01-01

    A vertical-cavity surface-emitting laser device. The vertical-cavity surface-emitting laser (VCSEL) device comprises one or more VCSELs with each VCSEL having a mode-control region thereabout, with the mode-control region forming an optical cavity with an effective cavity length different from the effective cavity length within each VCSEL. Embodiments of the present invention can be formed as single VCSELs and as one- or two-dimensional arrays of VCSELs, with either an index-guided mode of operation or an index anti-guided mode of operation being defined by a sign of the difference in the two effective cavity lengths.

  10. 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.

  11. Electrically injected visible vertical cavity surface emitting laser diodes

    SciTech Connect

    Schneider, Richard P.; Lott, James A.

    1994-01-01

    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.

  12. Vertical-cavity surface-emitting laser device

    DOEpatents

    Hadley, G.R.; Lear, K.L.; Awyoung, A.; Choquette, K.D.

    1999-05-11

    A vertical-cavity surface-emitting laser device is disclosed. The vertical-cavity surface-emitting laser (VCSEL) device comprises one or more VCSELs with each VCSEL having a mode-control region thereabout, with the mode-control region forming an optical cavity with an effective cavity length different from the effective cavity length within each VCSEL. Embodiments of the present invention can be formed as single VCSELs and as one- or two-dimensional arrays of VCSELs, with either an index-guided mode of operation or an index anti-guided mode of operation being defined by a sign of the difference in the two effective cavity lengths. 10 figs.

  13. Analysis and Design of Vertical Cavity Surface Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Yu, S. F.

    2003-08-01

    A practical, hands-on guidebook for the efficient modeling of VCSELs Vertical Cavity Surface Emitting Lasers (VCSELs) are a unique type of semiconductor laser whose optical output is vertically emitted from the surface as opposed to conventional edge-emitting semiconductor lasers. Complex in design and expensive to produce, VCSELs nevertheless represent an already widely used laser technology that promises to have even more significant applications in the future. Although the research has accelerated, there have been relatively few books written on this important topic. Analysis and Design of Vertical Cavity Surface Emitting Lasers seeks to encapsulate this growing body of knowledge into a single, comprehensive reference that will be of equal value for both professionals and academics in the field. The author, a recognized expert in the field of VCSELs, attempts to clarify often conflicting assumptions in order to help readers achieve the simplest and most efficient VCSEL models for any given problem. Highlights of the text include: * A clear and comprehensive theoretical treatment of VCSELs * Detailed derivations for understanding the operational principles of VCSELs * Mathematical models for the investigation of electrical, optical, and thermal properties of VCSELs * Case studies on the mathematical modeling of VCSELs and the implementation of simulation programs

  14. High-speed modulation of vertical cavity surface emitting lasers

    SciTech Connect

    Hietala, V.M.; Armendariz, M.G.; Choquette, K.D.; Lear, K.L.

    1998-03-01

    This report summarizes work on the development of high-speed vertical cavity surface emitting lasers (VCSELs) for multi-gigabit per second optical data communications applications (LDRD case number 3506.010). The program resulted in VCSELs that operate with an electrical bandwidth of 20 GHz along with a simultaneous conversion efficiency (DC to light) of about 20%. To achieve the large electrical bandwidth, conventional VCSELs were appropriately modified to reduce electrical parasitics and adapted for microwave probing for high-speed operation.

  15. Spectrally and temporally resolved laser emission from vertical cavity surface emitting lasers

    SciTech Connect

    Sinclair, M.; Gourley, P.L.; Brennan, T.M.; Hammons, B.E.

    1992-12-31

    We have measured the laser emission spectra of several vertical cavity surface emitting lasers following pulsed laser excitation, with a time resolution of < 1 ps. Correlations between the observed pulse widths and cavity lifetimes were observed.

  16. Wafer bonded 1.55 mum vertical cavity laser arrays for wavelength division multiplexing

    NASA Astrophysics Data System (ADS)

    Karim, Adil Mahmood

    Vertical cavity lasers in the 1.55 mum wavelength band are attractive sources for optical networks. Previous devices have been limited by low output power and poor thermal performance. In this work, novel wafer bonding techniques were developed to create high-performance 1.55 mum vertical cavity lasers and a new class of multiple wavelength vertical cavity laser arrays. Wafer bonding enables the integration of thermally conductive GaAs/AlGaAs mirrors and traditional InP/InGaAsP active regions. A superlattice barrier was used as a buffer layer during bonding to reduce the number of non-radiative recombination centers in the active region. The surface of these superlattice layers was patterned prior to bonding to define multiple wavelength cavities. Continuous-wave operation was achieved at temperatures up to 105°C. This is the highest reported lasing temperature for a 1.55 mum vertical cavity laser. Threshold currents of 0.8 mA were measured. The peak output power at 20°C was 0.7 mW. The peak output power at 80°C was 0.2 mW. Single-mode operation with a side-mode suppression ration in excess of 40 dB was observed for a 5 mum aperture device. Four-channel arrays were also fabricated. The wavelength span was 1509.1--1524.4 nm with channel spacing of approximately 5 nm. This is the first demonstration of an independently addressable, multiple-wavelength vertical cavity laser array at 1.55 mum. Threshold currents of 1.0 mA and peak output powers of 0.5 mW were measured for array elements. Thermal and optical crosstalk between array elements are negligible, due to the high thermal conductivity of the bottom mirror and large device pitch.

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

    PubMed Central

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

    2013-01-01

    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. PMID:23884078

  18. Fabrication and performance of selectively oxidized vertical-cavity lasers

    SciTech Connect

    Choquette, K.D.; Lear, K.L.; Schneider, R.P. Jr.; Geib, K.M.; Figiel, J.J.; Hull, R.

    1995-11-01

    The authors report the high yield fabrication and reproducible performance of selectivity oxidized vertical-cavity surface emitting lasers. They show that liner oxidation rates of AlGaAs without an induction period allows reproducible fabrication of buried oxide current apertures within monolithic distributed Bragg reflectors. The oxide layers do not induce obvious crystalline defects, and continuous wave operation in excess of 650 h has been obtained. The high yield fabrication enables relatively high laser performance over a wide wavelength span. They observe submilliamp threshold currents over a wavelength range of up to 75 nm, and power conversion efficiencies at 1 mW output power of greater than 20% over a 50-nm wavelength range.

  19. Oxide-Confined Vertical-Cavity Surface-Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Liu, W. L.; Li, L.; Zhong, J. C.; Zhao, Y. J.; Zeng, L. N.; Yan, C. L.

    Novel distributed Bragg reflectors (DBRs) with 6-pair-GaAs/AlAs short period superlattice for the oxide-confined vertical-cavity surface-emitting lasers (VCSEL) are designed. They are for the VCSEL that emits at 840 nm and is grown with 34-period n-type mirrors, three-quantum-well active region, and 22-period p-type mirrors. In addition, a 35-nm-layer of Al0.98Ga0.02As was inserted in the top mirrors for being selectively oxidized. The maximum output power is more than 2 mW with low threshold current of about 2 mA. The fact that the device's threshold current in both CW and pulsed operation depends slightly on the operation temperature shows its higher characteristic temperature (T0).

  20. Low threshold planarized vertical-cavity surface-emitting lasers

    SciTech Connect

    Geels, R.S.; Corzine, S.W.; Scott, J.W.; Young, D.B.; Coldren, L.A. )

    1990-04-01

    Vertical-cavity surface-emitting lasers have been fabricated utilizing a novel self-aligned process to provide planarized contacts. A single 80 {angstrom} In{sub 0.2}Ga{sub 0.8}As strained quantum well was used in the active region. Emission was at 963 nm. Threshold currents under continuous-wave room temperature operation of 1.1 mA, at 4.0 V bias, were measured for numerous 12 {times} 12 {mu}m square devices. Corresponding threshold current densities are 800 A/cm{sup 2} (600 A/cm{sup 2} for broad area devices). These are the lowest figures yet reported for this type of device. The effect of interface grading on mirror resistance was also investigated.

  1. 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.

  2. 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.

  3. Double photonic crystal vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Viktorovitch, Pierre; Sciancalepore, Corrado; Bakir, Badhise Ben; Letartre, Xavier; Seassal, Christian

    2013-03-01

    The periodic patterning of the optical medium achieved through photonic crystal membranes (PCMs) can be employed for controlling the resonant coupling of external radiation continuum to above-the-light-line flat edges of the folded band structure in strongly corrugated waveguides, resulting in high reflectivity for an efficient quasi-3D light harnessing. Recently, vertical-cavity surface-emitting lasers (VCSELs) emitting in C-band using a double set of one-dimensional Si/SiO2 photonic crystals as compact, flexible, and power efficient mirrors have been realized within a mass-scale fabrication paradigm by employing standard 200-mm microelectronics pilot lines. Conceived as the basic building block for photonics-on-silicon back-end integration of group III-V laser microsources, the extreme flexibility of the novel photonic architecture enables to perform a tailored modal selection of the optical cavity, including polarization and far-field control. It also offers a wide range of functionality, such as on-chip optical routing and a variety of efficient wavelength tuning-trimming schemes. Device compactness ensures a considerable reduction in the device footprint, power consumption, and parasitics. Furthermore, high fabrication yields obtained thanks to the state-of-the-art molecular wafer bonding of III-V alloys on silicon conjugate excellent device performances with cost-effective high-throughput production, indicating strong perspective industrial potential.

  4. 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.

  5. 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.

  6. 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.

  7. III-Nitride Vertical-Cavity Surface-Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Leonard, John T.

    Vertical-cavity surface-emitting lasers (VCSELs) have a long history of development in GaAs-based and InP-based systems, however III-nitride VCSELs research is still in its infancy. Yet, over the past several years we have made dramatic improvements in the lasing characteristics of these highly complex devices. Specifically, we have reduced the threshold current density from ˜100 kA/cm2 to ˜3 kA/cm2, while simultaneously increasing the output power from ˜10 muW to ˜550 muW. These developments have primarily come about by focusing on the aperture design and intracavity contact design for flip-chip dual dielectric DBR III-nitride VCSELs. We have carried out a number of studies developing an Al ion implanted aperture (IIA) and photoelectrochemically etched aperture (PECA), while simultaneously improving the quality of tin-doped indium oxide (ITO) intracavity contacts, and demonstrating the first III-nitride VCSEL with an n-GaN tunnel junction intracavity contact. Beyond these most notable research fronts, we have analyzed numerous other parameters, including epitaxial growth, flip-chip bonding, substrate removal, and more, bringing further improvement to III-nitride VCSEL performance and yield. This thesis aims to give a comprehensive discussion of the relevant underlying concepts for nonpolar VCSELs, while detailing our specific experimental advances. In Section 1, we give an overview of the applications of VCSELs generally, before describing some of the potential applications for III-nitride VCSELs. This is followed by a summary of the different material systems used to fabricate VCSELs, before going into detail on the basic design principles for developing III-nitride VCSELs. In Section 2, we outline the basic process and geometry for fabricating flip-chip nonpolar VCSELs with different aperture and intracavity contact designs. Finally, in Section 3 and 4, we delve into the experimental results achieved in the last several years, beginning with a discussion on

  8. 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.

  9. High-speed modulation, wavelength, and mode control in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Ledentsov, Nikolay N.; Kropp, Jörg-R.; Shchukin, Vitaly A.; Steinle, Gunther; Ledentsov, Nikolay N.; Turkiewicz, Jarek P.; Wu, Bo; Qiu, Shaofeng; Ma, Yanan; Feng, Zhiyong; Burger, Sven; Schmidt, Frank; Caspar, Christoph; Freund, Ronald; Choquette, Kent D.

    2015-03-01

    We address demands and challenges for GaAs-based Vertical-Cavity Surface-Emitting Lasers (VCSEL) in data communication. High speed modulation (~50Gb/s) at a high reliability can be realized with a proper VCSEL design providing a high differential gain. In cases where extreme temperatures are required electrooptic modulation in duo- cavity VCSELs can be applied as the modulation speed and the differential gain are decoupled. Single mode operation of VCSELs is necessary to counteract the chromatic dispersion of glass fibers and extend distances to above 1 km while using standard multimode fibers. Oxide layer engineering or using of photonic crystals can be applied. Parallel error-free 25Gb/s transmission over OM3 and OM4 multimode fiber (~0.5 and 1 km, respectively) is realized in large aperture oxide-engineered VCSEL arrays. Passive cavity VCSELs with gain medium placed in the bottom DBR and the upper part made of dielectric materials a complete temperature insensitivity of the emission wavelength can be realized. Engineering of the oxide aperture region enables near field vertical cavity lasers. Such devices can operate in a high- order transverse mode with an effective mode angle beyond the angle of the total internal reflection at the semiconductor-air interface. Near filed coupling to optical fibers and waveguides becomes possible in this case.

  10. 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.

  11. 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.

  12. 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.

  13. Polarization characteristics, control, and modulation of vertical-cavity surface emitting lasers

    SciTech Connect

    Choquette, K.D.; Lear, K.L.; Schneider, R.P. Jr.; Figiel, J.J.; Kilcoyne, S.P.; Hagerott-Crawford, M.; Zolper, J.C.; Leibenguth, R.E.

    1995-03-01

    The gain-dependent polarization properties of vertical-cavity surface emitting lasers and methods for polarization control and modulation are discussed. The partitioning of power between the two orthogonal eigen polarizations is shown to depend upon the relative spectral alignment of the nondegenerate polarization cavity resonances with the laser gain spectrum. A dominant polarization can thus be maintained by employing a blue-shifted offset of the peak laser gain relative to the cavity resonance wavelength. Alternatively, the polarization can be controlled through use of anisotropic transverse cavity geometries. The orthogonal eigen polarizations are also shown to enable polarization modulation. By exploiting polarization switching transitions in cruciform lasers, polarization modulation of the fundamental mode up to 50 MHz is demonstrated. At lower modulation frequencies, complementary digital polarized output or frequency doubling of the polarized output is obtained. Control and manipulation of vertical-cavity laser polarization may prove valuable for present and future applications.

  14. Vertical cavity surface-emitting semiconductor lasers with injection laser pumping

    NASA Astrophysics Data System (ADS)

    McDaniel, D. L., Jr.; McInerney, J. G.; Raja, M. Y. A.; Schaus, C. F.; Brueck, S. R. J.

    1990-05-01

    Continuous-wave GaAs/GaAlAs edge-emitting diode lasers were used to pump GaAs/AlGaAs and InGaAs/AlGaAs vertical cavity surface-emitting lasers (VCSELs) with resonant periodic gain (RPG) at room temperature. Pump threshold as low as 11 mW, output powers as high as 27 mW at 850 nm, and external differential quantum efficiencies of about 70 percent were observed in GaAs/AlGaAs surface -emitters; spectral brightness 22 times that of the pump laser was also observed. Output powers as high as 85 mW at 950 nm and differential quantum efficiencies of up to 58 percent were recorded for the InGaAs surface-emitting laser. This is the highest quasi-CW output power ever reported for any RPG VCSEL, and the first time such a device has been pumped using an injection laser diode.

  15. 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.

  16. 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.

  17. Many body effects in the temperature dependence of threshold in a vertical-cavity surface-emitting laser

    SciTech Connect

    Chow, W.W.; Corzine, S.W.; Young, D.B.; Coldren, L.A.

    1995-05-08

    The temperature dependence of the threshold in a vertical-cavity surface-emitting laser is investigated. Comparison of theory with experiment indicates that many-body Coulomb interactions play an important role.

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

    PubMed

    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

  19. 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

  20. 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.

  1. 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%.

  2. 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.

  3. High-contrast grating reflectors for 980 nm vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Gebski, M.; Kuzior, O.; Wasiak, M.; Szerling, A.; Wójcik-Jedlińska, A.; Pałka, N.; Dems, M.; Xie, Y. Y.; Xu, Z. J.; Wang, Q. J.; Zhang, D. H.; Czyszanowski, T.

    2015-02-01

    This paper presents results of computer simulation of 1D monolithic high refractive index contrast grating (MHCG) reflector also called surface grating reflector (SGR). We analyzed optical properties of the GaAs reflector designed for 980 nm wavelength with respect to the grating parameters variation. We also determined the electric field patterns after reflection from the structure in several cases of parameters variation. We show that thanks to the scalability and design simplicity, proposed design is a promising candidate for simple, next generation vertical cavity surface emitting lasers emitting from ultra-violet to infrared.

  4. 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.

  5. Mode selectivity study of vertical-cavity surface-emitting lasers

    SciTech Connect

    Liu, G.; Seurin, J.; Chuang, S.L.; Babic, D.I.; Corzine, S.W.; Tan, M.; Barnes, D.C.; Tiouririne, T.N.

    1998-08-01

    Mode selectivity of an air-post index-guided vertical-cavity surface-emitting laser structure operating at 1550 nm is investigated using a full-vector Maxwell-equation solver with a finite-difference time-domain method. The resonance wavelengths, quality factors, and spatial field distributions are calculated for the three lowest-order modes. Transverse-mode competition is quantitatively described as a function of the cavity size and the pillar etch depth. {copyright} {ital 1998 American Institute of Physics.}

  6. 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%.

  7. 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.

  8. Low-frequency fluctuations in vertical cavity lasers: Experiments versus Lang-Kobayashi dynamics

    SciTech Connect

    Torcini, Alessandro; Barland, Stephane; Giacomelli, Giovanni; Marin, Francesco

    2006-12-15

    The limits of applicability of the Lang-Kobayashi (LK) model for a semiconductor laser with optical feedback are analyzed. The model equations, equipped with realistic values of the parameters, are investigated below the solitary laser threshold where low-frequency fluctuations (LFF's) are usually observed. The numerical findings are compared with experimental data obtained for the selected polarization mode from a vertical cavity surface emitting laser (VCSEL) subject to polarization selective external feedback. The comparison reveals the bounds within which the dynamics of the LK model can be considered as realistic. In particular, it clearly demonstrates that the deterministic LK model, for realistic values of the linewidth enhancement factor {alpha}, reproduces the LFF's only as a transient dynamics towards one of the stationary modes with maximal gain. A reasonable reproduction of real data from VCSEL's can be obtained only by considering the noisy LK or alternatively deterministic LK model for extremely high {alpha} values.

  9. InGaAs vertical-cavity surface-emitting lasers

    SciTech Connect

    Geels, R.S.; Corzine, S.W.; Coldren, L.A. )

    1991-06-01

    In this paper the authors give theoretical and experimental results for vertical-cavity surface-emitting lasers (VCSEL's). The modeling is applied to the design of InGaAs VCSEL's A simple method is introduced to calculate the reflectivity of semiconductor stack mirrors with graded interfaces and compound metal/semiconductor stack mirrors. The theoretical predictions are compared to results from actual device measurements. A novel technique is introduced to determine material parameters: fabrication of in-plane lasers from VCSEL material. The procedure used to determine the optical model in such an in-plane laser is described. Using the insight gained from our modeling, we have increased our external efficiency to {gt}30% with a threshold current density of 1 kA/cm{sup 2}. Linewidth measurements on very high reflectivity VCSEL's have indicated widths as low as 85 MHz and linewidth-power products of 5 MHz {center dot} mW.

  10. Square-wave switching by crossed-polarization gain modulation in vertical-cavity semiconductor lasers

    SciTech Connect

    Mulet, J.; Giudici, M.; Javaloyes, J.; Balle, S.

    2007-10-15

    We study experimentally and theoretically the effects of crossed-polarization reinjection (XPR) on the output characteristics of a vertical-cavity semiconductor laser. We find a set of parameters values for which each polarization component develops a square-wave modulation at a period close to twice the reinjection delay. We analyze the regularity of this modulation in terms of the laser pumping current and of the reinjection level. These observations are numerically reproduced within the spin-flip model modified to account for XPR. In particular, the degradation of the square-wave switching is linked to the finite value of the spin-flip rate, and it occurs when the current approaches the boundaries of polarization bistability.

  11. Stable polarization self-modulation in vertical-cavity surface-emitting lasers

    SciTech Connect

    Li, H.; Hohl, A.; Gavrielides, A.; Hou, H.; Choquette, K.D.

    1998-05-01

    The characteristics of polarization self-modulation in a vertical-cavity surface-emitting laser (VCSEL) were studied for frequencies up to {approx}9 GHz both experimentally and theoretically. Polarization self-modulation was obtained by rotating the linearly polarized output of the VCSEL by 90{degree} and reinjecting it into the laser. Experimentally we simultaneously recorded time traces, optical and radio-frequency spectra. We found for increasing modulation frequencies that the output characteristics changed from square-wave to sinusoidal and the VCSEL system assumed new polarization eigenstates that are different from the free-running VCSEL eigenstates. We modeled polarization self-modulation as an interband process and found a good qualitative agreement between our experimental and numerical results. {copyright} {ital 1998 American Institute of Physics.}

  12. 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.

  13. 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.

  14. Vertical cavity surface emitting lasers emitting near 1.5 {mu}m with Sb-based reflectors

    SciTech Connect

    Blum, O.; Klem, J.F.; Vawter, G.A.

    1998-04-01

    We describe use of AlAsSb/AlGaAsSb lattice matched to InP for distributed Bragg reflectors. These structures are integral to several surface normal devices, in particular vertical cavity surface emitting lasers. The high refractive index ratio of these materials allows formation of a highly reflective mirror with relatively few mirror pairs. As a result, we have been able to show for the first time the 77K CW operation of an optically pumped, monolithic, all-epitaxial vertical cavity laser, emitting at 1.56 {mu}m.

  15. 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.

  16. Growth of vertical-cavity surface emitting lasers by metalorganic vapor phase epitaxy

    SciTech Connect

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

    1996-10-01

    We present growth and characterization of visible and near-infrared vertical-cavity surface emitting lasers (VCSELs) grown by metalorganic vapor phase epitaxy. Discussions on the growth issue of VCSEL materials include growth rate and composition control using an {ital in}{ital situ} normal-incidence reflectometer, comprehensive p- and n-type doping study in AlGaAs by CCl{sub 4} and Si{sub 2}H{sub 6} over the entire composition range, and optimization of ultra-high material uniformity. We also demonstrate our recent achievements of all-AlGaAs VCSELs which include the first room-temperature continuous- wave demonstration of 700-nm red VCSELs and high-efficiency and low- threshold voltage 850-nm VCSELs.

  17. Vertical cavity surface emitting laser based optoelectronic asynchronous transfer mode switch

    SciTech Connect

    Wilmsen, C.W.; Duan, C.; Collington, J.R.; Dames, M.P.; Crossland, W.A.

    1999-07-01

    Large broadband asynchronous transfer mode (ATM) switching nodes require novel hardware solutions that could benefit from the inclusion of optical interconnect technology, since electronic solutions are limited by pin out and by the capacitance/inductance of the interconnections. We propose, analyze and demonstrate a new three stage free space optical switch that utilizes vertical cavity surface emitting lasers (VCSELs) for the optical interconnections, a liquid crystal spatial light modulator (SLM) as a reconfigurable shutter and relatively simple optics for fan out and fan in. A custom complementary metal oxide semiconductor (CMOS) chip is required to introduce a time delay in the optical bit stream and to drive the VCSELs. Analysis shows that the switch should be scalable to 1024{times}1024, which would require 2048 {approximately}2 mW VCSELs. {copyright} {ital 1999 Society of Photo-Optical Instrumentation Engineers.}

  18. Numerical model of capacitance in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Wasiak, M.; Śpiewak, P.; Moser, P.; Walczak, J.; Sarzała, R. P.; Czyszanowski, T.; Lott, J. A.

    2016-05-01

    In this paper we present a model of impedance and modulation time constants for vertical-cavity surface-emitting lasers (VCSELs) operating above threshold current. A 3D numerical model of potential distribution in the device under a constant bias is used to determine resistances and capacitances of an appropriate equivalent circuit. The model has been verified by comparing the theoretical and measured impedance as a function of frequency Z(f). The measured Z(f) is determined from S 11 small signal modulation experiments. The comparison has been performed for frequencies up to 40 GHz and a wide range of above threshold currents, for two oxide-confined VCSELs of different aperture diameters. We obtained a very good quantitative agreement for frequencies up to about 15 GHz and qualitative agreement over the entire range of currents and frequencies.

  19. Comprehensive numerical model for cw vertical-cavity surface-emitting lasers

    SciTech Connect

    Hadley, G.R.; Lear, K.L.; Warren, M.E.; Choquette, K.D.; Scott, J.W.; Corzine, S.W.

    1995-03-01

    The authors present a comprehensive numerical model for vertical-cavity surface-emitting lasers that includes all major processes effecting cw operation of axisymmetric devices. In particular, the model includes a description of the 2D transport of electrons and holes through the cladding layers to the quantum well(s), diffusion and recombination processes of these carriers within the wells, the 2D transport of heat throughout the device, and a multi-lateral-mode effective index optical model. The optical gain acquired by photons traversing the quantum wells is computed including the effects of strained band structure and quantum confinement. They employ the model to predict the behavior of higher-order lateral modes in proton-implanted devices, and to provide an understanding of index-guiding in devices fabricated using selective oxidation.

  20. Critical slowing down in polarization switching of vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Heng; Li, Yueh-Chen; Kuo, Wang-Chuang; Yen, Tsu-Chiang

    2014-05-01

    This research investigated the critical slowing down in polarization switching (PS) of vertical-cavity surface-emitting lasers (VCSELs). The experiments were performed by step-function current injection in two types: step-up and stepdown. In the case of step-up and step-down, the relationship between relaxation time and final current in this experiment resembles critical slowing down (CSD). The critical currents of two step-function current experiment are compared. The PS in this experiment is a static case. We also find that the divergence of relaxation time follow a power law. These results contribute to the understanding of the mechanism of CSD in VCSEL's PS (VPS).

  1. GaN-based vertical cavity surface emitting lasers with periodic gain structures

    NASA Astrophysics Data System (ADS)

    Matsui, Kenjo; Kozuka, Yugo; Ikeyama, Kazuki; Horikawa, Kosuke; Furuta, Takashi; Akagi, Takanobu; Takeuchi, Tetsuya; Kamiyama, Satoshi; Iwaya, Motoaki; Akasaki, Isamu

    2016-05-01

    We have achieved room-temperature CW operations of GaN-based vertical cavity surface emitting lasers (VCSELs) with periodic gain structures (PGSs). The PGS-VCSEL consisted of 4.5λ-thick optical cavity length and two GaInN 5-quantum-well (QW) active regions separated with a Mg-doped GaN intermediate layer. The uniform carrier injection into the two active regions was also investigated using light-emitting diodes (LEDs). It is found that the use of an optimum Mg concentration in the intermediate layers improves the uniform carrier injection in the two active regions. From these results, we realized the CW operation of VCSELs with PGSs grown on AlInN/GaN distributed Bragg reflectors (DBRs). The VCSEL under CW operation showed a threshold current density of 16.5 kA/cm2 and its operation wavelength was 409.9 nm.

  2. Dynamics of a low-threshold optically pumped organic vertical-cavity surface-emitting laser

    NASA Astrophysics Data System (ADS)

    Shayesteh, Mohammad Reza; Darvish, Ghafar

    2016-06-01

    We propose a low-threshold optically pumped organic vertical-cavity surface-emitting laser (OVCSEL). This device has the capability to apply both electrical and optical excitation. The microcavity structure consists of an organic light emitting diode with field-effect electron transport inserted in a high-quality factor double distributed Bragg reflector. The simulated quality factor of the microcavity is shown to be as high as 16,000. Also, we investigate threshold behaviour and the dynamics of the optically pumped OVCSEL with sub-picosecond pulses. Results from numerical simulation show that lasing threshold is 12.8 pJ/0.64 µJ cm-2 when pumped by sub-picosecond pulses of λ = 400 nm wavelength light.

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

    SciTech Connect

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

    1994-04-01

    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 manufacture. Scaling VCSELs to higher power outputs requires increasing the device area, which leads to transverse mode control difficulties if devices become larger than about 5 microns. One approach to increasing the device size while maintaining a well controlled transverse mode profile is formation of coupled or phase-locked two-dimensional arrays of VCSELs that are individually single-transverse mode. Such arrays have unique optical properties, not all of which are desirable. This paper covers some of the basic principles of these devices and reviews recent work on device designs, fabrication and operation. A technique for improving the far-field properties of the arrays is demonstrated and performance limitations are discussed.

  4. Comprehensive numerical modeling of vertical-cavity surface-emitting lasers

    SciTech Connect

    Hadley, G.R.; Lear, K.L.; Warren, M.E.; Choquette, K.D.; Scott, J.W.; Corzine, S.W.

    1996-04-01

    The authors present a comprehensive numerical model for vertical-cavity surface-emitting lasers that includes all major processes affecting cw operation of axisymmetric devices. In particular, the model includes a description of the 2-D transport of electrons and holes through the cladding layers to the quantum well(s), diffusion and recombination of these carriers within the wells, the 2-D transport of heat throughout the device, and a multilateral-mode effective index optical model. The optical gain acquired by photons traversing the quantum wells is computed including the effects of strained band structure and quantum confinement. The authors employ the model to predict the behavior of higher-order lateral modes in proton-implanted devices and to provide an understanding of index-guiding in devices fabricated using selective oxidation.

  5. MOVPE growth of visible vertical-cavity surface-emitting lasers (VCSELs)

    NASA Astrophysics Data System (ADS)

    Zorn, M.; Knigge, A.; Zeimer, U.; Klein, A.; Kissel, H.; Weyers, M.; Tränkle, G.

    2003-02-01

    This paper summarises the development of the epitaxial growth process for visible vertical-cavity surface-emitting lasers (VCSELs) in metal-organic vapour phase epitaxy (MOVPE). The production of these devices which are of particular interest, e.g. for data communications via plastic optical fibres or for consumer electronics, is a real challenge for MOVPE due to the unfavourable material properties in the AlInGaP/AlGaAs material system necessary for this wavelength range. The following stages of the growth process have been investigated with the intention to reach maximum output power and high temperature stability: distributed Bragg reflector (DBR) doping, interface grading, number of p:DBR pairs, oxide confinement layer, cavity design, number of quantum wells, and wavelength alignment. After optimisation devices with record high output powers of more than 4 mW at 650 nm and 10 mW at 670 nm could be fabricated. Single mode VCSELs show laser emission up to 65°C at 650 nm and 87°C at 670 nm. Laser operation for more than 1000 h demonstrates the potential of these devices for industrial applications.

  6. Status and future of GaN-based vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Feezell, Daniel F.

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) offer distinct advantages over conventional edge-emitting lasers, including lower power consumption, single-longitudinal-mode operation, circularly symmetric output beams, waferlevel testing, and the ability to form densely packed, two-dimensional arrays. High-performance GaN-based VCSELs are well suited for applications in high-density optical data storage, high-resolution printing, lighting, displays, projectors, miniature atomic clocks, and chemical/biological sensing. Thus far, the performance of these devices has been limited by challenges associated with the formation of high-reflectance distributed Bragg reflectors (DBRs), optical mode confinement, carrier transport, lateral current spreading, polarization-related electric fields, and cavity-length control. This manuscript discusses the state-of-the-art results for electrically injected GaN-based VCSELs and reviews approaches to overcome the key challenges currently preventing higher performance devices. The manuscript also describes the development of nonpolar GaN-based VCSELs on free-standing GaN. Nonpolar orientations exhibit anisotropic optical gain within the quantum well plane and uniquely enable VCSELs with a well-defined and stable polarization state. In addition, a detailed description of a band-gap-selective photoelectrochemical etching (BGS PECE) process for substrate removal and fine cavity length control on free-standing GaN substrates is provided.

  7. Energy-efficiency of optical network units with vertical-cavity surface-emitting lasers.

    PubMed

    Wong, Elaine; Mueller, Michael; Dias, Maluge P I; Chan, Chien Aun; Amann, Markus C

    2012-07-01

    The energy savings of 10 Gbps vertical-cavity surface-emitting lasers (VCSELs) for use in energy-efficient optical network units (ONUs) is critically examined in this work. We experimentally characterize and analytically show that the fast settling time and low power consumption during active and power-saving modes allow the VCSEL-ONU to achieve significant energy savings over the distributed feedback laser (DFB) based ONU. The power consumption per customer using VCSEL-ONUs and DFB-ONUs, is compared through an illustrative example of 10G-EPON for Video-on-Demand delivery. Using energy consumption models and numerical analyses in sleep and doze mode operations, we present an impact study of network and protocol parameters, e.g. polling cycle time, network load, and upstream access scheme used, on the achievable energy savings of VCSEL-ONUs over DFB-ONUs. Guidance on the specific power-saving mode to maximum energy savings throughout the day, is also presented. PMID:22772191

  8. Time-dependent model for vertical-cavity surface-emitting laser

    SciTech Connect

    Thode, L.; Csanak, G.; Hotchkiss, R.; Snell, C.

    1995-03-01

    Two models have been developed to simulate a vertical-cavity surface-emitting laser (VCSEL). The first model is a two-dimensional time-dependent solution of Maxwell`s equations, with frequency-independent bulk dielectric and absorption coefficients. These bulk coefficients depend upon the material, lattice temperature, and carrier concentration. This field model is coupled with a frequency-dependent gain model that describes the quantum well regions in the time domain. Treatment of frequency-dependent media in a finite-difference time-domain code is computationally intensive. On the other hand, because the volume of the active region is small relative to the volume of the distributed laser cavity, the computational overhead is reasonable. A semi-empirical transport model is used to describe the bulk transport, which drives the quantum well transport. In addition, the semi-empirical model provides a spatial distribution for the lattice temperature and carrier concentrations. The second model is a three-dimensional solution of Maxwell`s equations. The three-dimensional model can be used for cold-cavity calculations. The two-dimensional code generates the dielectric and absorption coefficients assuming azimuthal symmetry, providing the initial conditions for the three-dimensional calculation.

  9. Flip-chip bonding of vertical-cavity surface-emitting lasers using laser-induced forward transfer

    SciTech Connect

    Kaur, K. S. Missinne, J.; Van Steenberge, G.

    2014-02-10

    This letter reports the use of the Laser-Induced Forward Transfer (LIFT) technique for the fabrication of indium micro-bumps for the flip-chip (FC) bonding of single vertical-cavity surface-emitting laser chips. The FC bonded chips were electrically and optically characterized, and the successful functioning of the devices post-bonding is demonstrated. The die shear and life-time tests carried out on the bonded chips confirmed the mechanical reliability of the LIFT-assisted FC bonded assemblies.

  10. Flip-chip bonding of vertical-cavity surface-emitting lasers using laser-induced forward transfer

    NASA Astrophysics Data System (ADS)

    Kaur, K. S.; Missinne, J.; Van Steenberge, G.

    2014-02-01

    This letter reports the use of the Laser-Induced Forward Transfer (LIFT) technique for the fabrication of indium micro-bumps for the flip-chip (FC) bonding of single vertical-cavity surface-emitting laser chips. The FC bonded chips were electrically and optically characterized, and the successful functioning of the devices post-bonding is demonstrated. The die shear and life-time tests carried out on the bonded chips confirmed the mechanical reliability of the LIFT-assisted FC bonded assemblies.

  11. 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.

  12. Effect of pump wave reflections on the excitation of a dual-wavelength vertical-cavity surface-emitting laser

    SciTech Connect

    Morozov, M. Yu.; Morozov, Yu. A. Popov, V. V.

    2009-03-15

    The effect of pump wave reflections on the carrier generation rate and uniformity of carrier population in quantum wells (QWs) of a dual-wavelength vertical-cavity surface-emitting laser has been numerically analyzed. The laser's active region has been described within a mathematical model allowing any number of QWs and arbitrary distribution of carrier generation rate. It is shown that the optimal arrangement of blocking layers in the active region of a dual-wavelength vertical-cavity surface-emitting laser allows one to obtain a very uniform QW population. It is established that pump wave reflections significantly affect the local carrier generation rate and, therefore, the distribution of excited carriers in the laser structure.

  13. Optically pumped GaN vertical cavity surface emitting laser with high index-contrast nanoporous distributed Bragg reflector.

    PubMed

    Lee, Seung-Min; Gong, Su-Hyun; Kang, Jin-Ho; Ebaid, Mohamed; Ryu, Sang-Wan; Cho, Yong-Hoon

    2015-05-01

    Laser operation of a GaN vertical cavity surface emitting laser (VCSEL) is demonstrated under optical pumping with a nanoporous distributed Bragg reflector (DBR). High reflectivity, approaching 100%, is obtained due to the high index-contrast of the nanoporous DBR. The VCSEL system exhibits low threshold power density due to the formation of high Q-factor cavity, which shows the potential of nanoporous medium for optical devices. PMID:25969197

  14. Route to polarization switching induced by optical injection in vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Sciamanna, M.; Panajotov, K.

    2006-02-01

    We perform a theoretical investigation of the polarization dynamics in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the injected field has a linear polarization (LP) orthogonal to that of the free-running VCSEL. In agreement with previous experiments [Z. G. Pan , Appl. Phys. Lett. 63, 2999 (1993)], an increase of the injection strength may lead to a polarization switching accompanied by an injection locking. We find that this route to polarization switching is typically accompanied by a cascade of bifurcations to wave-mixing dynamics and time-periodic and possibly chaotic regimes. A detailed mapping of the polarization dynamics in the plane of the injection parameters (detuning, injection strength) unveils a large richness of dynamical scenarios. Of particular interest is the existence of another injection-locked solution for which the two LP modes both lock to the master laser frequency, i.e., an elliptically polarized injection-locked (EPIL) steady state. Modern continuation techniques allow us to unveil an unfolding mechanism of the EPIL solution as the detuning varies and also to link the existence of the EPIL solution to a resonance condition between the master laser frequency and the free-running frequency of the normally depressed LP mode in the slave laser. We furthermore report an additional case of bistability, in which the EPIL solution may coexist with the second injection-locked solution (the one being locked to the master polarization). This case of bistability is a result of the interaction between optical injection and the two-polarization-mode characteristics of VCSEL devices.

  15. 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.

  16. Vertical-cavity surface-emitting lasers for free-space interconnects

    NASA Astrophysics Data System (ADS)

    Coldren, Larry A.; Thibeault, Brian J.

    1996-01-01

    Vertical-cavity surface-emitting lasers have emerged as viable optical sources for low-power, low-cost interconnects. Work over the past few years has involved the use of several different structures, including etched-mesa, proton-implanted and dielectric apertured types. Although much of the development work aimed at manufacture has focused on the proton-implanted structure, more recent work suggests that lower threshold, higher-efficiency configurations may be more desirable for future applications. In this review, we briefly outline the different structures, introduce a general design formalism, overview growth and fabrication issues, summarize some integration work, and finally review some applications that have been identified. Free-space interconnects with AlGaAs/GaAs-based materials are emphasized including a brief summary of recent work on links using integrated microlenses on the VCSELs and detectors to avoid external optics. For completeness, we shall also include some discussion of the progress in long-wavelength InP-based (1.3 - 1.55 micrometer) and short- wavelength AlInGaP/GaAs-based (0.8 - 0.6 micrometer) VCSELs as well as guided-wave data links.

  17. Polarized optical injection in long-wavelength vertical-cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Hurtado, A.; Schires, K.; Khan, N.; Al-Seyab, R.; Henning, I. D.; Adams, M. J.

    2011-05-01

    We report a comprehensive study of the effects of polarized optical injection in long-wavelength Vertical-Cavity Surface Emitting Lasers (LW-VCSELs) emitting at the telecom wavelength of 1550nm. We analyze the properties of the polarization switching and bistability that can be induced in a 1550nm-VCSEL under orthogonal and arbitrary polarized optical injection. Additionally, we study the injection locking bandwidth of these devices when subject to different polarized optical injection. Furthermore, we also analyze the relationship existing between the injection locking bandwidth and the polarization switching range when the device is subject to orthogonally-polarized optical injection. Finally, we have identified regions of different nonlinear dynamics outside the injection locking bandwidth, including regions of periodic dynamics (such as limit cycle and period doubling) and chaos when these devices are subject to parallel and to orthogonal optical injection. This rich variety of nonlinear effects observed at 1550nm offers exciting prospects for novel practical uses of VCSELs in optical switching/routing applications in optical networks.

  18. 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

  19. Efficient vertical-cavity surface-emitting lasers for infrared illumination applications

    NASA Astrophysics Data System (ADS)

    Seurin, Jean-Francois; Xu, Guoyang; Guo, Baiming; Miglo, Alexander; Wang, Qing; Pradhan, Prachi; Wynn, James D.; Khalfin, Viktor; Zou, Wei-Xiong; Ghosh, Chuni; Van Leeuwen, Robert

    2011-03-01

    Infrared illumination is used in the commercial and defense markets for surveillance and security, for high-speed imaging, and for military covert operations. Vertical-cavity surface-emitting lasers (VCSELs) are an attractive candidate for IR illumination applications as they offer advantageous properties such as efficiency, intrinsically low diverging circular beam, low-cost manufacturing, narrow emission spectrum, and high reliability. VCSELs can also operate at high temperatures, thereby meeting the harsh environmental requirements of many illuminators. The efficiency and brightness of these VCSELs also reduce the requirements of the power supply compared to, for example, an LED approach. We present results on VCSEL arrays for illumination applications, as well as results on VCSEL-based illumination experiments. These VCSELs are used in illuminators emitting from a few Watts up to several hundred Watts. The emission of these VCSEL-based illuminators is speckle-free with no interference patterns. Infra-red illumination at up to 1,600ft (500m) from the source has been demonstrated using VCSEL-based illumination, without any optics.

  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. 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.

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

    PubMed

    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

  3. 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.

  4. Ultimate modulation bandwidth of 850 nm oxide-confined vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Bobrov, M. A.; Blokhin, S. A.; Maleev, N. A.; Kuzmenkov, A. G.; Blokhin, A. A.; Zadiranov, Yu M.; Troshkov, S. I.; Ledentsov, N. N.; Ustinov, V. M.

    2015-11-01

    Complex influence of photon lifetime (controlled by the mirror loss) and aperture size on the performance of 850 nm InGaAlAs oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with fully doped AlGaAs-based distributed Bragg reflectors (DBR) was investigated. We find a tradeoff between photon lifetime and gain nonlinearity for maximizing the optical bandwidth, leading to the optimum aperture size close to 4-6 μm. In spite of the reduced photon lifetime (from 4 ps to 1 ps), the excess damping caused by the current-induced self-heating limits the ultimate modulation bandwidth for the given VCSELs design at 24-25 GHz. Further improvement in high frequency characteristics can be facilitated by decrease of the heat generation and improvement of the heat removal from the active region as well as by proper engineering of the scattering loss at the oxide aperture while keeping the low capacitance optimizing design of the oxide aperture.

  5. Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture

    NASA Astrophysics Data System (ADS)

    Leonard, J. T.; Cohen, D. A.; Yonkee, B. P.; Farrell, R. M.; Margalith, T.; Lee, S.; DenBaars, S. P.; Speck, J. S.; Nakamura, S.

    2015-07-01

    We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3 nm quantum well width, 1 nm barriers, a 5 nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406 nm nonpolar VCSEL with a low threshold current density (˜16 kA/cm2), a peak output power of ˜12 μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss.

  6. Al-based thermal oxides in vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Liliental-Weber, Zuzanna; Ruvimov, S.; Swider, W.; Washburn, Jack; Li, Meng; Li, Gabriel S.; Chang-Hasnain, Constance J.; Weber, Eicke R.

    1997-01-01

    The microstructure of wet oxidized layers for vertical cavity surface emitting lasers (VCSELS) was studied by transmission electron microscopy. These oxides were formed by reaction of AlxGa1-xAs(x approximately equals 0 - 0.2) with water vapor at elevated temperatures (approximately 400 - 450 degrees Celsius). Due to the excellent carrier confinement provided by the oxidized layer, VCSELS have very low threshold currents and high efficiencies. This study revealed the accumulation of excess As at the interfaces with the oxidized layers and occasionally at the sample surface. To avoid this As accumulation on the sample surface, GaInP layers were grown on top of AlGaAs/GaAs layers. In this case no As was found at the layer surface. In addition, substantial shrinkage was found after oxidation, and the formation of large pores at the interface between the oxide and the high Al content layer, which might be detrimental for the device performance. The dependence of the oxide and interface quality on the composition of the oxidized layers, oxidation time and temperature are discussed in relation to the optical quality of VCSELs.

  7. Frequency tuning of polarization oscillations in spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Pusch, Tobias; Michalzik, Rainer; Gerhardt, Nils C.; Hofmann, Martin R.

    2016-04-01

    Controlling the coupled spin-photon dynamics in vertical-cavity surface-emitting lasers (VCSELs) is an attractive opportunity to overcome the limitations of conventional, purely charge based semiconductor lasers. Such spin-controlled VCSELs (spin-VCSELs) offer several advantages, like reduced threshold, spin amplification and polarization control. Furthermore the coupling between carrier spin and light polarization bears the potential for ultrafast polarization dynamics. By injecting spin-polarized carriers, the complex polarization dynamics can be controlled and utilized for high-speed applications. Polarization oscillations as resonance oscillations of the coupled spin- photon system can be generated using pulsed spin injection, which can be much faster than the intensity dynamics in conventional devices. We already demonstrated that the oscillations can be switched in a controlled manner. These controllable polarization dynamics can be used for ultrafast polarization-based optical data communication. The polarization oscillation frequency and therefore the possible data transmission rate is assumed to be mainly determined by the birefringence-induced mode-splitting. This provides a direct tool to increase the polarization dynamics toward higher frequencies by adding a high amount of birefringence to the VCSEL structure. Using this technique, we could recently demonstrate experimentally a birefringence splitting of more than 250 GHz using mechanical strain. Here, we employ the well-known spin-flip model to investigate the tuning of the polarization oscillation frequency. The changing mechanical strain is represented by a linear birefringence sweep to values up to 80πGHz. The wide tuning range presented enables us to generate polarization oscillation frequencies exceeding the conventional intensity modulation frequency in the simulated device by far, mainly dependent on the birefringence in the cavity only.

  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. 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

  10. Measurement of formaldehyde H{sub 2}CO concentration in air using diode vertical-cavity lasers

    SciTech Connect

    Zaslavskii, V Ya; Nadezhdinskii, Aleksandr I; Ponurovskii, Ya Ya; Chernin, S M

    2011-01-31

    A two-channel gas-analysing spectrometer is developed using a vertical-cavity surface-emitting laser (VCSEL) ({lambda}=1.79 {mu}m) and a multi-pass cell (total optical length 39 m) for studying the absorption spectra and measuring the background concentration of formaldehyde. High-resolution absorption spectra of formaldehyde are obtained within the VCSEL frequency tuning range ({lambda} {approx}1.79 {mu}m). Changing the background concentration of H{sub 2}CO, the sensitivity limit of the gas analyser is estimated. (laser applications)

  11. Simulation of Optical Resonators for Vertical-Cavity Surface-Emitting Lasers (vcsel)

    NASA Astrophysics Data System (ADS)

    Mansour, Mohy S.; Hassen, Mahmoud F. M.; El-Nozahey, Adel M.; Hafez, Alaa S.; Metry, Samer F.

    2010-04-01

    Simulation and modeling of the reflectivity and transmissivity of the multilayer DBR of VCSEL, as well as inside the active region quantum well are analyzed using the characteristic matrix method. The electric field intensity distributions inside such vertical-cavity structure are calculated. A software program under MATLAB environment is constructed for the simulation. This study was performed for two specific Bragg wavelengths 980 nm and 370 nm for achieving a resonant periodic gain (RPG)

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Development of III-Sb metamorphic DBR membranes on InP for vertical cavity laser applications

    NASA Astrophysics Data System (ADS)

    Addamane, S. J.; Mansoori, A.; Renteria, E. J.; Dawson, N.; Shima, D. M.; Rotter, T. J.; Hains, C. P.; Dawson, L. R.; Balakrishnan, G.

    2016-04-01

    Sb-based metamorphic DBR membranes are developed for InP-based vertical cavity laser applications. The reflectivity of the metamorphic DBR membrane is compared to the reflectivity of a lattice-matched DBR to characterize the optical quality of the DBR membrane. The metamorphic interface between InP and the III-antimonides is found to degrade the reflectivity of the DBR. Therefore, the growth temperature for the metamorphic DBR is optimized in order to obtain highly reflective (>99.8%) III-Sb thin-film membranes.

  17. 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.

  18. 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.

  19. Spacer and well pumping of InGaN vertical cavity semiconductor lasers with varying number of quantum wells

    NASA Astrophysics Data System (ADS)

    Debusmann, R.; Brauch, U.; Hoffmann, V.; Weyers, M.; Kneissl, M.

    2012-08-01

    We have investigated the dependence of the threshold pump power and slope efficiency of 415 nm (In)GaN vertical cavity surface emitting lasers on the wavelength of the pump source and the number of quantum wells. InGaN double quantum well resonant-periodic-gain structures with 6, 8, and 10 periods have been compared. By barrier and well pumping of the samples with a 375 nm dye laser, a nearly 10 times reduction of the laser threshold was observed compared to pumping with a 337 nm nitrogen laser source. The laser threshold was found to be independent of the number of quantum wells. The slope efficiency seems to be not affected by the pump wavelength and resonant-periodic-gain periods. The results are discussed with a rate equation model that takes into account the inhomogeneous pumping of the quantum wells and optical thickness variations in the resonant-periodic-gain structure.

  20. 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

  1. Measurement of refractive index and size of microparticles by optical traps generated by vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Flynn, Richard A.

    Optical trapping is a powerful tool in the biological sciences for manipulating cells, bacteria, viruses and organelles within cells. Optical traps can measure tiny biological forces on the order of picoNewtons or less. Currently particle manipulation and force measurement are the two main applications of optical traps. Conventional optical traps are generated by large expensive lasers aligned to full sized laboratory microscopes. In this era lab-on-a-chip bioanalysis technologies, the trapping laser must be miniaturized while the analysis capabilities of optical traps should be expanded to address a larger span of applications. The research that forms the basis of this dissertation involves the use of Vertical Cavity Surface Emitting Lasers (VCSELs) that are compact and arrayable for optical trapping and toward the development of a new and parallel method to measure the refractive index and size of a particle within an optical trap. The current best technique for measuring refractive index of a microparticle, refractometry, requires changing the fluid composition of the sample. The proposed optical trap technique works with any transparent fluid, a significant advantage for biological analysis. VCSEL arrays are applied to create arrays of optical traps. VCSEL arrays offer a low cost, low power, compact and arrayable solution to creating many simultaneous optical traps in parallel. VCSEL traps are shown to manipulate 3x3 arrays of biological cells. Cell types manipulated include red blood cells, yeast cells, NIH 3T3 Murine fibroblasts and rat primary hepatocytes. Forces exerted by VCSEL traps are quantified. Scaling of the array size is analyzed. VCSEL traps are applied to creating a co-culture of fibroblasts and hepatocytes, enabling the study of intracellular communication. Finally, VCSELS are shown to cause negligible damage to hepatocytes after 5 min exposure. The counter-propagating optical trap measurement (COTM) system extends the capabilities of optical

  2. 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.

  3. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy.

    PubMed

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications. PMID:27036765

  4. Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Liu, Lei; Chen, Rongzhang; Nelsen, Bryan; Huang, Xi; Lu, Yongfeng; Chen, Kevin

    2016-03-01

    This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, and limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.

  5. 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. PMID:21479012

  6. 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.

  7. Lateral integration of vertical-cavity surface-emitting laser and slow light Bragg reflector waveguide devices.

    PubMed

    Shimada, Toshikazu; Matsutani, Akihiro; Koyama, Fumio

    2014-03-20

    We present the modeling and the experiment on the lateral integration of a vertical-cavity surface-emitting laser (VCSEL) and slow light Bragg reflector waveguide devices. The modeling shows an efficient direct-lateral coupling from a VCSEL to an integrated slow light waveguide. The calculated result shows a possibility of 13 dB chip gain and an extinction ratio over 5 dB for a compact slow light semiconductor optical amplifier (SOA) and electroabsorption modulator integrated with a VCSEL, respectively. We demonstrate an SOA-integrated VCSEL, exhibiting the maximum output power over 6 mW. Also, we fabricate a sub-50-μm long electroabsorption modulator laterally integrated with a VCSEL. An extinction ratio of over 15 dB for a voltage swing of 2.0 V is obtained without noticeable change of threshold. In addition, we demonstrate an on-chip electrothermal beam deflector integrated with a VCSEL. PMID:24663452

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Development of long-wavelength avalanche photodiodes and vertical-cavity lasers for epitaxial integration as a vertical-cavity photon number amplifier

    NASA Astrophysics Data System (ADS)

    Huntington, Andrew Sumika

    The goal of this research was to develop technology for building a vertical-geometry photon number amplifier (vertical PNA) that operates at a wavelength in the low-absorption window for optical fibers near 1.55 mum. An optical amplifier of this design would provide electrically-tappable low-noise polarization-independent optical amplification of laser pulses and serve as a stepping stone toward development of a tunable amplifying wavelength converter. The vertical PNA design consists of a multiple active region (MAR) VCSEL integrated with an avalanche photodiode of the separate absorption, charge, and multiplication layer design (SACM APD): the VCSEL is intended to operate continuous wave (CW), modulated by the APD. Both components were selected for their high gain: in excess of 10 electrons out per photon in for the APD, and slightly more than 1 photon out per electron in for the MAR VCSEL under ideal circumstances. In working toward the vertical PNA, significant technical challenges were addressed: (1) Development of a long-wavelength MAR VCSEL capable of high-temperature CW operation. Although this goal was never achieved, efforts directed to this end resulted in an investigation of basic material science issues that are vital to future improvements of the device. Better DBR and active region designs were developed, the overall thermal impedance of the structure was reduced significantly, a rudimentary optical aperture compatible with InP-based materials was tested, and loss estimates for the device were put on solid ground. (2) Development of a low-noise SACM APD capable of modulating the MAR VCSEL at high speed. Here the vital relationships between growth conditions, material quality, and APD performance were established. Other achievements include demonstration of highly uniform arrays of these devices, extremely low-noise operation, and the largest area long-wavelength APDs ever reported. (3) Successful demonstration of the epitaxial integration of these

  13. Frequency-induced polarization bistability in vertical-cavity surface-emitting lasers with orthogonal optical injection

    SciTech Connect

    Gatare, I.; Panajotov, K.; Sciamanna, M.

    2007-02-15

    We report theoretically on a pure frequency-induced polarization bistability in a vertical-cavity surface-emitting laser (VCSEL) subject to orthogonal optical injection, i.e., the master laser light polarization is orthogonal to that of the slave VCSEL. As the frequency detuning is scanned from negative to positive values and for a fixed injected power, the VCSEL exhibits two successive and possibly bistable polarization switchings. The first switching (from the slave laser polarization to the injected light polarization) exhibits a bistable region whose width is maximum for a given value of the injected power. Such a dependency of hysteresis width on the injected power is similar to that recently found experimentally by Hong et al.[Electron. Lett. 36, 2019 (2000)]. The bistability accompanying the second switching (from the injected light polarization back to the slave laser free-running polarization) exhibits, however, significantly different features related to the occurrence of optical chaos. Interestingly, the width of the bistable region can be tuned over a large range not only by modifying the injection parameters but also by modifying the device parameters, in particular the VCSEL linewidth enhancement factor.

  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. 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.

  16. Spectral dynamics of picosecond gain-switched pulses from nitride-based vertical-cavity surface-emitting lasers.

    PubMed

    Chen, Shaoqiang; Ito, Takashi; Asahara, Akifumi; Yoshita, Masahiro; Liu, Wenjie; Zhang, Jiangyong; Zhang, Baoping; Suemoto, Tohru; Akiyama, Hidefumi

    2014-01-01

    Short pulses generated from low-cost semiconductor lasers by a simple gain-switching technique have attracted enormous attention because of their potential usage in wide applications. Therein, reducing the durations of gain-switched pulses is a key technical point for promoting their applications. Therefore, understanding the dynamic characteristics of gain-switched pulses is highly desirable. Herein, we used streak camera to investigate the time- and spectral-resolved lasing characteristics of gain-switched pulses from optically pumped InGaN single-mode vertical-cavity surface-emitting lasers. We found that fast initial components with ultra-short durations far below our temporal resolution of 5.5 ps emerged on short-wavelength sides, while the entire pulses were down-chirped, resulting in the simultaneous broadening of the spectrum and pulse width. The measured chirp characteristics were quantitatively explained using a single-mode rate-equation model, combined with carrier-density-dependent gain and index models. The observed universal fast short-wavelength components can be useful in generating even shorter pulses from gain-switched semiconductor lasers. PMID:24710268

  17. Towards high-frequency operation of polarization oscillations in spin vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Lindemann, Markus; Höpfner, Henning; Gerhardt, Nils C.; Hofmann, Martin R.; Pusch, Tobias; Michalzik, Rainer

    2015-09-01

    Compared to purely charge based devices, spintronic lasers offer promising perspectives for new superior device concepts. Especially vertical-cavity surface-emitting lasers with spin-polarization (spin-VCSELs) feature ultrafast spin and polarization dynamics. Oscillations in the circular polarization degree can be generated using pulsed spin-injection. The oscillations evolve due to the carrier-spin-photon system that is coupled for the linear modes in the VCSEL's cavity via the birefringence. The polarization oscillations are independent of the conventional relaxation oscillations and have the potential to exceed frequencies of 100 GHz. The oscillations are switchable and can be the basis for ultrafast directly modulated spin-VCSELs for, e.g., communication purposes. The polarization oscillation frequency is mainly determined by the birefringence. We show a method to tune the birefringence and thus the polarization oscillation frequency by adding mechanical strain to the substrate in the vicinity of the laser. We achieved first experimental results for high-frequency operation using 850 nm oxide-confined single-mode VCSELs. The results are compared with simulations using the spin-flip-model for high birefringence values.

  18. Quasi-bichromatic laser for a lin⊥lin coherent population trapping clock produced by vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Yun, Peter; Tan, Bozhong; Deng, Wei; Yang, Jing; Gu, Sihong

    2012-09-01

    With two vertical-cavity surface-emitting lasers working under the master-slave sideband injection-locking configuration, we have realized a quasi-bichromatic laser beam with residual phase noise Δϕ2 < 0.282 rad2. The two wanted frequency components share more than 96% power of the beam. With the realized beam, we have carried out coherent population trapping (CPT) resonance experiment with 87Rb in the lin⊥lin CPT scheme, and recorded CPT resonance signal with contrast of 60%. Such laser system is promising to realize a lin⊥lin CPT clock with high performance and low power consumption.

  19. Low-speckle laser projection with a broad-area vertical-cavity surface-emitting laser in the nonmodal emission regime.

    PubMed

    Riechert, Falko; Craggs, Gordon; Meuret, Youri; Van Giel, Bart; Thienpont, Hugo; Lemmer, Uli; Verschaffelt, Guy

    2009-02-01

    We demonstrate low-speckle laser projection using a broad-area vertical-cavity surface-emitting laser (VCSEL) emitting at 840 nm wavelength as the illumination source. By driving the source in a nonmodal emission regime, we were able to achieve speckle contrast values as low as 3.5% in a realistic projection setup. This was done by driving the VCSEL with specific current pulses without using any additional or mechanically moving components to destroy the coherence of the laser beam. We quantitatively model the speckle contrast reduction based on polarization scrambling and the reduced temporal and spatial coherence of the VCSEL. PMID:19183610

  20. 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.

  1. Optical characterization of InGaN heterostructures for blue light emitters and vertical cavity lasers: Efficiency and recombination dynamics

    NASA Astrophysics Data System (ADS)

    Okur, Serdal

    ) suggesting a minimum limit for the active region thickness. Therefore, multiple relatively thin but still three dimensional InGaN active regions separated by thin and low barriers were found to be more efficient for InGaN light emitters. Investigations of electroluminescence from light emitting diodes (LEDs) incorporating multi DH InGaN active regions (e.g. quad 3 nm DH) and thick SEIs (two 20 nm-thick InGaN layers with step increase in In content) revealed higher emission intensities compared to LEDs with thinner or no SEI. This indicated that injected electrons were cooled sufficiently with thicker SEI layers and their overflow was greatly reduced resulting in efficient recombination in the active region. Among the structures considered to enhance the quantum efficiency, the multi-DH design with a sufficiently thick SEI layer constitutes a viable approach to achieve high efficiency also in blue lasers. Owing to its high exciton binding energy, GaN is one of the ideal candidates for microcavities exploiting the strong exciton-photon coupling to realize the mixed quasiparticles called polaritons and achieve ideally thresholdless polariton lasing at room temperature. Angle-resolved PL and cathodoluminescence measurements revealed large Rabi splitting values up to 75 meV indicative of the strong exciton-photon coupling regime in InGaN-based microcavities with bottom semiconductor AlN/GaN and a top dielectric SiO2/SiN x DBRs, which exhibited quality factors as high as 1300. Vertical cavity structures with all dielectric DBRs were also achieved by employing a novel ELO method that allowed integration of a high quality InGaN cavity active region with a dielectric bottom DBR without removal of the substrate while forming a current aperture through the ideally defect-free active region. The full-cavity structures formed as such were shown to exhibit clear cavity modes near 400 and 412 nm in the reflectivity spectrum and quality factors of 500. Although the polar c-plane orientation

  2. 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.

  3. Vertical-cavity surface-emitting laser (VCSEL) sources for frequency domain photon migration

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Thomas D.; No, Keun-Sik; Matlock, Alex; Hill, Brian; Cerussi, Albert E.; Tromberg, Bruce J.

    2015-03-01

    Frequency domain photon migration (FDPM) uses modulated laser light to measure the bulk optical properties of turbid media and is increasingly being applied for noninvasive functional medical imaging. Though semiconductor edge emitting laser diodes (EELs) have been traditionally used for this application, we show that VCSELs exhibit performance characteristics suitable for FDPM measurements of tissue optical properties. Their output power and modulation characteristics are more than sufficient for optical property recovery. In addition, their small size, high efficiency, low cost, and simple packaging make them an attractive choice as components in clinical FDPM systems. We demonstrate a unique, compact optical probe that was enabled by VCSEL technology.

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

    NASA Astrophysics Data System (ADS)

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

    2016-01-01

    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 θp. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θp. The maximum value of the cross-correlation coefficient achieved is -0.99 with a zero time delay over a wide range of θp beyond 65° with a poor synchronization dynamic at θp less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θp. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

  5. Polarization behavior of vertical-cavity surface-emitting lasers under the influence of in-plane anisotropic strain

    NASA Astrophysics Data System (ADS)

    Peeters, Michael; Panajotov, Krassimir P.; Verschaffelt, Guy; Nagler, Bob; Albert, Jan; Thienpont, Hugo; Veretennicoff, Irina P.; Danckaert, Jan

    2002-06-01

    It is well known that vertical-cavity surface-emitting lasers (VCSELs) can abruptly switch between two orthogonal linear polarization states if the current is changed. The impact of externally induced in-plane anisotropic strain on this switching was experimentally demonstrated in proton-implanted devices. In this contribution we present a further and thorough experimental investigation of the polarization behavior of different types of VCSELs (proton-implanted, air-post and oxide-confined), under varying strain conditions. We first measure the influence of the strain on the orientation of the axes of the linear polarization states. These axes can be rotated from the crystallographic direction [110] over [100] to [110]. At the same time, we monitor the exact birefringence. From the combination of these two measurements the amount of residual strain in these devices is deduced. Applying strain not only changes the frequency splitting between the two modes (due to birefringence) and their orientation, but also lifts the degeneracy in the gain of the polarization modes. We therefore also measure the gain difference (dichroism) as a function of the applied strain, via the mode suppression ratio and the optical spectrum. Due to the effect on both the birefringence and the dichroism, strain also changes the position of the polarization switching point as a function of current and can lead to the observation of double (consecutive) polarization switching. All this experimental evidence will help to build up a better understanding of the physics of polarization switching in VCSELs.

  6. Continuous sensing of tumor-targeted molecular probes with a vertical cavity surface emitting laser-based biosensor

    NASA Astrophysics Data System (ADS)

    Parashurama, Natesh; O'Sullivan, Thomas D.; De La Zerda, Adam; El Kalassi, Pascale; Cho, Seongjae; Liu, Hongguang; Teed, Robert; Levy, Hart; Rosenberg, Jarrett; Cheng, Zhen; Levi, Ofer; Harris, James S.; Gambhir, Sanjiv S.

    2012-11-01

    Molecular optical imaging is a widespread technique for interrogating molecular events in living subjects. However, current approaches preclude long-term, continuous measurements in awake, mobile subjects, a strategy crucial in several medical conditions. Consequently, we designed a novel, lightweight miniature biosensor for in vivo continuous optical sensing. The biosensor contains an enclosed vertical-cavity surface-emitting semiconductor laser and an adjacent pair of near-infrared optically filtered detectors. We employed two sensors (dual sensing) to simultaneously interrogate normal and diseased tumor sites. Having established the sensors are precise with phantom and in vivo studies, we performed dual, continuous sensing in tumor (human glioblastoma cells) bearing mice using the targeted molecular probe cRGD-Cy5.5, which targets αVβ3 cell surface integrins in both tumor neovasculature and tumor. The sensors capture the dynamic time-activity curve of the targeted molecular probe. The average tumor to background ratio after signal calibration for cRGD-Cy5.5 injection is approximately 2.43±0.95 at 1 h and 3.64±1.38 at 2 h (N=5 mice), consistent with data obtained with a cooled charge coupled device camera. We conclude that our novel, portable, precise biosensor can be used to evaluate both kinetics and steady state levels of molecular probes in various disease applications.

  7. Continuous sensing of tumor-targeted molecular probes with a vertical cavity surface emitting laser-based biosensor

    PubMed Central

    Parashurama, Natesh; O’Sullivan, Thomas D.; De La Zerda, Adam; El Kalassi, Pascale; Cho, Seongjae; Liu, Hongguang; Teed, Robert; Levy, Hart; Rosenberg, Jarrett; Cheng, Zhen; Levi, Ofer; Harris, James S.

    2012-01-01

    Abstract. Molecular optical imaging is a widespread technique for interrogating molecular events in living subjects. However, current approaches preclude long-term, continuous measurements in awake, mobile subjects, a strategy crucial in several medical conditions. Consequently, we designed a novel, lightweight miniature biosensor for in vivo continuous optical sensing. The biosensor contains an enclosed vertical-cavity surface-emitting semiconductor laser and an adjacent pair of near-infrared optically filtered detectors. We employed two sensors (dual sensing) to simultaneously interrogate normal and diseased tumor sites. Having established the sensors are precise with phantom and in vivo studies, we performed dual, continuous sensing in tumor (human glioblastoma cells) bearing mice using the targeted molecular probe cRGD-Cy5.5, which targets αVβ3 cell surface integrins in both tumor neovasculature and tumor. The sensors capture the dynamic time-activity curve of the targeted molecular probe. The average tumor to background ratio after signal calibration for cRGD-Cy5.5 injection is approximately 2.43±0.95 at 1 h and 3.64±1.38 at 2 h (N=5 mice), consistent with data obtained with a cooled charge coupled device camera. We conclude that our novel, portable, precise biosensor can be used to evaluate both kinetics and steady state levels of molecular probes in various disease applications. PMID:23123976

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

    PubMed

    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. PMID:26781492

  9. Upstream vertical cavity surface-emitting lasers for fault monitoring and localization in WDM passive optical networks

    NASA Astrophysics Data System (ADS)

    Wong, Elaine; Zhao, Xiaoxue; Chang-Hasnain, Connie J.

    2008-04-01

    As wavelength division multiplexed passive optical networks (WDM-PONs) are expected to be first deployed to transport high capacity services to business customers, real-time knowledge of fiber/device faults and the location of such faults will be a necessity to guarantee reliability. Nonetheless, the added benefit of implementing fault monitoring capability should only incur minimal cost associated with upgrades to the network. In this work, we propose and experimentally demonstrate a fault monitoring and localization scheme based on a highly-sensitive and potentially low-cost monitor in conjunction with vertical cavity surface-emitting lasers (VCSELs). The VCSELs are used as upstream transmitters in the WDM-PON. The proposed scheme benefits from the high reflectivity of the top distributed Bragg reflector (DBR) mirror of optical injection-locked (OIL) VCSELs to reflect monitoring channels back to the central office for monitoring. Characterization of the fault monitor demonstrates high sensitivity, low bandwidth requirements, and potentially low output power. The added advantage of the proposed fault monitoring scheme incurs only a 0.5 dB penalty on the upstream transmissions on the existing infrastructure.

  10. 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

  11. Harmonic distortion dependent on optical feedback, temperature and injection current in a vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

    2016-04-01

    In this paper, selective optical feedback is used to investigate the nonlinearity behaviours of a vertical cavity surface emitting laser (VCSEL) with the modulation signal. A single mode VCSEL with both parallel and orthogonal optical feedback (OF) signals modulated at 1 MHz frequency over a range of modulation depth is investigated. We also investigate the nonlinear characteristics of the orthogonal polarization modes XP and YP of the VCSEL by changing the injection current and temperature. The results show an enhancement in the harmonic distortions (HDs) of both XP and YP modes with parallel OF, and the total suppression of HDs with orthogonal OF. We show that for the VCSEL with orthogonal OF, the second and third harmonic components of the XP and YP modes decrease and reach the noise floor level of the output power spectrum. Additionally, peaks of second and third harmonic components change radically when varying the bias current and temperature. The results reveal that orthogonal OF can be employed as a new tool to improve the linear dynamic range and to control the nonlinear characteristics of the VCSEL, thus making these devices a promising optical source in present and future optical communication applications.

  12. 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.

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

    PubMed Central

    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. PMID:26781492

  14. 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. PMID:20648149

  15. Power scaling and beam divergence compression of bottom-emitting vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Zhang, Xing; Ning, Yongqiang; Zhang, Jianwei; Zhang, Jian; Zhang, Jinsheng; Jia, Peng; Li, Xiushan; Shi, Jingjing; Qin, Li; Liu, Yun; Tong, Cunzhu; Wang, Lijun

    2013-09-01

    Power scaling and beam divergence compression of 980 nm bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) are presented in this paper. First, the relationships among the reflectivity of the n-doped distributed Bragg reflector, threshold current, and output power were analyzed, and the n-DBR reflectivity was optimized to achieve higher slope efficiency in a relatively low threshold current. Second, the influence of the p-contact on the current density distribution inside the active region was analyzed using the three-dimensional finite-element method. Uniform current distribution was achieved by optimizing the diameter of the p-contact, and a consequent improvement in beam divergence was observed. A low divergence of 5.4° was obtained for a single device with continuous-wave (CW) of 1.46 W at room temperature. The 8×8 VCSEL array showed a divergence angle of 10.2° at 4A. This array afforded a CW output power of 1.95 W under an injected current of 4 A and a pulse output power of 115 W under a pulse drive current of 130 A, a pulse width of 100 ns, and a repetition frequency of 100 Hz. VCSEL array chips were packaged in series to form a "quasi-array" to further increase the output power. This series achieved a peak output power of 475 W under a pulse drive current of 120 A.

  16. 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.

  17. Coherent polarization stabilization in large-aperture rectangular post bottom-emitting vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Wang, W.; Ning, Y. Q.; Tian, Z. H.; Zhang, X.; Shi, J. J.; Wang, Z. F.; Zhang, L. S.; Zhang, Y.; Liu, Y.; Qin, L.; Wang, L. J.

    2011-03-01

    The output characteristics of large-aperture rectangular post bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) were investigated. It was shown that the output power of the rectangle VCSELs can be up to 660 mW at a current of 5 A. Both H-polarization (horizontal) and V-polarization (vertical) demonstrated a coherent stabilization over the entire range of operation current, and coherent spectrum blue-shift of H-polarization light occurred with respect to V-polarization light at three different injected currents. The polarization states of output light were stabilized in the two orthogonal directions and H-polarization was the most principal polarization which was parallel to the longer side of the rectangular aperture. From the relationship between polarization ratio and aspect ratio of the oxidation confinement aperture (OCA), it was found that the highest polarization ratio (about 2:1) took place when the appropriate aspect ratio was 5:3, which meant better polarization stabilization in large-aperture VCSELs.

  18. 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.

  19. Phonon-assisted stimulated emission and ultra-thin active layers in cleaved-cavity and vertical-cavity surface emitting lasers

    SciTech Connect

    Benjamin, S.D.

    1991-01-01

    Unique lasing processes in III-V semiconductor lasers are examined. The dynamics of stimulated photon emissions in thin AlGaAs/GaAs single quantum well lasers are observed experimentally and modeled by rate equations describing the electron and photon densities. Agreement between experiment and theory are achieved when the transition probability matrix, calculated with the spreading out of electron and hole wave functions taken into account, is used. The phonon assisted stimulated photon emission observed in this work is delayed with respect to the unassisted emission. This observation is modeled by using a weaker matrix element for the unassisted process which is expected from theory and thus supports the author' claim that this emission is phonon assisted. Rate equations developed to simulate doubly stimulated emission of photons and phonons do not describe the experimental data so the possibility of stimulated phonon emission is ruled out for the samples studied in this work. Vertical Cavity Surface Emitting Lasers are also studied since they can be designed to support unique lasing processes. The design and growth of vertical cavity surface emitting lasers are discussed and these concepts are applied to the realization of a vertical cavity surface emitting laser with the thinnest active layer of any laser yet reported. Stimulated emission supported across the sub-monolayer thick InAs single quantum well active region can be understood by considering the spreading of the electron and hole wavefunctions beyond the confines of the quantum well to increase the length of the effective gain region.

  20. Record low-threshold index-guided InGaAs/GaAlAs vertical-cavity surface-emitting laser with a native oxide confinement structure

    NASA Astrophysics Data System (ADS)

    Hayashi, Y.; Mukaihara, T.; Hatori, N.; Ohnoki, N.; Matsutani, A.; Koyama, F.; Iga, K.

    1995-03-01

    An index-guided InGaAs/GaAlAs vertical-cavity surface-emitting laser with a native oxide confinement structure has been proposed and fabricated. A record threshold current of 70 micro A was achieved with a 5 micron-diameter core device. The proposed structure provides strong electrical and optical confinements. Also a reduction in nonradiative recombination and an improvement in the thermal resistance can be expected.

  1. Polarization mode structure in long-wavelength wafer-fused vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Volet, N.; Iakovlev, V.; Sirbu, A.; Caliman, A.; Suruceanu, G.; Mereuta, A.; Kapon, E.

    2012-06-01

    Applications of long-wavelength (λ > 1 μm) vertical-cavity surface-emitting lasers (VCSELs) generally require close control over wavelength and polarization of the emitted light. In most cases, single mode and polarization stable lasing is desired. We report here on the detailed modal analysis of wafer-fused 1550-nm wavelength VCSELs incorporating an AlGaInAs/InP active region, a re-grown circular tunnel junction (TJ) and undoped AlGaAs/GaAs distributed Bragg reflectors (DBRs). We experimentally determined the diameter of the TJ that optimizes the output power and threshold current, finding a value between 7.0 μm and 9.5 μm depending on the temperature. Moreover, we investigated the impact of the TJ aperture diameter on the mode structure. A large batch of devices was investigated, allowing drawing conclusions on typical behavior of these devices. The measured emission spectra show that the fundamental spatial mode is split into two orthogonal polarization modes, which are spectrally separated in wavelength by δ, used as a birefringence parameter. We observed that this parameter is independent of current but depends on the particular chip, suggesting that it is caused by stress, growth inhomogeneities, or etched mesa shape. The higher order spatial modes show similar polarization doublets with a splitting also equal to δ. This suggests that the birefringence results from effects not particular to the mechanism of mode confinement. Finally, the spectral separation Δ01 between the fundamental mode and the first-order transverse mode increases linearly with current, with a slope that depends only on the TJ aperture diameter. This confirms that the mode confinement is induced by the structured TJ, and possibly also by the temperature distribution induced by the current injection.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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/cm2 (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 (LP12,1), 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. Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We report on the lasing of III-nitride nonpolar, violet, vertical-cavity surface-emitting lasers (VCSELs) with IIInitride tunnel-junction (TJ) intracavity contacts and ion implanted apertures (IIAs). The TJ VCSELs are compared to similar VCSELs with tin-doped indium oxide (ITO) intracavity contacts. Prior to analyzing device results, we consider the relative advantages of III-nitride TJs for blue and green emitting VCSELs. The TJs are shown to be most advantageous for violet and UV VCSELs, operating near or above the absorption edge for ITO, as they significantly reduce the total internal loss in the cavity. However, for longer wavelength III-nitride VCSELs, TJs primarily offer the advantage of improved cavity design flexibility, allowing one to make the p-side thicker using a thick n-type III-nitride TJ intracavity contact. This offers improved lateral current spreading and lower loss, compare to using ITO and p-GaN, respectively. These aspects are particularly important for achieving high-power CW VCSELs, making TJs the ideal intracavity contact for any III-nitride VCSEL. A brief overview of III-nitride TJ growth methods is also given, highlighting the molecular-beam epitaxy (MBE) technique used here. Following this overview, we compare 12 μm aperture diameter, violet emitting, TJ and ITO VCSEL experimental results, which demonstrate the significant improvement in differential efficiency and peak power resulting from the reduced loss in the TJ design. Specifically, the TJ VCSEL shows a peak power of ~550 μW with a threshold current density of ~3.5 kA/cm2, while the ITO VCSELs show peak powers of ~80 μW and threshold current densities of ~7 kA/cm2.

  4. 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.

  5. 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.

  6. High-power temperature-insensitive gain-offset InGaAs/GaAs vertical-cavity surface-emitting lasers

    SciTech Connect

    Young, D.B.; Scott, J.W.; Peters, F.H.; Thibeault, B.J.; Corzine, S.W.; Peters, M.G.; Lee, S.L.; Coldren, L.A. )

    1993-02-01

    The authors have grown 997 nm vertical-cavity surface-emitting lasers with an offset between the wavelength of the cavity mode and the quantum well gain peak to improve high temperature operation, and with higher aluminum-content barriers around the active region to improve the carrier confinement. They fabricated lasers of 8-15 and 20 [mu]m diameters. The 8[mu]m diameter devices exhibited CW operation up to 140 C with little change in threshold current from 15 C, and the 20[mu]m diameter devices showed CW output power of 11 mW at 25 C without significant heat-sinking.

  7. GaSb-based vertical-cavity surface-emitting lasers with an emission wavelength at 3 μm.

    PubMed

    Andrejew, Alexander; Sprengel, Stephan; Amann, Markus-Christian

    2016-06-15

    GaSb-based electrically pumped vertical-cavity surface-emitting lasers (VCSELs) with a buried tunnel junction emitting at 3 μm are demonstrated. To achieve this, a low optical loss VCSEL concept with an undoped epitaxial distributed Bragg reflector and intracavity contact is presented. The devices operate up to 5°C continuous wave and up to 50°C in pulsed mode. Single-mode operation with a side-mode suppression ratio of 30 dB and electro-thermal tuning range of 19.7 nm is achieved. PMID:27304292

  8. Continuous wave operation of high power GaN-based blue vertical-cavity surface-emitting lasers using epitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We have succeeded in achieving continuous-wave operation of gallium nitride (GaN) based vertical-cavity surfaceemitting lasers (VCSELs), which was fabricated by epitaxial lateral overgrowth (ELO) using dielectric distributed Bragg reflectors(DBRs) as masks for selective growth. The device exhibited CW operation at a wavelength of 453.9nm. The maximum output power was 1.1 mW, which is the highest value reported in previously published articles. The ELO process used for this study represents a breakthrough for challenges which were indicated by other former reports for GaN-based VCSELs and is suitable for mass production.

  9. Temperature dependence of spontaneous switch-on and switch-off of laser cavity solitons in vertical-cavity surface-emitting lasers with frequency-selective feedback

    NASA Astrophysics Data System (ADS)

    Jimenez, J.; Oppo, G.-L.; Ackemann, T.

    2016-03-01

    A systematic experimental and numerical investigation of the conditions for the spontaneous formation of laser cavity solitons in broad-area vertical-cavity surface-emitting lasers with frequency-selective feedback by a volume Bragg grating is reported. It is shown that the switching thresholds are controlled by a combination of frequency shifts induced by ambient temperature and Joule heating. The gain level has only a minor influence on the threshold but controls mainly the power of the solitons. At large initial detuning and high threshold gain, the first observed structure can be a high order soliton. In real devices spatial disorder in the cavity length causes a pinning of solitons and a dispersion of thresholds. The experimental observations are in good agreement with numerical simulations taking into account disorder and the coupling of gain and cavity resonance due to Joule heating. In particular, we demonstrate that the existence of the traps explain the spontaneous switch on of the solitons, but do not modify the soliton shape significantly, i.e. the observed solitons are a good approximation of the ones expected in a homogeneous system.

  10. Low threshold continuous-wave lasing of yellow-green InGaN-QD vertical-cavity surface-emitting lasers.

    PubMed

    Weng, Guoen; Mei, Yang; Liu, Jianping; Hofmann, Werner; Ying, Leiying; Zhang, Jiangyong; Bu, Yikun; Li, Zengcheng; Yang, Hui; Zhang, Baoping

    2016-07-11

    Low threshold continuous-wave (CW) lasing of current injected InGaN quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs) was achieved at room temperature. The VCSEL was fabricated by metal bonding technique on a copper substrate to improve the heat dissipation ability of the device. For the first time, lasing was obtained at yellow-green wavelength of 560.4 nm with a low threshold of 0.61 mA, corresponding to a current density of 0.78 kA/cm2. A high degree of polarization of 94% were measured. Despite the operation in the range of "green gap" of GaN-based devices, single longitudinal mode laser emission was clearly achieved due to the high quality of active region based on InGaN QDs and the excellent thermal design of the VCSELs. PMID:27410828

  11. Characterization of 2.3 μm GaInAsSb-based vertical-cavity surface-emitting laser structures using photo-modulated reflectance

    SciTech Connect

    Chai, G. M. T.; Hosea, T. J. C.; Fox, N. E.; Hild, K.; Ikyo, A. B.; Marko, I. P.; Sweeney, S. J.; Bachmann, A.; Arafin, S.; Amann, M.-C.

    2014-01-07

    We report angle dependent and temperature dependent (9 K–300 K) photo-modulated reflectance (PR) studies on vertical-cavity surface-emitting laser (VCSEL) structures, designed for 2.3 μm mid-infrared gas sensing applications. Changing the temperature allows us to tune the energies of the quantum well (QW) transitions relative to the VCSEL cavity mode (CM) energy. These studies show that this VCSEL structure has a QW-CM offset of 21 meV at room temperature. Consequently the QW ground-state transition comes into resonance with the CM at 220 ± 2 K. The results from these PR studies are closely compared with those obtained in a separate study of actual operating devices and show how the PR technique may be useful for device optimisation without the necessity of having first to process the wafers into working devices.

  12. High-differential-quantum-efficiency, long-wavelength vertical-cavity lasers using five-stage bipolar-cascade active regions

    SciTech Connect

    Koda, R.; Wang, C.S.; Lofgreen, D.D.; Coldren, L.A.

    2005-05-23

    We present five-stage bipolar-cascade vertical-cavity surface-emitting lasers emitting at 1.54 {mu}m grown monolithically on an InP substrate by molecular beam epitaxy. A differential quantum efficiency of 120%, was measured with a threshold current density of 767 A/cm{sup 2} and voltage of 4.49 V, only 0.5 V larger than 5x0.8 V, the aggregate photon energy. Diffraction loss study on deeply etched pillars indicates that diffraction loss is a major loss mechanism for such multiple-active region devices larger than 20 {mu}m. We also report a model on the relationship of diffraction loss to the number of active stages.

  13. 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. PMID:26193547

  14. Long wavelength (1.3 {mu}m) vertical-cavity surface-emitting lasers with a wafer-bonded mirror and an oxygen-implanted confinement region

    SciTech Connect

    Qian, Y.; Zhu, Z.H.; Lo, Y.H.; Huffaker, D.L.; Deppe, D.G.; Hou, H.Q.; Hammons, B.E.; Lin, W.; Tu, Y.K.

    1997-07-01

    We proposed and demonstrated a novel design for long wavelength (1.3 {mu}m) vertical-cavity surface-emitting lasers (VCSELs). In this design, oxygen-implanted current-confinement regions were formed in a GaAs/AlGaAs Bragg reflector which is the bottom mirror wafer bonded to an AlGaInAs/InP cavity consisting of nine strain-compensated quantum wells. Room- temperature continuous-wave (cw) operation of 1.3 {mu}m-VCSELs with a record low cw threshold current density of 1.57kA/cm{sup 2} and a record low cw threshold current of 1 mA have been realized. {copyright} {ital 1997 American Institute of Physics.}

  15. Lasing-Polarization-Dependent Output from Orthogonal Waveguides in High-Index-Contrast Subwavelength Grating Vertical-Cavity Surface-Emitting Laser

    NASA Astrophysics Data System (ADS)

    Tsunemi, Yoshihiro; Ikeda, Kazuhiro; Kawaguchi, Hitoshi

    2013-09-01

    We propose a high-index-contrast subwavelength grating vertical-cavity surface-emitting laser (HCG-VCSEL) incorporating a polarization-independent HCG coupled with two orthogonal in-plane output waveguides and numerically investigate the optical output characteristics from the waveguides using a three-dimensional finite-difference time-domain method. The light coupled more strongly to the waveguide in the direction perpendicular to the polarization of the resonant mode than to that in the parallel direction. The extinction ratio between the waveguides was 11.9, indicating that the output waveguide can be switched by changing the lasing polarization. The propagating modes in the strongly and weakly coupled waveguides were the TE and TM modes, respectively.

  16. Efficient double intracavity-contacted vertical-cavity surface-emitting lasers with very low-threshold and low-power dissipation designed for cryogenic applications

    SciTech Connect

    Yang, K.; Hains, C.P.; Cheng, J.; Allerman, A.A.

    2000-02-01

    Efficient continuous wave operation of oxide-confined double intracavity-contacted InGaAs-GaAs vertical-cavity surface-emitting lasers (VCSEL's) with low-threshold voltage, low-threshold current and low-power dissipation has been achieved over a wide range of cryogenic temperatures (77 K--250 K). Low operating voltages were obtained by routing current through two intracavity contacts to bypass both distributed Bragg reflector (DBR) mirrors, while lower optical losses were achieved by using undoped DBR mirrors with abrupt heterointerfaces. This resulted in low operating voltages (<1.5 V), submillampere threshold currents (I{sub th} {approximately} 0.15 mA), low-power dissipation ({approximately} 0.21 mW at threshold) and a high power conversion efficiency ({eta}{sub eff} = 31%).

  17. 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.

  18. 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.

  19. 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

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

    PubMed

    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

  1. Blue vertical-cavity surface-emitting lasers based on second-harmonic generation grown on (311)B and (411)A GaAs substrates

    NASA Astrophysics Data System (ADS)

    Kaneko, Yasuhisa; Nakagawa, Shigeru; Ichimura, Yoshikatsu; Yamada, Norihide; Mars, Dan E.; Takeuchi, Tetsuya

    2000-02-01

    We have studied blue vertical-cavity surface-emitting lasers (VCSELs) based on second-harmonic generation (SHG) grown on (411)A and (311)B GaAs substrates in order to investigate suitable substrate orientations for SHG-VCSELs. The comparison among substrate orientations has been made on three parameters, SHG conversion efficiency, transparency current density and gain coefficient. The transparency current density and the gain coefficient are characterized by edge emitting lasers grown on the above substrates. We also discuss the transparency current density and the gain coefficient for (311)A reported previously by Takahashi et al. [M. Takahashi, M. Hirai, K. Fujita, N. Egami, and K. Iga, J. Appl. Phys. 82, 4551 (1997)]. SHG conversion efficiency is 38 and 30% W for SHG-VCSELs grown on (311)B and (411)A substrates, respectively, which is consistent with theory, assuming identical nonlinear coefficients for the A face and B face. Transparency current density for (311)A, (311)B and (411)A is 80, 105 and 60 A/cm2, and gain coefficients for (311)A, (311)B and (411)A are 20, 13 and 18 cm-1, respectively. There are no significant differences between (311)A and (411)A, while those for (311)B are less than those for (311)A. In conclusion, SHG efficiency is dependent on crystal orientation consistent with theory and thus the (311) orientation is preferable. Optical gain is independent of substrate orientation, while it is dependent on substrate face and A face is preferable.

  2. Single-mode vertical-cavity surface emitting lasers for {sup 87}Rb-based chip-scale atomic clock

    SciTech Connect

    Derebezov, I. A. Haisler, V. A.; Bakarov, A. K.; Kalagin, A. K.; Toropov, A. I.; Kachanova, M. M.; Gavrilova, T. A.; Semenova, O. I.; Tretyakov, D. B.; Beterov, I. I.; Entin, V. M.; Ryabtsev, I. I.

    2010-11-15

    The results of numerical simulation and study of lasing characteristics of semiconductor verticalcavity surface-emitting lasers based on Al{sub x}Ga{sub 1-x}As alloys are presented. Lasers exhibit stable single-mode lasing at a wavelength of 795 nm at low operating currents {approx}1.5 mA and an output power of 350 {mu}W, which offers prospects of their applications in next-generation chip-scale atomic clocks

  3. Mechanically tunable organic vertical-cavity surface emitting lasers (VCSELs) for highly sensitive stress probing in dual-modes.

    PubMed

    Yang, Yu; Zhou, Yuan; Liao, Zhifu; Yu, Jiancan; Cui, Yuanjing; Garcia-Moreno, Inmaculada; Wang, Zhiyu; Costela, Angel; Qian, Guodong

    2015-02-23

    Herein, we report a straight forward stress probing method based on mechanically tunable organic VCSELs via dual detecting-modes. By designing the active layer thickness, uploaded stress was measured simultaneously by the laser wavelength and mode separations, facilitating highly sensitive stress detection in broad ranges. Single-mode laser emission with low threshold and narrow line-width was characterized, which could be tuned continuously within 8 nm. The probing sensitivity and resolution were estimated to be 60 Pa and 5.6 nm/KPa respectively, which were ~160-folds higher than previous results. PMID:25836475

  4. 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.

  5. Fabrication and alignment of large sapphire microlenses for use in electrically-injected GaN-based vertical-cavity laser applications

    NASA Astrophysics Data System (ADS)

    Farrell, Robert; Feezell, Daniel; Ishida, Masahiro; Newman, Scott; Cohen, Daniel; Nakamura, Shuji

    2007-03-01

    We have fabricated large sapphire microlenses for use in electrically-injected GaN-based vertical-cavity surface-emitting laser (VCSEL) applications. Thermally reflown photoresist microlenses are used as sacrificial masks for a BCl3/Cl2-based dry etch of sapphire. Sapphire microlenses with base diameters ranging from 10-250 μm and radii of curvature (ROC) ranging from 50-2000 μm are created by varying the initial thickness and diameter of the photoresist mask. Typical rms surface roughnesses of 1.5 å over 5.0 μm x 5.0 μm scan areas are achieved by utilizing specialized post-etch cleaning techniques. By coating the sapphire microlenses with dielectric distributed Bragg reflectors (DBRs) and aligning them to current apertures on InGaN-based devices on the opposite side of the sapphire wafer, we have demonstrated a viable technique for making high-reflectivity concave micromirrors for use in electrically-injected GaN-based VCSELs.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 (Jth) of ˜3.5 kA/cm2, compared to the ITO VCSEL Jth of 8 kA/cm2. 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.

  8. 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.

  9. 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.

  10. Accelerated aging of 28 Gb s-1 850 nm vertical-cavity surface-emitting laser with multiple thick oxide apertures

    NASA Astrophysics Data System (ADS)

    Kropp, J. R.; Steinle, G.; Schäfer, G.; Shchukin, V. A.; Ledentsov, N. N.; Turkiewicz, J. P.; Zoldak, M.

    2015-04-01

    850 nm vertical-cavity surface-emitting lasers with multiple thick oxide apertures suitable for temperature-insensitive error free transmission at 28 Gb s-1 are subjected to accelerated aging at high current densities and chip temperatures. The devices withstand a 20% power change test at a high current density (18 kA c{{m}-2}) at an ambient temperature of 120 {}^\\circ C for 2500 h. At 90-95 {}^\\circ C at this current density no degradation was observed up to 5000 h. We performed the studies at further elevated current densities and temperatures and define the acceleration factor as AF={{({{J}stress}/{{J}use})}8}exp [(1.3 eV/{{k}B})(1/{{T}use}-1/{{T}stress})]. The extrapolated lifetime for 20% power drop is estimated as 20 thousand years at 300 K at current density of 18 kA c{{m}-2} which is sufficient for 28 Gb s-1 error-free temperature-insensitive data transmission.

  11. Improved single-mode emission characteristics of long-wavelength wafer-fused vertical-cavity surface-emitting lasers by intra-cavity patterning

    NASA Astrophysics Data System (ADS)

    Volet, Nicolas; Czyszanowski, Tomasz; Walczak, Jarosław; Mutter, Lukas; Dwir, Benjamin; Micković, Zlatko; Gallo, Pascal; Iakovlev, Vladimir; Sirbu, Alexei; Caliman, Andrei; Mereuta, Alexandru; Kapon, Elyahou

    2013-03-01

    We report on transverse mode discrimination in long-wavelength wafer-fused vertical-cavity surface-emitting lasers (VCSELs) incorporating ring-shaped air gap patterns at the fused interface between the active region and the top distributed Bragg reflector (DBR). These 60-nm deep patterns were implemented with the aim of favoring the fundamental mode while preserving high output power. The VCSELs under consideration emit in the 1310-nm band and incorporate an AlGaInAs-based quantum well active region, a regrown circular tunnel junction and undoped GaAs/AlGaAs DBRs. A large batch of devices with varying pattern dimensions was investigated by on-wafer mapping, allowing significant statistical analysis leading to conclusions on their typical behavior. We observe experimentally a dependence of the side-mode suppression ratio on the geometrical parameters of the patterns. In particular, we identified a design that statistically increases the maximal single-mode emitted power by more than 20%. Numerical simulations of the patterned-cavity VCSELs based on our fully three dimensional electrical, thermal and optical VCSEL computational model support these observations. They show that patterns with a large inner diameter actually confine the first-order transverse mode and enhance its modal gain. In smaller devices, this mode is pushed out of the optical aperture and suffers larger losses. Optimized parameters were found numerically for enhancing the single-mode properties of the devices with negligible penalty on emitted power and threshold current.

  12. Nano-polymer-dispersed liquid crystal as phase modulator for a tunable vertical-cavity surface-emitting laser at 1.55 mum.

    PubMed

    Levallois, C; Caillaud, B; de Bougrenet de la Tocnaye, J-L; Dupont, L; Lecorre, A; Folliot, H; Dehaese, O; Loualiche, S

    2006-11-20

    We demonstrate what we believe is the first nonmechanical tunable vertical-cavity surface-emitting laser operating in the C band. This was achieved as a result of the combination of an InGaAs quantum well structure with a 6lambda thickness tunable index nano-polymer-dispersed liquid-crystal material. Experimental results exhibited a potential tunable range close to 10 nm, in the preliminary version, and excellent single mode locking due to the side-mode suppression ratio (more than 20 dB) over the whole spectral range. Another decisive advantage, compared to mechanical solutions, was the tuning response time of a few tens of microseconds (>30 micros) to scan the full spectral range (10 nm), making this device appropriate for some access network functions, as well as being robust and low cost. The voltage values are the main limitation to wavelength range extension. We present a first version of the device optically pumped. The next version will be electrically pumped as required for the access network applications targeted here. PMID:17086259

  13. Room-temperature CW operation of a nitride-based vertical-cavity surface-emitting laser using thick GaInN quantum wells

    NASA Astrophysics Data System (ADS)

    Furuta, Takashi; Matsui, Kenjo; Horikawa, Kosuke; Ikeyama, Kazuki; Kozuka, Yugo; Yoshida, Shotaro; Akagi, Takanobu; Takeuchi, Tetsuya; Kamiyama, Satoshi; Iwaya, Motoaki; Akasaki, Isamu

    2016-05-01

    We demonstrated a room-temperature (RT) continuous-wave (CW) operation of a GaN-based vertical-cavity surface-emitting laser (VCSEL) using a thick GaInN quantum well (QW) active region and an AlInN/GaN distributed Bragg reflector. We first investigated the following two characteristics of a 6 nm GaInN 5 QWs active region in light-emitting diode (LED) structures. The light output power at a high current density (∼10 kA/cm2) from the 6 nm GaInN 5 QWs was the same or even higher than that from standard 3 nm 5 QWs. In addition, we found that hole injection into the farthest QW from a p-layer was sufficient. We then demonstrated a GaN-based VCSEL with the 6 nm 5 QWs, resulting in the optical confinement factor of 3.5%. The threshold current density under CW operation at RT was 7.5 kA/cm2 with a narrow (0.4 nm) emission spectrum of 413.5 nm peak wavelength.

  14. 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.

  15. Smooth e-beam-deposited tin-doped indium oxide for III-nitride vertical-cavity surface-emitting laser intracavity contacts

    NASA Astrophysics Data System (ADS)

    Leonard, J. T.; Cohen, D. A.; Yonkee, B. P.; Farrell, R. M.; DenBaars, S. P.; Speck, J. S.; Nakamura, S.

    2015-10-01

    We carried out a series of simulations analyzing the dependence of mirror reflectance, threshold current density, and differential efficiency on the scattering loss caused by the roughness of tin-doped indium oxide (ITO) intracavity contacts for 405 nm flip-chip III-nitride vertical-cavity surface-emitting lasers (VCSELs). From these results, we determined that the ITO root-mean-square (RMS) roughness should be <1 nm to minimize scattering losses in VCSELs. Motivated by this requirement, we investigated the surface morphology and optoelectronic properties of electron-beam (e-beam) evaporated ITO films, as a function of substrate temperature and oxygen flow and pressure. The transparency and conductivity were seen to increase with increasing temperature. Decreasing the oxygen flow and pressure resulted in an increase in the transparency and resistivity. Neither the temperature, nor oxygen flow and pressure series on single-layer ITO films resulted in highly transparent and conductive films with <1 nm RMS roughness. To achieve <1 nm RMS roughness with good optoelectronic properties, a multi-layer ITO film was developed, utilizing a two-step temperature scheme. The optimized multi-layer ITO films had an RMS roughness of <1 nm, along with a high transparency (˜90% at 405 nm) and low resistivity (˜2 × 10-4 Ω-cm). This multi-layer ITO e-beam deposition technique is expected to prevent p-GaN plasma damage, typically observed in sputtered ITO films on p-GaN, while simultaneously reducing the threshold current density and increasing the differential efficiency of III-nitride VCSELs.

  16. Thermal oxidation rates of Al(x)Ga(1-x)As in H(2)O vapor and oxide-defined vertical cavity surface emitting laser characteristics

    NASA Astrophysics Data System (ADS)

    Ochiai, Mari

    The incorporation of oxides into semiconductor structures formed by the thermal oxidation of Alsb{x}Gasb{1-x}As in water vapor has resulted in a marked improvement in device performance. Vertical cavity surface emitting lasers (VCSEL's), in particular, have benefited from this technology, demonstrating record operating characteristics. This study focuses on the following areas with respect to oxide defined VCSEL's: the establishment of rate laws for the lateral oxidation of AlAs, the fabrication of VCSEL's, and the characterization of VCSEL's designed for high speed operation. An oxidation rate study was conducted on structures with AlAs oxidation layers. At low temperatures and short oxidation times, oxidation was found to be reaction rate limited. Conversely, diffusion across the oxide was determined to be the rate limiting mechanism at high temperature or long oxidation times. The observed rates can be modeled by rate equations by which the two component mechanisms can be separated. An activation energy of 1.6 eV and 0.8 eV was determined for the reaction and diffusion limited mechanism, respectively. A reduction in oxidation rates was observed with decreasing oxidation layer thickness and increasing doping concentration. The thickness dependence can be incorporated into the rate equations by assuming an oxidation reaction rate which is inhibited by the presence of strain in thin layers. The reaction rate can be characterized by a threshold thickness for which a value of 20 nm was determined for Alsb{x}Gasb{1-x}As. Oxide defined GaAs VCSEL's varying in size and oxidation layer composition were fabricated. Threshold currents of 450 muA and external differential quantum efficiencies of 0.5 were obtained. Finally, the large signal modulation characteristics of oxide defined VCSEL's were investigated. A threshold carrier lifetime of 1.6 nanoseconds VCSEL's was determined from laser turn-on delay measurements. The laser turn-on delay was also measured under various

  17. On-Chip High-Resolution Beam Scanner Based on Bragg Reflector Slow-Light Waveguide Amplifier and Tunable Micro-Electro-Mechanical System Vertical Cavity Surface Emitting Laser

    NASA Astrophysics Data System (ADS)

    Nakahama, Masanori; Gu, Xiaodong; Shimada, Toshikazu; Koyama, Fumio

    2012-04-01

    We propose a monolithic beam scanner consisting of a Bragg reflector slow-light waveguide amplifier and a tunable micro-electro-mechanical vertical cavity surface emitting laser. Continuous beam steering of over 30° and a narrow divergence angle of below 0.1° are predicted, which gives us a number of resolution points over 300. In addition, the modeling on saturation characteristics of a slow light amplifier shows a possibility of the maximum output power of over 10 mW.

  18. 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.

  19. The use of spatially ordered arrays of etched holes for fabrication of single-mode vertical-cavity surface-emitting lasers based on submonolayer InGaAs quantum dots

    SciTech Connect

    Kuzmenkov, A. G. Blokhin, S. A.; Maleev, N. A.; Sakharov, A. V.; Tikhomirov, V. G.; Maksimov, M. V.; Ustinov, V. M.; Kovsh, A. R.; Mikhrin, S. S.; Ledentsov, N. N.; Yang, H. P. D.; Lin, G.; Hsiao, R. S.; Chi, J. Y.

    2007-10-15

    To suppress the generation of high-order modes in vertical-cavity surface-emitting lasers based on submonolayer InGaAs quantum dots, the method of formation of a spatially ordered array of etched holes in the upper distributed Bragg reflector was used. Single-mode vertical-cavity surface-emitting lasers for spectral region of 990 nm with current-aperture diameter of 20 {mu}m, threshold current 0.9 mA, and maximum output power 3.8 mW at room temperature were demonstrated. Single-mode lasing with the coefficient of side-mode suppression in excess of 35 dB is retained in the entire range of pump currents. A decrease in the current oxide aperture to sizes that are close to those of the optical aperture brings about an increase in the external quantum efficiency; however, in this case, the transition to the multimode of lasing is observed at high pump currents.

  20. 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.

  1. 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.

  2. 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.

  3. Anomalous lasing of high-speed 850 nm InGaAlAs oxide-confined vertical-cavity surface-emitting lasers with a large negative gain-to-cavity wavelength detuning

    SciTech Connect

    Blokhin, S. A. Bobrov, M. A.; Maleev, N. A.; Sakharov, A. V.; Ustinov, V. M.; Kuzmenkov, A. G.; Blokhin, A. A.; Moser, P.; Lott, J. A.; Bimberg, D.

    2014-08-11

    The impact of a large negative quantum well gain-to-cavity etalon wavelength detuning on the static and dynamic characteristics of 850 nm InGaAlAs high-speed oxide-confined vertical-cavity surface-emitting lasers (VCSELs) was investigated. Three distinct lasing regimes were revealed in large square aperture (≥7 μm per side) devices with large detuning including: (1) an anomalous lasing via higher order Hermite–Gaussian modes at low forward bias current; (2) lasing via the lowest order Hermite–Gaussian modes at high bias current; and (3) simultaneous lasing via both types of transverse modes at intermediate bias currents. In contrast to conventional multimode VCSELs a two-resonance modulation response was observed for the case of co-lasing via multiple transverse modes with high spectral separation. The reduction in the oxide aperture area resulted in classical lasing via the lowest order modes with a conventional single-resonance frequency response.

  4. Short-wavelength infrared imaging using low dark current InGaAs detector arrays and vertical-cavity surface-emitting laser illuminators

    NASA Astrophysics Data System (ADS)

    Macdougal, Michael; Geske, Jon; Wang, Chad; Follman, David

    2011-06-01

    We describe the factors that go into the component choices for a short wavelength IR (SWIR) imager, which include the SWIR sensor, the lens, and the illuminator. We have shown the factors for reducing dark current, and shown that we can achieve well below 1.5 nA/cm2 for 15 μm devices at 7 °C. In addition, we have mated our InGaAs detector arrays to 640×512 readout integrated integrated circuits to make focal plane arrays (FPAs). The resulting FPAs are capable of imaging photon fluxes with wavelengths between 1 and 1.6 μm at low light levels. The dark current associated with these FPAs is extremely low, exhibiting a mean dark current density of 0.26 nA/cm2 at 0 °C. Noise due to the readout can be reduced from 95 to 57 electrons by using off-chip correlated double sampling. In addition, Aerius has developed laser arrays that provide flat illumination in scenes that are normally light-starved. The illuminators have 40% wall-plug efficiency and provide low-speckle illumination, and provide artifact-free imagery versus conventional laser illuminators.

  5. Impact of a large negative gain-to-cavity wavelength detuning on the performance of InGaAlAs oxide-confined vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Blokhin, Sergey A.; Bobrov, Mikhail A.; Maleev, Nikolai A.; Kuzmenkov, Alexander G.; Sakharov, Alexey V.; Blokhin, Alexey A.; Moser, Philip; Lott, James A.; Bimberg, Dieter; Ustinov, Viktor M.

    2015-03-01

    Vertical-cavity surface-emitting lasers (VCSELs) based on the InGaAlAs-materials system on GaAs substrates are the key component for short-reach data and computer communications systems. Several different modulation schemes have been developed to realize high data bit rates based on various oxide-confined near-infrared VCSEL designs operated under direct current modulation. However, one open question to resolve is the optimal gain-to-cavity wavelength detuning to employ for temperature-stable high-speed performance. We investigate the static and dynamic characteristics of 850 nm high-speed oxide-confined VCSELs with different negative gain-to-cavity wavelength detunings. Our oxideconfined 850 nm VCSELs with a more common ~10 nm negative gain-to-cavity detuning demonstrate the conventional optical mode behavior with a classical single-resonance frequency response. With a larger (≥ 20 nm) negative detuning, our devices with large oxide-aperture size (>6 μm) show an anomalous start of lasing via higher order modes with a subsequent switching to lasing via the lowest order modes at higher currents. At intermediate currents, co-lasing via two types of transverse modes and a two-resonance modulation response is observed. The increase of operation temperature as well as the reduction in the oxide-aperture area resulted in classical lasing of index-guided VCSELs. The observed optical mode behavior can be attributed to the specific index guiding profile caused by the oxide-apertures, low internal optical losses, and the large gain-to-cavity detuning. Moreover, one can suggest that the complex shape of the modulation response results from the mode competition for the available gain during an interesting co-lasing operating regime.

  6. 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.

  7. Laser addressed holographic memory system

    NASA Technical Reports Server (NTRS)

    Gange, R. A.; Wagle, E. M.; Steinmetz, C. C.

    1973-01-01

    Holographic recall and storage system uses red-lipid microcrystalline wax as storage medium. When laser beam strikes wax, its energy heats point of incidence enough to pass wax through transition temperature. Holograph image can then be written or erased in softened wax.

  8. 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.

  9. Radiation shielding for the Fermilab Vertical Cavity Test Facility

    SciTech Connect

    Ginsburg, Camille; Rakhno, Igor; /Fermilab

    2010-03-01

    The results of radiation shielding studies for the vertical test cryostat VTS1 at Fermilab performed with the codes FISHPACT and MARS15 are presented and discussed. The analysis is focused on operations with two RF cavities in the cryostat. The vertical cavity test facility (VCTF) for superconducting RF cavities in Industrial Building 1 at Fermilab has been in operation since 2007. The facility currently consists of a single vertical test cryostat VTS1. Radiation shielding for VTS1 was designed for operations with single 9-cell 1.3 GHz cavities, and the shielding calculations were performed using a simplified model of field emission as the radiation source. The operations are proposed to be extended in such a way that two RF cavities will be in VTS1 at a time, one above the other, with tests for each cavity performed sequentially. In such a case the radiation emitted during the tests from the lower cavity can, in part, bypass the initially designed shielding which can lead to a higher dose in the building. Space for additional shielding, either internal or external to VTS1, is limited. Therefore, a re-evaluation of the radiation shielding was performed. An essential part of the present analysis is in using realistic models for cavity geometry and spatial, angular and energy distributions of field-emitted electrons inside the cavities. The calculations were performed with the computer codes FISHPACT and MARS15.

  10. Cryogenic Infrastructure for Fermilab's Ilc Vertical Cavity Test Facility

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    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.

  11. 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.

    2008-03-16

    Fermilab is building a Vertical Cavity Test Facility (VCTF) to provide for R and 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.

  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. GaInNAs-based Hellish-vertical cavity semiconductor optical amplifier for 1.3 μm operation.

    PubMed

    Chaqmaqchee, Faten Adel Ismail; Mazzucato, Simone; Oduncuoglu, Murat; Balkan, Naci; Sun, Yun; Gunes, Mustafa; Hugues, Maxime; Hopkinson, Mark

    2011-01-01

    Hot electron light emission and lasing in semiconductor heterostructure (Hellish) devices are surface emitters the operation of which is based on the longitudinal injection of electrons and holes in the active region. These devices can be designed to be used as vertical cavity surface emitting laser or, as in this study, as a vertical cavity semiconductor optical amplifier (VCSOA). This study investigates the prospects for a Hellish VCSOA based on GaInNAs/GaAs material for operation in the 1.3-μm wavelength range. Hellish VCSOAs have increased functionality, and use undoped distributed Bragg reflectors; and this coupled with direct injection into the active region is expected to yield improvements in the gain and bandwidth. The design of the Hellish VCSOA is based on the transfer matrix method and the optical field distribution within the structure, where the determination of the position of quantum wells is crucial. A full assessment of Hellish VCSOAs has been performed in a device with eleven layers of Ga0.35In0.65N0.02As0.08/GaAs quantum wells (QWs) in the active region. It was characterised through I-V, L-V and by spectral photoluminescence, electroluminescence and electro-photoluminescence as a function of temperature and applied bias. Cavity resonance and gain peak curves have been calculated at different temperatures. Good agreement between experimental and theoretical results has been obtained. PMID:21711630

  14. GaInNAs-based Hellish-vertical cavity semiconductor optical amplifier for 1.3 μm operation

    PubMed Central

    2011-01-01

    Hot electron light emission and lasing in semiconductor heterostructure (Hellish) devices are surface emitters the operation of which is based on the longitudinal injection of electrons and holes in the active region. These devices can be designed to be used as vertical cavity surface emitting laser or, as in this study, as a vertical cavity semiconductor optical amplifier (VCSOA). This study investigates the prospects for a Hellish VCSOA based on GaInNAs/GaAs material for operation in the 1.3-μm wavelength range. Hellish VCSOAs have increased functionality, and use undoped distributed Bragg reflectors; and this coupled with direct injection into the active region is expected to yield improvements in the gain and bandwidth. The design of the Hellish VCSOA is based on the transfer matrix method and the optical field distribution within the structure, where the determination of the position of quantum wells is crucial. A full assessment of Hellish VCSOAs has been performed in a device with eleven layers of Ga0.35In0.65N0.02As0.08/GaAs quantum wells (QWs) in the active region. It was characterised through I-V, L-V and by spectral photoluminescence, electroluminescence and electro-photoluminescence as a function of temperature and applied bias. Cavity resonance and gain peak curves have been calculated at different temperatures. Good agreement between experimental and theoretical results has been obtained. PMID:21711630

  15. 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.

  16. Diode Laser Arrays

    NASA Astrophysics Data System (ADS)

    Botez, Dan; Scifres, Don R.

    1994-08-01

    This book provides a comprehensive overview of the fundamental principles and applications of semiconductor diode laser arrays. All of the major types of arrays are discussed in detail, including coherent, incoherent, edge- and surface-emitting, horizontal- and vertical-cavity, individually addressed, lattice- matched and strained-layer systems. The initial chapters cover such topics as lasers, amplifiers, external-cavity control, theoretical modeling, and operational dynamics. Spatially incoherent arrays are then described in detail, and the uses of vertical-cavity surface emitter and edge-emitting arrays in parallel optical-signal processing and multi-channel optical recording are discussed. Researchers and graduate students in solid state physics and electrical engineering studying the properties and applications of such arrays will find this book invaluable.

  17. 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.

  18. Simulation of Far-Field Properties of Coherent Vertical Cavity Surface Emitting Laser Array

    NASA Astrophysics Data System (ADS)

    Meng, Xun; Chen, Xu; Yi-Yang, Xie; Jun, Deng; Guo-Qing, Jiang; Guan-Zhong, Pan; Yi-Bo, Dong; Hong-Da, Chen

    2016-04-01

    Not Available Supported by the National Natural Science Foundation of China under Grant Nos 61376049, 61076044, 61107026 and 61204011, the Scientific Research Fund Project of Municipal Education Commission of Beijing under Grant No PXM2014-014204-07-000018.

  19. 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.

  20. Systems applications of vertical-cavity multi-quantum well optoelectronic modulators

    NASA Astrophysics Data System (ADS)

    Powell, Jeffry Scott

    1998-12-01

    A large portion of the 'optical computing' research over the last 10 years has been centered around vertical cavity optoelectronic modulators. These devices have several characteristics which make them desirable from a systems standpoint: low power dissipation, high speed, large contrast ratio, bandwidth, dense arrays, integration with silicon VLSI, and WDM capability. This thesis examines systems applications of these devices. Early experiments using a configuration of two of these devices known as a symmetric self electro-optic effect device to perform threshold logic are discussed and compared with similar devices for Boolean logic. An application of these modulators to optical neural networks is discussed. Modulators are used as output devices and integrated with MESFET circuitry and GaAs photodetectors. Next, I discuss a reflection/transmission modulator (or X-modulator), a very powerful device for optical computation, routing, and interconnection. The device is essentially a 3 input, 3 output conservative and reversible switch, an optoelectronic implementation of a Fredkin gate. The use of these devices for optical logic is exhibited. Using arrays of these modulators, reconfigurable switching, routing, and interconnection networks are constructed, including crossbar switches and field programmable gate arrays. Ongoing research is focussed on improving their characteristics and making them more flexible for systems applications. In particular, reduced operating voltages, optical control, and dual zone structures containing gain layers are investigated. Next, a new technology offered by AT&T at a workshop given last summer which involves smart pixels based on quantum well modulators and detectors flip chip bonded on to silicon VLSI chips is described. This technology has already demonstrated 1000's of optical inputs and outputs on a single chip and thus achieving aggregate data rates approaching 1 Tb/s. This technology has been used here to implement 2 x 2

  1. Ultrafast Laser Beam Switching and Pulse Train Generation by Using Coupled Vertical-Cavity, Surface-Emitting Lasers (VCSELS)

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M. (Inventor); Ning, Cun-Zheng (Inventor)

    2005-01-01

    Ultrafast directional beam switching is achieved using coupled VCSELs. This approach is demonstrated to achieve beam switching frequencies of 40 GHz and more and switching directions of about eight degrees. This switching scheme is likely to be useful for ultrafast optical networks at frequencies much higher than achievable with other approaches.

  2. Address substrates as promising targets for laser histochemical surgery as a nontraditional line in medicine

    NASA Astrophysics Data System (ADS)

    Piruzyan, L. A.; Mikhailovskiy, Ye. M.; Piruzyan, A. L.

    1999-12-01

    The priority concept of the laser histochemical surgery as a potentially novel line in medicine is presented. The histochemical stains, selectively coloring some targets (address substrates), that are cells or their biochemical ingredients, sensitize them to the laser irradiation. Such sensitization to laser irradiation by staining turns the colored targets into targets for the laser beam. The action of the irradiation onto its specific targets beats out of the cell its ingredients which participate in a pathology process. In particular, the beating of a stained ferment out of the general stage of biochemical processes characteristic for the pathology interrupts their currence. The laser beam, when beating out its stained targets without any damage of the unstained tissues, acts like a scalpel that cuts off affected tissues not brushing healthy ones. A scheme for testing stains as sensitizers of the `address substrates' to the laser irradiation is presented. As the criterion of the stain sensitization the fact was chosen of absence or weakness of pathomorphologic and biochemical signs of the disease in an experimental model of the pathology irradiated with laser after a stain use, while the pathology signs are present in a control sample. The basis is done for study of the histochemical stains as potential means for the laser histochemical surgery of disseminated sclerosis, mucopolysaccharidosis, hypercholesterolemia, myocardial infarction, cardiosclerosis, caries and parodontosis.

  3. Observation of "True" Optical Vortices in a Laser System

    NASA Astrophysics Data System (ADS)

    Barland, S.; Caboche, E.; Genevet, P.; Hachair, X.; Giudici, M.; Pedaci, F.; Tredicce, J. R.

    We briefly review a series of experiments performed at the Institut Nonlineaire de Nice on localized structures in semiconductor optical devices. We concentrate our attention on the observation of localized single addressable optical vortices. This type of optical vortices, predicted theoretically more than 30 years ago, have been only observed recently in a system formed by two vertical cavity surface emitter lasers (VCSELs) in a face-to-face configuration. We describe the experimental setup and we discuss the results and the reasons for which such a system is able to display "true" optical vortices.

  4. Properties of closely spaced independently addressable lasers fabricated by impurity-induced disordering

    SciTech Connect

    Thornton, R.L.; Mosby, W.J.; Donaldson, R.M.; Paoli, T.L. )

    1990-04-23

    We describe the fabrication and characteristics of closely spaced (10 {mu}m) dual-beam laser sources by the process of impurity-induced disordering. We present data demonstrating that these devices are capable of high efficiency and reliable operation when operated in a {ital p}-side up configuration. We also show that these devices can be placed in close proximity with a minimal amount of thermal and electrical interaction between devices. These features have significant implications for the realization of high-density arrays of independently addressable lasers for optical interconnection of integrated circuits and optical imaging systems.

  5. Bistability characteristics of different types of optical modes amplified by quantum dot vertical cavity semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Qasaimeh, Omar

    2016-04-01

    We have studied the characteristics of optical bistability of different types of optical modes amplified by small-size quantum dot vertical cavity semiconductor optical amplifiers operated in reflection. Our analysis reveals that TE01 mode exhibits stronger intensity-dependent non-linearity in small radius devices, which results in stronger optical phase modulation and therefore larger hysteresis width compared with the other modes. The effect of the wavelength detuning of the input signal on the shape of the hysteresis loop is studied. We find that butterfly hysteresis loop exhibits the largest hysteresis width compared with clockwise and counterclockwise loops. Our analysis reveals that doping the quantum dots with p-type doping slightly reduces the hysteresis width while doping the dots with n-type doping clearly increases the hysteresis width for any wavelength detuning. We estimate that the hysteresis width of quantum dot active layer will exhibit higher hysteresis width compared with quantum well active layer having the same threshold gain.

  6. The transverse instability in a differentially heated vertical cavity filled with molecular radiating gases. I. Linear stability analysis

    NASA Astrophysics Data System (ADS)

    Borget, V.; Bdéoui, F.; Soufiani, A.; Le Quéré, P.

    2001-05-01

    Radiation effects on the onset of the transverse instability in a differentially heated vertical cavity containing molecular emitting and absorbing gases in the so-called conduction regime is studied theoretically. Radiative transfer is treated using the full integro-differential formulation. The neutral stability curves are determined using a combined Galerkin-collocation method based on Chebyshev polynomials. A modified correlated-k model and the absorption distribution function model are used in order to take into account the spectral structure of the absorption coefficient for radiating molecules such as H2O and CO2. For transparent media, perfect agreement is found with the available data reported in the literature and, particularly, the principle of exchange of stability is found to hold for Prandtl number values less than 12.46. The study of gray media allows us to examine the basic mechanisms that yield to the onset of transverse instability as traveling waves. For real radiating gases, a parametric study for H2O and CO2 is reported. It is shown that the radiative transfer delays the onset of the transverse instability and this delay increases with temperature and decreases with boundary emissivities, while layer depth effects depend on the level of saturation of the gas active absorption bands. Whatever the gas considered, it is found that neither radiation effect on the basic flow nor the radiative power disturbances can be neglected.

  7. Flattop mode shaping of a vertical cavity surface emitting laser using an external-cavity aspheric mirror.

    PubMed

    Yang, Zhaohui; Leger, James

    2004-11-01

    Both square-shaped and circular-shaped flattop modes were experimentally demonstrated in extended-cavity broad-area VCSELs using aspheric feedback mirrors. These refractive aspheric mirrors were fabricated by electron-beam lithography on curved substrates. Excellent single-mode operation and improved power extraction efficiency were observed. The three-mirror structure of the VCSEL and the state-of-the-art fabrication of the aspheric mirror contribute to the superior VCSEL performance. The modal loss analysis using a rigid three-mirror-cavity simulation method is discussed. PMID:19484117

  8. Position-addressable digital laser scanning point fluorescence microscopy with a Blu-ray disk pickup head

    PubMed Central

    Tsai, Rung-Ywan; Chen, Jung-Po; Lee, Yuan-Chin; Huang, Chun-Chieh; Huang, Tai-Ting; Chiang, Hung-Chih; Cheng, Chih-Ming; Lo, Feng-Hsiang; Chang, Sheng-Li; Weng, Kuo-Yao; Chung, Lung-Pin; Chen, Jyh-Chern; Tiao, Golden

    2014-01-01

    A compact and position-addressable blue ray scanning microscope (BSM) based on a commercially available Blu-ray disk pickup head (PUH) is developed for cell imaging with high resolution and low cost. The BSM comprises two objective lenses with numerical apertures (NAs) of 0.85 and 0.6 for focusing blue and red laser beams, respectively, on the sample slide. The blue and red laser beams are co-located adjacent to each other and move synchronously. A specially designed sample slide is used with a sample area and an address-patterned area for sample holding and address recognition, respectively. The blue laser beam is focused on the sample area and is used for fluorescent excitation and image capturing, whereas the red laser beam is focused on the address-patterned area and is used for address recognition and dynamic focusing. The address-patterned area is divided into 310 sectors. The cell image of each sector of the sampling area has a corresponding address pattern. Fluorescence images of monkey-derived kidney epithelial cells and fibroblast cells in which the F-actin is stained with fluorophore phalloidin CF 405 are measured by the BSM, with results comparable to those measured by a Leica TCS CP2 confocal microscope. The cell image of an area of interest can be easily tracked based on the coded address, and a large-area sample image can be accurately reconstructed from the sector images. PMID:24575338

  9. Thermal management of quantum cascade lasers in an individually addressable monolithic array architecture

    NASA Astrophysics Data System (ADS)

    Missaggia, Leo; Wang, Christine; Connors, Michael; Saar, Brian; Sanchez-Rubio, Antonio; Creedon, Kevin; Turner, George; Herzog, William

    2016-03-01

    There are a number of military and commercial applications for high-power laser systems in the mid-to-long-infrared wavelength range. By virtue of their demonstrated watt-level performance and wavelength diversity, quantum cascade laser (QCL) and amplifier devices are an excellent choice of emitter for those applications. To realize the power levels of interest, beam combining of arrays of these emitters is required and as a result, array technology must be developed. With this in mind, packaging and thermal management strategies were developed to facilitate the demonstration of a monolithic QCL array operating under CW conditions. Thermal models were constructed and simulations performed to determine the effect of parameters such as array-element ridge width and pitch on gain region temperature rise. The results of the simulations were considered in determining an appropriate QCL array configuration. State-of-the-art micro-impingement cooling along with an electrical distribution scheme comprised of AlN multi-layer technology were integrated into the design. The design of the module allows for individual electrical addressability of the array elements, a method of phase control demonstrated previously for coherent beam combining of diode arrays, along with access to both front and rear facets. Hence, both laser and single-pass amplifier arrays can be accommodated. A module was realized containing a 5 mm cavity length monolithic QCL array comprised of 7 elements on 450 m pitch. An output power of 3.16 W was demonstrated under CW conditions at an emission wavelength of 9μm.

  10. Semiconductor laser with multiple lasing wavelengths

    DOEpatents

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

    2003-07-29

    A new class of multi-terminal vertical-cavity semiconductor laser components has been developed. These multi-terminal laser components can be switched, either electrically or optically, between distinct lasing wavelengths, or can be made to lase simultaneously at multiple wavelengths.

  11. AlGaInN laser diode bar and array technology for high-power and individual addressable applications

    NASA Astrophysics Data System (ADS)

    Najda, S. P.; Perlin, P.; Suski, T.; Marona, L.; Boćkowski, M.; Leszczyński, M.; Wisniewski, P.; Czernecki, R.; Kucharski, R.; Targowski, G.

    2016-04-01

    The AlGaInN material system allows for laser diodes to be fabricated over a very wide range of wavelengths from u.v., ~380nm, to the visible ~530nm, by tuning the indium content of the laser GaInN quantum well, giving rise to new and novel applications for medical, industrial, display and scientific purposes. Ridge waveguide laser diode structures are fabricated to achieve single mode operation with high optical powers of >100mW with high reliability. Low defectivity and highly uniform GaN substrates allow arrays and bars of nitride lasers to be fabricated. We demonstrate the operation of monolithic AlGaInN laser bars with up to 20 emitters giving optical powers up to 4W cw at ~395nm with a common contact configuration. These bars are suitable for optical pumps and novel extended cavity systems. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be individually addressable allowing complex free-space and/or fibre optic system integration within a very small form-factor.

  12. Addressing Control of Hazardous Energy (COHE) Requirements in a Laser Safety Program

    SciTech Connect

    Woods, Michael; /SLAC

    2012-02-15

    OSHA regulation 29CFR1910.147 specifies control of hazardous energy requirements for 'the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or release of stored energy could cause injury to employees.' Class 3B and Class 4 laser beams must be considered hazardous energy sources because of the potential for serious eye injury; careful consideration is therefore needed to safely de-energize these lasers. This paper discusses and evaluates control of hazardous energy principles in this OSHA regulation, in ANSI Z136.1 ''Safe Use of Lasers,'' and in ANSI Z244.1 ''Control of Hazardous Energy, Lockout/Tagout and Alternative Methods.'' Recommendations are made for updating and improving CoHE (control of hazardous energy) requirements in these standards for their applicability to safe laser operations.

  13. Addressing the Numerical Challenges Associated With Laser-Induced Melt Convection

    NASA Astrophysics Data System (ADS)

    Weston, Brian; Nourgaliev, Robert; Delplanque, Jean Pierre; Anderson, Andy

    2015-11-01

    We present a new robust and efficient numerical framework for simulating multi-material flows with phase change. The work is motivated by laser-induced phase change applications, particularly the selective laser melting (SLM) process in additive manufacturing. Physics-based simulations of the laser melt dynamics requires a fully compressible framework, since incompressible flow solvers are inefficient for stiff systems, arising from laser-induced rapid phase change. In this study, the liquid and solid phases are both modeled with the compressible Navier-Stokes equations. The solid phase has an additional combined variable viscosity and drag force model to suppress the velocity in the solid. Our all-speed Navier-Stokes solver is based on a fully-implicit, high-order reconstructed Discontinuous Galerkin method. A Newton-Krylov based framework is used to solve the resulting set of non-linear equations, enabling robust simulations of the highly stiff compressible Navier-Stokes equations. We demonstrate the method's capabilities for phase change on several different melting and freezing configurations, including a three-dimensional laser-induced melt convection problem. Future model enhancements will incorporate material evaporation and rapid solidification.

  14. 1280 x 1024 video rate laser-addressed liquid crystal light valve color projection display

    NASA Astrophysics Data System (ADS)

    Phillips, Thomas E.; Lasher, Mark E.; Trias, John A.; Robinson, Waldo R.; Poirier, Peter M.; Dahlke, Weldon J.

    1992-11-01

    An all solid-state 1280 X 1024 laser raster scanner (LRS) system conforming to the EIA RS-343 television standard with a limiting resolution of 1300 TV lines has been developed. The laser scanner incorporates acousto-optic devices to perform video modulation and X-Y deflection and is used in time-multiplexed mode to photoactivate three liquid crystal valves in project full-color, video-rate, large-screen images. Analysis of the LRS optical system, projection optics, electronics, and light valve characteristics is presented.

  15. James Clerk Maxwell Prize Address: High Intensity Laser Propagation and Interactions

    NASA Astrophysics Data System (ADS)

    Sprangle, Phillip

    2013-10-01

    High intensity laser radiation sources cover a wide range of parameters, e.g., peak powers from tera to peta watts, pulse lengths from pico to femto seconds, repetition rates ranging from kilo to mega hertz and average powers of many tens of watts. This talk will cover, among other things, some of the unique physical processes which result when high intensity laser radiation interacts with gases and plasmas. One of the interesting topics to be discussed is the propagation of these laser pulses in a turbulent atmosphere which results in a multitude of coupled linear and nonlinear processes including filamentation and scintillation. Phase conjugation techniques to reduce the effects of atmospheric turbulence (scintillation) will be described. This talk will also discuss a range of potential applications of these high intensity lasers, including: electron acceleration in spatially periodic and tapered plasma channels, detection of radioactive material using electromagnetic signatures, atmospheric lasing of N2 molecules, as well as incoherent and coherent x-ray generation mechanisms. Research supported by NRL, ONR and UMD.

  16. Generation of picosecond pulses with a gain-switched GaAs surface-emitting laser

    SciTech Connect

    Karin, J.R.; Melcer, L.G.; Nagarajan, R.; Bowers, J.E.; Corzine, S.W.; Morton, P.A.; Geels, R.S.; Coldren, L.A. )

    1990-09-03

    Pulses shorter than 4 ps (deconvolved) have been obtained by optically gain switching a GaAs multiple quantum well vertical-cavity surface-emitting laser with a picosecond dye laser. Pulse width and relative peak delay were measured as a function of pump power. A theoretical model of the large signal response agrees well with the measured data. The model predicts the minimum achievable pulse width and pulse delay for this device structure. Experimental results and calculated values indicate that very high modulation rates are possible with vertical-cavity surface-emitting lasers.

  17. Comparison of Gaussian and super Gaussian laser beams for addressing atomic qubits

    NASA Astrophysics Data System (ADS)

    Gillen-Christandl, Katharina; Gillen, Glen D.; Piotrowicz, M. J.; Saffman, M.

    2016-05-01

    We study the fidelity of single-qubit quantum gates performed with two-frequency laser fields that have a Gaussian or super Gaussian spatial mode. Numerical simulations are used to account for imperfections arising from atomic motion in an optical trap, spatially varying Stark shifts of the trapping and control beams, and transverse and axial misalignment of the control beams. Numerical results that account for the three-dimensional distribution of control light show that a super Gaussian mode with intensity I˜ e^{-2(r/w_0)^n} provides reduced sensitivity to atomic motion and beam misalignment. Choosing a super Gaussian with n=6 the decay time of finite temperature Rabi oscillations can be increased by a factor of 60 compared to an n=2 Gaussian beam, while reducing crosstalk to neighboring qubit sites.

  18. Evaluation of laser-induced breakdown spectroscopy analysis potential for addressing radiological threats from a distance

    NASA Astrophysics Data System (ADS)

    Gaona, I.; Serrano, J.; Moros, J.; Laserna, J. J.

    2014-06-01

    Although radioactive materials are nowadays valuable tools in nearly all fields of modern science and technology, the dangers stemming from the uncontrolled use of ionizing radiation are more than evident. Since preparedness is a key issue to face the risks of a radiation dispersal event, development of rapid and efficient monitoring technologies to control the contamination caused by radioactive materials is of crucial interest. Laser-induced breakdown spectroscopy (LIBS) exhibits appealing features for this application. This research focuses on the assessment of LIBS potential for the in-situ fingerprinting and identification of radioactive material surrogates from a safe distance. LIBS selectivity and sensitivity to detect a variety of radioactive surrogates, namely 59Co, 88Sr, 130Ba, 133Cs, 193Ir and 238U, on the surface of common urban materials at a distance of 30 m have been evaluated. The performance of the technique for nuclear forensics has been also studied on different model scenarios. Findings have revealed the difficulties to detect and to identify the analytes depending on the surface being interrogated. However, as demonstrated, LIBS shows potential enough for prompt and accurate gathering of essential evidence at a number of sites after the release, either accidental or intentional, of radioactive material. The capability of standoff analysis confers to LIBS unique advantages in terms of fast and safe inspection of forensic scenarios. The identity of the radioactive surrogates is easily assigned from a distance and the sensitivity to their detection is in the range of a few hundreds of ng per square centimeter.

  19. Multistable monochromatic laser solitons

    SciTech Connect

    Genevet, P.; Columbo, L.; Barland, S.; Giudici, M.; Gil, L.; Tredicce, J. R.

    2010-05-15

    We study the spectral properties of stationary laser solitons (LSs) generated in two broad-area vertical cavity surface emitting lasers coupled to each other in face-to-face configuration [P. Genevet et al., Phys. Rev. Lett. 101, 123905 (2008)]. We demonstrate experimentally that LS emission occurs on a single longitudinal mode frequency of the compound cavity. Multistability is reported among differently 'colored' LSs. We also develop a theoretical model beyond the single longitudinal mode approximation whose numerical simulation results are in good agreement with the experimental observations.

  20. Emission properties of surface-emitting distributed-feedback and distributed-Bragg-reflector semiconductor lasers

    SciTech Connect

    Dziura, T. G.; Wang, S. C.

    1989-05-15

    We use a single-mode transfer equation model to study the performance of vertical-cavity surface-emitting distributed-feedback (DFB) and distributed-Bragg-reflector (DBR) semiconductor lasers above threshold. We find that DBR lasers exhibit less envelope spatial hole burning than both single and double phase-shifted DFB lasers and therefore may achieve more stable single-longitudinal-mode operation.

  1. Laser optomechanics.

    PubMed

    Yang, Weijian; Gerke, Stephen Adair; Ng, Kar Wei; Rao, Yi; Chase, Christopher; Chang-Hasnain, Connie J

    2015-01-01

    Cavity optomechanics explores the interaction between optical field and mechanical motion. So far, this interaction has relied on the detuning between a passive optical resonator and an external pump laser. Here, we report a new scheme with mutual coupling between a mechanical oscillator supporting the mirror of a laser and the optical field generated by the laser itself. The optically active cavity greatly enhances the light-matter energy transfer. In this work, we use an electrically-pumped vertical-cavity surface-emitting laser (VCSEL) with an ultra-light-weight (130 pg) high-contrast-grating (HCG) mirror, whose reflectivity spectrum is designed to facilitate strong optomechanical coupling, to demonstrate optomechanically-induced regenerative oscillation of the laser optomechanical cavity. We observe >550 nm self-oscillation amplitude of the micromechanical oscillator, two to three orders of magnitude larger than typical, and correspondingly a 23 nm laser wavelength sweep. In addition to its immediate applications as a high-speed wavelength-swept source, this scheme also offers a new approach for integrated on-chip sensors. PMID:26333804

  2. Laser optomechanics

    NASA Astrophysics Data System (ADS)

    Yang, Weijian; Adair Gerke, Stephen; Wei Ng, Kar; Rao, Yi; Chase, Christopher; Chang-Hasnain, Connie J.

    2015-09-01

    Cavity optomechanics explores the interaction between optical field and mechanical motion. So far, this interaction has relied on the detuning between a passive optical resonator and an external pump laser. Here, we report a new scheme with mutual coupling between a mechanical oscillator supporting the mirror of a laser and the optical field generated by the laser itself. The optically active cavity greatly enhances the light-matter energy transfer. In this work, we use an electrically-pumped vertical-cavity surface-emitting laser (VCSEL) with an ultra-light-weight (130 pg) high-contrast-grating (HCG) mirror, whose reflectivity spectrum is designed to facilitate strong optomechanical coupling, to demonstrate optomechanically-induced regenerative oscillation of the laser optomechanical cavity. We observe >550 nm self-oscillation amplitude of the micromechanical oscillator, two to three orders of magnitude larger than typical, and correspondingly a 23 nm laser wavelength sweep. In addition to its immediate applications as a high-speed wavelength-swept source, this scheme also offers a new approach for integrated on-chip sensors.

  3. Laser optomechanics

    PubMed Central

    Yang, Weijian; Adair Gerke, Stephen; Wei Ng, Kar; Rao, Yi; Chase, Christopher; Chang-Hasnain, Connie J.

    2015-01-01

    Cavity optomechanics explores the interaction between optical field and mechanical motion. So far, this interaction has relied on the detuning between a passive optical resonator and an external pump laser. Here, we report a new scheme with mutual coupling between a mechanical oscillator supporting the mirror of a laser and the optical field generated by the laser itself. The optically active cavity greatly enhances the light-matter energy transfer. In this work, we use an electrically-pumped vertical-cavity surface-emitting laser (VCSEL) with an ultra-light-weight (130 pg) high-contrast-grating (HCG) mirror, whose reflectivity spectrum is designed to facilitate strong optomechanical coupling, to demonstrate optomechanically-induced regenerative oscillation of the laser optomechanical cavity. We observe >550 nm self-oscillation amplitude of the micromechanical oscillator, two to three orders of magnitude larger than typical, and correspondingly a 23 nm laser wavelength sweep. In addition to its immediate applications as a high-speed wavelength-swept source, this scheme also offers a new approach for integrated on-chip sensors. PMID:26333804

  4. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Electrophysical and optical properties of spherical and cylindrical liquid-crystal optically addressed lenses

    NASA Astrophysics Data System (ADS)

    Guralnik, I. R.; Samagin, S. A.

    2004-07-01

    New experimental results on direct measurements of the phase response of spherical liquid-crystal (LC) optically addressed lenses (OALs) are presented. A simple and easy-to-use formula for the focal length of an adaptive modal LC lens is obtained for the first time. The complex conductance is measured with an accuracy that is sufficient to find the aperture region contribution and the calculated conductance is in good qualitative agreement with the experiment. The possibility of using OALs for self-correction of defocusing and as adaptive laser-beam deflectors is proposed and demonstrated experimentally.

  5. STUDY OF THE HUMAN CHRONIC WOUND TISSUE: ADDRESSING LOGISTIC BARRIERS AND PRODUCTIVE USE OF LASER CAPTURE MICRODISSECTION

    PubMed Central

    Roy, Sashwati; Sen, Chandan K

    2015-01-01

    Direct procurement of tissue samples from clinically presented chronic human wounds is a powerful approach to understand mechanism at play in an actual problem wound. While such approach suffers from limitations related to lack of reproducible conditions across wounds, something that we are used to the laboratory while studying wounds on experimental animals, the direct study of human wound tissue helps recognize the right questions to ask in the laboratory. Going back and forth between human wound and experimental animal studies helps steer studies on experimental wounds in a clinically relevant direction. In this article, we describe critical factors that need to be considered prior to planning a study involving human wound samples. In addition, we describe an approach to capture wound hyperproliferative epithelium (HE) from chronic human wound biopsies using laser capture microdissection (LCM). LCM is a new technology applicable to a broad range of clinical research and represents a catalyst of sophisticated translational research. PMID:24029938

  6. Two-mode dynamics in different semiconductor laser structures

    NASA Astrophysics Data System (ADS)

    Scirè, Alessandro; Sorel, Marc; Colet, Pere; Tessone, Claudio Juan; Mirasso, Claudio R.; San Miguel, Maxi

    2006-04-01

    We review three two-mode models for different semiconductor laser structures: Vertical-Cavity Surface-Emitting Lasers (VCSELs), Twin-Stripe Semiconductor-Lasers (TSSL), and Semiconductor Ring Lasers (SRL). The VCSELs model and TSSL model display rich dynamic behavior when a saturable absorber is embedded in the cavity. VCSELs with saturable absorber showed polarization chaos, which found applications in encoded communications; TSSLs with saturable absorber show coherent locked states as well as chaotic behavior; and SRLs show a complex two-mode dynamics giving rise to bidirectional operation, alternate oscillations and spontaneous symmetry breaking toward quasi-unidirectional bistable solutions, with potential applications to all-optical switching.

  7. Communication using VCSEL laser array

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M. (Inventor)

    2008-01-01

    Ultrafast directional beam switching, using coupled vertical cavity surface emitting lasers (VCSELs) is combined with a light modulator to provide information transfer at bit rates of tens of GHz. This approach is demonstrated to achieve beam switching frequencies of 32-50 GHz in some embodiments and directional beam switching with angular differences of about eight degrees. This switching scheme is likely to be useful for ultrafast optical networks at frequencies much higher than achievable with other approaches. A Mach-Zehnder interferometer, a Fabry-Perot etalon, or a semiconductor-based electro-absorption transmission channel, among others, can be used as a light modulator.

  8. Resonant activation in bistable semiconductor lasers

    SciTech Connect

    Lepri, Stefano; Giacomelli, Giovanni

    2007-08-15

    We theoretically investigate the possibility of observing resonant activation in the hopping dynamics of two-mode semiconductor lasers. We present a series of simulations of a rate-equation model under random and periodic modulation of the bias current. In both cases, for an optimal choice of the modulation time scale, the hopping times between the stable lasing modes attain a minimum. The simulation data are understood by means of an effective one-dimensional Langevin equation with multiplicative fluctuations. Our conclusions apply to both edge-emitting and vertical cavity lasers, thus opening the way to several experimental tests in such optical systems.

  9. Composite Resonator Surface Emitting Lasers

    SciTech Connect

    FISCHER,ARTHUR J.; CHOQUETTE,KENT D.; CHOW,WENG W.; ALLERMAN,ANDREW A.; GEIB,KENT M.

    2000-05-01

    The authors have developed electrically-injected coupled-resonator vertical-cavity lasers and have studied their novel properties. These monolithically grown coupled-cavity structures have been fabricated with either one active and one passive cavity or with two active cavities. All devices use a selectively oxidized current aperture in the lower cavity, while a proton implant was used in the active-active structures to confine current in the top active cavity. They have demonstrated optical modulation from active-passive devices where the modulation arises from dynamic changes in the coupling between the active and passive cavities. The laser intensity can be modulated by either forward or reverse biasing the passive cavity. They have also observed Q-switched pulses from active-passive devices with pulses as short as 150 ps. A rate equation approach is used to model the Q-switched operation yielding good agreement between the experimental and theoretical pulseshape. They have designed and demonstrated the operation of active-active devices which la.se simultaneously at both longitudinal cavity resonances. Extremely large bistable regions have also been observed in the light-current curves for active-active coupled resonator devices. This bistability can be used for high contrast switching with contrast ratios as high as 100:1. Coupled-resonator vertical-cavity lasers have shown enhanced mode selectivity which has allowed devices to lase with fundamental-mode output powers as high as 5.2 mW.

  10. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

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

  11. Visible light surface emitting semiconductor laser

    DOEpatents

    Olbright, Gregory R.; Jewell, Jack L.

    1993-01-01

    A vertical-cavity surface-emitting laser is disclosed comprising a laser cavity sandwiched between two distributed Bragg reflectors. The laser cavity comprises a pair of spacer layers surrounding one or more active, optically emitting quantum-well layers having a bandgap in the visible which serve as the active optically emitting material of the device. The thickness of the laser cavity is m .lambda./2n.sub.eff where m is an integer, .lambda. is the free-space wavelength of the laser radiation and n.sub.eff is the effective index of refraction of the cavity. Electrical pumping of the laser is achieved by heavily doping the bottom mirror and substrate to one conductivity-type and heavily doping regions of the upper mirror with the opposite conductivity type to form a diode structure and applying a suitable voltage to the diode structure. Specific embodiments of the invention for generating red, green, and blue radiation are described.

  12. In situ grown quantum-wire lasers

    NASA Astrophysics Data System (ADS)

    Coldren, L. A.; Gossard, A. C.; English, J. H.; Mui, D.; Corzine, S. W.

    1994-04-01

    This program concentrated on developing techniques to better understand and fabricate quantum-confined structures. The goal was to create the enabling technology for more efficient semiconductor lasers and integrated optoelectronic circuits. Over the contract period, significant advances occurred in the development of quantum-confined lasers, UHV in-situ processing technology, and the underlying theory for quantum-confined laser structures. The quantum-confined laser work included both quantum-wire laser and vertical-cavity laser development. This latter effort also required substantial improvements in the MBE growth technology. Much of this technology is now ready for transfer to industry. In fact, a number of joint projects with industry are underway, as a result of this program.

  13. Addressing healthcare.

    PubMed

    Daly, Rich

    2013-02-11

    Though President Barack Obama has rarely made healthcare references in his State of the Union addresses, health policy experts are hoping he changes that strategy this year. "The question is: Will he say anything? You would hope that he would, given that that was the major issue he started his presidency with," says Dr. James Weinstein, left, of the Dartmouth-Hitchcock health system. PMID:23487896

  14. Preliminary surface-emitting laser logic device evaluation

    NASA Astrophysics Data System (ADS)

    Libby, S. I.; Parker, M. A.; Olbright, G. R.; Swanson, P. D.

    1993-03-01

    This report discusses the evaluation of a monolithically integrated heterojunction phototransistor and vertical-cavity surface-emitting laser, designated the surface-Emitting Laser Logic device (CELL). Included is a discussion of the device structure and theory of operation, test procedures, results, and conclusions. Also presented is the CELL's opto-electronic input/output characteristics which includes spectral analysis, characteristic emitted light versus current and current versus voltage curves, input wavelength tolerance, output wavelength sensitivity to bias current, and insensitivity to input wavelength and power within a specified range.

  15. Inaugural address

    NASA Astrophysics Data System (ADS)

    Joshi, P. S.

    2014-03-01

    From jets to cosmos to cosmic censorship P S Joshi Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India E-mail: psj@tifr.res.in 1. Introduction At the outset, I should like to acknowledge that part of the title above, which tries to capture the main flavour of this meeting, and has been borrowed from one of the plenary talks at the conference. When we set out to make the programme for the conference, we thought of beginning with observations on the Universe, but then we certainly wanted to go further and address deeper questions, which were at the very foundations of our inquiry, and understanding on the nature and structure of the Universe. I believe, we succeeded to a good extent, and it is all here for you in the form of these Conference Proceedings, which have been aptly titled as 'Vishwa Mimansa', which could be possibly translated as 'Analysis of the Universe'! It is my great pleasure and privilege to welcome you all to the ICGC-2011 meeting at Goa. The International Conference on Gravitation and Cosmology (ICGC) series of meetings are being organized by the Indian Association for General Relativity and Gravitation (IAGRG), and the first such meeting was planned and conducted in Goa in 1987, with subsequent meetings taking place at a duration of about four years at various locations in India. So, it was thought appropriate to return to Goa to celebrate the 25 years of the ICGC meetings. The recollections from that first meeting have been recorded elsewhere here in these Proceedings. The research and teaching on gravitation and cosmology was initiated quite early in India, by V V Narlikar at the Banares Hindu University, and by N R Sen in Kolkata in the 1930s. In course of time, this activity grew and gained momentum, and in early 1969, at the felicitation held for the 60 years of V V Narlikar at a conference in Ahmedabad, P C Vaidya proposed the formation of the IAGRG society, with V V Narlikar being the first President. This

  16. Opening addresses.

    PubMed

    Chukudebelu, W O; Lucas, A O; Ransome-kuti, O; Akinla, O; Obayi, G U

    1988-01-01

    The theme of the 3rd International Conference of the Society of Gynecology and Obstetrics of Nigeria (SOGON) held October 26, 1986 in Enugu was maternal morbidity and mortality in Africa. The opening addresses emphasize the high maternal mortality rate in Africa and SOGON's dedication to promoting women's health and welfare. In order to reduce maternal mortality, the scope of this problem must be made evident by gathering accurate mortality rates through maternity care monitoring and auditing. Governments, health professionals, educators, behavioral scientists, and communication specialists have a responsibility to improve maternal health services in this country. By making the population aware of this problem through education, measures can be taken to reduce the presently high maternal mortality rates. Nigerian women are physically unprepared for childbirth; therefore, balanced diets and disease prevention should be promoted. Since about 40% of deliveries are unmanaged, training for traditional birth attendants should be provided. Furthermore, family planning programs should discourage teenage pregnancies, encourage birth spacing and small families, and promote the use of family planning techniques among men. The problem of child bearing and rearing accompanied by hard work should also be investigated. For practices to change so that maternal mortality rates can be reduced, attitudes must be changed such that the current rates are viewed as unacceptable. PMID:12179275

  17. VCSEL end-pumped passively Q-switched Nd:YAG laser with adjustable pulse energy.

    PubMed

    Goldberg, Lew; McIntosh, Chris; Cole, Brian

    2011-02-28

    A compact, passively Q-switched Nd:YAG laser utilizing a Cr4+:YAG saturable absorber, is end-pumped by the focused emission from an 804 nm vertical-cavity surface-emitting laser (VCSEL) array. By changing the VCSEL operating current, we demonstrated 2x adjustability in the laser output pulse energy, from 9 mJ to 18 mJ. This energy variation was attributed to changes in the angular distribution of VCSEL emission with drive current, resulting in a change in the pump intensity distribution generated by a pump-light-focusing lens. PMID:21369256

  18. Opening Address

    NASA Astrophysics Data System (ADS)

    Yamada, T.

    2014-12-01

    Ladies and Gentlemen, it is my great honor and pleasure to present an opening address of the 3rd International Workshop on "State of the Art in Nuclear Cluster Physics"(SOTANCP3). On the behalf of the organizing committee, I certainly welcome all your visits to KGU Kannai Media Center belonging to Kanto Gakuin University, and stay in Yokohama. In particular, to whom come from abroad more than 17 countries, I would appreciate your participations after long long trips from your homeland to Yokohama. The first international workshop on "State of the Art in Nuclear Cluster Physics", called SOTANCP, was held in Strasbourg, France, in 2008, and the second one was held in Brussels, Belgium, in 2010. Then the third workshop is now held in Yokohama. In this period, we had the traditional 10th cluster conference in Debrecen, Hungary, in 2012. Thus we have the traditional cluster conference and SOTANCP, one after another, every two years. This obviously shows our field of nuclear cluster physics is very active and flourishing. It is for the first time in about 10 years to hold the international workshop on nuclear cluster physics in Japan, because the last cluster conference held in Japan was in Nara in 2003, about 10 years ago. The president in Nara conference was Prof. K. Ikeda, and the chairpersons were Prof. H. Horiuchi and Prof. I. Tanihata. I think, quite a lot of persons in this room had participated at the Nara conference. Since then, about ten years passed. So, this workshop has profound significance for our Japanese colleagues. The subjects of this workshop are to discuss "the state of the art in nuclear cluster physics" and also discuss the prospect of this field. In a couple of years, we saw significant progresses of this field both in theory and in experiment, which have brought better and new understandings on the clustering aspects in stable and unstable nuclei. I think, the concept of clustering has been more important than ever. This is true also in the

  19. Presidential address.

    PubMed

    Vohra, U

    1993-07-01

    The Secretary of India's Ministry of Health and Family Welfare serves as Chair of the Executive Council of the International Institute for Population Sciences in Bombay. She addressed its 35th convocation in 1993. Global population stands at 5.43 billion and increases by about 90 million people each year. 84 million of these new people are born in developing countries. India contributes 17 million new people annually. The annual population growth rate in India is about 2%. Its population size will probably surpass 1 billion by the 2000. High population growth rates are a leading obstacle to socioeconomic development in developing countries. Governments of many developing countries recognize this problem and have expanded their family planning programs to stabilize population growth. Asian countries that have done so and have completed the fertility transition include China, Japan, Singapore, South Korea, and Thailand. Burma, Malaysia, North Korea, Sri Lanka, and Vietnam have not yet completed the transition. Afghanistan, Bangladesh, Iran, Nepal, and Pakistan are half-way through the transition. High population growth rates put pressure on land by fragmenting finite land resources, increasing the number of landless laborers and unemployment, and by causing considerable rural-urban migration. All these factors bring about social stress and burden civic services. India has reduced its total fertility rate from 5.2 to 3.9 between 1971 and 1991. Some Indian states have already achieved replacement fertility. Considerable disparity in socioeconomic development exists among states and districts. For example, the states of Bihar, Madhya Pradesh, Rajasthan, and Uttar Pradesh have female literacy rates lower than 27%, while that for Kerala is 87%. Overall, infant mortality has fallen from 110 to 80 between 1981 and 1990. In Uttar Pradesh, it has fallen from 150 to 98, while it is at 17 in Kerala. India needs innovative approaches to increase contraceptive prevalence rates

  20. Welcome Address

    NASA Astrophysics Data System (ADS)

    Kiku, H.

    2014-12-01

    Ladies and Gentlemen, It is an honor for me to present my welcome address in the 3rd International Workshop on "State of the Art in Nuclear Cluster Physics"(SOTANCP3), as the president of Kanto Gakuin University. Particularly to those from abroad more than 17 countries, I am very grateful for your participation after long long trips from your home to Yokohama. On the behalf of the Kanto Gakuin University, we certainly welcome your visit to our university and stay in Yokohama. First I would like to introduce Kanto Gakuin University briefly. Kanto Gakuin University, which is called KGU, traces its roots back to the Yokohama Baptist Seminary founded in 1884 in Yamate, Yokohama. The seminary's founder was Albert Arnold Bennett, alumnus of Brown University, who came to Japan from the United States to establish a theological seminary for cultivating and training Japanese missionaries. Now KGU is a major member of the Kanto Gakuin School Corporation, which is composed of two kindergartens, two primary schools, two junior high schools, two senior high schools as well as KGU. In this university, we have eight faculties with graduate school including Humanities, Economics, Law, Sciences and Engineering, Architecture and Environmental Design, Human and Environmental Studies, Nursing, and Law School. Over eleven thousands students are currently learning in our university. By the way, my major is the geotechnical engineering, and I belong to the faculty of Sciences and Engineering in my university. Prof. T. Yamada, here, is my colleague in the same faculty. I know that the nuclear physics is one of the most active academic fields in the world. In fact, about half of the participants, namely, more than 50 scientists, come from abroad in this conference. Moreover, I know that the nuclear physics is related to not only the other fundamental physics such as the elementary particle physics and astrophysics but also chemistry, medical sciences, medical cares, and radiation metrology

  1. Research on laser fuze technology based on MEMS/MOEMS

    NASA Astrophysics Data System (ADS)

    Chen, Huimin; Li, Ping; Zhang, Yingwen; Li, Kun; Sun, Jianqiang

    2007-12-01

    With the development of semiconductor laser technology, laser proximity fuzes have been widely used in various kinds of guided missiles and conventional ammunitions. Conventional laser proximity fuzes consisting of separated components, have the disadvantages such as large volumes and poor anti-jamming abilities, so are not satisfied with the modern warfare circumstances. Combined with the separated components, the system has been divided into transmitting module, receiving module and information processing module, the different modules have been analyzed in detail,. Meanwhile, the transmitting driven circuit has been developed and laser pulse with 20ns narrow width was obtained. In order to meet the multifunction and miniaturization, laser fuzes based on MEMS/MOEMS have been introduced in this paper. Technologies include vertical-cavity surface-emitting laser, integrated resonant-cavity photodetector and refractive micro-optics. The entire structure was roughly 1~2mm thick and 1mm on a side.

  2. Progress Toward Measuring CO2 Isotopologue Fluxes in situ with the LLNL Miniature, Laser-based CO2 Sensor

    NASA Astrophysics Data System (ADS)

    Osuna, J. L.; Bora, M.; Bond, T.

    2015-12-01

    One method to constrain photosynthesis and respiration independently at the ecosystem scale is to measure the fluxes of CO2­ isotopologues. Instrumentation is currently available to makes these measurements but they are generally costly, large, bench-top instruments. Here, we present progress toward developing a laser-based sensor that can be deployed directly to a canopy to passively measure CO2 isotopologue fluxes. In this study, we perform initial proof-of-concept and sensor characterization tests in the laboratory and in the field to demonstrate performance of the Lawrence Livermore National Laboratory (LLNL) tunable diode laser flux sensor. The results shown herein demonstrate measurement of bulk CO2 as a first step toward achieving flux measurements of CO2 isotopologues. The sensor uses a Vertical Cavity Surface Emitting Laser (VCSEL) in the 2012 nm range. The laser is mounted in a multi-pass White Cell. In order to amplify the absorption signal of CO2 in this range we employ wave modulation spectroscopy, introducing an alternating current (AC) bias component where f is the frequency of modulation on the laser drive current in addition to the direct current (DC) emission scanning component. We observed a strong linear relationship (r2 = 0.998 and r2 = 0.978 at all and low CO2 concentrations, respectively) between the 2f signal and the CO2 concentration in the cell across the range of CO2 concentrations relevant for flux measurements. We use this calibration to interpret CO2 concentration of a gas flowing through the White cell in the laboratory and deployed over a grassy field. We will discuss sensor performance in the lab and in situ as well as address steps toward achieving canopy-deployed, passive measurements of CO2 isotopologue fluxes. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675788

  3. Relative intensity noise in high speed microcavity laser

    NASA Astrophysics Data System (ADS)

    Tan, F.; Wu, M. K.; Liu, M.; Feng, M.; Holonyak, N.

    2013-09-01

    We have fabricated a high speed single mode microcavity laser of the form of oxide-confined vertical cavity surface emitting laser (VCSEL) and achieved an ultralow threshold current (ITH = 0.13 mA at 20 °C) with lasing wavelength at 837 nm. The optical spectrum of the microcavity VCSEL exhibits a mode spacing of 3.1 nm, which is corresponding to an optical modal cavity dimension of 2.5 μm. The device exhibits an enhanced modulation bandwidth of 22.6 GHz and a thermal noise limited laser intensity noise (electrical power spectral density of laser intensity noise below the thermal noise floor -174 dBm/Hz) as a consequence of low power laser operation and reduced mode competition in the microcavity.

  4. High power VCSEL array pumped Q-switched Nd:YAG lasers

    NASA Astrophysics Data System (ADS)

    Xiong, Yihan; Van Leeuwen, Robert; Watkins, Laurence S.; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

    2012-03-01

    Solid-state lasers pumped by high-power two-dimensional arrays of vertical-cavity surface-emitting lasers (VCSELs) were investigated. Both end-pumping and side-pumping schemes of Nd:YAG lasers with high power kW-class 808 nm VCSEL pump modules were implemented. For one application 10 mJ blue laser pulses were obtained from a frequencydoubled actively Q-switched VCSEL-array dual side-pumped Nd:YAG laser operating at 946 nm. For another application 10 mJ green laser pulses were obtained from a frequency-doubled passively Q-switched VCSEL-array endpumped Nd:YAG laser operating at 1064 nm. Both QCW and CW pumping schemes were investigated to achieve high average Q-switched power.

  5. Submonolayer Quantum Dots for High Speed Surface Emitting Lasers

    PubMed Central

    2007-01-01

    We report on progress in growth and applications of submonolayer (SML) quantum dots (QDs) in high-speed vertical-cavity surface-emitting lasers (VCSELs). SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers. Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting lasers (VCSELs) is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than 10−12has been achieved in a temperature range 25–85 °Cwithout current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission. PMID:21794188

  6. High power high repetition rate VCSEL array side-pumped pulsed blue laser

    NASA Astrophysics Data System (ADS)

    van Leeuwen, Robert; Zhao, Pu; Chen, Tong; Xu, Bing; Watkins, Laurence; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

    2013-03-01

    High power, kW-class, 808 nm pump modules based on the vertical-cavity surface-emitting laser (VCSEL) technology were developed for side-pumping of solid-state lasers. Two 1.2 kW VCSEL pump modules were implemented in a dual side-pumped Q-switched Nd:YAG laser operating at 946 nm. The laser output was frequency doubled in a BBO crystal to produce pulsed blue light. With 125 μs pump pulses at a 300 Hz repetition rate 6.1 W QCW 946 nm laser power was produced. The laser power was limited by thermal lensing in the Nd:YAG rod.

  7. Broadband ultrasound field mapping system using a wavelength tuned, optically scanned focused laser beam to address a Fabry Perot polymer film sensor.

    PubMed

    Zhang, Edward; Beard, Paul

    2006-07-01

    An optical system for rapidly mapping broad-band ultrasound fields with high spatial resolution has been developed. The transduction mechanism is based upon the detection of acoustically induced changes in the optical thickness of a thin polymer film acting as a Fabry Perot sensing interferometer (FPI). By using a PC-controlled galvanometer mirror to line-scan a focused laser beam over the surface of the FPI, and a wavelength-tuned phase bias control system to optimally set the FPI working point, a notional 1D ultrasound array was synthesized. This system enabled ultrasound fields to be mapped over an aperture of 40 mm, in 50-microm steps with an optically defined element size of 50 microm and an acquisition time of 50 ms per step. The sensor comprised a 38-microm polymer film FPI which was directly vacuum-deposited onto an impedance-matched polycarbonate backing stub. The -3 dB acoustic bandwidth of the sensor was 300 kHz to 28 MHz and the peak noise-equivalent-pressure was 10 kPa over a 20-MHz measurement bandwidth. To demonstrate the system, the outputs of various planar and focused pulsed ultrasound transducers with operating frequencies in the range 3.5 to 20 MHz were mapped. It is considered that this approach offers a practical and inexpensive alternative to piezoelectric-based arrays and scanning systems for rapid transducer field characterization and biomedical and industrial ultrasonic imaging applications. PMID:16889340

  8. Photoconductive semiconductor switches: Laser Q-switch trigger and switch-trigger laser integration

    SciTech Connect

    Loubriel, G.M.; Mar, A.; Hamil, R.A.; Zutavern, F.J.; Helgeson, W.D.

    1997-12-01

    This report provides a summary of the Pulser In a Chip 9000-Discretionary LDRD. The program began in January of 1997 and concluded in September of 1997. The over-arching goal of this LDRD is to study whether laser diode triggered photoconductive semiconductor switches (PCSS) can be used to activate electro-optic devices such as Q-switches and Pockels cells and to study possible laser diode/switch integration. The PCSS switches we used were high gain GaAs switches because they can be triggered with small amounts of laser light. The specific goals of the LDRD were to demonstrate: (1) that small laser diode arrays that are potential candidates for laser-switch integration will indeed trigger the PCSS switch, and (2) that high gain GaAs switches can be used to trigger optical Q-switches in lasers such as the lasers to be used in the X-1 Advanced Radiation Source and the laser used for direct optical initiation (DOI) of explosives. The technology developed with this LDRD is now the prime candidate for triggering the Q switch in the multiple lasers in the laser trigger system of the X-1 Advanced Radiation Source and may be utilized in other accelerators. As part of the LDRD we developed a commercial supplier. To study laser/switch integration we tested triggering the high gain GaAs switches with: edge emitting laser diodes, vertical cavity surface emitting lasers (VCSELs), and transverse junction stripe (TJS) lasers. The first two types of lasers (edge emitting and VCSELs) did activate the PCSS but are harder to integrate with the PCSS for a compact package. The US lasers, while easier to integrate with the switch, did not trigger the PCSS at the US laser power levels we used. The PCSS was used to activate the Q-switch of the compact laser to be used in the X-1 Advanced Radiation Source.

  9. Efficient, narrow-linewidth distributed-Bragg-reflector surface-emitting laser with periodic gain

    SciTech Connect

    Corzine, S.W.; Geels, R.S.; Yan, R.H.; Scott, J.W.; Colden, L.A.

    1989-03-01

    Efficient, narrow-line emission from a novel vertical-cavity distributed Bragg reflector surface emitting laser (DBR-SEL) with gain segments periodically placed on standing-wave maxima was obtained. Clean single-longitudinal-mode spectra with <2A line widths, sharp output/input characteristics, and thresholds below that of analogous all-GaAs active-region devices were obtained by optical pumping. Theoretical calculations indicate the optimum number of quantum wells and mirror reflectives for best threshold and efficiency.

  10. Awards and Addresses Summary

    PubMed Central

    2008-01-01

    Each year at the annual ASHG meeting, addresses are given in honor of the society and a number of award winners. A summary of each of these addresses is given below. On the next pages, we have printed the Presidential Address and the addresses for the William Allan Award. The other addresses, accompanied by pictures of the speakers, can be found at www.ashg.org.

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

    SciTech Connect

    Dezfouli, Mohsen Kamandar; Dignam, Marc M.

    2014-12-15

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

  12. Single-mode operation of mushroom structure surface emitting lasers

    SciTech Connect

    Wang, Y.J.; Dziura, T.G.; Wang, S.C. ); Du, G.; Wang, S. )

    1991-01-01

    Mushroom structure vertical cavity surface emitting lasers with a 0.6 {mu}m GaAs active layer sandwiched by two Al{sub 0.6{sup {minus}}}Ga{sub 0.4}As-Al{sub 0.08}Ga{sub 0.92}As multilayers as top and bottom mirrors exhibit 15 mA pulsed threshold current at 880 nm. Single longitudinal and single transverse mode operation was achieved on lasers with a 5 {mu}m diameter active region at current levels near 2 {times} I{sub th}. The light output above threshold current was linearly polarized with a polarization ratio of 25:1.

  13. Electron beam pumped semiconductor laser

    NASA Technical Reports Server (NTRS)

    Hug, William F. (Inventor); Reid, Ray D. (Inventor)

    2009-01-01

    Electron-beam-pumped semiconductor ultra-violet optical sources (ESUVOSs) are disclosed that use ballistic electron pumped wide bandgap semiconductor materials. The sources may produce incoherent radiation and take the form of electron-beam-pumped light emitting triodes (ELETs). The sources may produce coherent radiation and take the form of electron-beam-pumped laser triodes (ELTs). The ELTs may take the form of electron-beam-pumped vertical cavity surface emitting lasers (EVCSEL) or edge emitting electron-beam-pumped lasers (EEELs). The semiconductor medium may take the form of an aluminum gallium nitride alloy that has a mole fraction of aluminum selected to give a desired emission wavelength, diamond, or diamond-like carbon (DLC). The sources may be produced from discrete components that are assembled after their individual formation or they may be produced using batch MEMS-type or semiconductor-type processing techniques to build them up in a whole or partial monolithic manner, or combination thereof.

  14. Microfabrication techniques for semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Tamanuki, Takemasa; Tadokoro, T.; Morito, Ken; Koyama, Fumio; Iga, Kenichi

    1991-03-01

    Several important techniques for fabricating micro-cavity semiconductor lasers including surface emitting lasers have been developed. Reactive ion beam etch (RIBE) for GaA1As and GaInAsP is employed and its condition for vertical fine etch under low damages and removal of residual damages are made clear. Passivation by sulfur is introduced to the fabrication process. Regrowth techniques for DII structures by LPE and MOCVD has been established. Some device applications are discussed. 1. MICRO-ETCHING PROCESS Micro-cavity lasers including a vertical cavity surface emitting laser1 are attracting the research interest for optical parallel processing and parallel light wave systems. In order to realize micron-order or sub-micron laserdevices the technology of micro-fabrication must be established. In this study the total fabrication technology has been almost completed. First fine and low damage etching condition by ultrahigh vacuum background RIBE using a Cl2 gas has been made clear. We have found an isotropic etching condition for the vertical side wall formation and good mask traceability i. e. the acceleration voltage is 500 V and substrate temperature is 150 C with a 5000A thickness Si02 mask. Residual damages induced on the surface and the side wall are characterized by photo-luminescence and making stripe lasers. Figure 1 is the histogram of the nominal threshold current density for (a) oxide-defined stripe lasers (b) RIBE etched and LPE regrown BH-lasers using an LPE grown DII wafer (LPE/LPE) and (c) RIBE etched

  15. Flip-chip assembly of VCSELs to silicon grating couplers via laser fabricated SU8 prisms.

    PubMed

    Kaur, K S; Subramanian, A Z; Cardile, P; Verplancke, R; Van Kerrebrouck, J; Spiga, S; Meyer, R; Bauwelinck, J; Baets, R; Van Steenberge, G

    2015-11-01

    This article presents the flip-chip bonding of vertical-cavity surface-emitting lasers (VCSELs) to silicon grating couplers (GCs) via SU8 prisms. The SU8 prisms are defined on top of the GCs using non-uniform laser ablation process. The prisms enable perfectly vertical coupling from the bonded VCSELs to the GCs. The VCSELs are flip-chip bonded on top of the silicon GCs employing the laser-induced forward transfer (LIFT)-assisted thermocompression technique. An excess loss of < 1 dB at 1.55 µm measured from the bonded assemblies is reported in this paper. The results of high speed transmission experiments performed on the bonded assemblies with clear eye openings up to 20 Gb/s are also presented. PMID:26561097

  16. Optimizing electrically pumped vertical extended cavity surface emitting semiconductor lasers (E-VECSELs)

    NASA Astrophysics Data System (ADS)

    McInerney, John G.; Mooradian, Aram

    2011-03-01

    The future evolution of photonics, for a wide spectrum of applications ranging from established optical telecommunications to emerging opportunities such as biotechnology, reprographics and projection displays, will depend on availability of compact, rugged, efficient and inexpensive lasers which deliver high power, good beam quality, excellent wavelength stability, low noise and long lifetime in the near infrared and visible regions. This combination is not readily available from either of the traditional classes of semiconductor laser, edge-emitters and vertical cavity surface emitters (VCSELs). Here we describe a novel class of laser based on geometry similar to VCSELs but controlled by an extended coupled cavity. These devices are scalable to high powers while maintaining fundamental spatial mode performance, a feature that is essential to efficient coupling into a single mode optical fibre or waveguide, or long range propagation in free space. They are also ideally suited to mode locking, gain-switching and intracavity frequency conversion, among other applications.

  17. Optical modeling of certical-cavity surface-emitting lasers

    SciTech Connect

    Hadley, G.R.

    1996-12-31

    Vertical-cavity surface-emitting lasers (VCSELs) are presently the subject of intense research due to their potential as compact, efficient, astigmatic laser sources for a number of important applications. Of special interest are the selectively-oxidized VCSELs that have recently set records for threshold current and wall-plug efficiency. The onset of higher-order modes at powers of a few milliWatts, however, presently limits the wide utilization of these devices and indicates the need for improvements in design. Unfortunately, their complexity precludes optimization based solely upon empirical methods, and points instead to the need for better numerical models. Modeling the optical field in a vertical-cavity laser, however, is especially difficult due to both the high Q of the optical cavity and the distributed reflectivity of the mirrors. Our approach to this dilemma has been the development of modeling techniques on two complexity scales. We first derived an effective- index model that is numerically efficient and thus can be included together with carrier transport and thermal models to make up a self-consistent modeling package. In addition to its use in the overall VCSEL model, this simplified optical model has been extremely valuable in elucidating the basic principles of waveguiding in VCSELs that in turn have led to new ideas in device design. More specifically, the derived expression for the effective index shows clearly that index guiding in a VCSEL depends only on variations in optical cavity length, and thus can be engineered without the need to alter the material index of refraction. Also, we have designed index- guided and antiguided devices whose cavity lengths are modified in certain regions by etching of the cavity material prior to growth of the second mirror. Fabrication of these new device designs is presently in progress.

  18. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

    Schneider, Jr., Richard P.; Crawford, Mary H.

    1996-01-01

    A visible semiconductor laser. The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1.lambda.) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%.

  19. Addressivity in cogenerative dialogues

    NASA Astrophysics Data System (ADS)

    Hsu, Pei-Ling

    2014-03-01

    Ashraf Shady's paper provides a first-hand reflection on how a foreign teacher used cogens as culturally adaptive pedagogy to address cultural misalignments with students. In this paper, Shady drew on several cogen sessions to showcase his journey of using different forms of cogens with his students. To improve the quality of cogens, one strategy he used was to adjust the number of participants in cogens. As a result, some cogens worked and others did not. During the course of reading his paper, I was impressed by his creative and flexible use of cogens and at the same time was intrigued by the question of why some cogens work and not others. In searching for an answer, I found that Mikhail Bakhtin's dialogism, especially the concept of addressivity, provides a comprehensive framework to address this question. In this commentary, I reanalyze the cogen episodes described in Shady's paper in the light of dialogism. My analysis suggests that addressivity plays an important role in mediating the success of cogens. Cogens with high addressivity function as internally persuasive discourse that allows diverse consciousnesses to coexist and so likely affords productive dialogues. The implications of addressivity in teaching and learning are further discussed.

  20. Laser pyrometry

    NASA Technical Reports Server (NTRS)

    Stein, Alexander

    1988-01-01

    A method of determining the emissivity of a hot target from a laser-based reflectance measurement which is conducted simultaneously with a measurement of the target radiance is described. Once the correct radiance and emissivity are determined, one calculates the true target temperature from these parameters via the Planck equations. The design and performance of a laser pyrometer is described. The accuracy of laser pyrometry and the effect of ambient radiance are addressed.

  1. Key techniques for space-based solar pumped semiconductor lasers

    NASA Astrophysics Data System (ADS)

    He, Yang; Xiong, Sheng-jun; Liu, Xiao-long; Han, Wei-hua

    2014-12-01

    In space, the absence of atmospheric turbulence, absorption, dispersion and aerosol factors on laser transmission. Therefore, space-based laser has important values in satellite communication, satellite attitude controlling, space debris clearing, and long distance energy transmission, etc. On the other hand, solar energy is a kind of clean and renewable resources, the average intensity of solar irradiation on the earth is 1353W/m2, and it is even higher in space. Therefore, the space-based solar pumped lasers has attracted much research in recent years, most research focuses on solar pumped solid state lasers and solar pumped fiber lasers. The two lasing principle is based on stimulated emission of the rare earth ions such as Nd, Yb, Cr. The rare earth ions absorb light only in narrow bands. This leads to inefficient absorption of the broad-band solar spectrum, and increases the system heating load, which make the system solar to laser power conversion efficiency very low. As a solar pumped semiconductor lasers could absorb all photons with energy greater than the bandgap. Thus, solar pumped semiconductor lasers could have considerably higher efficiencies than other solar pumped lasers. Besides, solar pumped semiconductor lasers has smaller volume chip, simpler structure and better heat dissipation, it can be mounted on a small satellite platform, can compose satellite array, which can greatly improve the output power of the system, and have flexible character. This paper summarizes the research progress of space-based solar pumped semiconductor lasers, analyses of the key technologies based on several application areas, including the processing of semiconductor chip, the design of small and efficient solar condenser, and the cooling system of lasers, etc. We conclude that the solar pumped vertical cavity surface-emitting semiconductor lasers will have a wide application prospects in the space.

  2. Addressing Social Issues.

    ERIC Educational Resources Information Center

    Schoebel, Susan

    1991-01-01

    Maintains that advertising can help people become more aware of social responsibilities. Describes a successful nationwide newspaper advertising competition for college students in which ads address social issues such as literacy, drugs, teen suicide, and teen pregnancy. Notes how the ads have helped grassroots programs throughout the United…

  3. States Address Achievement Gaps.

    ERIC Educational Resources Information Center

    Christie, Kathy

    2002-01-01

    Summarizes 2 state initiatives to address the achievement gap: North Carolina's report by the Advisory Commission on Raising Achievement and Closing Gaps, containing an 11-point strategy, and Kentucky's legislation putting in place 10 specific processes. The North Carolina report is available at www.dpi.state.nc.us.closingthegap; Kentucky's…

  4. Address of the President

    ERIC Educational Resources Information Center

    Ness, Frederic W.

    1976-01-01

    The president of the Association of American Colleges addresses at the 62nd annual meeting the theme of the conference: "Looking to the Future--Liberal Education in a Radically Changing Society." Contributions to be made by AAC are examined. (LBH)

  5. Addressing Sexual Harassment

    ERIC Educational Resources Information Center

    Young, Ellie L.; Ashbaker, Betty Y.

    2008-01-01

    This article discusses ways on how to address the problem of sexual harassment in schools. Sexual harassment--simply defined as any unwanted and unwelcome sexual behavior--is a sensitive topic. Merely providing students, parents, and staff members with information about the school's sexual harassment policy is insufficient; schools must take…

  6. Space sciences - Keynote address

    NASA Technical Reports Server (NTRS)

    Alexander, Joseph K.

    1990-01-01

    The present status and projected future developments of the NASA Space Science and Applications Program are addressed. Emphasis is given to biochemistry experiments that are planned for the Space Station. Projects for the late 1990s which will study the sun, the earth's magnetosphere, and the geosphere are briefly discussed.

  7. A hybrid CATV/16-QAM-OFDM visible laser light communication system

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Yu; Li, Chung-Yi; Lu, Hai-Han; Chen, Chia-Yi; Jhang, Tai-Wei; Ruan, Sheng-Siang; Wu, Kuan-Hung

    2014-10-01

    A visible laser light communication (VLLC) system employing a vertical cavity surface emitting laser and spatial light modulator with hybrid CATV/16-QAM-OFDM modulating signals over a 5 m free-space link is proposed and demonstrated. With the assistance of a push-pull scheme, low-noise amplifier, and equalizer, good performances of composite second-order and composite triple beat are obtained, accompanied by an acceptable carrier-to-noise ratio performance for a CATV signal, and a low bit error rate value and clear constellation map are achieved for a 16-QAM-OFDM signal. Such a hybrid CATV/16-QAM-OFDM VLLC system would be attractive for providing services including CATV, Internet and telecommunication services.

  8. Absolute diode laser-based in situ detection of HCl in gasification processes

    NASA Astrophysics Data System (ADS)

    Ortwein, P.; Woiwode, W.; Fleck, S.; Eberhard, M.; Kolb, T.; Wagner, S.; Gisi, M.; Ebert, V.

    2010-10-01

    The release of HCl is an important parameter for industrial combustion and gasification processes, which must be determined in the ppm range for active process control and optimization. Based on a low power vertical-cavity surface-emitting laser (VCSEL) at 1.74 μm, we developed a new tuneable diode laser absorption spectrometer for calibration-free, absolute in situ HCl detection using the H35Cl (2 ← 0) R(3) absorption line with minimized cross-sensitivity to CO2 and H2O. The spectrometer was applied to in situ measurements in a gasification process ( T = 1,130°C, P = 1 atm, L = 28 cm) and yielded an optical resolution of 2.3·10-4, i.e. a HCl sensitivity of 45 ppm (13 ppm·m).

  9. Truly random number generation based on measurement of phase noise of a laser.

    PubMed

    Guo, Hong; Tang, Wenzhuo; Liu, Yu; Wei, Wei

    2010-05-01

    We present a simple approach to realize truly random number generator based on measuring the phase noise of a single-mode vertical cavity surface emitting laser. The true randomness of the quantum phase noise originates from the spontaneous emission of photons and the random bit generation rate is ultimately limited only by the laser linewidth. With the final bit generation rate of 20 Mbit/s, the truly random bit sequence guaranteed by the uncertainty principle of quantum mechanics passes the three standard randomness tests (ENT, Diehard, and NIST Statistical Test Suites). Moreover, a continuously generated random bit sequence, with length up to 14 Gbit, is verified by two additional criteria for its true randomness. PMID:20866215

  10. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

    Schneider, R.P. Jr.; Crawford, M.H.

    1996-09-17

    The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1{lambda}) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%. 5 figs.

  11. Excerpts from keynote address

    SciTech Connect

    Creel, G.C.

    1995-06-01

    Excerpts from the keynote principally address emissions issues in the fossil power industry as related to heat rate improvements. Stack emissions of both sulfur and nitrogen oxides are discussed, and a number of examples are given: (1) PEPCO`s Potomac River Station, and (2) Morgantown station`s NOX reduction efforts. Circulating water emissions are also briefly discussed, as are O & M costs of emission controls.

  12. Holographic content addressable storage

    NASA Astrophysics Data System (ADS)

    Chao, Tien-Hsin; Lu, Thomas; Reyes, George

    2015-03-01

    We have developed a Holographic Content Addressable Storage (HCAS) architecture. The HCAS systems consists of a DMD (Digital Micromirror Array) as the input Spatial Light Modulator (SLM), a CMOS (Complementary Metal-oxide Semiconductor) sensor as the output photodetector and a photorefractive crystal as the recording media. The HCAS system is capable of performing optical correlation of an input image/feature against massive reference data set stored in the holographic memory. Detailed system analysis will be reported in this paper.

  13. Content addressable memory project

    NASA Technical Reports Server (NTRS)

    Hall, J. Storrs; Levy, Saul; Smith, Donald E.; Miyake, Keith M.

    1992-01-01

    A parameterized version of the tree processor was designed and tested (by simulation). The leaf processor design is 90 percent complete. We expect to complete and test a combination of tree and leaf cell designs in the next period. Work is proceeding on algorithms for the computer aided manufacturing (CAM), and once the design is complete we will begin simulating algorithms for large problems. The following topics are covered: (1) the practical implementation of content addressable memory; (2) design of a LEAF cell for the Rutgers CAM architecture; (3) a circuit design tool user's manual; and (4) design and analysis of efficient hierarchical interconnection networks.

  14. Bioreactors Addressing Diabetes Mellitus

    PubMed Central

    Minteer, Danielle M.; Gerlach, Jorg C.

    2014-01-01

    The concept of bioreactors in biochemical engineering is a well-established process; however, the idea of applying bioreactor technology to biomedical and tissue engineering issues is relatively novel and has been rapidly accepted as a culture model. Tissue engineers have developed and adapted various types of bioreactors in which to culture many different cell types and therapies addressing several diseases, including diabetes mellitus types 1 and 2. With a rising world of bioreactor development and an ever increasing diagnosis rate of diabetes, this review aims to highlight bioreactor history and emerging bioreactor technologies used for diabetes-related cell culture and therapies. PMID:25160666

  15. Addressing Environmental Health Inequalities.

    PubMed

    Gouveia, Nelson

    2016-01-01

    Environmental health inequalities refer to health hazards disproportionately or unfairly distributed among the most vulnerable social groups, which are generally the most discriminated, poor populations and minorities affected by environmental risks. Although it has been known for a long time that health and disease are socially determined, only recently has this idea been incorporated into the conceptual and practical framework for the formulation of policies and strategies regarding health. In this Special Issue of the International Journal of Environmental Research and Public Health (IJERPH), "Addressing Environmental Health Inequalities-Proceedings from the ISEE Conference 2015", we incorporate nine papers that were presented at the 27th Conference of the International Society for Environmental Epidemiology (ISEE), held in Sao Paulo, Brazil, in 2015. This small collection of articles provides a brief overview of the different aspects of this topic. Addressing environmental health inequalities is important for the transformation of our reality and for changing the actual development model towards more just, democratic, and sustainable societies driven by another form of relationship between nature, economy, science, and politics. PMID:27618906

  16. Content addressable memory project

    NASA Technical Reports Server (NTRS)

    Hall, Josh; Levy, Saul; Smith, D.; Wei, S.; Miyake, K.; Murdocca, M.

    1991-01-01

    The progress on the Rutgers CAM (Content Addressable Memory) Project is described. The overall design of the system is completed at the architectural level and described. The machine is composed of two kinds of cells: (1) the CAM cells which include both memory and processor, and support local processing within each cell; and (2) the tree cells, which have smaller instruction set, and provide global processing over the CAM cells. A parameterized design of the basic CAM cell is completed. Progress was made on the final specification of the CPS. The machine architecture was driven by the design of algorithms whose requirements are reflected in the resulted instruction set(s). A few of these algorithms are described.

  17. Bax: Addressed to kill.

    PubMed

    Renault, Thibaud T; Manon, Stéphen

    2011-09-01

    The pro-apoptototic protein Bax (Bcl-2 Associated protein X) plays a central role in the mitochondria-dependent apoptotic pathway. In healthy mammalian cells, Bax is essentially cytosolic and inactive. Following a death signal, the protein is translocated to the outer mitochondrial membrane, where it promotes a permeabilization that favors the release of different apoptogenic factors, such as cytochrome c. The regulation of Bax translocation is associated to conformational changes that are under the control of different factors. The evidences showing the involvement of different Bax domains in its mitochondrial localization are presented. The interactions between Bax and its different partners are described in relation to their ability to promote (or prevent) Bax conformational changes leading to mitochondrial addressing and to the acquisition of the capacity to permeabilize the outer mitochondrial membrane. PMID:21641962

  18. Magnetic content addressable memories

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenye

    Content Addressable Memories are designed with comparison circuits built into every bit cell. This parallel structure can increase the speed of searching from O(n) (as with Random Access Memories) to O(1), where n is the number of entries being searched. The high cost in hardware limits the application of CAM within situations where higher searching speed is extremely desired. Spintronics technology can build non-volatile Magnetic RAM with only one device for one bit cell. There are various technologies involved, like Magnetic Tunnel Junctions, off-easy-axis programming method, Synthetic Anti-Ferromagnetic tri-layers, Domain Wall displacement, Spin Transfer Torque tri-layers and etc. With them, particularly the Tunnel Magneto-Resistance variation in MTJ due to difference in magnetization polarity of the two magnets, Magnetic CAM can be developed with reduced hardware cost. And this is demonstrated by the discussion in this dissertation. Six MCAM designs are discussed. In the first design, comparand (C), local information (S) and their complements are stored into 4 MTJs connected in XOR gate pattern. The other five designs have one or two stacks for both information storage and comparison, and full TMR ratio can be taken advantage of. Two challenges for the five are specifically programming C without changing S and selectively programming a cell out of an array. The solutions to specific programming are: by confining the programming field for C in a ring structure design; by using field programming and spin polarized current programming respectively for C and S in the SAF+DW and SAF+STT tri-layer design; by making use of the difference in thresholds between direct mode and toggle mode switching in the SAF+SAF design. The problem of selective programming is addressed by off-easy-axis method and by including SAF tri-layers. Cell with STT tri-layers for both C and S can completely avoid the problems of specific and selective programming, but subject to the limit of

  19. Monolithically Integrated High-β Nanowire Lasers on Silicon.

    PubMed

    Mayer, B; Janker, L; Loitsch, B; Treu, J; Kostenbader, T; Lichtmannecker, S; Reichert, T; Morkötter, S; Kaniber, M; Abstreiter, G; Gies, C; Koblmüller, G; Finley, J J

    2016-01-13

    Reliable technologies for the monolithic integration of lasers onto silicon represent the holy grail for chip-level optical interconnects. In this context, nanowires (NWs) fabricated using III-V semiconductors are of strong interest since they can be grown site-selectively on silicon using conventional epitaxial approaches. Their unique one-dimensional structure and high refractive index naturally facilitate low loss optical waveguiding and optical recirculation in the active NW-core region. However, lasing from NWs on silicon has not been achieved to date, due to the poor modal reflectivity at the NW-silicon interface. We demonstrate how, by inserting a tailored dielectric interlayer at the NW-Si interface, low-threshold single mode lasing can be achieved in vertical-cavity GaAs-AlGaAs core-shell NW lasers on silicon as measured at low temperature. By exploring the output characteristics along a detection direction parallel to the NW-axis, we measure very high spontaneous emission factors comparable to nanocavity lasers (β = 0.2) and achieve ultralow threshold pump energies ≤11 pJ/pulse. Analysis of the input-output characteristics of the NW lasers and the power dependence of the lasing emission line width demonstrate the potential for high pulsation rates ≥250 GHz. Such highly efficient nanolasers grown monolithically on silicon are highly promising for the realization of chip-level optical interconnects. PMID:26618638

  20. Final report on LDRD project: Semiconductor surface-emitting microcavity laser spectroscopy for analysis of biological cells and microstructures

    SciTech Connect

    Gourley, P.L.; McDonald, A.E.; Gourley, M.F.; Bellum, J.

    1997-08-01

    This article discusses a new intracavity laser technique that uses living or fixed cells as an integral part of the laser. The cells are placed on a GaAs based semiconductor wafer comprising one half of a vertical cavity surface-emitting laser. After placement, the cells are covered with a dielectric mirror to close the laser cavity. When photo-pumped with an external laser, this hybrid laser emits coherent light images and spectra that depend sensitively on the cell size, shape, and dielectric properties. The light spectra can be used to identify different cell types and distinguish normal and abnormal cells. The laser can be used to study single cells in real time as a cell-biology lab-on-a-chip, or to study large populations of cells by scanning the pump laser at high speed. The laser is well-suited to be integrated with other micro-optical or micro-fluidic components to lead to micro-optical-mechanical systems for analysis of fluids, particulates, and biological cells.

  1. Advances in solid state laser technology for space and medical applications

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Buoncristiani, A. M.

    1988-01-01

    Recent developments in laser technology and their potential for medical applications are discussed. Gas discharge lasers, dye lasers, excimer lasers, Nd:YAG lasers, HF and DF lasers, and other commonly used lasers are briefly addressed. Emerging laser technology is examined, including diode-pumped lasers and other solid state lasers.

  2. Laser bottom hole assembly

    DOEpatents

    Underwood, Lance D; Norton, Ryan J; McKay, Ryan P; Mesnard, David R; Fraze, Jason D; Zediker, Mark S; Faircloth, Brian O

    2014-01-14

    There is provided for laser bottom hole assembly for providing a high power laser beam having greater than 5 kW of power for a laser mechanical drilling process to advance a borehole. This assembly utilizes a reverse Moineau motor type power section and provides a self-regulating system that addresses fluid flows relating to motive force, cooling and removal of cuttings.

  3. Laser power transmission

    NASA Technical Reports Server (NTRS)

    Conway, Edmund J.

    1992-01-01

    An overview of previous studies related to laser power transmission is presented. Particular attention is given to the use of solar pumped lasers for space power applications. Three general laser mechanisms are addressed: photodissociation lasing driven by sunlight, photoexcitation lasing driven directly by sunlight, and photoexcitation lasing driven by thermal radiation.

  4. New laser serves red light, straight up

    SciTech Connect

    Amato, I.

    1993-05-28

    Researchers have been trying to develop lasers that direct their light up through the top of a chip instead of out the side. But they've had little success in turning such lasers into efficient, practical emitters of the visible light prized for many applications. Now, researchers at Sandia National Laboratories have fashioned tiny surface-emitters that just may pass technological muster. In the 13 May issue of Electronics Letters, Sandia materials scientists Richard Schneider and James A. Lott report a new wrinkle on a technology familiar in the optoelectronics world-that of the so-called vertical cavity surface emitting lasers (VSCELs). To make their VSCEL, the Sandia scientists relied on a fabrication technique known as metalorganic vapor phase epitaxy, which enables them to build up complex multilayered constructions, molecular layer by molecular layer. The light-emitting heart of these constructions is the optical cavity, composed of several 10-nanometer-thick layers of the semiconductor indium-aluminum-gallium-phosphide. The cavity's quantum mechanical properties, which depend partly on the precise thicknesses of its layers, the specific semiconductors used, and the mechanical strain between adjacent layers, turn it into so-called quantum well in which electric charges approaching from the layers above and below it get trapped and recombine to emit red light. Bounding the cavity are complex mirrors made up of alternating sublayers of aluminum arsenide and aluminum gallium arsenide. The mirrors reflect and amplify the emitted light and pave a low resistance pathway into the cavity for electrons and holes - mobile positive charges. The electrical current that drives the laser enters through metal electrodes that are deposited onto the very top and bottom of the multilayered structure.

  5. Noise induced stabilization of chaotic free-running laser diode

    NASA Astrophysics Data System (ADS)

    Virte, Martin

    2016-05-01

    In this paper, we investigate theoretically the stabilization of a free-running vertical-cavity surface-emitting laser exhibiting polarization chaos dynamics. We report the existence of a boundary isolating the chaotic attractor on one side and a steady-state on the other side and identify the unstable periodic orbit playing the role of separatrix. In addition, we highlight a small range of parameters where the chaotic attractor passes through this boundary, and therefore where chaos only appears as a transient behaviour. Then, including the effect of spontaneous emission noise in the laser, we demonstrate that, for realistic levels of noise, the system is systematically pushed over the separating solution. As a result, we show that the chaotic dynamics cannot be sustained unless the steady-state on the other side of the separatrix becomes unstable. Finally, we link the stability of this steady-state to a small value of the birefringence in the laser cavity and discuss the significance of this result on future experimental work.

  6. 2014 ASHG Awards and Addresses

    PubMed Central

    2015-01-01

    Each year at the annual meeting of The American Society of Human Genetics (ASHG), addresses are given in honor of The Society and a number of award winners. A summary of each of these addresses is given below. On the following pages, we have printed the presidential address and the addresses for the William Allan Award, the Curt Stern Award, and the Victor A. McKusick Leadership Award. Webcasts of these addresses, as well as those of many other presentations, can be found at http://www.ashg.org.

  7. 2013 ASHG Awards and Addresses

    PubMed Central

    2014-01-01

    Each year at the annual meeting of The American Society of Human Genetics (ASHG), addresses are given in honor of The Society and a number of award winners. A summary of each of these addresses is given below. On the following pages, we have printed the Presidential Address and the addresses for the William Allan Award, the Curt Stern Award, and the Victor A. McKusick Leadership Award. Webcasts of these addresses, as well as those of many other presentations, can be found at http://www.ashg.org.

  8. Laser interferometer for absolute distance measurement based on a tunable VCSEL laser

    NASA Astrophysics Data System (ADS)

    Cip, Ondrej; Mikel, Bretislav; Lazar, Josef

    2005-02-01

    In the work, we present the absolute distance interferometer with a narrow-linewidth tunable VCSEL laser (Vertical-Cavity Surface-Emitting Laser) working at &lambda ~760 nm. As a detection technique, we use a fast wavelength-scanning interferometry improved by an amplitude division of the interference fringe with using two signals in quadrature. Used VCSEL laser is wide tunable with the mod-hop free tuning range more than 1.2 nm by means of the amplitude modulation of the injection current. We control the stabilization and tuning process of the laser wavelength with using the frequency lock to a Fabry-Perot resonator. We build that resonator as a glass plan-parallel etalon with high-fines. Except the frequency lock, the etalon helps us to measure a wavelength-tuning interval of VCSEL laser during the scanning process. We have stabilized an operating temperature of the VCSEL laser by means of a fast digital temperature controller. The optical set-up of the interferometer begins with a polarizing beam-splitter. It splits the laser beam into the measuring and reference arm of the Michelson interferometer. Two cubic corner cubes reflect beams back to this beam-splitter. It collects reflected beams to the same axis of propagation. Then a detection unit produces the combination of two perpendicularly polarized laser beams with production of two electronic signals that are in the quadrature. A fast analog-to-digital card equipped with the digital signal processor (DSP) samples these signals. DSP also controls the course of the scanning process. After Δλ ~ 1 nm scan of the wavelength of VCSEL laser we obtain a record of passed interference fringes and passed Fabry-Perot resonance modes at the same time. On basis of these measured quantities we are able to calculate with high precision the instantaneous value of the optical path length difference between the measuring and reference arm of the Michelson interferometer. We experimentally compared the developed absolute

  9. Pre-stabilized Lasers for Advanced Detectors

    NASA Astrophysics Data System (ADS)

    Man, C.-Nary

    Gravitational wave detectors need very stable continuous wave laser sources able to delivering high power beams. Realization of those lasers is a special R&D calling on very low noise controls on very reliable laser sources. After a brief introduction on the laser principles, we review the current laser sources for gravitational wave interferometric detectors, shortly describing the technologies of both solid-state and fiber lasers and amplifiers. A final section addresses the issue of laser pre-stabilization.

  10. Lasers-an effective artificial source of radiation for the cultivation of anoxygenic photosynthetic bacteria.

    PubMed

    Bertling, K; Hurse, T J; Kappler, U; Rakić, A D

    2006-06-01

    The laser diode (LD) is a unique light source that can efficiently produce all radiant energy within the narrow wavelength range used most effectively by a photosynthetic microorganism. We have investigated the use of a single type of LD for the cultivation of the well-studied anoxygenic photosynthetic bacterium, Rhodobacter capsulatus (Rb. capsulatus). An array of vertical-cavity surface-emitting lasers (VCSELs) was driven with a current of 25 mA, and delivered radiation at 860 nm with 0.4 nm linewidth. The emitted light was found to be a suitable source of radiant energy for the cultivation of Rb. capsulatus. The dependence of growth rate on incident irradiance was quantified. Despite the unusual nearly monochromatic light source used in these experiments, no significant changes in the pigment composition and in the distribution of bacteriochlorophyll between LHII and LHI-RC were detected in bacterial cells transferred from incandescent light to laser light. We were also able to show that to achieve a given growth rate in a light-limited culture, the VCSEL required only 30% of the electricity needed by an incandescent bulb, which is of great significance for the potential use of laser-devices in biotechnological applications and photobioreactor construction. PMID:16514675

  11. Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers.

    PubMed

    Jirauschek, Christian; Huber, Robert

    2015-07-01

    We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell's equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

  12. Wavelength shifting of intra-cavity photons: Adiabatic wavelength tuning in rapidly wavelength-swept lasers

    PubMed Central

    Jirauschek, Christian; Huber, Robert

    2015-01-01

    We analyze the physics behind the newest generation of rapidly wavelength tunable sources for optical coherence tomography (OCT), retaining a single longitudinal cavity mode during operation without repeated build up of lasing. In this context, we theoretically investigate the currently existing concepts of rapidly wavelength-swept lasers based on tuning of the cavity length or refractive index, leading to an altered optical path length inside the resonator. Specifically, we consider vertical-cavity surface-emitting lasers (VCSELs) with microelectromechanical system (MEMS) mirrors as well as Fourier domain mode-locked (FDML) and Vernier-tuned distributed Bragg reflector (VT-DBR) lasers. Based on heuristic arguments and exact analytical solutions of Maxwell’s equations for a fundamental laser resonator model, we show that adiabatic wavelength tuning is achieved, i.e., hopping between cavity modes associated with a repeated build up of lasing is avoided, and the photon number is conserved. As a consequence, no fundamental limit exists for the wavelength tuning speed, in principle enabling wide-range wavelength sweeps at arbitrary tuning speeds with narrow instantaneous linewidth. PMID:26203373

  13. High-power green and blue electron-beam pumped surface-emitting lasers using dielectric and epitaxial distributed Bragg reflectors

    SciTech Connect

    Klein, T.; Klembt, S.; Kozlovsky, V. I.; Zheng, A.; Tiberi, M. D.; Kruse, C.

    2015-03-21

    ZnSe-based electron-beam pumped vertical-cavity surface-emitting lasers for the green (λ = 530 nm) and blue (λ = 462 nm) spectral region have been realized. Structures with and without epitaxial bottom distributed Bragg reflector have been fabricated and characterized. The samples consist of an active region containing 20 quantum wells with a cavity length varying between an optical thickness of 10 λ to 20 λ. The active material is ZnCdSSe in case of the green devices and ZnSe for the blue ones. Room temperature single mode lasing for structures with and without epitaxial bottom mirror with a maximum output power up to 5.9 W (green) and 3.3 W (blue) is achieved, respectively.

  14. High-power green and blue electron-beam pumped surface-emitting lasers using dielectric and epitaxial distributed Bragg reflectors

    NASA Astrophysics Data System (ADS)

    Klein, T.; Klembt, S.; Kozlovsky, V. I.; Zheng, A.; Tiberi, M. D.; Kruse, C.

    2015-03-01

    ZnSe-based electron-beam pumped vertical-cavity surface-emitting lasers for the green (λ = 530 nm) and blue (λ = 462 nm) spectral region have been realized. Structures with and without epitaxial bottom distributed Bragg reflector have been fabricated and characterized. The samples consist of an active region containing 20 quantum wells with a cavity length varying between an optical thickness of 10 λ to 20 λ. The active material is ZnCdSSe in case of the green devices and ZnSe for the blue ones. Room temperature single mode lasing for structures with and without epitaxial bottom mirror with a maximum output power up to 5.9 W (green) and 3.3 W (blue) is achieved, respectively.

  15. Addressing problems of employee performance.

    PubMed

    McConnell, Charles R

    2011-01-01

    Employee performance problems are essentially of 2 kinds: those that are motivational in origin and those resulting from skill deficiencies. Both kinds of problems are the province of the department manager. Performance problems differ from problems of conduct in that traditional disciplinary processes ordinarily do not apply. Rather, performance problems are addressed through educational and remedial processes. The manager has a basic responsibility in ensuring that everything reasonable is done to help each employee succeed. There are a number of steps the manager can take to address employee performance problems. PMID:21537142

  16. Addressing Phonological Questions with Ultrasound

    ERIC Educational Resources Information Center

    Davidson, Lisa

    2005-01-01

    Ultrasound can be used to address unresolved questions in phonological theory. To date, some studies have shown that results from ultrasound imaging can shed light on how differences in phonological elements are implemented. Phenomena that have been investigated include transitional schwa, vowel coalescence, and transparent vowels. A study of…

  17. Communities Address Barriers to Connectivity.

    ERIC Educational Resources Information Center

    Byers, Anne

    1996-01-01

    Rural areas lag behind urban areas in access to information technologies. Public institutions play a critical role in extending the benefits of information technologies to those who would not otherwise have access. The most successful rural telecommunications plans address barriers to use, such as unawareness of the benefits, technophobia, the…

  18. Keynote Address: Rev. Mark Massa

    ERIC Educational Resources Information Center

    Massa, Mark S.

    2011-01-01

    Rev. Mark S. Massa, S.J., is the dean and professor of Church history at the School of Theology and Ministry at Boston College. He was invited to give a keynote to begin the third Catholic Higher Education Collaborative Conference (CHEC), cosponsored by Boston College and Fordham University. Fr. Massa's address posed critical questions about…

  19. State of the Lab Address

    ScienceCinema

    King, Alex

    2013-03-01

    In his third-annual State of the Lab address, Ames Laboratory Director Alex King called the past year one of "quiet but strong progress" and called for Ames Laboratory to continue to build on its strengths while responding to changing expectations for energy research.

  20. State of the Lab Address

    SciTech Connect

    King, Alex

    2010-01-01

    In his third-annual State of the Lab address, Ames Laboratory Director Alex King called the past year one of "quiet but strong progress" and called for Ames Laboratory to continue to build on its strengths while responding to changing expectations for energy research.

  1. Surface-emitting semiconductor laser for intracavity spectroscopy and microscopy

    SciTech Connect

    Meissner, K.E.; Gourley, P.L.; Brennan, T.M.; Hammons, B.E.; McDonald, A.E.

    1995-03-01

    The authors demonstrate lasing action in a novel microcavity laser which can be utilized for intracavity spectroscopy as well as high contrast imaging of small ({approximately} 10{mu}m) structures. The system can be easily visualized as a Fabry-Perot cavity containing a gain media and an object for study. Since the primary constraint on the object is transparency at the lasing wavelength, investigation of lasing in objects such as microspheres, liquid droplets, and biological cells is possible. The resonator consists of an epitaxial NME grown mirror and gain region on a GaAs wafer. This is essentially an open-cavity vertical cavity surface emitting laser (VCSEL). The object to be studied is placed on the wafer and covered with a glass dielectric mirror which acts as the output coupler. When the semiconductor gain region is photo-pumped, the object within the cavity provides lateral optical confinement through its index difference with the surrounding media, increases the cavity Q, and thus encourages lasing action. The emitted laser light can be spectrally and spatially resolved. The narrow lasing lines can provide information about the lasing modes supported and the size of the object. The spatially resolved laser light provides high contrast microscopic images of the electromagnetic modes oscillating in the resonator. The authors present an investigation of stable lasing modes in polystyrene spheres. This device could prove useful in biomedical diagnostics. It covers the correct spatial dimensions as well as wavelength region. In fact, an integrated system of these devices may provide a high speed, compact method of performing cell diagnostics.

  2. Widely continuous-tuning single-wavelength laser based on commercial multimode VCSELs

    NASA Astrophysics Data System (ADS)

    Yen, Tsu-Chiang; Hsu, Chuan-Pi; Wu, Yu-Heng; Cheng, Da-Long; Kuo, Wang-Chuang

    2010-08-01

    The conventional vertical-cavity surface-emitting lasers (VCSELs) are designed to have a very short resonant cavity. Therefore, the longitudinal mode of the VCSELs is intrinsically single; and the VCSELs are expected to be an excellent instrument for many precision measurements that demand high-purity single-wavelength light sources. However, the laser facet of the conventional VCSELs is relatively large, around 10 μm, which admits the emission of multi-transverse modes. Accordingly, conducting a single transverse mode from VCSELs is an important research topic. In this research, the beam-profile-adapted optical feedback (BPAF) method was investigated by a single-mode fiber cavity (SMFC), in which the beam profile of the multimode-VCSEL's output was adapted to the fundamental-transverse mode of an optical fiber to feedback into the laser's cavity. The operational principle and performance of BPAF will be presented. The experimental results successfully demonstrated that BPAF can efficiently conduct multimode VCSELs to stably lase the fundamental transverse mode with a wide tuning range of about 1090 GHz, or 2.62 nm, and a spectrum purity around 20 dB. Some precision spectrum measurements will be exhibited. These results will help to extend the application of the VCSELs in many precision measurements.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  4. High-capacity content-addressable memory architecture

    NASA Astrophysics Data System (ADS)

    Henshaw, Philip D.; Lis, Steven A.

    1993-11-01

    This paper describes a new hardware architecture for searching and accessing data. This Content Addressable Memory (CAM) can be implemented using holographic storage in spectral hole burning media. The use of laser wavelength as a fourth dimension for volume holographic recording provides an additional addressing variable which can be used to advantage in a CAM architecture. This paper consists of three parts: definition of a CAM, presentation of two CAM concepts for digital data string and analog function search, and a discussion of architecture issues.

  5. Nanoscale content-addressable memory

    NASA Technical Reports Server (NTRS)

    Davis, Bryan (Inventor); Principe, Jose C. (Inventor); Fortes, Jose (Inventor)

    2009-01-01

    A combined content addressable memory device and memory interface is provided. The combined device and interface includes one or more one molecular wire crossbar memories having spaced-apart key nanowires, spaced-apart value nanowires adjacent to the key nanowires, and configurable switches between the key nanowires and the value nanowires. The combination further includes a key microwire-nanowire grid (key MNG) electrically connected to the spaced-apart key nanowires, and a value microwire-nanowire grid (value MNG) electrically connected to the spaced-apart value nanowires. A key or value MNGs selects multiple nanowires for a given key or value.

  6. Addressing the workforce pipeline challenge

    SciTech Connect

    Leonard Bond; Kevin Kostelnik; Richard Holman

    2006-11-01

    A secure and affordable energy supply is essential for achieving U.S. national security, in continuing U.S. prosperity and in laying the foundations to enable future economic growth. To meet this goal the next generation energy workforce in the U.S., in particular those needed to support instrumentation, controls and advanced operations and maintenance, is a critical element. The workforce is aging and a new workforce pipeline, to support both current generation and new build has yet to be established. The paper reviews the challenges and some actions being taken to address this need.

  7. Identifying and Addressing Vaccine Hesitancy

    PubMed Central

    Kestenbaum, Lori A.; Feemster, Kristen A.

    2015-01-01

    In the 20th century, the introduction of multiple vaccines significantly reduced childhood morbidity, mortality, and disease outbreaks. Despite, and perhaps because of, their public health impact, an increasing number of parents and patients are choosing to delay or refuse vaccines. These individuals are described as vaccine hesitant. This phenomenon has developed due to the confluence of multiple social, cultural, political and personal factors. As immunization programs continue to expand, understanding and addressing vaccine hesitancy will be crucial to their successful implementation. This review explores the history of vaccine hesitancy, its causes, and suggested approaches for reducing hesitancy and strengthening vaccine acceptance. PMID:25875982

  8. Identifying and addressing vaccine hesitancy.

    PubMed

    Kestenbaum, Lori A; Feemster, Kristen A

    2015-04-01

    In the 20th century, the introduction of multiple vaccines significantly reduced childhood morbidity, mortality, and disease outbreaks. Despite, and perhaps because of, their public health impact, an increasing number of parents and patients are choosing to delay or refuse vaccines. These individuals are described as "vaccine hesitant." This phenomenon has developed due to the confluence of multiple social, cultural, political, and personal factors. As immunization programs continue to expand, understanding and addressing vaccine hesitancy will be crucial to their successful implementation. This review explores the history of vaccine hesitancy, its causes, and suggested approaches for reducing hesitancy and strengthening vaccine acceptance. PMID:25875982

  9. Wavelength-agile diode-laser sensing strategies for monitoring gas properties in optically harsh flows: application in cesium-seeded pulse detonation.

    PubMed

    Sanders, Scott; Mattison, Daniel; Ma, Lin; Jeffries, Jay; Hanson, Ronald

    2002-06-17

    The rapid, broad wavelength scanning capabilities of advanced diode lasers allow extension of traditional diode-laser absorption techniques to high pressure, transient, and generally hostile environments. Here, we demonstrate this extension by applying a vertical cavity surface-emitting laser (VCSEL) to monitor gas temperature and pressure in a pulse detonation engine (PDE). Using aggressive injection current modulation, the VCSEL is scanned through a 10 cm-1 spectral window at megahertz rates - roughly 10 times the scanning range and 1000 times the scanning rate of a conventional diode laser. The VCSEL probes absorption lineshapes of the ~ 852 nm D2 transition of atomic Cs, seeded at ~ 5 ppm into the feedstock gases of a PDE. Using these lineshapes, detonated-gas temperature and pressure histories, spanning 2000 - 4000 K and 0.5 - 30 atm, respectively, are recorded with microsecond time response. The increasing availability of wavelength-agile diode lasers should support the development of similar sensors for other harsh flows, using other absorbers such as native H2O. PMID:19436388

  10. Addressing viral resistance through vaccines

    PubMed Central

    Laughlin, Catherine; Schleif, Amanda; Heilman, Carole A

    2015-01-01

    Antimicrobial resistance is a serious healthcare concern affecting millions of people around the world. Antiviral resistance has been viewed as a lesser threat than antibiotic resistance, but it is important to consider approaches to address this growing issue. While vaccination is a logical strategy, and has been shown to be successful many times over, next generation viral vaccines with a specific goal of curbing antiviral resistance will need to clear several hurdles including vaccine design, evaluation and implementation. This article suggests that a new model of vaccination may need to be considered: rather than focusing on public health, this model would primarily target sectors of the population who are at high risk for complications from certain infections. PMID:26604979

  11. Addressing failures in exascale computing

    SciTech Connect

    Snir, Marc; Wisniewski, Robert W.; Abraham, Jacob A.; Adve, Sarita; Bagchi, Saurabh; Balaji, Pavan; Belak, Jim; Bose, Pradip; Cappello, Franck; Carlson, William; Chien, Andrew A.; Coteus, Paul; Debardeleben, Nathan A.; Diniz, Pedro; Engelmann, Christian; Erez, Mattan; Saverio, Fazzari; Geist, Al; Gupta, Rinku; Johnson, Fred; Krishnamoorthy, Sriram; Leyffer, Sven; Liberty, Dean; Mitra, Subhasish; Munson, Todd; Schreiber, Robert; Stearly, Jon; Van Hensbergen, Eric

    2014-05-01

    We present here a report produced by a workshop on “Addressing Failures in Exascale Computing” held in Park City, Utah, August 4–11, 2012. The charter of this workshop was to establish a common taxonomy about resilience across all the levels in a computing system; discuss existing knowledge on resilience across the various hardware and software layers of an exascale system; and build on those results, examining potential solutions from both a hardware and software perspective and focusing on a combined approach. The workshop brought together participants with expertise in applications, system software, and hardware; they came from industry, government, and academia; and their interests ranged from theory to implementation. The combination allowed broad and comprehensive discussions and led to this document, which summarizes and builds on those discussions.

  12. Light addressable photoelectrochemical cyanide sensor

    SciTech Connect

    Licht, S.; Myung, N.; Sun, Y.

    1996-03-15

    A sensor is demonstrated that is capable of spatial discrimination of cyanide with use of only a single stationary sensing element. Different spatial regions of the sensing element are light activated to reveal the solution cyanide concentration only at the point of illumination. In this light addressable photoelectrochemical (LAP) sensor the sensing element consists of an n-CdSe electrode immersed in solution, with the open-circuit potential determined under illumination. In alkaline ferro-ferri-cyanide solution, the open-circuit photopotential is highly responsive to cyanide, with a linear response of (120 mV) log [KCN]. LAP detection with a spatial resolution of {+-}1 mm for cyanide detection is demonstrated. The response is almost linear for 0.001-0.100 m cyanide with a resolution of 5 mV. 38 refs., 7 figs., 1 tab.

  13. Addressing Failures in Exascale Computing

    SciTech Connect

    Snir, Marc; Wisniewski, Robert; Abraham, Jacob; Adve, Sarita; Bagchi, Saurabh; Balaji, Pavan; Belak, J.; Bose, Pradip; Cappello, Franck; Carlson, Bill; Chien, Andrew; Coteus, Paul; DeBardeleben, Nathan; Diniz, Pedro; Engelmann, Christian; Erez, Mattan; Fazzari, Saverio; Geist, Al; Gupta, Rinku; Johnson, Fred; Krishnamoorthy, Sriram; Leyffer, Sven; Liberty, Dean; Mitra, Subhasish; Munson, Todd; Schreiber, Rob; Stearley, Jon; Van Hensbergen, Eric

    2014-01-01

    We present here a report produced by a workshop on Addressing failures in exascale computing' held in Park City, Utah, 4-11 August 2012. The charter of this workshop was to establish a common taxonomy about resilience across all the levels in a computing system, discuss existing knowledge on resilience across the various hardware and software layers of an exascale system, and build on those results, examining potential solutions from both a hardware and software perspective and focusing on a combined approach. The workshop brought together participants with expertise in applications, system software, and hardware; they came from industry, government, and academia, and their interests ranged from theory to implementation. The combination allowed broad and comprehensive discussions and led to this document, which summarizes and builds on those discussions.

  14. Lasers '86; Proceedings of the Ninth International Conference on Lasers and Applications, Orlando, FL, Nov. 3-7, 1986

    SciTech Connect

    Mcmillan, R.W.

    1987-01-01

    Laser physics, technology, and applications are examined in reviews and reports. Topics addressed include VUV and X-ray lasers, vibrational energy transfer and kinetics, medical applications, ultrashort lasers and spectroscopy, surface and material interactions, lasers in atmospheric physics, and fiber-optic systems. Consideration is given to alexandrite lasers, four-wave mixing and nonlinear optics, chemical lasers, semiconductor lasers, photothermal and photoacoustic spectroscopy, dye lasers, optical phase conjugation and SBS, excimer lasers, SDI laser applications, remote-sensing with lasers, FELs, and applications in chemistry. Diagrams, drawings, graphs, and photographs are provided.

  15. Light-addressable bacteriorhodopsin photocell

    NASA Astrophysics Data System (ADS)

    Wang, Wei W.; Knopf, George K.; Bassi, Amarjeet S.

    2004-09-01

    Bacteriorhodopsin (bR) thin films have been investigated in recent years as a viable biomaterial for constructing micro- or nanoscale optical devices. During illumination, the bR molecules in the thin film undergo a photocycle that is followed by a proton transport from the cytoplasmatic side to the extracellular side of the cell membrane. The photoelectric response induced by the charge displacement can be influenced by both the wavelength and intensity of the impinging light sources. A photocell based on the photoelectric properties of a thin bR film is described in this paper. The bR-based photocell is built as a sandwich-structural device with an ITO (Indium Tin Oxide) electrode/bR film/ITO electrode configuration. The photocell is fabricated by depositing the oriented bR film onto the grounded ITO electrode. The cytoplasmic side of the bR membrane is attached to the ITO conductive surface and the extracelluar side is placed in contact with the second ITO electrode that provides the signal input to the instrumentation circuit. A polyester thin film was used as the spacer separating the two ITO electrodes. The size of the active area of the photocell is about 10×10 mm. A HeNe laser coupled with an acoustic-optical scanning system is used as the light source. Experimental results confirm that the photoelectric response generated by the bR-photocell prototype is durable, stable, and highly sensitive to changes in light intensity. The sensitivity of the proposed signal transducer is 10.25mV/mW. The wavelength dependence of the photoelectric responses is similar to the optical absorption spectrum of bR membrane.

  16. High power laser diodes for the NASA direct detection laser transceiver experiment

    NASA Technical Reports Server (NTRS)

    Seery, Bernard D.; Holcomb, Terry L.

    1988-01-01

    High-power semiconductor laser diodes selected for use in the NASA space laser communications experiments are discussed. The diode selection rationale is reviewed, and the laser structure is shown. The theory and design of the third mirror lasers used in the experiments are addressed.

  17. Addressing neurological disorders with neuromodulation.

    PubMed

    Oluigbo, Chima O; Rezai, Ali R

    2011-07-01

    Neurological disorders are becoming increasingly common in developed countries as a result of the aging population. In spite of medications, these disorders can result in progressive loss of function as well as chronic physical, cognitive, and emotional disability that ultimately places enormous emotional and economic on the patient, caretakers, and the society in general. Neuromodulation is emerging as a therapeutic option in these patients. Neuromodulation is a field, which involves implantable devices that allow for the reversible adjustable application of electrical, chemical, or biological agents to the central or peripheral nervous system with the objective of altering its functioning with the objective of achieving a therapeutic or clinically beneficial effect. It is a rapidly evolving field that brings together many different specialties in the fields of medicine, materials science, computer science and technology, biomedical, and neural engineering as well as the surgical or interventional specialties. It has multiple current and emerging indications, and an enormous potential for growth. The main challenges before it are in the need for effective collaboration between engineers, basic scientists, and clinicians to develop innovations that address specific problems resulting in new devices and clinical applications. PMID:21193369

  18. Gender: addressing a critical focus.

    PubMed

    Thornton, L; Wegner, M N

    1995-01-01

    The definition of gender was addressed at the Fourth World Conference on Women (Beijing, China). After extensive debate, the definition developed by the UN Population Fund in 1995 was adopted: "a set of qualities and behaviors expected from a female or male by society." The sustainability of family planning (FP) programs depends on acknowledgment of the role gender plays in contraceptive decision-making and use. For example, programs must consider the fact that women in many cultures do not make FP decisions without the consent of their spouse. AVSC is examining providers' gender-based ideas about clients and the effects of these views on the quality of reproductive health services. Questions such as how service providers can encourage joint responsibility for contraception without requiring spousal consent or how they can make men feel comfortable about using a male method in a society where FP is considered a woman's issue are being discussed. Also relevant is how service providers can discuss sexual matters openly with female clients in cultures that do not allow women to enjoy their sexuality. Another concern is the potential for physical violence to a client as a result of the provision of FP services. PMID:12294397

  19. Exploring Ramsey-coherent population trapping atomic clock realized with pulsed microwave modulated laser

    SciTech Connect

    Yang, Jing; Yun, Peter; Tian, Yuan; Tan, Bozhong; Gu, Sihong

    2014-03-07

    A scheme for a Ramsey-coherent population trapping (CPT) atomic clock that eliminates the acousto-optic modulator (AOM) is proposed and experimentally studied. Driven by a periodically microwave modulated current, the vertical-cavity surface-emitting laser emits a continuous beam that switches between monochromatic and multichromatic modes. Ramsey-CPT interference has been studied with this mode-switching beam. In eliminating the AOM, which is used to generate pulsed laser in conventional Ramsey-CPT atomic clock, the physics package of the proposed scheme is virtually the same as that of a conventional compact CPT atomic clock, although the resource budget for the electronics will slightly increase as a microwave switch should be added. By evaluating and comparing experimentally recorded signals from the two Ramsey-CPT schemes, the short-term frequency stability of the proposed scheme was found to be 46% better than the scheme with AOM. The experimental results suggest that the implementation of a compact Ramsey-CPT atomic clock promises better frequency stability.

  20. Performance of a fire detector based on a compact laser spectroscopic carbon monoxide sensor.

    PubMed

    Hangauer, A; Chen, J; Strzoda, R; Fleischer, M; Amann, M-C

    2014-06-01

    In this paper we show the suitability of a miniaturized tunable diode laser spectroscopy (TDLS)-based carbon-monoxide (CO) sensor for fire detection applications. The sensor utilizes a vertical-cavity surface-emitting laser (VCSEL) and inherent calibration scheme with reference gas filled in the photodetector housing. The fire-detection experiments are carried out under realistic conditions as described in the European standard EN54. The CO generation of all class C fires (according to EN54) could be well resolved. The cross-sensitivity to other substances was found to be very low: the maximum CO false response from cigarette smoke, hairspray and general aerosols reaches a low value of a few μL/L and only if the substance is directly applied into the sensor gas inlet. Therefore this sensor overcomes the disadvantage of high false alarm rate given by smoke detectors and is also in small size which is suitable for household and industrial applications. Hence, the VCSEL-based TDLS sensor is shown to have sufficient performance for fire-detection. It has advantages such as capability for fail-safe operation and, low cross-sensitivities as compared to existing point fire detector technology which is presently limited by these factors. PMID:24921562

  1. Fabrication of Diffractive Optical Elements for an Integrated Compact Optical-MEMS Laser Scanner

    SciTech Connect

    WENDT,JOEL R.; KRYGOWSKI,T.W.; VAWTER,GREGORY A.; SPAHN,OLGA B.; SWEATT,WILLIAM C.; WARREN,MIAL E.; REYES,DAVID NMN

    2000-07-13

    The authors describe the microfabrication of a multi-level diffractive optical element (DOE) onto a micro-electromechanical system (MEMS) as a key element in an integrated compact optical-MEMS laser scanner. The DOE is a four-level off-axis microlens fabricated onto a movable polysilicon shuttle. The microlens is patterned by electron beam lithography and etched by reactive ion beam etching. The DOE was fabricated on two generations of MEMS components. The first generation design uses a shuttle suspended on springs and displaced by a linear rack. The second generation design uses a shuttle guided by roller bearings and driven by a single reciprocating gear. Both the linear rack and the reciprocating gear are driven by a microengine assembly. The compact design is based on mounting the MEMS module and a vertical cavity surface emitting laser (VCSEL) onto a fused silica substrate that contains the rest of the optical system. The estimated scan range of the system is {+-}4{degree} with a spot size of 0.5 mm.

  2. Bio-optimized energy transfer in densely packed fluorescent protein enables near-maximal luminescence and solid-state lasers

    NASA Astrophysics Data System (ADS)

    Gather, Malte C.; Yun, Seok Hyun

    2014-12-01

    Bioluminescent organisms are likely to have an evolutionary drive towards high radiance. As such, bio-optimized materials derived from them hold great promise for photonic applications. Here, we show that biologically produced fluorescent proteins retain their high brightness even at the maximum density in solid state through a special molecular structure that provides optimal balance between high protein concentration and low resonance energy transfer self-quenching. Dried films of green fluorescent protein show low fluorescence quenching (-7 dB) and support strong optical amplification (gnet=22 cm-1 96 dB cm-1). Using these properties, we demonstrate vertical cavity surface emitting micro-lasers with low threshold (<100 pJ, outperforming organic semiconductor lasers) and self-assembled all-protein ring lasers. Moreover, solid-state blends of different proteins support efficient Förster resonance energy transfer, with sensitivity to intermolecular distance thus allowing all-optical sensing. The design of fluorescent proteins may be exploited for bio-inspired solid-state luminescent molecules or nanoparticles.

  3. Lasers in space

    NASA Astrophysics Data System (ADS)

    Michaelis, M. M.; Forbes, A.; Bingham, R.; Kellett, B. J.; Mathye, A.

    2008-05-01

    A variety of laser applications in space, past, present, future and far future are reviewed together with the contributions of some of the scientists and engineers involved, especially those that happen to have South African connections. Historically, two of the earliest laser applications in space, were atmospheric LIDAR and lunar ranging. These applications involved atmospheric physicists, several astronauts and many of the staff recruited into the Soviet and North American lunar exploration programmes. There is a strong interest in South Africa in both LIDAR and lunar ranging. Shortly after the birth of the laser (and even just prior) theoretical work on photonic propulsion and space propulsion by laser ablation was initiated by Georgii Marx, Arthur Kantrowitz and Eugen Saenger. Present or near future experimental programs are developing in the following fields: laser ablation propulsion, possibly coupled with rail gun or gas gun propulsion; interplanetary laser transmission; laser altimetry; gravity wave detection by space based Michelson interferometry; the de-orbiting of space debris by high power lasers; atom laser interferometry in space. Far future applications of laser-photonic space-propulsion were also pioneered by Carl Sagan and Robert Forward. They envisaged means of putting Saenger's ideas into practice. Forward also invented a laser based method for manufacturing solid antimatter or SANTIM, well before the ongoing experiments at CERN with anti-hydrogen production and laser-trapping. SANTIM would be an ideal propellant for interstellar missions if it could be manufactured in sufficient quantities. It would be equally useful as a power source for the transmission of information over light year distances. We briefly mention military lasers. Last but not least, we address naturally occurring lasers in space and pose the question: "did the Big Bang lase?"

  4. Laser Technology.

    ERIC Educational Resources Information Center

    Gauger, Robert

    1993-01-01

    Describes lasers and indicates that learning about laser technology and creating laser technology activities are among the teacher enhancement processes needed to strengthen technology education. (JOW)

  5. Parity time-symmetric vertical cavities: intrinsically single-mode regime in longitudinal direction.

    PubMed

    Jones, Hugh F; Kulishov, Mykola; Kress, Bernard

    2016-07-25

    We explore a new class of distributed feedback (DFB) structures that employ the recently-developed concept of parity-time (PT) symmetry in optics. We show that, based on PT-symmetric pure reflective volume gratings, a vertical surface-emitting cavity can be constructed. We provide a detailed analysis of the threshold conditions as well as the wavelength and angular spectral characteristics using the Kogelnik coupled-wave approximation, backed up by an exact solution of the Helmholtz equation. We show that such a PT-symmetric cavity can be configured to support one and only one longitudinal mode, leading to inherently single-mode lasing. PMID:27464163

  6. An address geocoding solution for Chinese cities

    NASA Astrophysics Data System (ADS)

    Zhang, Xuehu; Ma, Haoming; Li, Qi

    2006-10-01

    We introduce the challenges of address geocoding for Chinese cities and present a potential solution along with a prototype system that deal with these challenges by combining and extending current geocoding solutions developed for United States and Japan. The proposed solution starts by separating city addresses into "standard" addresses which meet a predefined address model and non-standard ones. The standard addresses are stored in a structured relational database in their normalized forms, while a selected portion of the non-standard addresses are stored as aliases to the standard addresses. An in-memory address index is then constructed from the address database and serves as the basis for real-time address matching. Test results were obtained from two trials conducted in the city Beijing. On average 80% matching rate were achieved. Possible improvements to the current design are also discussed.

  7. Measurement of water vapor line strengths in the 1.4-2.7 μm range by tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Pogány, Andrea; Klein, Alexander; Ebert, Volker

    2015-11-01

    Line strengths of nine water vapor absorption lines in the wavelength range between 1.37 and 2.71 μm with line strengths of 10-23-10-20 cm/molecule have been measured using direct tunable diode laser absorption spectroscopy (dTDLAS). Four different light sources were used: three distributed feedback (DFB) diode lasers with wavelengths of 1.37 μm, 2.55 μm and 2.71 μm for measuring one application-specifically selected absorption line with each laser, and a vertical-cavity surface-emitting laser (VCSEL) radiating around 1.39 μm for the measurement of six further absorption lines. Despite the different light sources and line strengths, a uniform measurement and data evaluation method was developed and applied to all lines, and the experimental set-up was kept as similar as possible. This allows a thorough and uniform uncertainty analysis and evaluation of the contributions of the individual experimental parameters to the uncertainty of the derived line strengths. A comprehensive and transparent uncertainty analysis is given for the measurements. Uncertainties of our measured line strengths are in the 1.1-2.5% range (k=2, 95% confidence level). Our measured line strength values agree well with line strengths in the HITRAN 2012 database and other literature sources, we realized lower uncertainties up to a factor of 5-10.

  8. Laser Material Processing in Manufacturing

    NASA Astrophysics Data System (ADS)

    Jones, Marshall

    2014-03-01

    This presentation will address some of the past, present, and potential uses of lasers for material processing in manufacturing. Laser processing includes welding, drilling, cutting, cladding, etc. The U.S. was the hot bed for initial uses of lasers for material processing in the past with Europe, especially Germany, presently leading the way. The future laser processing leader may still be Germany. Selected uses, past and present, of lasers within GE will also be highlighted as seen in such business units as Aviation, Lighting, Power and Water, Healthcare, and Transportation.

  9. Understanding lasers

    SciTech Connect

    Gibilisco, S.

    1989-01-01

    Covering all different types of laser applications-Gibilisco offers an overview of this fascinating phenomenon of light. Here he describes what lasers are and how they work and examines in detail the different kinds of lasers in use today. Topics of particular interest include: the way lasers work; the different kinds of lasers; infrared, ultraviolet and x-ray lasers; use of lasers in industry and manufacturing; use of lasers for long-distance communications; fiberoptic communications; the way laser shows work; the reality of Star Wars; lasers in surgical and medical applications; and holography and the future of laser technology.

  10. Laser amplifier developments at Mercury

    SciTech Connect

    Rose, E.A.; Brucker, J.P.; Honig, E.M.; McCown, A.W.; Romero, V.O.; York, G.W.

    1993-09-01

    Electron-beam pumped laser amplifiers have been modified to address the mission of krypton-fluoride excimer laser technology development. Methods are described for improving the performance and reliability of two pre-existing amplifiers at minimal cost and time. Preliminary performance data are presented to support the credibility of the approach.

  11. 32 CFR 516.7 - Mailing addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 3 2011-07-01 2009-07-01 true Mailing addresses. 516.7 Section 516.7 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY AID OF CIVIL AUTHORITIES AND PUBLIC RELATIONS LITIGATION General § 516.7 Mailing addresses. Mailing addresses for organizations referenced...

  12. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  13. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  14. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  15. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  16. 47 CFR 97.23 - Mailing address.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Mailing address. 97.23 Section 97.23 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AMATEUR RADIO... name and mailing address. The mailing address must be in an area where the amateur service is...

  17. 47 CFR 13.10 - Licensee address.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Licensee address. 13.10 Section 13.10 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL COMMERCIAL RADIO OPERATORS General § 13.10 Licensee address. In accordance with § 1.923 of this chapter all applications must specify an address where...

  18. CCCC Chair's Address: Representing Ourselves, 2008

    ERIC Educational Resources Information Center

    Glenn, Cheryl

    2008-01-01

    This article presents the text of the author's address at the fifty-ninth annual convention of the Conference on College Composition and Communication (CCCC) in March 2008. In her address, the author picks up strands of previous Chairs' addresses and weaves them through the fabric of her remarks. What she hopes will give sheen to the fabric is her…

  19. 75 FR 49813 - Change of Address

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-16

    ... COMMISSION 11 CFR Parts 9405, 9407, 9409, 9410, 9420, and 9428 Change of Address AGENCY: United States... Assistance Commission (EAC) is amending its regulations to reflect a change of address for its headquarters. This technical amendment is a nomenclature change that updates and corrects the address for...

  20. 32 CFR 516.7 - Mailing addresses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Mailing addresses. 516.7 Section 516.7 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY AID OF CIVIL AUTHORITIES AND PUBLIC RELATIONS LITIGATION General § 516.7 Mailing addresses. Mailing addresses for organizations referenced...

  1. Matter in extreme conditions produced by lasers

    NASA Astrophysics Data System (ADS)

    Batani, Dimitri

    2016-06-01

    This perspective addresses the study of “extreme” states of matter created by laser pulses. We define “warm dense states” and “high energy density”, their importance in physics, how to produce and diagnose them, either using isochoric heating with short-pulse lasers or laser-driven shock waves.

  2. Quantum well intersubband THz lasers and detectors

    NASA Astrophysics Data System (ADS)

    Soref, Richard A.; Friedman, Lionel R.; Sun, Gregory; Noble, Michael J.; Ram-Mohan, L. R.

    1999-11-01

    This paper presents modeling and simulation results on Si- based quantum-well intersubband THz detectors and THz lasers (tasers) in the 3 to 10 THz range where the intersubband transition energy is 12 to 41 meV. The incoherent cryogenically cooled (4 K to 20 K) quantum well terahertz detector (QWTD) consists of p-type Si0.9Ge0.1 QWs with Si barriers on an Si substrate, or of p-Si0.85Ge0.15/Si on a relaxed Si0.97Ge0.03 buffer on Si. The QWTD senses THz radiation at normal incidence (the XY polarization on the HH1 to LH1 transition) or at edge- illumination (the Z polarization on the HH1 to HH2 transition). Resonant-cavity enhancement, coupling to Si THz waveguides, and integration with SiGe transistor preamplifiers appear feasible for QWTDs. The quantum staircase taser is a simplified far-infrared version of the quantum cascade laser in which each superlattice transfer region is replaced by a thin tunnel-barrier layer. We have adapted to group IV the III-V idea of Sun, Lu, and Khurgin; the `inverted mass taser'. On a Si0.81Ge0.19 substrate, we find that an inverted effective mass exists in LH1 at kg equals 0.013 angstroms-1 in 9-nm single- wells of Si0.7Ge0.3 with 5-nm Si barriers. Selective electrical injection of holes into LH1 at T equals 77 K is postulated. This offers local-in-k-space LH1-HH1 population inversion and tasing at 7.2 THz. Since the taser emission is XY-polarized, the active MQW staircase (a set of identical square QWs) is suitable for insertion into a vertical cavity surface-emitting taser. The VCSET would have resonator thickness of (lambda) /2n equals 6 micrometers , and Bragg mirrors constructed from SiO2/Si multilayers.

  3. 780nm-range VCSEL array for laser printer system and other applications at Ricoh

    NASA Astrophysics Data System (ADS)

    Jikutani, Naoto; Itoh, Akihiro; Harasaka, Kazuhiro; Sasaki, Toshihide; Sato, Shunichi

    2016-03-01

    A 780 nm-range 40 channels vertical-cavity surface-emitting laser (VCSEL) array was developed as a writing light source for printers. A 15° off missoriented GaAs substrate, an aluminum-free GaInAsP/GaInP compressively-strained multiple quantum well and an anisotropic-shape transverse-mode filter were employed to control polarization characteristics. The anisotropic-shape transverse-mode filter also suppressed higher transverse-mode and enabled high-power single-mode operation. Thus, orthogonal-polarization suppression-ratio (OPSR) of over 22 dB and side-mode suppression-ratio (SMSR) of 30 dB were obtained at operation power of 3mW at same time for wide oxide-aperture range below 50 μm2. Moreover, a thermal resistance was reduced for 38% by increasing a thickness of high thermal conductivity layer (3λ/4-AlAs layer) near a cavity. By this structure, a peak-power increased to 1.3 times. Moreover, a power-fall caused by self-heating at pulse-rise was decreased to 10% and the one caused by a thermal-crosstalk between channels was decreased to 46%. The VCSEL array was mounted in a ceramic package with a tilted seal glass to prevent optical-crosstalk caused by other channels. Thus, we achieved stable-output and high-quality beam characteristics for long-duration pulse drive.

  4. Individual Optical Addressing of Atomic Clock Qubits With Stark Shifts

    NASA Astrophysics Data System (ADS)

    Lee, Aaron; Smith, Jacob; Richerme, Phillip; Neyenhuis, Brian; Hess, Paul; Zhang, Jiehang; Monroe, Chris

    2016-05-01

    In recent years, trapped ions have proven to be a versatile quantum information platform, enabled by their long lifetimes and high gate fidelities. Some of the most promising trapped ion systems take advantage of groundstate hyperfine ``clock'' qubits, which are insensitive to background fields to first order. This same insensitivity also makes σz manipulations of the qubit impractical, eliminating whole classes of operations. We prove there exists a fourth-order light shift, or four-photon Stark shift, of the clock states derived from two coherent laser beams whose beatnote is close to the qubit splitting. Using a mode-locked source generates a large light shift with only modest laser powers, making it a practical σz operation on a clock qubit. We experimentally verify and measure the four-photon Stark shift and demonstrate its use to coherently individually address qubits in a chain of 10 Yb 171 ions with low crosstalk. We use this individual addressing to prepare arbitrary product states with high fidelity and also to apply independent σz terms transverse to an Ising Hamiltonian. This work is supported by the ARO Atomic Physics Program, the AFOSR MURI on Quantum Measurement and Verification, and the NSF Physics Frontier Center at JQI.

  5. Novel Duplicate Address Detection with Hash Function.

    PubMed

    Song, GuangJia; Ji, ZhenZhou

    2016-01-01

    Duplicate address detection (DAD) is an important component of the address resolution protocol (ARP) and the neighbor discovery protocol (NDP). DAD determines whether an IP address is in conflict with other nodes. In traditional DAD, the target address to be detected is broadcast through the network, which provides convenience for malicious nodes to attack. A malicious node can send a spoofing reply to prevent the address configuration of a normal node, and thus, a denial-of-service attack is launched. This study proposes a hash method to hide the target address in DAD, which prevents an attack node from launching destination attacks. If the address of a normal node is identical to the detection address, then its hash value should be the same as the "Hash_64" field in the neighboring solicitation message. Consequently, DAD can be successfully completed. This process is called DAD-h. Simulation results indicate that address configuration using DAD-h has a considerably higher success rate when under attack compared with traditional DAD. Comparative analysis shows that DAD-h does not require third-party devices and considerable computing resources; it also provides a lightweight security resolution. PMID:26991901

  6. Novel Duplicate Address Detection with Hash Function

    PubMed Central

    Song, GuangJia; Ji, ZhenZhou

    2016-01-01

    Duplicate address detection (DAD) is an important component of the address resolution protocol (ARP) and the neighbor discovery protocol (NDP). DAD determines whether an IP address is in conflict with other nodes. In traditional DAD, the target address to be detected is broadcast through the network, which provides convenience for malicious nodes to attack. A malicious node can send a spoofing reply to prevent the address configuration of a normal node, and thus, a denial-of-service attack is launched. This study proposes a hash method to hide the target address in DAD, which prevents an attack node from launching destination attacks. If the address of a normal node is identical to the detection address, then its hash value should be the same as the “Hash_64” field in the neighboring solicitation message. Consequently, DAD can be successfully completed. This process is called DAD-h. Simulation results indicate that address configuration using DAD-h has a considerably higher success rate when under attack compared with traditional DAD. Comparative analysis shows that DAD-h does not require third-party devices and considerable computing resources; it also provides a lightweight security resolution. PMID:26991901

  7. Addressing two-level systems variably coupled to an oscillating field.

    PubMed

    Navon, Nir; Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Almog, Ido; Ozeri, Roee

    2013-08-16

    We propose a simple method to spectrally resolve an array of identical two-level systems coupled to an inhomogeneous oscillating field. The addressing protocol uses a dressing field with a spatially dependent coupling to the atoms. We validate this scheme experimentally by realizing single-spin addressing of a linear chain of trapped ions that are separated by ~3 μm, dressed by a laser field that is resonant with the micromotion sideband of a narrow optical transition. PMID:23992060

  8. Addressing Two-Level Systems Variably Coupled to an Oscillating Field

    NASA Astrophysics Data System (ADS)

    Navon, Nir; Kotler, Shlomi; Akerman, Nitzan; Glickman, Yinnon; Almog, Ido; Ozeri, Roee

    2013-08-01

    We propose a simple method to spectrally resolve an array of identical two-level systems coupled to an inhomogeneous oscillating field. The addressing protocol uses a dressing field with a spatially dependent coupling to the atoms. We validate this scheme experimentally by realizing single-spin addressing of a linear chain of trapped ions that are separated by ˜3μm, dressed by a laser field that is resonant with the micromotion sideband of a narrow optical transition.

  9. 16 CFR 0.2 - Official address.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 1 2012-01-01 2012-01-01 false Official address. 0.2 Section 0.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE ORGANIZATION § 0.2 Official address. The principal office of the Commission is at Washington, DC. All communications to...

  10. 40 CFR 374.6 - Addresses.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 29 2012-07-01 2012-07-01 false Addresses. 374.6 Section 374.6 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND COMMUNITY RIGHT-TO-KNOW PROGRAMS PRIOR NOTICE OF CITIZEN SUITS § 374.6 Addresses. Administrator, U.S. Environmental Protection Agency, 1200...

  11. 16 CFR 0.2 - Official address.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 1 2011-01-01 2011-01-01 false Official address. 0.2 Section 0.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE ORGANIZATION § 0.2... 20580, unless otherwise specifically directed. The Commission's Web site address is www.ftc.gov....

  12. 16 CFR 0.2 - Official address.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Official address. 0.2 Section 0.2 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE ORGANIZATION § 0.2... 20580, unless otherwise specifically directed. The Commission's Web site address is www.ftc.gov....

  13. 10 CFR 218.34 - Addresses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 3 2010-01-01 2010-01-01 false Addresses. 218.34 Section 218.34 Energy DEPARTMENT OF ENERGY OIL STANDBY MANDATORY INTERNATIONAL OIL ALLOCATION Procedures § 218.34 Addresses. All..., Economic Regulatory Administration, Department of Energy, 2000 M Street, NW., Washington, DC 20461, and...

  14. History Forum Addresses Creation/Evolution Controversy.

    ERIC Educational Resources Information Center

    Schweinsberg, John

    1997-01-01

    A series of programs entitled Creationism and Evolution: The History of a Controversy was presented at the University of Alabama in Huntsville. The controversy was addressed from an historical and sociological, rather than a scientific perspective. Speakers addressed the evolution of scientific creationism, ancient texts versus sedimentary rocks…

  15. Public Address Systems. Specifications - Installation - Operation.

    ERIC Educational Resources Information Center

    Palmer, Fred M.

    Provisions for public address in new construction of campus buildings (specifications, installations, and operation of public address systems), are discussed in non-technical terms. Consideration is given to microphones, amplifiers, loudspeakers and the placement and operation of various different combinations. (FS)

  16. 40 CFR 80.174 - Addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 16 2011-07-01 2011-07-01 false Addresses. 80.174 Section 80.174... FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.174 Addresses. (a) The detergent additive sample required under § 80.161(b)(2) shall be sent to: Manager, Fuels and Technical Analysis Group,...

  17. 7 CFR 1730.3 - RUS addresses.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 11 2014-01-01 2014-01-01 false RUS addresses. 1730.3 Section 1730.3 Agriculture Regulations of the Department of Agriculture (Continued) RURAL UTILITIES SERVICE, DEPARTMENT OF AGRICULTURE ELECTRIC SYSTEM OPERATIONS AND MAINTENANCE General § 1730.3 RUS addresses. (a) Persons wishing to obtain forms referred to in this part...

  18. Forms of Address in Chilean Spanish

    ERIC Educational Resources Information Center

    Bishop, Kelley; Michnowicz, Jim

    2010-01-01

    The present investigation examines possible social and linguistic factors that influence forms of address used in Chilean Spanish with various interlocutors. A characteristic of the Spanish of Chile is the use of a variety of forms of address for the second person singular, "tu", "vos", and "usted", with corresponding verb conjugations (Lipski…

  19. 40 CFR 374.6 - Addresses.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 28 2014-07-01 2014-07-01 false Addresses. 374.6 Section 374.6 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND COMMUNITY RIGHT-TO-KNOW PROGRAMS PRIOR NOTICE OF CITIZEN SUITS § 374.6 Addresses. Administrator, U.S. Environmental Protection Agency, 1200...

  20. 34 CFR 674.44 - Address searches.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 3 2010-07-01 2010-07-01 false Address searches. 674.44 Section 674.44 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If...

  1. 34 CFR 674.44 - Address searches.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 34 Education 3 2013-07-01 2013-07-01 false Address searches. 674.44 Section 674.44 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If...

  2. 34 CFR 674.44 - Address searches.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 3 2011-07-01 2011-07-01 false Address searches. 674.44 Section 674.44 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If...

  3. 34 CFR 674.44 - Address searches.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 34 Education 3 2014-07-01 2014-07-01 false Address searches. 674.44 Section 674.44 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If...

  4. 34 CFR 674.44 - Address searches.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 3 2012-07-01 2012-07-01 false Address searches. 674.44 Section 674.44 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If...

  5. Image compression using address-vector quantization

    NASA Astrophysics Data System (ADS)

    Nasrabadi, Nasser M.; Feng, Yushu

    1990-12-01

    A novel vector quantization scheme, the address-vector quantizer (A-VQ), is proposed which exploits the interblock correlation by encoding a group of blocks together using an address-codebook (AC). The AC is a set of address-codevectors (ACVs), each representing a combination of addresses or indices. Each element of the ACV is an address of an entry in the LBG-codebook, representing a vector-quantized block. The AC consists of an active (addressable) region and an inactive (nonaddressable) region. During encoding the ACVs in the AC are reordered adaptively to bring the most probable ACVs into the active region. When encoding an ACV, the active region is checked, and if such an address combination exists, its index is transmitted to the receiver. Otherwise, the address of each block is transmitted individually. The SNR of the images encoded by the A-VQ method is the same as that of a memoryless vector quantizer, but the bit rate is by a factor of approximately two.

  6. Approaches for Resolving Dynamic IP Addressing.

    ERIC Educational Resources Information Center

    Foo, Schubert; Hui, Siu Cheung; Yip, See Wai; He, Yulan

    1997-01-01

    A problem with dynamic Internet protocol (IP) addressing arises when the Internet connection is through an Internet provider since the IP address is allocated only at connection time. This article examines a number of online and offline methods for resolving the problem. Suggests dynamic domain name system (DNS) and directory service look-up are…

  7. Tradition and Change in Swedish Address Forms.

    ERIC Educational Resources Information Center

    Mitchell, Stephen A.

    In most European languages, choice of address form classifies the relation between speakers. The first theoretical framework for analyzing address form usage was established by Brown and Gilman (1960) in their investigation of the semantics of pronoun use in a wide variety of Indo-European languages, which concluded that Europeans use the informal…

  8. 7 CFR 504.5 - Address.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 6 2014-01-01 2014-01-01 false Address. 504.5 Section 504.5 Agriculture Regulations... USER FEES § 504.5 Address. Deposits of and requests for microbial patent cultures should be directed to.... University St., Peoria, Illinois 61604; (309) 685-4011....

  9. 7 CFR 504.5 - Address.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 6 2012-01-01 2012-01-01 false Address. 504.5 Section 504.5 Agriculture Regulations... USER FEES § 504.5 Address. Deposits of and requests for microbial patent cultures should be directed to.... University St., Peoria, Illinois 61604; (309) 685-4011....

  10. 7 CFR 504.5 - Address.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 6 2010-01-01 2010-01-01 false Address. 504.5 Section 504.5 Agriculture Regulations... USER FEES § 504.5 Address. Deposits of and requests for microbial patent cultures should be directed to.... University St., Peoria, Illinois 61604; (309) 685-4011....

  11. 7 CFR 504.5 - Address.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 6 2011-01-01 2011-01-01 false Address. 504.5 Section 504.5 Agriculture Regulations... USER FEES § 504.5 Address. Deposits of and requests for microbial patent cultures should be directed to.... University St., Peoria, Illinois 61604; (309) 685-4011....

  12. 7 CFR 504.5 - Address.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 6 2013-01-01 2013-01-01 false Address. 504.5 Section 504.5 Agriculture Regulations... USER FEES § 504.5 Address. Deposits of and requests for microbial patent cultures should be directed to.... University St., Peoria, Illinois 61604; (309) 685-4011....

  13. 25 CFR 2.14 - Record address.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Record address. 2.14 Section 2.14 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR PROCEDURES AND PRACTICE APPEALS FROM ADMINISTRATIVE ACTIONS § 2.14 Record address. (a) Every interested party who files a document in connection with an...

  14. 25 CFR 2.14 - Record address.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Record address. 2.14 Section 2.14 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR PROCEDURES AND PRACTICE APPEALS FROM ADMINISTRATIVE ACTIONS § 2.14 Record address. (a) Every interested party who files a document in connection with an...

  15. Laser Propulsion Standardization Issues

    SciTech Connect

    Scharring, Stefan; Eckel, Hans-Albert; Roeser, Hans-Peter; Sinko, John E.; Sasoh, Akihiro

    2010-10-08

    It is a relevant issue in the research on laser propulsion that experimental results are treated seriously and that meaningful scientific comparison is possible between groups using different equipment and measurement techniques. However, critical aspects of experimental measurements are sparsely addressed in the literature. In addition, few studies so far have the benefit of independent confirmation by other laser propulsion groups. In this paper, we recommend several approaches towards standardization of published laser propulsion experiments. Such standards are particularly important for the measurement of laser ablation pulse energy, laser spot area, imparted impulse or thrust, and mass removal during ablation. Related examples are presented from experiences of an actual scientific cooperation between NU and DLR. On the basis of a given standardization, researchers may better understand and contribute their findings more clearly in the future, and compare those findings confidently with those already published in the laser propulsion literature. Relevant ISO standards are analyzed, and revised formats are recommended for application to laser propulsion studies.

  16. Surface emitting laser technology and its application to the space radiation environment

    SciTech Connect

    Carson, R.F.; Choquette, K.D.; Hou, Hong, Q.

    1997-09-01

    Present and future space-based applications such as sensors, low-weight and low-power data links for satellites, communication between electromagnetically-shielded modules, and short-distance cross-links within satellite constellations may benefit from the inclusion of small, low-power, and high-efficiency lasers such as the recently-developed Vertical Cavity Surface-Emitting Laser (VCSEL). Many factors influence the application of these devices to space. Temperature response, operational lifetime and reliability, and power consumption are all important considerations for space applications. In addition, the space radiation environments must be considered. In this work, the effects of ionizing radiation on VCSELs are studied with an emphasis on proton damage, and with comparisons to related neutron and gamma-induced phenomena. The influence of proton irradiation is studied in-depth for selected VCSEL structures by the use of an ion microbeam. The experiments indicate that VCSELs exhibit much less threshold current shift for a given radiation dose, compared to the more traditional edge-emitting semiconductor lasers, but that self-heating is a more important consideration for VCSELs. The high current densities associated with VCSELs also lead to a strong influence from forward-bias annealing. These effects are common to various VCSEL types (780 nm and 850 nm) and their magnitude at a given dose is strongly dependent on device size. This indicates that, while VCSELs appear to be very insensitive to ionizing radiation when compared with alternative technologies, there are a number of factors that must be taken into account when optimizing for the space environment.

  17. 7 CFR 1730.3 - RUS addresses.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... ELECTRIC SYSTEM OPERATIONS AND MAINTENANCE General § 1730.3 RUS addresses. (a) Persons wishing to obtain... assigned RUS General Field Representative (GFR) or such other office as designated by RUS....

  18. 21 CFR 600.2 - Mailing addresses.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... BIOLOGICAL PRODUCTS: GENERAL General Provisions § 600.2 Mailing addresses. (a) Licensed biological products... applications (BLAs) and their amendments and supplements, adverse experience reports, biological product deviation reports, fatality reports, and other correspondence. Biological products samples must not be...

  19. 21 CFR 600.2 - Mailing addresses.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... BIOLOGICAL PRODUCTS: GENERAL General Provisions § 600.2 Mailing addresses. (a) Licensed biological products... applications (BLAs) and their amendments and supplements, adverse experience reports, biological product deviation reports, fatality reports, and other correspondence. Biological products samples must not be...

  20. 21 CFR 600.2 - Mailing addresses.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... BIOLOGICAL PRODUCTS: GENERAL General Provisions § 600.2 Mailing addresses. (a) Licensed biological products... applications (BLAs) and their amendments and supplements, adverse experience reports, biological product deviation reports, fatality reports, and other correspondence. Biological products samples must not be...

  1. Addressing Your Child's Weight at the Doctor

    MedlinePlus

    ... a Healthy Heart Healthy Kids Our Kids Programs Childhood Obesity What is childhood obesity? Overweight in Children BMI in Children Is Childhood Obesity an Issue in Your Home? Addressing your Child's ...

  2. 7 CFR 1730.3 - RUS addresses.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... ELECTRIC SYSTEM OPERATIONS AND MAINTENANCE General § 1730.3 RUS addresses. (a) Persons wishing to obtain... assigned RUS General Field Representative (GFR) or such other office as designated by RUS....

  3. 7 CFR 1730.3 - RUS addresses.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ELECTRIC SYSTEM OPERATIONS AND MAINTENANCE General § 1730.3 RUS addresses. (a) Persons wishing to obtain... assigned RUS General Field Representative (GFR) or such other office as designated by RUS....

  4. 7 CFR 1730.3 - RUS addresses.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... ELECTRIC SYSTEM OPERATIONS AND MAINTENANCE General § 1730.3 RUS addresses. (a) Persons wishing to obtain... assigned RUS General Field Representative (GFR) or such other office as designated by RUS....

  5. Laser cooling of solids

    NASA Astrophysics Data System (ADS)

    Nemova, Galina; Kashyap, Raman

    2010-08-01

    Laser cooling of solids, sometimes also known as optical refrigeration, is a fast developing area of optical science, investigating the interaction of light with condensed matter. Apart from being of fundamental scientific interest, this topic addresses a very important practical issue: design and construction of laser pumped solid-state cryocoolers, which are compact, free from mechanical vibrations, moving parts, fluids and can cause only low electromagnetic interference in the cooled area. The optical cryocooler has a broad area of applications such as in the development of magnetometers for geophysical sensors, in biomedical sensing and can be beneficial for satellite instrumentations and small sensors, where compactness and the lack of vibrations are very important. Simply, a laser cooler works on the conversion of low energy pump photons into high-energy anti-Stokes fluorescence photons by extracting some of the phonons (heat energy) in a material. That is, the process of laser cooling of solids is based on anti-Stokes fluorescence also known as luminescence upconversion, when light quanta in the red tail of the absorption spectrum are absorbed from a pump laser, and blue-shifted photons are spontaneously emitted. The extra energy extracted from the solid-state lattice in the form of the phonons is the quanta of vibrational energy which generates heat. The idea to cool solids with anti-Stokes fluorescence was proposed in 1929 by Peter Pringsheim and first demonstrated experimentally by Epstein's research team in 1995. In 1999, Steven Bowman proposed to use the optical refrigeration by anti-Stokes fluorescence within the laser medium to balance the heat generated by the Stokes shifted stimulated emission in a high-power solid-state bulk laser. Such a laser without internal heating named radiation-balanced or athermal laser was experimentally demonstrated for the first time in 2002. At the present time laser cooling of solids can be largely divided into three

  6. Cost-effective telecom/datacom semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Chen, Nong; Chen, Dick T. R.; Hsin, Wei; Chen, Steven Bo; Xiong, Frank; Erlig, Hernan; Chen, Paul; Yeh, Xian-li; Scott, David C.; Sherer, Axel

    2007-11-01

    The recent development of semiconductor laser technologies for cost-effective telecom/datacom applications is reviewed in details in this paper. This includes the laser design, laser chip technology, laser packaging technology and other low cost lasers (chip + packaging). Some design and simulation examples in Archcom laser production are described first. A latest trend in the wafer scale testing/characterization/screening technology for low cost semiconductor laser mass production is discussed then. An advanced long wavelength high power single mode surface emitting laser with wafer scale characterization using our unique mask free focused ion beam (FIB) etching technology is also demonstrated. Detailed descriptions on our wide temperature range (-50 °C to +105 °C) G-PON distributed feedback (DFB) semiconductor lasers with high performance and low cost wafer design are included. Cost reduction innovations in laser package with our beam profile improved laser and optical feedback insensitive (OFBI) laser are also addressed.

  7. Laser Welding in Electronic Packaging

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The laser has proven its worth in numerous high reliability electronic packaging applications ranging from medical to missile electronics. In particular, the pulsed YAG laser is an extremely flexible and versatile too] capable of hermetically sealing microelectronics packages containing sensitive components without damaging them. This paper presents an overview of details that must be considered for successful use of laser welding when addressing electronic package sealing. These include; metallurgical considerations such as alloy and plating selection, weld joint configuration, design of optics, use of protective gases and control of thermal distortions. The primary limitations on use of laser welding electronic for packaging applications are economic ones. The laser itself is a relatively costly device when compared to competing welding equipment. Further, the cost of consumables and repairs can be significant. These facts have relegated laser welding to use only where it presents a distinct quality or reliability advantages over other techniques of electronic package sealing. Because of the unique noncontact and low heat inputs characteristics of laser welding, it is an ideal candidate for sealing electronic packages containing MEMS devices (microelectromechanical systems). This paper addresses how the unique advantages of the pulsed YAG laser can be used to simplify MEMS packaging and deliver a product of improved quality.

  8. Mrs. Chandrasekhar addresses the media in TRW Media Hospitality Tent

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Mrs. Lalitha Chandrasekhar (at podium), wife of the late Indian- American Nobel Laureate Subrahmanyan Chandrasekhar, addresses the media and other invited guests in the TRW Media Hospitality Tent at the NASA Press Site at KSC. Other participants in the program (seated facing the audience, left to right) are the winners of the contest to rename the telescope, Jatila van der Veen, academic coordinator and lecturer, Physics Dept., University of Santa Barbara, Calif., and Tyrel Johnson, high school student, Laclede, Idaho; Joanne Maguire, vice-president and general manager, TRW Space & Laser Programs Division; and Dr. Alan Bunner, Science Program Director, Structure and Evolution of the Universe, Office of Space Science, NASA Headquarters, Washington, D.C. The name 'Chandra,' a shortened version of Chandrasekhar, was the name the Nobel Laureate preferred among friends and colleagues. 'Chandra' also means 'Moon' or 'luminous' in Sanskrit. The observatory is scheduled to be launched aboard Columbia on Space Shuttle mission STS-93.

  9. 46 CFR 67.113 - Managing owner designation; address; requirement to report change of address.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Managing owner designation; address; requirement to... Required for Vessel Documentation § 67.113 Managing owner designation; address; requirement to report change of address. The owner of each vessel must designate a managing owner on the Application...

  10. 46 CFR 67.113 - Managing owner designation; address; requirement to report change of address.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Managing owner designation; address; requirement to... Required for Vessel Documentation § 67.113 Managing owner designation; address; requirement to report change of address. The owner of each vessel must designate a managing owner on the Application...

  11. 46 CFR 67.113 - Managing owner designation; address; requirement to report change of address.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Managing owner designation; address; requirement to... Required for Vessel Documentation § 67.113 Managing owner designation; address; requirement to report change of address. The owner of each vessel must designate a managing owner on the Application...

  12. 46 CFR 67.113 - Managing owner designation; address; requirement to report change of address.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Managing owner designation; address; requirement to... Required for Vessel Documentation § 67.113 Managing owner designation; address; requirement to report change of address. The owner of each vessel must designate a managing owner on the Application...

  13. 46 CFR 67.113 - Managing owner designation; address; requirement to report change of address.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Managing owner designation; address; requirement to... Required for Vessel Documentation § 67.113 Managing owner designation; address; requirement to report change of address. The owner of each vessel must designate a managing owner on the Application...

  14. 0.52-11.86 Gbit/s OFDM modulation for power-sharing VLC transmission by using VCSEL laser.

    PubMed

    Yeh, Chien-Hung; Lu, I-Cheng

    2016-09-01

    In this paper, we propose employing a 682 nm vertical-cavity surface-emitting laser (VCSEL) with 1 GHz bandwidth for high-speed and power-sharing wireless visible light communication (VLC) in the different transmission distances of 2 to 5 m. In the measurement, the data rate of 0.52 to 11.86 Gbit/s (0.44 to 10.8 Gbit/s in a net data rate) can be achieved by using spectral-efficient orthogonal frequency division multiplexing (OFDM) modulation with bit-loading algorithm. Therefore, 4- to 256-quadrature amplitude modulations (QAMs) are employed simultaneously in the modulation bandwidth for VCSEL-based VLC. The proposed power-sharing VLC system can be divided to four end-users, when three beam splitters (BSs) are used simultaneously. Moreover, all of the measured bit error rates (BERs) are below the forward error correction (FEC) threshold (BER = 3.8 × 10-3). PMID:27607714

  15. Laser Launch-The Second Wave

    NASA Astrophysics Data System (ADS)

    Kare, Jordin T.

    2003-05-01

    In the spring of 1986, a Workshop on Laser Propulsion was held to discuss the feasibility of using large free electron lasers to launch payloads into Earth orbit. This workshop kicked off a four-year program, supported by the U.S. Strategic Defense Initiative Organization (SDIO), to develop laser propulsion technology. This talk reviews the concepts addressed by the SDIO Laser Propulsion Program, and the results of both modeling and experiments on double-pulse planar ablative thrusters, which remain a promising approach to laser launch. Other program topics to be discussed include trajectory and system modeling, and air-breathing thruster and vehicle concepts.

  16. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2002-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. The beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being recombined with the first portion after a delay before injection into the ignitor laser. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones.

  17. Fs-laser processing of polydimethylsiloxane

    SciTech Connect

    Atanasov, Petar A. Nedyalkov, Nikolay N.; Valova, Eugenia I.; Georgieva, Zhenya S.; Armyanov, Stefan A.; Kolev, Konstantin N.; Amoruso, Salvatore; Wang, Xuan; Bruzzese, Ricardo; Sawczak, Miroslaw; Śliwiński, Gerard

    2014-07-14

    We present an experimental analysis on surface structuring of polydimethylsiloxane films with UV (263 nm) femtosecond laser pulses, in air. Laser processed areas are analyzed by optical microscopy, SEM, and μ-Raman spectroscopy. The laser-treated sample shows the formation of a randomly nanostructured surface morphology. μ-Raman spectra, carried out at both 514 and 785 nm excitation wavelengths, prior and after laser treatment allow evidencing the changes in the sample structure. The influence of the laser fluence on the surface morphology is studied. Finally, successful electro-less metallization of the laser-processed sample is achieved, even after several months from the laser-treatment contrary to previous observation with nanosecond pulses. Our findings address the effectiveness of fs-laser treatment and chemical metallization of polydimethylsiloxane films with perspective technological interest in micro-fabrication devices for MEMS and nano-electromechanical systems.

  18. Shared address collectives using counter mechanisms

    SciTech Connect

    Blocksome, Michael; Dozsa, Gabor; Gooding, Thomas M; Heidelberger, Philip; Kumar, Sameer; Mamidala, Amith R; Miller, Douglas

    2014-02-18

    A shared address space on a compute node stores data received from a network and data to transmit to the network. The shared address space includes an application buffer that can be directly operated upon by a plurality of processes, for instance, running on different cores on the compute node. A shared counter is used for one or more of signaling arrival of the data across the plurality of processes running on the compute node, signaling completion of an operation performed by one or more of the plurality of processes, obtaining reservation slots by one or more of the plurality of processes, or combinations thereof.

  19. Initiative Addresses Subsurface Energy and Environment Problems

    NASA Astrophysics Data System (ADS)

    Bodvarsson, Gudmundur S.; Majer, Ernest L.; Wang, Joseph S. Y.; Colwell, Frederick; Redden, George

    2006-01-01

    Members of the geoscience community are cooperating in conceptualizing fundamental, crosscutting research to address major obstacles to solving energy and environmental problems related to the subsurface, through the SECUREarth initiative, which began in 2004. Addressing problems, such as reliable nuclear waste storage and safe carbon dioxide (CO2) sequestration, are critical to maintaining an economical and safe energy supply and clean environment. A recent workshop in Golden, Colo., helped to further the development of the SECUREarth (Scientific Energy/Environmental Crosscutting Underground Research for Urgent Solutions to Secure the Earth's Future) initiative by identifying the key scientific challenges in the geosciences, as well as to target possible approaches for overcoming roadblocks.

  20. Frequency addressable beams for land mobile communications

    NASA Technical Reports Server (NTRS)

    Thompson, J. D.; Dubellay, G. G.

    1988-01-01

    Satellites used for mobile communications need to serve large numbers of small, low cost terminals. The most important parameters affecting the capacity of such systems are the satellite equivalent isotropically radiated power (EIRP) and gain to noise temperature ratio (G/T) and available bandwidth. Satellites using frequency addressed beams provide high EIRP and G/T with high-gain antenna beams that also permit frequency reuse over the composite coverage area. Frequency addressing is easy to implement and compatible with low-cost terminals and offers higher capacity than alternative approaches.

  1. Cheaper Adjoints by Reversing Address Computations

    DOE PAGESBeta

    Hascoët, L.; Utke, J.; Naumann, U.

    2008-01-01

    The reverse mode of automatic differentiation is widely used in science and engineering. A severe bottleneck for the performance of the reverse mode, however, is the necessity to recover certain intermediate values of the program in reverse order. Among these values are computed addresses, which traditionally are recovered through forward recomputation and storage in memory. We propose an alternative approach for recovery that uses inverse computation based on dependency information. Address storage constitutes a significant portion of the overall storage requirements. An example illustrates substantial gains that the proposed approach yields, and we show use cases in practical applications.

  2. Micromotion based single-qubit addressing with trapped-ions

    NASA Astrophysics Data System (ADS)

    Akerman, Nitzan; Navon, Nir; Kotler, Shlomi; Glickman, Yinnon; Almog, Ido; Ozeri, Roee

    2013-05-01

    Individual-particle addressing is a necessary capability in many quantum information experiments. For example, characterization of multi-qubit operations with quantum process tomography (QPT). We propose and demonstrate a scheme that exploits the inhomogeneous excess micromotion in ion trap to address single-qubits in a chain of several ion-qubits, separated by only few microns. The scheme uses a laser field which is resonant with the micromotion sideband of a narrow optical quadrupole transition and acts as a dressing field with a spatially-dependent coupling along the chain. As a consequence, the level spacing of each ion, in the dressed state picture, becomes position dependent and individual ions can be spectrally separated. We have demonstrated Individual Rabi flops with 85% fidelity in a three-ion chain. For the case of only two ions, the coupling can be tailored to vanish on one of the two. This allows preparing any two-qubit product state as well as completing state tomography without direct spatially-selective imaging. We demonstrate full QPT for two-qubit Sørensen-Mølmer entangling interaction (Bell-state preparation fidelity of 98%) which has not been process-analyzed yet. Our tomography resulted process fidelity of 92%. N. Navon et al. arXiv:1210.7336 (1012).

  3. Lasers of All Sizes

    NASA Astrophysics Data System (ADS)

    Balcou, Philippe; Forget, Sébastien Robert-Philip, Isabelle

    2015-10-01

    * Introduction * The Laser in All Its Forms * Gas lasers * Dye lasers * Solid-state lasers * Lasers for Every Taste * The rise of lasers * Lasers of all sizes * The colors of the rainbow... and beyond * Shorter and shorter lasers * Increasingly powerful lasers * Lasers: A Universal Tool? * Cutting, welding, and cleaning * Communicating * Treating illnesses * Measuring * Supplying energy? * Entertaining * Understanding * Conclusion

  4. Coherent laser vision system

    SciTech Connect

    Sebastion, R.L.

    1995-10-01

    The Coherent Laser Vision System (CLVS) is being developed to provide precision real-time 3D world views to support site characterization and robotic operations and during facilities Decontamination and Decommissioning. Autonomous or semiautonomous robotic operations requires an accurate, up-to-date 3D world view. Existing technologies for real-time 3D imaging, such as AM laser radar, have limited accuracy at significant ranges and have variability in range estimates caused by lighting or surface shading. Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no-moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic to coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.

  5. Federal Offices That Address Women's Issues.

    ERIC Educational Resources Information Center

    Weber, Patricia A.; And Others

    This directory contains a listing of federal offices that address women's issues. Among the departments and agencies included are: the executive branch and the executive agencies departments of agriculture, commerce, defense (Air Force, Army, Coast Guard, Marine Corps, National Guard and Navy), education, health and human services, housing and…

  6. Preservice Educators' Confidence in Addressing Sexuality Education

    ERIC Educational Resources Information Center

    Wyatt, Tammy Jordan

    2009-01-01

    This study examined 328 preservice educators' level of confidence in addressing four sexuality education domains and 21 sexuality education topics. Significant differences in confidence levels across the four domains were found for gender, academic major, sexuality education philosophy, and sexuality education knowledge. Preservice educators…

  7. 50 CFR 228.8 - Mailing address.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Mailing address. 228.8 Section 228.8 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION... the Presiding Officer, c/o Assistant Administrator, National Marine Fisheries Service, 1315...

  8. Latitude and Longitude. AIR Presidential Address.

    ERIC Educational Resources Information Center

    Chaffee, Ellen Earle

    This speech addresses the problem of higher education's response to the forces of change and argues for a reinventing of higher education rather than repeatedly amending core teaching and research activities to fit new social and economic situations. Three higher education organizational dynamics (recruitment, budgeting, and handling outside…

  9. Violence Goes to School. Keynote Address.

    ERIC Educational Resources Information Center

    Levin, Jack

    1998-01-01

    Increased juvenile violence in schools has led to suggested solutions that are politically expedient but fail to address what makes violence so appealing. Instead of school uniforms, conflict resolution programs, or media rating systems, a grass roots approach of alternative programs, parental involvement, and youth support systems could repair…

  10. 40 CFR 80.174 - Addresses.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.174 Addresses. (a) The detergent additive sample..., 2565 Plymouth Road, Ann Arbor, Michigan 48105. (b) Other detergent registration and certification data, and certain other information which may be specified in this subpart, shall be sent to:...

  11. Addressing Gender Differences in Young Adolescents.

    ERIC Educational Resources Information Center

    Butler, Deborah A.; Manning, M. Lee

    The current interest in identifying gender differences in young adolescents suggests a need to focus on how gender differences affect teaching and learning situations and on how middle level school educators can address these differences. This book explains what gender differences are, how gender differences affect learning, how both girls and…

  12. Addressing South Africa's Engineering Skills Gaps

    ERIC Educational Resources Information Center

    Hall, Jonathan; Sandelands, Eric

    2009-01-01

    Purpose: This paper aims to provide a case study of how engineering skills gaps are being addressed by Murray & Roberts in South Africa. Design/methodology/approach: The paper focuses on skills challenges in South Africa from a reflective practitioner perspective, exploring a case example from an industry leader. Findings: The paper explores how…

  13. 76 FR 80903 - Mandatory Declassification Review Addresses

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-27

    ... of the Secretary Mandatory Declassification Review Addresses AGENCY: Department of Defense. ACTION... Declassification Review requests may be sent. This notice benefits the public in advising them where to send such requests for declassification review. FOR FURTHER INFORMATION CONTACT: Mr. Robert Storer, (571)...

  14. Registering Names and Addresses for Information Technology.

    ERIC Educational Resources Information Center

    Knapp, Arthur A.

    The identification of administrative authorities and the development of associated procedures for registering and accessing names and addresses of communications data systems are considered in this paper. It is noted that, for data communications systems using standards based on the Open Systems Interconnection (OSI) Reference Model specified by…

  15. 50 CFR 228.8 - Mailing address.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 50 Wildlife and Fisheries 11 2013-10-01 2013-10-01 false Mailing address. 228.8 Section 228.8 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION... the Presiding Officer, c/o Assistant Administrator, National Marine Fisheries Service, 1315...

  16. Naming and Address in Afghan Society.

    ERIC Educational Resources Information Center

    Miran, M. Alam

    Forms of address in Afghan society reflect the relationships between the speakers as well as the society's structure. In Afghan Persian, or Dari, first, second, and last names have different semantic dimensions. Boys' first names usually consist of two parts or morphemes, of which one may be part of the father's name. Girls' names usually consist…

  17. Addressing Student Debt in the Classroom

    ERIC Educational Resources Information Center

    Perkins, David; Johnston, Tim; Lytle, Rick

    2016-01-01

    Student debt is a national concern. The authors address debt in the classroom to enhance students' understanding of the consequences of debt and the need for caution when financing their education. However, student feedback indicates this understanding has a delayed effect on borrowing behavior and underscores the importance of making difficult…

  18. Native Women at Risk: Addressing Cancer Prevention.

    ERIC Educational Resources Information Center

    Thiemann, Kay M. B.

    1994-01-01

    Discusses outcomes of a conference that brought together representatives from Indian tribes, state health departments, the Indian Health Service, the Mayo Clinic, and the American Cancer Society, to address the high rate of cervical cancer among American Indian women. Describes barriers to health care and plans to promote cancer screening among…

  19. Autocheck: Addressing the Problem of Rural Transportation.

    ERIC Educational Resources Information Center

    Payne, Guy A.

    This paper describes a project implemented by a social worker from the Glynn County School District in rural Georgia to address transportation problems experienced by students and their families. The project aims to assist families who are unable to keep appointments or attend other important events due to unreliable transportation. A county needs…

  20. Problem Solvers: Solutions--The Inaugural Address

    ERIC Educational Resources Information Center

    Dause, Emily

    2014-01-01

    Fourth graders in Miss Dause's and Mrs. Hicks's mathematics classes at South Mountain Elementary School in Dillsburg, Pennsylvania, worked with the data from the Inauagural Address problem that was previously published published in the February 2013 issue of "Teaching Children Mathematics". This activity allowed students to…

  1. EMAIL -- E-mail address searching

    NASA Astrophysics Data System (ADS)

    Bly, M. J.; Mellor, G. R.

    One of the most common activities on networked computers is the sending and receiving of personal electronic mail (email). Starlink nodes are connected to the worldwide Internet network. This document describes how to find email addresses to communicate with other astronomers and astronomy groups in the UK and the rest of the world.

  2. Address Systems in "The Plum Plum Pickers"

    ERIC Educational Resources Information Center

    Geuder, Patricia A.

    1975-01-01

    The address systems in Raymond Barrio's "The Plum Plum Pickers" imply sociolinguistic differences between the Chicano and the Anglo characters. The kinds of sociolinguistic situations, the number of dyadic patterns, and the quantity of the dyadic patterns strongly suggest the differences. (Author)

  3. Addressing Issues Related to Technology and Engineering

    ERIC Educational Resources Information Center

    Technology Teacher, 2008

    2008-01-01

    This article presents an interview with Michael Hacker and David Burghardt, codirectors of Hoftra University's Center for Technological Literacy. Hacker and Burghardt address issues related to technology and engineering. They argue that teachers need to be aware of the problems kids are facing, and how to present these problems in an engaging…

  4. How Sociology Texts Address Gun Control

    ERIC Educational Resources Information Center

    Tonso, William R.

    2004-01-01

    William R. Tonso has chosen an issue that he knows something about to examine how sociology textbooks address controversy. Appealing for gun control is fashionable, but it is at odds with a fondness that ordinary Americans have for their firearms--one that is supported by a growing body of research on deterrence to crime. There are two sides to…

  5. 40 CFR 374.6 - Addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 28 2011-07-01 2011-07-01 false Addresses. 374.6 Section 374.6 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND... Administrator, Region VII, U.S. Environmental Protection Agency, 726 Minnesota Avenue, Kansas City, KS...

  6. 40 CFR 374.6 - Addresses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 27 2010-07-01 2010-07-01 false Addresses. 374.6 Section 374.6 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SUPERFUND, EMERGENCY PLANNING, AND... Administrator, Region VII, U.S. Environmental Protection Agency, 726 Minnesota Avenue, Kansas City, KS...

  7. Opening Address of Chairman Michael Pertschuk.

    ERIC Educational Resources Information Center

    Pertschuk, Michael

    Presented to a symposium sponsored by the Federal Trade Commission (FTC) to consider some of the issues involved in the continuing growth of a few large companies in the field of communication, this address cites statements of concern, made by the Supreme Court and by some periodicals, that excessive concentrations of power threaten First…

  8. 37 CFR 301.2 - Official addresses.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Section 301.2 Patents, Trademarks, and Copyrights COPYRIGHT ROYALTY BOARD, LIBRARY OF CONGRESS GENERAL...., and be addressed as follows: Copyright Royalty Board, Library of Congress, James Madison Memorial... Royalty Board, Library of Congress, James Madison Memorial Building, 101 Independence Avenue,...

  9. 37 CFR 301.2 - Official addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Section 301.2 Patents, Trademarks, and Copyrights COPYRIGHT ROYALTY BOARD, LIBRARY OF CONGRESS GENERAL...., and be addressed as follows: Copyright Royalty Board, Library of Congress, James Madison Memorial... Royalty Board, Library of Congress, James Madison Memorial Building, 101 Independence Avenue,...

  10. 37 CFR 301.2 - Official addresses.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Section 301.2 Patents, Trademarks, and Copyrights COPYRIGHT ROYALTY BOARD, LIBRARY OF CONGRESS GENERAL...., and be addressed as follows: Copyright Royalty Board, Library of Congress, James Madison Memorial... Royalty Board, Library of Congress, James Madison Memorial Building, 101 Independence Avenue,...

  11. 37 CFR 301.2 - Official addresses.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Section 301.2 Patents, Trademarks, and Copyrights COPYRIGHT ROYALTY BOARD, LIBRARY OF CONGRESS GENERAL...., and be addressed as follows: Copyright Royalty Board, Library of Congress, James Madison Memorial... Royalty Board, Library of Congress, James Madison Memorial Building, 101 Independence Avenue,...

  12. The Conversational Frame in Public Address.

    ERIC Educational Resources Information Center

    Branham, Robert James; Pearce, W. Barnett

    1996-01-01

    Explores the diverse forms and motives of the conversational frame in public address. Argues that, by framing their remarks and transactions with their listeners as conversational, orators may attempt to reconstruct or seem to reconstruct speaker-audience relationships and to position themselves and their audiences within networks of reciprocal…

  13. Rational Rhymes for Addressing Common Childhood Issues

    ERIC Educational Resources Information Center

    Warren, Jeffrey M.

    2011-01-01

    Music-based interventions are valuable tools counselors can use when working with children. Specific types of music-based interventions, such as songs or rhymes, can be especially pertinent in addressing the thoughts, feelings, and behaviors of children. Rational-emotive behavior therapy (REBT) provides a therapeutic framework that encourages…

  14. Chemical Address Tags of Fluorescent Bioimaging Probes

    PubMed Central

    Shedden, Kerby; Rosania, Gus R.

    2010-01-01

    Chemical address tags can be defined as specific structural features shared by a set of bioimaging probes having a predictable influence on cell-associated visual signals obtained from these probes. Here, using a large image dataset acquired with a high content screening instrument, machine vision and cheminformatics analysis have been applied to reveal chemical address tags. With a combinatorial library of fluorescent molecules, fluorescence signal intensity, spectral, and spatial features characterizing each one of the probes' visual signals were extracted from images acquired with the three different excitation and emission channels of the imaging instrument. With multivariate regression, the additive contribution from each one of the different building blocks of the bioimaging probes towards each measured, cell-associated image-based feature was calculated. In this manner, variations in the chemical features of the molecules were associated with the resulting staining patterns, facilitating quantitative, objective analysis of chemical address tags. Hierarchical clustering and paired image-cheminformatics analysis revealed key structure-property relationships amongst many building blocks of the fluorescent molecules. The results point to different chemical modifications of the bioimaging probes that can exert similar (or different) effects on the probes' visual signals. Inspection of the clustered structures suggests intramolecular charge migration or partial charge distribution as potential mechanistic determinants of chemical address tag behavior. PMID:20104576

  15. Comprehensive Planning To Address Homelessness. City Initiatives.

    ERIC Educational Resources Information Center

    Zawisza, Kris

    This packet contains documents that provide information about the planning and implementation of a comprehensive plan to address homelessness in cities throughout the U.S. Information on the following components of a comprehensive strategy are included: (1) "Task Forces"; (2) "Assessment Studies"; (3) "Emergency Services"; (4) "Transitional…

  16. 40 CFR 80.174 - Addresses.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... FUELS AND FUEL ADDITIVES Detergent Gasoline § 80.174 Addresses. (a) The detergent additive sample..., 2565 Plymouth Road, Ann Arbor, Michigan 48105. (b) Other detergent registration and certification data, and certain other information which may be specified in this subpart, shall be sent to:...

  17. 40 CFR 98.9 - Addresses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... submitted to the following address: (a) For U.S. mail. Director, Climate Change Division, 1200 Pennsylvania Ave., NW., Mail Code: 6207J, Washington, DC 20460. (b) For package deliveries. Director, Climate Change Division, 1310 L St, NW., Washington, DC 20005....

  18. 40 CFR 98.9 - Addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... submitted to the following address: (a) For U.S. mail. Director, Climate Change Division, 1200 Pennsylvania Ave., NW., Mail Code: 6207J, Washington, DC 20460. (b) For package deliveries. Director, Climate Change Division, 1310 L St, NW., Washington, DC 20005....

  19. 37 CFR 251.1 - Official addresses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Copyright Arbitration Royalty Panels (CARPs) must be addressed as follows: (a) If hand delivered by a... Friday between 8:30 a.m. and 5 p.m. (b) If hand delivered by a commercial courier (excluding Federal...) located at Second and D Street, NE., Washington, DC. The CCAS will accept items from couriers with...

  20. Laser therapy

    MedlinePlus

    ... be used for many medical purposes. Because the laser beam is so small and precise, it allows health care providers to safely treat tissue without injuring the surrounding area. Lasers are often used to: Treat varicose veins Improve ...

  1. Laser microphone

    DOEpatents

    Veligdan, James T.

    2000-11-14

    A microphone for detecting sound pressure waves includes a laser resonator having a laser gain material aligned coaxially between a pair of first and second mirrors for producing a laser beam. A reference cell is disposed between the laser material and one of the mirrors for transmitting a reference portion of the laser beam between the mirrors. A sensing cell is disposed between the laser material and one of the mirrors, and is laterally displaced from the reference cell for transmitting a signal portion of the laser beam, with the sensing cell being open for receiving the sound waves. A photodetector is disposed in optical communication with the first mirror for receiving the laser beam, and produces an acoustic signal therefrom for the sound waves.

  2. Mapping virtual addresses to different physical addresses for value disambiguation for thread memory access requests

    DOEpatents

    Gala, Alan; Ohmacht, Martin

    2014-09-02

    A multiprocessor system includes nodes. Each node includes a data path that includes a core, a TLB, and a first level cache implementing disambiguation. The system also includes at least one second level cache and a main memory. For thread memory access requests, the core uses an address associated with an instruction format of the core. The first level cache uses an address format related to the size of the main memory plus an offset corresponding to hardware thread meta data. The second level cache uses a physical main memory address plus software thread meta data to store the memory access request. The second level cache accesses the main memory using the physical address with neither the offset nor the thread meta data after resolving speculation. In short, this system includes mapping of a virtual address to a different physical addresses for value disambiguation for different threads.

  3. Nonablative lasers.

    PubMed

    Nouri, Keyvan; Rivas, Maria Patricia; Bouzari, Navid; Faghih, Sahar

    2006-06-01

    The trend toward minimally invasive rejuvenation techniques has led to the widespread use of nonablative lasers. Nonablative lasers can be classified in two groups based on their wavelengths: lasers emitting light in the visible range, and those emitting in the infrared range. In this review, different laser and intense pulsed light (IPL) systems are presented and critically discussed along with findings of the studies in the literature. PMID:17173583

  4. Laser driver

    SciTech Connect

    Culpepper, C.F.

    1989-03-14

    A laser driver for a laser diode is described, consisting of: an impedance matched input buffer amplifier to which a modulation signal is applied; and a current source coupled to the output of the impedance matched input buffer amplifier, the output of the current source providing an essentially constant amplitude a.c. current component coupled to drive the laser diode.

  5. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2004-01-13

    Sequenced pulses of light from an excitation laser with at least two resonator cavities with separate output couplers are directed through a light modulator and a first polarzing analyzer. A portion of the light not rejected by the first polarizing analyzer is transported through a first optical fiber into a first ignitor laser rod in an ignitor laser. Another portion of the light is rejected by the first polarizing analyzer and directed through a halfwave plate into a second polarization analyzer. A first portion of the output of the second polarization analyzer passes through the second polarization analyzer to a second, oscillator, laser rod in the ignitor laser. A second portion of the output of the second polarization analyzer is redirected by the second polarization analyzer to a second optical fiber which delays the beam before the beam is combined with output of the first ignitor laser rod. Output of the second laser rod in the ignitor laser is directed into the first ignitor laser rod which was energized by light passing through the first polarizing analyzer. Combined output of the first ignitor laser rod and output of the second optical fiber is focused into a combustible fuel where the first short duration, high peak power pulse from the ignitor laser ignites the fuel and the second long duration, low peak power pulse directly from the excitation laser sustains the combustion.

  6. One Micron Laser Technology Advancements at GSFC

    NASA Technical Reports Server (NTRS)

    Heaps, William S.

    2010-01-01

    This slide presentation reviews the advancements made in one micron laser technology at Goddard Space Flight Center. It includes information about risk factors that are being addressed by GSFC, and overviews of the various programs that GSFC is currently managing that are using 1 micron laser technology.

  7. Investigation of laser polarized xenon magnetic resonance

    NASA Technical Reports Server (NTRS)

    Walsworth, Ronald L.

    1998-01-01

    Ground-based investigations of a new biomedical diagnostic technology: nuclear magnetic resonance of laser polarized noble gas are addressed. The specific research tasks discussed are: (1) Development of a large-scale noble gas polarization system; (2) biomedical investigations using laser polarized noble gas in conventional (high magnetic field) NMR systems; and (3) the development and application of a low magnetic field system for laser polarized noble gas NMR.

  8. Design considerations for a laser-plasma linear collider

    SciTech Connect

    Schroeder, C. B.; Esarey, E.; Geddes, C. G. R.; Toth, Cs.; Leemans, W. P.

    2009-01-22

    Design considerations for a next-generation electron-positron linear collider based on laser-plasma-accelerators are discussed. Several of the advantages and challenges of laser-plasma-based accelerator technology are addressed. An example of the parameters for a 1 TeV laser-plasma-based collider is presented.

  9. A tunable mid-infrared laser source for remote sensing

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.

    1991-01-01

    Many remote sensing needs can be effectively addressed with a tunable laser source in the mid infrared. One potential laser source is an optical parametric oscillator and amplifier system pumped by a near infrared solid state laser. Advantages of such a system and progress made at NASA Langley Research Center to date on such a system are described.

  10. Design considerations for a laser-plasma linear collider

    SciTech Connect

    Schroeder, C. B.; Esarey, E.; Geddes, C. G. R.; Toth, Cs.; Leemans, W. P.

    2008-08-01

    Design considerations for a next-generation electron-positron linear collider based on laser-plasma-accelerators are discussed. Several of the advantages and challenges of laser-plasma based accelerator technology are addressed. An example of the parameters for a 1 TeV laser-plasma based collider is presented.

  11. CW laser pumped emerald laser

    SciTech Connect

    Shand, M.L.; Lai, S.T.

    1984-02-01

    A CW laser-pumped emerald laser is reported. A 34 percent output power slope efficiency is observed with longitudinal pumping by a krypton laser in a nearly concentric cavity. The laser has been tuned from 728.8 to 809.0 nm. Losses in emerald are larger than those of alexandrite determined in a similar cavity. The present data also indicate that the excited state absorption minimum is shifted from that of alexandrite. 13 references.

  12. Increasing hope by addressing clients' outcome expectations.

    PubMed

    Swift, Joshua K; Derthick, Annie O

    2013-09-01

    Addressing clients' outcome expectations is an important clinical process that can lead to a strong therapeutic alliance, more positive treatment outcomes, and decreased rates of premature termination from psychotherapy. Five interventions designed to foster appropriate outcome expectations are discussed, including presenting a convincing treatment rationale, increasing clients' faith in their therapists, expressing faith in clients, providing outcome education, and comparing progress with expectations. Clinical examples and research support are provided for each. PMID:24000836

  13. Innovative Legal Approaches to Address Obesity

    PubMed Central

    Pomeranz, Jennifer L; Teret, Stephen P; Sugarman, Stephen D; Rutkow, Lainie; Brownell, Kelly D

    2009-01-01

    Context: The law is a powerful public health tool with considerable potential to address the obesity issue. Scientific advances, gaps in the current regulatory environment, and new ways of conceptualizing rights and responsibilities offer a foundation for legal innovation. Methods: This article connects developments in public health and nutrition with legal advances to define promising avenues for preventing obesity through the application of the law. Findings: Two sets of approaches are defined: (1) direct application of the law to factors known to contribute to obesity and (2) original and innovative legal solutions that address the weak regulatory stance of government and the ineffectiveness of existing policies used to control obesity. Specific legal strategies are discussed for limiting children's food marketing, confronting the potential addictive properties of food, compelling industry speech, increasing government speech, regulating conduct, using tort litigation, applying nuisance law as a litigation strategy, and considering performance-based regulation as an alternative to typical regulatory actions. Finally, preemption is an overriding issue and can play both a facilitative and a hindering role in obesity policy. Conclusions: Legal solutions are immediately available to the government to address obesity and should be considered at the federal, state, and local levels. New and innovative legal solutions represent opportunities to take the law in creative directions and to link legal, nutrition, and public health communities in constructive ways. PMID:19298420

  14. Addressing language barriers to healthcare in India.

    PubMed

    Narayan, Lalit

    2013-01-01

    In spite of a growing recognition of the importance of doctor-patient communication, the issue of language barriers to healthcare has received very little attention in India. The Indian population speaks over 22 major languages with English used as the lingua franca for biomedicine. Large-scale internal migration has meant that health workers are encountering increasing instances of language discordance within clinical settings. Research done predominantly in the West has shown language discordance to significantly affect access to care, cause problems of comprehension and adherence, and decrease the satisfaction and quality of care. Addressing language barriers to healthcare in India requires a stronger political commitment to providing non-discriminatory health services, especially to vulnerable groups such as illiterate migrant workers. Research will have to address three broad areas: the ways in which language barriers affect health and healthcare, the efficacy of interventions to overcome language barriers, and the costs of language barriers and efforts to overcome them. There is a need to address such barriers in health worker education and clinical practice. Proven strategies such as hiring multilingual healthcare workers, providing language training to health providers, employing in situ translators or using telephone interpretation services will have to be evaluated for their appropriateness to the Indian context. Internet-based initiatives, the proliferation of mobile phones and recent advances in machine translation promise to contribute to the solution. PMID:24758452

  15. Addressable parallel cavity-based quantum memory

    NASA Astrophysics Data System (ADS)

    Vetlugin, Anton N.; Sokolov, Ivan V.

    2014-09-01

    We elaborate theoretically a model of addressable parallel cavity-based quantum memory for light able to store multiple transverse spatial modes of the input light signal of finite duration and, at the same time, a time sequence of the signals by side illumination. Having in mind possible applications for, e.g., quantum repeaters, we reveal the addressability of our memory, that is, its handiness for the read-out on demand of a given transverse quantized signal mode and of a given signal from the time sequence. The addressability is achieved by making use of different spatial configurations of pump wave during the write-in and the readout. We also demonstrate that for the signal durations of the order of few cavity decay times, better efficiency is achieved when one excites the cavity with zero light-matter coupling and finally performs fast excitation transfer from the intracavity field to the collective spin. On the other hand, the light-matter coupling control in time, based on dynamical impedance matching, allows to store and retrieve time restricted signals of the on-demand smooth time shape.

  16. Matching Alternative Addresses: a Semantic Web Approach

    NASA Astrophysics Data System (ADS)

    Ariannamazi, S.; Karimipour, F.; Hakimpour, F.

    2015-12-01

    Rapid development of crowd-sourcing or volunteered geographic information (VGI) provides opportunities for authoritatives that deal with geospatial information. Heterogeneity of multiple data sources and inconsistency of data types is a key characteristics of VGI datasets. The expansion of cities resulted in the growing number of POIs in the OpenStreetMap, a well-known VGI source, which causes the datasets to outdate in short periods of time. These changes made to spatial and aspatial attributes of features such as names and addresses might cause confusion or ambiguity in the processes that require feature's literal information like addressing and geocoding. VGI sources neither will conform specific vocabularies nor will remain in a specific schema for a long period of time. As a result, the integration of VGI sources is crucial and inevitable in order to avoid duplication and the waste of resources. Information integration can be used to match features and qualify different annotation alternatives for disambiguation. This study enhances the search capabilities of geospatial tools with applications able to understand user terminology to pursuit an efficient way for finding desired results. Semantic web is a capable tool for developing technologies that deal with lexical and numerical calculations and estimations. There are a vast amount of literal-spatial data representing the capability of linguistic information in knowledge modeling, but these resources need to be harmonized based on Semantic Web standards. The process of making addresses homogenous generates a helpful tool based on spatial data integration and lexical annotation matching and disambiguating.

  17. Aboriginal health promotion through addressing employment discrimination.

    PubMed

    Ferdinand, Angeline S; Paradies, Yin; Perry, Ryan; Kelaher, Margaret

    2014-01-01

    The Localities Embracing and Accepting Diversity (LEAD) program aimed to improve the mental health of Aboriginal Victorians by addressing racial discrimination and facilitating social and economic participation. As part of LEAD, Whittlesea Council adopted the Aboriginal Employment Pathways Strategy (AEPS) to increase Aboriginal employment and retention within the organisation. The Aboriginal Cultural Awareness Training Program was developed to build internal cultural competency and skills in recruiting and retaining Aboriginal staff. Analysis of surveys conducted before (pre; n=124) and after (post; n=107) the training program indicated a significant increase in participant understanding across all program objectives and in support of organisational policies to improve Aboriginal recruitment and retention. Participants ended the training with concrete ideas about intended changes, as well as how these changes could be supported by their supervisors and the wider organisation. Significant resources have since been allocated to implementing the AEPS over 5 years. In line with principles underpinning the National Aboriginal and Torres Strait Islander Health Plan 2013-23, particularly the focus on addressing racism as a determinant of health, this paper explores the AEPS and training program as promising approaches to health promotion through addressing barriers to Aboriginal employment. Possible implications for other large organisations are also considered. PMID:25155236

  18. Global-Address Space Networking (GASNet) Library

    SciTech Connect

    Welcome, Michael L.; Bell, Christian S.

    2011-04-06

    GASNet (Global-Address Space Networking) is a language-independent, low-level networking layer that provides network-independent, high-performance communication primitives tailored for implementing parallel global address space SPMD languages such as UPC and Titanium. The interface is primarily intended as a compilation target and for use by runtime library writers (as opposed to end users), and the primary goals are high performance, interface portability, and expressiveness. GASNet is designed specifically to support high-performance, portable implementations of global address space languages on modern high-end communication networks. The interface provides the flexibility and extensibility required to express a wide variety of communication patterns without sacrificing performance by imposing large computational overheads in the interface. The design of the GASNet interface is partitioned into two layers to maximize porting ease without sacrificing performance: the lower level is a narrow but very general interface called the GASNet core API - the design is basedheavily on Active Messages, and is implemented directly on top of each individual network architecture. The upper level is a wider and more expressive interface called GASNet extended API, which provides high-level operations such as remote memory access and various collective operations. This release implements GASNet over MPI, the Quadrics "elan" API, the Myrinet "GM" API and the "LAPI" interface to the IBM SP switch. A template is provided for adding support for additional network interfaces.

  19. Global-Address Space Networking (GASNet) Library

    Energy Science and Technology Software Center (ESTSC)

    2011-04-06

    GASNet (Global-Address Space Networking) is a language-independent, low-level networking layer that provides network-independent, high-performance communication primitives tailored for implementing parallel global address space SPMD languages such as UPC and Titanium. The interface is primarily intended as a compilation target and for use by runtime library writers (as opposed to end users), and the primary goals are high performance, interface portability, and expressiveness. GASNet is designed specifically to support high-performance, portable implementations of global address spacemore » languages on modern high-end communication networks. The interface provides the flexibility and extensibility required to express a wide variety of communication patterns without sacrificing performance by imposing large computational overheads in the interface. The design of the GASNet interface is partitioned into two layers to maximize porting ease without sacrificing performance: the lower level is a narrow but very general interface called the GASNet core API - the design is basedheavily on Active Messages, and is implemented directly on top of each individual network architecture. The upper level is a wider and more expressive interface called GASNet extended API, which provides high-level operations such as remote memory access and various collective operations. This release implements GASNet over MPI, the Quadrics "elan" API, the Myrinet "GM" API and the "LAPI" interface to the IBM SP switch. A template is provided for adding support for additional network interfaces.« less

  20. Laser device

    DOEpatents

    Scott, Jill R.; Tremblay, Paul L.

    2004-11-23

    A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

  1. Laser device

    DOEpatents

    Scott, Jill R.; Tremblay, Paul L.

    2007-07-10

    A laser device includes a target position, an optical component separated a distance J from the target position, and a laser energy source separated a distance H from the optical component, distance H being greater than distance J. A laser source manipulation mechanism exhibits a mechanical resolution of positioning the laser source. The mechanical resolution is less than a spatial resolution of laser energy at the target position as directed through the optical component. A vertical and a lateral index that intersect at an origin can be defined for the optical component. The manipulation mechanism can auto align laser aim through the origin during laser source motion. The laser source manipulation mechanism can include a mechanical index. The mechanical index can include a pivot point for laser source lateral motion and a reference point for laser source vertical motion. The target position can be located within an adverse environment including at least one of a high magnetic field, a vacuum system, a high pressure system, and a hazardous zone. The laser source and an electro-mechanical part of the manipulation mechanism can be located outside the adverse environment. The manipulation mechanism can include a Peaucellier linkage.

  2. Glass lasers.

    PubMed

    Snitzer, E

    1966-10-01

    After a general discussion of the merits of glass vs. crystals as host materials for laser ions, a summary is given of the various glass lasers. Because of its importance as an efficient, room temperature laser the properties of neodymium are considered in greater detail. This includes the nonlaser properties of Nd(3+) in glass, the spectral and temporal emission characteristics of Nd(3+) lasers, and Nd(3+) laser configurations. Separate sections deal with the other two room temperature lasers which use Yb(3+) or Er(3+). The problem of thermal stability of laser cavities is also discussed. Finally, a survey is given of the glasses that are useful as Faraday rotators. PMID:20057584

  3. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2003-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In a third embodiment, alternating short and long pulses of light from the excitation light source are directed into the ignitor laser. Each of the embodiments of the invention can be multiplexed so as to provide laser light energy sequentially to more than one ignitor laser.

  4. High-sensitivity remote detection of atmospheric pollutants and greenhouse gases at low ppm levels using near-infrared tunable diode lasers

    NASA Astrophysics Data System (ADS)

    Roy, Anirban; Upadhyay, Abhishek; Chakraborty, Arup Lal

    2016-05-01

    The concentration of atmospheric pollutants and greenhouse gases needs to be precisely monitored for sustainable industrial development and to predict the climate shifts caused by global warming. Such measurements are made on a continuous basis in ecologically sensitive and urban areas in the advanced countries. Tunable diode laser spectroscopy (TDLS) is the most versatile non-destructive technology currently available for remote measurements of multiple gases with very high selectivity (low cross-sensitivity), very high sensitivity (on the order of ppm and ppb) and under hazardous conditions. We demonstrate absolute measurements of acetylene, methane and carbon dioxide using a fielddeployable fully automated TDLS system that uses calibration-free 2f wavelength modulation spectroscopy (2f WMS) techniques with sensitivities of low ppm levels. A 40 mW, 1531.52 nm distributed feedback (DFB) diode laser, a 10 mW, 1650 nm DFB laser and a 1 mW, 2004 nm vertical cavity surface emitting laser (VCSEL) are used in the experiments to probe the P9 transition of acetylene, R4 transition of methane and R16 transition of carbon dioxide respectively. Data acquisition and on-board analysis comprises a Raspberry Pi-based embedded system that is controllable over a wireless connection. Gas concentration and pressure are simultaneously extracted by fitting the experimental signals to 2f WMS signals simulated using spectroscopic parameters obtained from the HITRAN database. The lowest detected concentration is 11 ppm for acetylene, 275 ppm for methane and 285 ppm for carbon dioxide using a 28 cm long single-pass gas cell.

  5. Practical considerations for industrial ultrafast lasers

    NASA Astrophysics Data System (ADS)

    Hankla, Allen K.; Bromley, Leigh J.; Weston, Jeremy

    1998-07-01

    The ultrafast laser industry has been built upon the scientific research market with the assumption that certain factors such as electrical power, cooling, and vibration isolation can be taken for granted. As ultrafast lasers stand ready to break into the industrial laser market, these and many other assumptions must be re-examined. This paper presents a discussion of the many non-trivial engineering issues that must be addressed in order to bring a highly sophisticated laser system into the harsh industrial environment. These practical considerations include performance, reliability, and cost of ownership. The foundation of the discussion is based upon lessons drawn from successful existing industrial laser systems such as CO2 and Nd:YAG. Relevant results from this study will then be applied to the particular case of ultrafast lasers with the goal of examining how current scientific lasers compare with industrial requirements and highlighting some technologies which can help bridge this gap.

  6. A Laser Technology Test Facility for Laser Inertial Fusion Energy (LIFE)

    SciTech Connect

    Bayramian, A J; Campbell, R W; Ebbers, C A; Freitas, B L; Latkowski, J; Molander, W A; Sutton, S B; Telford, S; Caird, J A

    2009-10-06

    A LIFE laser driver needs to be designed and operated which meets the rigorous requirements of the NIF laser system while operating at high average power, and operate for a lifetime of >30 years. Ignition on NIF will serve to demonstrate laser driver functionality, operation of the Mercury laser system at LLNL demonstrates the ability of a diode-pumped solid-state laser to run at high average power, but the operational lifetime >30 yrs remains to be proven. A Laser Technology test Facility (LTF) has been designed to specifically address this issue. The LTF is a 100-Hz diode-pumped solid-state laser system intended for accelerated testing of the diodes, gain media, optics, frequency converters and final optics, providing system statistics for billion shot class tests. These statistics will be utilized for material and technology development as well as economic and reliability models for LIFE laser drivers.

  7. Addressing Extremes within the WCRP - GEWEX Framework

    NASA Astrophysics Data System (ADS)

    van Oevelen, P. J.; Stewart, R.; Detemmerman, V.

    2008-12-01

    For large international coordination programs such as the Global Energy and Water Cycle Experiment (GEWEX) as part of the World Climate Research Programme (WCRP) it is difficult to strike a good balance between enabling as much international involvement as is possible and desirable and the achievability of the objectives. WCRP has decided that "Extremes Research" is one of several areas where it would like to see its efforts strengthened and scientific research pushed forward. The foci that are being selected should be phrased such that they are practical and achievable within a time span of 1 to 3 years. Preferably these foci build upon the expertise from cross WCRP activities and are not restricted to single core project activities. In this presentation an overview will be given of the various activities within GEWEX that are related to extremes and which ones would be most ideal to be addressed as WCRP foci from a GEWEX perspective. The rationale and context of extreme research will be presented as well links to other national and international programs. "Extremes Research" as a topic is attractive since it has a high societal relevance and impact. However, numerous definitions of extremes exist and they are being used in widely varying contexts making it not always clear of what exactly is being addressed. This presentation will give an outlook on what can be expected research wise in the near future based upon the outcomes of the Extremes Workshop organised last June in Vancouver in the context of the Coordinated Energy and water cycle Observations Project (CEOP) as part of GEWEX. In particular it will be shown how these activities, which will only address certain types of extremes, can be linked to adaptation and mitigation efforts taking place in other organisations and by national and international bodies.

  8. Addressing Risks to Advance Mental Health Research

    PubMed Central

    Iltis, Ana S.; Misra, Sahana; Dunn, Laura B.; Brown, Gregory K.; Campbell, Amy; Earll, Sarah A.; Glowinski, Anne; Hadley, Whitney B.; Pies, Ronald; DuBois, James M.

    2015-01-01

    Objective Risk communication and management are essential to the ethical conduct of research, yet addressing risks may be time consuming for investigators and institutional review boards (IRBs) may reject study designs that appear too risky. This can discourage needed research, particularly in higher risk protocols or those enrolling potentially vulnerable individuals, such as those with some level of suicidality. Improved mechanisms for addressing research risks may facilitate much needed psychiatric research. This article provides mental health researchers with practical approaches to: 1) identify and define various intrinsic research risks; 2) communicate these risks to others (e.g., potential participants, regulatory bodies, society); 3) manage these risks during the course of a study; and 4) justify the risks. Methods As part of a National Institute of Mental Health (NIMH)-funded scientific meeting series, a public conference and a closed-session expert panel meeting were held on managing and disclosing risks in mental health clinical trials. The expert panel reviewed the literature with a focus on empirical studies and developed recommendations for best practices and further research on managing and disclosing risks in mental health clinical trials. IRB review was not required because there were no human subjects. The NIMH played no role in developing or reviewing the manuscript. Results Challenges, current data, practical strategies, and topics for future research are addressed for each of four key areas pertaining to management and disclosure of risks in clinical trials: identifying and defining risks, communicating risks, managing risks during studies, and justifying research risks. Conclusions Empirical data on risk communication, managing risks, and the benefits of research can support the ethical conduct of mental health research and may help investigators better conceptualize and confront risks and to gain IRB approval. PMID:24173618

  9. Photosensitive biosensor array system using optical addressing without an addressing circuit on array biochips

    NASA Astrophysics Data System (ADS)

    Ahn, Chang-Geun; Ah, Chil Seong; Kim, Tae-Youb; Park, Chan Woo; Yang, Jong-Heon; Kim, Ansoon; Sung, Gun Yong

    2010-09-01

    This paper introduces a photosensitive biosensor array system with a simple photodiode array that detects photocurrent changes caused by reactions between probe and target molecules. Using optical addressing, the addressing circuit on the array chip is removed for low-cost application, and real cell addressing is achieved using an externally located computer-controllable light-emitting diode array module. The fabricated biosensor array chip shows a good dynamic range of 1-100 ng/mL under prostate-specific antigen detection, with an on-chip resolution of roughly 1 ng/mL.

  10. A Task Force to Address Bullying.

    PubMed

    Keller, Ronald; Budin, Wendy C; Allie, Tammy

    2016-02-01

    Bullying in the workplace can create a dysfunctional environment that is associated with serious physical and psychological harm to the person being bullied. Nurses' experience with bullying has gained considerable attention in recent years, and warrants further discussion. Nurse leaders need to develop and implement effective bullying prevention initiatives that will foster the functioning of a professional and productive staff in a healthy work environment. The aim of this article is to review workplace bullying as experienced by nurses, and describe how nurses at a Magnet-designated academic medical center developed and implemented a bullying task force to address the problem. PMID:26817556

  11. Best Practices in Hiring: Addressing Unconscious Bias

    NASA Astrophysics Data System (ADS)

    Simpson, Caroline E.

    2012-01-01

    Research has shown that implementing certain hiring practices will increase diversity in the workplace while enhancing academic quality. All of these practices rely on addressing the issue of 'unconscious bias.' A brief overview of unconscious bias--what it is, how it works, and simple measures to counter it--will be presented. Successful strategies, actions, and recommendations for implementing best recruiting and hiring practices, which have been proven to enhance academic excellence by ensuring a deep and diverse applicant pool, will also be presented.

  12. Building technology services that address student needs.

    PubMed

    Le Ber, Jeanne M; Lombardo, Nancy T; Wimmer, Erin

    2015-01-01

    A 16-question technology use survey was conducted to assess incoming health sciences students' knowledge of and interest in current technologies, and to identify student device and tool preferences. Survey questions were developed by colleagues at a peer institution and then edited to match this library's student population. Two years of student responses have been compiled, compared, and reviewed as a means for informing library decisions related to technology and resource purchases. Instruction and event programming have been revised to meet student preferences. Based on the number of students using Apple products, librarians are addressing the need to become more proficient with this platform. PMID:25611437

  13. Addressing the water budget with SMOS

    NASA Astrophysics Data System (ADS)

    Kerr, Y. H.; AlBitar, A.; Tomer, S. K.; Merlin, O.; Pellarin, T.

    2012-12-01

    SMOS, a L Band radiometer using aperture synthesis to achieve a good spatial resolution, was successfully launched on November 2, 2009. It was developed and made under the leadership of the European Space Agency (ESA) as an Earth Explorer Opportunity mission. It is a joint program with the Centre National d'Etudes Spatiales (CNES) in France and the Centro para el Desarrollo Teccnologico Industrial (CDTI) in Spain. SMOS carries a single payload, an L band 2D interferometric,radiometer in the 1400-1427 MHz h protected band. This wavelength penetrates well through the vegetation and the atmosphere is almost transparent enabling to infer both soil moisture and vegetation water content. SMOS achieves an unprecedented spatial resolution of 50 km at L-band maximum (43 km on average) with multi angular-dual polarized (or fully polarized) brightness temperatures over the globe and with a revisit time smaller than 3 days. SMOS as been now acquiring data for almost 2 years. The data quality exceeds what was expected, showing very good sensitivity and stability. The data is however very much impaired by man made emission in the protected band, leading to degraded measurements in several areas including parts of Europe and of China. However, many different international teams are now addressing cal val activities in various parts of the world, with notably large field campaigns either on the long time scale or over specific targets to address the specific issues. In parallel different teams are now starting addressing data use in various fields including hydrology. It requires coupling with other models and or disaggregation to address soil moisture distribution over watersheds. Significant new results were obtained for floods and drought events, together with new potential applications in terms of precipitation monitoring This paper thus gives an overview of the science goals of the SMOS mission, a description of its main elements, and a taste of the first results including

  14. Addressing the challenges of emerging infectious disease.

    PubMed

    Pinner, R W

    1996-01-01

    Through the recent examples of diphtheria in the former Soviet Union, plague in India, and trends in pneumonia mortality in the United States, the author, in this article, illustrates issues in emerging infectious diseases. The Centers for Disease Control's plan, Addressing Emerging Infectious Disease Threats: A Prevention Strategy for the United States, is summarized. Initial efforts to implement this plan are described, with particular focus on the development of Emerging Infections Programs, which are conducting epidemiologic and laboratory projects on several infectious diseases, including invasive bacterial diseases, unexplained deaths, foodborne diseases, and ehrlichiosis in four population-based sites in the United States. PMID:8571983

  15. Versions to Address Business Process Flexibility Issue

    NASA Astrophysics Data System (ADS)

    Chaâbane, Mohamed Amine; Andonoff, Eric; Bouaziz, Rafik; Bouzguenda, Lotfi

    This paper contributes to address an important issue in business process management: the Business Process (BP) flexibility issue. First, it defends that versions are an interesting solution to deal with both a priori (when designing BPs) and a posteriori (when executing BPs) flexibility. It also explains why previous contributions about versions of BPs are incomplete, and need to be revisited. Then, the paper presents a meta-model for BP versions, which combines five perspectives -the functional, process, informational, organizational and operation perspectives- for BP modelling, and which allows a comprehensive description of versionalized BPs.

  16. Single-mode and tunable microfluidic dye lasers

    NASA Astrophysics Data System (ADS)

    Kristensen, A.; Balslev, S.; Gersborg-Hansen, M.; Bilenberg, B.; Rasmussen, T.; Nilsson, D.

    2006-08-01

    We present a technology for miniaturized, chip-based liquid dye lasers, which may be integrated with microfluidic networks and planar waveguides without addition of further process steps. The microfluidic dye lasers consist of a microfluidic channel with an embedded optical resonator. The lasers are operated with Rhodamine 6G laser dye dissolved in a suitable solvent, such as ethanol or ethylene glycol, and optically pumped at 532 nm with a pulsed, frequency doubled Nd:YAG laser. Both vertically and laterally emitting devices are realized. A vertically emitting Fabry-Perot microcavity laser is integrated with a microfluidic mixer, to demonstrate realtime wavelength tunability. Two major challenges of this technology are addressed: lasing threshold and fluidic handling. Low threshold, in-plane emission and integration with polymer waveguides and microfluidic networks is demonstrated with distributed feed-back lasers. The challenge of fluidic handling is addressed by hybridization with mini-dispensers, and by applying capillary filling of the laser devices.

  17. Laser science and technology update - 1999

    SciTech Connect

    Chen, H L; Powell, H T

    1999-09-23

    The Laser Science and Technology (LS and T) Program's mission is to provide advanced solid-state laser and optics technologies for the Laboratory, government, and industry. The primary activities of LS and T in 1998 have been threefold--to complete the laser technology development and laser component testing for the ICF/NIF Program, to develop advanced solid-state laser systems and optical components for the Department of Defense (DoD) and DOE, and to address the needs of other government agencies and U.S. industry. After a four-year campaign, the LS and T Program achieved timely completion of the laser development effort for the NIF in 1998. This effort includes the special laser and component development, integrated performance testing on Beamlet, and detailed design and cost optimization using computation codes. Upon completing the Title II design review, the focus of the LS and T support effort has been shifted toward NIF laser hardware acquisition and deployment. The LS and T team also continued to develop advanced high-power solid-state laser technology for both the U.S. government and industrial partners. Progress was also made in several new areas: (a) diode-pumped solid-state laser drivers for high-energy-density physics and inertial fusion energy; (b) high-average-power femtosecond and nanosecond lasers for materials processing; and (c) femtosecond lasers for the generation of advanced light sources.

  18. Addressing Science Use Cases with HELIO

    NASA Astrophysics Data System (ADS)

    Bentley, R. D.; Aboudarham, J.; Csillaghy, A.; Jacquey, C.; Hapgood, M. A.; Messerotti, M.; Gallagher, P.; Bocchialini, K.; Hurlburt, N. E.; Roberts, D.; Sanchez Duarte, L.

    2009-12-01

    The Heliophysics Integrated Observatory (HELIO) is a new VO project funded under the EC's Seventh Framework Programme (FP7). It includes thirteen partners scattered over six countries and is led by University College London. HELIO is designed to support the heliophysics community and is based on a Service Oriented Architecture. The services developed by and integrated into HELIO can be used to address a wide range of science problems; they can be used individually or as part of a work-flow driven search engine that can use a propagation (or other) model to help locate obervations that describe interesting phenomena. We will describe and discuss how the components of HELIO could be used to address science use cases, particularly how a user can adapt the work flow to their own science interests. Networking is one of the three Activities of the HELIO Integrated Infrastructure Initiatives (I3) project. Within this activity we plan to involve the community in all aspects of the design and testing of the HELIO system, including determining which data and metadata should be included, how the quality and content of metadata can be included, etc. We are investigating ways of making HELIO "domain-aware" so that researchers who are specialists in one of the communities that constitute heliophysics can easily identify, access and use data they need from the other communities. We will discuss how the community can help us develop this capability.

  19. Multi-port, optically addressed RAM

    NASA Technical Reports Server (NTRS)

    Johnston, Alan R. (Inventor); Nixon, Robert H. (Inventor); Bergman, Larry A. (Inventor); Esener, Sadik (Inventor)

    1989-01-01

    A random access memory addressing system utilizing optical links between memory and the read/write logic circuits comprises addressing circuits including a plurality of light signal sources, a plurality of optical gates including optical detectors associated with the memory cells, and a holographic optical element adapted to reflect and direct the light signals to the desired memory cell locations. More particularly, it is a multi-port, binary computer memory for interfacing with a plurality of computers. There are a plurality of storage cells for containing bits of binary information, the storage cells being disposed at the intersections of a plurality of row conductors and a plurality of column conductors. There is interfacing logic for receiving information from the computers directing access to ones of the storage cells. There are first light sources associated with the interfacing logic for transmitting a first light beam with the access information modulated thereon. First light detectors are associated with the storage cells for receiving the first light beam, for generating an electrical signal containing the access information, and for conducting the electrical signal to the one of the storage cells to which it is directed. There are holographic optical elements for reflecting the first light beam from the first light sources to the first light detectors.

  20. Framework for Address Cooperative Extended Transactions

    Energy Science and Technology Software Center (ESTSC)

    1997-12-01

    The Framework for Addressing Cooperative Extended Transactions (FACET) is an object-oriented software framework for building models of complex, cooperative behaviors of agents. it can be used to implement simulation models of societal processes such as the complex interplay of participating individuals and organizations engaged in multiple concurrent transactions in pursuit of their various goals. These transactions can be patterned on, for example, clinical guidelines and procedures, business practices, government and corporate policies, etc. FACET canmore » also address other complex behaviors such as biological life cycles or manufacturing processes. FACET includes generic software objects representing the fundamental classes of agent -- Person and Organization - with mechanisms for resource management, including resolution of conflicting requests for participation and/or use of the agent's resources. The FACET infrastructure supports stochastic behavioral elements and coping mechanisms by which specified special conditions and events can cause an active cooperative process to be preempted, diverting the participants onto appropriate alternative behavioral pathways.« less

  1. Addressing medical errors in hand surgery.

    PubMed

    Johnson, Shepard P; Adkinson, Joshua M; Chung, Kevin C

    2014-09-01

    Influential think tanks such as the Institute of Medicine have raised awareness about the implications of medical errors. In response, organizations, medical societies, and hospitals have initiated programs to decrease the incidence and prevent adverse effects of these errors. Surgeons deal with the direct implications of adverse events involving patients. In addition to managing the physical consequences, they are confronted with ethical and social issues when caring for a harmed patient. Although there is considerable effort to implement system-wide changes, there is little guidance for hand surgeons on how to address medical errors. Admitting an error by a physician is difficult, but a transparent environment where patients are notified of errors and offered consolation and compensation is essential to maintain physician-patient trust. Furthermore, equipping hand surgeons with a guide for addressing medical errors will help identify system failures, provide learning points for safety improvement, decrease litigation against physicians, and demonstrate a commitment to ethical and compassionate medical care. PMID:25154576

  2. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2002-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In the embodiment of the invention claimed herein, the beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being combined with either the first portion after a delay before injection into the ignitor laser.

  3. Four channel Laser Firing Unit using laser diodes

    NASA Technical Reports Server (NTRS)

    Rosner, David, Sr.; Spomer, Edwin, Sr.

    1994-01-01

    This paper describes the accomplishments and status of PS/EDD's (Pacific Scientific/Energy Dynamics Division) internal research and development effort to prototype and demonstrate a practical four channel laser firing unit (LFU) that uses laser diodes to initiate pyrotechnic events. The LFU individually initiates four ordnance devices using the energy from four diode lasers carried over the fiber optics. The LFU demonstrates end-to-end optical built in test (BIT) capabilities. Both Single Fiber Reflective BIT and Dual Fiber Reflective BIT approaches are discussed and reflection loss data is presented. This paper includes detailed discussions of the advantages and disadvantages of both BIT approaches, all-fire and no-fire levels, and BIT detection levels. The following topics are also addressed: electronic control and BIT circuits, fiber optic sizing and distribution, and an electromechanical shutter type safe/arm device. This paper shows the viability of laser diode initiation systems and single fiber BIT for typing military applications.

  4. MEMS-based beam steering system for individual addressing of trapped ions

    NASA Astrophysics Data System (ADS)

    Kim, Taehyun; Knoernschild, Caleb; Mount, Emily; Crain, Stephen; Noek, Rachel; Gaultney, Daniel; van Rynbach, Andre; Maunz, Peter; Kim, Jungsang

    2011-05-01

    One of the important components to implement large-scale trapped ion quantum information processing is a scalable technology to manipulate individual ions in a long linear chain of ions. So far, individual addressing has been demonstrated by steering a focused laser beam on individual ions with acousto-optic and electro-optic deflectors, by utilizing the Zeeman shift due to a magnetic field gradient, and by separating a single ion from the rest of the chain for individual exposure to laser light. Micro-mirrors based on microelectromechanical system (MEMS) technology can be used to design an alternative beam steering system which can handle multiple beams with different wavelengths and address locations in multiple dimensions. We will report our progress in integrating a MEMS beam steering system with an Yb ion trap experiment. Our MEMS system is designed to steer an ultraviolet beam with a waist of ~1.5 μm across a 20 μm range. To demonstrate the individual addressing capability, we plan to measure the Ramsey interference of the differential AC Stark shift induced by an individually-focused, far-detuned laser beam.

  5. Laser ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    2002-01-01

    In the apparatus of the invention, a first excitation laser or other excitation light source capable of producing alternating beams of light having different wavelengths is used in tandem with one or more ignitor lasers to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using the single remote excitation light source for pumping one or more small lasers located proximate to one or more fuel combustion zones with alternating wavelengths of light.

  6. Laser polishing

    NASA Astrophysics Data System (ADS)

    Temmler, A.; Willenborg, E.; Wissenbach, K.

    2012-03-01

    A new approach to polish metallic freeform surfaces is polishing by means of laser radiation. In this technology a thin surface layer is molten and the surface tension leads to a material flow from the peaks to the valleys. No material is removed but reallocated while molten. As the typical processing time is 1 min/cm2 laser polishing is up to 30 times faster than manual polishing. Reducing the roughness by laser polishing is achieved for several different materials such as hot work steels for the die and molding industries or titanium alloys for medical engineering. Enhancing the appearance of design surfaces is achieved by creating a dual-gloss effect by selective laser polishing (SLP). In comparison to conventional polishing processes laser polishing opens up the possibility of selective processing of small areas (< 0.1 mm2). A dual-gloss effect is based on a space-resolved change in surface roughness. In comparison to the initial surface the roughness of the laser polished surface is reduced significantly up to spatial wavelengths of 80 microns and therefore the gloss is raised considerably. The surface roughness is investigated by a spectral analysis which is achieved by a discrete convolution of the surface profile with a Gaussian loaded function. The surfaces roughness is split into discrete wavelength intervals and can be evaluated and optimized. Laser polishing is carried out by using a special tailored five-axis mechanical handling system, combined with a three axis laser scanning system and a fibre laser.

  7. Biocavity Lasers

    SciTech Connect

    Gourley, P.L.; Gourley, M.F.

    2000-10-05

    Laser technology has advanced dramatically and is an integral part of today's healthcare delivery system. Lasers are used in the laboratory analysis of human blood samples and serve as surgical tools that kill, burn or cut tissue. Recent semiconductor microtechnology has reduced the size o f a laser to the size of a biological cell or even a virus particle. By integrating these ultra small lasers with biological systems, it is possible to create micro-electrical mechanical systems that may revolutionize health care delivery.

  8. Laser apparatus

    DOEpatents

    Lewis, Owen; Stogran, Edmund M.

    1980-01-01

    Laser apparatus is described wherein an active laser element, such as the disc of a face-pumped laser, is mounted in a housing such that the weight of the element is supported by glass spheres which fill a chamber defined in the housing between the walls of the housing and the edges of the laser element. The uniform support provided by the spheres enable the chamber and the pump side of the laser element to be sealed without affecting the alignment or other optical properties of the laser element. Cooling fluid may be circulated through the sealed region by way of the interstices between the spheres. The spheres, and if desired also the cooling fluid may contain material which absorbs radiation at the wavelength of parasitic emissions from the laser element. These parasitic emissions enter the spheres through the interface along the edge surface of the laser element and it is desirable that the index of refraction of the spheres and cooling fluid be near the index of refraction of the laser element. Thus support, cooling, and parasitic suppression functions are all accomplished through the use of the arrangement.

  9. Polymer lasers: recent advances

    NASA Astrophysics Data System (ADS)

    Riedl, T.; Rabe, T.; Görrn, P.; Wang, J.; Weinmann, T.; Hinze, P.; Galbrecht, F.; Scherf, U.; Kowalsky, W.

    2007-09-01

    The development of organic thin film lasers has seen tremendous progress over the past few years. Only a few materials are necessary to allow for continuous wavelength tunability in the spectral region from the UV to the near IR. At the same time, the lasing thresholds of organic thin film lasers have been reduced considerably both due to improved low-loss distributed feedback (DFB) resonator structures and highly efficient gain materials based on guest-host energy transfer. Aside from the as yet open issue of electrical operation of organic lasers, which we will address briefly in this paper, there are numerous applications (e.g. in biotechnology, spectroscopy) where optically driven organic lasers may be the more cost effective and versatile solution. In this context, tunable polymer lasers pumped by compact and inexpensive InGaN laser diodes will be shown. These lasers are based on a modified poly(9,9'-dioctylfluorene) derivative (BN-PFO) containing 12% of -6,6'-(2,2'-octyloxy-1,1'-binaphthyl) spacer groups doped with a few wt% of the stilbene dye 1,4-Bis(2-(4-(N,N-di(p-tolyl)amino)phenyl)vinyl-benzene (DPAVB). With the same host polymer (BN-PFO) quasi continuous wave operation (up to 5 MHz) can be demonstrated. Highly repetitive lasers are especially desirable for many spectroscopic applications. This regime of operstion is found to be impeded by the photo-physics in doped organic systems where the accumulation of absorptive species in the gain medium leads to piled-up absorption losses and consequently to termination of the lasing process. The presence of the dopand molecules seems to strongly promote the formation and stabilization of the species which we relate to triplet excitons. Therefore, the concentration of the dopand affects the feasibility of quasi-cw operation of thin-film organic lasers. Strategies and results to achieve highly repetitive operation in low-threshold guest-host systems BN-PFO:DPAVB or BN-PFO:poly[2-methoxy-5-(2'-ethylhexyloxy)-1

  10. Addressing submarine geohazards through scientific drilling

    NASA Astrophysics Data System (ADS)

    Camerlenghi, A.

    2009-04-01

    Natural submarine geohazards (earthquakes, volcanic eruptions, landslides, volcanic island flank collapses) are geological phenomena originating at or below the seafloor leading to a situation of risk for off-shore and on-shore structures and the coastal population. Addressing submarine geohazards means understanding their spatial and temporal variability, the pre-conditioning factors, their triggers, and the physical processes that control their evolution. Such scientific endeavour is nowadays considered by a large sector of the international scientific community as an obligation in order to contribute to the mitigation of the potentially destructive societal effects of submarine geohazards. The study of submarine geohazards requires a multi-disciplinary scientific approach: geohazards must be studied through their geological record; active processes must be monitored; geohazard evolution must be modelled. Ultimately, the information must be used for the assessment of vulnerability, risk analysis, and development of mitigation strategies. In contrast with the terrestrial environment, the oceanic environment is rather hostile to widespread and fast application of high-resolution remote sensing techniques, accessibility for visual inspection, sampling and installation of monitoring stations. Scientific Drilling through the IODP (including the related pre site-survey investigations, sampling, logging and in situ measurements capability, and as a platform for deployment of long term observatories at the surface and down-hole) can be viewed as the centre of gravity of an international, coordinated, multi-disciplinary scientific approach to address submarine geohazards. The IODP Initial Science Plan expiring in 2013 does not address openly geohazards among the program scientific objectives. Hazards are referred to mainly in relation to earthquakes and initiatives towards the understanding of seismogenesis. Notably, the only drilling initiative presently under way is the

  11. Fiber lasers and their applications [Invited].

    PubMed

    Shi, Wei; Fang, Qiang; Zhu, Xiushan; Norwood, R A; Peyghambarian, N

    2014-10-01

    Fiber lasers have seen progressive developments in terms of spectral coverage and linewidth, output power, pulse energy, and ultrashort pulse width since the first demonstration of a glass fiber laser in 1964. Their applications have extended into a variety of fields accordingly. In this paper, the milestones of glass fiber laser development are briefly reviewed and recent advances of high-power continuous wave, Q-switched, mode-locked, and single-frequency fiber lasers in the 1, 1.5, 2, and 3 μm regions and their applications in such areas as industry, medicine, research, defense, and security are addressed in detail. PMID:25322245

  12. Addressing health literacy in patient decision aids

    PubMed Central

    2013-01-01

    Background Effective use of a patient decision aid (PtDA) can be affected by the user’s health literacy and the PtDA’s characteristics. Systematic reviews of the relevant literature can guide PtDA developers to attend to the health literacy needs of patients. The reviews reported here aimed to assess: 1. a) the effects of health literacy / numeracy on selected decision-making outcomes, and b) the effects of interventions designed to mitigate the influence of lower health literacy on decision-making outcomes, and 2. the extent to which existing PtDAs a) account for health literacy, and b) are tested in lower health literacy populations. Methods We reviewed literature for evidence relevant to these two aims. When high-quality systematic reviews existed, we summarized their evidence. When reviews were unavailable, we conducted our own systematic reviews. Results Aim 1: In an existing systematic review of PtDA trials, lower health literacy was associated with lower patient health knowledge (14 of 16 eligible studies). Fourteen studies reported practical design strategies to improve knowledge for lower health literacy patients. In our own systematic review, no studies reported on values clarity per se, but in 2 lower health literacy was related to higher decisional uncertainty and regret. Lower health literacy was associated with less desire for involvement in 3 studies, less question-asking in 2, and less patient-centered communication in 4 studies; its effects on other measures of patient involvement were mixed. Only one study assessed the effects of a health literacy intervention on outcomes; it showed that using video to improve the salience of health states reduced decisional uncertainty. Aim 2: In our review of 97 trials, only 3 PtDAs overtly addressed the needs of lower health literacy users. In 90% of trials, user health literacy and readability of the PtDA were not reported. However, increases in knowledge and informed choice were reported in those studies

  13. STS-79 John Blaha address news media

    NASA Technical Reports Server (NTRS)

    1996-01-01

    STS-79 Mission Specialist John E. Blaha addresses news media gathered for the flight crew's late night arrival at the KSC Shuttle Landing Facility. A veteran space traveler who served as either commander or pilot on his four previous Shuttle flights, Blaha is taking a mission specialist's slot on STS-79 because he will be transferring to the Russian Space Station Mir for an extended stay. American astronaut Shannon Lucid will take his place aboard the Space Shuttle Atlantis for the return trip home. Final preparations are under way for launch of Atlantis on Mission STS-79, with liftoff scheduled to occur during an approximately seven-minute window opening at 4:54 a.m. EDT, Sept.16.

  14. Combined hepatocellular cholangiocarcinoma: Controversies to be addressed

    PubMed Central

    Wang, An-Qiang; Zheng, Yong-Chang; Du, Juan; Zhu, Cheng-Pei; Huang, Han-Chun; Wang, Shan-Shan; Wu, Liang-Cai; Wan, Xue-Shuai; Zhang, Hao-Hai; Miao, Ruo-Yu; Sang, Xin-Ting; Zhao, Hai-Tao

    2016-01-01

    Combined hepatocellular cholangiocarcinoma (CHC) accounts for 0.4%-14.2% of primary liver cancer cases and possesses pathological features of both hepatocellular carcinoma and cholangiocarcinoma. Since this disease was first described and classified in 1949, the classification of CHC has continuously evolved. The latest definition and classification of CHC by the World Health Organization is based on the speculation that CHC arises from hepatic progenitor cells. However, there is no evidence demonstrating the common origin of different components of CHC. Furthermore, the definition of CHC subtypes is still ambiguous and the identification of CHC subtype when a single tumor contains many components has remained unresolved. In addition, there is no summary on the newly recognized histopathology features or the contribution of CHC components to prognosis and outcome of this disease. Here we provide a review of the current literature to address these questions. PMID:27182157

  15. Applying evolutionary biology to address global challenges

    PubMed Central

    Carroll, Scott P.; Jørgensen, Peter Søgaard; Kinnison, Michael T.; Bergstrom, Carl T.; Denison, R. Ford; Gluckman, Peter; Smith, Thomas B.; Strauss, Sharon Y.; Tabashnik, Bruce E.

    2014-01-01

    Two categories of evolutionary challenges result from escalating human impacts on the planet. The first arises from cancers, pathogens and pests that evolve too quickly, and the second from the inability of many valued species to adapt quickly enough. Applied evolutionary biology provides a suite of strategies to address these global challenges that threaten human health, food security, and biodiversity. This review highlights both progress and gaps in genetic, developmental and environmental manipulations across the life sciences that either target the rate and direction of evolution, or reduce the mismatch between organisms and human-altered environments. Increased development and application of these underused tools will be vital in meeting current and future targets for sustainable development. PMID:25213376

  16. Remediation tradeoffs addressed with simulated annealing optimization

    SciTech Connect

    Rogers, L. L., LLNL

    1998-02-01

    Escalation of groundwater remediation costs has encouraged both advances in optimization techniques to balance remediation objectives and economics and development of innovative technologies to expedite source region clean-ups. We present an optimization application building on a pump-and-treat model, yet assuming a prior removal of different portions of the source area to address the evolving management issue of more aggressive source remediation. Separate economic estimates of in-situ thermal remediation are combined with the economic estimates of the subsequent optimal pump-and-treat remediation to observe tradeoff relationships of cost vs. highest remaining contamination levels (hot spot). The simulated annealing algorithm calls the flow and transport model to evaluate the success of a proposed remediation scenario at a U.S.A. Superfund site contaminated with volatile organic compounds (VOCs).

  17. Addressing submarine geohazards through scientific drilling

    NASA Astrophysics Data System (ADS)

    Camerlenghi, A.

    2009-04-01

    Natural submarine geohazards (earthquakes, volcanic eruptions, landslides, volcanic island flank collapses) are geological phenomena originating at or below the seafloor leading to a situation of risk for off-shore and on-shore structures and the coastal population. Addressing submarine geohazards means understanding their spatial and temporal variability, the pre-conditioning factors, their triggers, and the physical processes that control their evolution. Such scientific endeavour is nowadays considered by a large sector of the international scientific community as an obligation in order to contribute to the mitigation of the potentially destructive societal effects of submarine geohazards. The study of submarine geohazards requires a multi-disciplinary scientific approach: geohazards must be studied through their geological record; active processes must be monitored; geohazard evolution must be modelled. Ultimately, the information must be used for the assessment of vulnerability, risk analysis, and development of mitigation strategies. In contrast with the terrestrial environment, the oceanic environment is rather hostile to widespread and fast application of high-resolution remote sensing techniques, accessibility for visual inspection, sampling and installation of monitoring stations. Scientific Drilling through the IODP (including the related pre site-survey investigations, sampling, logging and in situ measurements capability, and as a platform for deployment of long term observatories at the surface and down-hole) can be viewed as the centre of gravity of an international, coordinated, multi-disciplinary scientific approach to address submarine geohazards. The IODP Initial Science Plan expiring in 2013 does not address openly geohazards among the program scientific objectives. Hazards are referred to mainly in relation to earthquakes and initiatives towards the understanding of seismogenesis. Notably, the only drilling initiative presently under way is the

  18. Applying evolutionary biology to address global challenges.

    PubMed

    Carroll, Scott P; Jørgensen, Peter Søgaard; Kinnison, Michael T; Bergstrom, Carl T; Denison, R Ford; Gluckman, Peter; Smith, Thomas B; Strauss, Sharon Y; Tabashnik, Bruce E

    2014-10-17

    Two categories of evolutionary challenges result from escalating human impacts on the planet. The first arises from cancers, pathogens, and pests that evolve too quickly and the second, from the inability of many valued species to adapt quickly enough. Applied evolutionary biology provides a suite of strategies to address these global challenges that threaten human health, food security, and biodiversity. This Review highlights both progress and gaps in genetic, developmental, and environmental manipulations across the life sciences that either target the rate and direction of evolution or reduce the mismatch between organisms and human-altered environments. Increased development and application of these underused tools will be vital in meeting current and future targets for sustainable development. PMID:25213376

  19. Extreme space weather studies: Addressing societal needs

    NASA Astrophysics Data System (ADS)

    Ngwira, C. M.

    2014-12-01

    Extreme space weather events can adversely impact the operations of critical modern-day technological infrastructure such as high-voltage electric power transmission grids. Understanding of coupled magnetosphere-ionosphere dynamics under extreme solar wind driving conditions is still a major challenge mainly because of a lack of data during such time intervals. This presentation will highlight some of the past and on-going investigations on extreme space weather events, and how these investigations are used to address societal needs. Particularly, I will describe how first principles physics-based 3-D global MHD models are playing a major role in advancing our knowledge on extreme geomagnetically induced currents. These MHD models represent a very important component of attempts to understand the response of the magnetosphere-ionosphere system to varying solar wind conditions.

  20. Presidential address, 2001. Advice to young surgeons

    PubMed Central

    MacFarlane, John K.

    2002-01-01

    In his 2001 presidential address to the Canadian Association of General Surgeons, the author offers advice to young surgeons, based on his lifetime experience as a surgical educator, researcher and practitioner. He offers the following samples of wisdom for young surgeons: they should be prepared for a lifetime of learning and be willing and able to adapt to new advances; they should listen to their patients as they describe their presenting complaints and not be tempted to interrupt; they should take time in an emergency situation and remember that split-second decisions can affect the patient for a lifetime; they should be willing to take advice from fellow professionals; they should take time to maintain a quality family life and take adequate time away from the workplace; they should be active be a role model in their community; and, finally, they should get involved and adopt an advocacy role in their profession. PMID:11939654