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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. Coupled resonator vertical cavity laser

    SciTech Connect

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

    1998-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Gadallah, Abdel-Sattar; Michalzik, Rainer

    2013-03-01

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

  4. 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.

  5. Degradation in vertical cavity lasers

    NASA Astrophysics Data System (ADS)

    Herrick, Robert Wallace

    Vertical Cavity Lasers (VCLs) are rapidly being adopted as low-cost sources in data communications links. It is thus important that we understand how VCLs age, if we are to be able to extend their lifetime to meet the desired reliability standards. We focus primarily on the widely-commercialized top-emitting, proton-implanted design, with GaAs quantum wells, and emitting at 850 nm. We also provide extensive characterization of 680 nm GaInP-quantum-well proton-implanted VCLs. A brief discussion is provided regarding the degradation in 980 nm etched pillar VCLs, and 980 and 850 nm oxide-aperture VCLs. Surprisingly, a number of major differences are noted between the degradation behavior of traditional stripe lasers (which lase in the plane of the active region), and vertical cavity lasers (which lase perpendicular to the active region). The primary degradation mechanism in VCLs appears to be related to passivation of the dopants in the center of the lasers, which forces current out toward the device edges, where it is not useful in the lasing process. In the final stages of device degradation, dislocations appear not only in the active regions, but also surprisingly in the p-mirrors above the active region. The driving mechanism for this degradation process is discussed in detail. Extensive characterization, including cathodoluminescence (CL), transmission electron microscopy (TEM), photoluminescence (PL), electroluminescence (EL), electron beam induced current (EBIC), and scanning probe techniques are used to shed light on the nature and causes of the aging process. In spite of valid reasons for concern about the potential degradation rates of VCLs, we do not observe dark-line defects in the proton-implanted lasers which are our main research focus, and the lasers appear to be relatively insensitive to damage to the die edges or facets, in contrast to stripe lasers. Further, the proton implant appears not to participate in the aging process as had been expected

  6. 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.

  7. 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.

  8. Coupled Resonator Vertical Cavity Laser Diode

    SciTech Connect

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

    1999-09-16

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

  9. 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.

  10. High-speed vertical cavity surface emitting lasers

    SciTech Connect

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

    1997-03-01

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

  11. 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.

  12. Bistable Vertical Cavity Surface Emitting Lasers

    DTIC Science & Technology

    1992-06-30

    734-736 (9 April, 1992). 7. D.L. Huffaker, C. Lei, D.G. Deppe, C.J. Pinzone , J.G. Neff, and R.D. Dupuis, "Controlled Spontaneous Emission in Room... Pinzone , J.G. Neff, and R.D. F-) Dupuis, "Effect on Spontaneous Emission of Quantum Well Placement in a Short Vertical Cavity", Appl. Phys. Lett., to...be published. ........ ........ 9. C. Lei, C.J. Pinzone , Z. Huang, D.L. Huffaker, D.G. Deppe, J.G. Neff, and R.D. Dupuis, "Room Temperature Spontaneous

  13. 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.

  14. 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.

  15. Electrically injected visible vertical cavity surface emitting laser diodes

    DOEpatents

    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.

  16. Engineering oxide apertures in vertical-cavity lasers

    NASA Astrophysics Data System (ADS)

    Hegblom, Eric Richard

    This work focuses on analyzing and improving the performance of smaller vertical cavity lasers which employ transparent, insulating apertures (commonly made by lateral etching or oxidation) for optical and current confinement. Improved performance of smaller vertical cavity lasers is important for applications which require arrays of vertical cavity lasers operating at low power such as free-space optical interconnections between computer boards or even computer chips or highly parallel laser printing schemes. And if properly scaled, smaller lasers have better characteristics at lower output powers. We analyze two major barriers to shrinking the aperture size: optical scattering losses and current spreading. These analyses helped explain the observed drop in efficiency and rise of threshold current density in earlier. oxide apertured, small lasers, and directed changes in the aperture design such as tapering the oxide front for a more lens-like shape. In addition, these analyses were reduced to simple formulas involving normalized parameters which can be applied to a variety of designs. We also demonstrate experimentally the impact of improvements in aperture design which enabled small, single-mode, VCSELs <2mum diameter to reach record efficiencies and enabled 2--3mum diameter devices to reach power conversion efficiencies of 20% at output powers as low as 150muW. And we discuss how these results can be unproved with carbon doping and better tailoring of the doping profile to minimize resistance with the least absorptive loss.

  17. 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.

  18. Single transverse mode selectively oxidized vertical cavity lasers

    SciTech Connect

    CHOQUETTE,KENT D.

    2000-04-18

    Vertical cavity surface emitting laser (VCSEL) sources have been adopted into Gigabit Ethernet applications in a remarkably short time period. VCSELs are particularly suitable for multimode optical fiber local area networks (LANs), due to their reduced threshold current, circular output beam, and inexpensive and high volume manufacture. Moreover, selectively oxidized VCSELs are nearly ideal LAN sources since the oxide aperture within the laser cavity produces strong electrical and optical confinement which enables high electrical to optical conversion efficiency and minimal modal discrimination allowing emission into multiple transverse optical modes. In addition to the large demand for multimode lasers, VCSELs which emit into a single optical mode are also increasingly sought for emerging applications, which include data communication with single mode optical fiber, bar code scanning, laser printing, optical read/write heads, and modulation spectroscopy. To achieve single mode selectively oxidized VCSELs is a challenging task, since the inherent index confinement within these high performance lasers is very large.

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

    SciTech Connect

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

    1999-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

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

    SciTech Connect

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

    2003-01-01

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

  2. Vertical Cavity Surface Emitting Laser sources for gas detection

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Margalit, Near Moses

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

  4. Single transverse mode selectively oxidized vertical cavity lasers

    SciTech Connect

    CHOQUETTE,KENT D.; GEIB,KENT M.; BRIGGS,RONALD D.; ALLERMAN,ANDREW A.; HINDI,JANA JO

    2000-04-26

    Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.

  5. 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.

  6. 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.

  7. Visible light emitting vertical cavity surface emitting lasers

    DOEpatents

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

    1995-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Jeong, Hyejin

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

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

    DTIC Science & Technology

    1992-12-01

    01 Design and Characterization of Optically Pumped Vertical Cavity Surface Emitting Lasers THESIS Presented to the Faculty of the School of Engineering...VCSELs ............................ 3-11 3.4 Injection Lasers : Electrical Pumping .................... 3-12 3.4.1 Active Region Design... lasers on the wafer. x Design and Characterization of Optically Pumped Vertical Cavity Surface Emitting Lasers L. Introduction This thesis investigates

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  11. 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.

  12. 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.

  13. Ultrashort pulse generation from vertical cavity surface emitting semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Jasim, Khalil E.

    This work presents the first demonstration of a passively modelocked extended vertical cavity surface emitting laser (VECSEL) diode. Three cavity configurations were used to sustain stable passive modelocking operation: the Z-shaped, V-shaped and linear cavities. A semiconductor saturable absorber mirror (SESAM) used to triggered passive modelocking of the VECSEL diode. The SESAM device was used as a nonlinear high reflector in the Z-shaped and V-shaped cavity configurations, while it served as an output coupler (SESAMOC) in the linear cavity after the substrate was being angle polished and antireflection coated to eliminate any etalon effects. Many examples of VECSEL diode passive modelocking results will be presented. The standard non-collinear second-harmonic autocorrelation technique has been used to measure the generated pulse width, which was as small as 23 psec. The VECSEL-SESAM configuration has generated stable pulse trains at repetition rates ranging from 1 GHz to approximately 6 GHz, depending on the resonator configuration. Modelocking operation was stable and robust as amplitude noise measurements revealed a noise level ˜0.8%. Moreover, harmonic passive modelocking operation has been observed for the first time during the investigation of modelocking dynamics and stability in the regime of strong self-feedback coupling >10%. A reverse biased p-i-n QW device has enabled the generation of a stable pulse train at 15 GHz with pulse duration close to 15 psec and amplitude noise level ˜0.3%. However, due to design limitations of both the active and passive VECSELs, driving the system to produce repetition rates close to 20 GHz resulted in pulse amplitude variation and an unavoidable DC background. These initial results suggest the possibility of design and fabrication of an integrated or monolithic structure, which may lead to operation of the device at repetition rates beyond 50 GHz with sub-ps pulse durations. Although our VECSEL diode emits 980 nm

  14. 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

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

    DOEpatents

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

    2003-05-20

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

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

    SciTech Connect

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

    2011-06-15

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

  17. 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.

  18. 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.

  19. Single orbital angular momentum mode emission from vertical cavity surface emitting laser by optical feedback

    NASA Astrophysics Data System (ADS)

    Toda, Y.; Moriya, H.; Shigematsu, K.; Yamane, K.; Morita, R.; Awaji, Y.

    2017-04-01

    Single angular momentum (OAM) mode emissions from a vertical cavity surface emitting laser (VCSEL) were demonstrated by an external optical feedback using computer generated holograms, which are optimized on the OAM modal gain of the free-running VCSEL. Side-mode suppression ratio of more than 23 dB was achieved for the OAM modes with l = +/-1.

  20. 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.

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

    DOEpatents

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

    2003-08-19

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

  2. 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.

  3. Spatial distribution of the intensity noise of a vertical-cavity surface-emitting semiconductor laser.

    PubMed

    Bramati, A; Hermier, J P; Khoury, A Z; Giacobino, E; Schnitzer, P; Michalzik, R; Ebeling, K J; Poizat, J P; Grangier, P

    1999-07-01

    We studied anticorrelated quantum fluctuations between the TEM(00) and the TEM(01) transverse modes of a vertical-cavity surface-emitting semiconductor laser by measuring the transverse spatial distribution of the laser beam intensity noise. Our experimental results are found to be in good agreement with the predictions of a phenomenological model that accounts for quantum correlations between transverse modes in a light beam.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

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

    SciTech Connect

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

    1999-07-07

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-03-01

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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  10. Two-frequency injection on a multimode vertical-cavity surface-emitting laser.

    PubMed

    Lin, Hong; Pierce, David W; Basnet, Amod J; Quirce, Ana; Zhang, Yu; Valle, Angel

    2011-11-07

    We have studied experimentally effects of two-frequency optical injection on a multimode vertical-cavity surface-emitting laser (VCSEL). The injected signal comes from another VCSEL. Polarization switching (PS) with and without frequency locking occurs for relatively small frequency detuning. Outside the regime of polarization switching, the VCSEL demonstrates two types of instabilities. The instability regions and boundaries of PS of each transverse mode are mapped in the parameter plane of frequency detuning versus injected power.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    PubMed

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

    2011-01-31

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

  13. 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

  14. Monolithic vertical-cavity surface-emitting laser with thermally tunable birefringence

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The birefringence splitting in vertical-cavity surface-emitting lasers offers an opportunity for spintronic-based high-frequency operation. By means of coupling of the carrier spin in the active region with the photons of the laser mode, the device can be excited to oscillations in the degree of circular polarization with a frequency corresponding to the birefringence splitting. On-chip frequency tunability of those oscillations is desirable for future applications. By asymmetric current-induced heating using the elasto-optic effect, we demonstrate a reversible tuning of the birefringence splitting of 45 GHz with less than 3 dB output power penalty.

  15. High-performance optoelectronic switching network with vertical-cavity surface-emitting laser arrays

    SciTech Connect

    Fyodorov, V B

    2003-03-31

    A schematic solution is proposed for creating a highly efficient switching network with fully connected switching topology for use in supercomputers and telecommunication systems. An important characteristic of this solution is the use of vertical-cavity surface-emitting semiconductor laser arrays and polarising beamsplitters. Estimates show that the commercially available elemental base can be used for a practical realisation of an optoelectronic switching network with basic parameters and functional properties that are superior to those in known electronic analogues. (laser applications and other topics in quantum electronics)

  16. Room-temperature 2D semiconductor activated vertical-cavity surface-emitting lasers.

    PubMed

    Shang, Jingzhi; Cong, Chunxiao; Wang, Zilong; Peimyoo, Namphung; Wu, Lishu; Zou, Chenji; Chen, Yu; Chin, Xin Yu; Wang, Jianpu; Soci, Cesare; Huang, Wei; Yu, Ting

    2017-09-14

    Two-dimensional (2D) semiconductors are opening a new platform for revitalizing widely spread optoelectronic applications. The realisation of room-temperature vertical 2D lasing from monolayer semiconductors is fundamentally interesting and highly desired for appealing on-chip laser applications such as optical interconnects and supercomputing. Here, we present room-temperature low-threshold lasing from 2D semiconductor activated vertical-cavity surface-emitting lasers (VCSELs) under continuous-wave pumping. 2D lasing is achieved from a 2D semiconductor. Structurally, dielectric oxides were used to construct the half-wavelength-thick cavity and distributed Bragg reflectors, in favour of single-mode operation and ultralow optical loss; in the cavity centre, the direct-bandgap monolayer WS2 was embedded as the gain medium, compatible with the planar VCSEL configuration and the monolithic integration technology. This work demonstrates 2D semiconductor activated VCSELs with desirable emission characteristics, which represents a major step towards practical optoelectronic applications of 2D semiconductor lasers.Two-dimensional materials have recently emerged as interesting materials for optoelectronic applications. Here, Shang et al. demonstrate two-dimensional semiconductor activated vertical-cavity surface-emitting lasers where both the gain material and the lasing characteristics are two-dimensional.

  17. 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.

  18. 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.

  19. Vertical-cavity surface-emitting lasers for flip-chip packaged vertical optical interconnects

    NASA Astrophysics Data System (ADS)

    O'Keefe, Sean S.; Schaff, William J.; Eastman, Lester F.

    1994-06-01

    Vertical cavity surface emitting lasers (VCSELs) have been fabricated and studied as the optical sources in a vertical optical interconnect application. The VCSELs are to replace LEDs that are currently used in a proof-of-concept demonstration. The advantages of VCSELs ares better power efficiency as sources, higher optical powers, focused beam output, monochromatic operation, and higher modulation bandwidth. The VCSELs used in this project are the first to implement continuously sinusoidally graded interface mirrors grown by molecular beam epitaxy. material parameters, device results, and interconnect implications are presented.

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

    NASA Astrophysics Data System (ADS)

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

    1995-09-01

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

  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. Single orbital angular mode emission from externally feed-backed vertical cavity surface emitting laser

    NASA Astrophysics Data System (ADS)

    Toda, Y.; Moriya, A.; Yamane, K.; Morita, R.; Shigematsu, K.; Awaji, Y.

    2017-09-01

    The single orbital angular momentum mode emission from a commercially available broad-area vertical cavity surface emitting laser (VCSEL) is realized with an optical feedback technique using a spatial light modulator, where a computer generated hologram (CGH) is optimized by taking into account the mode properties of the external cavity VCSEL. The flexibility with which the chirality of the orbital angular momentum mode can be selected is also demonstrated simply by changing the chirality of the CGH. The technique is very simple and easily applicable to other VCSELs without processing.

  4. 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.

  5. 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%.

  6. 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.

  7. Birefringent vertical cavity surface-emitting lasers: toward high-speed spin-lasers

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) provide novel opportunities to overcome several limitations of conventional, purely charge-based semiconductor lasers. Presumably the highest potential lies in the spin-VCSEL's capability for ultrafast spin and polarization dynamics which can be significantly faster than the intensity dynamics in conventional devices. By injecting spin-polarized carriers, these coupled spin-photon dynamics can be controlled and utilized for high-speed applications. While relaxation oscillations provide insights in the speed and direct modulation bandwidth of conventional devices, resonance oscillations in the circular polarization degree step in for the spin and polarization dynamics in spin-VCSELs. These polarization oscillations can be generated using pulsed spin injection and achieve much higher frequencies than the conventional intensity relaxation oscillations in these devices. Furthermore polarization oscillations can be switched on and off and it is possible to generate short polarization pulses, which may represent an information unit in polarization-based optical communication. The frequency of polarization oscillations is mainly determined by the birefringence-induced mode splitting between both orthogonal linearly polarized laser modes. Thus the polarization modulation bandwidth of spin-VCSELs can be increased by adding a high amount of birefringence to the cavity, for example by incorporating mechanical strain. Using this technique, we could demonstrate tunable polarization oscillations from 10 to 40 GHz in AlGaAs-based 850nm VCSELs recently. Furthermore a birefringence-induced mode splitting of more than 250 GHz could be demonstrated experimentally. Provided that this potential for ultrafast dynamics can be fully exploited, birefringent spin-VCSELs are ideal devices for fast short-haul optical interconnects. In this paper we review our recent progress on polarization dynamics of birefringent spin

  8. Resonance-free optical response of a vertical cavity transistor laser

    NASA Astrophysics Data System (ADS)

    Feng, M.; Wu, Cheng-Han; Wu, M. K.; Wu, Chao-Hsin; Holonyak, N.

    2017-09-01

    Optical resonance in a semiconductor laser is a major limitation in high speed data communications, resulting in bit error rate degradation and requiring additional power consuming error-correction circuits to counter these effects. In this work, we report the microwave bandwidth measurement of a vertical cavity transistor laser with an oxide-confined aperture of 4.7 × 5.4 μm2 and demonstrate a 3 dB bandwidth of 11 GHz resonance-free optical response via base-current or collector-voltage modulation. The emission spectra exhibit single-mode operation around 970 nm with a narrow linewidth of Δλ ˜ 0.23 Å (cavity Q of 42 216). The resonance-free optical response is explained by the absence of carrier "accumulating" due to the fast base electron-hole recombination lifetimes and a gradient in the minority carrier charge in the transistor active mode.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-11-01

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

  12. Bistable Output from a Coupled-Resonator Vertical-Cavity Laser Diode

    SciTech Connect

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

    2000-07-20

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

  13. 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.}

  14. 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.

  15. 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.

  16. 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.

  17. Radiation resistance of GaAs-GaAlAs vertical cavity surface emitting lasers

    SciTech Connect

    Jabbour, J.; Zazoui, M.; Sun, G.C.; Bourgoin, J.C.; Gilard, O.

    2005-02-15

    The variations of the optical and electrical characteristics of a vertical cavity surface emitting laser based on GaAs quantum wells have been monitored versus irradiation with 1 MeV electrons. The results are understood by the introduction of nonradiative recombination centers in the wells whose characteristics, capture cross section for minority carriers times their introduction rate, can be determined. A similar study performed for proton irradiation shows that the results can be explained in the same way when the introduction rate of the defects is replaced by the proton energy loss into atomic collisions. These results allow us to deduce the equivalence between electron and proton irradiations: A flux of 1 proton cm{sup -2} which loses an energy E{sub nl} (eV) into atomic collisions is equivalent to a fluence of about 9x10{sup -2} E{sub nl} cm{sup -2}, 1 MeV electrons.

  18. Comprehensive vertical-cavity surface-emitting laser model for optical interconnect transceiver circuit design

    NASA Astrophysics Data System (ADS)

    Wang, Binhao; Sorin, Wayne V.; Palermo, Samuel; Tan, Michael R. T.

    2016-12-01

    Directly modulated vertical-cavity surface-emitting lasers (VCSELs) are commonly used in short-reach optical interconnect applications. To enable efficient optical interconnect transceiver systems operating at data rates up to 25 Gb/s and beyond, cosimulation environments, which allow for the optimization of driver circuitry with accurate compact VCSEL models, are necessary. A comprehensive VCSEL model, which captures thermally dependent electrical and optical dynamics and provides direct current, small-, and large-signal simulation capabilities with self-consistency, is presented. The device's electrical behavior is described with an equivalent circuit, which captures both large-signal operation and electrical parasitics, while the optical response is captured with a rate-equation-based model. Bias and temperature dependencies are incorporated into both key electrical and optical model parameters. Experimental verification of the model is performed at 25 Gb/s with a 990-nm VCSEL to study the impact of bias current level and substrate temperature.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  2. Green monolithic II-VI vertical-cavity surface-emitting laser operating at room temperature

    NASA Astrophysics Data System (ADS)

    Kruse, C.; Ulrich, S. M.; Alexe, G.; Roventa, E.; Kröger, R.; Brendemühl, B.; Michler, P.; Gutowski, J.; Hommel, D.

    2004-02-01

    The realization of a monolithic all II-VI-based vertical cavity surface emitting laser (VCSEL) for the green spectral region is reported. Optically pumped lasing operation was achieved up to room temperature using a planar VCSEL structure. Taking advantage of distributed Bragg-reflectors based on MgS/Zn(Cd)Se superlattices as the low-refractive index material and ZnS0.06Se0.94 layers as the high-index material with a refractive index contrast of n = 0.6, a quality factor exceeding Q = 2000 is reached by using only 18 Bragg periods for the bottom DBR and 15 Bragg periods for the top DBR. The threshold power density is 0.32 MW/cm2 at a temperature of 10 K (emission wavelength 498.5 nm) and 1.9 MW/cm2 at room temperature (emission wavelength 502.3 nm).

  3. Modeling and optimization of single-mode vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    Vertical cavity surface emitting laser (VCSEL) plays a vital role in optical network. The present investigation reports the performance comparison of the modeling of single-mode VCSELs at room temperature for continuous wave operation. VCSEL for the study consists of InGaAsP-based cavity or active region sandwiched between GaAs/AlGaAs top mirror and GaAs/AlAs bottom mirrors with the aim of increasing the power conversion efficiency (PCE), lasing power, and decreasing the threshold current. It is observed that VCSELs with lower diameter are most suitable to achieve energy-efficient operation. The PCE obtained is ˜50% for the proposed single-mode VCSELs. The proposed VCSELs are suitable for short-reach optical interconnects such as chip-to-chip and board-to-board communication in high-performance computers.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  6. Recent progress of vertical-cavity surface emitting lasers: wavelength engineering and new functions

    NASA Astrophysics Data System (ADS)

    Koyama, Fumio

    2004-10-01

    Vertical cavity surface emitting lasers (VCSELs) have been extensively developed and are now key devices in local area networks based on multi-mode optical fibers. Long wavelength VCSELs are currently attracting much interest for use in single-mode fiber metropolitan area and wide area networks. Also, parallel data links including board-to-board interconnections with low threshold VCSEL arrays are also under development. Low threshold single-mode VCSEL arrays will enable us to realize parallel optical interconnects with low power consumption. We have developed highly strained GaInAs/GaAs QW VCSELs emitting at 1.1-1.2 mm band. Excellent temperature characteristics have been realized. We present long wavelength GaInAs VCSELs on GaAs substrates, enabling uncooled operation for high speed data transmission in single-mode fibers. Also, we will discuss a possibility of isolator-free operations of single-mode VCSELs. In addition, we demonstrated a single-mode multiple-wavelength VCSEL array on a patterned GaAs substrate for the wavelength engineering of VCSELs. The maximum lasing span of arrays is over 190 nm. Densely integrated multi-wavelength arrays are presented. Tunable micromachined VCSELs are also attracting much interest for WDM networking, because micromachined tunable VCSELs enable wide continuous tuning. We proposed and demonstrated a micromachined tunable vertical cavity with a strain control layer, which gives us novel functions including temperature insensitive operation, thermal wavelength tuning, and so on. We also propose and demonstrate injection-locked VCSELs for all-optical signal processing. Some results on optical inverters, optical bistable devices and optical regenerators will be reported. Toward other applications including optical storages and sensing, we will describe metal nano-aperture VCSELs for near-field optics.

  7. Molecular beam epitaxy of indium phosphide-based alloys for long-wavelength vertical cavity lasers

    NASA Astrophysics Data System (ADS)

    Buell, David Arthur

    Long-wavelength vertical cavity lasers (VCLs) can be an excellent source for fiber-optic telecommunications transmitters, thanks to their small footprint, ease of manufacturing, wafer scale testing, optical fiber coupling efficiency, and direct modulation bandwidth. Several approaches to realizing long-wavelength VCLs at both important telecommunications wavelengths, 1310 nm and 1550 nm, have been tried, including GaInNAs-based GaAs lasers and wafer bonded AlGaAs/InP structures. Both efforts are geared towards overcoming a traditional shortcoming of InP-based VCLs: the lack of high index-contrast distributed Bragg reflector (DBR) mirrors that can be grown lattice-matched to the substrate. Previously we had demonstrated 1550 nm VCLs grown via molecular beam epitaxy (MBE) which used AlGaAsSb alloys as the DBR material, and which laced up to 88°C with greater than 1mW output power at room temperature and 23% differential quantum efficiency. Devices operating at 1310 nm are now desired, to demonstrate the flexibility of this technology platform. In this dissertation the materials growth optimization for these associated alloys is described; in particular, the growth diagram for InP is defined. Interfaces between the various alloys of AlGaAsSb, AlInGaAs, and InP are explored and optimized to reduce defect density and roughness. Active region design and optimization for both 1310 nm and 1550 nm emission is presented as well. Aperture design to reduce optical scattering losses as low as possible is also outlined, with conclusions for optimum aperture thickness and placement. A tunnel junction was used as the aperture for our 1310 run VCLs, to combine optical and current confinement into one layer. This thin (35 nm) tunnel junction was then selectively etched with respect to the surrounding InP cladding, forming an air-gap aperture with ultra-low loss. A 1310 nm VCL grown using optimized MBE methods and interfacial transitions and processed to include the thin tunnel

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  14. Monolithically integrated vertical-cavity lasers and resonant detectors for free-space optical interconnects

    NASA Astrophysics Data System (ADS)

    Louderback, Duane Alan

    In this dissertation, a new technique for integrating vertical cavity lasers and resonant-cavity photodetectors for free-space optical interconnects is explored. The work starts with an overview of the device requirements for free-space optical interconnects, specifically the need for integrated VCLs and detectors that are compatible with flip-chip bonding and microlens integration. The lack of a suitable integration technique lead to the development of a new method of integrating VCLs and detectors. Part of the VCL bottom mirror is oxidized, while the detector structure is left unoxidized, enabling different bottom mirror reflectivities to be achieved. This difference in bottom mirror reflectivity allows individually designed VCLs and resonant-cavity detectors to be monolithically integrated. Since the reflectivity difference is realized in the bottom mirror, the devices have through-the substrate emission and detection, making flip-chip bonding and microlens integration straightforward. High performance VCLs and resonant-cavity detectors were fabricated using this integration technique. A comprehensive analysis of the devices is performed with the goal of broadening the detector optical bandwidth without causing adverse effects on other device parameters. DC and high-speed device characteristics are presented, including the results of a free-space optical link where the operating temperature of the VCL and detector were independently varied over a wide range. These results demonstrate the potential of this integration technique for meeting the device requirements of free-space optical interconnect systems.

  15. 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.

  16. 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.

  17. Few-mode vertical-cavity surface-emitting lasers for space-division multiplexing

    NASA Astrophysics Data System (ADS)

    Su, Yaman; Yu, Lijuan; Guo, Xia; Zhang, Xing; Liu, Jianguo; Zhu, Ninghua

    2017-09-01

    In order to choose the proper radius of oxide aperture for few-mode vertical-cavity surface-emitting lasers (VCSELs), the influences of oxide aperture size on the multi-transverse-mode behaviors are investigated in detail. By establishing the effective refractive index model to simulate VCSELs with different radii of oxide apertures, the wavelength and corresponding order of different modes are obtained. VCSELs with three kinds of oxide apertures are manufactured. Then the multi-transverse-mode spectra and near-field are measured. It is found that when the radius is between 1.5 and 4.5 {{μ }}{{m}}, few-mode VCSELs can be implemented. The 2.5 {{μ }}{{m}} VCSEL manufactured in this paper only emits LP01 mode and LP21 mode. Since the space distance between the two modes is 2 {{μ }}{{m}}, it is expected to realize direct-modulation few-mode VCSELs by channel etching or ion implantation between the two modes. Project supported by the National Basic Research Program of China (No. 2014CB3400102), the National Natural Science Foundation of China (No. 61335004), the National High Technology Research and Development Program of China (No. 2015AA017101), and the National Key Technologies R & D Program of China (No. 2016YFB0400603).

  18. Stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Li, Nianqiang; Susanto, H.; Cemlyn, B. R.; Henning, I. D.; Adams, M. J.

    2017-07-01

    A detailed stability and bifurcation analysis of spin-polarized vertical-cavity surface-emitting lasers (VCSELs) is presented. We consider both steady-state and dynamical regimes. In the case of steady-state operation, we carry out a small-signal (asymptotic) stability analysis of the steady-state solutions for a representative set of spin-VCSEL parameters. Compared with full numerical simulation, we show this produces surprisingly accurate results over the whole range of pump ellipticity, and spin-VCSEL bias up to 1.5 times the threshold. We then combine direct numerical integration of the extended spin-flip model and standard continuation technique to examine the underlying dynamics. We find that the spin VCSEL undergoes a period-doubling or quasiperiodic route to chaos as either the pump magnitude or polarization ellipticity is varied. Moreover, we find that different dynamical states can coexist in a finite interval of pump intensity, and observe a hysteresis loop whose width is tunable via the pump polarization. Finally we report a comparison of stability maps in the plane of the pump polarization against pump magnitude produced by categorizing the dynamic output of a spin VCSEL from time-domain simulations, against supercritical bifurcation curves obtained by the standard continuation package auto. This helps us better understand the underlying dynamics of the spin VCSELs.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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

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

    PubMed

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  6. Dynamic and spectral characteristics of vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Giudice, Gustavo Enrique

    2000-08-01

    Small size, small beam divergence, very low threshold current, and wide modulation bandwidth make vertical- cavity surface-emitting lasers (VCSELs) very attractive for optical communications and interconnects. However, their carrier dynamics such as threshold carrier densities and recombination processes are still not well known. Many of these parameters can be obtained from carrier lifetime measurements. This work presents the results of experimental studies obtained with a recently developed experimental technique for accurate and reliable measurements of carrier lifetimes in VCSELs. This technique is based on a high frequency impedance model of quantum-well lasers. Results on differential carrier lifetimes of gain-guided (λ = 850 nm) and index-guided (λ = 980 nm) VCSELs were obtained from laser impedance measurements at subthreshold currents. We also show how to use this new technique to study the effect of lateral diffusion of carriers in index-guided VCSELs with the device size as a parameter. Different applications of VCSELs use different information coding schemes and require lasers with different characteristics. Digital transmission at high data rates requires VCSELs with high modulation bandwidth and very stable single-wavelength emission. Since VCSELs have a relatively large transverse dimension, the mode structure resulting from optical feedback could be strongly affected, generating either multimode or single mode emission, depending on the amount of feedback. Our work demonstrated single-mode operation of a VCSEL using a fiber Bragg grating as an external reflector. A side mode suppression ratio of 30dB was obtained under static and dynamic bias conditions for a wide range of modulation frequencies. Analog transmission using VCSELs has large potential for communication applications. Standard cable television systems, radar links, and personal communication systems utilize analog modulation of the signal but require low intermodulation distortion and

  7. 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

  8. Graded index profiles and loss-induced single-mode characteristics in vertical-cavity surface-emitting lasers with petal-shape holey structure

    NASA Astrophysics Data System (ADS)

    Liu, An-Jin; Qu, Hong-Wei; Chen, Wei; Jiang, Bin; Zhou, Wen-Jun; Xing, Ming-Xin; Zheng, Wan-Hua

    2011-02-01

    The 850-nm oxide-confined vertical-cavity surface-emitting lasers with petal-shape holey structures are presented. An area-weighted average refractive index model is given to analyse their effective index profiles, and the graded index distribution in the holey region is demonstrated. The index step between the optical aperture and the holey region is obtained which is related merely to the etching depth. Four types of holey vertical-cavity surface-emitting lasers with different parameters are fabricated as well as the conventional oxide-confined vertical-cavity surface-emitting laser. Compared with the conventional oxide-confined vertical-cavity surface-emitting laser without etched holes, the holey vertical-cavity surface-emitting laser possesses an improved beam quality due to its graded index distribution, but has a lower output power, higher threshold current and lower slope efficiency. With the hole number increased, the holey vertical-cavity surface-emitting laser can realize the single-mode operation throughout the entire current range, and reduces the beam divergence further. The loss mechanism is used to explain the single-mode characteristic, and the reduced beam divergence is attributed to the shallow etching. High coupling efficiency of 86% to a multi-mode fibre is achieved for the single-mode device in the experiment.

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

    SciTech Connect

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

    1997-05-01

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

  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. Static, dynamic, and noise characteristics of vertical- cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Law, Joanne Y.

    1998-07-01

    An important aspect of vertical-cavity surface-emitting lasers (VCSELs) that needs to be improved is its stable operation in a single transverse mode. Due to relatively large dimensions of VCSELs (~10 μm radius), spatial hole-burning and carrier diffusion affect device performance significantly, especially because VCSELs often operate in several transverse modes at high injection currents. In this thesis, a comprehensive numerical study of such spatial effects on the static, dynamic, and noise characteristics of VCSELs is presented. The computer model includes the spatial dependences of both the optical field and the carrier density. Device characteristics are analyzed under different operating conditions, including continuous-wave (CW) operation, gain-switched operation, optical feedback, and optical injection. Both single-mode and two-mode operations are analyzed. Under CW operation, transverse-mode competition induced by spatial hole-burning is found to affect the static and noise characteristics significantly. In particular, transverse-mode competition affects the mode-partition noise. Under single-mode gain-switched operation, it is shown that by using an appropriate electrical contact, spatial hole-burning can be avoided and shorter pulses can be obtained. Under two-mode gain-switched operation, transverse-mode competition gives rise to rich nonlinear dynamics. The effect of external influence has also been studied. It is found that optical feedback or optical injection can force a two-mode VCSEL to operate in a single transverse mode under appropriate conditions. However, distant feedback or injection outside the locking region can destabilize the CW operation and lead to interesting nonlinear dynamics. The feedback strength and the injection power at which oscillations occur depend critically on the strength of intermodal coupling. In general, results indicate that strong intermodal coupling reduces the sensitivity of the VCSEL towards external influence

  12. 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)

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

    NASA Astrophysics Data System (ADS)

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

    1998-04-01

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

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

    SciTech Connect

    Ackemann, T.; Sondermann, M.

    2001-06-04

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

  15. Monolithic III-V and hybrid polysilicon-III-V microelectromechanical tunable vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Ochoa, Edward M.; Lott, James A.; Nelson, Thomas R., Jr.; Harvey, M. C.; Raley, J. A.; Stintz, Andreas; Malloy, Kevin J.

    2003-04-01

    We report our progress on the design and fabrication of electrostatically-actuated microelectromechanical (MEM) tunable wavelength filters and vertical cavity surface-emitting lasers (VCSELs). We investigate both an all-semiconductor monolithic approach and a hybrid approach based on the combination of conventional polysilicon microelectromechanical systems (MEMS) and III-V semiconductor thin-film distributed Bragg reflector (DBR) and VCSEL structures. In the tunable hybrid structures the III-V semiconductor layers are flip-bonded onto specially designed polysilicon foundry MEMS structures and separated from their lattice-matched parent substrates by a novel post-bonding lift-off process.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  19. Two-dimensional integration of a vertical-cavity surface-emitting laser and photodetectors for position sensing.

    PubMed

    Giannopoulos, Antonios V; Kasten, Ansas M; Long, Christopher M; Chen, Chen; Choquette, Kent D

    2008-09-01

    Noncontact long-range position sensing is desirable for a number of applications. We have designed and fabricated a monolithically integrated vertical-cavity surface-emitting laser (VCSEL) and p-type/intrinsic/n-type (PIN) photodetectors for optical position sensing. Calculations using the reflection from a periodic metallic corrugation as a position gauge indicate resolution in the submicron regime. High device uniformity is obtained using novel fabrication techniques. We observe a threshold current of 0.52 mA for the VCSELs and a detector responsivity of 0.38 A/W at 840 nm. The optical cross talk between VCSELs and detectors is also quantified.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

  7. 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.

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

    SciTech Connect

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

    2016-03-15

    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.

  9. 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.

  10. 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.

  11. 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.

  12. Simultaneous blue and green lasing of GaN-based vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Xu, R. B.; Mei, Y.; Zhang, B. P.; Ying, L. Y.; Zheng, Z. W.; Hofmann, W.; Liu, J. P.; Yang, H.; Li, M.; Zhang, J.

    2017-10-01

    Using a quantum dot in quantum well (QD-in-QW) active region, current injected GaN-based vertical-cavity surface-emitting lasers (VCSELs) lasing simultaneously in blue and green were achieved at room temperature (RT). Lasing was first achieved at 545 nm with a threshold current of ∼2 μA, and with a further increase of current, another lasing peak at 430 nm came out with a threshold current of ∼5 mA. The energy difference between the two lasing peaks originating from QDs and QWs is 609 meV. According to the spontaneous emission spectra measured under different injected currents, a model of energy states in QD-in-QW is proposed to describe the distribution of carriers in this structure. Using this model, the evolution of emission intensity, shift of peak energy, variation of linewidth and the lasing characteristics can be well explained.

  13. Molecular beam epitaxial regrowth on diffraction gratings for vertical-cavity, surface-emitting laser-based integrated optoelectronics

    SciTech Connect

    Pickrell, G.W.; Xu, C.F.; Louderback, D.A.; Lin, H.C.; Fish, M.A.; Hindi, J.J.; Simpson, M.C.; Guilfoyle, P.S.; Zhang, Z.H.; Hsieh, K.C.

    2004-10-15

    Epitaxial regrowth techniques, using molecular beam epitaxy, were optimized for the inclusion of submicron diffraction gratings within a vertically resonant structure. Various growth conditions including chemical surface preparation, growth rate, and regrown interfacial structure were studied to determine the quality of the regrown materials and structures. Characteristics such as dislocation density and growth planarity (flatness of the regrown layers) were of particular importance due to the vertical geometry and resonance requirements of the structure. Threading dislocation densities of {approx_equal}3x10{sup 6} cm{sup -2} were measured, by means of transmission electron microscopy, in the regrown structures using optimized regrowth processes. Layer thickness variations, due to growth on nonplanar surfaces (diffraction gratings), were characterized using modeling and optical reflectometry. With these results, inclusion of diffraction gratings has been demonstrated with the accurate control over layer thickness needed for use in vertically oriented devices such as vertical-cavity, surface-emitting lasers, and resonant cavity photodetectors.

  14. 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.

  15. Emission characteristics of high-gain GaN-based Vertical-Cavity Surface-Emitting Lasers

    NASA Astrophysics Data System (ADS)

    Weng, Guoen; Chen, Shaoqiang; Ito, Takashi; Akiyama, Hidefumi; Hu, Xiaobo; Zhang, Baoping

    2017-06-01

    GaN-based vertical-cavity surface-emitting lasers (VCSELs) with high optical gain and short cavity lifetime are favorable for the generation of ultra-short pulses in the blue and green regions. In our previous works, 6 and 2 picosecond short-pulses have been generated from gain-switched InGaN VCSELs with 3- and 10-period InGaN/GaN quantum wells (QWs) in the active layers by using an up-conversion measurement system. To further increase the gain of the VCSEL for the generation of even shorter pulses, 20-period InGaN/GaN QWs samples were fabricated. The emission characteristics of these high-gain VCSELs were investigated and analyzed under the optical pumping at room temperature.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  17. 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.

  18. 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.

  19. 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.

  20. Energy-efficient vertical-cavity surface-emitting lasers (VCSELs) for "green" data and computer communication

    NASA Astrophysics Data System (ADS)

    Moser, Philip; Lott, James A.; Wolf, Philip; Larisch, Gunter; Payusov, Alexey; Fiol, Gerrit; Ledentsov, Nikolay N.; Hofmann, Werner; Bimberg, Dieter

    2012-03-01

    Record energy-efficient oxide-confined 850-nm single mode and quasi-single mode vertical-cavity surface-emitting lasers (VCSELs) for optical interconnects are presented. Error-free performance at 17 Gb/s is achieved with record-low dissipated power of only 69 fJ/bit. The total energy consumption is only 93 fJ/bit. Transmission lengths up to 1 km of multimode optical fiber were achieved. Our commercial quasi-single mode devices achieve error-free operation at 25 Gb/s across up to 303 m of multimode fiber. To date our VCSELs are the most energy-efficient directly modulated light-sources at any wavelength for data transmission across all distances up to 1 km of multimode optical fiber.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  3. 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.

  4. 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.

  5. 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.

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

    PubMed Central

    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

  7. The Effects of Optical Feedback on Polarization of Vertical Cavity Surface Emitting Lasers

    DTIC Science & Technology

    1993-12-01

    evidence for this comes from Sample #2, which was pumped with the Ti:Sapphire and then a much steadier diode laser . While coherence length with the...Ti:Sapphire pump was I cm, with the diode laser pump it was 10 cm. Some other factors caused rapid, large fluctuations in VCSEL intensity, leading to coherence...feasible, pumping with a diode laser at the appropriate wavelength will help considerably, as demonstrated in this experiment. In fact, combining a

  8. Ultrafast nanomechanics in vertical cavity surface-emitting lasers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Akimov, Andrey V.; Czerniuk, Thomas; Yakovlev, Dmitri R.; Bayer, Manfred

    2017-02-01

    The existence of both optical and sub-THz nanomechanical resonances in the same laser microcavity results in strong photon-phonon interaction, and may be explored for the ultrafast control of vertical lasers. In the talk the experiments involving the injection of picosecond strain pulses into optically and electrically pumped vertical lasers, and monitoring of the modulated output laser intensity will be discussed. The results of three recent experiments will be presented: • In the experiments with an optically pumped quantum dot laser, an increase of the lasing output induced by strain pulses by two orders of magnitude has been observed on a picosecond time scale. Such strong and ultrafast increase is due to the inhomogeneous quantum dot ensemble with a spectral broadening much larger than the optical cavity mode width. Thus, the optical resonance required for lasing is achieved for a tiny dot fraction only while non-resonant dots store optical excitation for long time. The strain pulse brings "non-resonant" quantum dots into the resonance with the cavity mode and the stored energy releases almost simultaneously in a form of the intense laser pulses. • Experiments with electrically pumped micropillar lasers show the modulation of the emission wavelength on the frequencies equal to the resonant GHz nanomechanical modes of the micropillar. • Experiments with a quantum well vertical laser showed intensity modulation with the mechanical resonance frequencies (20-40 GHz) of the optomechanical nanoresonator. Prospective application for nanophotonics are discussed.

  9. 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.

  10. Coherence switching of a vertical-cavity semiconductor-laser for multimode biomedical imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cao, Hui; Knitter, Sebastian; Liu, Changgeng; Redding, Brandon; Khokha, Mustafa Kezar; Choma, Michael Andrew

    2017-02-01

    Speckle formation is a limiting factor when using coherent sources for imaging and sensing, but can provide useful information about the motion of an object. Illumination sources with tunable spatial coherence are therefore desirable as they can offer both speckled and speckle-free images. Efficient methods of coherence switching have been achieved with a solid-state degenerate laser, and here we demonstrate a semiconductor-based degenerate laser system that can be switched between a large number of mutually incoherent spatial modes and few-mode operation. Our system is designed around a semiconductor gain element, and overcomes barriers presented by previous low spatial coherence lasers. The gain medium is an electrically-pumped vertical external cavity surface emitting laser (VECSEL) with a large active area. The use of a degenerate external cavity enables either distributing the laser emission over a large ( 1000) number of mutually incoherent spatial modes or concentrating emission to few modes by using a pinhole in the Fourier plane of the self-imaging cavity. To demonstrate the unique potential of spatial coherence switching for multimodal biomedical imaging, we use both low and high spatial coherence light generated by our VECSEL-based degenerate laser for imaging embryo heart function in Xenopus, an important animal model of heart disease. The low-coherence illumination is used for high-speed (100 frames per second) speckle-free imaging of dynamic heart structure, while the high-coherence emission is used for laser speckle contrast imaging of the blood flow.

  11. 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.

  12. 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

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

    PubMed Central

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

    2012-01-01

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

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

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

    SciTech Connect

    Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

    2016-01-15

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

  17. 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.

  18. 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

  19. 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.

  20. Numerical analysis on current and optical confinement of III-nitride vertical-cavity surface-emitting lasers.

    PubMed

    Lai, Ying-Yu; Huang, Shen-Che; Ho, Tsung-Lin; Lu, Tien-Chang; Wang, Shing-Chung

    2014-04-21

    We report on the numerical analysis of the electrical and optical properties of current-injected III-nitride based vertical-cavity surface-emitting lasers (VCSELs) with three types of current confinement schemes: the conventional planar-indium tin oxide (ITO) type, the AlN-buried type without ITO, and the hybrid type. The proposed hybrid structure, which combines an ITO layer and an intracavity AlN aperture, exhibits not only uniform current distribution but also enhanced lateral optical confinement. Thus, the hybrid type design shows remarkably better performance including lower threshold current and series resistance compared with the planar-ITO type and the AlN-buried type. Furthermore, the multi-transverse mode lasing behavior induced by strong index guiding of the AlN aperture is suppressed to single transverse mode operation by reducing the aperture size. Such design provides a powerful solution for the high performance III-N based VCSELs and is also viable by using current state of the art processing techniques.

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

    PubMed

    Valle, A; Sciamanna, M; Panajotov, K

    2007-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  3. InP-based long-wavelength vertical-cavity surface-emitting lasers with buried tunnel junction

    NASA Astrophysics Data System (ADS)

    Lauer, Christian; Ortsiefer, Markus; Shau, Robert; Rosskopf, Jürgen; Böhm, Gerhard; Meyer, Ralf; Amann, Markus-Christian

    2004-07-01

    In this paper we present a device concept for long-wavelength vertical-cavity surface-emitting lasers (VCSELs) in the InGaAlAs/InP material system incorporating a buried tunnel junction (BTJ). A major issue of long-wavelength VCSELs is the dissipation of heat because of the low thermal conductivity of ternary and quaternary alloys. With the BTJ-VCSEL, a significant reduction of the thermal resistance is achieved by the use of a hybrid backside mirror made of a stack of amorphous dielectrics with Au-coating and the monolithic integration of a heat sink. These provide improved heat sinking capability compared to a conventional epitaxial semiconductor DBR. In addition, the tunnel junction facilitates a substitution of most of the p-doped layers by n-doped material, reducing heat generation due to ohmic losses. These features significantly improve the VCSEL characteristics. At 1.55 m wavelength, we demonstrated single-mode cw-output powers of 1.7mW at room temperature [1], multi-mode cw-output powers of 7mW [2], laser operation up to heat sink temperatures of 110 °C [2], and optical data transmission with 10 Gbit/s and low bit error rates [3]. These are record values to the best knowledge of the authors.Using strained quantum wells, the emission wavelength can be tailored to any value in the range between 1.3 m and 2.0 m [4], sample results are presented for the telecommunication wavelengths 1.3 m and 1.55 m, 1.8 m, and the currently upper limit of 2.0 μm. The slight wavelength tuning with driving current is brought about by the tiny volume of the devices and makes VCSELs ideal components for tunable diode laser absorption spectroscopy (TDLAS) [5, 6]. The maximum detuning typically reaches 4 nm (500 GHz).

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

    NASA Astrophysics Data System (ADS)

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

    1998-07-01

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

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

    SciTech Connect

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

    2016-01-18

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Kakuma, Seiichi

    2017-02-01

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

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Mo, Qingwei

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

  13. State bistability between pure- and mixed-mode states in a 1550 nm vertical-cavity surface-emitting laser subject to parallel optical injection

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Chen, Jianjun; Xia, Guangqiong; Wu, Zhengmao

    2017-07-01

    Polarization dynamics in a 1550 nm vertical-cavity surface-emitting laser (1550 nm VCSEL) under parallel optical injection (POI) is investigated experimentally, and we experimentally observe the state bistability (SB) between pure- and mixed-mode states by scanning the injection power along different routes. Such a SB occurs only when the frequency of injection light is lower than that of the excited mode of a free-running 1550 nm VCSEL. Moreover, the effect of frequency detuning on the hysteresis loop width is analyzed.

  14. Impact of relative intensity noise of vertical-cavity surface-emitting lasers on optics-based micromachined audio and seismic sensors.

    PubMed

    Littrell, Robert; Hall, Neal A; Okandan, Murat; Olsson, Roy; Serkland, Darwin

    2007-10-01

    The relative intensity noise of vertical-cavity surface-emitting lasers (VCSELs) in the 100 mHz to 50 kHz frequency range is experimentally investigated using two representative single-mode VCSELs. Measurements in this frequency range are relevant to recently developed optical-based micromachined acoustic and accelerometer sensing structures that utilize VCSELs as the light source to form nearly monolithic 1 mm3 packages. Although this frequency regime is far lower than the gigahertz range relevant to optical communication applications for which VCSELs are primarily designed, the intensity noise is found to be low and well within the range of cancellation using basic reference detection principles.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  19. Bifurcation structure of cavity soliton dynamics in a vertical-cavity surface-emitting laser with a saturable absorber and time-delayed feedback

    NASA Astrophysics Data System (ADS)

    Schelte, Christian; Panajotov, Krassimir; Tlidi, Mustapha; Gurevich, Svetlana V.

    2017-08-01

    We consider a wide-aperture surface-emitting laser with a saturable absorber section subjected to time-delayed feedback. We adopt the mean-field approach assuming a single longitudinal mode operation of the solitary vertical-cavity surface-emitting laser (VCSEL). We investigate cavity soliton dynamics under the effect of time-delayed feedback in a self-imaging configuration where diffraction in the external cavity is negligible. Using bifurcation analysis, direct numerical simulations, and numerical path-continuation methods, we identify the possible bifurcations and map them in a plane of feedback parameters. We show that for both the homogeneous and localized stationary lasing solutions in one spatial dimension, the time-delayed feedback induces complex spatiotemporal dynamics, in particular a period doubling route to chaos, quasiperiodic oscillations, and multistability of the stationary solutions.

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2003-08-01

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

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

    PubMed

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

    2015-07-27

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  7. 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

  8. 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.

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

    SciTech Connect

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

    2007-08-15

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

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

    NASA Astrophysics Data System (ADS)

    Coronel, Juan; Varón, Margarita; Rissons, Angélique

    2016-09-01

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

  11. High-Speed and high-power vertical-cavity surface-emitting lasers based on InP suitable for telecommunication and gas sensing

    NASA Astrophysics Data System (ADS)

    Gruendl, Tobias; Zogal, Karolina; Mueller, Michael; Nagel, Robin D.; Jatta, Sandro; Geiger, Kathrin; Grasse, Christian; Boehm, Gerhard; Ortsiefer, Markus; Meyer, Ralf; Meissner, Peter; Amann, Markus-Christian

    2010-10-01

    We present 1.55 μm short-cavity buried-tunnel-junction VCSELs (Vertical-Cavity Surface-Emitting Lasers) with single mode output powers of 6.7 mW at 20°C and 3 mW at 80°C, respectively. Although the device had been predominantly optimized for high-power applications and a proper heat management, we are also observing a 3dB-cut-off frequency of more than 11 GHz and side mode suppression ratios (SMSRs) beyond 54 dB over the whole temperature range. The tuning range of the devices can be increased from 7 nm based on gain tuning to several tens of nanometers when replacing the top DBR by a micro-electro-mechanical system (MEMS) distributed Bragg reflector (DBR) composed of semiconductor or dielectric material being thermally actuated for changing the cavity length. These devices are perfectly suitable for telecommunication and gas sensing applications and represent outstanding devices for the so called tunable diode laser absorption spectroscopy (TDLAS) technique.

  12. Experimental Investigation and Computer Modeling of Optical Switching in Distributed Bragg Reflector and Vertical Cavity Surface Emitting Laser Structures.

    DTIC Science & Technology

    1995-12-01

    Panish. Heterostructure Lasers, Part A: Fundamental Principles. Quantum Electronics : Principles and Applications, Orlando: Academic Press, Inc., 1978...John Wiley & Sons, 1978. 15. Gibbs, H.M. Optical Bistability: Controlling Light with Light. Quantum Electronics - Principles and Applications, Orlando

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-07-01

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

  18. Robustness versus thermal effects of single-mode operation of vertical-cavity surface-emitting lasers with engineered leakage of high-order transverse optical modes

    NASA Astrophysics Data System (ADS)

    Kalosha, V. P.; Shchukin, V. A.; Ledentsov, N. N.; Kropp, J.-R.; Ledentsov, N. N.

    2017-02-01

    Design of the oxide-confined vertical cavity surface emitting laser (VCSEL) with enhanced engineered lateral leakage of high-order transverse optical modes is studied by three-dimensional optical modeling to evaluate the robustness of the leakage selection approach with respect to thermal effects. Both Joule heat and heat generated by the free carrier absorption of the optical mode in the doped semiconductor layers and their impact on the refractive index profile are considered. We show that for typical regimes of the VCSEL design and operation absorption-induced heat exceeds by several times the Joule heat while the shape of the generated heated domains strongly differ. Modeling shows that well defined spectral separation between the transverse optical modes persists upon increase in injection current. Further, upon increase in current the lateral extension of the fundamental mode decreases and the mode shrinks towards the center of the VCSEL structure thus reducing the lateral leakage and increasing the mode lifetime, whereas similar effect for high-order transverse modes is much weaker. Thus the preferred conditions for the lasing of the fundamental mode persist and even improve upon current increase. At high currents the fundamental mode becomes favorable at all aperture diameters, also for those where the cold cavity approximation predicts preference for the excited mode lasing.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

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

    PubMed

    Ogura, Yusuke; Shirai, Nobuhiro; Tanida, Jun

    2002-09-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-06-01

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

  5. 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.

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

    PubMed

    Ju, Young-Gu

    2005-05-16

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

  7. 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.

  8. 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.

  9. InGaAsP/AlGaAs multiple-wavelength vertical-cavity lasers and arrays in the 1.5-μm band fabricated by localized wafer fusion technique

    NASA Astrophysics Data System (ADS)

    Syrbu, Alexei V.; Iakovlev, Vladimir P.; Rudra, Alok P.; Berseth, Claude-Albert; Kapon, Eli E.; Mereuta, Alexandru Z.; Sagnes, Isabelle; Ougazzaden, Abdallah

    2000-02-01

    We have demonstrated InGaAsP/AlGaAs double fused 1.5 micrometers multiple wavelength vertical cavity lasers and arrays in which element definition is obtained by localized fusion. Laser elements emit in continuous wave under electrical and optical pumping. Multiple wavelength single element VCSELs have been fabricated in the same batch taking advantage of layer thickness nonuniformity of InGaAsP/InP material close to the edge of the wafer. To obtain multiple wavelength arrays a controllable cavity length variation using anodic oxidation has been performed. The wavelength span in an 8 by 1 laser array is 10 nm. Single mode operation with more than of 40 dB side mode suppression ratio is characteristic for laser elements in the array.

  10. 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.

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

    PubMed Central

    Choi, Woo June; Wang, Ruikang K.

    2015-01-01

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

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

    PubMed

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

    2016-11-01

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

  13. 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.

  14. 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.

  15. 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.

  16. Visible Vertical Cavity Surface Emitting Lasers

    DTIC Science & Technology

    1993-01-01

    Visible VCSEL ................ 103 3.6 Analysis of Results ............................... 113 3.7 Conclusions .................................. 117 4...Stacks ........... 41 2.4 Estimated Mobility and Conductivity of Selected Epitaxial Layers ....... 58 2.5 Summary of the DBR Voltage Drop Analysis ...wavelength both for the optically pumped hybrid visible VCSEL ............... 114 3.15 Qualitative analysis of the gain versus lasing wavelength results for

  17. Single-mode 850-nm vertical-cavity surface-emitting lasers with Zn-diffusion and oxide-relief apertures for > 50 Gbit/sec OOK and 4-PAM transmission

    NASA Astrophysics Data System (ADS)

    Shi, Jin-Wei; Wei, Chia-Chien; Chen, Jyehong; Ledentsov, N. N.; Yang, Ying-Jay

    2017-02-01

    Vertical-cavity surface-emitting lasers (VCSELs) has become the most important light source in the booming market of short-reach (< 300 meters) optical interconnect (OI). The next generation OI has been targeted at 56 Gbit/sec data rate per channel (CEI-56G) with the total data rate up to 400 Gbit/sec. However, the serious modal dispersion of multi-mode fiber (MMF), limited speed of VCSEL, and its high resistance (> 150 Ω) seriously limits the >50 Gbit/sec linking distance (< 10 m) by using only on-off keying (OOK) modulation scheme without any signal processing techniques. In contrast to OOK, 4-PAM modulation format is attractive for >50 Gbit/sec transmission due to that it can save one-half of the required bandwidth. Nevertheless, a 4.7 dB optical power penalty and the linearity of transmitter would become issues in the 4-PAM linking performance. Besides, in the modern OI system, the optics transreceiver module must be packaged as close as possible with the integrated circuits (ICs). The heat generated from ICs will become an issue in speed of VSCEL. Here, we review our recent work about 850 nm VCSEL, which has unique Zn-diffusion/oxide-relief apertures and special p- doping active layer with strong wavelength detuning to further enhance its modulation speed and high-temperature (85°C) performances. Single-mode (SM) devices with high-speed ( 26 GHz), reasonable resistance ( 70 Ω) and moderate output power ( 1.5 mW) can be achieved. Error-free 54 Gbit/sec OOK transmission through 1km MMF has been realized by using such SM device with signal processing techniques. Besides, the volterra nonlinear equalizer has been applied in our 4-PAM 64 Gbit/sec transmission through 2-km OM4 MMF, which significantly enhance the linearity of device and outperforms fed forward equalization (FFE) technique. Record high bit-rate distance product of 128.km is confirmed for optical-interconnect applications.

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

    NASA Astrophysics Data System (ADS)

    Waldrip, Karen Elizabeth

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

  19. Laser diode technology and applications V; Proceedings of the Meeting, Los Angeles, CA, Jan. 18-20, 1993

    NASA Astrophysics Data System (ADS)

    Renner, Daniel

    Various papers on laser diode technology and its applications are presented. The general topics addressed include: high-power coherent large-aperture sources, vertical-cavity lasers, quantum-well lasers, semiconductor laser reliability, high-power semiconductor lasers, surface-emitting lasers, laser dynamics, and visible and midinfrared semiconductor lasers.

  20. Four-wave mixing and optical phase conjugation in vertical-cavity surface-emitting devices

    NASA Astrophysics Data System (ADS)

    Vansuch, Gregory Joseph

    1997-08-01

    Four-wave mixing (FWM), a nonlinear optical process, was investigated in resonant cavity light emitting diodes (RCLEDs) and vertical cavity surface emitting lasers (VCSELs) below lasing threshold. These semiconductor photonic devices consisted of an optical gain region of quantum wells sandwiched between two distributed Bragg reflector (DBR) mirrors. Pump and probe lasers were injected into the devices to generate FWM. The dependence of FWM on bias current, pump laser power, and spectral and spatial separation between pump and probe lasers was investigated experimentally. A computer model of FWM based on the wave and carrier density equations was developed and agreed well with experimental results. Conjugate reflectivities of 1.0 were obtained in the VCSEL when bias current was below threshold but above transparency. Reasonable conjugate reflectivities were obtained for pump-probe detunings up to 2 GHz in both devices. Noncollinear FWM was performed for the first time in VCSELs or RCLEDs at angles up to 10o. Both experiment and model showed the possibility of generating a strong reflected conjugate signal while minimizing the reflected pump signal. The noncollinear FWM demonstrated the possibility of phase front conjugation for correcting aberrated signals in vertical cavity devices.

  1. 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.

  2. Bidirectional Multimode-Fiber Communication Links Using Dual-Purpose Vertical-Cavity Devices

    NASA Astrophysics Data System (ADS)

    Ingham, Jonathan D.; Penty, Richard V.; White, Ian H.

    2006-03-01

    This paper describes the development of novel multimode-fiber (MMF) communication links that achieve half-duplex bidirectional transmission over a single fiber through the use of 850-nm dual-purpose GaAs vertical-cavity optoelectronic devices. The dual-purpose devices are fabricated by focused-ion-beam micromachining (FIBM) of standard vertical-cavity surface-emitting lasers (VCSELs) and are able to be switched between operation as either efficient laser sources or as resonant-cavity-enhanced avalanche photodetectors. An avalanche multiplication factor of 10 is achieved at a reverse-bias voltage of 12.3 V. A 1.25-Gb/s half-duplex bidirectional data communication link is demonstrated and shown to allow error-free transmission of binary data over 500 m of standard 50-µm-core-diameter MMF. Receiver sensitivities for transceivers based upon these devices are predicted for the first time to be comparable with conventional data communication transceivers. Furthermore, a half-duplex analog bidirectional system is constructed, which permits the transmission of advanced RF modulation formats over MMF. Link characterization by error-vector magnitude (EVM) is described. The dual-purpose vertical-cavity devices are employed for bidirectional transmission of 32-symbol quadrature-amplitude-modulated (32-QAM) signals on a carrier frequency of 2 GHz, relevant to many current wireless local-area network and cellular standards. EVM as low as 1.3% rms is observed for a 600-m link of 62.5-µm-core-diameter MMF.

  3. Near Field and Far Field Effects in the Taguchi-Optimized Design of AN InP/GaAs-BASED Double Wafer-Fused Mqw Long-Wavelength Vertical-Cavity Surface-Emitting Laser

    NASA Astrophysics Data System (ADS)

    Menon, P. S.; Kandiah, K.; Mandeep, J. S.; Shaari, S.; Apte, P. R.

    Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchi's orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchi's orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

  4. Etched Vertical-Cavity Surface Emitting Laser Diodes,

    DTIC Science & Technology

    and two-dimensional array capacity. To date, VCSEL’s with monolithic distributed Bragg reflectors (DBR’s) require current injection through the upper...p-type DBR resulting in a large threshold voltage due to the concomitant series resistance. The voltage drop in the p-type DBR also leads to...quarterwave DBR or tapered doping in the p-type DBR have provided a reduction in the series resistance, but have lead to complicated DBR designs. We have

  5. High efficiency oxide confined vertical cavity surface emitting lasers

    SciTech Connect

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

    1995-08-01

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

  6. 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.

  7. 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.

  8. 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.

  9. Vertical-cavity saturable-absorber intensity modulator

    NASA Astrophysics Data System (ADS)

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

    2003-01-01

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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  12. Diode Laser Arrays

    NASA Astrophysics Data System (ADS)

    Botez, Dan; Scifres, Don R.

    2005-11-01

    Contributors; 1. Monolithic phase-locked semiconductor laser arrays D. Botez; 2. High power coherent, semiconductor laser master oscillator power amplifiers and amplifier arrays D. F. Welch and D. G. Mehuys; 3. Microoptical components applied to incoherent and coherent laser arrays J. R. Leger; 4. Modeling of diode laser arrays G. R. Hadley; 5. Dynamics of coherent semiconductor laser arrays H. G. Winfuland and R. K. Defreez; 6. High average power semiconductor laser arrays and laser array packaging with an emphasis for pumping solid state lasers R. Solarz; 7. High power diode laser arrays and their reliability D. R. Scifres and H. H. Kung; 8. Strained layer quantum well heterostructure laser arrays J. J. Coleman; 9. Vertical cavity surface emitting laser arrays C. J. Chang-Hasnain; 10. Individually addressed arrays of diode lasers D. Carlin.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  14. Cryogenic Infrastructure Upgrade of the Fermilab Magnet and Vertical Cavity Test Facilities

    NASA Astrophysics Data System (ADS)

    Rabehl, R.; Carcagno, R.; Huang, Y.; Norris, B.; Sylvester, C.

    2010-04-01

    The Fermilab Magnet Test Facility (MTF) and the Vertical Cavity Test Facility (VCTF), both located in Industrial Building 1 and serviced by a shared cryogenic infrastructure, provide cryogenic testing of superconducting magnets and superconducting radio-frequency cavities in support of programs such as the Tevatron, US-LHC, LARP, HINS, Project X, and the ILC. While MTF must continue to support a robust magnet test program, VCTF is expected to increase its cavity test throughput by a factor of five, reaching 250 cavity test cycles per year as cavity production ramps up. A cryogenic infrastructure upgrade program has been undertaken in preparation for meeting the challenge of this additional cavity test throughput. The cryogenic infrastructure improvements include dedicated ambient temperature vacuum pumps, a helium compressor, purification skids, and additional helium gas storage. This paper will elaborate on the goals of the upgrade program, the selected equipment, and foreseen integration and operations plans and issues.

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

    PubMed

    Zhang, Haijiang; Wen, Pengyue; Esener, Sadik

    2007-07-01

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

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

    PubMed

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

    2007-10-15

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

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

    SciTech Connect

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

    2008-09-01

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

  18. Electrical addressing and temporal tweezing of localized pulses in passively-mode-locked semiconductor lasers

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    We show that the pumping current is a convenient parameter for manipulating the temporal localized structures (LSs), also called localized pulses, found in passively-mode-locked vertical-cavity surface-emitting lasers. While short electrical pulses can be used for writing and erasing individual LSs, we demonstrate that a current modulation introduces a temporally evolving parameter landscape allowing one to control the position and the dynamics of LSs. We show that the localized pulse drifting speed in this landscape depends almost exclusively on the local parameter value instead of depending on the landscape gradient, as shown in quasi-instantaneous media. This experimental observation is theoretically explained by the causal response time of the semiconductor carriers that occurs on a finite time scale and breaks the parity invariance along the cavity, thus leading to a different paradigm for temporal tweezing of localized pulses. Different modulation waveforms are applied for describing exhaustively this paradigm. Starting from a generic model of passive mode locking based upon delay differential equations, we deduce the effective equations of motion for these LSs in a time-dependent current landscape.

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

    DTIC Science & Technology

    2007-09-01

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

  20. Ultra-Low Threshold Vertical-Cavity Surface-Emitting Lasers for USAF Applications

    DTIC Science & Technology

    2005-01-01

    initiated by Dr . John Loehr, with AFOSR Program Manager Dr . Alan Craig. In 2001, Dr . Thomas Nelson became the in-house project lead on this effort, with...AFOSR management transferred first to Dr . Kent Miller, and most recently to Dr . Gernot Pomrenke. This task was initiated in March 1996, and this report...NUMBER OF PAGES 108 Dr . Thomas R. Nelson 19b. TELEPHONE NUMBER (Include Area Code) (937) 255-1874 x3361 Standard Form 298 (Rev. 8

  1. 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.

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

    NASA Astrophysics Data System (ADS)

    Smagley, Vladimir Anatolievich

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

  3. 1.55 Vertical Cavity Surface Emitting Laser With Dielectric Mirrors

    DTIC Science & Technology

    2007-11-02

    was achieved with a polymer coating and a planarization coating etch-back to expose dielectric top. Then, the etch chemistry was switched to etch...densities respectively, q are the electronic charge, G is the generation rate of carriers and R is the recombination rate of carriers. Python Script...Modification CFDRC has developed python script for data flow management and control of coupled electromagnetic optics/semiconductor physics simulation

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

    DTIC Science & Technology

    2014-05-30

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

  5. Bistable Vertical-Cavity Surface-Emitting Laser. Structures on GaAs and Si Substrates

    DTIC Science & Technology

    1994-06-01

    Lett. 28,734-736 (9 April, 1992). 7. D.L Huffaker, C. Lei, D.G. Deppe, CJ. Pinzone , J.G. Neff, and R.D. Dupuis, "Controlled Spontaneous Emission in...Room Temperature Semiconductor Microcavities," AppL Phys. Lett 60,3203-3205 (29 June, 1992). 8. D.L Huffaker, Z. Huang, C. Lei, D.G. Deppe, CJ. Pinzone ...August, 1992). 9. C. Le, CJ. Pinzone , Z. Huang, D.L. Huffaker, D.G. Deppe, J.G. Neff, and R.D. Dupuis, "Room Temperature Spontaneous Emission in 5pm Long

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Yahata, Hideo

    1999-02-01

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

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

    DOEpatents

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

    2001-01-01

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

  9. Force communication in multicellular tissues addressed by laser nanosurgery.

    PubMed

    Colombelli, Julien; Solon, Jérôme

    2013-04-01

    Cell contractility is a prominent mechanism driving multicellular tissue development and remodeling. Forces originated by the actomyosin cytoskeleton not only act within the cell body but can also propagate many layers away from the contraction source and grant tissues the ability to organize collectively and to achieve robust remodeling through development. Tissue tension is being thoroughly investigated in model organisms and increasing evidence is revealing the major role played by the communication, dynamics and propagation of cell-to-cell physical forces in multicellular remodeling. Recently, pulsed-laser-based surgery has fostered in vivo experimental studies to investigate intracellular and supracellular forces in action. The technique offers a unique method to perturb mechanical equilibrium in a subpopulation of cells or in a single cell, while the overall tissue remains intact. In particular, improved ablation precision with short laser pulses and the combination of this technique with biophysical models now allow an in-depth understanding of the role of cellular mechanics in tissue morphogenesis. We first characterize laser ablation modes available to perform intracellular, cellular, or multi-cellular ablation via the example of the model monolayer tissue of the amnioserosa of Drosophila by relating subnanosecond laser pulse energy to ablation efficiency and the probability of cavitation bubble formation. We then review recent laser nanosurgery experiments that have been performed in cultured cells and that tackle actomyosin mechanics and provide molecular insights into force-sensing mechanisms. We finally review studies showing the central role of laser ablation in revealing the nature and orientation of forces involved in intracellular contractility and force mechanosensing in tissue development, e.g., axis elongation, branching morphogenesis, or tissue invagination. We discuss the perspectives offered by the technique in force-based cell

  10. Processing and packaging of semiconductor lasers and optoelectronic devices; Proceedings of the Meeting, Los Angeles, CA, Jan. 20, 21, 1993

    NASA Astrophysics Data System (ADS)

    Temkin, Henryk

    1993-06-01

    Various papers on processing and packaging of semiconductor laser and optoelectronic devices are presented. Individual topics addressed include: buried heterostructure lasers based on InGaAsP/InP, fabrication processes for GaAs-based high-power diode lasers, fast and reliable processing of high-performance InGaAs 0.98 micron laser diodes, 1.3 micron InGaAsP/InP buried-crescent lasers with narrow spread of threshold currents, Si-based laser subassembly for telecommunications, inexpensive packaging techniques of fiber pigtailed laser diodes, high-performance packaging of gigabit data communication optical modules, applications of diamond made by chemical-vapor deposition for semiconductor laser submounts. Also discussed are: packaging of optical interconnect arrays for optical signal processing and computing, coupling 4 W cw from a diode-pumped Nd:YAG laser through a 5-micron-core single-mode fiber, microoptic and microelectronic infrared packaging of vertical-cavity laser arrays, vertical-cavity surface-emitting laser technology, direct contact-type image sensor unit.

  11. 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.

  12. 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.

  13. Four-Wave Mixing and Optical Phase Conjugation in Vertical Cavity Surface Emitting Devices

    DTIC Science & Technology

    1997-01-01

    1990). Osinski , Marek and Jens Buus. "Linewidth Broadening Factor in Semiconductor Lasers- An Overview," IEEE Journal of Quantum Electronics QE-23(1): 9...above threshold. But as pointed out in the definitive document on the linewidth enhancement factor ( Osinski , 1987), for low carrier densities one can

  14. 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.

  15. High-fidelity local addressing of trapped ions and atoms by composite sequences of laser pulses.

    PubMed

    Ivanov, Svetoslav S; Vitanov, Nikolay V

    2011-04-01

    A vital requirement for a quantum computer is the ability to locally address, with high fidelity, any of its qubits without affecting their neighbors. We propose an addressing method using composite sequences of laser pulses that dramatically reduces the addressing error in a lattice of closely spaced atoms or ions and at the same time significantly enhances the robustness of qubit manipulations. To this end, we design novel (to our knowledge) high-fidelity composite pulses for the most important single-qubit operations. In principle, this method allows one to beat the diffraction limit, for only atoms situated in a small spatial region around the center of the laser beam are excited, well within the laser beam waist.

  16. Occasional Addresses by Edward Teller at Conferences of Laser Interaction and Related Plasma Phenomena (LIRPP)

    NASA Astrophysics Data System (ADS)

    Hora, Heinrich; Miley, George H.

    2016-10-01

    The following sections are included: * Futurology of High Intensity Lasers (LIRPP Vol. 3A) * Lecture in Connection with the Edward Teller Medal Award (LIRPP Vol. 10) * Photo of the First Recipients of the Edward Teller Medal in 1991 * Photos from the Edward Teller Medal Celebration in 1997 * Photo with Participants of the LIRPP No. 12 Conference, 1995 * Photo with Edward Teller Medalists at IFSA01, Kyoto, 2001 * Keynote Address: The Edward Teller Lecture (LIRPP Vol. 11) * Keynote Address: Dr. Edward Teller (LIRPP Vol. 12) * Teller Award Presentation and Keynote Address (LIRPP Vol. 13) * Laudations of Awardees 1991-1995 (LIRPP Vol. 13) * Laudations of Awardees 1999-2003

  17. Multiple wavelength vertical-cavity surface-emitting laser arrays using surface-controlled MOCVD growth rate enhancement and reduction

    SciTech Connect

    Ortiz, G.G.; Hains, C.P.; Luong, S.; Cheng, J.; Hou, H.Q.; Vawter, G.A.

    1997-04-01

    Multiple-wavelength VCSEL and photodetector arrays are useful for wavelength-multiplexed fiberoptic networks, and for optical crosstalk isolation in parallel, free-space interconnects. Multiple wavelength VCSEL arrays have been obtained by varying the growth rate using thermal gradients caused by a backside-patterned substrate, by growth enhancement on a patterned substrate, and by varying the cavity length through anodic oxidation and selective etching of the wafer. We show here for the first time both the enhancement and the reduction of the growth rate of the entire VCSEL structure on a topographically patterned substrate, and demonstrate the controlled variation of the lasing wavelengths of a VCSEL array over an extended spectral range.

  18. Ultra-fine pitch individually addressable visible laser arrays for high speed digital printing applications

    NASA Astrophysics Data System (ADS)

    Kowalski, O. P.; McDougall, S. D.; Qiu, B. C.; Masterton, G. H.; Armstrong, M. L.; Robertson, S.; Caldecott, S.; Marsh, J. H.

    2009-02-01

    An individually addressable visible semiconductor laser diode array with a 20 μm pitch is demonstrated that is highly suited for deployment in next-generation digital print systems. The array, operating at 660 nm, comprises 22 single mode lasers fabricated on a single GaInP/AlGaInP/GaAs substrate. The laser array is flip-chip bonded onto a patterned ceramic submount that enables the individual elements to be driven independently and is integrated into a 26-pin butterfly package. Arrays tested CW exhibit low threshold current (<20 mA per emitter), up to 50 mW output power per channel with a high slope efficiency (0.9 W/A) and a high characteristic temperature of over 100 K.

  19. Some controversies in endovenous laser ablation of varicose veins addressed by optical-thermal mathematical modeling.

    PubMed

    Poluektova, Anna A; Malskat, Wendy S J; van Gemert, Martin J C; Vuylsteke, Marc E; Bruijninckx, Cornelis M A; Neumann, H A Martino; van der Geld, Cees W M

    2014-03-01

    Minimally invasive treatment of varicose veins by endovenous laser ablation (EVLA) becomes more and more popular. However, despite significant research efforts performed during the last years, there is still a lack of agreement regarding EVLA mechanisms and therapeutic strategies. The aim of this article is to address some of these controversies by utilizing optical-thermal mathematical modeling. Our model combines Mordon's light absorption-based optical-thermal model with the thermal consequences of the thin carbonized blood layer on the laser fiber tip that is heated up to temperatures of around 1,000 °C due to the absorption of about 45% of the laser light. Computations were made in MATLAB. Laser wavelengths included were 810, 840, 940, 980, 1,064, 1,320, 1,470, and 1,950 nm. We addressed (a) the effect of direct light absorption by the vein wall on temperature behavior, comparing computations by using normal and zero wall absorption; (b) the prediction of the influence of wavelength on the temperature behavior; (c) the effect of the hot carbonized blood layer surrounding the fiber tip on temperature behavior, comparing wall temperatures from using a hot fiber tip and one kept at room temperature; (d) the effect of blood emptying the vein, simulated by reducing the inside vein diameter from 3 down to 0.8 mm; (e) the contribution of absorbed light energy to the increase in total energy at the inner vein wall in the time period where the highest inner wall temperature was reached; (f) the effect of laser power and pullback velocity on wall temperature of a 2-mm inner diameter vein, at a power/velocity ratio of 30 J/cm at 1,470 nm; (g) a comparison of model outcomes and clinical findings of EVLA procedures at 810 nm, 11 W, and 1.25 mm/s, and 1,470 nm, 6 W, and 1 mm/s, respectively. Interestingly, our model predicts that the dominating mechanism for heating up the vein wall is not direct absorption of the laser light by the vein wall but, rather, heat flow to the

  20. Stimulated Brillouin Scattering (SBS) Suppression and Long Delivery Fibers at the Multikilowatt Level with Chirped Seed Lasers

    DTIC Science & Technology

    2017-03-16

    Mark Harfouche and Amnon Yariv Department of Electrical Engineering , California Institute of Technology, Pasadena, CA John Edgecumbe Nufern...external mirror of a vertical cavity surface - emitting diode laser 0.2 µm in 10 µs can yield a frequency chirp of 5 × 1017 Hz/s at a nearly constant...Burgner for providing the microelectromechanical system (MEMS)-vertical-cavity, surface - emitting lasers (VCSELs). This work was supported by the High

  1. Ultraviolet Polariton Laser

    DTIC Science & Technology

    2015-09-17

    Ultraviolet Polariton Laser Significant progress was achieved in the epitaxy of deep UV AlN/ AlGaN Bragg mirrors and microcavity structures paving...the way to the successful fabrication of vertical cavity emitting laser structures and polariton lasers. For the first time DBRs providing sufficient...high reflectivity for polariton emission were demonstrated. Thanks to a developed strain balanced Al0.85Ga0.15N template, the critical thickness

  2. 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.

  3. AlGaInN laser diode bar and array technology for high power and individually addressable applications

    NASA Astrophysics Data System (ADS)

    Najda, Stephen P.; Perlin, Piotr; Suski, Tadek; Marona, Lucja; Boćkowski, Mike; Leszczyński, Mike; Wisniewski, Przemek; Czernecki, Robert; Kucharski, Robert; Targowski, Grzegorz

    2015-05-01

    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. Low defectivity and high uniformity GaN substrates allows arrays and bars of AlGaInN lasers with up to 20 emitters to be fabricated to obtain optical powers up to 4W at 395nm. AlGaInN laser bars are suitable for optical pumps and novel extended cavity systems for a wide range of applications. An alternative package configuration for AlGaInN laser arrays allows for each individual laser to be addressed individually allowing complex free-space and/or fibre optic system integration with a very small form-factor.

  4. 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.

  5. Characterizing the geometrical tolerances of optimized vertical-cavity thermal emitter stack configurations for the mid-infrared via Monte Carlo testing

    NASA Astrophysics Data System (ADS)

    Pühringer, Gerald; Jakoby, Bernhard

    2017-05-01

    We evaluate a recently devised design of vertical-cavity enhanced resonant thermal emitter (VERTE) regarding stability to fabrication tolerances of PVD layer deposition techniques. Such an emitter achieves narrowband and coherent thermal emission and is composed of an multilayer stack of dielectric layers (silicon and silica) on top of a reflective metal (silver) structure. The silica layer above the metal acts as a vertical cavity enhancing the electromagnetic field between the reflective metal and the dielectric stack forming a Bragg mirror (1-D photonic crystal). In our previous work, we identified several suitable five-layer-stack configurations, which considered several features and limitations of a real-world device, such as temperature dependence of the materials, fabrication constraints or unwanted emission modes. However, the emission characteristics are very sensitive to the geometrical and optical properties of the material. In order to examine this behaviour, a Monte-Carlo algorithm was used to apply a Gauss-distributed error in depth (relative the unperturbed layer thickness) for every individual layer. The robustness of the emission properties against fabrication errors were evaluated and analyzed by significant statistical quantities. As expected, the main issue compromising the emission properties is a deviation of the resonance wavelength in relation to the initial target resonance wavelength of the unperturbed configuration. Interestingly, configurations with larger average layer thicknesses and therefore with larger absolute thickness deviations did not exhibit a larger variance of the emission wavelength. Instead, the variance slightly decreased or remained constant. A similar result was obtained for increasing the number of dielectric layers. In contrast, the peak emissivity (at normal incidence) was significantly influenced by the average layer depth of a configuration. Also, the effect of broadening of the spectral emittance curve due to

  6. High Speed Laser with 100 Ghz Resonance Frequency

    DTIC Science & Technology

    2014-02-28

    practical limit occurs when the detuned master laser encounters the next-order laser modes (i.e. Fabry - Perot modes). Our current DFB slave laser...lasers and vertical- cavity surface-emitting lasers (VCSELs), showing the broad applicability of the technique and that the coupling Q (optical quality...Q-factor, and also increases as the injection power and optical frequency increase. Additionally, we show that lasers with very different cavity

  7. 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.

  8. 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.

  9. Interstellar laser communication: implementability criterion and optimisation conditions for the addressed signal search and sending

    NASA Astrophysics Data System (ADS)

    Mankevich, S. K.; Orlov, E. P.

    2016-10-01

    Using new opportunities offered by the construction of large optical telescopes, a laser radiation receiver with an iodine active quantum filter, high-energy iodine lasers with a diffraction-limited beam divergence and the discovery of exoplanets of the Earth type, including those located relatively not far from the Sun, we analyse the implementability of interstellar laser communication under the conditions, when the central spot of the diffraction pattern at the place of the laser signal reception by means of large optical telescopes can be made smaller than the orbit of the planet, and the signals come to the specified point of the orbit not synchronously with the planet motion because of the error in the determination of the distance between the Sun and the star, around which the planet chosen for communication rotates.

  10. 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.

  11. Optically addressable single-use microfluidic valves by laser printer lithography.

    PubMed

    Garcia-Cordero, Jose L; Kurzbuch, Dirk; Benito-Lopez, Fernando; Diamond, Dermot; Lee, Luke P; Ricco, Antonio J

    2010-10-21

    We report the design, fabrication, and characterization of practical microfluidic valves fabricated using laser printer lithography. These optofluidic valves are opened by directing optical energy from a solid-state laser, with similar power characteristics to those used in CD/DVD drives, to a spot of printed toner where localized heating melts an orifice in the polymer layer in as little as 500 ms, connecting previously isolated fluidic components or compartments. Valve functionality, response time, and laser input energy dependence of orifice size are reported for cyclo-olefin polymer (COP) and polyethylene terephthalate (PET) films. Implementation of these optofluidic valves is demonstrated on pressure-driven and centrifugal microfluidic platforms. In addition, these "one-shot" valves comprise a continuous polymer film that hermetically isolates on-chip fluid volumes within fluidic devices using low-vapor-permeability materials; we confirmed this for a period of one month. The fabrication and integration of optofluidic valves are compatible with a range of polymer microfabrication technologies and should facilitate the development of fully integrated, reconfigurable, and automated lab-on-a-chip systems, particularly when reagents must be stored on chip for extended periods, e.g. for medical diagnostic devices, lab-on-a-chip synthetic systems, or hazardous biochemical analysis platforms.

  12. Techniques and applications for integrating a semiconductor laser on a micromachined die

    NASA Astrophysics Data System (ADS)

    Bouchard, Joseph G., Jr.; Bright, Victor M.; Burns, David M.

    1998-04-01

    This paper describes methods for attaching a vertical cavity surface emitting laser (VCSEL) on to a surface micromachined die. Techniques investigated include silver paste, soldering, wire bonding, and gold pads with integrated resistive heaters. Each technique is evaluated based on reliability, positioning tolerances, and secondary effects. Applications include single chip laser beam scanning.

  13. 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.

  14. Semiconductor Laser Joint Study Program with Rome Laboratory

    DTIC Science & Technology

    1994-09-01

    L.T. Florez . "Low threshold electrically pumped vertical-cavity surface emitting microlasers." Elecron. Lett.. vol. 25 pp. 1213-1124, 1989. 4 N...Macda, L.T. Florez , N.G. Stoffel and T-P. Lee, "Multiple Wavelength Tunable Surface-Emitting Laser Arrays," IEEE J. of Quantmn Elec., vol 27., pp. 1368

  15. Feasibility Analysis and Demonstration of High-Speed Digital Imaging Using Micro-Arrays of Vertical Cavity Surface-Emitting Lasers

    DTIC Science & Technology

    2011-04-01

    quently used PF-200 and PF-300 flashbulbs are shown in Fig. 2. The peak output of 6.0×106 lumens translates to 477465 candelas . Bulbs are flashed at 28 ms...speed imaging, the Lu- minys Corporation 6.5-K Blast high intensity light, produces 25863 candelas , but for a significantly longer duration, de- pending

  16. Tunable vertical-cavity surface-emitting laser with feedback to implement a pulsed neural model. 1. Principles and experimental demonstration.

    PubMed

    Romariz, Alexandre R S; Wagner, Kelvin H

    2007-07-20

    An optoelectronic implementation of a modified FitzHugh-Nagumo neuron model is proposed, analyzed, and experimentally demonstrated. The setup uses linear optics and linear electronics for implementing an optical wavelength-domain nonlinearity. The system attains instability through a bifurcation mechanism present in a class of neuron models, a fact that is shown analytically. The implementation exhibits basic features of neural dynamics including threshold, production of short pulses (or spikes), and refractoriness.

  17. 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.

  18. Sigma7500: an improved DUV laser pattern generator addressing sub-100-nm photomask accuracy and productivity requirements

    NASA Astrophysics Data System (ADS)

    Sjöberg, Henrik; Karlin, Tord; Rosling, Mats; Öström, Thomas; Måhlén, Jonas; Newman, Tom

    2006-05-01

    As photomask pattern complexity continues to increase, it becomes more challenging to control write times of shaped e-beam tools. This raises the related concerns of increased mask costs and extended mask cycle times. A strategy for sub-100 nm technology nodes is to use high-speed DUV laser pattern generators for as many layers as possible, reserving e-beam tools for only the most critical layers. With 248 nm optics and high-NA partially coherent imaging, the Sigma7500 increases the application space available to laser pattern generators. Image profiles are steepened with phase shifting methods, and pattern fidelity is improved with on-line corner enhancement. In the Sigma architecture, mask patterns are imaged with full fidelity and addressability in each writing pass. Because of this, the Sigma7500 provides additional means to improve write time by reducing the number of exposure passes. Platform improvements have resulted in a 2-pass writing accuracy that meets the 4-pass specification of the previous system. Write time is typically under two hours in 2-pass mode, compared to approximately three hours for 4-pass. The Sigma7500 can generally be used for all binary mask layers at the 90 nm technology node, and for about half the layers at 45 nm. The ProcessEqualizer TM function addresses long range CD errors arising from mask process effects. Mask data is sized in real time to compensate for process errors related to local pattern density, and also to correct for static process CD signatures. With a through-the-lens alignment system and both grid matching and pattern matching capabilities, the tool is also suited to 2 nd layer patterning for advanced phase shifting mask (PSM) applications down to 45 nm, with extendibility to 32 nm. Process integration is facilitated by the use of standard FEP-171 chemically amplified resist (CAR).

  19. Lasers Aimed at Aircraft Cockpits: Background and Possible Options to Address the Threat to Aviation Safety and Security

    DTIC Science & Technology

    2005-01-26

    1 Van B. Nakagawara and Ronald W. Montgomery. Laser Pointers : Their Potential Affects on Vision and Aviation Safety. Federal Aviation...powerful at extended viewing distances. Because lasers remain powerful over large distances, a laser pointer can expose pilots to radiation levels above...airliner by aiming a handheld laser pointer into the cockpit is highly unlikely, there is concern that a military laser , such as the Chinese-made ZM-87 laser

  20. Laser-based displays: a review.

    PubMed

    Chellappan, Kishore V; Erden, Erdem; Urey, Hakan

    2010-09-01

    After the invention of lasers, in the past 50 years progress made in laser-based display technology has been very promising, with commercial products awaiting release to the mass market. Compact laser systems, such as edge-emitting diodes, vertical-cavity surface-emitting lasers, and optically pumped semiconductor lasers, are suitable candidates for laser-based displays. Laser speckle is an important concern, as it degrades image quality. Typically, one or multiple speckle reduction techniques are employed in laser displays to reduce speckle contrast. Likewise, laser safety issues need to be carefully evaluated in designing laser displays under different usage scenarios. Laser beam shaping using refractive and diffractive components is an integral part of laser displays, and the requirements depend on the source specifications, modulation technique, and the scanning method being employed in the display. A variety of laser-based displays have been reported, and many products such as pico projectors and laser televisions are commercially available already.

  1. Waveguide grating mirror for laser resonators

    NASA Astrophysics Data System (ADS)

    Rabady, Rabi Ibrahim

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

  2. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Principles of construction of a multiport associative memory from quantum-electronics components

    NASA Astrophysics Data System (ADS)

    Fedorov, V. B.

    1995-11-01

    The principles of construction are proposed, the feasibility of implementation is considered, and the main parameters are estimated of an optoelectronic multiport associative memory which allows M users to carry out simultaneously and independently a parallel associative search for keys and selection of data associated with these keys from a shared memory with the capacity of N words. Addressed writing of keys and data through M ports is also possible. The main base components of such a memory should be arrays of vertical-cavity surface-emitting lasers, optical threshold inverters and photodetectors, and memory arrays based on hybrid memory boards with electrically controlled optical pixels, in combination with spherical free-space optics and electronic control circuits.

  3. 1.56 µm 1 watt single frequency semiconductor disk laser.

    PubMed

    Rantamäki, Antti; Rautiainen, Jussi; Sirbu, Alexei; Mereuta, Alexandru; Kapon, Eli; Okhotnikov, Oleg G

    2013-01-28

    A single frequency wafer-fused semiconductor disk laser at 1.56 µm with 1 watt of output power and a coherence length over 5 km in fiber is demonstrated. The result represents the highest output power reported for a narrow-line semiconductor disk laser operating at this spectral range. The study shows the promising potential of the wafer fusion technique for power scaling of single frequency vertical-cavity lasers emitting in the 1.3-1.6 µm range.

  4. A ten-element array of individually addressable channeled-substrate-planar AlGaAs diode lasers

    NASA Technical Reports Server (NTRS)

    Carlin, D. B.; Goldstein, B.; Bednarz, J. P.; Harvey, M. G.; Dinkel, N. A.

    1987-01-01

    The fabrication of arrays of channeled-substrate-planar (CSP) AlGaAs diode lasers which emit up to 150 mW CW in a single spatial mode and are applicable to mulitchannel optical recording systems is described. The CSP diode lasers are incorporated in ten-array geometry, and each array is 1.95 nm in width and 100 microns in thickness and is cleaved to have a cavity length of 200 microns and coated to produce 90-percent reflectivity on the back facet and 10-percent reflectivity on the front facet. The array is attached to a thermoelectrically cooled submount. The optical output power versus input current characteristics for the array are evaluated, and the lateral far-field intensity profiles for each of the lasers (at 30 mW CW) and CW spectra of the lasers are analyzed.

  5. 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.

  6. 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

  7. Infrared diode laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Civiš, S.; Cihelka, J.; Matulková, I.

    2010-12-01

    Three types of lasers (double-heterostructure 66 K InAsSb/InAsSbP laser diode, room temperature, multi quantum wells with distributed feedback (MQW with DFB) (GaInAsSb/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs) (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) for the strongest absorption line of the v3 + v5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm-1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of v1, v5). Laser sensitive detection (laser absorption together with high resolution Fourier transform infrared technique including direct laser linewidth measurement, infrared photoacoustic detection of neutral molecules (methane, form-aldehyde) is discussed. Additionally, very sensitive laser absorption techniques of such velocity modulation are discussed for case of laser application in laboratory research of molecular ions. Such sensitive techniques (originally developed for lasers) contributed very much in identifying laboratory microwave spectra of a series of anions (C6H-, C4H-, C2H-, CN-) and their discovery in the interstellar space (C6H-, C4H-).

  8. Very large arrays of individually addressable high-power single-mode laser arrays in the 800- to 1000-nm wavelength range obtained by quantum well intermixing techniques

    NASA Astrophysics Data System (ADS)

    Najda, Stephen P.; Bacchin, Gianluca; Qiu, Bocang C.; Smith, Chris J. M.; Vassalli, O.; Toury, Marion; McDougall, Stewart D.; Hamilton, Craig J.; Marsh, John H.

    2005-04-01

    Quantum well intermixing (QWI) of the facet regions of a semiconductor laser can significantly improve the COD of the device giving high kink power and high reliability. A novel epitaxy design incorporating a graded 'V-profile' layer allows for a reduced vertical far-field and simultaneously suppresses higher order modes to give high power operation. Furthermore, the 'V-profile' layer provides a robust design to improve the ridge etch tolerance to give excellent device performance uniformity across an array. Very large arrays of individually addressable lasers (up to 100 elements) are reported with small pitch size (~100 μm), high single mode power (up to 300 mW) and high uniformity.

  9. 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.

  10. 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.

  11. 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)

  12. 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)

  13. 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.

  14. 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.

  15. ANK1 is up-regulated in laser captured microglia in Alzheimer’s brain; the importance of addressing cellular heterogeneity

    PubMed Central

    Sekar, Shobana; Nolz, Jennifer; Delvaux, Elaine; Lunnon, Katie; Mill, Jonathan; Liang, Winnie S.; Coleman, Paul D.

    2017-01-01

    Recent epigenetic association studies have identified a new gene, ANK1, in the pathogenesis of Alzheimer’s disease (AD). Although strong associations were observed, brain homogenates were used to generate the data, introducing complications because of the range of cell types analyzed. In order to address the issue of cellular heterogeneity in homogenate samples we isolated microglial, astrocytes and neurons by laser capture microdissection from CA1 of hippocampus in the same individuals with a clinical and pathological diagnosis of AD and matched control cases. Using this unique RNAseq data set, we show that in the hippocampus, ANK1 is significantly (p<0.0001) up-regulated 4-fold in AD microglia, but not in neurons or astrocytes from the same individuals. These data provide evidence that microglia are the source of ANK1 differential expression previously identified in homogenate samples in AD. PMID:28700589

  16. VCSEL's frequency stabilization of an external cavity diode laser: countermeasures against atmospheric temperature variations

    NASA Astrophysics Data System (ADS)

    Motojima, Mutsuki; Doi, Kohei; Sato, Takashi; Ohkawa, Masashi; Suzuki, Takamasa

    2010-02-01

    We introduced the vertical cavity surface emitting laser (VCSEL) as the laser diode in tour external cavity system. Because VCSELs are now commercially available, and the External cavity diode laser (ECDL) systems using them are expected to improve their frequency stability, we have replaced a Fabry-Perot type laser diode with a VCSEL, and examined its oscillation-frequency stability. Therefore we were able to expect that the VCSELs with our double optical feedback system have good oscillation frequency stability. The obtained VCSEL's oscillation-frequency stability, i.e., the square root of Allan variance σ was 4×10-10, at an averaging time of τ=1 sec.

  17. 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.

  18. Study of a low power dissipation, miniature laser-pumped rubidium frequency standard

    NASA Astrophysics Data System (ADS)

    Liu, Guo-Bin; Zhao, Feng; Gu, Si-Hong

    2009-09-01

    This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping 87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5 × 10-11τ-1/2 (τ < 500 s) frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90 cm3 volume and 10-12τ-1/2 short-term frequency stability.

  19. Oscillation frequency stabilization and narrowing of a laser diode by using an external cavity

    NASA Astrophysics Data System (ADS)

    Iwahori, Minoru; Doi, Kohei; Arai, Hideaki; Sato, Takashi; Ohkawa, Masashi

    2012-02-01

    External cavity diode laser (ECDL) systems are presently experiencing a surge in popularity as laser light-sources, in advanced optical communications- and measurement-applications. Because such systems require that their external reflectors be precisely controlled, to eliminate low frequency fluctuations in optical output, we conducted experiments with a two-cavity version of the ECDL system for a vertical cavity surface emitting laser (VCSEL). This technique brings the added advantages of a narrower linewidth than would be achievable via a single optical feedback. VCSELs are characterized by wider oscillation linewidths than edge emitting types, so the larger effect of double optical feedback system is expected.

  20. 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.

  1. 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.

  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. Differential atomic magnetometry based on a diverging laser beam

    SciTech Connect

    Hodby, E.; Donley, E. A.; Kitching, J.

    2007-07-02

    The authors demonstrate a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over single-channel operation. They also suggest ways in which the current sensitivity of 28 pT/{radical}Hz may be improved further without sacrificing size or simplicity.

  4. A novel diagonal-current injection VCSEL design proposed for nitride lasers

    NASA Astrophysics Data System (ADS)

    Mackowiak, P.; Sarzala, R. P.; Nakwaski, W.

    2001-07-01

    An advanced three-dimensional optical-electrical model has been used for nitride lasers to design a novel vertical-cavity surface-emitting laser (VCSEL) configuration with a diagonal-current injection (DCI) mechanism. The design has been optimized for the lowest room-temperature (RT) lasing threshold which has been found to be similar to RT thresholds of advanced arsenide and phosphide VCSELs. The DCI nitride VCSEL demonstrates very promising anticipated RT threshold characteristics. Its optical structure is very selective: the fundamental mode exhibits distinctly the lowest threshold. In addition, the lasing threshold has been found to be exponentially proportional to the barrier width.

  5. Cavity soliton laser based on a VCSEL with saturable absorber

    NASA Astrophysics Data System (ADS)

    Tissoni, Giovanna; Aghdami, Keivan M.; Prati, Franco; Brambilla, Massimo; Lugiato, Luigi A.

    In this Chapter we intend to make a review on our work on cavity solitons in semiconductor lasers with saturable absorbers, with a special attention to the most recent results.We study theoretically a broad-area vertical cavity surface emitting laser (VCSEL) with a saturable absorber, and show numerically the existence of cavity solitons in the system: they exist as solitary structures superposed on a background with zero intensity. Therefore, this system can work as a cavity soliton laser, ensuring maximum contrast and compactness of the device, in comparison with other systems supporting cavity solitons. In particular, in absence of a holding beam, these solitons do not rely on a proper phase of the addressing pulses to be either created or deleted.We also show that the properties of the system are deeply influenced by the radiative recombination of carriers. Taking into account this process, the existence of solitons is shown numerically for a choice of parameters suitable to describe real devices, where the same material is used for the active and the passive parts. Furthermore, we compare three different switching techniques for the control of cavity solitons in a VCSEL based cavity soliton laser, one incoherent and the other two semicoherent with different injection frequencies. We show that the switching dynamics and energies can be very different depending on the type of injection. Finally, we show that in a cavity soliton laser based on a VCSEL with a saturable absorber the solitons can spontaneously move if the ratio of the carrier lifetimes in the amplifier and in the absorber takes appropriate values. The direction of the motion is arbitrary, while its velocity is determined by the parameters of the system. In devices with a finite cross section the CS describes different trajectories depending on the shape of the boundary of the pumped region. For a circular pump the CS moves on circular trajectories along the boundary. This dynamical regime can be

  6. 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

  7. 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.

  8. Convocation address.

    PubMed

    Kakodkar, A

    1999-07-01

    This convocation addressed by Dr. Anil Kakodkar focuses on the challenges faced by graduating students. In his speech, he emphasized the high level of excellence achieved by the industrial sector; however, he noted that there has been a loss of initiative in maximizing value addition, which was worsened by an increasing population pressure. In facing a stiff competition in the external and domestic markets, it is imperative to maximize value addition within the country in a competitive manner and capture the highest possible market share. To achieve this, high-quality human resources are central. Likewise, family planning programs should become more effective and direct available resources toward national advantage. To boost the domestic market, he suggests the need to search for strengths to achieve leadership position in those areas. First, an insight into the relationship between the lifestyles and the needs of our people and the natural resource endowment must be gained. Second, remodeling of the education system must be undertaken to prepare the people for adding the necessary innovative content in our value addition activities. Lastly, Dr. Kakodkar emphasizes the significance of developing a strong bond between parents and children to provide a sound foundation and allow the education system to grow upon it.

  9. 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

  10. 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

  11. Convocation address.

    PubMed

    Ghatowar, P S

    1993-07-01

    The Union Deputy Minister of Health and Family Welfare in India addressed the 35th convocation of the International Institute for Population Sciences in Bombay in 1993. Officials in developing countries have been concerned about population growth for more than 30 years and have instituted policies to reduce population growth. In the 1960s, population growth in developing countries was around 2.5%, but today it is about 2%. Despite this decline, the world will have 1 billion more individuals by the year 2001. 95% of these new people will be born in developing countries. India's population size is so great that India does not have the time to wait for development to reduce population growth. Population needs to be viewed as an integrated part of overall development, since it is linked to poverty, illiteracy, environmental damage, gender issues, and reproductive health. Despite a large population size, India has made some important advancements in health and family planning. For example, India has reduced population growth (to 2.14% annually between 1981-1991), infant mortality, and its birth rate. It has increased the contraceptive use rate and life expectancy. Its southern states have been more successful at achieving demographic goals than have the northern states. India needs to implement efforts to improve living conditions, to change attitudes and perceptions about small families and contraception, and to promote family planning acceptance earlier among young couples. Improvement of living conditions is especially important in India, since almost 33% of the people live in poverty. India needs to invest in nutrition, health, and education. The mass media and nongovernmental organizations need to create population awareness and demand for family planning services. Improvement in women's status accelerates fertility decline, as has happened in Kerala State. The government needs to facilitate generation of jobs. Community participation is needed for India to achieve

  12. 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

  13. 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

  14. Laser Doppler velocimetry using a modified computer mouse

    NASA Astrophysics Data System (ADS)

    Zaron, Edward D.

    2016-10-01

    A computer mouse has been modified for use as a low-cost laser Doppler interferometer and used to measure the two-component fluid velocity of a flowing soap film. The mouse sensor contains two vertical cavity surface emitting lasers, photodiodes, and signal processing hardware integrated into a single package, approximately 1 cm2 in size, and interfaces to a host computer via a standard USB port. Using the principle of self-mixing interferometry, whereby laser light re-enters the laser cavity after being scattered from a moving target, the Doppler shift and velocity of scatterers dispersed in the flow are measured. Observations of the boundary layer in a turbulent soap film channel flow demonstrate the capabilities of the sensor.

  15. Solid state microcavity dye lasers fabricated by nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Nilsson, D.; Nielsen, T.; Kristensen, A.

    2004-11-01

    We present a solid state polymer microcavity dye laser, fabricated by thermal nanoimprint lithography (NIL) in a dye-doped thermoplast. The thermoplast poly-methylmethacrylate (PMMA) is used due to its high transparency in the visible range and its robustness to laser radiation. The laser dye is Rhodamine 6G ClO4. This dye is shown to withstand temperatures up to 240 °C without bleaching, which makes it compatible with the thermal nanoimprint lithography process. The 1.55 μm thick dye-doped PMMA devices are fabricated on a SiO2 substrate, yielding planar waveguiding in the dye-doped PMMA with two propagating TE-TM modes. The laser cavity has the lateral shape of a trapezoid, supporting lasing modes by reflection on the vertical cavity walls. The solid polymer dye lasers emit laterally through one of the vertical cavity walls, when pumped optically through the top surface by means of a frequency doubled, pulsed Nd:YAG laser. Lasing in the wavelength region from 560 to 570 nm is observed from a laser with a side-length of 50 μm. In this proof of concept, the lasers are multimode with a mode wavelength separation of approximately 1.6 nm, as determined by the waveguide propagation constant(s) and cavity dimensions. The stamps used in this work were fabricated by UV-lithography, limiting the lateral dimensional control of the devices. The resolution of NIL is ultimately limited by the quality of the stamps. Using electron beam lithography for stamp fabrication, the NIL process presented here offers the possibility for adding mode-selecting elements, e.g., diffractive- or sub-wavelength optical elements.

  16. 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.

  17. Passively Q-switched VCSEL-pumped Nd:YAG laser with 47 mJ pulse energy

    NASA Astrophysics Data System (ADS)

    Van Leeuwen, Robert; Xu, Bing; Wang, Qing; Xu, Guoyang; Zhou, Delai; Kovsh, Alexey; Seurin, Jean-Francois; Ghosh, Chuni

    2017-02-01

    A compact passively Q-switched Nd:YAG laser was end-pumped by a water-cooled 808 nm vertical-cavity surface-emitting laser (VCSEL) pump module comprising four high power, high brightness VCSEL chips with a combined 10 mm diameter circular emitting area and 2.3 kW total peak power, resulting in 47 mJ laser pulse energy at 1064 nm with 16% optical efficiency at 15 Hz repetition frequency. A laser package comprising an air-cooled 1.6 kW VCSEL pump module produced 37 mJ laser pulse energy, while more than 13 mJ laser pulse energy was demonstrated in a bench-top experiment with a very compact laser set-up using a single 5 mm x 5 mm VCSEL chip.

  18. [Lasers].

    PubMed

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  19. Lasers.

    PubMed

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  20. 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.

  1. Oxygen measurement by multimode diode lasers employing gas correlation spectroscopy.

    PubMed

    Lou, Xiutao; Somesfalean, Gabriel; Chen, Bin; Zhang, Zhiguo

    2009-02-10

    Multimode diode laser (MDL)-based correlation spectroscopy (COSPEC) was used to measure oxygen in ambient air, thereby employing a diode laser (DL) having an emission spectrum that overlaps the oxygen absorption lines of the A band. A sensitivity of 700 ppm m was achieved with good accuracy (2%) and linearity (R(2)=0.999). For comparison, measurements of ambient oxygen were also performed by tunable DL absorption spectroscopy (TDLAS) technique employing a vertical cavity surface emitting laser. We demonstrate that, despite slightly degraded sensitivity, the MDL-based COSPEC-based oxygen sensor has the advantages of high stability, low cost, ease-of-use, and relaxed requirements in component selection and instrument buildup compared with the TDLAS-based instrument.

  2. Design and analysis of an electrically pumped microcavity organic laser device

    NASA Astrophysics Data System (ADS)

    Shayesteh, Mohammad Reza

    2017-02-01

    We propose a new structure of organic vertical-cavity surface-emitting laser to be pumped electrically. The microcavity structure consists of an organic light emitting diode with field-effect electron transport set in between multilayer dielectric mirrors. The threshold behavior and the dynamics of the proposed OVCSEL are analyzed numerically. We show that the device can reach the lasing threshold under electrical pump at a current density of 24 A/cm2. Also, the dynamic behavior of the device under pulsed excitation is investigated. The results show that pulse excitation reduces field quenching and triplet exciton losses; hence, output photon density can be increased. [Figure not available: see fulltext.

  3. Thermal analysis of etched-well surface-emitting diode lasers

    SciTech Connect

    Nakwaski, Wlodzimierz; Osinski, Marek )

    1991-11-01

    A new self-consistent thermal-electrical model of etched-well GaAs/AlGaAs vertical-cavity surface-emitting lasers is developed. The model features a realistic distribution of heat sources and two-dimensional current- and heat-flux spreading. It is shown that the P-AlGaAs layer represents a major source of Joule heating that may easily exceed the active-region heating. A moderate increase of the P-AlGaAs layer doping is shown to be very effective in reducing the excessive heating. 8 refs.

  4. Application of nanophotonics to the next generation of surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Ledentsov, Nikolay N.; Ledentsov, Nikolay; Agustin, Mikel; Kropp, Joerg-R.; Shchukin, Vitaly A.

    2017-08-01

    Novel trends and concepts in the design and fabrication of vertical cavity surface-emitting lasers (VCSELs) and their integration in optical networks and implementation in integrated photonics applications are discussed. To serve these goals and match the growing bandwidth demands, significant changes are to be implemented in the device design. New lateral leakage-mediated single-mode VCSELs, including both devices confined by oxide layers and those confined by alloy-intermixed regions, are likely to be good candidates for light sources for the data networks of the future. An overview of the records in VCSEL transmission distances and transmission speeds is discussed in this context.

  5. 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.

  6. 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.

  7. Wave pattern and weak localization of chaotic versus scarred modes in stadium-shaped surface-emitting lasers.

    PubMed

    Yu, Y T; Tuan, P H; Chiang, P Y; Liang, H C; Huang, K F; Chen, Y F

    2011-11-01

    We explore the lasing mode selection between the chaotic and scarred modes in stadium-shaped vertical-cavity surface-emitting lasers (VCSELs). Experimental results reveal that the spatial gain distribution in the active layer of a VCSEL can be modified via the aperture size to favor the generation of either the chaotic or the scarred modes. Experimentally obtained chaotic and scarred modes are further employed to perform statistical analysis of wave function intensities for making a comparison with predictions based on the nonlinear σ model. We verify that the scarring effect can be quantitatively relevant to the weak-localization correction in the intensity probability distribution.

  8. 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.

  9. 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.

  10. Laser Science and Applications

    NASA Astrophysics Data System (ADS)

    El-Nadi, Lotfia M.; Mansour, Mohy S.

    2010-04-01

    Attosecond high harmonic pulses: generation and characterization / C. H. Nam and K. T. Kim -- High power lasers and interactions / C. Chatwin and R. Young -- Laser accelerators / L. M. El-Nadi ... [et al.] -- Energy levels, oscillator strengths, lifetimes, and gain distributions of S VII, CI VIII, and Ar IX / Wessameldin. S. Abdelaziz and Th. M. El-Sherbini -- The gain distribution according to theoretical level structure and decay dynamics of W[symbol] / H. M. Hamed ... [et al.] -- Raman spectroscopy and low temperature photoluminescence ZnSe[symbol]Te[symbol] ternary alloys / A. Salah ... [et al.] -- Automated polarization-discrimination technique to minimize lidar detected skylight background noise, part I / Y. Y. Hassebo, K. Elsayed and S. Ahmed -- Laser interferometric measurements of the physical properties for He, Ne gases and their mixture / N. M. Abdel-Moniem ... [et al.] -- Analytical studies of laser beam propagation through the atmosphere / M. I. El-Saftawy, A. M. Abd El-Hamed and N. Sh. Kalifa -- Laser techniques in conservation of artworks: problems and breakthroughs / R. Salimbeni and S. Siano -- Technology-aided heritage conservation laser cleaning for buildings / M. S. Nada -- Technology significance in conservation of the built heritage 3D visualization impact / M. S. Nada -- Simulation of optical resonators for Vertical-Cavity Surface-Emitting Lasers (VCSEL) / M. S. Mansour ... [et al.] -- Optical design alternatives: a survey study / A. A. K. Ismail, I. A. S. Ismail and S. H. Ahmed -- Materials for digital optical design; a survey study / A. A. K. Ismail, I. A. S. Ismail and S. H. Ahmed -- Proposed design for optical digital circuits / A. A. K. Ismail, I. A. S. Ismail and S. H. Ahmed -- Photo-induced effect on bacterial cells / M. H. El Batanouny ... [et al.] -- Laser and non-coherent light effect on peripheral blood normal and acute lymphoblastic leukemic cells by using different types of photosensitizers / M. H. El Batanouny ... [et al

  11. 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

    2015-11-02

    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.

  12. 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.

  13. 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%.

  14. High brightness diode lasers controlled by volume Bragg gratings

    NASA Astrophysics Data System (ADS)

    Glebov, Leonid

    2017-02-01

    Volume Bragg gratings (VBGs) recorded in photo-thermo-refractive (PTR) glass are holographic optical elements that are effective spectral and angular filters withstanding high power laser radiation. Reflecting VBGs are narrow-band spectral filters while transmitting VBGs are narrow-band angular filters. The use of these optical elements in external resonators of semiconductor lasers enables extremely resonant feedback that provides dramatic spectral and angular narrowing of laser diodes radiation without significant power and efficiency penalty. Spectral narrowing of laser diodes by reflecting VBGs demonstrated in wide spectral region from near UV to 3 μm. Commercially available VBGs have spectral width ranged from few nanometers to few tens of picometers. Efficient spectral locking was demonstrated for edge emitters (single diodes, bars, modules, and stacks), vertical cavity surface emitting lasers (VCSELs), grating coupled surface emitting lasers (GCSELs), and interband cascade lasers (ICLs). The use of multiplexed VBGs provides multiwavelength emission from a single emitter. Spectrally locked semiconductor lasers demonstrated CW power from milliwatts to a kilowatt. Angular narrowing by transmitting VBGs enables single transverse mode emission from wide aperture diode lasers having resonators with great Fresnel numbers. This feature provides close to diffraction limit divergence along a slow axis of wide stripe edge emitters. Radiation exchange between lasers by means of spatially profiled or multiplexed VBGs enables coherent combining of diode lasers. Sequence of VBGs or multiplexed VBGs enable spectral combining of spectrally narrowed diode lasers or laser modules. Thus the use of VBGs for diode lasers beam control provides dramatic increase of brightness.

  15. Semiconductor surface emitting lasers for photon pairs generation

    NASA Astrophysics Data System (ADS)

    Vanbever, Luc R.; Karpov, Evgueni; Panajotov, Krassimir

    2017-10-01

    We study the feasibility of generating photon pairs in a resonant Vertical-Cavity Surface-Emitting Laser (VCSEL) as a result of a third-order non-linear, four wave mixing interaction. We focus on degenerate four wave mixing in the spontaneous regime where two pump photons are annihilated to create a pair of signal and idler photons. Using the methods of quantum optics, we calculate the two-photon production rate, the spectrum of the generated photons, and the signal-idler cross-correlations. We highlight how the dispersion of the medium in the VCSEL cavity (a regular GaAs configuration) significantly diminishes the two-photon production rate. Based on our results, we enumerate the characteristics of a VCSEL that would be suitable for photon pair generation.

  16. 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.

  17. Frequency tuning of polarization oscillations: Toward high-speed spin-lasers

    SciTech Connect

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

    2016-01-25

    Spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) offer a high potential to overcome several limitations of conventional purely charged-based laser devices. Presumably, the highest potential of spin-VCSELs lies in their ultrafast spin and polarization dynamics, which can be significantly faster than the intensity dynamics in conventional devices. Here, we experimentally demonstrate polarization oscillations in spin-VCSELs with frequencies up to 44 GHz. The results show that the oscillation frequency mainly depends on the cavity birefringence, which can be tuned by applying mechanical strain to the VCSEL structure. A tuning range of about 34 GHz is demonstrated. By measuring the polarization oscillation frequency and the birefringence governed mode splitting as a function of the applied strain simultaneously, we are able to investigate the correlation between birefringence and polarization oscillations in detail. The experimental findings are compared to numerical calculations based on the spin-flip model.

  18. Optical Addressing And Clocking Of RAM's

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Proposed random-access-memory (RAM) addressing system, in which memory linked optically to read/write logic circuits, greatly increases computer operating speed. System - comprises addressing circuits including numerous lasers as signal sources, numerous optical gates including optical detectors associated with memory cells, and holographic element to direct light signals to desired memory-cell locations - applied to high-capacity digital systems, supercomputers, and complex microcircuits.

  19. External-cavity solid-state organic lasers: Design rules and application perspectives (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Chénais, Sébastien; Gallinelli, Thomas; Mhibik, Oussama; Blanchard, Cédric; Forget, Sébastien

    2016-09-01

    Among various laser architectures currently used to make lasers out of organic materials (distributed feedback lasers or organic vertical cavity surface-emitting lasers, ....), vertical EXTERNAL cavities have several distinctive features that enable making lasers with a high brightness, resulting from a combination of high efficiency and good beam quality, and also offer a superior flexibility to monitor the laser spectrum. In this talk I will highlight a few recent results on external-cavity organic lasers and reveal their potential through the example of a single mode organic laser device with an ultranarrow linewidth (< pm) corresponding to coherence lengths of several meters under diode pumping (typically 2-3 orders of magnitude longer than the state-of-the-art). From the material point of view, I will also show how ink-jet printing can be successfully used in vertical external-cavity organic lasers to make thick and optical-quality films that have the potential to be easily produced with a high throughput.

  20. Reach Address Database (RAD)

    EPA Pesticide Factsheets

    The Reach Address Database (RAD) stores the reach address of each Water Program feature that has been linked to the underlying surface water features (streams, lakes, etc) in the National Hydrology Database (NHD). (A reach is the portion of a stream between two points of confluence. A confluence is the location where two or more streams flow together.)

  1. Addressing Ozone Layer Depletion

    EPA Pesticide Factsheets

    Access information on EPA's efforts to address ozone layer depletion through regulations, collaborations with stakeholders, international treaties, partnerships with the private sector, and enforcement actions under Title VI of the Clean Air Act.

  2. Thermal annealing effects on AlGaAsSb/GaSb laser structure: Bandgap energy blueshift and thermal conductivity enhancement

    NASA Astrophysics Data System (ADS)

    Ilahi, S.; Yacoubi, N.; Genty, F.

    2017-07-01

    In this paper, we have investigated the effects of thermal annealing on optical properties and thermal conductivity of AlGaAsSb/GaSb laser structure using photo-thermal deflection spectroscopy PDS. In fact, optical absorption spectrum and thermal conductivity have been determined by comparison between experimental and theoretical phase of PDS signal. We have found that band gap energy is blue shifted of 70 meV for the as grown to the sample annealed for 1 h. Indeed, the highest thermal conductivity is found around of 11 W/m.K for AlGaAsSb/GaSb annealed for 1 h, which presents a promising result for vertical-cavity surface-emitting lasers (VCSELs).

  3. Low-cost bidirectional hybrid fiber-visible laser light communication system based on carrier-less amplitude phase modulation

    NASA Astrophysics Data System (ADS)

    He, Jing; Dong, Huan; Deng, Rui; Chen, Lin

    2016-08-01

    We propose a bidirectional hybrid fiber-visible laser light communication (fiber-VLC) system. To reduce the cost of the system, the cheap and easy integration red vertical cavity surface emitting lasers, low-complexity carrier-less amplitude phase modulation format, and wavelength reuse technique are utilized. Meanwhile, the automatic gain control amplifier voltage and bias voltage for downlink and uplink are optimized. The simulation results show that, by using the proposed system, the bit error rate of 3.8×10-3 can be achieved for 16-Gbps CAP signal after 30-km standard single mode fiber and 8-m VLC bidirectional transmission. Therefore, it indicates the feasibility and potential of proposed system for indoor access network.

  4. 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.

  5. 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.

  6. 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.

  7. 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…

  8. 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…

  9. Addressivity in Cogenerative Dialogues

    ERIC Educational Resources Information Center

    Hsu, Pei-Ling

    2014-01-01

    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…

  10. 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…

  11. Invitational Addresses, 1965.

    ERIC Educational Resources Information Center

    Gates, Arthur I.; And Others

    The full texts of invitational addresses given at the 1965 International Reading Association (IRA) Convention in Detroit, Michigan, by six recipients of IRA citation awards are presented. Gates suggests steps IRA should take to revive and redirect reading research. McCallister discusses the implications of the changing and expanding vocabulary of…

  12. 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…

  13. 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.

  14. 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.

  15. Semiconductor lasers driven by self-sustained chaotic electronic oscillators and applications to optical chaos cryptography.

    PubMed

    Kingni, Sifeu Takougang; Mbé, Jimmi Hervé Talla; Woafo, Paul

    2012-09-01

    In this work, we numerically study the dynamics of vertical cavity surface emitting laser (VCSEL) firstly when it is driven by Chua's oscillator, secondly in case where it is driven by a broad frequency spectral bandwidth chaotic oscillator developed by Nana et al. [Commun. Nonlinear Sci. Numer. Simul. 14, 2266 (2009)]. We demonstrated that the VCSEL generated robust chaotic dynamics compared to the ones found in VCSEL subject to a sinusoidally modulated current and therefore it is more suitable for chaos encryption techniques. The synchronization characteristics and the communication performances of unidirectional coupled VCSEL driven by the broad frequency spectral bandwidth chaotic oscillators are investigated numerically. The results show that high-quality synchronization and transmission of messages can be realized for suitable system parameters. Chaos shift keying method is successfully applied to encrypt a message at a high bitrate.

  16. Content Addressable Memory Project

    DTIC Science & Technology

    1990-11-01

    The Content Addressable M1-emory Project consists of the development of several experimental software systems on an AMT Distributed Array Processor...searching (database) compiler algorithms memory management other systems software) Linear C is an unlovely hybrid language which imports the CAM...memory from AMT’s operating system for the DAP; how- ever, other than this limitation, the memory management routines work exactly as their C counterparts

  17. 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.

  18. 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.

  19. Ultralow-threshold electrically pumped quantum-dot photonic-crystal nanocavity laser

    NASA Astrophysics Data System (ADS)

    Ellis, Bryan; Mayer, Marie A.; Shambat, Gary; Sarmiento, Tomas; Harris, James; Haller, Eugene E.; Vučković, Jelena

    2011-05-01

    Efficient, low-threshold and compact semiconductor laser sources are under investigation for many applications in high-speed communications, information processing and optical interconnects. The best edge-emitting and vertical-cavity surface-emitting lasers have thresholds on the order of 100 µA (refs 1,2), but dissipate too much power to be practical for many applications, particularly optical interconnects. Optically pumped photonic-crystal nanocavity lasers represent the state of the art in low-threshold lasers; however, to be practical, techniques to electrically pump these structures must be developed. Here, we demonstrate a quantum-dot photonic-crystal nanocavity laser in gallium arsenide pumped by a lateral p-i-n junction formed by ion implantation. Continuous-wave lasing is observed at temperatures up to 150 K. Thresholds of only 181 nA at 50 K and 287 nA at 150 K are observed--the lowest thresholds ever observed in any type of electrically pumped laser.

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

    SciTech Connect

    Virte, Martin

    2016-05-15

    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.

  1. 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.

  2. 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

  3. Bioreactors addressing diabetes mellitus.

    PubMed

    Minteer, Danielle M; Gerlach, Jorg C; Marra, Kacey G

    2014-11-01

    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. © 2014 Diabetes Technology Society.

  4. Addressing Environmental Health Inequalities.

    PubMed

    Gouveia, Nelson

    2016-08-27

    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.

  5. Addressing Environmental Health Inequalities

    PubMed Central

    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

  6. The application of cost-effective lasers in coherent UDWDM-OFDM-PON aided by effective phase noise suppression methods.

    PubMed

    Liu, Yue; Yang, Chuanchuan; Yang, Feng; Li, Hongbin

    2014-03-24

    Digital coherent passive optical network (PON), especially the coherent orthogonal frequency division multiplexing PON (OFDM-PON), is a strong candidate for the 2nd-stage-next-generation PON (NG-PON2). As is known, OFDM is very sensitive to the laser phase noise which severely limits the application of the cost-effective distributed feedback (DFB) lasers and more energy-efficient vertical cavity surface emitting lasers (VCSEL) in the coherent OFDM-PON. The current long-reach coherent OFDM-PON experiments always choose the expensive external cavity laser (ECL) as the optical source for its narrow linewidth (usually<100 KHz). To solve this problem, we introduce the orthogonal basis expansion based (OBE) phase noise suppression method to the coherent OFDM-PON and study the possibility of the application of the DFB lasers and VCSEL in coherent OFDM-PON. A typical long-reach coherent ultra dense wavelength division multiplexing (UDWDM) OFDM-PON has been set up. The numerical results prove that the OBE method can stand severe phase noise of the lasers in this architecture and the DFB lasers as well as VCSEL can be used in coherent OFDM-PON. In this paper, we have also analyzed the performance of the RF-pilot-aided (RFP) phase noise suppression method in coherent OFDM-PON.

  7. 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.

  8. Watt-class high-power, high-beam-quality photonic-crystal lasers

    NASA Astrophysics Data System (ADS)

    Hirose, Kazuyoshi; Liang, Yong; Kurosaka, Yoshitaka; Watanabe, Akiyoshi; Sugiyama, Takahiro; Noda, Susumu

    2014-05-01

    The applications of surface-emitting lasers, in particular vertical-cavity surface-emitting lasers (VCSELs), are currently being extended to various low-power fields including communications and interconnections. However, the fundamental difficulties in increasing their output power by more than several milliwatts while maintaining single-mode operation prevent their application in high-power fields such as material processing, laser medicine and nonlinear optics, despite their advantageous properties of circular beams, the absence of catastrophic optical damage, and their suitability for two-dimensional integration. Here, we demonstrate watt-class high-power, single-mode operation by a two-dimensional photonic-crystal surface-emitting laser under room-temperature, continuous-wave conditions. The two-dimensional band-edge resonant effect of a photonic crystal formed by metal-organic chemical vapour deposition enables a 1,000 times broader coherent-oscillation area, which results in a high beam quality of M2 <= 1.1, narrowing the focus spot by two orders of magnitude compared to VCSELs. Our demonstration promises to realize innovative high-power applications for surface-emitting lasers.

  9. Frequency stabilization of an external cavity diode laser: countermeasures against atmospheric temperature variations

    NASA Astrophysics Data System (ADS)

    Minabe, Yuta; Doi, Kohei; Sato, Takashi; Maruyama, Takeo; Ohkawa, Masashi; Tsubokawa, Tsuneya

    2008-02-01

    External cavity diode lasers (ECDL) are presently experiencing a surge in popularity, as laser light-sources for advanced optical measurement systems. While these devices normally require external optical-output controls, we simplified the setup, a bit, by adding a second external cavity. This technique boasts the added advantage of having a narrower oscillation-linewidth than would be achievable, using a single optical feedback. Because drive-current and atmospheric temperature directly impact the ECDL systems' oscillation frequency, during frequency stability checks, it was necessary, in this instance, to construct a slightly smaller ECDL system, which we mounted on a Super-Invar board, to minimize the influence of thermal expansion. Taking these and other aggressive and timely measures to prevent atmospheric temperature-related changes allowed us to achieve an improvement in oscillation-frequency stability, i.e., to obtain the square root of Allan variance σ =2×10 -10, at averaging time τ =10 -1. We introduced a vertical-cavity surface-emitting laser (VCSEL) to the setup, for the simple reason that its frequency is far less susceptible to changes in temperature, than other lasers of its type. And, because VCSELs are widely available, and the ECDL systems that use them improve frequency stability, we replaced the Fabry-Perot semiconductor laser with a VCSEL.

  10. A study of distributed dielectric bragg reflectors for vertically emitting lasers of the near-IR range

    NASA Astrophysics Data System (ADS)

    Blokhin, S. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Blokhin, A. A.; Vasil'ev, A. P.; Guseva, Yu. A.; Kulagina, M. M.; Karpovsky, I. O.; Zadiranov, Yu. M.; Troshkov, S. I.; Prasolov, N. D.; Brunkov, P. N.; Levitsky, V. S.; Lisak, V.; Maleev, N. A.; Ustinov, V. M.

    2016-10-01

    Studies aimed at optimization of the design of a dielectric distributed Bragg reflector (DBR) produced by the reactive magnetron sputtering method for applications in near-IR vertical-cavity surface-emitting lasers with intracavity contacts (ICC-VCSELs) are carried out. It is shown that the reflectivity of the dielectric DBRs based on SiO2/TiO2 decreases due to the polycrystalline structure of the TiO2 layers, which causes diffusive scattering of light. In contrast, amorphous Ta2O5 layers is characterized by a low surface roughness and low fluctuation in the refractive index. Single-mode ICC-VCSELs in the 980-nm spectral range with dielectric DBR based on SiO2/Ta2O5 with a threshold current less than 0.27 mA, electric resistance of less than 200 Ω, and differential efficiency of more than 0.8 W/A are demonstrated.

  11. Analysis of Effect of Singlet-Triplet Annihilation in a Low-Threshold Optically Pumped Organic Semiconductor Laser

    NASA Astrophysics Data System (ADS)

    Shayesteh, Mohammad Reza

    2017-10-01

    We investigate the impact of optical excitation in a low-threshold organic semiconductor vertical-cavity surface-emitting laser (OVCSEL) to achieve lasing. We study the threshold behavior and the dynamics of the optimized OVCSEL structure when pumped by both picosecond and nanosecond pulses. The boundary between pulsed and continuous wave lasing is analyzed for the study of annihilation quenching losses in the proposed OVCSEL. Results from numerical simulation show that, for the picosecond pulses excitation case, the singlet-triplet annihilation is not effective and a lasing threshold of about 0.75 μJ cm-2 can be obtained. We show that for the nanosecond pulses pumping case, triplet excitons largely quench singlet excitons and lasing is sustained for a short time following turn-on of the pump.

  12. [Keynote address: Climate change

    SciTech Connect

    Forrister, D.

    1994-12-31

    Broadly speaking, the climate issue is moving from talk to action both in the United States and internationally. While few nations have adopted strict controls or stiff new taxes, a number of them are developing action plans that are making clear their intention to ramp up activity between now and the year 2000... and beyond. There are sensible, economically efficient strategies to be undertaken in the near term that offer the possibility, in many countries, to avoid more draconian measures. These strategies are by-and-large the same measures that the National Academy of Sciences recommended in a 1991 report called, Policy Implications of Greenhouse Warming. The author thinks the Academy`s most important policy contribution was how it recommended the nations act in the face of uncertain science and high risks--that cost effective measures are adopted as cheap insurance... just as nations insure against other high risk, low certainty possibilities, like catastrophic health insurance, auto insurance, and fire insurance. This insurance theme is still right. First, the author addresses how the international climate change negotiations are beginning to produce insurance measures. Next, the author will discuss some of the key issues to watch in those negotiations that relate to longer-term insurance. And finally, the author will report on progress in the United States on the climate insurance plan--The President`s Climate Action Plan.

  13. Laser cosmology

    NASA Astrophysics Data System (ADS)

    Chen, P.

    2014-05-01

    Recent years have witnessed tremendous progress in our understanding of the cosmos, which in turn points to even deeper questions to be further addressed. Concurrently the laser technology has undergone dramatic revolutions, providing exciting opportunity for science applications. History has shown that the symbiosis between direct observations and laboratory investigation is instrumental in the progress of astrophysics. We believe that this remains true in cosmology. Current frontier phenomena related to particle astrophysics and cosmology typically involve one or more of the following conditions: (1) extremely high energy events;(2) very high density, high temperature processes; (3) super strong field environments. Laboratory experiments using high intensity lasers can calibrate astrophysical observations, investigate underlying dynamics of astrophysical phenomena, and probe fundamental physics in extreme limits. In this article we give an overview of the exciting prospect of laser cosmology. In particular, we showcase its unique capability of investigating frontier cosmology issues such as cosmic accelerator and quantum gravity.

  14. Ultrahigh-speed Si-integrated on-chip laser with tailored dynamic characteristics

    NASA Astrophysics Data System (ADS)

    Park, Gyeong Cheol; Xue, Weiqi; Piels, Molly; Zibar, Darko; Mørk, Jesper; Semenova, Elizaveta; Chung, Il-Sug

    2016-12-01

    For on-chip interconnects, an ideal light source should have an ultralow energy consumption per bandwidth (operating en-ergy) as well as sufficient output power for error-free detection. Nanocavity lasers have been considered the most ideal for smaller operating energy. However, they have a challenge in obtaining a sufficient output power. Here, as an alternative, we propose an ultrahigh-speed microcavity laser structure, based on a vertical cavity with a high-contrast grating (HCG) mirror for transverse magnetic (TM) polarisation. By using the TM HCG, a very small mode volume and an un-pumped compact optical feedback structure can be realised, which together tailor the frequency response function for achieving a very high speed at low injection currents. Furthermore, light can be emitted laterally into a Si waveguide. From an 1.54-μm optically-pumped laser, a 3-dB frequency of 27 GHz was obtained at a pumping level corresponding to sub-mA. Using measured 3-dB frequen-cies and calculated equivalent currents, the modulation current efficiency factor (MCEF) is estimated to be 42.1 GHz/mA1/2, which is superior among microcavity lasers. This shows a high potential for a very high speed at low injection currents or avery small heat generation at high bitrates, which are highly desirable for both on-chip and off-chip applications.

  15. 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

  16. Ultrahigh-speed Si-integrated on-chip laser with tailored dynamic characteristics

    PubMed Central

    Park, Gyeong Cheol; Xue, Weiqi; Piels, Molly; Zibar, Darko; Mørk, Jesper; Semenova, Elizaveta; Chung, Il-Sug

    2016-01-01

    For on-chip interconnects, an ideal light source should have an ultralow energy consumption per bandwidth (operating en-ergy) as well as sufficient output power for error-free detection. Nanocavity lasers have been considered the most ideal for smaller operating energy. However, they have a challenge in obtaining a sufficient output power. Here, as an alternative, we propose an ultrahigh-speed microcavity laser structure, based on a vertical cavity with a high-contrast grating (HCG) mirror for transverse magnetic (TM) polarisation. By using the TM HCG, a very small mode volume and an un-pumped compact optical feedback structure can be realised, which together tailor the frequency response function for achieving a very high speed at low injection currents. Furthermore, light can be emitted laterally into a Si waveguide. From an 1.54-μm optically-pumped laser, a 3-dB frequency of 27 GHz was obtained at a pumping level corresponding to sub-mA. Using measured 3-dB frequen-cies and calculated equivalent currents, the modulation current efficiency factor (MCEF) is estimated to be 42.1 GHz/mA1/2, which is superior among microcavity lasers. This shows a high potential for a very high speed at low injection currents or avery small heat generation at high bitrates, which are highly desirable for both on-chip and off-chip applications. PMID:27934926

  17. Optically addressed asymmetric Fabry-Perot modulator

    NASA Technical Reports Server (NTRS)

    Larsson, A.; Maserjian, J.

    1991-01-01

    A low power, high contrast optically addressed modulator, operating with normal incidence, has been fabricated. Optically controlled reflection modulation is achieved through optically induced absorption modulation in a periodically delta-doped InGaAs/GaAs multiple quantum well structure inserted in an integrated asymmetric Fabry-Perot resonator. A contrast ratio over 60:1 was measured using a spectrally matched low power InGaAs/GaAs quantum well laser to generate the write (control) signal. The insertion loss for the normally off modulator is 4.6 dB at the highest write signal power (30 mW) used. The device lends itself to the fabrication of arrays for optically addressed spatial light modulation.

  18. The Reach Address Database (RAD)

    EPA Pesticide Factsheets

    The Reach Address Database (RAD) stores reach address information for each Water Program feature that has been linked to the underlying surface water features (streams, lakes, etc) in the National Hydrology Database (NHD) Plus dataset.

  19. Detection-gap-independent optical sensor design using divergence-beam-controlled slit lasers for wearable devices

    NASA Astrophysics Data System (ADS)

    Yoon, Young Zoon; Kim, Hyochul; Park, Yeonsang; Kim, Jineun; Lee, Min Kyung; Kim, Un Jeong; Roh, Young-Geun; Hwang, Sung Woo

    2016-09-01

    Wearable devices often employ optical sensors, such as photoplethysmography sensors, for detecting heart rates or other biochemical factors. Pulse waveforms, rather than simply detecting heartbeats, can clarify arterial conditions. However, most optical sensor designs require close skin contact to reduce power consumption while obtaining good quality signals without distortion. We have designed a detection-gap-independent optical sensor array using divergence-beam-controlled slit lasers and distributed photodiodes in a pulse-detection device wearable over the wrist's radial artery. It achieves high biosignal quality and low power consumption. The top surface of a vertical-cavity surface-emitting laser of 850 nm wavelength was covered by Au film with an open slit of width between 500 nm and 1500 nm, which generated laser emissions across a large divergence angle along an axis orthogonal to the slit direction. The sensing coverage of the slit laser diode (LD) marks a 50% improvement over nonslit LD sensor coverage. The slit LD sensor consumes 100% more input power than the nonslit LD sensor to obtain similar optical output power. The slit laser sensor showed intermediate performance between LD and light-emitting diode sensors. Thus, designing sensors with multiple-slit LD arrays can provide useful and convenient ways for incorporating optical sensors in wrist-wearable devices.

  20. 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.

  1. Raman fiber lasers

    NASA Astrophysics Data System (ADS)

    Supradeepa, V. R.; Feng, Yan; Nicholson, Jeffrey W.

    2017-02-01

    High-power fiber lasers have seen tremendous development in the last decade, with output powers exceeding multiple kilowatts from a single fiber. Ytterbium has been at the forefront as the primary rare-earth-doped gain medium owing to its inherent material advantages. However, for this reason, the lasers are largely confined to the narrow emission wavelength region of ytterbium. Power scaling at other wavelength regions has lagged significantly, and a large number of applications rely upon the diversity of emission wavelengths. Currently, Raman fiber lasers are the only known wavelength agile, scalable, high-power fiber laser technology that can span the wavelength spectrum. In this review, we address the technology of Raman fiber lasers, specifically focused on the most recent developments. We will also discuss several applications of Raman fiber lasers in laser pumping, frequency conversion, optical communications and biology.

  2. CONTENT-ADDRESSABLE MEMORY SYSTEMS,

    DTIC Science & Technology

    The utility of content -addressable memories (CAM’s) within a general purpose computing system is investigated. Word cells within CAM may be...addressed by the character of all or a part of cell contents . Multimembered sets of word cells may be addressed simultaneously. The distributed logical...package is developed which allows simulation of CAM commands within job programs run on the IBM 7090 and derives tallies of execution times corresponding to a particular realization of a CAM system . (Author)

  3. III-Nitride-on-silicon microdisk lasers from the blue to the deep ultra-violet

    NASA Astrophysics Data System (ADS)

    Sellés, J.; Crepel, V.; Roland, I.; El Kurdi, M.; Checoury, X.; Boucaud, P.; Mexis, M.; Leroux, M.; Damilano, B.; Rennesson, S.; Semond, F.; Gayral, B.; Brimont, C.; Guillet, T.

    2016-12-01

    We present a series of microdisk lasers realized within the same GaN-on-Si photonic platform scheme, and operating at room temperature under pulsed optical pumping over a broad spectral range extending over λ = 275 nm-470 nm. The III-nitride microdisks embed either binary GaN/AlN multiple quantum wells (MQWs) for UV operation, or ternary InGaN/GaN MQWs for violet and blue operation. This demonstrates the versatility of this nitride-on-silicon platform, and the realization on this platform of efficient active layers for lasing action over a 200 nm broad UV to visible spectral range. We probe the lasing threshold carrier density over the whole spectral range and found that it is similar whatever the emission wavelength for these Q > 1000 microdisk resonators with a constant material quality until quantum confined Stark effect takes over. The threshold is also found independent of microdisk diameters from 3 to 12 μm, with a β factor intermediate between the one of vertical cavity lasers and the one of small modal volume "thresholdless" lasers.

  4. Large-area high-power VCSEL pump arrays optimized for high-energy lasers

    NASA Astrophysics Data System (ADS)

    Wang, Chad; Geske, Jonathan; Garrett, Henry; Cardellino, Terri; Talantov, Fedor; Berdin, Glen; Millenheft, David; Renner, Daniel; Klemer, Daniel

    2012-06-01

    Practical, large-area, high-power diode pumps for one micron (Nd, Yb) as well as eye-safer wavelengths (Er, Tm, Ho) are critical to the success of any high energy diode pumped solid state laser. Diode efficiency, brightness, availability and cost will determine how realizable a fielded high energy diode pumped solid state laser will be. 2-D Vertical-Cavity Surface-Emitting Laser (VCSEL) arrays are uniquely positioned to meet these requirements because of their unique properties, such as low divergence circular output beams, reduced wavelength drift with temperature, scalability to large 2-D arrays through low-cost and high-volume semiconductor photolithographic processes, high reliability, no catastrophic optical damage failure, and radiation and vacuum operation tolerance. Data will be presented on the status of FLIR-EOC's VCSEL pump arrays. Analysis of the key aspects of electrical, thermal and mechanical design that are critical to the design of a VCSEL pump array to achieve high power efficient array performance will be presented.

  5. Microchip Lasers

    DTIC Science & Technology

    2016-10-31

    physics that underlies their performance, typical operating parameters for the devices, and several of their applications . Keywords Composite-cavity...laser, Diode -pumped laser, Laser, Microchip laser, Miniature laser, Monolithic laser, Passively Q-switched laser, Q-switched laser, Saturable...cavity mirrors are deposited directly on the gain medium and the laser is pumped with a diode laser, either directly, as shown in Fig. 1, or via an

  6. 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.

  7. 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.

  8. A Pedagogy to Address Plagiarism.

    ERIC Educational Resources Information Center

    Whitaker, Elaine E.

    1993-01-01

    Presents strategies and methods by which writing teachers can openly address the potential problem of plagiarism. Details specific methods used by one teacher to train students how to quote and cite materials without plagiarizing. (HB)

  9. Address tracing for parallel machines

    NASA Technical Reports Server (NTRS)

    Stunkel, Craig B.; Janssens, Bob; Fuchs, W. Kent

    1991-01-01

    Recently implemented parallel system address-tracing methods based on several metrics are surveyed. The issues specific to collection of traces for both shared and distributed memory parallel computers are highlighted. Five general categories of address-trace collection methods are examined: hardware-captured, interrupt-based, simulation-based, altered microcode-based, and instrumented program-based traces. The problems unique to shared memory and distributed memory multiprocessors are examined separately.

  10. 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)

  11. 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)

  12. Laser apparatus

    NASA Technical Reports Server (NTRS)

    Koepf, G. A. (Inventor)

    1979-01-01

    A laser apparatus having a pump laser device for producing pump laser energy upon being excited is disclosed. The pump laser device has a resonating cavity for oscillating and amplifying the pump laser energy. A source laser device is used for producing source laser energy upon being excited by the pump laser energy. The source laser device has a resonating cavity for oscillating and amplifying the source laser energy. The source laser's resonating cavity is coupled within a portion of the pump laser's resonating cavity.

  13. 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?"

  14. Nanoengineered InAs quantum dot active medium for laser diodes

    NASA Astrophysics Data System (ADS)

    Tokranov, Vadim E.; Yakimov, Michael; Katsnelson, Alex; Lamberti, Matthew; Agnello, Gabriel; Oktyabrsky, Serge

    2004-05-01

    Nanoengineering approach was used to develop an efficient active medium based on self-assembled InAs/GaAs quantum dots (QDs) for laser diodes operating at elevated temperatures. Photoluminescence (PL), transmission electron microscopy, and electroluminescence were used to study the influence of an overgrowth procedure on the properties of multiple-layer QDs. Optical properties of QDs were optimized by the adjustment of a GaAs overlayer thickness prior to a heating step, responsible for the truncation of the pyramid-shaped QDs. Triple-layer QD edge-emitting lasers with 1220 nm emitting wavelength exhibited a maximum saturated modal gain of 16 cm-1. To use truncated QD active medium for vertical cavity surface emitting lasers, seven layers of QDs with 20 nm of short period superlattice barriers between layers was developed. A wavelength of 1190 nm edge-emitting lasers with 120 nm total thickness 7xQDs active medium showed almost two times higher maximum saturated gain, 31 cm-1. Unfortunately, these lasers with closer distance between QD layers in active medium demonstrated stronger temperature dependence (with To = 110 K) of threshold current density and lasing wavelength. A record high characteristic temperature for lasing threshold, To = 380 K up to 55 C, was measured for edge-emitting laser diodes, which contained triple-layer truncated QD active medium. We believe that AlAs capping in combination with truncation procedure result in significant suppression of carrier transport between QDs within the layer as well as between QD layers.

  15. 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.

  16. Time-multiplexed, optically-addressed, gigabit optical crossbar switch

    NASA Technical Reports Server (NTRS)

    Lang, Robert J. (Inventor); Cheng, Li-Jen (Inventor); Maserjian, Joseph (Inventor)

    1994-01-01

    A time-multiplexed, optically-addressed, crossbar switch (38) is provided using a two-dimensional, optically-addressed, reflective spatial light modulator (O-SLM) (20). Since the optical addressing is time-multiplexed, only N addressing lines are required for an N.times.N crossbar, rather than the N.sup.2 lines needed in the prior art. This reduction in addressing lines makes possible the development of enormous crossbar switches, such as 100.times.100, for the first time. In addition, since data paths remain entirely in the optics domain, data speeds can reach the multi-gigabit level. In the switch, a row (40) of N inputs (42) at the read wavelength is spread over one axis of the O-SLM. The light is refocused along the other axis to an output array (48) of detectors (50), so that each input has the potential to talk to any one output. The O-SLM is normally off, i.e., non-reflective, so that the output is, in the absence of an input signal, zero. A one-dimensional array (52) of lasers (54) at the write wavelength is imaged onto the O-SLM. Each laser scans across an entire row of the O-SLM; where the laser is on, it turns on a portion of the O-SLM and establishes a connection between a particular input and a particular output. A full row is scanned in a time much shorter than the response time of the O-SLM, so that state of the O-SLM is capacitively stored and dynamically refreshed. The scanning is accomplished by tuning the wavelength of the laser and passing it through a grating, which sweeps the beam in space.

  17. 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.

  18. 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

    2014-06-02

    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.

  19. Microcavity Laser Based on a Single Molecule Thick High Gain Layer.

    PubMed

    Palatnik, Alexander; Aviv, Hagit; Tischler, Yaakov R

    2017-04-05

    The ability to confine excitons within monolayers has led to fundamental investigations of non-radiative energy transfer, super-radiance, strong light-matter coupling, high-efficiency LEDs, and recently lasers in lateral resonator architectures. Vertical Cavity Surface Emitting Lasers (VCSELs), in which lasing occurs perpendicular to the device plane, are critical for telecommunications and large-scale photonics integration, however strong optical self-absorption and low fluorescence quantum yields have thus far prevented coherent emission from a monolayer microcavity device. Here we show lasing from a monolayer VCSEL using a single molecule thick film of amphiphilic fluorescent dye, assembled via Langmuir-Blodgett deposition, as the gain layer. Threshold was observed when 5% of the molecules were excited (4.4 μJ/cm(2)). At this level of excitation, the optical gain in the monolayer exceeds 1056 cm(-1). High localization of the excitons in the VCSEL gain layer can enhance their collective emission properties with Langmuir-Blodgett deposition presenting a paradigm for engineering the high gain layers on the molecular level.

  20. 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.

  1. Surface-emitting, distributed-feedback diode lasers with uniform near-field intensity profile

    NASA Astrophysics Data System (ADS)

    Lopez, James; Kasraian, Masoud; Botez, Dan

    1998-10-01

    Theoretical analysis of second-order surface-emitting, complex-coupled distributed feedback diode lasers with first-order distributed Bragg reflectors (DBR) is presented. The DBR reflectors are shown to insure simultaneous operation in a virtually uniform near-field profile with high efficiency and adequate intermodal discrimination. Such devices display symmetric-mode (single-lobe) surface emission with relatively high external differential quantum efficiency (30%), low gain threshold (18 cm-1), and <8% near-field intensity profile variations (in the longitudinal direction). The devices have the potential to provide >100 mW of stable, single-mode cw power, significantly higher than it is possible with vertical-cavity surface-emitting lasers. It is also shown that the device studied here can be combined with a resonant optical waveguide array device to produce a 2D uniform near-field surface-emitting source capable of providing greater than 1 W cw power in a stable, single-lobed beam.

  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. Rapid monitoring of cerebral ischemia dynamics using laser-based optical imaging of blood oxygenation and flow

    PubMed Central

    Levy, Hart; Ringuette, Dene; Levi, Ofer

    2012-01-01

    Abstract: Imaging blood flow or oxygenation changes using optical techniques is useful for monitoring cortical activity in healthy subjects as well as in diseased states such as stroke or epilepsy. However, in order to gain a better understanding of hemodynamics in conscious, freely moving animals, these techniques must be implemented in a small scale, portable design that is adaptable to a wearable format. We demonstrate a novel system which combines the two techniques of laser speckle contrast imaging and intrinsic optical signal imaging simultaneously, using compact laser sources, to monitor induced cortical ischemia in a full field format with high temporal acquisition rates. We further demonstrate the advantages of using combined measurements of speckle contrast and oxygenation to establish absolute flow velocities, as well as to statistically distinguish between veins and arteries. We accomplish this system using coherence reduction techniques applied to Vertical Cavity Surface Emitting Lasers (VCSELs) operating at 680, 795 and 850 nm. This system uses minimal optical components and can easily be adapted into a portable format for continuous monitoring of cortical hemodynamics. PMID:22574265

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

    PubMed

    Gather, Malte C; Yun, Seok Hyun

    2014-12-08

    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.

  5. Material growth and characterization of gallium arsenic antimide on gallium arsenide grown by MOCVD for long wavelength laser applications

    NASA Astrophysics Data System (ADS)

    Noh, Min-Soo

    Due to the demand for faster and higher bit rate optical communication, long wavelength vertical cavity surface emitting laser (VCSEL) has been attracting great interests because of its ability of 2D array application. Although InGaAsP/InP edge emitting lasers (EEL) have been well developed and commercially available, the lack of high contrast distributed Bragg reflector (DBR) for the material system forced to find new active materials that can be grown on GaAs substrate to exploit AlGaAs/GaAs DBR pairs. For the purpose, GaAsSb has been studied as the active material. This dissertation describes and discusses the GaAsSb semiconductor material growth, the optimization of the growth conditions, and the characterization of the laser devices fabricated from GaAsSb QW structures. Based on the optimal growth conditions, EELs operating at room temperature in CW mode at the wavelength of 1.27 mum have been demonstrated from the GaAsSb QW structure with GaAsP barriers grown monolithically by MOCVD.

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

    PubMed Central

    Gather, Malte C.; Yun, Seok Hyun

    2015-01-01

    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. PMID:25483850

  7. RF noise induced laser perturbation for improving the performance of non-resonant cavity enhanced absorption spectroscopy.

    PubMed

    Ciaffoni, Luca; Couper, John; Hancock, Gus; Peverall, Robert; Robbins, Peter A; Ritchie, Grant A D

    2014-07-14

    We present a novel strategy for suppressing mode structure which often degrades off-axis cavity enhanced absorption spectra. This strategy relies on promoting small, random fluctuations in the optical frequency by perturbing the injection current of the diode laser source with radio frequency (RF) bandwidth-limited white noise. A fast and compact oxygen sensor, constructed from a 764 nm vertical-cavity surface-emitting laser (VCSEL) and an optical cavity with re-entrant configuration, is employed to demonstrate the potential of this scheme for improving the sensitivity and robustness of a field-deployable cavity spectrometer. The RF spectral density of the current noise injected into the VCSEL has been measured, and correlated to the effects on the optical spectral signal-to-noise ratio (SNR) and laser linewidth for a range of re-entrant geometries. A fourfold gain in the SNR has been achieved using the RF noise perturbation for the optimal off-axis alignment, which led to a minimum detectable absorption (MDA) predicted from an Allan variance study as low as 4.3 × 10(-5) at 1 s averaging. For the optically forbidden oxygen transition under investigation, a limit of detection (SNR = 1) of 810 ppm was achieved for a 10 ms acquisition time. This performance level paves the way for a fast, sensitive, in-line oxygen spectrometer that lends itself to a range of applications in respiratory medicine.

  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. State of the Lab Address

    ScienceCinema

    King, Alex

    2016-07-12

    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.

  10. Every Other Day. Keynote Address.

    ERIC Educational Resources Information Center

    Tiller, Tom

    Schools need to be reoriented and restructured so that what is taught and learned, and the way in which it is taught and learned, are better integrated with young people's real-world experiences. Many indicators suggest that the meaningful aspects of school have been lost in the encounter with modern times. The title of this address--"Every…

  11. Agenda to address climate change

    SciTech Connect

    1998-10-01

    This document looks at addressing climate change in the 21st century. Topics covered are: Responding to climate change; exploring new avenues in energy efficiency; energy efficiency and alternative energy; residential sector; commercial sector; industrial sector; transportation sector; communities; renewable energy; understanding forests to mitigate and adapt to climate change; the Forest Carbon budget; mitigation and adaptation.

  12. 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…

  13. 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…

  14. Addressing Student Diversity and Equity

    ERIC Educational Resources Information Center

    Januszyk, Rita; Miller, Emily C.; Lee, Okhee

    2016-01-01

    While student demographics continue to change nationwide, science achievement gaps persist, as measured by the National Assessment of Educational Progress (NCES 2012). As traditional racial and ethnic minority students have become the numeric majority (NCES 2013), teaching science for all increasingly means addressing diverse student populations.…

  15. Research strategies for addressing uncertainties

    USGS Publications Warehouse

    Busch, David E.; Brekke, Levi D.; Averyt, Kristen; Jardine, Angela; Welling, Leigh; Garfin, Gregg; Jardine, Angela; Merideth, Robert; Black, Mary; LeRoy, Sarah

    2013-01-01

    Research Strategies for Addressing Uncertainties builds on descriptions of research needs presented elsewhere in the book; describes current research efforts and the challenges and opportunities to reduce the uncertainties of climate change; explores ways to improve the understanding of changes in climate and hydrology; and emphasizes the use of research to inform decision making.

  16. Influence of laser sources with different spectral properties on the performance of vapor cell atomic clocks based on lin||lin CPT.

    PubMed

    Breschi, Evelina; Kazakov, George; Lammegger, Roland; Matisov, Boris; Windholz, Laurentius; Mileti, Gaetano

    2009-05-01

    We evaluate the influence of 2 types of laser sources with different spectral profiles on the performance of vapor cell atomic clocks based on lin||lin coherent population trapping (CPT) resonances. We show that a short-term stability of 1-2 x 10(-11) tau(-1/2) may be reached in a compact system using a modulated vertical cavity surface-emitting laser. Here the stability is limited by the detection noise level and can be improved up to a factor of 4 by increasing the lock-in detection frequency to several tens of kilohertz, which is not possible in standard double resonance atomic clocks. We compare these results with CPT prepared under the same experimental conditions, using 2 phase-locked extended cavity diode lasers, with which we predict a challenging short-term stability of 1-3 x 10(-13) tau(-1/2), comparable to the state-of-the-art laser-pumped Rb-clocks.

  17. Atomic clusters with addressable complexity

    NASA Astrophysics Data System (ADS)

    Wales, David J.

    2017-02-01

    A general formulation for constructing addressable atomic clusters is introduced, based on one or more reference structures. By modifying the well depths in a given interatomic potential in favour of nearest-neighbour interactions that are defined in the reference(s), the potential energy landscape can be biased to make a particular permutational isomer the global minimum. The magnitude of the bias changes the resulting potential energy landscape systematically, providing a framework to produce clusters that should self-organise efficiently into the target structure. These features are illustrated for small systems, where all the relevant local minima and transition states can be identified, and for the low-energy regions of the landscape for larger clusters. For a 55-particle cluster, it is possible to design a target structure from a transition state of the original potential and to retain this structure in a doubly addressable landscape. Disconnectivity graphs based on local minima that have no direct connections to a lower minimum provide a helpful way to visualise the larger databases. These minima correspond to the termini of monotonic sequences, which always proceed downhill in terms of potential energy, and we identify them as a class of biminimum. Multiple copies of the target cluster are treated by adding a repulsive term between particles with the same address to maintain distinguishable targets upon aggregation. By tuning the magnitude of this term, it is possible to create assemblies of the target cluster corresponding to a variety of structures, including rings and chains.

  18. Manipulating relativistic electrons with lasers

    NASA Astrophysics Data System (ADS)

    Malka, Victor

    2016-09-01

    The motion control of relativistic electrons with lasers allows for an efficient and elegant way to map the space with ultra-intense electric-field components, which, in turn, permits a unique improvement of the electron beam parameters. This perspective addresses the recent laser plasma accelerator experiments related to the phase space engineering of electron beams in a plasma medium performed at LOA.

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

    NASA Astrophysics Data System (ADS)

    Wakitani, Shunichi

    1998-08-01

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

  20. 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.

  1. 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

  2. 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.

  3. Addressing inequities in healthy eating.

    PubMed

    Friel, Sharon; Hattersley, Libby; Ford, Laura; O'Rourke, Kerryn

    2015-09-01

    What, when, where and how much people eat is influenced by a complex mix of factors at societal, community and individual levels. These influences operate both directly through the food system and indirectly through political, economic, social and cultural pathways that cause social stratification and influence the quality of conditions in which people live their lives. These factors are the social determinants of inequities in healthy eating. This paper provides an overview of the current evidence base for addressing these determinants and for the promotion of equity in healthy eating. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. 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.

  5. Laser processing for bio-microfluidics applications (part II).

    PubMed

    Khan Malek, Chantal G

    2006-08-01

    This paper reviews applications of laser-based techniques to the fabrication of microfluidic devices for biochips and addresses some of the challenges associated with the manufacture of these devices. Special emphasis is placed on the use of lasers for the rapid prototyping and production of biochips, in particular for applications in which silicon is not the preferred material base. This review addresses applications and devices based on ablation using femtosecond lasers, infrared lasers as well as laser-induced micro-joining, and the laser-assisted generation of micro-replication tools, for subsequent replication of polymeric chips with a technique like laser LIGA.

  6. 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.

  7. 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

  8. Content-addressable holographic databases

    NASA Astrophysics Data System (ADS)

    Grawert, Felix; Kobras, Sebastian; Burr, Geoffrey W.; Coufal, Hans J.; Hanssen, Holger; Riedel, Marc; Jefferson, C. Michael; Jurich, Mark C.

    2000-11-01

    Holographic data storage allows the simultaneous search of an entire database by performing multiple optical correlations between stored data pages and a search argument. We have recently developed fuzzy encoding techniques for this fast parallel search and demonstrated a holographic data storage system that searches digital data records with high fidelity. This content-addressable retrieval is based on the ability to take the two-dimensional inner product between the search page and each stored data page. We show that this ability is lost when the correlator is defocussed to avoid material oversaturation, but can be regained by the combination of a random phase mask and beam confinement through total internal reflection. Finally, we propose an architecture in which spatially multiplexed holograms are distributed along the path of the search beam, allowing parallel search of large databases.

  9. 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.

  10. 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.

  11. Excimer lasers and applications; Proceedings of the Meeting, Hamburg, Federal Republic of Germany, Sept. 21-23, 1988

    SciTech Connect

    Basting, D.

    1989-01-01

    Various papers on excimer lasers and applications are presented. Individual topics addressed include: trends in materials processing with laser radiation, high repetition at high power excimer lasers, excimer lasers with large discharge cross section, first results on high power excimer lasers, excimer lasers with capacitatively excited tubular discharges, 1 kW e-beam pumped excimer laser, femtosecond excimer lasers, stretching of excimer laser pulses, advanced control system for excimer lasers, optical control of high-power excimer lasers, excimer laser and geometric optics, UV-laser photoablation of polymers, accelerated laser aging of plastics, excimer laser surface treatment of nonferrous alloys, excimer lasers for materials processing, excimer laser-based machining of amorphous metals, surface treatments of metals with excimer lasers, optical fiber transmission of excimer laser pulses, European joint effort on kilowatt excimer lasers.

  12. 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.

  13. Laser principles.

    PubMed

    Bogdan Allemann, Inja; Kaufman, Joely

    2011-01-01

    Since the construction of the first laser in the 1960s, the role that lasers play in various medical specialities, including dermatology, has steadily increased. However, within the last 2 decades, the technological advances and the use of lasers in the field of dermatology have virtually exploded. Many treatments have only become possible with the use of lasers. Especially in aesthetic medicine, lasers are an essential tool in the treatment armamentarium. Due to better research and understanding of the physics of light and skin, there is now a wide and increasing array of different lasers and devices to choose from. The proper laser selection for each indication and treatment requires a profound understanding of laser physics and the basic laser principles. Understanding these principles will allow the laser operator to obtain better results and help avoid complications. This chapter will give an in-depth overview of the physical principles relevant in cutaneous laser surgery. Copyright © 2011 S. Karger AG, Basel.

  14. 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.

  15. Addressing physicians' impaired communication skills.

    PubMed

    Egener, Barry

    2008-11-01

    Deficient physician communication skills can lead to complaints by patients and colleagues. While there are many communication training courses for physicians, there are few descriptions of programs that address their deficiencies. This report describes the use of a coaching model developed by the author to remediate inadequate communication skills. The coaching model consists of a discrete set of communication skills that are gradually integrated into professional activities while debriefing that process in a supportive relationship. Outcomes are provided for the first 13 physicians coached after the approach was standardized. On a Likert scale (range, 1-7), with 7 expressing "high satisfaction," all participants rated the consultation in the 5-7 range (mean, 6.3), and all supervisors rated the consultation in the 6-7 range (mean, 6.7). A coaching model is effective in improving communication skills deemed inadequate by physicians' patients and colleagues. Future work should evaluate the impact of integrating coaching into health care organizations and on developing new tools to augment coaching.

  16. A region addresses patient safety.

    PubMed

    Feinstein, Karen Wolk; Grunden, Naida; Harrison, Edward I

    2002-06-01

    The Pittsburgh Regional Healthcare Initiative (PRHI) is a coalition of 35 hospitals, 4 major insurers, more than 30 major and small-business health care purchasers, dozens of corporate and civic leaders, organized labor, and partnerships with state and federal government all working together to deliver perfect patient care throughout Southwestern Pennsylvania. PRHI believes that in pursuing perfection, many of the challenges facing today's health care delivery system (eg, waste and error in the delivery of care, rising costs, frustration and shortage among clinicians and workers, financial distress, overcapacity, and lack of access to care) will be addressed. PRHI has identified patient safety (nosocomial infections and medication errors) and 5 clinical areas (obstetrics, orthopedic surgery, cardiac surgery, depression, and diabetes) as ideal starting points. In each of these areas of work, PRHI partners have assembled multifacility/multidisciplinary groups charged with defining perfection, establishing region-wide reporting systems, and devising and implementing recommended improvement strategies and interventions. Many design and conceptual elements of the PRHI strategy are adapted from the Toyota Production System and its Pittsburgh derivative, the Alcoa Business System. PRHI is in the proof-of-concept phase of development.

  17. Fiber lasers for material processing

    NASA Astrophysics Data System (ADS)

    Shiner, Bill

    2005-03-01

    Low power fiber lasers began entering the commercial markets in the early 1990s. Since their introduction, fiber lasers have rapidly progressed in power levels level with greatly improved beam quality to the point where they now exceed any other commercial material processing laser. These lasers, with single mode operation to 1 kilowatt and multi-mode operation to beyond 20 kilowatts, have high wall plug efficiency, an extremely compact footprint, are maintenance free and have a predicted diode life beyond 100,000 hours of continuous operation. Fiber lasers are making inroads into the scientific, medical, government, and in particular, material processing markets. These lasers have greatly expanded the application umbrella due to their unparallel performance combined with the ability to operate at different wavelengths, address remote applications and be propagated great distances in fiber. In the material processing markets, fiber lasers are rapidly gaining share in the automotive, microelectronic, medical device and marking markets, to name a few. The single mode lasers are redefining process parameters that have been accepted for decades. The high brightness multimode-kilowatt class lasers are achieving speeds and depths greater than comparable powered conventional lasers while providing the only commercial material processing lasers operating beyond 6 kilowatts at the 1 micron region.

  18. Laser clock

    SciTech Connect

    Facklam, R.L.

    1983-05-26

    A laser clock includes a linear laser in one embodiment of the clock and a ring laser gyro in the other embodiment. The linear laser is frequency stabilized and utilizes a single active medium in the form of a low pressure gas, such as He-Ne, with a Doppler broadened gain curve. The ring laser gyro is a four frequency laser with a Faraday rotor. Detector and electronic circuitry associated with the laser of each embodiment detects a beat frequency and convert it to a clock signal.

  19. 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.

  20. Blue Laser.

    DTIC Science & Technology

    1985-12-01

    HOLLOW CATHODE LASER FABRICATION 13 4. EXPERIENCE WITH THE BLUE LASER 18 4.1 Operational and Processing Experience 18 4.2 Performance Testing 20 5...34 -. - . •. SECTION 3 BLUE HOLLOW CATHODE LASER FABRICATION This section presents an overview of the steps taken in creating a HCL. There is...to the laser assembly. These steps can actually be considered as the final steps in laser fabrication because some of them involve adding various

  1. Novel hybrid laser modes in composite VCSEL-DFB microcavities (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Mischok, Andreas; Wagner, Tim; Sudzius, Markas; Brückner, Robert; Fröb, Hartmut; Lyssenko, Vadim G.; Leo, Karl

    2017-02-01

    Two of the most successful microcresonator concepts are the vertical cavity surface emitting laser (VCSEL), where light is confined between distributed Bragg reflectors (DBRs), and the distributed feedback (DFB) laser, where a periodic grating provides positive optical feedback to selected modes in an active waveguide (WG) layer. Our work concerns the combination of both into a composite device, facilitating coherent interaction between both regimes and giving rise to novel laser modes in the system. In a first realization, a full VCSEL stack with an organic active layer is evaporated on top of a diffraction grating with a large period (approximately 1 micron), leading to diffraction of waveguided modes into the surface emission of the device. Here, the coherent interaction between VCSEL and WG modes, as observed in an anticrossing of the dispersion lines, facilitates novel hybrid lasing modes with macroscopic in-plane coherence [1]. In further studies, we decrease the grating period of such devices to realise DFB conditions in a second-order Bragg grating which strongly couples photons via first-order light diffraction to the VCSEL. This efficient coupling can be compared to more classical cascade-coupled cavities and is successfully described by a coupled oscillator model [2]. When both resonators are non-degenerate, they are able to function as independent structures without substantial diffraction losses. The realization of such novel devices provides a promising platform for photonic circuits based on organic microlasers. [1] A. Mischok et al., Adv. Opt. Mater., early online, DOI: 10.1002/adom.201600282, (2016) [2] T. Wagner et al., Appl. Phys. Lett., accepted, in production, (2016)

  2. 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.

  3. 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.

  4. Wurtzite spin lasers

    NASA Astrophysics Data System (ADS)

    Faria Junior, Paulo E.; Xu, Gaofeng; Chen, Yang-Fang; Sipahi, Guilherme M.; Žutić, Igor

    2017-03-01

    Semiconductor lasers are strongly altered by adding spin-polarized carriers. Such spin lasers could overcome many limitations of their conventional (spin-unpolarized) counterparts. While the vast majority of experiments in spin lasers employed zinc-blende semiconductors, the room-temperature electrical manipulation was first demonstrated in wurtzite GaN-based lasers. However, the underlying theoretical description of wurtzite spin lasers is still missing. To address this situation, focusing on (In,Ga)N-based wurtzite quantum wells, we develop a theoretical framework in which the calculated microscopic spin-dependent gain is combined with a simple rate equation model. A small spin-orbit coupling in these wurtzites supports simultaneous spin polarizations of electrons and holes, providing unexplored opportunities to control spin lasers. For example, the gain asymmetry, as one of the key figures of merit related to spin amplification, can change the sign by simply increasing the carrier density. The lasing threshold reduction has a nonmonotonic dependence on electron-spin polarization, even for a nonvanishing hole spin polarization.

  5. Laser Analyzer

    NASA Technical Reports Server (NTRS)

    1993-01-01

    Dopant level analysis is important to the laser system designer because it allows him to model the laser's performance. It also allows the end user to determine what went wrong when a laser fails to perform as expected. Under a Small Business Innovation Research (SBIR) contract, Scientific Materials Corporation has developed a process for producing uniform laser rods in which the amount of water trapped in the crystal during growth is reduced. This research led to the formation of a subsidiary company, Montana Analytical Services, which conducts analysis of laser rods for dopant ion concentrations. This is a significant advance in laser technology.

  6. 16 CFR 0.2 - Official address.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... Official address. The principal office of the Commission is at Washington, DC. All communications to the Commission should be addressed to the Federal Trade Commission, 600 Pennsylvania Avenue, NW, Washington,...

  7. 16 CFR 0.2 - Official address.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... Official address. The principal office of the Commission is at Washington, DC. All communications to the Commission should be addressed to the Federal Trade Commission, 600 Pennsylvania Avenue, NW, Washington,...

  8. 16 CFR 0.2 - Official address.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Official address. The principal office of the Commission is at Washington, DC. All communications to the Commission should be addressed to the Federal Trade Commission, 600 Pennsylvania Avenue, NW, Washington, DC...

  9. 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

  10. 37 CFR 41.10 - Correspondence addresses.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2014-07-01 2014-07-01 false Correspondence addresses. 41... Correspondence addresses. Except as the Board may otherwise direct, (a) Appeals. Correspondence in an application... correspondence in an application or a patent involved in an appeal to the Board for which an address is...

  11. 37 CFR 41.10 - Correspondence addresses.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2013-07-01 2013-07-01 false Correspondence addresses. 41... Correspondence addresses. Except as the Board may otherwise direct, (a) Appeals. Correspondence in an application... correspondence in an application or a patent involved in an appeal to the Board for which an address is...

  12. 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 regulated...

  13. 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 regulated...

  14. 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 regulated...

  15. 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 regulated...

  16. 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 regulated...

  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. 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...

  19. 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.

  20. 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.

  1. Lasers and laser-like devices: part two.

    PubMed

    Sebaratnam, Deshan F; Lim, Adrian C; Lowe, Patricia M; Goodman, Greg J; Bekhor, Philip; Richards, Shawn

    2014-02-01

    Part two of this review series evaluates the use of lasers and laser-like devices in dermatology based on published evidence and the collective experience of the senior authors. Dermatologists can laser-treat a wide range of dermatoses, including vascular, pigmentary, textural, benign proliferative and premalignant conditions. Some of these conditions include vascular malformation, haemangioma, facial telangiectases, café-au-lait macules, naevi of Ota, lentigines, acne scarring, rhytides, rhinophyma and miscellaneous skin lesions. Photodynamic therapy with lasers and intense pulsed light is addressed, with particular reference to actinic keratosis and actinic cheilitis. A treatment algorithm for acne scarring based on scar morphology and severity is comprehensively outlined. Following from part one, the various devices are matched to the corresponding dermatological conditions with representative pictorial case vignettes illustrating likely clinical outcomes as well as limitations and potential complications of the various laser and light therapies.

  2. 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.

  3. Laser sampling

    NASA Astrophysics Data System (ADS)

    Gorbatenko, A. A.; Revina, E. I.

    2015-10-01

    The review is devoted to the major advances in laser sampling. The advantages and drawbacks of the technique are considered. Specific features of combinations of laser sampling with various instrumental analytical methods, primarily inductively coupled plasma mass spectrometry, are discussed. Examples of practical implementation of hybrid methods involving laser sampling as well as corresponding analytical characteristics are presented. The bibliography includes 78 references.

  4. 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.

  5. 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.

  6. Laser tweezer actuated microphotonic array devices for high resolution imaging and analysis in chip-based biosystems

    NASA Astrophysics Data System (ADS)

    Birkbeck, Aaron L.

    A new technology is developed that functionally integrates arrays of lasers and micro-optics into microfluidic systems for the purpose of imaging, analyzing, and manipulating objects and biological cells. In general, the devices and technologies emerging from this area either lack functionality through the reliance on mechanical systems or provide a serial-based, time consuming approach. As compared to the current state of art, our all-optical design methodology has several distinguishing features, such as parallelism, high efficiency, low power, auto-alignment, and high yield fabrication methods, which all contribute to minimizing the cost of the integration process. The potential use of vertical cavity surface emitting lasers (VCSELs) for the creation of two-dimensional arrays of laser optical tweezers that perform independently controlled, parallel capture, and transport of large numbers of individual objects and biological cells is investigated. One of the primary biological applications for which VCSEL array sourced laser optical tweezers are considered is the formation of engineered tissues through the manipulation and spatial arrangement of different types of cells in a co-culture. Creating devices that combine laser optical tweezers with select micro-optical components permits optical imaging and analysis functions to take place inside the microfluidic channel. One such device is a micro-optical spatial filter whose motion and alignment is controlled using a laser optical tweezer. Unlike conventional spatial filter systems, our device utilizes a refractive optical element that is directly incorporated onto the lithographically patterned spatial filter. This allows the micro-optical spatial filter to automatically align itself in three-dimensions to the focal point of the microscope objective, where it then filters out the higher frequency additive noise components present in the laser beam. As a means of performing high resolution imaging in the

  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.

  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. 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.

  10. Cutaneous lasers.

    PubMed

    Fedok, Fred G; Garritano, Frank; Portela, Antonio

    2013-02-01

    There has been a remarkable development and evolution of laser technology, leading to adaptation of lasers for medical use and the treatment of skin problems and disorders. Many treatments that required incisional surgery and other invasive methods are now preferentially treated with a laser. Although laser advances have resulted in the availability of some amazing tools, they require the clinical skill and judgment of the clinician for their optimal use. This article provides a clinically oriented overview of many of the lasers valuable in facial plastic surgery. Basic science, clinical adaptations, and patient management topics are covered. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Quality-switched laser tattoo removal.

    PubMed

    Williams, Nkaya

    2014-06-01

    Quality-switched (Q-switched) laser is the most effective method to remove tattoos with minimal adverse outcomes. This article reviews the types of tattoos commonly treated with Q-switched lasers, mechanisms behind the procedure, technologies used, patient considerations and contraindications, addressing patient expectations, treatment procedures, possible adverse reactions, and future techniques and technology.

  17. An Integrated Approach to Laser Crystal Development

    NASA Technical Reports Server (NTRS)

    Ries, Heidi R.

    1996-01-01

    Norfolk State University has developed an integrated research program in the area of laser crystal development, including crystal modeling, crystal growth, spectroscopy, and laser modeling. This research program supports a new graduate program in Chemical Physics, designed in part to address the shortage of minority scientists.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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)

  4. 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…

  5. 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…

  6. 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 Official address. The principal office of the Commission is at Washington, DC. All communications to the...

  7. 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....

  8. 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…

  9. 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…

  10. 37 CFR 41.10 - Correspondence addresses.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2011-07-01 2011-07-01 false Correspondence addresses. 41....10 Correspondence addresses. Except as the Board may otherwise direct, (a) Appeals. Correspondence in... all other correspondence in an application or a patent involved in an appeal to the Board for which...

  11. 37 CFR 41.10 - Correspondence addresses.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2012-07-01 2012-07-01 false Correspondence addresses. 41....10 Correspondence addresses. Except as the Board may otherwise direct, (a) Appeals. Correspondence in... all other correspondence in an application or a patent involved in an appeal to the Board for which...

  12. 37 CFR 41.10 - Correspondence addresses.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 37 Patents, Trademarks, and Copyrights 1 2010-07-01 2010-07-01 false Correspondence addresses. 41....10 Correspondence addresses. Except as the Board may otherwise direct, (a) Appeals. Correspondence in... all other correspondence in an application or a patent involved in an appeal to the Board for which...

  13. 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..., DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If mail... litigation; (2) The account is assigned to the United States; or (3) The account is written off under §...

  14. 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..., DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Due Diligence § 674.44 Address searches. (a) If mail... litigation; (2) The account is assigned to the United States; or (3) The account is written off under §...

  15. 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…

  16. 49 CFR 1102.1 - How addressed.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 8 2010-10-01 2010-10-01 false How addressed. 1102.1 Section 1102.1 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT OF TRANSPORTATION RULES OF PRACTICE COMMUNICATIONS § 1102.1 How addressed. All communications...

  17. 49 CFR 1102.1 - How addressed.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 8 2013-10-01 2013-10-01 false How addressed. 1102.1 Section 1102.1 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT OF TRANSPORTATION RULES OF PRACTICE COMMUNICATIONS § 1102.1 How addressed. All communications...

  18. 49 CFR 1102.1 - How addressed.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 8 2014-10-01 2014-10-01 false How addressed. 1102.1 Section 1102.1 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT OF TRANSPORTATION RULES OF PRACTICE COMMUNICATIONS § 1102.1 How addressed. All communications...

  19. 49 CFR 1102.1 - How addressed.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 8 2012-10-01 2012-10-01 false How addressed. 1102.1 Section 1102.1 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT OF TRANSPORTATION RULES OF PRACTICE COMMUNICATIONS § 1102.1 How addressed. All communications...

  20. 49 CFR 1102.1 - How addressed.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 8 2011-10-01 2011-10-01 false How addressed. 1102.1 Section 1102.1 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT OF TRANSPORTATION RULES OF PRACTICE COMMUNICATIONS § 1102.1 How addressed. All communications...