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Sample records for airbridges

  1. Fabrication and characterization of aluminum airbridges for superconducting microwave circuits

    SciTech Connect

    Chen, Zijun; Kelly, J.; Barends, R.; Bochmann, J.; Chen, Yu; Chiaro, B.; Dunsworth, A.; Jeffrey, E.; Mutus, J. Y.; O'Malley, P. J. J.; Neill, C.; Roushan, P.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T. C.; Megrant, A.; Cleland, A. N.; Martinis, John M.

    2014-02-03

    Superconducting microwave circuits based on coplanar waveguides (CPW) are susceptible to parasitic slotline modes which can lead to loss and decoherence. We motivate the use of superconducting airbridges as a reliable method for preventing the propagation of these modes. We describe the fabrication of these airbridges on superconducting resonators, which we use to measure the loss due to placing airbridges over CPW lines. We find that the additional loss at single photon levels is small, and decreases at higher drive powers.

  2. Air-bridge and Vertical CNT Switches for High Performance Switching Applications

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Wong, Eric W.; Epp, Larry; Bronikowski, Michael J.; Hunt, BBrian D.

    2006-01-01

    Carbon nanotubes are attractive for switching applications since electrostatically-actuated CNT switches have low actuation voltages and power requirements, while allowing GHz switching speeds that stem from the inherently high elastic modulus and low mass of the CNT.Our first NEM structure, the air-bridge switch, consists of suspended single-walled nanotubes (SWNTs) that lie above a sputtered Nb base electrode, where contact to the CNTs is made using evaporated Au/Ti. Electrical measurements of these air-bridge devices show well-defined ON and OFF states as a dc bias of a few volts is applied between the CNT and the Nb-base electrode. The CNT air-bridge switches were measured to have switching times down to a few nanoseconds. Our second NEM structure, the vertical CNT switch, consists of nanotubes grown perpendicular to the substrate. Vertical multi-walled nanotubes (MWNTs) are grown directly on a heavily doped Si substrate, from 200 - 300 nm wide, approximately 1 micrometer deep nano-pockets, with Nb metal electrodes to result in the formation of a vertical single-pole-double-throw switch architecture.

  3. Design and fabrication of indium phosphide air-bridge waveguides with MEMS functionality

    NASA Astrophysics Data System (ADS)

    Ng, Wing H.; Podoliak, Nina; Horak, Peter; Wu, Jiang; Liu, Huiyun; Stewart, William J.; Kenyon, Anthony J.

    2015-05-01

    We present the design and fabrication of a dual air-bridge waveguide structure integrated with MEMS functionality. The structure is designed to function as a tunable optical buffer for telecommunication application. The optical buffer structure is based on two parallel waveguides made of high refractive index material with subwavelength dimensions. They are suspended in air, and are separated by a sub-micron air gap. Due to the fact that the size of the waveguides is much smaller than the wavelength of light that propagates in the structure, a significant fraction of the optical mode is in the air gap between the waveguides. By changing the size of the air gap using MEMS techniques, we can vary this fraction and hence the effective refractive index of the waveguide structure, thus generating tunable optical delay. The optical buffer structure was grown on an InP substrate by molecular beam epitaxy, and the device layer was made of InGaP. An InGaAs layer was sandwiched between the device layer and the substrate to serve as a sacrificial layer. The sub-micron waveguides, their supports in the form of side pillars with tapered shapes in order to minimize optical losses, and the MEMS structures were patterned using electron beam lithography and plasma etching. Electrodes were integrated into the structure to provide electrostatic actuation. After the sample patterning, the waveguide structure was released using HF etch. Our simulations predict that by varying the waveguide separation from 50 nm to 500 nm, we could achieve a change in propagation delay by a factor of two.

  4. Room-temperature light emission from an airbridge double-heterostructure microcavity of Er-doped Si photonic crystal

    NASA Astrophysics Data System (ADS)

    Wang, Yue; An, Jun-ming; Wu, Yuan-da; Hu, Xiong-wei

    2016-01-01

    We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional (2D) hexagonal photonic crystal (PC) airbridge double-heterostructure microcavity with Er-doped silicon (Si) as light emitters on siliconon-insulator (SOI) wafer at room temperature. A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence (PL) spectrum with the pumping power of 12.5 mW. The obvious red shift and the degraded quality factor (Q-factor) of resonant peak appear with the pumping power increasing, and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 mW. The resonant peak is observed to shift depending on the structural parameters of PC, which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.

  5. Air-bridged lateral growth of an Al0.98Ga0.02N layer by introduction of porosity in an AlN buffer

    NASA Astrophysics Data System (ADS)

    Wang, T.; Bai, J.; Parbrook, P. J.; Cullis, A. G.

    2005-10-01

    We demonstrated air-bridged lateral growth of an Al0.98Ga0.02N layer with significant dislocation reduction by introduction of a porous AlN buffer underneath via metalorganic chemical vapor deposition. By modifying growth conditions, a porous AlN layer and an atomically flat AlN layer have been obtained for comparison, confirmed by atomic force microscopy. An Al0.98Ga0.02N layer was subsequently grown on both the porous AlN layer and the atomically flat AlN layer under identical conditions. Significant dislocation reduction was achieved for the Al0.98Ga0.02N layer grown on the porous AlN buffer layer, compared to the layer grown on the atomically flat AlN layer, as observed by transmission electron microscopy. Clear bubbles from the layer grown on the porous AlN buffer layer have been observed, while in contrast, there was not any bubble from the layer on the flat AlN buffer, confirming the mechanism of lateral growth for dislocation reduction. Asymmetric x-ray diffraction studies also indicated that the crystal quality was dramatically improved using the porous AlN buffer layer.

  6. The French airbridge for circulatory support in the Carribean†

    PubMed Central

    Lebreton, Guillaume; Sanchez, Bruno; Hennequin, Jean-Luc; Resière, Dabor; Hommel, Didier; Léonard, Christian; Mehdaoui, Hossein; Roques, François

    2012-01-01

    OBJECTIVES We report the assessment and the activities for the first year of our airborne circulatory support mobile unit (CSMU) in the French Caribbean. METHODS From January 2010 to June 2011, 12 patients (mean age = 35.7 years; range: 15–62 years; sex ratio = 1:1) were attended outside Martinique by our CSMU and transferred to our unit by air. RESULTS Eight patients had acute respiratory distress syndrome and were assisted by veno-venous extra corporeal membrane oxygenation (ECMO) four had refractory cardiogenic shock, assisted by extra corporeal life support (ECLS). The average air transfer distance for patients was 912 km (range: 198–1585 km). The average flying time was 124 min (range: 45–255 min). The aircraft used were heliciopter, military transport or private jet. The setting-up of assistance devices and transfer of patients was uneventful. One patient subsequently benefited from heart transplantation after long-term circulatory support. One patient died under ECMO support after 51 days of assistance and another died on the 60th day after withdrawal of ECLS. CONCLUSIONS CSMUs can be very efficient in providing support to patients in refractory shock, when remote from a cardiac surgery centre. The airborne transfer of patients on ECMO/ECLS can be achieved safely, even over long distances. PMID:22659268

  7. Prolonged spontaneous emission and dephasing of localized excitons in air-bridged carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sarpkaya, Ibrahim; Zhang, Zhengyi; Walden-Newman, William; Wang, Xuesi; Hone, James; Wong, Chee W.; Strauf, Stefan

    2013-07-01

    The bright exciton emission of carbon nanotubes is appealing for optoelectronic devices and fundamental studies of light-matter interaction in one-dimensional nanostructures. However, to date, the photophysics of excitons in carbon nanotubes is largely affected by extrinsic effects. Here we perform time-resolved photoluminescence measurements over 14 orders of magnitude for ultra-clean carbon nanotubes bridging an air gap over pillar posts. Our measurements demonstrate a new regime of intrinsic exciton photophysics with prolonged spontaneous emission times up to T1=18 ns, about two orders of magnitude better than prior measurements and in agreement with values hypothesized by theorists about a decade ago. Furthermore, we establish for the first time exciton decoherence times of individual nanotubes in the time domain and find fourfold prolonged values up to T2=2.1 ps compared with ensemble measurements. These first observations motivate new discussions about the magnitude of the intrinsic dephasing mechanism while the prolonged exciton dynamics is promising for applications.

  8. Air-bridge high-speed InGaAs/InP waveguide photodiode

    NASA Astrophysics Data System (ADS)

    Yang, H.; Daunt, C. L. L. M.; Han, W.; Thomas, K.; Corbett, B.; Peters, F. H.

    2012-04-01

    The photodiode (PD) is a key component in optical transmission and optical measurement systems which receive optical signals and convert them into electric signals. High speed, high responsivity, high power and low dark current are desirable attributes of the PD in these applications, but also a simple fabrication process for high yield and low cost is essential for industry production. In this paper, an undercut-air-bridge high speed InGaAs/InP PIN structural photodiode is presented. By utilizing the crystal orientation dependent wet etching of InP material and designing the arms of the bridge with proper angle, the air bridge was easily obtained, which greatly eased the fabrication. The fabricated devices with 120μm×3μm ridge waveguides work robustly up to 30GHz in the measurements and potentially faster with optimized material.

  9. A theoretical and experimental study of coplanar waveguide shunt stubs

    NASA Technical Reports Server (NTRS)

    Dib, Nihad I.; Ponchak, George E.; Katehi, Linda P. B.

    1993-01-01

    A comprehensive theoretical and experimental study of straight and bent coplanar waveguide (CPW) shunt stubs is presented. In the theoretical analysis, the CPW is assumed to be inside a cavity while, the experiments are performed on open structures. For the analysis of CPW discontinuities with air-bridges, a hybrid technique was developed which was validated through extensive theoretical and experimental comparisons. The effect of the cavity resonances on the behavior of the stubs with and without air-bridges is investigated. In addition, the encountered radiation loss due to the discontinuities is evaluated experimentally.

  10. Effects of Ground Equalization on the Electrical Performance of Asymmetric CPW Shunt Stubs

    NASA Technical Reports Server (NTRS)

    Dib, Nihad; Gupta, Minoo; Ponchak, George; Katehi, Linda

    1993-01-01

    A hybrid technique is used to study the effects of ground equalization on the electrical performance of CPW shunt stubs. Extensive experiments have been performed and the results are in good agreement with theoretical data. The advantages of using air-bridges in CPW circuits as opposed to bond-wires are also discussed.

  11. Effects of capacitance at crossover wirings in power GaAs M.E.S.F.E.T.s

    NASA Astrophysics Data System (ADS)

    Aono, Y.; Higashisaka, A.; Hasegawa, F.

    1980-05-01

    Power GaAs FETs with an air-bridge crossover were compared with those of SiO2 crossover to find the effect of the capacitance at the crossover points. The capacitance of SiO2 crossover points is much smaller than that of the gate pad or the gate busbar in power GaAs FETs, and deterioration of the microwave performance due to that capacitance is negligible.

  12. Ultraflexible nanostructures and implications for future nanorobots

    NASA Astrophysics Data System (ADS)

    Cohn, Robert W.; Panchapakesan, Balaji

    2016-05-01

    Several high aspect ratio nanostructures have been made by capillary force directed self-assembly including polymeric nanofiber air-bridges, trampoline-like membranes, microsphere-beaded nanofibers, and intermetallic nanoneedles. Arrays of polymer air-bridges form in seconds by simply hand brushing a bead of polymeric liquid over an array of micropillars. The domination of capillary force that is thinning unstable capillary bridges leads to uniform arrays of nanofiber air-bridges. Similarly, arrays of vertically oriented Ag2Ga nanoneedles have been formed by dipping silvercoated arrays of pyramidal silicon into melted gallium. Force-displacement measurements of these structures are presented. These nanostructures, especially when compressively or torsionally buckled, have extremely low stiffnesses, motion due to thermal fluctuations that is relatively easily detected, and the ability to move great distances for very small changes in applied force. Nanofibers with bead-on-a-string structure, where the beads are micron diameter and loaded with magnetic iron oxide (maghemite), are shown to be simply viewable under optical microscopes, have micronewton/ m stiffness, and have ultralow torsional stiffnesses enabling the bead to be rotated numerous revolutions without breaking. Combination of these high aspect ratio structures with stretched elastomers offer interesting possibilities for robotic actuation and locomotion. Polydimethylsiloxane loaded with nanomaterials, e.g. nanotubes, graphene or MoS2, can be efficiently heated with directed light. Heating produces considerable force through the thermoelastic effect, and this force can be used for continuous translation or to trigger reversible elastic buckling of the nanostructures. The remote stimulation of motion with light provides a possible mechanism for producing cooperative behavior between swarms of semiautonomous nanorobots.

  13. High-sensitivity and high-Q-factor glass photonic crystal cavity and its applications as sensors.

    PubMed

    Siraji, Ashfaqul Anwar; Zhao, Yang

    2015-04-01

    We investigate the properties of a planar photonic crystal cavity on glass and its applications as sensors. An airbridged twofold defect cavity on Schott glass background and Gorilla glass substrate has been designed for high Q-factor up to 4459. The average sensitivity of the cavity resonance to background refractive index is 388 nm/Refractive Index Unit. The resonant wavelength is sensitive to background temperature by 18.5 pm/°C. The designed sensors show much higher sensitivity than those based on waveguide interferometers or photonic bandgap structures without cavity resonance. The results are also useful for experimental studies of glass photonic devices. PMID:25831371

  14. High-speed, room-temperature quantum cascade detectors at 4.3 μm

    NASA Astrophysics Data System (ADS)

    Zhou, Yuhong; Zhai, Shenqiang; Wang, Fengjiao; Liu, Junqi; Liu, Fengqi; Liu, Shuman; Zhang, Jinchuan; Zhuo, Ning; Wang, Lijun; Wang, ZhanGuo

    2016-03-01

    We present high-speed, room-temperature operated 4.3 μm quantum cascade detectors. The devices are processed as square mesas with 50 Ω coplanar access line and air-bridge connector. The high frequency features are explored using microwave rectification technique and a RLC circuit model. The -3 dB cutoff frequency is experimentally 9 GHz and 4 GHz for 20×20 μm2 and 50×50 μm2 detectors, respectively. The equivalent circuit analysis shows that a second order filter feature governs the devices. Higher cutoff frequency can be achieved by eliminate the parasitics further.

  15. Array integration of thousands of photonic crystal nanolasers

    SciTech Connect

    Watanabe, Takumi Abe, Hiroshi; Nishijima, Yoshiaki; Baba, Toshihiko

    2014-03-24

    Photonic crystal (PC) nanolasers often consist of air-bridge PC slab, which enhances optical confinement while limiting its size to 30 × 30 μm{sup 2} due to the mechanical fragileness. This limit is broken by resin-mediated bonding of the PC slab on a host substrate. In this paper, we demonstrate a GaInAsP PC slab with a size of over 100 × 100 μm{sup 2} in which 1089, 2376, and 11 664 nanolasers showing high-yield laser operation are integrated.

  16. Direct three-dimensional patterning using nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Li, Mingtao; Chen, Lei; Chou, Stephen Y.

    2001-05-01

    We demonstrated that nanoimprint lithography (NIL) can create three-dimensional patterns, sub-40 nm T-gates, and air-bridge structures, in a single step imprint in polymer and metal by lift-off. A method based on electron beam lithography and reactive ion etching was developed to fabricate NIL molds with three-dimensional protrusions. The low-cost and high-throughput nanoimprint lithography for three-dimensional nanostructures has many significant applications such as monolithic microwave integrated circuits and nanoelectromechanical system.

  17. Enhanced performance of VOx-based bolometer using patterned gold black absorber

    NASA Astrophysics Data System (ADS)

    Smith, Evan M.; Panjwani, Deep; Ginn, James; Warren, Andrew; Long, Christopher; Figuieredo, Pedro; Smith, Christian; Perlstein, Joshua; Walter, Nick; Hirschmugl, Carol; Peale, Robert E.; Shelton, David J.

    2015-06-01

    Patterned highly absorbing gold black film has been selectively deposited on the active surfaces of a vanadium-oxide-based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves gold black's near unity absorption. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. Infrared responsivity is substantially improved by the gold black coating without significantly increasing noise. The increase in the time constant caused by the additional mass of gold black is a modest 14%.

  18. A comprehensive theoretical and experimental study of coplanar waveguide shunt stubs

    NASA Technical Reports Server (NTRS)

    Dib, Nihad I.; Ponchak, George E.; Katehi, Linda P. B.

    1993-01-01

    A comprehensive theoretical and experimental study of straight and bent coplanar waveguide (CPW) shunt stubs is presented. In the theoretical analysis, the CPW is assumed to be inside a cavity, while, the experiments are performed on open structures. A hybrid technique was developed to analyze the CPW discontinuities which proved to be accurate since the theoretical and experimental results agree very well. The effect of the cavity resonances on the behavior of the stubs with and without air-bridges is investigated. In addition, the encountered radiation loss due to the discontinuities is evaluated experimentally.

  19. Array integration of thousands of photonic crystal nanolasers

    NASA Astrophysics Data System (ADS)

    Watanabe, Takumi; Abe, Hiroshi; Nishijima, Yoshiaki; Baba, Toshihiko

    2014-03-01

    Photonic crystal (PC) nanolasers often consist of air-bridge PC slab, which enhances optical confinement while limiting its size to 30 × 30 μm2 due to the mechanical fragileness. This limit is broken by resin-mediated bonding of the PC slab on a host substrate. In this paper, we demonstrate a GaInAsP PC slab with a size of over 100 × 100 μm2 in which 1089, 2376, and 11 664 nanolasers showing high-yield laser operation are integrated.

  20. Discrete GaAs microwave devices for satellite TV converter front ends

    NASA Astrophysics Data System (ADS)

    Pettenpaul, E.; Langer, E.; Huber, J.; Mampe, H.; Zimmermann, W.

    GaAs microwave devices for receiver front ends, especially for the home reception of satellite broadcasts in the region of 12 GHz, are reported. The basic devices used are micron and submicron single- and dual-gate MESFETs as amplifiers, oscillators, mixers and lumped elements for impedance-matching circuitry and filters. The results of chip measurements and modeling are reported. In particular, noise figures below 2 dB have been realized for the halfmicron MESFET at 12 GHz, below 2.5 dB for a single-stage monolithic broadband amplifier at 1.5 GHz, and 2.7 dB for a complete hybrid ECS down-converter module. The process technology includes direct selective ion implantation, submicron gate definition and airbridge crossovers.

  1. Dual band sensitivity enhancements of a VO(x) microbolometer array using a patterned gold black absorber.

    PubMed

    Smith, Evan M; Panjwani, Deep; Ginn, James; Warren, Andrew P; Long, Christopher; Figuieredo, Pedro; Smith, Christian; Nath, Janardan; Perlstein, Joshua; Walter, Nick; Hirschmugl, Carol; Peale, Robert E; Shelton, David

    2016-03-10

    Infrared-absorbing gold black has been selectively patterned onto the active surfaces of a vanadium-oxide-based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves much of gold black's high absorptance. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. For our fabricated devices, infrared responsivity is improved 22% in the long-wave IR and 70% in the mid-wave IR by the gold black coating, with no significant change in detector noise, using a 300°C blackbody and 80 Hz chopping rate. The increase in the time constant caused by the additional mass of gold black is ∼15%. PMID:26974804

  2. Directional whispering gallery mode emission from Limaçon-shaped electrically pumped quantum dot micropillar lasers

    NASA Astrophysics Data System (ADS)

    Albert, F.; Hopfmann, C.; Eberspächer, A.; Arnold, F.; Emmerling, M.; Schneider, C.; Höfling, S.; Forchel, A.; Kamp, M.; Wiersig, J.; Reitzenstein, S.

    2012-07-01

    We experimentally demonstrate directional far field emission from whispering gallery modes (WGMs) in electrically driven quantum dot micropillar lasers. In-plane directionality of whispering gallery mode emission is obtained by patterning micropillars with Limaçon-shaped cross-section and an upper air-bridge contact for current injection. The micropillar lasers with radii R0 down to 4.5 μm show Q-factors of 40 000 and threshold currents of 40 μA at low temperature. We achieved a far field divergence of about 30° and a directionality of 1.67 ± 0.15 for an optimal Limaçon deformation factor ɛ ≈ 0.5. Parameter dependent studies of the directional emission as a function of ɛ reveal good qualitative agreement with theoretical predictions.

  3. Advanced fabrication technologies for nano-electronics

    SciTech Connect

    Simmons, J.A.; Weckwerth, M.V.; Baca, W.E.

    1996-03-01

    Three novel fabrication technologies are presented which greatly increase the tools available for the realization of nano-electronic devices. First, a sub-micron area post structure descending from a metallic airbridge allows gating of regions as small as 0.1 {mu}m in diameter. This has enabled the study of such quantum phenomena as coupling of parallel quantum point contacts, and electron focusing around a tunable quantum antidot. We also describe two new techniques for backgating multiquantum well structures with submicron lateral resolution. These techniques enable separate ohmic contacts to individual quantum wells spaced as closely as 100 {Angstrom}, and thus allow the fabrication of novel quantum tunneling devices. The first technique uses regrowth over a patterned ion-implanted substrate. The second involves a novel epoxy-bond-and-stop-etch (EBASE) processing scheme, whereby the original substrate is etched away and the backside then patterned using conventional methods.

  4. Fabrication of infrared antennas using electron-beam lithography

    NASA Astrophysics Data System (ADS)

    Gritz, Michael A.; Gonzalez, Francisco J.; Boreman, Glenn D.

    2003-01-01

    The methods of fabricating infrared antennas using electron beam lithography will be investigated. For this purpose, a process using a bi-layer lift off process and a single layer of resist has been developed. The bi-layer lift off process used allowed for antenna arm resolution of 200nm. The single layer resist process enhanced the resolution of the antenna arms to 90nm by using a Chlorine based reactive ion etcher with Chrome as an etch mask. An alignment scheme using a set of global and local marks allowed for an overlay accuracy of 25nm. An improved process was developed to further improve device yield and uniformity of the infrared detectors by sputtering the bolometer and using an oxygen descum to remove residual resist between antenna and bolometer. Two separate methods of fabrication of air-bridge microstrip antenna-coupled microbolometers using both a critical point dryer and an isotropic reactive ion etcher will also be introduced.

  5. Oscillation up to 1.92 THz in resonant tunneling diode by reduced conduction loss

    NASA Astrophysics Data System (ADS)

    Maekawa, Takeru; Kanaya, Hidetoshi; Suzuki, Safumi; Asada, Masahiro

    2016-02-01

    A large increase in oscillation frequency was achieved in resonant-tunneling-diode (RTD) terahertz oscillators by reducing the conduction loss. An n+-InGaAs layer under the air-bridge electrode connected to the RTD was observed to cause a large conduction loss for high-frequency current due to the skin effect. By introducing a new fabrication process removing the InGaAs layer, we obtained 1.92-THz oscillation, which extended the highest frequency of room-temperature electronic single oscillators. Theoretical calculations reasonably agreed with the experiment, and an oscillation above 2 THz is further expected with an improved structure of the slot antenna used as a resonator and radiator.

  6. Fano Resonance in GaAs 2D Photonic Crystal Nanocavities

    SciTech Connect

    Valentim, P. T.; Guimaraes, P.S. S.; Luxmoore, I. J.; Szymanski, D.; Whittaker, D. M.; Fox, A. M.; Skolnick, M. S.; Vasco, J. P.; Vinck-Posada, H.

    2011-12-23

    We report the results of polarization resolved reflectivity experiments in GaAs air-bridge photonic crystals with L3 cavities. We show that the fundamental L3 cavity mode changes, in a controlled way, from a Lorentzian symmetrical lineshape to an asymmetrical form when the linear polarization of the incident light is rotated in the plane of the crystal. The different lineshapes are well fitted by the Fano asymmetric equation, implying that a Fano resonance is present in the reflectivity. We use the scattering matrix method to model the Fano interference between a localized discrete state (the cavity fundamental mode) and a background of continuum states (the light reflected from the crystal slab in the vicinity of the cavity) with very good agreement with the experimental data.

  7. Responsivity improvements for a vanadium oxide microbolometer using subwavelength resonant absorbers

    NASA Astrophysics Data System (ADS)

    Smith, Evan M.; Nath, Janardan; Ginn, James; Peale, Robert E.; Shelton, David

    2016-05-01

    Subwavelength resonant structures designed for long-wave infrared (LWIR) absorption have been integrated with a standard vanadium-oxide microbolometer. Dispersion of the dielectric refractive index provides for multiple overlapping resonances that span the 8-12 μm LWIR wavelength band, a broader range than can be achieved using the usual quarter-wave resonant cavity engineered into the air-bridge structures. Experimental measurements show a 49% increase in responsivity for LWIR and a 71% increase across a full waveband as compared to a similar device designed for only LWIR absorption, using a 300°C blackbody at 35 Hz chopping rate. Increased thermal time constant due to additional mass is shown to lessen this enhancement at higher chopping rates.

  8. Uniplanar circularly polarized slot-ring antenna architectures

    NASA Astrophysics Data System (ADS)

    Fries, Matthias K.; Vahldieck, Rüdiger

    2002-04-01

    This paper presents a novel printed uniplanar antenna architecture for circular polarization. The structure consists of a single-fed slot-ring antenna with asymmetrically placed perturbations. The influence of different kinds of perturbations and substrates on the size of the antenna, its impedance bandwidth, and its axial ratio bandwidth is investigated. Various feed circuits based on coplanar waveguides (CPWs), coaxial line, and microstrip are investigated as well. Low-cost applications such as tagging antennas at 2.45 GHz are tested in combination with a coaxial line and CPW feed circuit. It was found that antennas achieving an impedance bandwidth over 60% and an axial ratio bandwidth up to 15% can be realized without the need of airbridges and rf-substrates.

  9. Operation of an InAs quantum-dot embedded GaAs photonic crystal slab waveguide laser by using two-photon pumping for photonics integrated circuits

    NASA Astrophysics Data System (ADS)

    Oda, H.; Yamanaka, A.; Ozaki, N.; Ikeda, N.; Sugimoto, Y.

    2016-06-01

    The development of small sized laser operating above room temperature is important in the realization of optical integrated circuits. Recently, micro-lasers consisting of photonic crystals (PhCs) and whispering gallery mode cavities have been demonstrated. Optically pumped laser devices could be easily designed using photonic crystal-slab waveguides (PhC-WGs) with an air-bridge type structure. In this study, we observe lasing at 1.3μm from two-photon pumped InAs-quantum-dots embedded GaAs PhC-WGs above room temperature. This type of compact laser shows promise as a new light source in ultra-compact photonics integrated circuits.

  10. Design and fabrication of one-dimensional and two- dimensional photonic bandgap devices

    NASA Astrophysics Data System (ADS)

    Lim, Kuo-Yi

    1999-10-01

    One-dimensional and two-dimensional photonic bandgap devices have been designed and fabricated using III-V compound semiconductors. The one-dimensional photonic bandgap devices consist of monorail and air-bridge waveguide microcavities, while the two-dimensional photonic bandgap devices consist of light-emitting devices with enhanced extraction efficiency. Fabrication techniques such as gas source molecular beam epitaxy, direct-write electron-beam lithography, reactive ion etching and thermal oxidation of AlxGa1- xAs have been employed. The III-V thermal oxide, in particular, is used as an index confinement material, as a sacrificial material for micromechanical fabrication of the air-bridge microcavity, and in the realization of a wide-bandwidth distributed Bragg reflector. The one-dimensional photonic bandgap waveguide microcavities have been designed to operate in the wavelength regimes of 4.5 m m and 1.55 m m. The devices designed to operate in the 1.55 m m wavelength regime have been optically characterized. The transmission spectra exhibit resonances at around 1.55 m m and cavity quality factors (Q's) ranging from 136 to 334. The resonant modal volume is calculated to be about 0.056 m m3. Tunability in the resonance wavelengths has also been demonstrated by changing the size of the defect in the one-dimensional photonic crystal. The two-dimensional photonic bandgap light-emitting device consists of a In0.51Ga0.49P/In0.2Ga0.8As/In 0.51Ga0.49P quantum well emitting at 980nm with a triangular photonic lattice of holes in the top cladding layer of the quantum well. The photonic crystal prohibits the propagation of guided modes in the semiconductor, thus enhancing the extraction of light vertical to the light-emitting device. A wide-bandwidth GaAs/AlxOy distributed Bragg reflector mirror under the quantum well structure further enhances the extraction of light from the devices. The extraction efficiency of the two-dimensional photonic bandgap light-emitting device

  11. An AlGaN/GaN HEMT with enhanced breakdown and a near-zero breakdown voltage temperature coefficient

    NASA Astrophysics Data System (ADS)

    Xie, Gang; Tang, Cen; Wang, Tao; Guo, Qing; Zhang, Bo; Sheng, Kuang; Wai, Tung Ng

    2013-02-01

    An AlGaN/GaN high-electron mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is experimentally verified. The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain. When compared to a similar size HEMT device with a conventional field plate (CFP) structure, the AFP not only minimizes the parasitic gate to source capacitance, but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm, three times higher forward blocking voltage of 375 V was obtained at VGS = -5 V. In contrast, a similar sized HEMT with a CFP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. Moreover, a temperature coefficient of 0 V/K for the breakdown voltage is observed. However, devices without a field plate (no FP) and with an optimized conventional field plate (CFP) exhibit breakdown voltage temperature coefficients of -0.113 V/K and -0.065 V/K, respectively.

  12. Waveguide Transition for Submillimeter-Wave MMICs

    NASA Technical Reports Server (NTRS)

    Leong, Kevin M.; Deal, William R.; Radisic, Vesna; Mei, Xiaobing; Uyeda, Jansen; Lai, Richard; Fung, King Man; Gaier, Todd C.

    2009-01-01

    An integrated waveguide-to-MMIC (monolithic microwave integrated circuit) chip operating in the 300-GHz range is designed to operate well on high-permittivity semiconductor substrates typical for an MMIC amplifier, and allows a wider MMIC substrate to be used, enabling integration with larger MMICs (power amplifiers). The waveguide-to- CBCPW (conductor-backed coplanar waveguide) transition topology is based on an integrated dipole placed in the E-plane of the waveguide module. It demonstrates low loss and good impedance matching. Measurement and simulation demonstrate that the loss of the transition and waveguide loss is less than 1-dB over a 340-to-380-GHz bandwidth. A transition is inserted along the propagation direction of the waveguide. This transition uses a planar dipole aligned with the maximum E-field of the TE10 waveguide mode as an inter face between the waveguide and the MMIC. Mode conversion between the coplanar striplines (CPS) that feed the dipole and the CBCPW transmission line is accomplished using a simple air-bridge structure. The bottom side ground plane is truncated at the same reference as the top-side ground plane, leaving the end of the MMIC suspended in air.

  13. InGaAs PIN photodiodes on semi-insulating InP substrates with bandwidth exceeding 14 GHz

    NASA Astrophysics Data System (ADS)

    Wen-Jeng Ho; Ting-Arn Dai; Zuon-Ming Chuang; Wei Lin; Yuan-Kuang Tu; Meng-Chyi Wu

    1995-07-01

    The top-illuminated InGaAs PIN photodiodes have been fabricated from materials grown by metalorganic vapor phase epitaxy. Using the planar air-bridge approach and the selective etching technique, it can eliminate the significant bondpad capacitance which is present in conventional PIN photodiodes on conducting substrates. Besides, a self-aligned lift-off process is used for the n-contact recess and metallization. The anti-reflection coating devices have responsivity of 0.79 and 0.78 A/W at 1.3 and 1.55 μm, respectively. The fabricated devices with 30 μm photosensitive diameter have a very low dark current below 0.2 nA and low capacitance of 143 fF at -5V bias voltage. The 3-dB bandwidth of these devices is in excess of 14.8 GHz which is in good agreement with the calculated minority-carrier transit time through an absorbing layer thickness of 1.85 μm. The device performance reveals that these devices are potentially suitable for the applications in optoelectronic integrated circuits.

  14. CMOS compatible high-Q photonic crystal nanocavity fabricated with photolithography on silicon photonic platform

    PubMed Central

    Ooka, Yuta; Tetsumoto, Tomohiro; Fushimi, Akihiro; Yoshiki, Wataru; Tanabe, Takasumi

    2015-01-01

    Progress on the fabrication of ultrahigh-Q photonic-crystal nanocavities (PhC-NCs) has revealed the prospect for new applications including silicon Raman lasers that require a strong confinement of light. Among various PhC-NCs, the highest Q has been recorded with silicon. On the other hand, microcavity is one of the basic building blocks in silicon photonics. However, the fusion between PhC-NCs and silicon photonics has yet to be exploited, since PhC-NCs are usually fabricated with electron-beam lithography and require an air-bridge structure. Here we show that a 2D-PhC-NC fabricated with deep-UV photolithography on a silica-clad silicon-on-insulator (SOI) structure will exhibit a high-Q of 2.2 × 105 with a mode-volume of ~1.7(λ/n)3. This is the highest Q demonstrated with photolithography. We also show that this device exhibits an efficient thermal diffusion and enables high-speed switching. The demonstration of the photolithographic fabrication of high-Q silica-clad PhC-NCs will open possibility for mass-manufacturing and boost the fusion between silicon photonics and CMOS devices. PMID:26086849

  15. A reusable robust radio frequency biosensor using microwave resonator by integrated passive device technology for quantitative detection of glucose level.

    PubMed

    Kim, N Y; Dhakal, R; Adhikari, K K; Kim, E S; Wang, C

    2015-05-15

    A reusable robust radio frequency (RF) biosensor with a rectangular meandered line (RML) resonator on a gallium arsenide substrate by integrated passive device (IPD) technology was designed, fabricated and tested to enable the real-time identification of the glucose level in human serum. The air-bridge structure fabricated by an IPD technology was applied to the RML resonator to improve its sensitivity by increasing the magnitude of the return loss (S21). The resonance behaviour, based on S21 characteristics of the biosensor, was analysed at 9.20 GHz with human serum containing different glucose concentration ranging from 148-268 mg dl(-1), 105-225 mg dl(-1) and at a deionised (D) water glucose concentration in the range of 25- 500 mg dl(-1) for seven different samples. A calibration analysis was performed for the human serum from two different subjects and for D-glucose at a response time of 60 s; the reproducibility, the minimum shift in resonance frequency and the long-term stability of the signal were investigated. The feature characteristics based on the resonance concept after the use of serum as an analyte are modelled as an inductor, capacitor and resistor. The findings support the development of resonance-based sensing with an excellent sensitivity of 1.08 MHz per 1 mg dl(-1), a detection limit of 8.01 mg dl(-1), and a limit of quantisation of 24.30 mg dl(-1). PMID:25459060

  16. Surface passivation of a photonic crystal band-edge laser by atomic layer deposition of SiO2 and its application for biosensing

    NASA Astrophysics Data System (ADS)

    Cha, Hyungrae; Lee, Jeongkug; Jordan, Luke R.; Lee, Si Hoon; Oh, Sang-Hyun; Kim, Hyo Jin; Park, Juhun; Hong, Seunghun; Jeon, Heonsu

    2015-02-01

    We report on the conformal surface passivation of photonic crystal (PC) laser devices with an ultrathin dielectric layer. Air-bridge-type Γ-point band-edge lasers (BELs) are fabricated by forming a honeycomb lattice two-dimensional PC structure into an InGaAsP multiple-quantum-well epilayer. Atomic layer deposition (ALD) is employed for conformal deposition of a few-nanometer-thick SiO2 layer over the entire device surface, not only on the top and bottom surfaces of the air-bridge membrane but also on the air-hole sidewalls. Despite its extreme thinness, the ALD passivation layer is found to protect the InGaAsP BEL devices from harsh chemicals. In addition, the ALD-SiO2 is compatible with the silane-based surface chemistry, which allows us to use ALD-passivated BEL devices as label-free biosensors. The standard streptavidin-biotin interaction shifts the BEL lasing wavelength by ~1 nm for the dipole-like Γ-point band-edge mode. A sharp lasing line (<0.2 nm, full width at half-maximum) and a large refractive index sensitivity (~163 nm per RIU) produce a figure of merit as high as ~800 for our BEL biosensor, which is at least an order of magnitude higher than those of more common biosensors that rely on a broad resonance peak, showing that our nanolaser structures are suitable for highly sensitive biosensor applications.

  17. Structure dependence of oscillation characteristics of resonant-tunneling-diode terahertz oscillators associated with intrinsic and extrinsic delay times

    NASA Astrophysics Data System (ADS)

    Kanaya, Hidetoshi; Maekawa, Takeru; Suzuki, Safumi; Asada, Masahiro

    2015-09-01

    We investigate the effect of intrinsic and extrinsic delay times on the oscillation characteristics of resonant-tunneling-diode (RTD) terahertz oscillators. The intrinsic delay time is composed of the electron dwell time in the resonant tunneling region and the electron transit time in the collector depletion region. We obtain and discuss the structure dependence of these factors in terms of the oscillation frequency and output power measured for RTD oscillators with different quantum-well and collector-spacer thicknesses and different air-bridge widths between the RTD and a slot antenna. The highest oscillation frequency achieved in this experiment is 1.86 THz for the well and spacer thicknesses of 2.5 and 12 nm, respectively, with a 1-µm-wide air bridge. In this structure, the extrinsic delay time (80 fs) estimated from the parasitic elements is more than double the intrinsic delay time (35 fs). It is shown theoretically that an oscillation frequency of over 2 THz is possible upon the reduction in the extrinsic delay time caused by the bulk and spread resistances in RTDs.

  18. CMOS compatible high-Q photonic crystal nanocavity fabricated with photolithography on silicon photonic platform.

    PubMed

    Ooka, Yuta; Tetsumoto, Tomohiro; Fushimi, Akihiro; Yoshiki, Wataru; Tanabe, Takasumi

    2015-01-01

    Progress on the fabrication of ultrahigh-Q photonic-crystal nanocavities (PhC-NCs) has revealed the prospect for new applications including silicon Raman lasers that require a strong confinement of light. Among various PhC-NCs, the highest Q has been recorded with silicon. On the other hand, microcavity is one of the basic building blocks in silicon photonics. However, the fusion between PhC-NCs and silicon photonics has yet to be exploited, since PhC-NCs are usually fabricated with electron-beam lithography and require an air-bridge structure. Here we show that a 2D-PhC-NC fabricated with deep-UV photolithography on a silica-clad silicon-on-insulator (SOI) structure will exhibit a high-Q of 2.2 × 10(5) with a mode-volume of ~ 1.7(λ/n)(3). This is the highest Q demonstrated with photolithography. We also show that this device exhibits an efficient thermal diffusion and enables high-speed switching. The demonstration of the photolithographic fabrication of high-Q silica-clad PhC-NCs will open possibility for mass-manufacturing and boost the fusion between silicon photonics and CMOS devices. PMID:26086849

  19. Gate length variation effect on performance of gate-first self-aligned In₀.₅₃Ga₀.₄₇As MOSFET.

    PubMed

    Mohd Razip Wee, Mohd F; Dehzangi, Arash; Bollaert, Sylvain; Wichmann, Nicolas; Majlis, Burhanuddin Y

    2013-01-01

    A multi-gate n-type In₀.₅₃Ga₀.₄₇As MOSFET is fabricated using gate-first self-aligned method and air-bridge technology. The devices with different gate lengths were fabricated with the Al2O3 oxide layer with the thickness of 8 nm. In this letter, impact of gate length variation on device parameter such as threshold voltage, high and low voltage transconductance, subthreshold swing and off current are investigated at room temperature. Scaling the gate length revealed good enhancement in all investigated parameters but the negative shift in threshold voltage was observed for shorter gate lengths. The high drain current of 1.13 A/mm and maximum extrinsic transconductance of 678 mS/mm with the field effect mobility of 364 cm(2)/Vs are achieved for the gate length and width of 0.2 µm and 30 µm, respectively. The source/drain overlap length for the device is approximately extracted about 51 nm with the leakage current in order of 10(-8) A. The results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared. PMID:24367548

  20. Gate Length Variation Effect on Performance of Gate-First Self-Aligned In0.53Ga0.47As MOSFET

    PubMed Central

    Mohd Razip Wee, Mohd F.; Dehzangi, Arash; Bollaert, Sylvain; Wichmann, Nicolas; Majlis, Burhanuddin Y.

    2013-01-01

    A multi-gate n-type In0.53Ga0.47As MOSFET is fabricated using gate-first self-aligned method and air-bridge technology. The devices with different gate lengths were fabricated with the Al2O3 oxide layer with the thickness of 8 nm. In this letter, impact of gate length variation on device parameter such as threshold voltage, high and low voltage transconductance, subthreshold swing and off current are investigated at room temperature. Scaling the gate length revealed good enhancement in all investigated parameters but the negative shift in threshold voltage was observed for shorter gate lengths. The high drain current of 1.13 A/mm and maximum extrinsic transconductance of 678 mS/mm with the field effect mobility of 364 cm2/Vs are achieved for the gate length and width of 0.2 µm and 30µm, respectively. The source/drain overlap length for the device is approximately extracted about 51 nm with the leakage current in order of 10−8 A. The results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared. PMID:24367548

  1. Multiband terahertz quasi-optical balanced hot-electron mixers based on dual-polarization sinuous antennas

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenguo; Rahman, Syed M.; Ruggiero, Steven T.; Fay, Patrick; Liu, Lei

    2014-05-01

    Receivers based on superconducting Hot-Electron Bolometers (HEBs) are widely used for terahertz (THz) sensing owing to their advantages of high sensitivity, low noise, and low LO power requirement. Balanced HEB mixers are superior to single-element ones since the thermal noise and AM noise from the LO injection can be effectively suppressed. Although a 1.3 THz balanced waveguide HEB mixer has been reported, waveguide mixer configurations offer relatively narrow RF bandwidths. We report on the development, fabrication and characterization of a THz quasioptical balanced superconducting HEB mixer utilizing a dual-polarization sinuous antenna that can potentially achieve both multiband operation and ultra-high sensitivity. In the balanced mixer configuration, a lens-coupled four-arm sinuous antenna was designed for operation from 0.2-1.0 THz with a nearly frequency-independent embedding impedance of ~106 Ω. Two identical superconducting niobium HEB devices have been integrated at the antenna feedpoints, connecting each opposing pair of antenna arms to form a balanced mixer configuration. An air-bridge was also fabricated to separate the two mixer branches. The HEB devices were fabricated from 10 nm thick niobium film sputtered on semi-insulating silicon substrates. Each HEB device has dimensions of 80 nm × 240 nm (3 squares) for approaching a resistance of 105 Ω for impedance matching. Mixer properties including antenna radiation patterns, broadband operation and polarization isolation have been characterized. Finally, in order to achieve multiband mixer operation, electronically reconfigurable THz quasi-optical mesh filters are needed. Frequency-tunable antenna elements using Schottky varactor diodes suitable for the above applications have been designed, simulated and demonstrated at Gband (140-220 GHz) showing 50 GHz tuning range.

  2. Optimization of kinetic inductance detectors for millimeter and submillimeter wave detection

    NASA Astrophysics Data System (ADS)

    Coiffard, G.; Schuster, K. F.; Monfardini, A.; Adane, A.; Barbier, B.; Boucher, C.; Calvo, M.; Goupy, J.; Leclercq, S.; Pignard, S.

    2014-07-01

    We present the latest improvements of lumped element kinetic inductance detectors (LEKIDs) for the NIKA camera at the 30-m telescope of IRAM at Pico Veleta (Spain) [1]. LEKIDs are direct absorption detectors for millimeter wavelength and represent a particularly efficient concept of planar array continuum detectors for the millimeter and submillimeter wavelength range. To improve the detector radiation coupling over a wider frequency range, a combination of backplane reflector and a supplementary layer of dielectric between silicon substrate and backplane has been successfully explored. To this end we apply deep silicon etching to the substrate in order to decrease its effective dielectric constant in an intermediate layer. In the first generation of LEKIDs array, the response is disturbed by the presence of slot-modes in the frequency multiplexing coplanar feed/readout line, an effect which was reduced when applying wire bonding across the readout line. Superconducting air-bridges can be integrated into the array fabrication process. The suppression of slot-modes also reduces undesired cross-talk between pixels. Our current KID detectors are made of very thin aluminum films, but with a thickness of less than 20 nm we have reached some limitations concerning the layout and material processing. Following the results from Leduc et al. [2], we developed non-stoichiometric titanium nitride (TiN) at IRAM as an alternative material. We focus on the work done to achieve reproducible and homogenous films with the required transition temperature for mm-wave detection. We present characterization techniques that allow room temperature measurements to be correlated to the transition temperature of TiNx and first measurements on a test sample.

  3. Surface passivation of a photonic crystal band-edge laser by atomic layer deposition of SiO2 and its application for biosensing.

    PubMed

    Cha, Hyungrae; Lee, Jeongkug; Jordan, Luke R; Lee, Si Hoon; Oh, Sang-Hyun; Kim, Hyo Jin; Park, Juhun; Hong, Seunghun; Jeon, Heonsu

    2015-02-28

    We report on the conformal surface passivation of photonic crystal (PC) laser devices with an ultrathin dielectric layer. Air-bridge-type Γ-point band-edge lasers (BELs) are fabricated by forming a honeycomb lattice two-dimensional PC structure into an InGaAsP multiple-quantum-well epilayer. Atomic layer deposition (ALD) is employed for conformal deposition of a few-nanometer-thick SiO2 layer over the entire device surface, not only on the top and bottom surfaces of the air-bridge membrane but also on the air-hole sidewalls. Despite its extreme thinness, the ALD passivation layer is found to protect the InGaAsP BEL devices from harsh chemicals. In addition, the ALD-SiO2 is compatible with the silane-based surface chemistry, which allows us to use ALD-passivated BEL devices as label-free biosensors. The standard streptavidin-biotin interaction shifts the BEL lasing wavelength by ∼1 nm for the dipole-like Γ-point band-edge mode. A sharp lasing line (<0.2 nm, full width at half-maximum) and a large refractive index sensitivity (∼163 nm per RIU) produce a figure of merit as high as ∼800 for our BEL biosensor, which is at least an order of magnitude higher than those of more common biosensors that rely on a broad resonance peak, showing that our nanolaser structures are suitable for highly sensitive biosensor applications. PMID:25631610

  4. Inductively coupled plasma etching of GaAs low loss waveguides for a traveling waveguide polarization converter, using chlorine chemistry

    NASA Astrophysics Data System (ADS)

    Lu, J.; Meng, X.; Springthorpe, A. J.; Shepherd, F. R.; Poirier, M.

    2004-05-01

    A traveling waveguide polarization converter [M. Poirier et al.] has been developed, which involves long, low loss, weakly confined waveguides etched in GaAs (epitaxially grown by molecular beam epitaxy), with electroplated ``T electrodes'' distributed along the etched floor adjacent to the ridge walls, and airbridge interconnect metallization. This article describes the development of the waveguide fabrication, based on inductively coupled plasma (ICP) etching of GaAs using Cl2 chemistry; the special processes required to fabricate the electrodes and metallization [X. Meng et al.], and the device characteristics [M. Poirier et al.], are described elsewhere. The required waveguide has dimensions nominally 4 μm wide and 2.1 μm deep, with dimensional tolerances ~0.1 μm across the wafer and wafer to wafer. A vertical etch profile with very smooth sidewalls and floors is required to enable the plated metal electrodes to be fabricated within 0.1 μm of the ridge. The ridges were fabricated using Cl2 ICP etching and a photoresist mask patterned with an I-line stepper; He backside cooling, combined with an electrostatic chuck, was employed to ensure good heat transfer to prevent resist reticulation. The experimental results showed that the ridge profile is very sensitive to ICP power and platen rf power. High ICP power and low platen power tend to result in more isotropic etching, whereas increasing platen power increases the photoresist etch rate, which causes rougher ridge sidewalls. No strong dependence of GaAs etch rate and ridge profile were observed with small changes in process temperature (chuck temperature). However, when the chuck temperature was decreased from 25 to 0 °C, etch uniformity across a 3 in. wafer improved from 6% to 3%. Photoresist and polymer residues present after the ICP etch were removed using a combination of wet and dry processes. .

  5. PAH sorption mechanism and partitioning behavior in lampblack-impacted soils from former oil-gas plant sites.

    PubMed

    Hong, Lei; Ghosh, Upal; Mahajan, Tania; Zare, Richard N; Luthy, Richard G

    2003-08-15

    This study assessed polycyclic aromatic hydrocarbon (PAH) association and aqueous partitioning in lampblack-impacted field soils from five sites in California that formerly housed oil-gas process operations. Lampblack is the solid residue resulting from the decomposition of crude oil at high temperatures in the gas-making operation and is coated or impregnated with oil gasification byproducts, among which PAHs are the compounds of the greatest regulatory concern. A suite of complementary measurements investigated the character of lampblack particles and PAH location and the associated effects on PAH partitioning between lampblack and water. PAH analyses on both whole samples and density-separated components demonstrated that 81-100% of PAHs in the lampblack-impacted soils was associated with lampblack particles. FTIR, 13C NMR, and SEM analyses showed that oil-gas lampblack solids comprise primarily aromatic carbon with soot-like structures. A free-phase aromatic oil may be present in some of the lampblack soils containing high PAH concentrations. Comparable long-term aqueous partitioning measurements were obtained with an air-bridge technique and with a centrifugation/alum flocculation procedure. Large solid/water partition coefficient (Kd) values were observed in samples exhibiting lower PAH and oil levels, whereas smaller Kd values were measured in lampblack samples containing high PAH levels. The former result is in agreement with an oil-soot partitioning model, and the latter is in agreement with a coal tar-water partitioning model. Lampblack containing high PAH levels appears to exhaust the sorption capacity of the soot-carbon, creating a free aromatic oil phase that exhibits partitioning behavior similar to PAHs in coal tar. This study improves mechanistic understanding of PAH sorption on aged lampblack residuals at former oil-gas sites and provides a framework for mechanistic assessment of PAH leaching potential and risk from such site materials. PMID

  6. Integrated diode circuits for greater than 1 THz

    NASA Astrophysics Data System (ADS)

    Schoenthal, Gerhard Siegbert

    The terahertz frequency band, spanning from roughly 100 GHz to 10 THz, forms the transition from electronics to photonics. This band is often referred to as the "terahertz technology gap" because it lacks typical microwave and optical components. The deficit of terahertz devices makes it difficult to conduct important scientific measurements that are exclusive to this band in fields such as radio astronomy and chemical spectroscopy. In addition, a number of scientific, military and commercial applications will become more practical when a suitable terahertz technology is developed. UVa's Applied Electrophysics Laboratory has extended non-linear microwave diode technology into the terahertz region. Initial success was achieved with whisker-contacted diodes and then discrete planar Schottky diodes soldered onto quartz circuits. Work at UVa and the Jet Propulsion Laboratory succeeded in integrating this diode technology onto low dielectric substrates, thereby producing more practical components with greater yield and improved performance. However, the development of circuit integration technologies for greater than 1 THz and the development of broadly tunable sources of terahertz power remain as major research goals. Meeting these critical needs is the primary motivation for this research. To achieve this goal and demonstrate a useful prototype for one of our sponsors, this research project has focused on the development of a Sideband Generator at 1.6 THz. This component allows use of a fixed narrow band source as a tunable power source for terahertz spectroscopy and compact range radar. To prove the new fabrication and circuit technologies, initial devices were fabricated and tested at 200 and 600 GHz. These circuits included non-ohmic cathodes, air-bridged fingers, oxideless anode formation, and improved quartz integration processes. The excellent performance of these components validated these new concepts. The prototype process was then further optimized to

  7. Room temperature strong light-matter coupling in 3D THz meta-atoms (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Paulillo, Bruno; Manceau, Jean-Michel; Li, Lianhe; Linfield, Edmund; Colombelli, Raffaele

    2016-04-01

    We demonstrate strong light-matter coupling at room temperature in the terahertz (THz) spectral region using 3D meta-atoms with extremely sub-wavelength volumes. Using an air-bridge fabrication scheme, we have implemented sub-wavelength 3D THz micro-resonators that rely on suspended loop antennas connected to semiconductor-filled patch cavities. We have experimentally shown that they possess the functionalities of lumped LC resonators: their frequency response can be adjusted by independently tuning the inductance associated the antenna element or the capacitance provided by the metal-semiconductor-metal cavity. Moreover, the radiation coupling and efficiency can be engineered acting on the design of the loop antenna, similarly to conventional RF antennas. Here we take advantage of this rich playground in the context of cavity electrodynamics/intersubband polaritonics. In the strong light-matter coupling regime, a cavity and a two-level system exchange energy coherently at a characteristic rate called the vacuum Rabi frequency ΩR which is dominant with respect to all other loss mechanisms involved. The signature, in the frequency domain, is the appearance of a splitting between the bare cavity and material system resonances: the new states are called upper and a lower polariton branches. So far, most experimental demonstrations of strong light-matter interaction between an intersubband transition and a deeply sub-wavelength mode in the THz or mid-infrared ranges rely on wavelength-scale or larger resonators such as photonic crystals, diffractive gratings, dielectric micro-cavities or patch cavities. Lately, planar metamaterials have been used to enhance the light-matter interaction and strongly reduce the interaction volume by engineering the electric and magnetic resonances of the individual subwavelength constituents. In this contribution we provide evidence of strong coupling between a THz intersubband transition and an extremely sub-wavelength mode (≈λ/10