High power and single mode quantum cascade lasers.

PubMed

Bismuto, Alfredo; Bidaux, Yves; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Rochat, Michel; Muller, Antoine; Bonzon, Christopher; Faist, Jerome

2016-05-16

We present a single mode quantum cascade laser with nearly 1 W optical power. A buried distributed feedback reflector is used on the back section for wavelength selection. The laser is 6 mm long, 3.5 μm wide, mounted episide-up and the laser facets are left uncoated. Laser emission is centered at 4.68 μm. Single-mode operation with a side mode suppression ratio of more than 30 dB is obtained in whole range of operation. Farfield measurements prove a symmetric, single transverse-mode emission in TM00-mode with typical divergences of 41° and 33° in the vertical and horizontal direction respectively. This work shows the potential for simple fabrication of high power lasers compatible with standard DFB processing.

Studies of single-mode injection lasers and of quaternary materials. Volume 1: Single-mode constricted double-heterojunction AlGaAs diode lasers

NASA Technical Reports Server (NTRS)

Botez, D.

1982-01-01

Constricted double-heterojunction (CDH) lasers are presented as the class of single-mode nonplanar-substrate devices for which the lasing cavity is on the least resistive electrical path between the contact and the substrate. Various types of CDH structures are considered under three general topics: liquid-phase epitaxy over channeled substrates, lateral mode control, and current control in nonplanar-substrate devices. Ridge-guide CDH lasers have positive-index lateral-mode confinement and provide: single-mode CW operation to 7 mW/facet at room temperature and to 3 mW/facet at 150 C; light-current characteristics with second-harmonic distortion as low as -57 dB below the fundamental level; threshold-current temperature coefficients, as high as 375 C (pulsed) and 310 C (CW); constant external differential quantum efficiency to 100 C; and lasing operation to 170 C CW and 280 C pulsed. Semileakyguide CDH lasers have an asymmetric leaky cavity for lateral-mode confinement and provide single-mode operation to 15 to 20 mW/facet CW and to 50 mW/facet at 50% duty cycle. Modulation characteristics and preliminary reliability data are discussed.

Characterization of pseudosingle bunch kick-and-cancel operational mode

DOE PAGES

Sun, C.; Robin, D. S.; Steier, C.; ...

2015-12-18

Pseudosingle-bunch kick-and-cancel (PSB-KAC) is a new operational mode at the Advanced Light Source of Lawrence Berkeley National Laboratory that provides full timing and repetition rate control for single x-ray pulse users while being fully transparent to other users of synchrotron radiation light. In this operational mode, a single electron bunch is periodically displaced from a main bunch train by a fast kicker magnet with a user-on-demand repetition rate, creating a single x-ray pulse to be matched to a typical laser excitation pulse rate. This operational mode can significantly improve the signal to noise ratio of single x-ray pulse experiments andmore » drastically reduce dose-induced sample damage rate. It greatly expands the capabilities of synchrotron light sources to carry out dynamics and time-of-flight experiments. In this paper, we carry out extensive characterizations of this PSB-KAC mode both numerically and experimentally. This includes the working principle of this mode, resonance conditions and beam stability, experimental setups, and diagnostic tools and measurements.« less

GaSb-based single-mode distributed feedback lasers for sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gupta, James A.; Bezinger, Andrew; Lapointe, Jean; Poitras, Daniel; Aers, Geof C.

2017-02-01

GaSb-based tunable single-mode diode lasers can enable rapid, highly-selective and highly-sensitive absorption spectroscopy systems for gas sensing. In this work, single-mode distributed feedback (DFB) laser diodes were developed for the detection of various trace gases in the 2-3.3um range, including CO2, CO, HF, H2S, H2O and CH4. The lasers were fabricated using an index-coupled grating process without epitaxial regrowth, making the process significantly less expensive than conventional DFB fabrication. The devices are based on InGaAsSb/AlGaAsSb separate confinement heterostructures grown on GaSb by molecular beam epitaxy. DFB lasers were produced using a two step etch process. Narrow ridge waveguides were first defined by optical lithography and etched into the semiconductor. Lateral gratings were then defined on both sides of the ridge using electron-beam lithography and etched to produce the index-grating. Effective index modeling was used to optimize the ridge width, etch depths and the grating pitch to ensure single-lateral-mode operation and adequate coupling strength. The effective index method was further used to simulate the DFB laser emission spectrum, based on a transfer matrix model for light transmission through the periodic structure. The fabricated lasers exhibit single-mode operation which is tunable through the absorption features of the various target gases by adjustment of the drive current. In addition to the established open-path sensing applications, these devices have great potential for optoelectronic integrated gas sensors, making use of integrated photodetectors and possibly on-chip Si photonics waveguide structures.

Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

NASA Technical Reports Server (NTRS)

Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

2009-01-01

Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

NASA Technical Reports Server (NTRS)

Kumar, Sushil; Williams, Benjamin S.; Qin, Qi; Lee, Alan W. M.; Hu, Qing; Reno, John L.

2007-01-01

Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

Long distance transmission in few-mode fibers.

PubMed

Yaman, Fatih; Bai, Neng; Zhu, Benyuan; Wang, Ting; Li, Guifang

2010-06-07

Using multimode fibers for long-haul transmission is proposed and demonstrated experimentally. In particular few-mode fibers (FMFs) are demonstrated as a good compromise since they are sufficiently resistant to mode coupling compared to standard multimode fibers but they still can have large core diameters compared to single-mode fibers. As a result these fibers can have significantly less nonlinearity and at the same time they can have the same performance as single-mode fibers in terms of dispersion and loss. In the absence of mode coupling it is possible to use these fibers in the single-mode operation where all the data is carried in only one of the spatial modes throughout the fiber. It is shown experimentally that the single-mode operation is achieved simply by splicing single-mode fibers to both ends of a 35-km-long dual-mode fiber at 1310 nm. After 35 km of transmission, no modal dispersion or excess loss was observed. Finally the same fiber is placed in a recirculating loop and 3 WDM channels each carrying 6 Gb/s BPSK data were transmitted through 1050 km of the few-mode fiber without modal dispersion.

Biomedical ultrasonoscope

NASA Technical Reports Server (NTRS)

Lee, R. D. (Inventor)

1976-01-01

An instrument with a single ultrasonic transducer probe and a linear array of transducer probes permitting three operator modes is described. An 'A' and an 'M' mode scanner were combined with a 'C' mode scanner and a single receiver is used. The 'C' scanner mode enables two-dimensional cross sections of the viewed organ. Video-produced markers enable measurement of the dimensions of the heart. COS/MOS integrated logic circuit components are used to minimize power consumption and permit battery operation.

Effect of ripple taper on band-gap overlap in a coaxial Bragg structure operating at terahertz frequency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding Xueyong; Li Hongfan; Lv Zhensu

Based on the mode-coupling method, numerical analysis is presented to demonstrate the influence of ripple taper on band-gap overlap in a coaxial Bragg structure operating at terahertz frequency. Results show that the interval between the band-gaps of the competing mode and the desired working mode is narrowed by use of positive-taper ripples, but is expanded if negative-taper ripples are employed, and the influence of the negative-taper ripples is obviously more advantageous than the positive-taper ripples; the band-gap overlap of modes can be efficiently separated by use of negative-taper ripples. The residual side-lobes of the frequency response in a coaxial Braggmore » structure with ripple taper also can be effectively suppressed by employing the windowing-function technique. These peculiarities provide potential advantage in constructing a coaxial Bragg cavity with high quality factor for single higher-order-mode operation of a high-power free-electron maser in the terahertz frequency range.« less

Static internal performance of single expansion-ramp nozzles with thrust vectoring and reversing

NASA Technical Reports Server (NTRS)

Re, R. J.; Berrier, B. L.

1982-01-01

The effects of geometric design parameters on the internal performance of nonaxisymmetric single expansion-ramp nozzles were investigated at nozzle pressure ratios up to approximately 10. Forward-flight (cruise), vectored-thrust, and reversed-thrust nozzle operating modes were investigated.

Tunable Er-doped fiber ring laser with single longitudinal mode operation based on Rayleigh backscattering in single mode fiber.

PubMed

Yin, Guolu; Saxena, Bhavaye; Bao, Xiaoyi

2011-12-19

A tunable and single longitudinal mode Er-doped fiber ring laser (SLM-EDFRL) is proposed and demonstrated based on Rayleigh backscattering (RBS) in single mode fiber-28e (SMF-28e). Theory and experimental study on formation of SLM from normal multi-mode ring laser is demonstrated. The RBS feedback in 660 m SMF-28e is the key to ensure SLM laser oscillation. This tunable SLM laser can be tuned over 1549.7-1550.18 nm with a linewidth of 2.5-3.0 kHz and a side mode suppression ratio (SMSR) of ~72 dB for electrical signal power. The tuning range is determined by the bandpass filter and gain medium used in the experiment. The laser is able to operate at S+C+L band.

Cutoff-mesa isolated rib optical waveguide for III-V heterostructure photonic integrated circuits

DOEpatents

Vawter, Gregory A.; Smith, Robert E.

1998-01-01

A cutoff mesa rib waveguide provides single-mode performance regardless of any deep etches that might be used for electrical isolation between integrated electrooptic devices. Utilizing a principle of a cutoff slab waveguide with an asymmetrical refractive index profile, single mode operation is achievable with a wide range of rib widths and does not require demanding etch depth tolerances. This new waveguide design eliminates reflection effects, or self-interference, commonly seen when conventional rib waveguides are combined with deep isolation etches and thereby reduces high order mode propagation and crosstalk compared to the conventional rib waveguides.

Cutoff-mesa isolated rib optical waveguide for III-V heterostructure photonic integrated circuits

DOEpatents

Vawter, G.A.; Smith, R.E.

1998-04-28

A cutoff mesa rib waveguide provides single-mode performance regardless of any deep etches that might be used for electrical isolation between integrated electrooptic devices. Utilizing a principle of a cutoff slab waveguide with an asymmetrical refractive index profile, single mode operation is achievable with a wide range of rib widths and does not require demanding etch depth tolerances. This new waveguide design eliminates reflection effects, or self-interference, commonly seen when conventional rib waveguides are combined with deep isolation etches and thereby reduces high order mode propagation and crosstalk compared to the conventional rib waveguides. 7 figs.

Tunable single-longitudinal-mode operation of an injection-locked TEA CO2 laser. [ozone absorption spectroscopy

NASA Technical Reports Server (NTRS)

Megie, G.; Menzies, R. T.

1979-01-01

The tunable single-longitudinal-mode operation of a TEA CO2 laser by an injection technique using a CW waveguide laser as the master oscillator is reported. With the experimental arrangement described, in which the waveguide laser frequency is tuned to correspond to one of the oscillating longitudinal modes of the TEA laser, single-longitudinal-mode operation was achieved with no apparent reduction in the TEA output energy, on various CO2 lines with frequency offsets from the line center as large as 300 MHz. The capability of this technique for high-resolution spectroscopy or atmospheric lidar studies is demonstrated by the recording of the absorption spectrum of a strong ozone line.

Design of dual-mode optical fibres for the FTTH applications

NASA Astrophysics Data System (ADS)

Chen, Ming-Yang; Li, Yu-Rong; Zhang, Yin; Zhu, Yuan-Feng; Zhang, Yong-Kang; Zhou, Jun

2011-01-01

We present in this article a proposal and design for dual-mode optical fibres for fibre-to-the-home applications. High-order modes in the fibre can be effectively suppressed by the connection of the fibre with standard single-mode optical fibres at the two ends of the fibre. The alignment tolerance at the splicing process is presented. In particular, a low bending loss operation with low splice loss is demonstrated using the proposed technique.

Effective squeezing enhancement via measurement-induced non-Gaussian operation and its application to the dense coding scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitagawa, Akira; Takeoka, Masahiro; Sasaki, Masahide

2005-08-15

We study the measurement-induced non-Gaussian operation on the single- and two-mode Gaussian squeezed vacuum states with beam splitters and on-off type photon detectors, with which mixed non-Gaussian states are generally obtained in the conditional process. It is known that the entanglement can be enhanced via this non-Gaussian operation on the two-mode squeezed vacuum state. We show that, in the range of practical squeezing parameters, the conditional outputs are still close to Gaussian states, but their second order variances of quantum fluctuations and correlations are effectively suppressed and enhanced, respectively. To investigate an operational meaning of these states, especially entangled states,more » we also evaluate the quantum dense coding scheme from the viewpoint of the mutual information, and we show that non-Gaussian entangled state can be advantageous compared with the original two-mode squeezed state.« less

1.9 μm square-wave passively Q-witched mode-locked fiber laser.

PubMed

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Wang, Furen; Zhang, Jing; Wang, Chengbo; Jiang, Huilin

2018-05-14

We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.

LP01 to LP11 mode convertor based on side-polished small-core single-mode fiber

NASA Astrophysics Data System (ADS)

Liu, Yan; Li, Yang; Li, Wei-dong

2018-03-01

An all-fiber LP01-LP11 mode convertor based on side-polished small-core single-mode fibers (SMFs) is numerically demonstrated. The linearly polarized incident beam in one arm experiences π shift through a fiber half waveplate, and the side-polished parts merge into an equivalent twin-core fiber (TCF) which spatially shapes the incident LP01 modes to the LP11 mode supported by the step-index few-mode fiber (FMF). Optimum conditions for the highest conversion efficiency are investigated using the beam propagation method (BPM) with an approximate efficiency as high as 96.7%. The proposed scheme can operate within a wide wavelength range from 1.3 μm to1.7 μm with overall conversion efficiency greater than 95%. The effective mode area and coupling loss are also characterized in detail by finite element method (FEM).

Mode Behavior in Ultralarge Ring Lasers

NASA Astrophysics Data System (ADS)

Hurst, Robert B.; Dunn, Robert W.; Schreiber, K. Ulrich; Thirkettle, Robert J.; MacDonald, Graeme K.

2004-04-01

Contrary to expectations based on mode spacing, single-mode operation in very large He-Ne ring lasers may be achieved at intracavity power levels up to ~0.15 times the saturation intensity for the He-Ne transition. Homogeneous line broadening at a high total gas pressure of 4-6 Torr allows a single-peaked gain profile that suppresses closely spaced multiple modes. At startup, decay of initial multiple modes may take tens of seconds. The single remaining mode in each direction persists metastably as the cavity is detuned by many times the mode frequency spacing. A theoretical explanation requires the gain profile to be concave down and to satisfy an inequality related to slope and saturation at the operating frequency. Calculated metastable frequency ranges are greater than 150 MHz at 6 Torr and depend strongly on pressure. Examples of unusual stable mode configurations are shown, with differently numbered modes in the two directions and with multiple modes at a spacing of ~100 MHz.

Mode behavior in ultralarge ring lasers.

PubMed

Hurst, Robert B; Dunn, Robert W; Schreiber, K Ulrich; Thirkettle, Robert J; MacDonald, Graeme K

2004-04-10

Contrary to expectations based on mode spacing, single-mode operation in very large He-Ne ring lasers may be achieved at intracavity power levels up to approximately0.15 times the saturation intensity for the He-Ne transition. Homogeneous line broadening at a high total gas pressure of 4-6 Torr allows a single-peaked gain profile that suppresses closely spaced multiple modes. At startup, decay of initial multiple modes may take tens of seconds. The single remaining mode in each direction persists metastably as the cavity is detuned by many times the mode frequency spacing. A theoretical explanation requires the gain profile to be concave down and to satisfy an inequality related to slope and saturation at the operating frequency. Calculated metastable frequency ranges are > 150 MHz at 6 Torr and depend strongly on pressure. Examples of unusual stable mode configurations are shown, with differently numbered modes in the two directions and with multiple modes at a spacing of approximately 100 MHz.

Dual-color single-mode lasing in axially coupled organic nanowire resonators

PubMed Central

Zhang, Chunhuan; Zou, Chang-Ling; Dong, Haiyun; Yan, Yongli; Yao, Jiannian; Zhao, Yong Sheng

2017-01-01

Miniaturized lasers with multicolor output and high spectral purity are of crucial importance for yielding more compact and more versatile photonic devices. However, multicolor lasers usually operate in multimode, which largely restricts their practical applications due to the lack of an effective mode selection mechanism that is simultaneously applicable to multiple wavebands. We propose a mutual mode selection strategy to realize dual-color single-mode lasing in axially coupled cavities constructed from two distinct organic self-assembled single-crystal nanowires. The unique mode selection mechanism in the heterogeneously coupled nanowires was elucidated experimentally and theoretically. With each individual nanowire functioning as both the laser source and the mode filter for the other nanowire, dual-color single-mode lasing was successfully achieved in the axially coupled heterogeneous nanowire resonators. Furthermore, the heterogeneously coupled resonators provided multiple nanoscale output ports for delivering coherent signals with different colors, which could greatly contribute to increasing the integration level of functional photonic devices. These results advance the fundamental understanding of the lasing modulation in coupled cavity systems and offer a promising route to building multifunctional nanoscale lasers for high-level practical photonic integrations. PMID:28785731

Wide spectral range confocal microscope based on endlessly single-mode fiber.

PubMed

Hubbard, R; Ovchinnikov, Yu B; Hayes, J; Richardson, D J; Fu, Y J; Lin, S D; See, P; Sinclair, A G

2010-08-30

We report an endlessly single mode, fiber-optic confocal microscope, based on a large mode area photonic crystal fiber. The microscope confines a very broad spectral range of excitation and emission wavelengths to a single spatial mode in the fiber. Single-mode operation over an optical octave is feasible. At a magnification of 10 and λ = 900 nm, its resolution was measured to be 1.0 μm (lateral) and 2.5 μm (axial). The microscope's use is demonstrated by imaging single photons emitted by individual InAs quantum dots in a pillar microcavity.

III-Nitride Nanowire Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, Jeremy Benjamin

2014-07-01

In recent years there has been a tremendous interest in nanoscale optoelectronic devices. Among these devices are semiconductor nanowires whose diameters range from 10-100 nm. To date, nanowires have been grown using many semiconducting material systems and have been utilized as light emitting diodes, photodetectors, and solar cells. Nanowires possess a relatively large index contrast relative to their dielectric environment and can be used as lasers. A key gure of merit that allows for nanowire lasing is the relatively high optical con nement factor. In this work, I discuss the optical characterization of 3 types of III-nitride nanowire laser devices.more » Two devices were designed to reduce the number of lasing modes to achieve singlemode operation. The third device implements low-group velocity mode lasing with a photonic crystal constructed of an array of nanowires. Single-mode operation is necessary in any application where high beam quality and single frequency operation is required. III-Nitride nanowire lasers typically operate in a combined multi-longitudinal and multi-transverse mode state. Two schemes are introduced here for controlling the optical modes and achieving single-mode op eration. The rst method involves reducing the diameter of individual nanowires to the cut-o condition, where only one optical mode propagates in the wire. The second method employs distributed feedback (DFB) to achieve single-mode lasing by placing individual GaN nanowires onto substrates with etched gratings. The nanowire-grating substrate acted as a distributed feedback mirror producing single mode operation at 370 nm with a mode suppression ratio (MSR) of 17 dB. The usage of lasers for solid state lighting has the potential to further reduce U.S. lighting energy usage through an increase in emitter e ciency. Advances in nanowire fabrication, speci cally a two-step top-down approach, have allowed for the demonstration of a multi-color array of lasers on a single chip that emit vertically. By tuning the geometrical properties of the individual lasers across the array, each individual nanowire laser produced a di erent emission wavelength yielding a near continuum of laser wavelengths. I successfully fabricated an array of emitters spanning a bandwidth of 60 nm on a single chip. This was achieved in the blue-violet using III-nitride photonic crystal nanowire lasers.« less

Mode control in photonic crystal surface emitting lasers (PCSELs) through in-plane feedback (Conference Presentation)

NASA Astrophysics Data System (ADS)

Taylor, Richard J. E.; Li, Guangrui; Ivanov, Pavlo; Childs, David T. D.; Stevens, Ben J.; Babazadeh, Nasser; Ignatova, Olesya; Hogg, Richard A.

2017-02-01

All-semiconductor photonic crystal surface-emitting lasers (PCSELs) operating in CW mode at room temperature and coherently coupled arrays of these lasers are reviewed. These PCSELs are grown via MOVPE on GaAs substrates and include QW active elements and GaAs/InGaP photonic crystal (PC) layer situated above this active zone. Atoms of triangular shapes have been shown to increase optical power from the PCSEL but are also shown to result in a competition between lasing modes. Simulation shows that the energy splitting of lasing modes is smaller for triangular atoms, than for circles making high power single-mode devices difficult to achieve. In this work we experimentally investigate the effect of lateral optical feedback introduced by a facet cleave along one or two perpendicular PCSEL edges. This cleavage plane is misaligned to the PC resulting in a periodic variation of facet phase along the side of the device. Results confirm that a single cleave selects the lowest threshold 2D lasing mode, resulting in a 20% reduction in threshold current and favours single-mode emission. The addition of a second cleave at right-angles to the first has no significant effect upon threshold current. The virgin device is shown to have a symmetric far-field (1 degree) whilst a single cleave produces a 1 degree divergence perpendicular to cleave and 5 degree parallel to cleave. The second orthogonal cleave results in the far field becoming symmetric again but with a divergence angle of 1 degree indicating that single-mode lasing is supported over a wider area.

Output Power Limitations and Improvements in Passively Mode Locked GaAs/AlGaAs Quantum Well Lasers.

PubMed

Tandoi, Giuseppe; Ironside, Charles N; Marsh, John H; Bryce, A Catrina

2012-03-01

We report a novel approach for increasing the output power in passively mode locked semiconductor lasers. Our approach uses epitaxial structures with an optical trap in the bottom cladding that enlarges the vertical mode size to scale the pulse saturation energy. With this approach we demonstrate a very high peak power of 9.8 W per facet, at a repetition rate of 6.8 GHz and with pulse duration of 0.71 ps. In particular, we compare two GaAs/AlGaAs epilayer designs, a double quantum well design operating at 830 nm and a single quantum well design operating at 795 nm, with vertical mode sizes of 0.5 and 0.75 μm, respectively. We show that a larger mode size not only shifts the mode locking regime of operation towards higher powers, but also produces other improvements in respect of two main failure mechanisms that limit the output power: the catastrophic optical mirror damage and the catastrophic optical saturable absorber damage. For the 830 nm material structure, we also investigate the effect of non-absorbing mirrors on output power and mode locked operation of colliding pulse mode locked lasers.

Output Power Limitations and Improvements in Passively Mode Locked GaAs/AlGaAs Quantum Well Lasers

PubMed Central

Tandoi, Giuseppe; Ironside, Charles N.; Marsh, John H.; Bryce, A. Catrina

2013-01-01

We report a novel approach for increasing the output power in passively mode locked semiconductor lasers. Our approach uses epitaxial structures with an optical trap in the bottom cladding that enlarges the vertical mode size to scale the pulse saturation energy. With this approach we demonstrate a very high peak power of 9.8 W per facet, at a repetition rate of 6.8 GHz and with pulse duration of 0.71 ps. In particular, we compare two GaAs/AlGaAs epilayer designs, a double quantum well design operating at 830 nm and a single quantum well design operating at 795 nm, with vertical mode sizes of 0.5 and 0.75 μm, respectively. We show that a larger mode size not only shifts the mode locking regime of operation towards higher powers, but also produces other improvements in respect of two main failure mechanisms that limit the output power: the catastrophic optical mirror damage and the catastrophic optical saturable absorber damage. For the 830 nm material structure, we also investigate the effect of non-absorbing mirrors on output power and mode locked operation of colliding pulse mode locked lasers. PMID:23843678

Linearly Polarized Single-Frequency Oscillations of Laser-Diode-Pumped Microchip Ceramic Nd:YAG Lasers with Forced Ince-Gaussian Mode Operations

NASA Astrophysics Data System (ADS)

Otsuka, Kenju; Nemoto, Kana; Kamikariya, Koji; Miyasaka, Yoshihiko; Chu, Shu-Chun

2007-09-01

Detailed oscillation spectra and polarization properties have been examined in laser-diode-pumped (LD-pumped) microchip ceramic (i.e., polycrystalline) Nd:YAG lasers and the inherent segregation of lasing patterns into local modes possessing different polarization states was observed. Single-frequency linearly-polarized stable oscillations were realized by forcing the laser to Ince-Gaussian mode operations by adjusting azimuthal cavity symmetry.

Tunable single frequency fiber laser based on FP-LD injection locking.

PubMed

Zhang, Aiqin; Feng, Xinhuan; Wan, Minggui; Li, Zhaohui; Guan, Bai-ou

2013-05-20

We propose and demonstrate a tunable single frequency fiber laser based on Fabry Pérot laser diode (FP-LD) injection locking. The single frequency operation principle is based on the fact that the output from a FP-LD injection locked by a multi-longitudinal-mode (MLM) light can have fewer longitudinal-modes number and narrower linewidth. By inserting a FP-LD in a fiber ring laser cavity, single frequency operation can be possibly achieved when stable laser oscillation established after many roundtrips through the FP-LD. Wavelength switchable single frequency lasing can be achieved by adjusting the tunable optical filter (TOF) in the cavity to coincide with different mode of the FP-LD. By adjustment of the drive current of the FP-LD, the lasing modes would shift and wavelength tunable operation can be obtained. In experiment, a wavelength tunable range of 32.4 nm has been obtained by adjustment of the drive current of the FP-LD and a tunable filter in the ring cavity. Each wavelength has a side-mode suppression ratio (SMSR) of at least 41 dB and a linewidth of about 13 kHz.

Two-gigawatt burst-mode operation of the intense microwave prototype (IMP) free-electron laser (FEL) for the microwave tokamak experiment (MTX)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Felker, B.; Allen, S.; Bell, H.

1993-10-06

The MTX explored the plasma heating effects of 140 GHz microwaves from both Gyrotrons and from the IMP FEL wiggler. The Gyrotron was long pulse length (0.5 seconds maximum) and the FEL produced short-pulse length, high-peak power, single and burst modes of 140 GHZ microwaves. Full-power operations of the IMP FEL wiggler were commenced in April of 1992 and continued into October of 1992. The Experimental Test Accelerator H (ETA-II) provided a 50-nanosecond, 6-MeV, 2--3 kAmp electron beam that was introduced co-linear into the IMP FEL with a 140 GHz Gyrotron master oscillator (MO). The FEL was able to amplifymore » the MO signal from approximately 7 kW to peaks consistently in the range of 1--2 GW. This microwave pulse was transmitted into the MTX and allowed the exploration of the linear and non-linear effects of short pulse, intense power in the MTX plasma. Single pulses were used to explore and gain operating experience in the parameter space of the IMP FEL, and finally evaluate transmission and absorption in the MTX. Single-pulse operations were repeatable. After the MTX was shut down burst-mode operations were successful at 2 kHz. This paper will describe the IMP FEL, Microwave Transmission System to MTX, the diagnostics used for calorimetric measurements, and the operations of the entire Microwave system. A discussion of correlated and uncorrelated errors that affect FEL performance will be made Linear and non-linear absorption data of the microwaves in the MTX plasma will be presented.« less

Single-mode VCSEL operation via photocurrent feedback

NASA Astrophysics Data System (ADS)

Riyopoulos, Spilios

1999-04-01

On-axis channeling through the use of photoactive layers in VCSEL cavities is proposed to counteract hole burning and mode switching. The photoactive layers act as variable resistivity screens whose radial `aperture' is controlled by the light itself. It is numerically demonstrated that absorption of a small fraction of the light intensity suffices for significant on axis current peaking and single mode operation at currents many times threshold, with minimum efficiency loss and optical mode distortion. Fabrication is implemented during the molecular beam epitaxy phase without wafer post processing, as for oxide apertures.

Performance Assessment of Single Electrode-Supported Solid Oxide Cells Operating in the Steam Electrolysis Mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

X. Zhang; J. E. O'Brien; R. C. O'Brien

2011-11-01

An experimental study is under way to assess the performance of electrode-supported solid-oxide cells operating in the steam electrolysis mode for hydrogen production. Results presented in this paper were obtained from single cells, with an active area of 16 cm{sup 2} per cell. The electrolysis cells are electrode-supported, with yttria-stabilized zirconia (YSZ) electrolytes ({approx}10 {mu}m thick), nickel-YSZ steam/hydrogen electrodes ({approx}1400 {mu}m thick), and modified LSM or LSCF air-side electrodes ({approx}90 {mu}m thick). The purpose of the present study is to document and compare the performance and degradation rates of these cells in the fuel cell mode and in the electrolysismore » mode under various operating conditions. Initial performance was documented through a series of voltage-current (VI) sweeps and AC impedance spectroscopy measurements. Degradation was determined through long-term testing, first in the fuel cell mode, then in the electrolysis mode. Results generally indicate accelerated degradation rates in the electrolysis mode compared to the fuel cell mode, possibly due to electrode delamination. The paper also includes details of an improved single-cell test apparatus developed specifically for these experiments.« less

Single transverse mode laser in a center-sunken and cladding-trenched Yb-doped fiber.

PubMed

Liu, Yehui; Zhang, Fangfang; Zhao, Nan; Lin, Xianfeng; Liao, Lei; Wang, Yibo; Peng, Jinggang; Li, Haiqing; Yang, LuYun; Dai, NengLi; Li, Jinyan

2018-02-05

We report a novel center-sunken and cladding-trenched Yb-doped fiber, which was fabricated by a modified chemical vapor deposition process with a solution-doping technique. The simulation results showed that the fiber with a core diameter of 40 µm and a numerical aperture of 0.043 has a 1217 µm 2 effective mode area at 1080 nm. It is also disclosed that the leakage loss can be reduced lower than 0.01 dB/m for the LP 01 mode, while over 80 dB/m for the LP 11 mode by optimizing the bending radius as 14 cm. A 456 W laser output was observed in a MOPA structure. The laser slope efficiency was measured to be 79% and the M 2 was less than 1.1, which confirmed the single mode operation of the large mode area center-sunken cladding-trenched Yb-doped fiber.

Single-Event Effect Performance of a Conductive-Bridge Memory EEPROM

NASA Technical Reports Server (NTRS)

Chen, Dakai; Wilcox, Edward; Berg, Melanie; Kim, Hak; Phan, Anthony; Figueiredo, Marco; Seidleck, Christina; LaBel, Kenneth

2015-01-01

We investigated the heavy ion SEE characteristics of an EEPROM based on CBRAM technology. SEFI is the dominant type of SEE for each operating mode (standby, read-only, write/read). We also observed single bit upsets in the CBRAM cell, during write/read tests. the SEULET threshold is between 10 and 20 MeV * sq cm/mg, with an upper fluence limit of 3 × 10(exp 6) cm(exp -2) at 10 MeV * sq cm/mg. In the stand by mode, the CBRAM array appears immune to bit upsets.

Investigations of SBS and Laser Gain Competition in High-Power Phase Modulated Fiber Amplifiers (Postprint)

DTIC Science & Technology

2014-02-26

through RF filtering . Subsequently, this modulated signal is used in a cutback experiment with a passive fiber . Studies describing enhancement factors...to filter out higher order modes [3]. However, in order to maintain single-mode (diffraction limited) operation, conventional step-index fiber core...Letters 36, 2686-2688 (2011). [3] J. P. Koplaw, D. Kliner, and L. Goldberg, “Single-mode operation of a coiled multimode fiber amplifier,” Optics Letters

High single-spatial-mode pulsed power from 980 nm emitting diode lasers

NASA Astrophysics Data System (ADS)

Hempel, Martin; Tomm, Jens W.; Elsaesser, Thomas; Bettiati, Mauro

2012-11-01

Single-spatial-mode pulsed powers as high as 13 W and 20 W in 150 and 50 ns pulses, respectively, are reported for 980 nm emitting lasers. In terms of energy, single-spatial-mode values of up to 2 μJ within 150 ns pulses are shown. In this high-power pulsed operation, the devices shield themselves from facet degradation, being the main degradation source in continuous wave (cw) operation. Our results pave the way towards additional applications while employing available standard devices, which have originally been designed as very reliable cw fiber pumps.

Advanced specialty fiber designs for high power fiber lasers

NASA Astrophysics Data System (ADS)

Gu, Guancheng

The output power of fiber lasers has increased rapidly over the last decade. There are two major limiting factors, namely nonlinear effects and transverse mode instability, prohibiting the power scaling capability of fiber lasers. The nonlinear effects, originating from high optical intensity, primarily limit the peak power scaling. The mode instability, on the other hand, arises from quantum-defect driven heating, causing undesired mode coupling once the power exceeds the threshold and degradation of beam quality. The mode instability has now become the bottleneck for average output power scaling of fiber lasers. Mode area scaling is the most effective way to mitigate nonlinear effects. However, the use of large mode area may increase the tendency to support multiple modes in the core, resulting in lower mode instability threshold. Therefore, it is critical to maintain single mode operation in a large mode area fiber. Sufficient higher order mode suppression can lead to effective single-transverse-mode propagation. In this dissertation, we explore the feasibility of using specialty fiber to construct high power fiber lasers with robust single-mode output. The first type of fiber discussed is the resonantly-enhanced leakage channel fiber. Coherent reflection at the fiber outer boundary can lead to additional confinement especially for highly leaky HOM, leading to lower HOM losses than what are predicted by conventional finite element mothod mode solver considering infinite cladding. In this work, we conducted careful measurements of HOM losses in two leakage channel fibers (LCF) with circular and rounded hexagonal boundary shapes respectively. Impact on HOM losses from coiling, fiber boundary shapes and coating indexes were studied in comparison to simulations. This work demonstrates the limit of the simulation method commonly used in the large-mode-area fiber designs and the need for an improved approach. More importantly, this work also demonstrates that a deviation from circular fiber outer shape may be an effective method to mitigate HOM loss reduction from coherent reflection from fiber outer boundary. In an all-solid photonic bandgap fiber, modes are only guided due to anti-resonance of cladding photonic crystal lattice. This provides strongly mode-dependent guidance, leading to very high differential mode losses, which is essential for lasing far from the gain peak and suppression of stimulated Raman scattering. We will show that all-solid photonic bandgap fibers with effective mode area of 920microm2 can be made with excellent higher order mode suppression. We then demonstrate a 50microm-core-diameter Yb-doped all-solid photonic bandgap fiber laser. 75W output power has been generated with a diffraction-limited beam and an efficiency of 70% relative to the launched pump power. We have also experimentally confirmed that a robust single-mode regime exists near the high frequency edge of the bandgap. It is well known that incorporation of additional smaller cores in the cladding can be used to resonantly out-couple higher-order modes from a main core to suppress higher-order-mode propagation in the main core. Using a novel design with multiple coupled smaller cores in the cladding, we further scaled up the mode area and have successfully demonstrated a single-mode photonic bandgap fiber with record effective mode area of 2650microm2. Detailed numeric studies have been conducted for multiple cladding designs. For the optimal designs, the simulated minimum higher-order-mode losses are well over two orders of magnitudes higher than that of fundamental mode when expressed in dBs. We have also experimentally validated one of the designs. M 2<1.08 across the transmission band was demonstrated. Lowering quantum defect heating is another approach to mitigate mode instability. Highly-efficient high-power fiber lasers operating at wavelength below 1020nm are critical for tandem-pumping in >10kW fiber lasers to provide high pump brightness and low thermal loading. Using an ytterbium-doped-phosphosilicate double-clad leakage-channel fiber with 50microm core and 420microm cladding, we have achieved 70% optical-to-optical efficiency at 1018nm. The much larger cladding than those in previous reports demonstrates the much lower required pump brightness, a key for efficient kW operation. The demonstrated 1018nm fiber laser has ASE suppression of 41dB. This is higher than previous reports and further demonstrates the advantages of the fiber used. Limiting factors to efficiency are also systematically studied.

An Approach for Economic Analysis of Intermodal Transportation

PubMed Central

Sahin, Bahri; Ust, Yasin; Guneri, Ali Fuat; Gulsun, Bahadir; Turan, Eda

2014-01-01

A different intermodal transportation model based on cost analysis considering technical, economical, and operational parameters is presented. The model consists of such intermodal modes as sea-road, sea-railway, road-railway, and multimode of sea-road-railway. A case study of cargo transportation has been carried out by using the suggested model. Then, the single road transportation mode has been compared to intermodal modes in terms of transportation costs. This comparison takes into account the external costs of intermodal transportation. The research reveals that, in the short distance transportation, single transportation modes always tend to be advantageous. As the transportation distance gets longer, intermodal transportation advantages begin to be effective on the costs. In addition, the proposed method in this study leads to determining the fleet size and capacity for transportation and the appropriate transportation mode. PMID:25152919

An approach for economic analysis of intermodal transportation.

PubMed

Sahin, Bahri; Yilmaz, Huseyin; Ust, Yasin; Guneri, Ali Fuat; Gulsun, Bahadir; Turan, Eda

2014-01-01

A different intermodal transportation model based on cost analysis considering technical, economical, and operational parameters is presented. The model consists of such intermodal modes as sea-road, sea-railway, road-railway, and multimode of sea-road-railway. A case study of cargo transportation has been carried out by using the suggested model. Then, the single road transportation mode has been compared to intermodal modes in terms of transportation costs. This comparison takes into account the external costs of intermodal transportation. The research reveals that, in the short distance transportation, single transportation modes always tend to be advantageous. As the transportation distance gets longer, intermodal transportation advantages begin to be effective on the costs. In addition, the proposed method in this study leads to determining the fleet size and capacity for transportation and the appropriate transportation mode.

Liquid-phase epitaxy grown PbSnTe distributed feedback laser diodes with broad continuous single-mode tuning range

NASA Technical Reports Server (NTRS)

Hsieh, H.-H.; Fonstad, C. G.

1980-01-01

Distributed feedback (DFB) pulsed laser operation has been demonstrated in stripe geometry Pb(1-x)Sn(x)Te double-heterostructures grown by liquid-phase epitaxy. The grating structure of 0.79 micron periodicity operates in first order near 12.8 microns and was fabricated prior to the liquid-phase epitaxial growth using holographic exposure techniques. These DFB lasers had moderate thresholds, 3.6 kA/sq cm, and the output power versus current curves exhibited a sharp turn-on free of kinks. Clean, single-mode emission spectra, continuously tunable over a range in excess of 20 per cm, centered about 780 per cm (12.8 microns), and at an average rate of 1.2 per cm-K from 9 to 26 K, were observed. While weaker modes could at times be seen in the spectrum, substantially single-mode operation was obtained over the entire operating range and to over 10 times threshold.

High-power, surface-emitting quantum cascade laser operating in a symmetric grating mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyle, C.; Sigler, C.; Kirch, J. D.

2016-03-21

Grating-coupled surface-emitting (GCSE) lasers generally operate with a double-lobed far-field beam pattern along the cavity-length direction, which is a result of lasing being favored in the antisymmetric grating mode. We experimentally demonstrate a GCSE quantum-cascade laser design allowing high-power, nearly single-lobed surface emission parallel to the longitudinal cavity. A 2nd-order Au-semiconductor distributed-feedback (DFB)/distributed-Bragg-reflector (DBR) grating is used for feedback and out-coupling. The DFB and DBR grating regions are 2.55 mm- and 1.28 mm-long, respectively, for a total grating length of 5.1 mm. The lasers are designed to operate in a symmetric (longitudinal) grating mode by causing resonant coupling of the guided optical modemore » to the antisymmetric surface-plasmon modes of the 2nd-order metal/semiconductor grating. Then, the antisymmetric modes are strongly absorbed by the metal in the grating, causing the symmetric mode to be favored to lase, which, in turn, produces a single-lobed beam over a range of grating duty-cycle values of 36%–41%. Simulations indicate that the symmetric mode is always favored to lase, independent of the random phase of reflections from the device's cleaved ends. Peak pulsed output powers of ∼0.4 W were measured with nearly single-lobe beam-pattern (in the longitudinal direction), single-spatial-mode operation near 4.75 μm wavelength. Far-field measurements confirm a diffraction-limited beam pattern, in agreement with simulations, for a source-to-detector separation of 2 m.« less

Mode selection and tuning of single-frequency short-cavity VECSELs

DOE PAGES

Serkland, Darwin K.; So, Haley M.; Peake, Gregory M.; ...

2018-03-05

Here, we report on mode selection and tuning properties of vertical-external-cavity surface-emitting lasers (VECSELs) containing coupled semiconductor and external cavities of total length less than 1 mm. Our goal is to create narrowlinewidth (<1MHz) single-frequency VECSELs that operate near 850 nm on a single longitudinal cavity resonance and tune versus temperature without mode hops. We have designed, fabricated, and measured VECSELs with external-cavity lengths ranging from 25 to 800 μm. Lastly, we compare simulated and measured coupled-cavity mode frequencies and discuss criteria for single mode selection.

Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser.

PubMed

Wang, P; Cooper, L J; Sahu, J K; Clarkson, W A

2006-01-15

A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a 30 microm diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded 60.4 W of output at 1043 nm in a beam with M2 < 1.4 for 92.6 W launched pump power from a diode stack at 976 nm. The slope efficiency at pump powers well above threshold was approximately 84%, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.

The Single Event Effect Characteristics of the 486-DX4 Microprocessor

NASA Technical Reports Server (NTRS)

Kouba, Coy; Choi, Gwan

1996-01-01

This research describes the development of an experimental radiation testing environment to investigate the single event effect (SEE) susceptibility of the 486-DX4 microprocessor. SEE effects are caused by radiation particles that disrupt the logic state of an operating semiconductor, and include single event upsets (SEU) and single event latchup (SEL). The relevance of this work can be applied directly to digital devices that are used in spaceflight computer systems. The 486-DX4 is a powerful commercial microprocessor that is currently under consideration for use in several spaceflight systems. As part of its selection process, it must be rigorously tested to determine its overall reliability in the space environment, including its radiation susceptibility. The goal of this research is to experimentally test and characterize the single event effects of the 486-DX4 microprocessor using a cyclotron facility as the fault-injection source. The test philosophy is to focus on the "operational susceptibility," by executing real software and monitoring for errors while the device is under irradiation. This research encompasses both experimental and analytical techniques, and yields a characterization of the 486-DX4's behavior for different operating modes. Additionally, the test methodology can accommodate a wide range of digital devices, such as microprocessors, microcontrollers, ASICS, and memory modules, for future testing. The goals were achieved by testing with three heavy-ion species to provide different linear energy transfer rates, and a total of six microprocessor parts were tested from two different vendors. A consistent set of error modes were identified that indicate the manner in which the errors were detected in the processor. The upset cross-section curves were calculated for each error mode, and the SEU threshold and saturation levels were identified for each processor. Results show a distinct difference in the upset rate for different configurations of the on-chip cache, as well as proving that one vendor is superior to the other in terms of latchup susceptibility. Results from this testing were also used to provide a mean-time-between-failure estimate of the 486-DX4 operating in the radiation environment for the International Space Station.

Single-mode temperature and polarisation-stable high-speed 850nm vertical cavity surface emitting lasers

NASA Astrophysics Data System (ADS)

Nazaruk, D. E.; Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Vasil'ev, A. P.; Gladyshev, A. G.; Pavlov, M. M.; Blokhin, A. A.; Kulagina, M. M.; Vashanova, K. A.; Zadiranov, Yu M.; Fefelov, A. G.; Ustinov, V. M.

2014-12-01

A new intracavity-contacted design to realize temperature and polarization-stable high-speed single-mode 850 nm vertical cavity surface emitting lasers (VCSELs) grown by molecular-beam epitaxy is proposed. Temperature dependences of static and dynamic characteristics of the 4.5 pm oxide aperture InGaAlAs VCSEL were investigated in detail. Due to optimal gain-cavity detuning and enhanced carrier localization in the active region the threshold current remains below 0.75 mA for the temperature range within 20-90°C, while the output power exceeds 1 mW up to 90°C. Single-mode operation with side-mode suppression ratio higher than 30 dB and orthogonal polarization suppression ratio more than 18 dB was obtained in the whole current and temperature operation range. Device demonstrates serial resistance less than 250 Ohm, which is rather low for any type of single-mode short- wavelength VCSELs. VCSEL demonstrates temperature robust high-speed operation with modulation bandwidth higher than 13 GHz in the entire temperature range of 20-90°C. Despite high resonance frequency the high-speed performance of developed VCSELs was limited by the cut-off frequency of the parasitic low pass filter created by device resistances and capacitances. The proposed design is promising for single-mode high-speed VCSEL applications in a wide spectral range.

Implementation of single-photon quantum routing and decoupling using a nitrogen-vacancy center and a whispering-gallery-mode resonator-waveguide system.

PubMed

Cao, Cong; Duan, Yu-Wen; Chen, Xi; Zhang, Ru; Wang, Tie-Jun; Wang, Chuan

2017-07-24

Quantum router is a key element needed for the construction of future complex quantum networks. However, quantum routing with photons, and its inverse, quantum decoupling, are difficult to implement as photons do not interact, or interact very weakly in nonlinear media. In this paper, we investigate the possibility of implementing photonic quantum routing based on effects in cavity quantum electrodynamics, and present a scheme for single-photon quantum routing controlled by the other photon using a hybrid system consisting of a single nitrogen-vacancy (NV) center coupled with a whispering-gallery-mode resonator-waveguide structure. Different from the cases in which classical information is used to control the path of quantum signals, both the control and signal photons are quantum in our implementation. Compared with the probabilistic quantum routing protocols based on linear optics, our scheme is deterministic and also scalable to multiple photons. We also present a scheme for single-photon quantum decoupling from an initial state with polarization and spatial-mode encoding, which can implement an inverse operation to the quantum routing. We discuss the feasibility of our schemes by considering current or near-future techniques, and show that both the schemes can operate effectively in the bad-cavity regime. We believe that the schemes could be key building blocks for future complex quantum networks and large-scale quantum information processing.

Continuous-Wave Single-Frequency Operation of Fabry-Perot Laser Diodes by Self-Injection Phase Locking Using Feedback from a Fiber Bragg Grating

NASA Technical Reports Server (NTRS)

Duerksen, Gary L.; Krainak, Michael A.

1998-01-01

Single-frequency operation of uncoated Fabry-Perot laser diodes is demonstrated by phase- locking the laser oscillations through self-injection seeding with feedback from a fiber Bragg grating. By precisely tuning the laser temperature so that an axial-mode coincides with the short-wavelength band edge of the grating, the phase of the feedback is made conjugate to that of the axial mode, locking the phase of the laser oscillations to that mode.

40 CFR 63.1402 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... properties may vary with time. For a unit operation operated in a batch mode (i.e., batch unit operation... means a unit operation operated in a batch mode. Block means the time period that comprises a single batch cycle. Combustion device burner means a device designed to mix and ignite fuel and air to provide...

40 CFR 63.1402 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... properties may vary with time. For a unit operation operated in a batch mode (i.e., batch unit operation... means a unit operation operated in a batch mode. Block means the time period that comprises a single batch cycle. Combustion device burner means a device designed to mix and ignite fuel and air to provide...

40 CFR 63.1402 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... properties may vary with time. For a unit operation operated in a batch mode (i.e., batch unit operation... means a unit operation operated in a batch mode. Block means the time period that comprises a single batch cycle. Combustion device burner means a device designed to mix and ignite fuel and air to provide...

40 CFR 63.1402 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... properties may vary with time. For a unit operation operated in a batch mode (i.e., batch unit operation... means a unit operation operated in a batch mode. Block means the time period that comprises a single batch cycle. Combustion device burner means a device designed to mix and ignite fuel and air to provide...

40 CFR 63.1402 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... properties may vary with time. For a unit operation operated in a batch mode (i.e., batch unit operation... means a unit operation operated in a batch mode. Block means the time period that comprises a single batch cycle. Combustion device burner means a device designed to mix and ignite fuel and air to provide...

Single-mode very wide tunability in laterally coupled semiconductor lasers with electrically controlled reflectivities

NASA Astrophysics Data System (ADS)

Griffel, Giora; Chen, Howard Z.; Grave, Ilan; Yariv, Amnon

1991-04-01

The operation of a novel multisection structure comprised of laterally coupled gain-guided semiconductor lasers is demonstrated. It is shown that tunable single longitudinal mode operation can be achieved with a high degree of frequency selectivity. The device has a tuning range of 14.5 nm, the widest observed to date in a monolithic device.

Method and apparatus for single-stepping coherence events in a multiprocessor system under software control

DOEpatents

Blumrich, Matthias A.; Salapura, Valentina

2010-11-02

An apparatus and method are disclosed for single-stepping coherence events in a multiprocessor system under software control in order to monitor the behavior of a memory coherence mechanism. Single-stepping coherence events in a multiprocessor system is made possible by adding one or more step registers. By accessing these step registers, one or more coherence requests are processed by the multiprocessor system. The step registers determine if the snoop unit will operate by proceeding in a normal execution mode, or operate in a single-step mode.

Cryogenic motion performances of a piezoelectric single crystal micromotor

NASA Astrophysics Data System (ADS)

Li, Xiaotian; Wu, Yuting; Chen, Zhijiang; Wei, Xiaoyong; Luo, Haosu; Dong, Shuxiang

2014-04-01

This study investigates the cryogenic performances of a millimeter-size piezoelectric ultrasonic linear micromotor. The piezoelectric vibrator of the micromotor is made of Pb(In1/2Nb1/2)O3 -Pb(Mg1/3Nb2/3)-PbTiO3 single crystal and operated in first-bending wobbling mode. Experiments show that the piezoelectric single crystal micromotor works effectively even at extremely low temperature of -175 °C, although its resonance peaks vary with temperature significantly. This work confirms the feasibility of cryogenic operation of the piezo-micromotor, which is meaningful for aerospace or superconducting microwave application.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serkland, Darwin K.; So, Haley M.; Peake, Gregory M.

Here, we report on mode selection and tuning properties of vertical-external-cavity surface-emitting lasers (VECSELs) containing coupled semiconductor and external cavities of total length less than 1 mm. Our goal is to create narrowlinewidth (<1MHz) single-frequency VECSELs that operate near 850 nm on a single longitudinal cavity resonance and tune versus temperature without mode hops. We have designed, fabricated, and measured VECSELs with external-cavity lengths ranging from 25 to 800 μm. Lastly, we compare simulated and measured coupled-cavity mode frequencies and discuss criteria for single mode selection.

High Temperature Electrolysis using Electrode-Supported Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. E. O'Brien; C. M. Stoots

2010-07-01

An experimental study is under way to assess the performance of electrode-supported solid-oxide cells operating in the steam electrolysis mode for hydrogen production. The cells currently under study were developed primarily for the fuel cell mode of operation. Results presented in this paper were obtained from single cells, with an active area of 16 cm2 per cell. The electrolysis cells are electrode-supported, with yttria-stabilized zirconia (YSZ) electrolytes (~10 µm thick), nickel-YSZ steam/hydrogen electrodes (~1400 µm thick), and manganite (LSM) air-side electrodes (~90 µm thick). The purpose of the present study was to document and compare the performance and degradation ratesmore » of these cells in the fuel cell mode and in the electrolysis mode under various operating conditions. Initial performance was documented through a series of DC potential sweeps and AC impedance spectroscopy measurements. Degradation was determined through long-duration testing, first in the fuel cell mode, then in the electrolysis mode over more than 500 hours of operation. Results indicate accelerated degradation rates in the electrolysis mode compared to the fuel cell mode, possibly due to electrode delamination. The paper also includes details of the single-cell test apparatus developed specifically for these experiments.« less

Highly angular dependent high-contrast grating mirror and its application for transverse-mode control of VCSELs

NASA Astrophysics Data System (ADS)

Inoue, Shunya; Kashino, Junichi; Matsutani, Akihiro; Ohtsuki, Hideo; Miyashita, Takahiro; Koyama, Fumio

2014-09-01

We report on the design and fabrication of a highly angular dependent high contrast grating (HCG) mirror. The modeling and experiment on amorphous-Si/SiO2 HCG clearly show the large angular dependence of reflectivity, which enables single transverse-mode operations of large-area VCSELs. We fabricate 980 nm VCSELs with the angular dependent HCG functioning as a spatial frequency filter. We obtained the single transverse mode operation of the fabricated device in contrast to conventional VCSELs with semiconductor multilayer mirrors.

High power single-longitudinal-mode Ho:YLF unidirectional ring laser based on a composite structure of acousto-optic device and wave plate

NASA Astrophysics Data System (ADS)

Dai, T. Y.; Fan, Z. G.; Wu, J.; Ju, Y. L.; Yao, B. Q.; Zhang, Z. G.; Teng, K.; Xu, X. G.; Duan, X. M.

2017-05-01

We report a unidirectional single-longitudinal-mode Ho:YLF ring laser. An acousto-optic modulator and two half-wave plates were used to enforce the Ho:YLF ring laser in a unidirectional operation. The single-longitudinal-mode output power could reach 3.73 W successfully when the incident pump power was 16.4 W. The corresponding slope efficiency was 27.1%. The wavelength of the single-longitudinal-mode Ho:YLF ring laser was 2063.8 nm. The M2 factor was 1.12. The results illustrated that the single-longitudinal-mode output power could be further enhanced by increasing the radio frequency power of the acousto-optic modulator.

Multiplexed electronically programmable multimode ionization detector for chromatography

DOEpatents

Wise, M.B.; Buchanan, M.V.

1988-05-19

Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electronically programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes. A system is provided which automatically controls the programmed application of bias pulses at different intervals and/or amplitudes to switch the detector from an ionization mode to the electron capture mode and various degrees therebetween to provide an improved means of tuning an ECD for multimode detection and improved specificity. 6 figs.

Multiplexed electronically programmable multimode ionization detector for chromatography

DOEpatents

Wise, Marcus B.; Buchanan, Michelle V.

1989-01-01

Method and apparatus for detecting and differentiating organic compounds based on their electron affinity. An electron capture detector cell (ECD) is operated in a plurality of multiplexed electroncially programmable operating modes to alter the detector response during a single sampling cycle to acquire multiple simultaneous chromatograms corresponding to each of the different operating modes. The cell is held at a constant subatmospheric pressure while the electron collection bias voltage applied to the cell is modulated electronically to allow acquisition of multiple chromatograms for a single sample elution from a chromatograph representing three distinctly different response modes. A system is provided which automatically controls the programmed application of bias pulses at different intervals and/or amplitudes to switch the detector from an ionization mode to the electron capture mode and various degrees therebetween to provide an improved means of tuning an ECD for multimode detection and improved specificity.

Mentoring console improves collaboration and teaching in surgical robotics.

PubMed

Hanly, Eric J; Miller, Brian E; Kumar, Rajesh; Hasser, Christopher J; Coste-Maniere, Eve; Talamini, Mark A; Aurora, Alexander A; Schenkman, Noah S; Marohn, Michael R

2006-10-01

One of the most significant limitations of surgical robots has been their inability to allow multiple surgeons and surgeons-in-training to engage in collaborative control of robotic surgical instruments. We report the initial experience with a novel two-headed da Vinci surgical robot that has two collaborative modes: the "swap" mode allows two surgeons to simultaneously operate and actively swap control of the robot's four arms, and the "nudge" mode allows them to share control of two of the robot's arms. The utility of the mentoring console operating in its two collaborative modes was evaluated through a combination of dry laboratory exercises and animal laboratory surgery. The results from surgeon-resident collaborative performance of complex three-handed surgical tasks were compared to results from single-surgeon and single-resident performance. Statistical significance was determined using Student's t-test. Collaborative surgeon-resident swap control reduced the time to completion of complex three-handed surgical tasks by 25% compared to single-surgeon operation of a four-armed da Vinci (P < 0.01) and by 34% compared to single-resident operation (P < 0.001). While swap mode was found to be most helpful during parts of surgical procedures that require multiple hands (such as isolation and division of vessels), nudge mode was particularly useful for guiding a resident's hands during crucially precise steps of an operation (such as proper placement of stitches). The da Vinci mentoring console greatly facilitates surgeon collaboration during robotic surgery and improves the performance of complex surgical tasks. The mentoring console has the potential to improve resident participation in surgical robotics cases, enhance resident education in surgical training programs engaged in surgical robotics, and improve patient safety during robotic surgery.

Diffractive Combiner of Single-Mode Pump Laser-Diode Beams

NASA Technical Reports Server (NTRS)

Liu, Duncan; Wilson, Daniel; Qiu, Yueming; Forouhar, Siamak

2007-01-01

An optical beam combiner now under development would make it possible to use the outputs of multiple single-mode laser diodes to pump a neodymium: yttrium aluminum garnet (Nd:YAG) nonplanar ring oscillator (NPRO) laser while ensuring that the laser operates at only a single desired frequency. Heretofore, an Nd:YAG NPRO like the present one has been pumped by a single multimode laser-diode beam delivered via an optical fiber. It would be desirable to use multiple pump laser diodes to increase reliability beyond that obtainable from a single pump laser diode. However, as explained below, simplistically coupling multiple multimode laser-diode beams through a fiber-optic combiner would entail a significant reduction in coupling efficiency, and lasing would occur at one or more other frequencies in addition to the single desired frequency. Figure 1 schematically illustrates the principle of operation of a laser-diode-pumped Nd:YAG NPRO. The laser beam path is confined in a Nd:YAG crystal by means of total internal reflections on the three back facets and a partial-reflection coating on the front facet. The wavelength of the pump beam - 808 nm - is the wavelength most strongly absorbed by the Nd:YAG crystal. The crystal can lase at a wavelength of either 1,064 nm or 1,319 nm - which one depending on the optical coating on the front facet. A thermal lens effect induced by the pump beam enables stable lasing in the lowest-order transverse electromagnetic mode (the TEM00 mode). The frequency of this laser is very stable because of the mechanical stability of the laser crystal and the unidirectional nature of the lasing. The unidirectionality is a result of the combined effects of (1) a Faraday rotation induced by an externally applied magnetic field and (2) polarization associated with non-normal incidence and reflection on the front facet.

Model-OA wind turbine generator - Failure modes and effects analysis

NASA Technical Reports Server (NTRS)

Klein, William E.; Lali, Vincent R.

1990-01-01

The results failure modes and effects analysis (FMEA) conducted for wind-turbine generators are presented. The FMEA was performed for the functional modes of each system, subsystem, or component. The single-point failures were eliminated for most of the systems. The blade system was the only exception. The qualitative probability of a blade separating was estimated at level D-remote. Many changes were made to the hardware as a result of this analysis. The most significant change was the addition of the safety system. Operational experience and need to improve machine availability have resulted in subsequent changes to the various systems, which are also reflected in this FMEA.

Browns Ferry-1 single-loop operation tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

March-Leuba, J.; Wood, R.T.; Otaduy, P.J.

1985-09-01

This report documents the results of the stability tests performed on February 9, 1985, at the Browns Ferry Nuclear Power Plant Unit 1 under single-loop operating conditions. The observed increase in neutron noise during single-loop operation is solely due to an increase in flow noise. The Browns Ferry-1 reactor has been found to be stable in all modes of operation attained during the present tests. The most unstable test plateau corresponded to minimum recirculation pump speed in single-loop operation (test BFTP3). This operating condition had the minimum flow and maximum power-to-flow ratio. The estimated decay ratio in this plateau ismore » 0.53. The decay ratio decreased as the flow was increased during single-loop operation (down to 0.34 for test plateau BFTP6). This observation implies that the core-wide reactor stability follows the same trends in single-loop as it does in two-loop operation. Finally, no local or higher mode instabilities were found in the data taken from local power range monitors. The decay ratios estimated from the local power range monitors were not significantly different from those estimated from the average power range monitors.« less

Transverse single-mode edge-emitting lasers based on coupled waveguides.

PubMed

Gordeev, Nikita Yu; Payusov, Alexey S; Shernyakov, Yuri M; Mintairov, Sergey A; Kalyuzhnyy, Nikolay A; Kulagina, Marina M; Maximov, Mikhail V

2015-05-01

We report on the transverse single-mode emission from InGaAs/GaAs quantum well edge-emitting lasers with broadened waveguide. The lasers are based on coupled large optical cavity (CLOC) structures where high-order vertical modes of the broad active waveguide are suppressed due to their resonant tunneling into a coupled single-mode passive waveguide. The CLOC lasers have shown stable Gaussian-shaped vertical far-field profiles with a reduced divergence of ∼22° FWHM (full width at half-maximum) in CW (continuous-wave) operation.

Electrical characteristics of organic perylene single-crystal-based field-effect transistors

NASA Astrophysics Data System (ADS)

Lee, Jin-Woo; Kang, Han-Saem; Kim, Min-Ki; Kim, Kihyun; Cho, Mi-Yeon; Kwon, Young-Wan; Joo, Jinsoo; Kim, Jae-Il; Hong, Chang-Seop

2007-12-01

We report on the fabrication of organic field-effect transistors (OFETs) using perylene single crystal as the active material and their electrical characteristics. Perylene single crystals were directly grown from perylene powder in a furnace using a relatively short growth time of 1-3 h. The crystalline structure of the perylene single crystals was characterized by means of a single-crystal x-ray diffractometer. In order to place the perylene single crystal onto the Au electrodes of the field-effect transistor, a polymethlymethacrylate thin layer was spin-coated on top of the crystal surface. The OFETs fabricated using the perylene single crystal showed a typical p-type operating mode. The field-effect mobility of the perylene crystal based OFETs was measured to be ˜9.62×10-4 cm2/V s at room temperature. The anisotropy of the mobility implying the existence of different mobilities when applying currents in different directions was observed for the OFETs, and the existence of traps in the perylene crystal was found through the measurements of the temperature-dependent mobility at various operating drain voltages.

Mode selection in square resonator microlasers for widely tunable single mode lasing.

PubMed

Tang, Ming-Ying; Sui, Shao-Shuai; Yang, Yue-De; Xiao, Jin-Long; Du, Yun; Huang, Yong-Zhen

2015-10-19

Mode selection in square resonator semiconductor microlasers is demonstrated by adjusting the width of the output waveguide coupled to the midpoint of one side. The simulation and experimental results reveal that widely tunable single mode lasing can be realized in square resonator microlasers. Through adjusting the width of the output waveguide, the mode interval of the high-Q modes can reach four times of the longitudinal mode interval. Therefore, mode hopping can be efficiently avoided and the lasing wavelength can be tuned continuously by tuning the injection current. For a 17.8-μm-side-length square microlaser with a 1.4-μm-width output waveguide, mode-hopping-free single-mode operation is achieved with a continuous tuning range of 9.2 nm. As a result, the control of the lasing mode is realized for the square microlasers.

A single supply biopotential amplifier.

PubMed

Spinelli, E M; Martinez, N H; Mayosky, M A

2001-04-01

A biopotential amplifier for single supply operation is presented. It uses a Driven Right Leg Circuit (DRL) to drive the patient's body to a DC common mode voltage, centering biopotential signals with respect to the amplifier's input voltage range. This scheme ensures proper range operation when a single power supply is used. The circuit described is especially suited for low consumption, battery-powered applications, requiring a single battery and avoiding switching voltage inverters to achieve dual supplies. The generic circuit is described and, as an example, a biopotential amplifier with a gain of 60 dB and a DC input range of +/-200 mV was implemented using low power operational amplifiers. A Common Mode Rejection Ratio (CMRR) of 126 dB at 50 Hz was achieved without trimming.

Pseudo-single-bunch mode for a 100 MHz storage ring serving soft X-ray timing experiments

NASA Astrophysics Data System (ADS)

Olsson, T.; Leemann, S. C.; Georgiev, G.; Paraskaki, G.

2018-06-01

At many storage rings for synchrotron light production there is demand for serving both high-flux and timing users simultaneously. Today this is most commonly achieved by operating inhomogeneous fill patterns, but this is not preferable for rings that employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. For these rings, inhomogeneous fill patterns could severely reduce the effect of the harmonic cavities. It is therefore of interest to develop methods to serve high-flux and timing users simultaneously without requiring gaps in the fill pattern. One such method is pseudo-single-bunch (PSB), where one bunch in the bunch train is kicked onto another orbit by a fast stripline kicker. The light emitted from the kicked bunch can then be separated by an aperture in the beamline. Due to recent developments in fast kicker design, PSB operation in multibunch mode is within reach for rings that operate with a 100 MHz RF system, such as the MAX IV and Solaris storage rings. This paper describes machine requirements and resulting performance for such a mode at the MAX IV 1.5 GeV storage ring. A solution for serving all beamlines is discussed as well as the consequences of beamline design and operation in the soft X-ray energy range.

Laterally Coupled Quantum-Dot Distributed-Feedback Lasers

NASA Technical Reports Server (NTRS)

Qui, Yueming; Gogna, Pawan; Muller, Richard; Maker, paul; Wilson, Daniel; Stintz, Andreas; Lester, Luke

2003-01-01

InAs quantum-dot lasers that feature distributed feedback and lateral evanescent- wave coupling have been demonstrated in operation at a wavelength of 1.3 m. These lasers are prototypes of optical-communication oscillators that are required to be capable of stable single-frequency, single-spatial-mode operation. A laser of this type (see figure) includes an active layer that comprises multiple stacks of InAs quantum dots embedded within InGaAs quantum wells. Distributed feedback is provided by gratings formed on both sides of a ridge by electron lithography and reactive-ion etching on the surfaces of an AlGaAs/GaAs waveguide. The lateral evanescent-wave coupling between the gratings and the wave propagating in the waveguide is strong enough to ensure operation at a single frequency, and the waveguide is thick enough to sustain a stable single spatial mode. In tests, the lasers were found to emit continuous-wave radiation at temperatures up to about 90 C. Side modes were found to be suppressed by more than 30 dB.

Improvements in Production of Single-Walled Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Balzano, Leandro; Resasco, Daniel E.

2009-01-01

A continuing program of research and development has been directed toward improvement of a prior batch process in which single-walled carbon nanotubes are formed by catalytic disproportionation of carbon monoxide in a fluidized-bed reactor. The overall effect of the improvements has been to make progress toward converting the process from a batch mode to a continuous mode and to scaling of production to larger quantities. Efforts have also been made to optimize associated purification and dispersion post processes to make them effective at large scales and to investigate means of incorporating the purified products into composite materials. The ultimate purpose of the program is to enable the production of high-quality single-walled carbon nanotubes in quantities large enough and at costs low enough to foster the further development of practical applications. The fluidized bed used in this process contains mixed-metal catalyst particles. The choice of the catalyst and the operating conditions is such that the yield of single-walled carbon nanotubes, relative to all forms of carbon (including carbon fibers, multi-walled carbon nanotubes, and graphite) produced in the disproportionation reaction is more than 90 weight percent. After the reaction, the nanotubes are dispersed in various solvents in preparation for end use, which typically involves blending into a plastic, ceramic, or other matrix to form a composite material. Notwithstanding the batch nature of the unmodified prior fluidized-bed process, the fluidized-bed reactor operates in a continuous mode during the process. The operation is almost entirely automated, utilizing mass flow controllers, a control computer running software specific to the process, and other equipment. Moreover, an important inherent advantage of fluidized- bed reactors in general is that solid particles can be added to and removed from fluidized beds during operation. For these reasons, the process and equipment were amenable to modification for conversion from batch to continuous production.

Quantum propagation in single mode fiber

NASA Technical Reports Server (NTRS)

Joneckis, Lance G.; Shapiro, Jeffrey H.

1994-01-01

This paper presents a theory for quantum light propagation in a single-mode fiber which includes the effects of the Kerr nonlinearity, group-velocity dispersion, and linear loss. The theory reproduces the results of classical self-phase modulation, quantum four-wave mixing, and classical solution physics, within their respective regions of validity. It demonstrates the crucial role played by the Kerr-effect material time constant, in limiting the quantum phase shifts caused by the broadband zero-point fluctuations that accompany any quantized input field. Operator moment equations - approximated, numerically, via a terminated cumulant expansion - are used to obtain results for homodyne-measurement noise spectra when dispersion is negligible. More complicated forms of these equations can be used to incorporate dispersion into the noise calculations.

Wide single-mode tuning in quantum cascade lasers with asymmetric Mach-Zehnder interferometer type cavities with separately biased arms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Mei C., E-mail: meizheng@princeton.edu; Gmachl, Claire F.; Liu, Peter Q.

2013-11-18

We report on the experimental demonstration of a widely tunable single mode quantum cascade laser with Asymmetric Mach-Zehnder (AMZ) interferometer type cavities with separately biased arms. Current and, consequently, temperature tuning of the two arms of the AMZ type cavity resulted in a single mode tuning range of 20 cm{sup −1} at 80 K in continuous-wave mode operation, a ten-fold improvement from the lasers under a single bias current. In addition, we also observed a five fold increase in the tuning rate as compared to the AMZ cavities controlled by one bias current.

Theoretical Studies of Low-Loss Optical Fibers.

DTIC Science & Technology

1980-09-15

on the fiber surface. Single-mode fiber operation is of interest in communications. Marcuse has shown that surface imperfections are a strong source...0.01 very small value of a : 8A at X = 1 vim Marcuse single mode 2.7 typical value of a = 1 jim, A : 10.6 vm, af = 37 Pim surface imperfections 55...Braunstein, "Scattering Losses in Single and Polycrystalline Materials for Infrared Fiber Applications," unpublished. 5. D. Marcuse , "Mode Conversion

Dual-pulses and harmonic patterns of a square-wave soliton in passively mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Zhang, Jing; Jia, Qingsong; Jiang, Huilin

2018-06-01

We demonstrate a square-wave soliton pulse passively mode-locked fiber laser. The mode-locked pulses are achieved by using a nonlinear amplifying loop mirror. Single-pulse operation at a fundamental repetition rate of 3.2 MHz is obtained. The optical spectrum presents the soliton feature of several sidebands. The pulse duration expands with increasing pump power, but the amplitude hardly varies. Pulse breaking occurs and a stable dual-pulse is obtained with a fixed interval of 48 ns. Harmonic mode-locked states can be achieved when the total pump power is higher than 740 mW. The harmonic pulses can also operate in both single-pulse and dual-pulse states.

Single-frequency Ince-Gaussian mode operations of laser-diode-pumped microchip solid-state lasers.

PubMed

Ohtomo, Takayuki; Kamikariya, Koji; Otsuka, Kenju; Chu, Shu-Chun

2007-08-20

Various single-frequency Ince-Gaussian mode oscillations have been achieved in laser-diode-pumped microchip solid-state lasers, including LiNdP(4)O(12) (LNP) and Nd:GdVO(4), by adjusting the azimuthal symmetry of the short laser resonator. Ince-Gaussian modes formed by astigmatic pumping have been reproduced by numerical simulation.

On-chip electrically controlled routing of photons from a single quantum dot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bentham, C.; Coles, R. J.; Royall, B.

2015-06-01

Electrical control of on-chip routing of photons emitted by a single InAs/GaAs self-assembled quantum dot (SAQD) is demonstrated in a photonic crystal cavity-waveguide system. The SAQD is located inside an H1 cavity, which is coupled to two photonic crystal waveguides. The SAQD emission wavelength is electrically tunable by the quantum-confined Stark effect. When the SAQD emission is brought into resonance with one of two H1 cavity modes, it is preferentially routed to the waveguide to which that mode is selectively coupled. This proof of concept provides the basis for scalable, low-power, high-speed operation of single-photon routers for use in integratedmore » quantum photonic circuits.« less

All-solid-state single longitudinal mode MOPA laser system

NASA Astrophysics Data System (ADS)

Zhang, Xiang; Gu, Haidong; Hu, Wenhua; Ren, Shilong

2018-03-01

Side diode pumped electro-optical Q Switching Nd: YAG is demonstrated as master oscillator. F-P etalon and twisted-mode cavity combined configuration is introduced to select longitudinal modes. The seed light experiences a round trip through the two flash pump amplifiers, in this device, the 4f image transmission system and SBS phase conjugate mirror is adopted in order to improved beam quality, by compensating the heat depolarization effect and eliminate wave-front distortion. In the condition of 1 or 5 repetitions of the wavelength at 1064nm, it produces the pulse energy of 300mJ, pulse width of 12ns, and energy instability (RMS) below 3% in single longitudinal mode operation. With a type two-phase matched KTP crystal, 532nm green light is yielded, at 1 Hz repetition rate, the pulse energy of green light is more than 150mJ.

Electric vehicle drive train with direct coupling transmission

DOEpatents

Tankersley, J.B.; Boothe, R.W.; Konrad, C.E.

1995-04-04

An electric vehicle drive train includes an electric motor and an associated speed sensor, a transmission operable in a speed reduction mode or a direct coupled mode, and a controller responsive to the speed sensor for operating the transmission in the speed reduction mode when the motor is below a predetermined value, and for operating the motor in the direct coupled mode when the motor speed is above a predetermined value. The controller reduces the speed of the motor, such as by regeneratively braking the motor, when changing from the speed reduction mode to the direct coupled mode. The motor speed may be increased when changing from the direct coupled mode to the speed reduction mode. The transmission is preferably a single stage planetary gearbox. 6 figures.

Electric vehicle drive train with direct coupling transmission

DOEpatents

Tankersley, Jerome B.; Boothe, Richard W.; Konrad, Charles E.

1995-01-01

An electric vehicle drive train includes an electric motor and an associated speed sensor, a transmission operable in a speed reduction mode or a direct coupled mode, and a controller responsive to the speed sensor for operating the transmission in the speed reduction mode when the motor is below a predetermined value, and for operating the motor in the direct coupled mode when the motor speed is above a predetermined value. The controller reduces the speed of the motor, such as by regeneratively braking the motor, when changing from the speed reduction mode to the direct coupled mode. The motor speed may be increased when changing from the direct coupled mode to the speed reduction mode. The transmission is preferably a single stage planetary gearbox.

Bend-resistant large mode area fiber with novel segmented cladding

NASA Astrophysics Data System (ADS)

Ma, Shaoshuo; Ning, Tigang; Pei, Li; Li, Jing; Zheng, Jingjing

2018-01-01

A novel structure of segment cladding fiber (SCF) with characteristics of bend-resistance and large-mode-area (LMA) is proposed. In this new structure, the high refractive index (RI) core is periodically surrounded by high RI fan-segmented claddings. Numerical investigations show that effective single-mode operation of the proposed fiber with mode field area of 700 μm2 can be achieved when the bending radius is 15 cm. Besides, this fiber is insensitive to the bending orientation at the ranging of [-180°, 180°]. The proposed design shows great potential in high power fiber lasers and amplifiers with compact structure.

Single chip camera active pixel sensor

NASA Technical Reports Server (NTRS)

Shaw, Timothy (Inventor); Pain, Bedabrata (Inventor); Olson, Brita (Inventor); Nixon, Robert H. (Inventor); Fossum, Eric R. (Inventor); Panicacci, Roger A. (Inventor); Mansoorian, Barmak (Inventor)

2003-01-01

A totally digital single chip camera includes communications to operate most of its structure in serial communication mode. The digital single chip camera include a D/A converter for converting an input digital word into an analog reference signal. The chip includes all of the necessary circuitry for operating the chip using a single pin.

Integrated-Optic Wavelength Multiplexer In Glass Fabricated By A Charge Controlled Ion Exchange

NASA Astrophysics Data System (ADS)

Klein, R.; Jestel, D.; Lilienhof, H. J.; Rottman, F.; Voges, E.

1989-02-01

Integrated-optic wavelength division multiplexing (WDM) is commonly used in communication systems. These WDM-devices are also well suited to build up optical fiber networks for both intensity and interferometric sensor types. The operation principle of our wavelength division multiplexing devise is based on the wavelength dependent two-mode interference in a two-moded waveguide, which is coupled adiabatically to the single-mode input and output strip waveguides. The single-mode input and output waveguides are connected via two Y-branches ( "'kJ- 1° branching angle ) with a two-moded intersection region. The ratio of the light powers in the single-mode output waveguides depends on wavelength . The two-mode interference within the two-moded center waveguide leads to an almost wavelength periodic transmission caracteristic . Dual-channel multiplexers/demultiplexers were fabricated by a charge controlled field assisted pottasium exchange in B-270 glass (Desag). The devices have a typical channel separation of 30 - 40 nm and a far-end crosstalk attenuation of better than 16 dB. The operation wavelength regions of the fabricated devices are 0.6 - 0.8 µm and 1.3 - 1.6 µm, respectively.

Continuous tuning of two-section, single-mode terahertz quantum-cascade lasers by fiber-coupled, near-infrared illumination

NASA Astrophysics Data System (ADS)

Hempel, Martin; Röben, Benjamin; Niehle, Michael; Schrottke, Lutz; Trampert, Achim; Grahn, Holger T.

2017-05-01

The dynamical tuning due to rear facet illumination of single-mode, terahertz (THz) quantum-cascade lasers (QCLs) which employ distributed feedback gratings are compared to the tuning of single-mode QCLs based on two-section cavities. The THz QCLs under investigation emit in the range of 3 to 4.7 THz. The tuning is achieved by illuminating the rear facet of the QCL with a fiber-coupled light source emitting at 777 nm. Tuning ranges of 5.0 and 11.9 GHz under continuous-wave and pulsed operation, respectively, are demonstrated for a single-mode, two-section cavity QCL emitting at about 3.1 THz, which exhibits a side-mode suppression ratio better than -25 dB.

On the Application of Inverse-Mode SiGe HBTs in RF Receivers for the Mitigation of Single-Event Transients

NASA Astrophysics Data System (ADS)

Song, Ickhyun; Cho, Moon-Kyu; Oakley, Michael A.; Ildefonso, Adrian; Ju, Inchan; Buchner, Stephen P.; McMorrow, Dale; Paki, Pauline; Cressler, John. D.

2017-05-01

Best practice in mitigation strategies for single-event transients (SETs) in radio-frequency (RF) receiver modules is investigated using a variety of integrated receivers utilizing inverse-mode silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs). The receivers were designed and implemented in a 130-nm SiGe BiCMOS technology platform. In general, RF switches, low-noise amplifiers (LNAs), and downconversion mixers utilizing inverse-mode SiGe HBTs exhibit less susceptibility to SETs than conventional RF designs, in terms of transient peaks and duration, at the cost of RF performance. Under normal RF operation, the SET-hardened switch is mainly effective in peak reduction, while the LNA and the mixer exhibit reductions in transient peaks as well as transient duration.

Slow light generation in single-mode rectangular core photonic crystal fiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Sandeep; Saini, Than Singh; Kumar, Ajeet, E-mail: ajeetdph@gmail.com

2016-05-06

In this paper, we have designed and analyzed a rectangular core photonic crystal fiber (PCF) in Tellurite material. For the designed photonics crystal fiber, we have calculated the values of confinement loss and effective mode area for different values of air filling fraction (d/Λ). For single mode operation of the designed photonic crystal fiber, we have taken d/Λ= 0.4 for the further calculation of stimulated Brillouin scattering based time delay. A maximum time delay of 158 ns has been achieved for input pump power of 39 mW. We feel the detailed theoretical investigations and simulations carried out in the study have themore » potential impact on the design and development of slow light-based photonic devices.« less

Single-mode SOA-based 1kHz-linewidth dual-wavelength random fiber laser.

PubMed

Xu, Yanping; Zhang, Liang; Chen, Liang; Bao, Xiaoyi

2017-07-10

Narrow-linewidth multi-wavelength fiber lasers are of significant interests for fiber-optic sensors, spectroscopy, optical communications, and microwave generation. A novel narrow-linewidth dual-wavelength random fiber laser with single-mode operation, based on the semiconductor optical amplifier (SOA) gain, is achieved in this work for the first time, to the best of our knowledge. A simplified theoretical model is established to characterize such kind of random fiber laser. The inhomogeneous gain in SOA mitigates the mode competition significantly and alleviates the laser instability, which are frequently encountered in multi-wavelength fiber lasers with Erbium-doped fiber gain. The enhanced random distributed feedback from a 5km non-uniform fiber provides coherent feedback, acting as mode selection element to ensure single-mode operation with narrow linewidth of ~1kHz. The laser noises are also comprehensively investigated and studied, showing the improvements of the proposed random fiber laser with suppressed intensity and frequency noises.

Single-Event Effect Performance of a Conductive-Bridge Memory EEPROM

NASA Technical Reports Server (NTRS)

Chen, Dakai; Wilcox, Edward; Berg, Melanie; Kim, Hak; Phan, Anthony; Figueiredo, Marco; Seidleck, Christina; LaBel, Kenneth

2015-01-01

We investigated the heavy ion single-event effect (SEE) susceptibility of the industry’s first stand-alone memory based on conductive-bridge memory (CBRAM) technology. The device is available as an electrically erasable programmable read-only memory (EEPROM). We found that single-event functional interrupt (SEFI) is the dominant SEE type for each operational mode (standby, dynamic read, and dynamic write/read). SEFIs occurred even while the device is statically biased in standby mode. Worst case SEFIs resulted in errors that filled the entire memory space. Power cycle did not always clear the errors. Thus the corrupted cells had to be reprogrammed in some cases. The device is also vulnerable to bit upsets during dynamic write/read tests, although the frequency of the upsets are relatively low. The linear energy transfer threshold for cell upset is between 10 and 20 megaelectron volts per square centimeter per milligram, with an upper limit cross section of 1.6 times 10(sup -11) square centimeters per bit (95 percent confidence level) at 10 megaelectronvolts per square centimeter per milligram. In standby mode, the CBRAM array appears invulnerable to bit upsets.

Single-mode dispersive waves and soliton microcomb dynamics

PubMed Central

Yi, Xu; Yang, Qi-Fan; Zhang, Xueyue; Yang, Ki Youl; Li, Xinbai; Vahala, Kerry

2017-01-01

Dissipative Kerr solitons are self-sustaining optical wavepackets in resonators. They use the Kerr nonlinearity to both compensate dispersion and offset optical loss. Besides providing insights into nonlinear resonator physics, they can be applied in frequency metrology, precision clocks, and spectroscopy. Like other optical solitons, the dissipative Kerr soliton can radiate power as a dispersive wave through a process that is the optical analogue of Cherenkov radiation. Dispersive waves typically consist of an ensemble of optical modes. Here, a limiting case is studied in which the dispersive wave is concentrated into a single cavity mode. In this limit, its interaction with the soliton induces hysteresis behaviour in the soliton's spectral and temporal properties. Also, an operating point of enhanced repetition-rate stability occurs through balance of dispersive-wave recoil and Raman-induced soliton-self-frequency shift. The single-mode dispersive wave can therefore provide quiet states of soliton comb operation useful in many applications. PMID:28332495

Adaptive frequency-domain equalization for the transmission of the fundamental mode in a few-mode fiber.

PubMed

Bai, Neng; Xia, Cen; Li, Guifang

2012-10-08

We propose and experimentally demonstrate single-carrier adaptive frequency-domain equalization (SC-FDE) to mitigate multipath interference (MPI) for the transmission of the fundamental mode in a few-mode fiber. The FDE approach reduces computational complexity significantly compared to the time-domain equalization (TDE) approach while maintaining the same performance. Both FDE and TDE methods are evaluated by simulating long-haul fundamental-mode transmission using a few-mode fiber. For the fundamental mode operation, the required tap length of the equalizer depends on the differential mode group delay (DMGD) of a single span rather than DMGD of the entire link.

Effects of diesel exhaust aftertreatment devices on concentrations and size distribution of aerosols in underground mine air.

PubMed

Bugarski, Aleksandar D; Schnakenberg, George H; Hummer, Ion A; Cauda, Emanuele; Janisko, Samuel I; Patts, Larry D

2009-09-01

Three types of uncatalyzed diesel particulate filter (DPF) systems, three types of high-temperature disposable filter elements (DFEs), and one diesel oxidation catalytic converter (DOC) were evaluated in underground mine conditions for their effects on the concentrations and size distributions of diesel aerosols. Those effects were compared with the effects of a standard muffler. The experimental work was conducted directly in an underground environment using a unique diesel laboratory developed in an underground experimental mine. The DPF systems reduced total mass of aerosols in the mine air approximately 10-fold for light-load and 20-fold or more for high-load test conditions. The DFEs offered similar reductions in aerosol mass concentrations. The efficiency of the new DFEs significantly increased with accumulation of operating time and buildup of diesel particulate matter in the porous structure of the filter elements. A single laundering process did not exhibit substantial effects on performance of the filter element The effectiveness of DPFs and DFEs in removing aerosols by number was strongly influenced by engine operating mode. The concentrations of nucleation mode aerosols in the mine air were found to be substantially higher for both DPFs and DFEs when the engine was operated at high-load modes than at low-load modes. The effects of the DOC on mass and number concentrations of aerosols in mine air were relatively minor when compared to those of the DPF and DFE systems.

Harmonic voltage excess problem test and analysis in UHV and EHV grid particular operation mode

NASA Astrophysics Data System (ADS)

Lv, Zhenhua; Shi, Mingming; Fei, Juntao

2018-02-01

The test and analysis of the power quality of some 1000kV UHV transmission lines and 500kV EHV transmission lines is carried out. It is found that there is harmonic voltage excess problems when the power supply of the UHV and EHV voltage line is single-ended or single-loop, the problem basically disappeared after the operation mode change, different operating conditions, the harmonic current has not been greatly affected, indicating that the harmonic voltage changes mainly caused by the system harmonic impedance. With the analysis of MATLAB Simulink system model, it can be seen that there are specific harmonic voltage excess in the system under the specific operating mode, which results in serious distortion of the specific harmonic voltage. Since such phenomena are found in 500kV and 1000kV systems, it is suggested that the test evaluation work should be done under the typical mode of operation in 500kV, 1000kV Planning and construction process to prevent the occurrence of serious distortion and the regional harmonic current monitoring and suppression work should be done.

Tunable multiwavelength Tm-doped fiber laser based on the multimode interference effect.

PubMed

Zhang, Peng; Wang, Tianshu; Ma, Wanzhuo; Dong, Keyan; Jiang, Huilin

2015-05-20

A simple multiwavelength Tm-doped fiber laser at the 2 μm band based on multimode interference (MMI) is proposed and experimentally demonstrated. In this scheme, a 4 m Tm-doped single-mode fiber is pumped by a 1568 nm laser, and a single-mode-multimode-single-mode (SMS) fiber structure is used as an MMI filter in which the multimode fiber is used to tune the laser. Laser operation of up to three wavelengths is obtained based on the MMI filter. The wavelengths can be tuned by adjusting the polarization controller and rotating the multimode fiber in the SMS structure, and the tuning region is about 24 nm, i.e., 1892-1916 nm. The side-mode suppression ratio of the laser is about 54 dB. The 3 dB linewidth is less than 0.04 nm. Peak fluctuation at each wavelength is analyzed, and the results show that the power fluctuation is less than 3 dB around the average power.

Single-Mode, High Repetition Rate, Compact Ho:YLF Laser for Space-Borne Lidar Applications

NASA Technical Reports Server (NTRS)

Bai, Yingxin; Yu, Jirong; Wong, Teh-Hwa; Chen, Songsheng; Petros, Mulugeta; Singh, Upendra N.

2014-01-01

A single transverse/longitudinal mode, compact Q-switched Ho:YLF laser has been designed and demonstrated for space-borne lidar applications. The pulse energy is between 34-40 mJ for 100-200 Hz operation. The corresponding peak power is >1 MW.

Single-mode operation of mushroom structure surface emitting lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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.

Tunable Q-switched erbium doped fiber laser based on metal transition oxide saturable absorber and refractive index characteristic of multimode interference effects

NASA Astrophysics Data System (ADS)

Mohammed, D. Z.; Khaleel, Wurood Abdulkhaleq; Al-Janabi, A. H.

2017-12-01

Ferro-oxide (Fe3O4) nanoparticles were used as a saturable absorber (SA) for a passively Q-switched erbium doped fiber laser (EDFL) with ring cavity. The Q-switching operation was achieved at a pump threshold of 80 mW. The proposed fiber laser produces stable pulses train of repetition rate ranging from 25 kHz to 80 kHz as the pump power increases from threshold to 342 mW. The minimum recorded pulse width was 2.7 μs at 342 mW. The C-band tunability operation was performed using single mode-multimode-single mode fiber (SM-MM-SM) structure. The laser exhibited a total tuning range of 7 nm, maximum sensitivity of 106.9 nm, optical signal to noise ratio (OSNR) of 38 dB and 3-dB linewidth of 0.06 nm.

978-nm square-wave in an all-fiber single-mode ytterbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Li, Shujie; Xu, Lixin; Gu, Chun

2018-01-01

A 978 nm single mode passively mode-locked all-fiber laser delivering square-wave pulses was demonstrated using a figure-8 cavity and a 75 cm commercial double-clad ytterbium-doped fiber. We found the three-level system near 978 nm was able to operate efficiently under clad pumping, simultaneously oscillation around 1030 nm well inhibited. The optimized nonlinear amplifying loop mirror made the mode locking stable and performed the square-pulses shaping. To the best of our knowledge, it is the first time to report the square-wave pulse fiber laser operating at 980 nm. The spectral width of the 978 mode-locked square pulses was about 4 nm, far greater than that of the mode-locked square pulses around 1060 nm reported before, which would be helpful to deeply understand the various square-wave pulses' natures and forming mechanisms. Compared with modulated single-mode or multimode 980 nm LDs, this kind of 980 nm square-wave sources having higher brightness, more steeper rising and falling edge and shorter pulse width, might have potential applications in pumping nanosecond ytterbium or erbium fiber lasers and amplifiers.

Laguerre-polynomial-weighted squeezed vacuum: generation and its properties of entanglement

NASA Astrophysics Data System (ADS)

Ye, Wei; Zhang, Kuizheng; Zhang, Haoliang; Xu, Xuexiang; Hu, Liyun

2018-02-01

We theoretically prepare a kind of two-mode entangled non-Gaussian state generated by combining quantum catalysis and parametric-down amplifier operated on the two-mode squeezing vacuum state. We then investigate the entanglement properties by examining Von Neumann entropy, EPR correlation, squeezing effect and the fidelity of teleportation. It is shown that only Von Neumann entropy can be enhanced by both single- and two-mode catalysis in a small squeezing region, while the other properties can be enhanced only by two-mode catalysis including symmetrical and asymmetrical cases. A comparison among these properties shows that the squeezing and the EPR correlation definitely lead to the improvement of both the entanglement and the fidelity, and the region of enhanced fidelity can be seen as a sub-region of the enhanced entanglement which indicates that the entanglement is not always beneficial for the fidelity. In addition, the effect of photon-loss after catalysis on the fidelity is considered and the symmetrical two-photon catalysis may present better behavior than the symmetrical single-photon case against the decoherence in a certain region.

High-Reliability Pump Module for Non-Planar Ring Oscillator Laser

NASA Technical Reports Server (NTRS)

Liu, Duncan T.; Qiu, Yueming; Wilson, Daniel W.; Dubovitsky, Serge; Forouhar, Siamak

2007-01-01

We propose and have demonstrated a prototype high-reliability pump module for pumping a Non-Planar Ring Oscillator (NPRO) laser suitable for space missions. The pump module consists of multiple fiber-coupled single-mode laser diodes and a fiber array micro-lens array based fiber combiner. The reported Single-Mode laser diode combiner laser pump module (LPM) provides a higher normalized brightness at the combined beam than multimode laser diode based LPMs. A higher brightness from the pump source is essential for efficient NPRO laser pumping and leads to higher reliability because higher efficiency requires a lower operating power for the laser diodes, which in turn increases the reliability and lifetime of the laser diodes. Single-mode laser diodes with Fiber Bragg Grating (FBG) stabilized wavelength permit the pump module to be operated without a thermal electric cooler (TEC) and this further improves the overall reliability of the pump module. The single-mode laser diode LPM is scalable in terms of the number of pump diodes and is capable of combining hundreds of fiber-coupled laser diodes. In the proof-of-concept demonstration, an e-beam written diffractive micro lens array, a custom fiber array, commercial 808nm single mode laser diodes, and a custom NPRO laser head are used. The reliability of the proposed LPM is discussed.

Experimental Performance of a Single-Mode Ytterbium-doped Fiber Ring Laser with Intracavity Modulator

NASA Technical Reports Server (NTRS)

Numata, Kenji; Camp, Jordan

2012-01-01

We have developed a linearly polarized Ytterbium-doped fiber ring laser with a single longitudinal mode output at 1064 run. A fiber-coupled intracavity phase modulator ensured mode-hop free operation and allowed fast frequency tuning. The fiber laser was locked with high stability to an iodine-stabilized laser, showing a frequency noise suppression of a factor approx 10 (exp 5) at 1 mHz

Parity-time–symmetric optoelectronic oscillator

PubMed Central

2018-01-01

An optoelectronic oscillator (OEO) is a hybrid microwave and photonic system incorporating an amplified positive feedback loop to enable microwave oscillation to generate a high-frequency and low–phase noise microwave signal. The low phase noise is ensured by the high Q factor of the feedback loop enabled by the use of a long and low-loss optical fiber. However, an OEO with a long fiber loop would have a small free spectral range, leading to a large number of closely spaced oscillation modes. To ensure single-mode oscillation, an ultranarrowband optical filter must be used, but such an optical filter is hard to implement and the stability is poor. Here, we use a novel concept to achieve single-mode oscillation without using an ultranarrowband optical filter. The single-mode operation is achieved based on parity-time (PT) symmetry by using two identical feedback loops, with one having a gain and the other having a loss of the same magnitude. The operation is analyzed theoretically and verified by an experiment. Stable single-mode oscillation at an ultralow phase noise is achieved without the use of an ultranarrowband optical filter. The use of PT symmetry in an OEO overcomes the long-existing mode-selection challenge that would greatly simplify the implementation of OEOs for ultralow–phase noise microwave generation. PMID:29888325

Design of energy-storage reactors for single-winding constant-frequency dc-to-dc converters operating in the discontinuous-reactor-current mode

NASA Technical Reports Server (NTRS)

Chen, D. Y.; Owen, H. A., Jr.; Wilson, T. G.

1980-01-01

This paper presents an algorithm and equations for designing the energy-storage reactor for dc-to-dc converters which are constrained to operate in the discontinuous-reactor-current mode. This design procedure applied to the three widely used single-winding configurations: the voltage step-up, the current step-up, and the voltage-or-current step-up converters. A numerical design example is given to illustrate the use of the design algorithm and design equations.

Effect of injection pressure on performance, emission, and combustion characteristics of diesel-acetylene-fuelled single cylinder stationary CI engine.

PubMed

Srivastava, Anmesh Kumar; Soni, Shyam Lal; Sharma, Dilip; Jain, Narayan Lal

2018-03-01

In this paper, the effect of injection pressure on the performance, emission, and combustion characteristics of a diesel-acetylene fuelled single cylinder, four-stroke, direct injection (DI) diesel engine with a rated power of 3.5 kW at a rated speed of 1500 rpm was studied. Experiments were performed in dual-fuel mode at four different injection pressures of 180, 190, 200, and 210 bar with a flow rate of 120 LPH of acetylene and results were compared with that of baseline diesel operation. Experimental results showed that highest brake thermal efficiency of 27.57% was achieved at injection pressure of 200 bar for diesel-acetylene dual-fuel mode which was much higher than 23.32% obtained for baseline diesel. Carbon monoxide, hydrocarbon, and smoke emissions were also measured and found to be lower, while the NO x emissions were higher at 200 bar in dual fuel mode as compared to those in other injection pressures in dual fuel mode and also for baseline diesel mode. Peak cylinder pressure, net heat release rate, and rate of pressure rise were also calculated and were higher at 200 bar injection pressure in dual fuel mode.

Injection-seeded operation of a Q-switched Cr,Tm,Ho:YAG laser

NASA Technical Reports Server (NTRS)

Henderson, Sammy W.; Hale, Charley P.; Magee, James R.

1991-01-01

Single-frequency Tm,Ho:YAG lasers operating near 2 microns are attractive sources for several applications including eye-safe laser radar (lidar) and pumping of AgGaSe2 parametric oscillators for efficient generation of longer wavelengths. As part of a program to develop a coherent lidar system using Tm,Ho:YAG lasers, a diode laser-pumped tunable CW single-longitudinal-mode (SLM) Cr:Tm:Ho:YAG laser and a flashlamp-pumped single-transverse-mode Q-switched Cr,Tm,Ho:YAG laser were developed. The CW laser was used to injection-seed the flashlamp-pumped laser, resulting in SLM Q-switched output. Operational characteristics of the CW and Q-switched lasers and injection-seeding results are reported.

Polarization Maintaining, Very-Large-Mode Area, Er Fiber Amplifier for High Energy Pulses at 1572.3 nm

NASA Technical Reports Server (NTRS)

Nicholoson, J. W.; DeSantolo, A.; Yan, M. F.; Wisk, P.; Mangan, B.; Puc, G.; Yu, A.; Stephen, M.

2016-01-01

We demonstrate the first polarization maintaining, very-large-mode-area Er-doped fiber amplifier with 1000 square micron effective area. The amplifier is core pumped by a Raman fiber laser and is used to generate single frequency one microsecond pulses with pulse energy of 368 microJoules, M2 of 1.1, and polarization extinction greater than 20 dB. The amplifier operates at 1572.3 nm, a wavelength useful for trace atmospheric CO2 detection.

Experimental analysis of the flow pattern of a pump turbine model in pump mode

NASA Astrophysics Data System (ADS)

Guggenberger, Mark; Senn, Florian; Jaberg, Helmut; Gehrer, Arno; Sallaberger, Manfred; Widmer, Christian

2016-11-01

Reversible pump turbines are the only means to store primary energy in an highly efficient way. Within a short time their operation can be switched between the different operational regimes thus enhancing the stabilization of the electric grid. These qualities in combination with the operation even at off-design conditions offer a high flexibility to the energy market. However, pump turbines pass through operational regimes where their behaviour becomes unstable. One of these effects occurs when the flowrate is decreased continuously down to a minimum. This point is the physical limitation of the pump operation and is very difficult to predict properly by numerical design without a model test. The purpose of the present study is to identify the fluid mechanical phenomena leading to the occurrence of instabilities of pump turbines in pump mode. A reduced scale model of a ANDRITZ pump turbine was installed on a 4-quadrant test rig for the experimental investigation of unstable conditions in pump mode. The performed measurements are based on the IEC60193-standard. Characteristic measurements at a single guide vane opening were carried out to get a detailed insight into the instabilities in pump mode. The interaction between runner and guide vane was analysed by Particle Image Velocimetry. Furthermore, high-speed visualizations of the suction side part load flow and the suction recirculation were performed. Like never before the flow pattern in the draft tube cone became visible with the help of a high-speed camera by intentionally caused cavitation effects which allow a qualitative view on the flow pattern in the draft tube cone. Suction recirculation is observed in form of single vortices separating from each runner blade and stretching into the draft tube against the main flow direction. To find an explanation for the flow phenomena responsible for the appearance of the unstable head curve also characteristic velocity distributions on the pressure side were combined with high-speed visualizations on the suction side of the pump turbine model. The results enhance the comprehension of the physical background leading to the instability and improve the numerical predictability of the instability in pump mode.

Silicon photonics WDM transmitter with single section semiconductor mode-locked laser

NASA Astrophysics Data System (ADS)

Müller, Juliana; Hauck, Johannes; Shen, Bin; Romero-García, Sebastian; Islamova, Elmira; Azadeh, Saeed Sharif; Joshi, Siddharth; Chimot, Nicolas; Moscoso-Mártir, Alvaro; Merget, Florian; Lelarge, François; Witzens, Jeremy

2015-04-01

We demonstrate a wavelength domain-multiplexed (WDM) optical link relying on a single section semiconductor mode-locked laser (SS-MLL) with quantum dash (Q-Dash) gain material to generate 25 optical carriers spaced by 60.8 GHz, as well as silicon photonics (SiP) resonant ring modulators (RRMs) to modulate individual optical channels. The link requires optical reamplification provided by an erbium-doped fiber amplifier (EDFA) in the system experiments reported here. Open eye diagrams with signal quality factors (Q-factors) above 7 are measured with a commercial receiver (Rx). For higher compactness and cost effectiveness, reamplification of the modulated channels with a semiconductor optical amplifier (SOA) operated in the linear regime is highly desirable. System and device characterization indicate compatibility with the latter. While we expect channel counts to be primarily limited by the saturation output power level of the SOA, we estimate a single SOA to support more than eight channels. Prior to describing the system experiments, component design and detailed characterization results are reported including design and characterization of RRMs, ring-based resonant optical add-drop multiplexers (RR-OADMs) and thermal tuners, S-parameters resulting from the interoperation of RRMs and RR-OADMs, and characterization of Q-Dash SS-MLLs reamplified with a commercial SOA. Particular emphasis is placed on peaking effects in the transfer functions of RRMs and RR-OADMs resulting from transient effects in the optical domain, as well as on the characterization of SS-MLLs in regard to relative intensity noise (RIN), stability of the modes of operation, and excess noise after reamplification.

Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

NASA Astrophysics Data System (ADS)

Chen, W. G.; Lou, S. Q.; Feng, S. C.; Wang, L. W.; Li, H. L.; Guo, T. Y.; Jian, S. S.

2009-11-01

Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

Slope efficiency over 30% single-frequency ytterbium-doped fiber laser based on Sagnac loop mirror filter.

PubMed

Yin, Mojuan; Huang, Shenghong; Lu, Baole; Chen, Haowei; Ren, Zhaoyu; Bai, Jintao

2013-09-20

A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064 nm with the obtained maximum output power of 32 mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were <2% and <0.1%, respectively, and the signal-to-noise ratio measured was around 60 dB.

Characterization of photomultiplier tubes in a novel operation mode for Secondary Emission Ionization Calorimetry

NASA Astrophysics Data System (ADS)

Tiras, E.; Dilsiz, K.; Ogul, H.; Southwick, D.; Bilki, B.; Wetzel, J.; Nachtman, J.; Onel, Y.; Winn, D.

2016-10-01

Hamamatsu single anode R7761 and multi-anode R5900-00-M16 Photomultiplier Tubes have been characterized for use in a Secondary Emission (SE) Ionization Calorimetry study. SE Ionization Calorimetry is a novel technique to measure electromagnetic shower particles in extreme radiation environments. The different operation modes used in these tests were developed by modifying the conventional PMT bias circuit. These modifications were simple changes to the arrangement of the voltage dividers of the baseboard circuits. The PMTs with modified bases, referred to as operating in SE mode, are used as an SE detector module in an SE calorimeter prototype, and placed between absorber materials (Fe, Cu, Pb, W, etc.). Here, the technical design of different operation modes, as well as the characterization measurements of both SE modes and the conventional PMT mode are reported.

Linear optics only allows every possible quantum operation for one photon or one port

NASA Astrophysics Data System (ADS)

Moyano-Fernández, Julio José; Garcia-Escartin, Juan Carlos

2017-01-01

We study the evolution of the quantum state of n photons in m different modes when they go through a lossless linear optical system. We show that there are quantum evolution operators U that cannot be built with linear optics alone unless the number of photons or the number of modes is equal to one. The evolution for single photons can be controlled with the known realization of any unitary proved by Reck, Zeilinger, Bernstein and Bertani. The evolution for a single mode corresponds to the trivial evolution in a phase shifter. We analyze these two cases and prove that any other combination of the number of photons and modes produces a Hilbert state too large for the linear optics system to give any desired evolution.

FIBER AND INTEGRATED OPTICS: Radiative losses in single-mode fiber waveguides with a depressed cladding

NASA Astrophysics Data System (ADS)

Belov, A. V.; Kurkov, Andrei S.; Miroshnichenko, S. I.; Semenov, V. A.

1989-11-01

A comparison was made of the calculated and measured radiative losses suffered by the fundamental and first higher modes in real waveguide structures with a depressed cladding. It was found that in determination of the operating range of single-mode waveguides with a depressed cladding it is essential to allow not only for the increase in the losses due to leaking of the fundamental HE11 mode at long wavelengths, but also for the shift of the cutoff wavelength of the first higher HE21 mode for shorter wavelengths.

Large tuning of narrow-beam terahertz plasmonic lasers operating at 78 K

DOE PAGES

Wu, Chongzhao; Jin, Yuan; Reno, John L.; ...

2016-12-19

A new tuning mechanism is demonstrated for single-mode metal-clad plasmonic lasers, in which the refractive-index of the laser’s surrounding medium affects the resonant-cavity mode in the same vein as the refractive-index of gain medium inside the cavity. Reversible, continuous, and mode-hop-free tuning of ~57 GHz is realized for single-mode narrow-beam terahertz plasmonic quantum-cascade lasers (QCLs), which is demonstrated at a much more practical temperature of 78 K. The tuning is based on post-process deposition/etching of a dielectric (silicon-dioxide) on a QCL chip that has already been soldered and wire-bonded onto a copper mount. This is a considerably larger tuning rangemore » compared to previously reported results for terahertz QCLs with directional far-field radiation patterns. The key enabling mechanism for tuning is a recently developed antenna-feedback scheme for plasmonic lasers, which leads to the generation of hybrid surface-plasmon-polaritons propagating outside the cavity of the laser with a large spatial extent. The effect of dielectric deposition on QCL’s characteristics is investigated in detail including that on maximum operating temperature, peak output power, and far-field radiation patterns. Single-lobed beam with low divergence (<7°) is maintained through the tuning range. The antenna-feedback scheme is ideally suited for modulation of plasmonic lasers and their sensing applications due to the sensitive dependence of spectral and radiative properties of the laser on its surrounding medium.« less

Discrete mode laser diodes for FTTH/PON applications up to 10 Gbit/s

NASA Astrophysics Data System (ADS)

O'Carroll, John; Phelan, Richard; Kelly, Brian; Byrne, Diarmuid; Latkowski, Sylwester; Anandarajah, Prince M.; Barry, Liam P.

2012-06-01

Discrete Mode Laser Diodes (DMLDs) present an economic approach with a focus on high volume manufacturability of single mode lasers using a single step fabrication process. We report on a DMLD designed for operation in the 1550 nm window with high Side Mode Suppression Ratio (SMSR) over a wide temperature tuning range of -20 °C < T < 95 °C. Direct modulation rates as high as 10 Gbit/s are demonstrated at both 1550 nm and 1310 nm. Transmission experiments were also carried out over single mode fibre at both wavelengths. Using dispersion pre-compensation transmission from 0 to 60 km is demonstrated at 1550 nm with a maximum power penalty measured at 60 km of 3.6 dB.

A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

PubMed

Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

2016-03-01

Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Single mode wavelength control of modulated AlGaAs lasers with external and internal etalon feedback

NASA Technical Reports Server (NTRS)

Maynard, William L.

1989-01-01

Single mode lasing without mode hops has been obtained for VSIS and CSP laser diodes with an external etalon attached to the laser's front facet for up to an 8 C range CW and a 4 C range pulsed, with .07 nm/C tuning. Tests of thin tapered-thickness (TTT) laser diodes show CW and pulsed single mode lasing over 10 C and 2 C ranges, respectively, with .08 nm/C tuning. An analysis of the TTT structure reveals the equivalent of an internal etalon. The time-resolved pulsed behavior for both types of lasers show single mode lasing within the proper temperature ranges with minor modes present only early in the optical pulse, if at all. The external etalon produces noticeable interference fringes in the farfield pattern, while those of the TTT lasers are smooth. Ongoing CW lifetest results indicate stability to within one longitudinal mode after a few hundred hours of operation, along with at least several thousand hours lifetime.

An integrated parity-time symmetric wavelength-tunable single-mode microring laser

PubMed Central

Liu, Weilin; Li, Ming; Guzzon, Robert S.; Norberg, Erik J.; Parker, John S.; Lu, Mingzhi; Coldren, Larry A.; Yao, Jianping

2017-01-01

Mode control in a laser cavity is critical for a stable single-mode operation of a ring laser. In this study we propose and experimentally demonstrate an electrically pumped parity-time (PT)-symmetric microring laser with precise mode control, to achieve wavelength-tunable single-mode lasing with an improved mode suppression ratio. The proposed PT-symmetric laser is implemented based on a photonic integrated circuit consisting of two mutually coupled active microring resonators. By incorporating multiple semiconductor optical amplifiers in the microring resonators, the PT-symmetry condition can be achieved by a precise manipulation of the interplay between the gain and loss in the two microring resonators, and the incorporation of phase modulators in the microring resonators enables continuous wavelength tuning. Single-mode lasing at 1,554.148 nm with a sidemode suppression ratio exceeding 36 dB is demonstrated and the lasing wavelength is continuously tunable from 1,553.800 to 1,554.020 nm. PMID:28497784

An integrated parity-time symmetric wavelength-tunable single-mode microring laser.

PubMed

Liu, Weilin; Li, Ming; Guzzon, Robert S; Norberg, Erik J; Parker, John S; Lu, Mingzhi; Coldren, Larry A; Yao, Jianping

2017-05-12

Mode control in a laser cavity is critical for a stable single-mode operation of a ring laser. In this study we propose and experimentally demonstrate an electrically pumped parity-time (PT)-symmetric microring laser with precise mode control, to achieve wavelength-tunable single-mode lasing with an improved mode suppression ratio. The proposed PT-symmetric laser is implemented based on a photonic integrated circuit consisting of two mutually coupled active microring resonators. By incorporating multiple semiconductor optical amplifiers in the microring resonators, the PT-symmetry condition can be achieved by a precise manipulation of the interplay between the gain and loss in the two microring resonators, and the incorporation of phase modulators in the microring resonators enables continuous wavelength tuning. Single-mode lasing at 1,554.148 nm with a sidemode suppression ratio exceeding 36 dB is demonstrated and the lasing wavelength is continuously tunable from 1,553.800 to 1,554.020 nm.

Single-longitudinal-mode Er:GGG microchip laser operating at 2.7  μm.

PubMed

You, Zhenyu; Wang, Yan; Xu, Jinlong; Zhu, Zhaojie; Li, Jianfu; Wang, Hongyan; Tu, Chaoyang

2015-08-15

We reported on a diode-end-pumped single-longitudinal-mode microchip laser using a 600-μm-thick Er:GGG crystal at ∼2.7  μm, generating a maximum output power of 50.8 mW and the maximum pulsed energy of 0.306 mJ, with repetition rates of pumping light of 300, 200, and 100 Hz, respectively. The maximum slope efficiency of the laser was 20.1%. The laser was operated in a single-longitudinal mode centered at about 2704 nm with a FWHM of 0.42 nm. The laser had a fundamental beam profile and the beam quality parameter M(2) was measured as 1.46. These results indicate that the Er:GGG microchip laser is a potential compact mid-infrared laser source.

Silicon Photonics Transmitter with SOA and Semiconductor Mode-Locked Laser.

PubMed

Moscoso-Mártir, Alvaro; Müller, Juliana; Hauck, Johannes; Chimot, Nicolas; Setter, Rony; Badihi, Avner; Rasmussen, Daniel E; Garreau, Alexandre; Nielsen, Mads; Islamova, Elmira; Romero-García, Sebastián; Shen, Bin; Sandomirsky, Anna; Rockman, Sylvie; Li, Chao; Sharif Azadeh, Saeed; Lo, Guo-Qiang; Mentovich, Elad; Merget, Florian; Lelarge, François; Witzens, Jeremy

2017-10-24

We experimentally investigate an optical link relying on silicon photonics transmitter and receiver components as well as a single section semiconductor mode-locked laser as a light source and a semiconductor optical amplifier for signal amplification. A transmitter based on a silicon photonics resonant ring modulator, an external single section mode-locked laser and an external semiconductor optical amplifier operated together with a standard receiver reliably supports 14 Gbps on-off keying signaling with a signal quality factor better than 7 for 8 consecutive comb lines, as well as 25 Gbps signaling with a signal quality factor better than 7 for one isolated comb line, both without forward error correction. Resonant ring modulators and Germanium waveguide photodetectors are further hybridly integrated with chip scale driver and receiver electronics, and their co-operability tested. These experiments will serve as the basis for assessing the feasibility of a silicon photonics wavelength division multiplexed link relying on a single section mode-locked laser as a multi-carrier light source.

Long-wavelength (1.3-1.5 micron) quantum dot lasers based on GaAs

NASA Astrophysics Data System (ADS)

Kovsh, Alexey R.; Ledentsov, Nikolai N.; Mikhrin, Sergei S.; Zhukov, Alexey E.; Livshits, Daniil A.; Maleev, Nikolay A.; Maximov, Mikhail V.; Ustinov, Victor M.; Gubenko, Alexey E.; Gadjiev, Igor M.; Portnoi, Efim L.; Wang, Jyh Shyang; Chi, Jim Y.; Ouyang, Donald N.; Bimberg, Dieter; Lott, James A.

2004-06-01

The molecular beam epitaxy of self-assembled quantum dots (QDs) has reached a level such that the principal advantages of QD lasers can now be fully realized. We overview the most important recent results achieved to date including excellent device performance of 1.3 μm broad area and ridge waveguide lasers (Jth<150A/cm2, Ith=1.4 mA, differential efficiency above 70%, CW 300 mW single lateral mode operation), suppression of non-linearity of QD lasers, which results to improved beam quality, reduced wavelength chirp and sensitivity to optical feedback. Effect of suppression of side wall recombination in QD lasers is also described. These effects give a possibility to further improve and simplify processing and fabrication of laser modules targeting their cost reduction. Recent realization of 2 mW single mode CW operation of QD VCSEL with all-semiconductor DBR is also presented. Long-wavelength QD lasers are promising candidate for mode-locking lasers for optical computer application. Very recently 1.7-ps-wide pulses at repetition rate of 20 GHz were obtained on mode-locked QD lasers with clear indication of possible shortening of pulse width upon processing optimization. First step of unification of laser technology for telecom range with QD-lasers grown on GaAs has been done. Lasing at 1.5 μm is achieved with threshold current density of 0.8 kA/cm2 and pulsed output power 7W.

Fiber Grating Coupled Light Source Capable of Tunable, Single Frequency Operation

NASA Technical Reports Server (NTRS)

Krainak, Michael A. (Inventor); Duerksen, Gary L. (Inventor)

2001-01-01

Fiber Bragg grating coupled light sources can achieve tunable single-frequency (single axial and lateral spatial mode) operation by correcting for a quadratic phase variation in the lateral dimension using an aperture stop. The output of a quasi-monochromatic light source such as a Fabry Perot laser diode is astigmatic. As a consequence of the astigmatism, coupling geometries that accommodate the transverse numerical aperture of the laser are defocused in the lateral dimension, even for apsherical optics. The mismatch produces the quadratic phase variation in the feedback along the lateral axis at the facet of the laser that excites lateral modes of higher order than the TM(sub 00). Because the instability entails excitation of higher order lateral submodes, single frequency operation also is accomplished by using fiber Bragg gratings whose bandwidth is narrower than the submode spacing. This technique is particularly pertinent to the use of lensed fiber gratings in lieu of discrete coupling optics. Stable device operation requires overall phase match between the fed-back signal and the laser output. The fiber Bragg grating acts as a phase-preserving mirror when the Bragg condition is met precisely. The phase-match condition is maintained throughout the fiber tuning range by matching the Fabry-Perot axial mode wavelength to the passband center wavelength of the Bragg grating.

Startup and mode competition in a 420 GHz gyrotron

NASA Astrophysics Data System (ADS)

Qixiang Zhao, A.; Sheng Yu, B.; Tianzhong Zhang, C.

2017-09-01

In the experiments of a 420 GHz second-harmonic gyrotron, it is found that the electron beam voltage and current ranges for single mode operation of TE17.4 are slightly narrower than those in the simulation. To explain this phenomenon, the startup scenario has been investigated with special emphasis on mode competition. The calculations indicate that the decreases of the operating ranges are caused by the voltage overshoot in the startup scenario.

High power continuous operation of a widely tunable quantum cascade laser with an integrated amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slivken, S.; Sengupta, S.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu

2015-12-21

Wide electrical tuning and high continuous output power is demonstrated from a single mode quantum cascade laser emitting at a wavelength near 4.8 μm. This is achieved in a space efficient manner by integrating an asymmetric sampled grating distributed feedback tunable laser with an optical amplifier. An initial demonstration of high peak power operation in pulsed mode is demonstrated first, with >5 W output over a 270 nm (113 cm{sup −1}) spectral range. Refinement of the geometry leads to continuous operation with a single mode spectral coverage of 300 nm (120 cm{sup −1}) and a maximum continuous power of 1.25 W. The output beam is shown tomore » be nearly diffraction-limited, even at high amplifier current.« less

New Three-Mode Squeezing Operators Gained via Tripartite Entangled State Representation

NASA Astrophysics Data System (ADS)

Jiang, Nian-Quan; Fan, Hong-Yi

2008-01-01

We show that the Agarwal Simon representation of single-mode squeezed states can be generalized to find new form of three-mode squeezed states. We use the tripartite entangled state representations |p,y,z> and |x,u,v> to realize this goal.

Low-cost, single-mode diode-pumped Cr:Colquiriite lasers.

PubMed

Demirbas, Umit; Li, Duo; Birge, Jonathan R; Sennaroglu, Alphan; Petrich, Gale S; Kolodziejski, Leslie A; Kaertner, Franz X; Fujimoto, James G

2009-08-03

We present three Cr3+:Colquiriite lasers as low-cost alternatives to Ti:Sapphire laser technology. Single-mode laser diodes, which cost only $150 each, were used as pump sources. In cw operation, with approximately 520 mW of absorbed pump power, up to 257, 269 and 266 mW of output power and slope efficiencies of 53%, 62% and 54% were demonstrated for Cr:LiSAF, Cr:LiSGaF and Cr:LiCAF, respectively. Record cw tuning ranges from 782 to 1042 nm for Cr:LiSAF, 777 to 977 nm for Cr:LiSGaF, and 754 to 871 nm for Cr:LiCAF were demonstrated. In cw mode-locking experiments using semiconductor saturable absorber mirrors at 800 and 850 nm, Cr:Colquiriite lasers produced approximately 50-100 fs pulses with approximately 1-2.5 nJ pulse energies at approximately 100 MHz repetition rate. Electrical-to-optical conversion efficiencies of 8% in mode-locked operation and 12% in cw operation were achieved.

SPM and XPM crosstalk in WDM systems with DRA: Channel spacing and attenuation effects

NASA Astrophysics Data System (ADS)

Morsy, Emadeldeen; Fayed, Heba A.; Abd El Aziz, Ahmed; Aly, Moustafa H.

2018-06-01

This paper presents a theoretical analysis of a closed formula for nonlinear crosstalk due to self-phase modulation (SPM) and cross phase modulation (XPM) in wavelength division multiplexing (WDM) systems. The influence of channel spacing and attenuation on the system behavior is modeled and investigated. The system under consideration is a standard single-mode fiber (SSMF) with a single-span distributed Raman amplifier (DRA) and is operating at 100 Gbps.

Single-Photon-Sensitive HgCdTe Avalanche Photodiode Detector

NASA Technical Reports Server (NTRS)

Huntington, Andrew

2013-01-01

The purpose of this program was to develop single-photon-sensitive short-wavelength infrared (SWIR) and mid-wavelength infrared (MWIR) avalanche photodiode (APD) receivers based on linear-mode HgCdTe APDs, for application by NASA in light detection and ranging (lidar) sensors. Linear-mode photon-counting APDs are desired for lidar because they have a shorter pixel dead time than Geiger APDs, and can detect sequential pulse returns from multiple objects that are closely spaced in range. Linear-mode APDs can also measure photon number, which Geiger APDs cannot, adding an extra dimension to lidar scene data for multi-photon returns. High-gain APDs with low multiplication noise are required for efficient linear-mode detection of single photons because of APD gain statistics -- a low-excess-noise APD will generate detectible current pulses from single photon input at a much higher rate of occurrence than will a noisy APD operated at the same average gain. MWIR and LWIR electron-avalanche HgCdTe APDs have been shown to operate in linear mode at high average avalanche gain (M > 1000) without excess multiplication noise (F = 1), and are therefore very good candidates for linear-mode photon counting. However, detectors fashioned from these narrow-bandgap alloys require aggressive cooling to control thermal dark current. Wider-bandgap SWIR HgCdTe APDs were investigated in this program as a strategy to reduce detector cooling requirements.

An Assessment of Reduced Crew and Single Pilot Operations in Commercial Transport Aircraft Operations

NASA Technical Reports Server (NTRS)

Bailey, Randall E.; Kramer, Lynda J.; Kennedy, Kellie D.; Stephens, Chad L.; Etherington, Timothy J.

2017-01-01

Future reduced crew operations or even single pilot operations for commercial airline and on-demand mobility applications are an active area of research. These changes would reduce the human element and thus, threaten the precept that "a well-trained and well-qualified pilot is the critical center point of aircraft systems safety and an integral safety component of the entire commercial aviation system." NASA recently completed a pilot-in-the-loop high fidelity motion simulation study in partnership with the Federal Aviation Administration (FAA) attempting to quantify the pilot's contribution to flight safety during normal flight and in response to aircraft system failures. Crew complement was used as the experiment independent variable in a between-subjects design. These data show significant increases in workload for single pilot operations, compared to two-crew, with subjective assessments of safety and performance being significantly degraded as well. Nonetheless, in all cases, the pilots were able to overcome the failure mode effects in all crew configurations. These data reflect current-day flight deck equipage and help identify the technologies that may improve two-crew operations and/or possibly enable future reduced crew and/or single pilot operations.

Economical launching and accelerating control strategy for a single-shaft parallel hybrid electric bus

NASA Astrophysics Data System (ADS)

Yang, Chao; Song, Jian; Li, Liang; Li, Shengbo; Cao, Dongpu

2016-08-01

This paper presents an economical launching and accelerating mode, including four ordered phases: pure electrical driving, clutch engagement and engine start-up, engine active charging, and engine driving, which can be fit for the alternating conditions and improve the fuel economy of hybrid electric bus (HEB) during typical city-bus driving scenarios. By utilizing the fast response feature of electric motor (EM), an adaptive controller for EM is designed to realize the power demand during the pure electrical driving mode, the engine starting mode and the engine active charging mode. Concurrently, the smoothness issue induced by the sequential mode transitions is solved with a coordinated control logic for engine, EM and clutch. Simulation and experimental results show that the proposed launching and accelerating mode and its control methods are effective in improving the fuel economy and ensure the drivability during the fast transition between the operation modes of HEB.

High-power, cladding-pumped all-fiber laser with selective transverse mode generation property.

PubMed

Li, Lei; Wang, Meng; Liu, Tong; Leng, Jinyong; Zhou, Pu; Chen, Jinbao

2017-06-10

We demonstrate, to the best of our knowledge, the first cladding-pumped all-fiber oscillator configuration with selective transverse mode generation based on a mode-selective fiber Bragg grating pair. Operating in the second-order (LP 11 ) mode, maximum output power of 4.2 W is obtained with slope efficiency of about 38%. This is the highest reported output power of single higher-order transverse mode generation in an all-fiber configuration. The intensity distribution profile and spectral evolution have also been investigated in this paper. Our work suggests the potential of realizing higher power with selective transverse mode operation based on a mode-selective fiber Bragg grating pair.

Optimal entangling operations between deterministic blocks of qubits encoded into single photons

NASA Astrophysics Data System (ADS)

Smith, Jake A.; Kaplan, Lev

2018-01-01

Here, we numerically simulate probabilistic elementary entangling operations between rail-encoded photons for the purpose of scalable universal quantum computation or communication. We propose grouping logical qubits into single-photon blocks wherein single-qubit rotations and the controlled-not (cnot) gate are fully deterministic and simple to implement. Interblock communication is then allowed through said probabilistic entangling operations. We find a promising trend in the increasing probability of successful interblock communication as we increase the number of optical modes operated on by our elementary entangling operations.

Analysis of deterministic swapping of photonic and atomic states through single-photon Raman interaction

NASA Astrophysics Data System (ADS)

Rosenblum, Serge; Borne, Adrien; Dayan, Barak

2017-03-01

The long-standing goal of deterministic quantum interactions between single photons and single atoms was recently realized in various experiments. Among these, an appealing demonstration relied on single-photon Raman interaction (SPRINT) in a three-level atom coupled to a single-mode waveguide. In essence, the interference-based process of SPRINT deterministically swaps the qubits encoded in a single photon and a single atom, without the need for additional control pulses. It can also be harnessed to construct passive entangling quantum gates, and can therefore form the basis for scalable quantum networks in which communication between the nodes is carried out only by single-photon pulses. Here we present an analytical and numerical study of SPRINT, characterizing its limitations and defining parameters for its optimal operation. Specifically, we study the effect of losses, imperfect polarization, and the presence of multiple excited states. In all cases we discuss strategies for restoring the operation of SPRINT.

Demonstration of enhanced side-mode suppression in metal-filled photonic crystal vertical cavity lasers.

PubMed

Griffin, Benjamin G; Arbabi, Amir; Peun Tan, Meng; Kasten, Ansas M; Choquette, Kent D; Goddard, Lynford L

2013-06-01

Previously reported simulations have suggested that depositing thin layers of metal over the surface of a single-mode, etched air hole photonic crystal (PhC) vertical-cavity surface-emitting laser (VCSEL) could potentially improve the laser's side-mode suppression ratio by introducing additional losses to the higher-order modes. This work demonstrates the concept by presenting the results of a 30 nm thin film of Cr deposited on the surface of an implant-confined PhC VCSEL. Both experimental measurements and simulation results are in agreement showing that the single-mode operation is improved at the same injection current ratio relative to threshold.

Low-NA single-mode LMA photonic crystal rod fiber amplifier

NASA Astrophysics Data System (ADS)

Alkeskjold, Thomas Tanggaard; Laurila, Marko; Scolari, Lara; Broeng, Jes

2011-02-01

Enabling Single-Mode (SM) operation in Large-Mode-Area (LMA) fiber amplifiers and lasers is critical, since a SM output ensures high beam quality and excellent pointing stability. In this paper, we demonstrate and test a new design approach for achieving ultra-low NA SM rod fibers by using a spatially Distributed Mode Filter (DMF). This approach achieves SM performance in a short and straight rod fiber and allows preform tolerances to be compensated during draw. A low-NA SM rod fiber amplifier having a mode field diameter of ~60μm at 1064nm and a pump absorption of 27dB/m at 976nm is demonstrated.

Innovative Multi-Environment, Multimode Thermal Control System

NASA Technical Reports Server (NTRS)

Singh, Bhim S.; Hasan, Mohammad H.

2007-01-01

Innovative multi-environment multimode thermal management architecture has been described that is capable of meeting widely varying thermal control requirements of various exploration mission scenarios currently under consideration. The proposed system is capable of operating in a single-phase or two-phase mode rejecting heat to the colder environment, operating in a two-phase mode with heat pump for rejecting heat to a warm environment, as well as using evaporative phasechange cooling for the mission phases where the radiator is incapable of rejecting the required heat. A single fluid loop can be used internal and external to the spacecraft for the acquisition, transport and rejection of heat by the selection of a working fluid that meets NASA safety requirements. Such a system may not be optimal for each individual mode of operation but its ability to function in multiple modes may permit global optimization of the thermal control system. The architecture also allows flexibility in partitioning of components between the various Constellation modules to take advantage of operational requirements in various modes consistent with the mission needs. Preliminary design calculations using R-134 as working fluid show the concept to be feasible to meet the heat rejection requirements that are representative of the Crew Exploration Vehicle and Lunar Access Module for nominal cases. More detailed analyses to establish performance under various modes and environmental conditions are underway.

Long-wavelength vertical-cavity laser research at Gore

NASA Astrophysics Data System (ADS)

Jayaraman, Vijaysekhar; Geske, J. C.; MacDougal, Michael H.; Peters, Frank H.; Lowes, Ted D.; Char, T. T.; Van Deusen, Dale R.; Goodnough, T.; Donhowe, Mark N.; Kilcoyne, Sean P.; Welch, David J.

1999-04-01

Vertical cavity surface emitting lasers (VCSELs) operating near 1310 or 1550 nm have been the subject of intensive research by multiple groups for several years. In the past year at Gore, we have demonstrated the first 1300 nm VCSELs which operate with useful power, high modulation rate, and low voltage over the commercial temperature range of 0 - 70 degree(s)C. These results have been achieved using a new structure in which an 850 nm VCSEL optical pump is integrated with the 1300 nm VCSEL. Electrical drive is applied to the 850 nm pump, and 1300 nm light is emitted from the integrated structure. This approach has resulted in over a milliwatt of single transverse mode power at room temperature, and several hundred microwatts of single transverse mode power at 70 degree(s)C. In addition, these devices demonstrate multi-gigabit modulation and excellent coupling efficiency to single-mode fiber.

Implementation of fuzzy-sliding mode based control of a grid connected photovoltaic system.

PubMed

Menadi, Abdelkrim; Abdeddaim, Sabrina; Ghamri, Ahmed; Betka, Achour

2015-09-01

The present work describes an optimal operation of a small scale photovoltaic system connected to a micro-grid, based on both sliding mode and fuzzy logic control. Real time implementation is done through a dSPACE 1104 single board, controlling a boost chopper on the PV array side and a voltage source inverter (VSI) on the grid side. The sliding mode controller tracks permanently the maximum power of the PV array regardless of atmospheric condition variations, while The fuzzy logic controller (FLC) regulates the DC-link voltage, and ensures via current control of the VSI a quasi-total transit of the extracted PV power to the grid under a unity power factor operation. Simulation results, carried out via Matlab-Simulink package were approved through experiment, showing the effectiveness of the proposed control techniques. Copyright © 2015. Published by Elsevier Ltd.

Photonic bandgap single-mode optical fibre with ytterbium-doped silica glass core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egorova, O N; Semenov, S L; Vel'miskin, V V

2011-01-24

A photonic bandgap fibre with an ytterbium-doped silica glass core is fabricated and investigated. The possibility of implementing single-mode operation of such fibres in a wide spectral range at a large (above 20 {mu}m) mode field diameter makes them promising for fibre lasers and amplifiers. To ensure a high quality of the beam emerging from the fibre, particular attention is paid to increasing the optical homogeneity of the ytterbium-doped core glass. (optical fibres)

Scheme for generating distillation-favorable continuous-variable entanglement via three concurrent parametric down-conversions in a single χ⁽²⁾ nonlinear photonic crystal.

PubMed

Gong, Yan-Xiao; Zhang, ShengLi; Xu, P; Zhu, S N

2016-03-21

We propose to generate a single-mode-squeezing two-mode squeezed vacuum state via a single χ⁽²⁾ nonlinear photonic crystal. The state is favorable for existing Gaussian entanglement distillation schemes, since local squeezing operations can enhance the final entanglement and the success probability. The crystal is designed for enabling three concurrent quasi-phase-matching parametric-down conversions, and hence relieves the auxiliary on-line bi-side local squeezing operations. The compact source opens up a way for continuous-variable quantum technologies and could find more potential applications in future large-scale quantum networks.

Dynamics of ultra-broadband terahertz quantum cascade lasers for comb operation.

PubMed

Li, Hua; Laffaille, Pierre; Gacemi, Djamal; Apfel, Marc; Sirtori, Carlo; Leonardon, Jeremie; Santarelli, Giorgio; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jerome; Hänsel, Wolfgang; Holzwarth, Ronald; Barbieri, Stefano

2015-12-28

We present an experimental investigation of the multimode dynamics and the coherence of terahertz quantum cascade lasers emitting over a spectral bandwidth of ~1THz. The devices are studied in free-running and under direct RF modulation. Depending on the pump current we observe different regimes of operation, where RF spectra displaying single and multiple narrow beat-note signals alternate with spectra showing a single beat-note characterized by an intense phase-noise, extending over a bandwidth up to a few GHz. We investigate the relation between this phase-noise and the dynamics of the THz modes through the electro-optic sampling of the laser emission. We find that when the phase-noise is large, the laser operates in an unstable regime where the lasing modes are incoherent. Under RF modulation of the laser current such instability can be suppressed and the modes coherence recovered, while, simultaneously, generating a strong broadening of the THz emission spectrum.

A multi-core fiber based interferometer for high temperature sensing

NASA Astrophysics Data System (ADS)

Zhou, Song; Huang, Bo; Shu, Xuewen

2017-04-01

In this paper, we have verified and implemented a Mach-Zehnder interferometer based on seven-core fiber for high temperature sensing application. This proposed structure is based on a multi-mode-multi-core-multi-mode fiber structure sandwiched by a single mode fiber. Between the single-mode and multi-core fiber, a 3 mm long multi-mode fiber is formed for lead-in and lead-out light. The basic operation principle of this device is the use of multi-core modes, single-mode and multi-mode interference coupling is also utilized. Experimental results indicate that this interferometer sensor is capable of accurate measurements of temperatures up to 800 °C, and the temperature sensitivity of the proposed sensor is as high as 170.2 pm/°C, which is much higher than the current existing MZI based temperature sensors (109 pm/°C). This type of sensor is promising for practical high temperature applications due to its advantages including high sensitivity, simple fabrication process, low cost and compactness.

Few-mode fiber based Raman distributed temperature sensing.

PubMed

Wang, Meng; Wu, Hao; Tang, Ming; Zhao, Zhiyong; Dang, Yunli; Zhao, Can; Liao, Ruolin; Chen, Wen; Fu, Songnian; Yang, Chen; Tong, Weijun; Shum, Perry Ping; Liu, Deming

2017-03-06

We proposed and experimentally demonstrated a few mode fiber (FMF) based Raman distributed temperature sensor (RDTS) to extend the sensing distance with enhanced signal-to-noise ratio (SNR) of backscattered anti-Stokes spontaneous Raman scattering. Operating in the quasi-single mode (QSM) with efficient fundamental mode excitement, the FMF allows much larger input pump power before the onset of stimulated Raman scattering compared with the standard single mode fiber (SSMF) and mitigates the detrimental differential mode group delay (DMGD) existing in the conventional multimode fiber (MMF) based RDTS system. Comprehensive theoretical analysis has been conducted to reveal the benefits of RDTS brought by QSM operated FMFs with the consideration of geometric/optical parameters of different FMFs. The measurement uncertainty of FMF based scheme has also been evaluated. Among fibers being investigated and compared (SSMF, 2-mode and 4-mode FMFs, respectively), although an ideal 4-mode FMF based RDTS has the largest SNR enhancement in principle, real fabrication imperfections and larger splicing loss degrade its performance. While the 2-mode FMF based system outperforms in longer distance measurement, which agrees well with the theoretical calculations considering real experimental parameters. Using the conventional RDTS hardware, a 30-ns single pulse at 1550nm has been injected as the pump; the obtained temperature resolutions at 20km distance are estimated to be about 10°C, 7°C and 6°C for the SSMF, 4-mode and 2-mode FMFs, respectively. About 4°C improvement over SSMF on temperature resolution at the fiber end with 3m spatial resolution within 80s measuring time over 20km 2-mode FMFs have been achieved.

Resonant and resistive dual-mode uncooled infrared detectors toward expanded dynamic range and high linearity

NASA Astrophysics Data System (ADS)

Li, Xin; Liang, Ji; Zhang, Hongxiang; Yang, Xing; Zhang, Hao; Pang, Wei; Zhang, Menglun

2017-06-01

This paper reports an uncooled infrared (IR) detector based on a micromachined piezoelectric resonator operating in resonant and resistive dual-modes. The two sensing modes achieved IR responsivities of 2.5 Hz/nW and 900 μdB/nW, respectively. Compared with the single mode operation, the dual-mode measurement improves the limit of detection by two orders of magnitude and meanwhile maintains high linearity and responsivity in a higher IR intensity range. A combination of the two sensing modes compensates for its own shortcomings and provides a much larger dynamic range, and thus, a wider application field of the proposed detector is realized.

Compactly packaged monolithic four-wavelength VCSEL array with 100-GHz wavelength spacing for future-proof mobile fronthaul transport.

PubMed

Lee, Eun-Gu; Mun, Sil-Gu; Lee, Sang Soo; Lee, Jyung Chan; Lee, Jong Hyun

2015-01-12

We report a cost-effective transmitter optical sub-assembly using a monolithic four-wavelength vertical-cavity surface-emitting laser (VCSEL) array with 100-GHz wavelength spacing for future-proof mobile fronthaul transport using the data rate of common public radio interface option 6. The wavelength spacing is achieved using selectively etched cavity control layers and fine current adjustment. The differences in operating current and output power for maintaining the wavelength spacing of four VCSELs are <1.4 mA and <1 dB, respectively. Stable operation performance without mode hopping is observed, and error-free transmission under direct modulation is demonstrated over a 20-km single-mode fiber without any dispersion-compensation techniques.

Polymer Piezoelectric Energy Harvesters for Low Wind Speed

DOE PAGES

Li, Dong Jun; Hong, Seungbum; Gu, Shiyuan; ...

2014-01-06

We fabricated polymer piezoelectric energy harvesters (PEHs) that can generate electric power at wind speed of less than 4.7 m/s due to their high sensitivity to wind. In order to optimize their operating conditions, we evaluated three distinct PEH operation modes under the boundary conditions of single-side clamping. We found that a PEH connected to an external load of 120 kΩ shows the largest output power of 0.98 μW at 3.9m/s, with wind incident on its side (mode I). We attribute this result to large bending and torsion involved in this operation mode.

Wide-range radiation dose monitor

DOEpatents

Kopp, Manfred K.

1986-01-01

A radiation dose-rate monitor is provided which operates in a conventional linear mode for radiation in the 0 to 0.5 R/h range and utilizes a nonlinear mode of operation for sensing radiation from 0.5 R/h to over 500 R/h. The nonlinear mode is achieved by a feedback circuit which adjusts the high voltage bias of the proportional counter, and hence its gas gain, in accordance with the amount of radiation being monitored. This allows compression of readout onto a single scale over the range of 0 to greater than 500 R/h without scale switching operations.

Wide-range radiation dose monitor

DOEpatents

Kopp, M.K.

1984-09-20

A radiation dose-rate monitor is provided which operates in a conventional linear mode for radiation in the 0 to 0.5 R/h range and utilizes a nonlinear mode of operation for sensing radiation from 0.5 R/h to over 500 R/h. The nonlinear mode is achieved by a feedback circuit which adjusts the high voltage bias of the proportional counter, and hence its gas gain, in accordance with the amount of radiation being monitored. This allows compression of readout onto a single scale over the range of 0 to greater than 500 R/h without scale switching operations.

On electron heating in a low pressure capacitively coupled oxygen discharge

NASA Astrophysics Data System (ADS)

Gudmundsson, J. T.; Snorrason, D. I.

2017-11-01

We use the one-dimensional object-oriented particle-in-cell Monte Carlo collision code oopd1 to explore the charged particle densities, the electronegativity, the electron energy probability function, and the electron heating mechanism in a single frequency capacitively coupled oxygen discharge, when the applied voltage amplitude is varied. We explore discharges operated at 10 mTorr, where electron heating within the plasma bulk (the electronegative core) dominates, and at 50 mTorr, where sheath heating dominates. At 10 mTorr, the discharge is operated in a combined drift-ambipolar and α-mode, and at 50 mTorr, it is operated in the pure α-mode. At 10 mTorr, the effective electron temperature is high and increases with increased driving voltage amplitude, while at 50 mTorr, the effective electron temperature is much lower, in particular, within the electronegative core, where it is roughly 0.2-0.3 eV, and varies only a little with the voltage amplitude.

Integrating multimodal transport into cellulosic biofuel supply chain design under feedstock seasonality with a case study based on California.

PubMed

Xie, Fei; Huang, Yongxi; Eksioglu, Sandra

2014-01-01

A multistage, mixed integer programing model was developed that fully integrates multimodal transport into the cellulosic biofuel supply chain design under feedstock seasonality. Three transport modes are considered: truck, single railcar, and unit train. The goal is to minimize the total cost for infrastructure, feedstock harvesting, biofuel production, and transportation. Strategic decisions including the locations and capacities of transshipment hubs, biorefineries, and terminals and tactical decisions on system operations are optimized in an integrated manner. When the model was implemented to a case study of cellulosic ethanol production in California, it was found that trucks are convenient for short-haul deliveries while rails are more effective for long-haul transportation. Taking the advantage of these benefits, the multimodal transport provides more cost effective solutions than the single-mode transport (truck). Copyright © 2013 Elsevier Ltd. All rights reserved.

Low-sensitivity, low-bounce, high-linearity current-controlled oscillator suitable for single-supply mixed-mode instrumentation system.

PubMed

Hwang, Yuh-Shyan; Kung, Che-Min; Lin, Ho-Cheng; Chen, Jiann-Jong

2009-02-01

A low-sensitivity, low-bounce, high-linearity current-controlled oscillator (CCO) suitable for a single-supply mixed-mode instrumentation system is designed and proposed in this paper. The designed CCO can be operated at low voltage (2 V). The power bounce and ground bounce generated by this CCO is less than 7 mVpp when the power-line parasitic inductance is increased to 100 nH to demonstrate the effect of power bounce and ground bounce. The power supply noise caused by the proposed CCO is less than 0.35% in reference to the 2 V supply voltage. The average conversion ratio KCCO is equal to 123.5 GHz/A. The linearity of conversion ratio is high and its tolerance is within +/-1.2%. The sensitivity of the proposed CCO is nearly independent of the power supply voltage, which is less than a conventional current-starved oscillator. The performance of the proposed CCO has been compared with the current-starved oscillator. It is shown that the proposed CCO is suitable for single-supply mixed-mode instrumentation systems.

Post-inscription tuning of multicore fiber Bragg gratings

NASA Astrophysics Data System (ADS)

Lindley, Emma Y.; Min, Seong-sik; Leon-Saval, Sergio G.; Bland-Hawthorn, Joss

2016-07-01

Fiber Bragg gratings are used in astronomy for their ability to suppress narrow atmospheric emission lines of temporally varying brightness before the light is dispersed. These gratings can only operate in a single-mode fiber as the suppressed wavelength depends on mode velocity in the core. Recent experiments with fibers containing multiple single-moded cores have demonstrated the potential for inscribing identical gratings across all cores in a single pass. We have already improved the uniformity of gratings in 7-core fibers via modifications to the writing process; further progress can be achieved by tuning the gratings of the outer and inner cores relative to one another. Our eventual goal is to make the entire fiber suppress one wavelength to a depth of 30 dB or greater. By coating the fiber in a heat-conductive material with a high expansion coefficient, we can examine the effects of temperature and strain on the spectral response of each core. In this paper we present methods and results from experiments concerning the post-write tuning of gratings in multicore fibers.

Development of instrumentation for measurements of two components of velocity with a single sensing element

NASA Astrophysics Data System (ADS)

Byers, C. P.; Fu, M. K.; Fan, Y.; Hultmark, M.

2018-02-01

A novel method of obtaining two orthogonal velocity components with high spatial and temporal resolution is investigated. Both components are obtained utilizing a single sensing nanoribbon by combining the two independent operating modes of classic hot wire anemometry and the newly discovered elastic filament velocimetry (EFV). In contrast to hot wire anemometry, EFV measures fluid velocity through correlating the fluid forcing with the internal strain of the wire. In order to utilize both modes of operation, a system that switches between the two operating modes is built and characterized, and the theoretically predicted sensing response time in water is compared to experimental results. The sensing system is capable of switching between the two modes of operation at a frequency of 100 kHz with minimal attenuation with an uncompensated repetition rate up to 3 kHz or up to 10 kHz utilizing modest signal compensation. While further characterization of the sensor performance in air is needed, this methodology enables a technique for obtaining well-resolved yet cost-efficient directional measurements of flow velocities which, for example, can be used for distributed measurements of velocity or measurements of turbulent stresses with excellent spatial resolution.

Constricted double-heterojunction AlGaAs diode lasers - Structures and electrooptical characteristics

NASA Technical Reports Server (NTRS)

Botez, D.

1981-01-01

Constricted double-heterojunction (CDH) diode lasers are presented as a class of nonplanar-substrate devices for which the lasing cavity is on the least resistive electrical path between the contact and the substrate. Various CDH structures are discussed while treating such topics as liquid-phase epitaxy over channeled substrates, lateral mode control, and current control in nonplanar-substrate devices. Ridge-guide CDH lasers with positive-index lateral mode confinement provides single-mode CW operation to 7 mW/facet at room temperature and to 3 mW/facet at 150 C, while exhibiting light-current characteristics with second-harmonic distortions as low as -57 dB below the fundamental level. Semileaky guide CDH lasers with an asymmetric leaky cavity provide single-mode operation to 15-20 mW/facet CW, and to 50 mW/facet at 50% duty cycle.

Selection and amplification of a single optical frequency comb mode for laser cooling of the strontium atoms in an optical clock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Hui; School of Physics, University of Chinese Academy of Sciences, Beijing 100049; Yin, Mojuan

2015-10-12

In this paper, we report on the active filtering and amplification of a single mode from an optical femtosecond laser comb with mode spacing of 250 MHz by optical injection of two external-cavity diode lasers operating in cascade to build a narrow linewidth laser for laser cooling of the strontium atoms in an optical lattice clock. Despite the low injection of individual comb mode of approximately 50 nW, a single comb line at 689 nm could be filtered and amplified to reach as high as 10 mW with 37 dB side mode suppression and a linewidth of 240 Hz. This method could be appliedmore » over a broad spectral band to build narrow linewidth lasers for various applications.« less

High-power actively Q-switched single-mode 1342 nm Nd:YVO₄ ring laser, injection-locked by a cw single-frequency microchip laser.

PubMed

Koch, Peter; Bartschke, Juergen; L'huillier, Johannes A

2015-11-30

In this paper we report on the realization of a single-mode Q-switched Nd:YVO₄ ring laser at 1342 nm. Unidirectional and single-mode operation of the ring laser is achieved by injection-locking with a continuous wave Nd:YVO₄ microchip laser, emitting a single-frequency power of up to 40 mW. The ring laser provides a single-mode power of 13.9 W at 10 kHz pulse repetition frequency with a pulse duration of 18.2 ns and an excellent beam quality (M² < 1.05). By frequency doubling of the fundamental 1342 nm laser, a power of 8.7 W at 671 nm with a pulse duration of 14.8 ns and a beam propagation factor of M² < 1.1 is obtained. The 671 nm radiation features a long-term spectral width of 75 MHz.

Characterization of Geiger mode avalanche photodiodes for fluorescence decay measurements

NASA Astrophysics Data System (ADS)

Jackson, John C.; Phelan, Don; Morrison, Alan P.; Redfern, R. Michael; Mathewson, Alan

2002-05-01

Geiger mode avalanche photodiodes (APD) can be biased above the breakdown voltage to allow detection of single photons. Because of the increase in quantum efficiency, magnetic field immunity, robustness, longer operating lifetime and reduction in costs, solid-state detectors capable of operating at non-cryogenic temperatures and providing single photon detection capabilities provide attractive alternatives to the photomultiplier tube (PMT). Shallow junction Geiger mode APD detectors provide the ability to manufacture photon detectors and detector arrays with CMOS compatible processing steps and allows the use of novel Silicon-on-Insulator(SoI) technology to provide future integrated sensing solutions. Previous work on Geiger mode APD detectors has focused on increasing the active area of the detector to make it more PMT like, easing the integration of discrete reaction, detection and signal processing into laboratory experimental systems. This discrete model for single photon detection works well for laboratory sized test and measurement equipment, however the move towards microfluidics and systems on a chip requires integrated sensing solutions. As we move towards providing integrated functionality of increasingly nanoscopic sized emissions, small area detectors and detector arrays that can be easily integrated into marketable systems, with sensitive small area single photon counting detectors will be needed. This paper will demonstrate the 2-dimensional and 3-dimensional simulation of optical coupling that occurs in Geiger mode APDs. Fabricated Geiger mode APD detectors optimized for fluorescence decay measurements were characterized and preliminary results show excellent results for their integration into fluorescence decay measurement systems.

On wave-CISK and the evaporation-wind feedback for the Madden-Julian oscillation

NASA Technical Reports Server (NTRS)

Kirtman, B.; Vernekar, A.

1993-01-01

The combined effects of Kelvin wave-CISK and the evaporation-wind (E-W) feedback are proposed as a possible mechanism for the Madden-Julian oscillation. A very simple single vertical mode model has been employed to examine the effects of both these processes on moist Kelvin waves. The effects of wave-induced moisture convergence is parameterized by reducing the moist static stability, and CISK occurs when the moist static stability becomes negative. The E-W feedback in the presence of mean easterlies leads to unstable Kelvin modes. The presence of mean westerlies leads to decaying Kelvin modes. When CISK and the E-W feedback work in concert, an unstable Kelvin mode develops that has phase speeds of propagation between 5 m/s and 10 m/s for a large range of parameter values. On the other hand, the E-W feedback mechanism alone, in the case when CISK is not operating, produces the phase speeds of the observed Madden-Julian oscillation for only a very limited range of parameter values.

Switchable dual-wavelength erbium-doped fiber laser based on the photonic crystal fiber loop mirror and chirped fiber Bragg grating

NASA Astrophysics Data System (ADS)

Chen, Wei-Guo; Lou, Shu-Qin; Wang, Li-Wen; Li, Hong-Lei; Guo, Tieying; Jian, Shui-Sheng

2010-03-01

The switchable dual-wavelength erbium-doped fiber laser (EDFL) with a two-mode photonic crystal fiber (PCF) loop mirror and a chirped fiber Bragg grating (CFBG) at room temperature is proposed and experimentally demonstrated. The two-mode PCF loop mirror is formed by inserting a piece of two-mode PCF into a Sagnac loop mirror, with the air-holes of the PCF intentionally collapsing at the splices. By adjusting the state of the polarization controller (PC) appropriately, the laser can be switched between the stable single- and dual-wavelength operations by means of the polarization hole burning (PHB) and spectral hole burning (SHB) effects.

Characterization of Novel Operation Modes for Secondary Emission Ionization Calorimetry

NASA Astrophysics Data System (ADS)

Tiras, Emrah; Dilsiz, Kamuran; Ogul, Hasan; Snyder, Christina; Bilki, Burak; Onel, Yasar; Winn, David

2017-01-01

Secondary Emission (SE) Ionization Calorimetry is a novel technique to measure electromagnetic showers in high radiation environments. We have developed new operation modes by modifying the bias of the conventional PMT circuits. Hamamatsu single anode R7761 and multi-anode R5900-00-M16 Photomultiplier Tubes (PMTs) with modified bases are used as SE detector modules in our SE calorimetry prototype. In this detector module, the first dynode is used as the active media as opposed to photocathode. Here, we report the technical design of new modes and characterization measurements for both SE and PMT modes.

Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

PubMed

Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

2016-07-25

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 10⁶ W/cm² and the maximum pulsed peak power density is 2.16 × 10⁷ W/cm². The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

Single mode tapered fiber-optic interferometer based refractive index sensor and its application to protein sensing.

PubMed

Yadav, T K; Narayanaswamy, R; Abu Bakar, M H; Kamil, Y Mustapha; Mahdi, M A

2014-09-22

We demonstrate refractive index sensors based on single mode tapered fiber and its application as a biosensor. We utilize this tapered fiber optic biosensor, operating at 1550 nm, for the detection of protein (gelatin) concentration in water. The sensor is based on the spectroscopy of mode coupling based on core modes-fiber cladding modes excited by the fundamental core mode of an optical fiber when it transitions into tapered regions from untapered regions. The changes are determined from the wavelength shift of the transmission spectrum. The proposed fiber sensor has sensitivity of refractive index around 1500 nm/RIU and for protein concentration detection, its highest sensitivity is 2.42141 nm/%W/V.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Line width of a single longitudinal mode emitted by an AlGaAs heterojunction laser

NASA Astrophysics Data System (ADS)

Bogatov, Alexandr P.; Eliseev, P. G.; Luk'yanov, S. A.; Pak, G. T.; Petrakova, T. V.

1988-11-01

A nonmonotonic dependence of the emission line width on the power was observed for a single longitudinal mode of an AlGaAs heterojunction laser. This behavior could be due to the dependence of the waveguide coefficient of the amplitude-phase coupling on the nature of operation of the laser.

Diode-end-pumped single-longitudinal-mode passively Q-switched Nd:GGG laser

NASA Astrophysics Data System (ADS)

Xue, Feng; Zhang, Sasa; Cong, Zhenhua; Huang, Qingjie; Guan, Chen; Wu, Qianwen; Chen, Hui; Bai, Fen; Liu, Zhaojun

2018-03-01

Diode-end-pumped passively Q-switched Nd:GGG laser in a ring cavity at 1062 nm was demonstrated. Single-longitudinal-mode laser linewidth less than 0.5 pm was accomplished by unidirectional operation. The maximum output pulse energy was 437 µJ and the pulse width was 43 ns when Cr4+:YAG with an initial transmission of 61% was used.

Comparative study of dual-pulsed 1064 nm Q-switched Nd:YAG laser and single-pulsed 1064 nm Q-switched Nd:YAG laser by using zebrafish model and prospective split-face analysis of facial melasma.

PubMed

Jang, Hee Won; Chun, Seung Hyun; Park, Hae Chul; Ryu, Hwa Jung; Kim, Il-Hwan

2017-04-01

Recently dual-pulsed low-fluence 1064-nm Q-switched Nd:YAG (QSNY) laser has been developed for reducing complication during melasma treatment. Comparison of the efficacy and safety between dual-pulsed mode and single-pulsed mode for the treatment of melasma. In preclinical study, adult zebrafish were irradiated with dual-pulsed and single-pulsed mode. Changes of melanophore and cell death were assessed. In split-face clinical study, dual-pulsed and single-pulsed mode were irradiated on the left and right side of the face, respectively. L* value, clinical digital photos, modified Melasma Area and Severity Index (MASI) scores, and side effects were measured. As compared to single-pulsed mode and dual-pulsed mode with longer intervals, zebrafish melanophore was cleared quickly at dual-pulsed mode with 80-μsec interval and 0.3 J/cm 2 fluence. Dual-pulsed mode showed the least regeneration of melanophore at 4 weeks after irradiation and no cell death was observed with 80-μsec interval. Both pulse modes improved melasma significantly but modified MASI score and L* value were not significantly different between each other. Lesser pain and shorter duration of post-laser erythema were observed with dual-pulsed mode. Dual-pulsed mode was as effective as single-pulsed mode for the treatment of melasma and revealed less side effects.

Optimization for Single-Spike X-Ray FELs at LCLS with a Low Charge Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L.; Ding, Y.; Huang, Z.

2011-12-14

The Linac Coherent Light Source is an x-ray free-electron laser at the SLAC National Accelerator Laboratory, which is operating at x-ray wavelengths of 20-1.2 Angstrom with peak brightness nearly ten orders of magnitude beyond conventional synchrotron radiation sources. At the low charge operation mode (20 pC), the x-ray pulse length can be <10 fs. In this paper we report our numerical optimization and simulations to produce even shorter x-ray pulses by optimizing the machine and undulator setup at 20 pC charge. In the soft x-ray regime, with combination of slotted-foil or undulator taper, a single spike x-ray pulse is achievablemore » with peak FEL power of a few 10s GW. Linac Coherent Light Source (LCLS), the world's first hard x-ray Free electron laser (FEL), has started operation since 2009. With nominal operation charge of 250 pC, the generated x-ray pulse length is from 70 fs to a few hundred fs. This marks the beginning of a new era of ultrashort x-ray sciences. In addition, a low charge (20pC) operation mode has also been established. Since the collective effects are reduced at the low charge mode, we can increase the compression factor and still achieve a few kA peak current. The expected electron beam and x-ray pulses are less than 10 fs. There are growing interests in even shorter x-ray pulses, such as fs to sub-fs regime. One of the simple solutions is going to even lower charge. As discussed, single-spike x-ray pulses can be generated using 1 pC charge. However, this charge level is out of the present LCLS diagnostic range. 20 pC is a reasonable operation charge at LCLS, based on the present diagnostic system. At 20 pC in the soft x-ray wavelength regime, we have experimentally demonstrated that FEL can work at undercompression or over-compression mode, such as 1 degree off the full-compression; at full-compression, however, there is almost no lasing. In hard x-ray wavelength regime, we observed that there are reasonable photons generated even at full-compression mode, although the photon number is less than that from under-compression or over-compression mode. Since we cannot measure the x-ray pulse length at this time scale, the machine is typically optimized for generating maximum photons, not minimum pulse length. In this paper, we study the methods of producing femtosecond (or single-spike) x-ray pulses at LCLS with 20 pC charge, based on start-to-end simulations. Figure 1 shows a layout of LCLS. The compression in the second bunch compressor (BC2) determines the final e-beam bunch length. However, the laser heater, dog-leg after the main linac (DL2) and collective effects also affect the final bunch length. To adjust BC2 compression, we can either change the L2 phase or BC2 R{sub 56}. In this paper we only tune L2 phase while keep BC2 R{sub 56} fixed. For the start-to-end simulations, we used IMPACT-T and ELEGANT tracking from the photocathode to the entrance of the undulator, after that the FEL radiation was simulated with GENESIS. IMPACT-T tracks about 10{sup 6} particles in the injector part until 135 MeV, including 3D space charge force. The output particles from IMPACT-T are smoothed and increased to 12 x 10{sup 6} to reduce high-frequency numerical noise for subsequent ELEGANT simulations, which include linear and nonlinear transport effects, a 1D transient model of CSR, and longitudinal space charge effects, as well as geometric and resistive wake fields in the accelerator. In GENESIS part, the longitudinal wake field from undulator chamber and longitudinal space field are also included.« less

Electrically actuatable temporal tristimulus-color device

DOEpatents

Koehler, Dale R.

1992-01-01

The electrically actuated light filter operates in a cyclical temporal mode to effect a tristimulus-color light analyzer. Construction is based on a Fabry-Perot interferometer comprised of a high-speed movable mirror pair and cyclically powered electrical actuators. When combined with a single vidicon tube or a monochrome solid state image sensor, a temporally operated tristimulus-color video camera is effected. A color-generated is accomplished when constructed with a companion light source and is a flicker-free colored-light source for transmission type display systems. Advantages of low cost and small physical size result from photolithographic batch-processing manufacturability.

Laser performance and modeling of RE3+:YAG double-clad crystalline fiber waveguides

NASA Astrophysics Data System (ADS)

Li, Da; Lee, Huai-Chuan; Meissner, Stephanie K.; Meissner, Helmuth E.

2018-02-01

We report on laser performance of ceramic Yb:YAG and single crystal Tm:YAG double-clad crystalline fiber waveguide (CFW) lasers towards the goal of demonstrating the design and manufacturing strategy of scaling to high output power. The laser component is a double-clad CFW, with RE3+:YAG (RE = Yb, Tm respectively) core, un-doped YAG inner cladding, and ceramic spinel or sapphire outer cladding. Laser performance of the CFW has been demonstrated with 53.6% slope efficiency and 27.5-W stable output power at 1030-nm for Yb:YAG CFW, and 31.6% slope efficiency and 46.7-W stable output power at 2019-nm for Tm:YAG CFW, respectively. Adhesive-Free Bond (AFB®) technology enables a designable refractive index difference between core and inner cladding, and designable core and inner cladding sizes, which are essential for single transverse mode CFW propagation. To guide further development of CFW designs, we present thermal modeling, power scaling and design of single transverse mode operation of double-clad CFWs and redefine the single-mode operation criterion for the double-clad structure design. The power scaling modeling of double-clad CFW shows that in order to achieve the maximum possible output power limited by the physical properties, including diode brightness, thermal lens effect, and simulated Brillion scattering, the length of waveguide is in the range of 0.5 2 meters. The length of an individual CFW is limited by single crystal growth and doping uniformity to about 100 to 200 mm lengths, and also by availability of starting crystals and manufacturing complexity. To overcome the limitation of CFW lengths, end-to-end proximity-coupling of CFWs is introduced.

Narrow linewidth power scaling and phase stabilization of 2-μm thulium fiber lasers

NASA Astrophysics Data System (ADS)

Goodno, Gregory D.; Book, Lewis D.; Rothenberg, Joshua E.; Weber, Mark E.; Benjamin Weiss, S.

2011-11-01

Thulium-doped fiber lasers (TFLs) emitting retina-safe 2-μm wavelengths offer substantial power-scaling advantages over ytterbium-doped fiber lasers for narrow linewidth, single-mode operation. This article reviews the design and performance of a pump-limited, 600 W, single-mode, single-frequency TFL amplifier chain that balances thermal limitations against those arising from stimulated Brillouin scattering (SBS). A simple analysis of thermal and SBS limits is anchored with measurements on kilowatt class Tm and Yb fiber lasers to highlight the scaling advantage of Tm for narrow linewidth operation. We also report recent results on active phase-locking of a TFL amplifier to an optical reference as a precursor to further parallel scaling via coherent beam combining.

Recent Enhancements to the National Transonic Facility (Mixed Mode Operations)

NASA Technical Reports Server (NTRS)

Kilgore, W. Allen; Chan, David; Balakrishna, S.; Wahls, Richard A.

2006-01-01

The U.S. National Transonic Facility continues to make enhancements to provide quality data in a safe, efficient and cost effective method for aerodynamic ground testing. Recent enhancements discussed in this paper include the development of a Mixed-mode of operations that combine Air-mode operations with Nitrogen-mode operations. This implementation and operational results of this new Mixed-mode expands the ambient temperature transonic region of testing beyond the Air-mode limitations at a significantly reduced cost over Nitrogen Mode operation.

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser based on one polarization-maintaining fiber Bragg grating incorporating saturable absorber and feedback fiber loop

NASA Astrophysics Data System (ADS)

Feng, Suchun; Xu, Ou; Lu, Shaohua; Ning, Tigang; Jian, Shuisheng

2009-06-01

Switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser based on one polarization-maintaining fiber Bragg grating (PMFBG) is demonstrated. Due to the enhancement of the polarization hole burning (PHB) by the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The stable SLM operation is guaranteed by a compound-ring cavity and a saturable absorber (SA). The optical signal-to-noise ratio (OSNR) is over 45 dB. The amplitude variation in nearly one and half an hour is less than 0.2 dB.

Nonlinear digital out-of-plane waveguide coupler based on nonlinear scattering of a single graphene layer

NASA Astrophysics Data System (ADS)

Asadi, Reza; Ouyang, Zhengbiao

2018-03-01

A new mechanism for out-of-plane coupling into a waveguide is presented and numerically studied based on nonlinear scattering of a single nano-scale Graphene layer inside the waveguide. In this mechanism, the refractive index nonlinearity of Graphene and nonhomogeneous light intensity distribution occurred due to the interference between the out-of-plane incident pump light and the waveguide mode provide a virtual grating inside the waveguide, coupling the out-of-plane pump light into the waveguide. It has been shown that the coupling efficiency has two distinct values with high contrast around a threshold pump intensity, providing suitable condition for digital optical applications. The structure operates at a resonance mode due to band edge effect, which enhances the nonlinearity and decreases the required threshold intensity.

Feasibility of efficient room-temperature solid-state sources of indistinguishable single photons using ultrasmall mode volume cavities

NASA Astrophysics Data System (ADS)

Wein, Stephen; Lauk, Nikolai; Ghobadi, Roohollah; Simon, Christoph

2018-05-01

Highly efficient sources of indistinguishable single photons that can operate at room temperature would be very beneficial for many applications in quantum technology. We show that the implementation of such sources is a realistic goal using solid-state emitters and ultrasmall mode volume cavities. We derive and analyze an expression for photon indistinguishability that accounts for relevant detrimental effects, such as plasmon-induced quenching and pure dephasing. We then provide the general cavity and emitter conditions required to achieve efficient indistinguishable photon emission and also discuss constraints due to phonon sideband emission. Using these conditions, we propose that a nanodiamond negatively charged silicon-vacancy center combined with a plasmonic-Fabry-Pérot hybrid cavity is an excellent candidate system.

Passively mode-locked Raman fiber laser with 100 GHz repetition rate

NASA Astrophysics Data System (ADS)

Schröder, Jochen; Coen, Stéphane; Vanholsbeeck, Frédérique; Sylvestre, Thibaut

2006-12-01

We experimentally demonstrate the operation of a passively mode-locked Raman fiber ring laser with an ultrahigh repetition rate of 100GHz and up to 430mW of average output power. This laser constitutes a simple wavelength versatile pulsed optical source. Stable mode locking is based on dissipative four-wave mixing with a single fiber Bragg grating acting as the mode-locking element.

Master/slave clock arrangement for providing reliable clock signal

NASA Technical Reports Server (NTRS)

Abbey, Duane L. (Inventor)

1977-01-01

The outputs of two like frequency oscillators are combined to form a single reliable clock signal, with one oscillator functioning as a slave under the control of the other to achieve phase coincidence when the master is operative and in a free-running mode when the master is inoperative so that failure of either oscillator produces no effect on the clock signal.

Undulator performance on PEP storage ring with different optics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shenoy, G.K.; Viccaro, P.J.; Alp, E.E.

1987-12-01

Our ability to profitably utilize the radiation from undulators proposed for PEP is determined by their performance in the different operating modes and by whether the design tolerance required for acceptable operation of the device can be met with available technology. The purpose of this paper is to provide spectral characteristics for some typical devices calculated using a Monte-Carlo algorithm in which the Lienard-Wiechert potential is integrated over the trajectory of the charged particle along the undulator length. The actual emittance of the particle beam for the various PEP operating modes are included explicitly in the simulations. In addition, wemore » have carried out a single partial analysis of the effects of undulator magnetic field errors on the spectral properties in order to estimate the design tolerance requirements necessary for devices which have been proposed PEP. 6 figs.« less

Terraced-heterostructure large-optical-cavity AlGaAs diode laser - A new type of high-power CW single-mode device

NASA Technical Reports Server (NTRS)

Botez, D.; Connolly, J. C.

1982-01-01

A new terraced lateral wave confining structure is obtained by liquid phase epitaxy over channeled substrates misoriented perpendicular to the channels' direction. Single spatial and longitudinal mode CW operation is achieved to 50 mW from one facet, in large spot sizes (2 x 7.5 micron, 1/e squared points in intensity) and narrow beams (6 deg x 23 deg), full width half-power). At 70 C ambient temperature CW lasing is obtained to 15 mW from one facet. Weak mode confinement in an asymmetric lateral waveguides provides discrimination against high-order mode oscillation.

Design, fabrication and performance of a mixed-reactant membraneless micro direct methanol fuel cell stack

NASA Astrophysics Data System (ADS)

Abrego-Martínez, J. C.; Moreno-Zuria, A.; Cuevas-Muñiz, F. M.; Arriaga, L. G.; Sun, Shuhui; Mohamedi, Mohamed

2017-12-01

In the present work, we report the design, fabrication and evaluation of a membraneless mixed-reactant and air-breathing microfluidic direct methanol fuel cell (ML-μDMFC) stack operated in passive mode. The operation under mixed-reactant conditions was achieved by using a highly methanol-tolerant Ag/Pt/CP cathode with ultra-low Pt loading in alkaline medium. Prior to the fabrication of the stack, a flow simulation was made in order to study the behavior of the reactants stream in the microchannel through the 2 cells. Subsequently, the device was tested in passive mode using a mixture of 5 M MeOH +0.5 M KOH. The results showed that by connecting the 2 cells in series, it is possible to effectively double the voltage of a single ML-μDMFC, as well as increasing the absolute power by 75% with practically no cost increase. The stack was capable of operate continuously for more than 2 h with a single charge of 40 μL, producing an OCV of 0.89 V and a maximum power density of 3.33 mW mgPt-1. Additionally, the device exhibited good stability throughout a 10 h test.

Tunable and switchable dual-wavelength dissipative soliton generation in an all-normal-dispersion Yb-doped fiber laser with birefringence fiber filter.

PubMed

Zhang, Z X; Xu, Z W; Zhang, L

2012-11-19

We report the generation of tunable single- and dual-wavelength dissipative solitons in an all-normal-dispersion mode-locked Yb-doped fiber laser, to the best of our knowledge, for the first time. Besides single-wavelength mode-locking, dual-wavelength mode-locking was achieved using an in-line birefringence fiber filter with periodic multiple passbands, which not only allows multiple wavelengths to oscillate simultaneously but also performs spectrum modulation on highly chirped dissipative pulse. Furthermore, taking advantage of the tunability of the birefringence fiber filter, wavelength tuning for both single- and dual-wavelength dissipative soliton mode-locking was realized. The dual-wavelength operation is also switchable. The all-fiber dissipative laser with flexible outputs can meet diverse application needs.

1.5 W high efficiency and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect.

PubMed

Wu, Jing; Ju, Youlun; Dai, Tongyu; Yao, Baoquan; Wang, Yuezhu

2017-10-30

We demonstrated an efficient and tunable single-longitudinal-mode Ho:YLF ring laser based on Faraday effect for application to measure atmospheric carbon dioxide (CO 2 ). Single-longitudinal-mode power at 2051.65 nm achieved 528 mW with the slope efficiency of 39.5% and the M 2 factor of 1.07, and the tunable range of about 178 GHz was obtained by inserting a Fabry-Perot (F-P) etalon with the thickness of 0.5 mm. In addition, the maximum single-longitudinal-mode power reached 1.5 W with the injected power of 528 mW at 2051.65 nm by master oscillator power amplifier (MOPA) technique. High efficiency and tunable single-longitudinal-mode based on Faraday effect around 2 μm has not been reported yet to the best of our knowledge.

A Pixel Readout Chip in 40 nm CMOS Process for High Count Rate Imaging Systems with Minimization of Charge Sharing Effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maj, Piotr; Grybos, P.; Szczgiel, R.

2013-11-07

We present a prototype chip in 40 nm CMOS technology for readout of hybrid pixel detector. The prototype chip has a matrix of 18x24 pixels with a pixel pitch of 100 μm. It can operate both in single photon counting (SPC) mode and in C8P1 mode. In SPC the measured ENC is 84 e ₋rms (for the peaking time of 48 ns), while the effective offset spread is below 2 mV rms. In the C8P1 mode the chip reconstructs full charge deposited in the detector, even in the case of charge sharing, and it identifies a pixel with the largestmore » charge deposition. The chip architecture and preliminary measurements are reported.« less

Two-wavelength, passive self-injection-controlled operation of diode-pumped cw Yb-doped crystal lasers.

PubMed

Louyer, Yann; Wallerand, Jean-Pierre; Himbert, Marc; Deneva, Margarita; Nenchev, Marin

2003-09-20

We demonstrate and investigate a peculiar mode of cw Yb3+-doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place in either a single beam or spatially separated beams. The laser employs original two-channel cavities that use a passive self-injection-locking (PSIL) control to reduce intracavity loss. The advantages of the application of the PSIL technique and some limitations are shown. The conditions for two-wavelength multimode operation of the cw quasi-three-level diode-pumped Yb3+ lasers and the peculiarity of such an operation are carried out both theoretically and experimentally. The results reported are based on the example of a Yb3+:GGG laser but similar results are also obtained with a Yb3+:YAG laser. The laser operates in the 1023-1033-nm (1030-1040-nm) range with a total output power of 0.4 W. A two-wavelength, single longitudinal mode generation is also obtained.

Effect of chiral symmetry on chaotic scattering from Majorana zero modes.

PubMed

Schomerus, H; Marciani, M; Beenakker, C W J

2015-04-24

In many of the experimental systems that may host Majorana zero modes, a so-called chiral symmetry exists that protects overlapping zero modes from splitting up. This symmetry is operative in a superconducting nanowire that is narrower than the spin-orbit scattering length, and at the Dirac point of a superconductor-topological insulator heterostructure. Here we show that chiral symmetry strongly modifies the dynamical and spectral properties of a chaotic scatterer, even if it binds only a single zero mode. These properties are quantified by the Wigner-Smith time-delay matrix Q=-iℏS^{†}dS/dE, the Hermitian energy derivative of the scattering matrix, related to the density of states by ρ=(2πℏ)^{-1}TrQ. We compute the probability distribution of Q and ρ, dependent on the number ν of Majorana zero modes, in the chiral ensembles of random-matrix theory. Chiral symmetry is essential for a significant ν dependence.

Unitarily localizable entanglement of Gaussian states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serafini, Alessio; Adesso, Gerardo; Illuminati, Fabrizio

2005-03-01

We consider generic (mxn)-mode bipartitions of continuous-variable systems, and study the associated bisymmetric multimode Gaussian states. They are defined as (m+n)-mode Gaussian states invariant under local mode permutations on the m-mode and n-mode subsystems. We prove that such states are equivalent, under local unitary transformations, to the tensor product of a two-mode state and of m+n-2 uncorrelated single-mode states. The entanglement between the m-mode and the n-mode blocks can then be completely concentrated on a single pair of modes by means of local unitary operations alone. This result allows us to prove that the PPT (positivity of the partial transpose)more » condition is necessary and sufficient for the separability of (m+n)-mode bisymmetric Gaussian states. We determine exactly their negativity and identify a subset of bisymmetric states whose multimode entanglement of formation can be computed analytically. We consider explicit examples of pure and mixed bisymmetric states and study their entanglement scaling with the number of modes.« less

Triple-mode single-transistor graphene amplifier and its applications.

PubMed

Yang, Xuebei; Liu, Guanxiong; Balandin, Alexander A; Mohanram, Kartik

2010-10-26

We propose and experimentally demonstrate a triple-mode single-transistor graphene amplifier utilizing a three-terminal back-gated single-layer graphene transistor. The ambipolar nature of electronic transport in graphene transistors leads to increased amplifier functionality as compared to amplifiers built with unipolar semiconductor devices. The ambipolar graphene transistors can be configured as n-type, p-type, or hybrid-type by changing the gate bias. As a result, the single-transistor graphene amplifier can operate in the common-source, common-drain, or frequency multiplication mode, respectively. This in-field controllability of the single-transistor graphene amplifier can be used to realize the modulation necessary for phase shift keying and frequency shift keying, which are widely used in wireless applications. It also offers new opportunities for designing analog circuits with simpler structure and higher integration densities for communications applications.

Control of a lithium-ion battery storage system for microgrid applications

NASA Astrophysics Data System (ADS)

Pegueroles-Queralt, Jordi; Bianchi, Fernando D.; Gomis-Bellmunt, Oriol

2014-12-01

The operation of future microgrids will require the use of energy storage systems employing power electronics converters with advanced power management capacities. This paper presents the control scheme for a medium power lithium-ion battery bidirectional DC/AC power converter intended for microgrid applications. The switching devices of a bidirectional DC converter are commanded by a single sliding mode control law, dynamically shaped by a linear voltage regulator in accordance with the battery management system. The sliding mode controller facilitates the implementation and design of the control law and simplifies the stability analysis over the entire operating range. Control parameters of the linear regulator are designed to minimize the impact of commutation noise in the DC-link voltage regulation. The effectiveness of the proposed control strategy is illustrated by experimental results.

1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miah, M. J., E-mail: jarez.miah@tu-berlin.de; Posilovic, K.; Kalosha, V. P.

2014-10-13

High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M{sup 2} is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm{sup −2}sr{supmore » −1} is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.« less

Single photon detection in a waveguide-coupled Ge-on-Si lateral avalanche photodiode.

PubMed

Martinez, Nicholas J D; Gehl, Michael; Derose, Christopher T; Starbuck, Andrew L; Pomerene, Andrew T; Lentine, Anthony L; Trotter, Douglas C; Davids, Paul S

2017-07-10

We examine gated-Geiger mode operation of an integrated waveguide-coupled Ge-on-Si lateral avalanche photodiode (APD) and demonstrate single photon detection at low dark count for this mode of operation. Our integrated waveguide-coupled APD is fabricated using a selective epitaxial Ge-on-Si growth process resulting in a separate absorption and charge multiplication (SACM) design compatible with our silicon photonics platform. Single photon detection efficiency and dark count rate is measured as a function of temperature in order to understand and optimize performance characteristics in this device. We report single photon detection of 5.27% at 1310 nm and a dark count rate of 534 kHz at 80 K for a Ge-on-Si single photon avalanche diode. Dark count rate is the lowest for a Ge-on-Si single photon detector in this range of temperatures while maintaining competitive detection efficiency. A jitter of 105 ps was measured for this device.

Tunneling Mode of Scanning Electrochemical Microscopy: Probing Electrochemical Processes at Single Nanoparticles.

PubMed

Sun, Tong; Wang, Dengchao; Mirkin, Michael V

2018-06-18

Electrochemical experiments at individual nanoparticles (NPs) can provide new insights into their structure-activity relationships. By using small nanoelectrodes as tips in a scanning electrochemical microscope (SECM), we recently imaged individual surface-bound 10-50 nm metal NPs. Herein, we introduce a new mode of SECM operation based on tunneling between the tip and a nanoparticle immobilized on the insulating surface. The obtained current vs. distance curves show the transition from the conventional feedback response to electron tunneling between the tip and the NP at separation distances of less than about 3 nm. In addition to high-resolution imaging of the NP topography, the tunneling mode enables measurement of the heterogeneous kinetics at a single NP without making an ohmic contact with it. The developed method should be useful for studying the effects of nanoparticle size and geometry on electrocatalytic activity in real-world applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

11-GHz waveguide Nd:YAG laser CW mode-locked with single-layer graphene.

PubMed

Okhrimchuk, Andrey G; Obraztsov, Petr A

2015-06-08

We report stable, passive, continuous-wave (CW) mode-locking of a compact diode-pumped waveguide Nd:YAG laser with a single-layer graphene saturable absorber. The depressed cladding waveguide in the Nd:YAG crystal is fabricated with an ultrafast laser inscription method. The saturable absorber is formed by direct deposition of CVD single-layer graphene on the output coupler. The few millimeter-long cavity provides generation of 16-ps pulses with repetition rates in the GHz range (up to 11.3 GHz) and 12 mW average power. Stable CW mode-locking operation is achieved by controlling the group delay dispersion in the laser cavity with a Gires-Tournois interferometer.

11-GHz waveguide Nd:YAG laser CW mode-locked with single-layer graphene

PubMed Central

Okhrimchuk, Andrey G.; Obraztsov, Petr A.

2015-01-01

We report stable, passive, continuous-wave (CW) mode-locking of a compact diode-pumped waveguide Nd:YAG laser with a single-layer graphene saturable absorber. The depressed cladding waveguide in the Nd:YAG crystal is fabricated with an ultrafast laser inscription method. The saturable absorber is formed by direct deposition of CVD single-layer graphene on the output coupler. The few millimeter-long cavity provides generation of 16-ps pulses with repetition rates in the GHz range (up to 11.3 GHz) and 12 mW average power. Stable CW mode-locking operation is achieved by controlling the group delay dispersion in the laser cavity with a Gires–Tournois interferometer. PMID:26052678

Design for high-power, single-lobe, grating-surface-emitting quantum cascade lasers enabled by plasmon-enhanced absorption of antisymmetric modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sigler, C.; Kirch, J. D.; Mawst, L. J.

2014-03-31

Resonant coupling of the transverse-magnetic polarized (guided) optical mode of a quantum-cascade laser (QCL) to the antisymmetric surface-plasmon modes of 2nd-order distributed-feedback (DFB) metal/semiconductor gratings results in strong antisymmetric-mode absorption. In turn, lasing in the symmetric mode, that is, surface emission in a single-lobe far-field beam pattern, is strongly favored over controllable ranges in grating duty cycle and tooth height. By using core-region characteristics of a published 4.6 μm-emitting QCL, grating-coupled surface-emitting (SE) QCLs are analyzed and optimized for highly efficient single-lobe operation. For infinite-length devices, it is found that when the antisymmetric mode is resonantly absorbed, the symmetric mode hasmore » negligible absorption loss (∼0.1 cm{sup −1}) while still being efficiently outcoupled, through the substrate, by the DFB grating. For finite-length devices, 2nd-order distributed Bragg reflector (DBR) gratings are used on both sides of the DFB grating to prevent uncontrolled reflections from cleaved facets. Equations for the threshold-current density and the differential quantum efficiency of SE DFB/DBR QCLs are derived. For 7 mm-long, 8.0 μm-wide, 4.6 μm-emitting devices, with an Ag/InP grating of ∼39% duty cycle, and ∼0.22 μm tooth height, threshold currents as low as 0.45 A are projected. Based on experimentally obtained internal efficiency values from high-performance QCLs, slope efficiencies as high as 3.4 W/A are projected; thus, offering a solution for watt-range, single-lobe CW operation from SE, mid-infrared QCLs.« less

Biosensing operations based on whispering-gallery-mode optical cavities in single 1.0-µm diameter hexagonal GaN microdisks grown by radio-frequency plasma-assisted molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Kouno, Tetsuya; Sakai, Masaru; Kishino, Katsumi; Hara, Kazuhiko

2016-05-01

Biosensing operations based on a whispering-gallery-mode optical cavity in a single hexagonal GaN microdisk of approximately 1.0 µm diameter were demonstrated here. The sharp resonant peak in the photoluminescence spectrum obtained from the microdisk in aqueous sucrose solution redshifts with a change in sucrose concentration. The results indicate that an extremely small microdisk could be used as an optical transducer for sensing sugar, namely, as a biosensor. Furthermore, we investigate the relationship between the diameter of the microdisk and the sensitivity of the biosensor.

Dual-mode switching of a liquid crystal panel for viewing angle control

NASA Astrophysics Data System (ADS)

Baek, Jong-In; Kwon, Yong-Hoan; Kim, Jae Chang; Yoon, Tae-Hoon

2007-03-01

The authors propose a method to control the viewing angle of a liquid crystal (LC) panel using dual-mode switching. To realize both wide viewing angle (WVA) characteristics and narrow viewing angle (NVA) characteristics with a single LC panel, the authors use two different dark states. The LC layer can be aligned homogeneously parallel to the transmission axis of the bottom polarizer for WVA dark state operation, while it can be aligned vertically for NVA dark state operation. The authors demonstrated that viewing angle control can be achieved with a single panel without any loss of contrast at the front.

Projective filtering of the fundamental eigenmode from spatially multimode radiation

NASA Astrophysics Data System (ADS)

Pérez, A. M.; Sharapova, P. R.; Straupe, S. S.; Miatto, F. M.; Tikhonova, O. V.; Leuchs, G.; Chekhova, M. V.

2015-11-01

Lossless filtering of a single coherent (Schmidt) mode from spatially multimode radiation is a problem crucial for optics in general and for quantum optics in particular. It becomes especially important in the case of nonclassical light that is fragile to optical losses. An example is bright squeezed vacuum generated via high-gain parametric down conversion or four-wave mixing. Its highly multiphoton and multimode structure offers a huge increase in the information capacity provided that each mode can be addressed separately. However, the nonclassical signature of bright squeezed vacuum, photon-number correlations, are highly susceptible to losses. Here we demonstrate lossless filtering of a single spatial Schmidt mode by projecting the spatial spectrum of bright squeezed vacuum on the eigenmode of a single-mode fiber. Moreover, we show that the first Schmidt mode can be captured by simply maximizing the fiber-coupled intensity. Importantly, the projection operation does not affect the targeted mode and leaves it usable for further applications.

Two-dimensional photonic crystal bandedge laser with hybrid perovskite thin film for optical gain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cha, Hyungrae; Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826; Bae, Seunghwan

2016-05-02

We report optically pumped room temperature single mode laser that contains a thin film of hybrid perovskite, an emerging photonic material, as gain medium. Two-dimensional square lattice photonic crystal (PhC) backbone structure enables single mode laser operation via a photonic bandedge mode, while a thin film of methyl-ammonium lead iodide (CH{sub 3}NH{sub 3}PbI{sub 3}) spin-coated atop provides optical gain for lasing. Two kinds of bandedge modes, Γ and M, are employed, and both devices laser in single mode at similar laser thresholds of ∼200 μJ/cm{sup 2} in pulse energy density. Polarization dependence measurements reveal a clear difference between the two kindsmore » of bandedge lasers: isotropic for the Γ-point laser and highly anisotropic for the M-point laser. These observations are consistent with expected modal properties, confirming that the lasing actions indeed originate from the corresponding PhC bandedge modes.« less

New VCSEL technology with scalability for single mode operation and densely integrated arrays

NASA Astrophysics Data System (ADS)

Zhao, Guowei; Demir, Abdullah; Freisem, Sabine; Zhang, Yu; Liu, Xiaohang; Deppe, Dennis G.

2011-06-01

Data are presented demonstrating a new lithographic vertical-cavity surface-emitting laser (VCSEL) technology, which produces simultaneous mode- and current-confinement only by lithography and epitaxial crystal growth. The devices are grown by solid source molecular beam epitaxy, and have lithographically defined sizes that vary from 3 μm to 20 μm. The lithographic process allows the devices to have high uniformity throughout the wafer and scalability to very small size. The 3 μm device shows a threshold current of 310 μA, the slope efficiency of 0.81 W/A, and the maximum output power of more than 5 mW. The 3 μm device also shows single-mode single-polarization operation without the use of surface grating, and has over 25 dB side-mode-suppression-ratio up to 1 mW of output power. The devices have low thermal resistance due to the elimination of oxide aperture. High reliability is achieved by removal of internal strain caused by the oxide, stress test shows no degradation for the 3 μm device operating at very high injection current level of 142 kA/cm2 for 1000 hours, while at this dive level commercial VCSELs fail rapidly. The lithographic VCSEL technology can lead to manufacture of reliable small size laser diode, which will have application in large area 2-D arrays and low power sensors.

Short-term ensemble streamflow forecasting using operationally-produced single-valued streamflow forecasts - A Hydrologic Model Output Statistics (HMOS) approach

NASA Astrophysics Data System (ADS)

Regonda, Satish Kumar; Seo, Dong-Jun; Lawrence, Bill; Brown, James D.; Demargne, Julie

2013-08-01

We present a statistical procedure for generating short-term ensemble streamflow forecasts from single-valued, or deterministic, streamflow forecasts produced operationally by the U.S. National Weather Service (NWS) River Forecast Centers (RFCs). The resulting ensemble streamflow forecast provides an estimate of the predictive uncertainty associated with the single-valued forecast to support risk-based decision making by the forecasters and by the users of the forecast products, such as emergency managers. Forced by single-valued quantitative precipitation and temperature forecasts (QPF, QTF), the single-valued streamflow forecasts are produced at a 6-h time step nominally out to 5 days into the future. The single-valued streamflow forecasts reflect various run-time modifications, or "manual data assimilation", applied by the human forecasters in an attempt to reduce error from various sources in the end-to-end forecast process. The proposed procedure generates ensemble traces of streamflow from a parsimonious approximation of the conditional multivariate probability distribution of future streamflow given the single-valued streamflow forecast, QPF, and the most recent streamflow observation. For parameter estimation and evaluation, we used a multiyear archive of the single-valued river stage forecast produced operationally by the NWS Arkansas-Red River Basin River Forecast Center (ABRFC) in Tulsa, Oklahoma. As a by-product of parameter estimation, the procedure provides a categorical assessment of the effective lead time of the operational hydrologic forecasts for different QPF and forecast flow conditions. To evaluate the procedure, we carried out hindcasting experiments in dependent and cross-validation modes. The results indicate that the short-term streamflow ensemble hindcasts generated from the procedure are generally reliable within the effective lead time of the single-valued forecasts and well capture the skill of the single-valued forecasts. For smaller basins, however, the effective lead time is significantly reduced by short basin memory and reduced skill in the single-valued QPF.

Strong Light-Matter Interactions in Single Open Plasmonic Nanocavities at the Quantum Optics Limit.

PubMed

Liu, Renming; Zhou, Zhang-Kai; Yu, Yi-Cong; Zhang, Tengwei; Wang, Hao; Liu, Guanghui; Wei, Yuming; Chen, Huanjun; Wang, Xue-Hua

2017-06-09

Reaching the quantum optics limit of strong light-matter interactions between a single exciton and a plasmon mode is highly desirable, because it opens up possibilities to explore room-temperature quantum devices operating at the single-photon level. However, two challenges severely hinder the realization of this limit: the integration of single-exciton emitters with plasmonic nanostructures and making the coupling strength at the single-exciton level overcome the large damping of the plasmon mode. Here, we demonstrate that these two hindrances can be overcome by attaching individual J aggregates to single cuboid Au@Ag nanorods. In such hybrid nanosystems, both the ultrasmall mode volume of ∼71  nm^{3} and the ultrashort interaction distance of less than 0.9 nm make the coupling coefficient between a single J-aggregate exciton and the cuboid nanorod as high as ∼41.6  meV, enabling strong light-matter interactions to be achieved at the quantum optics limit in single open plasmonic nanocavities.

Qualitative analysis of ultra-short optical dissipative solitary pulses in the actively mode-locked semiconductor heterolasers with an external fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Campos Acosta, Joaquin; Moreno Zarate, Pedro; Pons Aglio, Alicia

2011-02-01

An advanced qualitative characterization of simultaneously existing various low-power trains of ultra-short optical pulses with an internal frequency modulation in a distributed laser system based on semiconductor heterostructure is presented. The scheme represents a hybrid cavity consisting of a single-mode heterolaser operating in the active mode-locking regime and an external long single-mode optical fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and linear optical losses. In fact, we consider the trains of optical dissipative solitons, which appear within double balance between the second-order dispersion and cubic-law nonlinearity as well as between the active-medium gain and linear optical losses in a hybrid cavity. Moreover, we operate on specially designed modulating signals providing non-conventional composite regimes of simultaneous multi-pulse active mode-locking. As a result, the mode-locking process allows shaping regular trains of picosecond optical pulses excited by multi-pulse independent on each other sequences of periodic modulations. In so doing, we consider the arranged hybrid cavity as a combination of a quasi-linear part responsible for the active mode-locking by itself and a nonlinear part determining the regime of dissipative soliton propagation. Initially, these parts are analyzed individually, and then the primarily obtained data are coordinated with each other. Within this approach, a contribution of the appeared cubically nonlinear Ginzburg-Landau operator is analyzed via exploiting an approximate variational procedure involving the technique of trial functions.

Tunable microwave generation of a monolithic dual-wavelength distributed feedback laser.

PubMed

Lo, Yen-Hua; Wu, Yu-Chang; Hsu, Shun-Chieh; Hwang, Yi-Chia; Chen, Bai-Ci; Lin, Chien-Chung

2014-06-02

The dynamic behavior of a monolithic dual-wavelength distributed feedback laser was fully investigated and mapped. The combination of different driving currents for master and slave lasers can generate a wide range of different operational modes, from single mode, period 1 to chaos. Both the optical and microwave spectrum were recorded and analyzed. The detected single mode signal can continuously cover from 15GHz to 50GHz, limited by photodetector bandwidth. The measured optical four-wave-mixing pattern indicates that a 70GHz signal can be generated by this device. By applying rate equation analysis, the important laser parameters can be extracted from the spectrum. The extracted relaxation resonant frequency is found to be 8.96GHz. With the full operational map at hand, the suitable current combination can be applied to the device for proper applications.

Three-party Quantum Secure Direct Communication with Single Photons in both Polarization and Spatial-mode Degrees of Freedom

NASA Astrophysics Data System (ADS)

Wang, LiLi; Ma, WenPing; Wang, MeiLing; Shen, DongSu

2016-05-01

We present an efficient three-party quantum secure direct communication (QSDC) protocol with single photos in both polarization and spatial-mode degrees of freedom. The three legal parties' messages can be encoded on the polarization and the spatial-mode states of single photons independently with desired unitary operations. A party can obtain the other two parties' messages simultaneously through a quantum channel. Because no extra public information is transmitted in the classical channels, the drawback of information leakage or classical correlation does not exist in the proposed scheme. Moreover, the comprehensive security analysis shows that the presented QSDC network protocol can defend the outsider eavesdropper's several sorts of attacks. Compared with the single photons with only one degree of freedom, our protocol based on the single photons in two degrees of freedom has higher capacity. Since the preparation and the measurement of single photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques, the proposed protocol is practical.

Pulsed Submillimeter Laser Program.

DTIC Science & Technology

1979-05-15

number of interrelated subsystems required for a heterodyning FIR radar were investigated. The work focused on optically pumped FIR lasers which... laser pressure. Figure 9 illustrates the effect on optical shape of raising laser pressure. It can be seen that considerable pulse shortening occurs as...range in which single transverse mode operation of a TE CO2 laser has been achieved. For the purposes of this program the optical cavity was

Reconfigurable optical interconnection network for multimode optical fiber sensor arrays

NASA Technical Reports Server (NTRS)

Chen, R. T.; Robinson, D.; Lu, H.; Wang, M. R.; Jannson, T.; Baumbick, R.

1992-01-01

A single-source, single-detector architecture has been developed to implement a reconfigurable optical interconnection network multimode optical fiber sensor arrays. The network was realized by integrating LiNbO3 electrooptic (EO) gratings working at the Raman Na regime and a massive fan-out waveguide hologram (WH) working at the Bragg regime onto a multimode glass waveguide. The glass waveguide utilized the whole substrate as a guiding medium. A 1-to-59 massive waveguide fan-out was demonstrated using a WH operating at 514 nm. Measured diffraction efficiency of 59 percent was experimentally confirmed. Reconfigurability of the interconnection was carried out by generating an EO grating through an externally applied electric field. Unlike conventional single-mode integrated optical devices, the guided mode demonstrated has an azimuthal symmetry in mode profile which is the same as that of a fiber mode.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Ashutosh, E-mail: asingh.rs.ece@iitbhu.ac.in; Center of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology; Jain, P. K.

In this paper, the effects of electron beam parameters and velocity spread on the RF behavior of a metallic photonic band gap (PBG) cavity gyrotron operating at 35 GHz with TE{sub 041}–like mode have been theoretically demonstrated. PBG cavity is used here to achieve a single mode operation of the overmoded cavity. The nonlinear time-dependent multimode analysis has been used to observe the beam-wave interaction behavior of the PBG cavity gyrotron, and a commercially available PIC code “CST Particle Studio” has been reconfigured to obtain 3D simulation results in order to validate the analytical values. The output power for this typicalmore » PBG gyrotron has been obtained ∼108 kW with ∼15.5% efficiency in a well confined TE{sub 041}–like mode, while all other competing modes have significantly low values of power output. The output power and efficiency of a gyrotron depend highly on the electron beam parameters and velocity spread. The influence of several electron beam parameters, e.g., beam voltage, beam current, beam velocity pitch factor, and DC magnetic field, on the PBG gyrotron operations has been investigated. This study would be helpful in optimising the electron beam parameters and estimating accurate RF output power of the high frequency PBG cavity based gyrotron oscillators.« less

Self-injection locked blue laser

NASA Astrophysics Data System (ADS)

Donvalkar, Prathamesh S.; Savchenkov, Anatoliy; Matsko, Andrey

2018-04-01

We demonstrate a 446.5 nm GaN semiconductor laser with sub-MHz linewidth. The linewidth reduction is achieved by locking the laser to a magnesium fluoride whispering gallery mode resonator characterized with 109 quality factor. Self-injection locking ensures single longitudinal mode operation of the laser.

Experimental evidence of mobility enhancement in short-channel ultra-thin body double-gate MOSFETs by magnetoresistance technique

NASA Astrophysics Data System (ADS)

Chaisantikulwat, W.; Mouis, M.; Ghibaudo, G.; Cristoloveanu, S.; Widiez, J.; Vinet, M.; Deleonibus, S.

2007-11-01

Double-gate transistor with ultra-thin body (UTB) has proved to offer advantages over bulk device for high-speed, low-power applications. There is thus a strong need to obtain an accurate understanding of carrier transport and mobility in such device. In this work, we report for the first time an experimental evidence of mobility enhancement in UTB double-gate (DG) MOSFETs using magnetoresistance mobility extraction technique. Mobility in planar DG transistor operating in single- and double-gate mode is compared. The influence of different scattering mechanisms in the channel is also investigated by obtaining mobility values at low temperatures. The results show a clear mobility improvement in double-gate mode compared to single-gate mode mobility at the same inversion charge density. This is explained by the role of volume inversion in ultra-thin body transistor operating in DG mode. Volume inversion is found to be especially beneficial in terms of mobility gain at low-inversion densities.

Liquid detection with InGaAsP semiconductor lasers having multiple short external cavities.

PubMed

Zhu, X; Cassidy, D T

1996-08-20

A liquid detection system consisting of a diode laser with multiple short external cavities (MSXC's) is reported. The MSXC diode laser operates single mode on one of 18 distinct modes that span a range of 72 nm. We selected the modes by setting the length of one of the external cavities using a piezoelectric positioner. One can measure the transmission through cells by modulating the injection current at audio frequencies and using phase-sensitive detection to reject the ambient light and reduce 1/f noise. A method to determine regions of single-mode operation by the rms of the output of the laser is described. The transmission data were processed by multivariate calibration techniques, i.e., partial least squares and principal component regression. Water concentration in acetone was used to demonstrate the performance of the system. A correlation coefficient of R(2) = 0.997 and 0.29% root-mean-square error of prediction are found for water concentration over the range of 2-19%.

Surface-emitting mid-infrared quantum cascade lasers with high-contrast photonic crystal resonators.

PubMed

Xu, Gangyi; Colombelli, Raffaele; Braive, Remy; Beaudoin, Gregoire; Le Gratiet, Luc; Talneau, Anne; Ferlazzo, Laurence; Sagnes, Isabelle

2010-05-24

We have developed surface-emitting single-mode quantum cascade lasers which employ high-contrast photonic-crystal resonators. The devices operate on band-edge states of the photonic band-structure. The mode profile and polarization characteristics of the band-edge modes are calculated by three-dimensional finite-difference time-domain simulation. Experimentally, the spectral properties, the far-field patterns, and the polarization characteristics of the lasers are determined and compared with simulations. The good agreement between the simulations and the experiments confirms that the hexapolar mode at the Gamma-point band-edge gives rise to lasing. By using a novel and advanced fabrication method, deep and vertical PhC holes are fabricated with no metal redeposition on the sidewalls, which improves the laser performance with respect to the current status. The angular of the output beam is approximately 15 masculine, and the side mode suppression ratio of the single mode emission is about 25 dB. The threshold current density at 78 K and the maximum operation temperature are 7.6 kA/cm2 and 220 K, respectively. The performance is mainly limited by the loss induced by surface plasmon waveguide, which can be overcome by using an optimized dielectric waveguide structure.

External amplitude and frequency modulation of a terahertz quantum cascade laser using metamaterial/graphene devices.

PubMed

Kindness, S J; Jessop, D S; Wei, B; Wallis, R; Kamboj, V S; Xiao, L; Ren, Y; Braeuninger-Weimer, P; Aria, A I; Hofmann, S; Beere, H E; Ritchie, D A; Degl'Innocenti, R

2017-08-09

Active control of the amplitude and frequency of terahertz sources is an essential prerequisite for exploiting a myriad of terahertz applications in imaging, spectroscopy, and communications. Here we present a optoelectronic, external modulation technique applied to a terahertz quantum cascade laser which holds the promise of addressing a number of important challenges in this research area. A hybrid metamaterial/graphene device is implemented into an external cavity set-up allowing for optoelectronic tuning of feedback into a quantum cascade laser. We demonstrate powerful, all-electronic, control over the amplitude and frequency of the laser output. Full laser switching is performed by electrostatic gating of the metamaterial/graphene device, demonstrating a modulation depth of 100%. External control of the emission spectrum is also achieved, highlighting the flexibility of this feedback method. By taking advantage of the frequency dispersive reflectivity of the metamaterial array, different modes of the QCL output are selectively suppressed using lithographic tuning and single mode operation of the multi-mode laser is enforced. Side mode suppression is electrically modulated from ~6 dB to ~21 dB, demonstrating active, optoelectronic modulation of the laser frequency content between multi-mode and single mode operation.

Durability evaluation of reversible solid oxide cells

NASA Astrophysics Data System (ADS)

Zhang, Xiaoyu; O'Brien, James E.; O'Brien, Robert C.; Housley, Gregory K.

2013-11-01

An experimental investigation on the performance and durability of single solid oxide cells (SOCs) is under way at the Idaho National Laboratory. Reversible operation of SOCs includes electricity generation in the fuel cell mode and hydrogen generation in the electrolysis mode. Degradation is a more significant issue when operating SOCs in the electrolysis mode. In order to understand and mitigate the degradation issues in high temperature electrolysis, single SOCs with different configurations from several manufacturers have been evaluated for initial performance and long-term durability. Cells were obtained from four industrial partners. Cells from Ceramatec Inc. and Materials and Systems Research Inc. (MSRI) showed improved durability in electrolysis mode compared to previous stack tests. Cells from Saint Gobain Advanced Materials Inc. (St. Gobain) and SOFCPower Inc. demonstrated stable performance in the fuel cell mode, but rapid degradation in the electrolysis mode, especially at high current density. Electrolyte-electrode delamination was found to have a significant impact on degradation in some cases. Enhanced bonding between electrolyte and electrode and modification of the electrode microstructure helped to mitigate degradation. Polarization scans and AC impedance measurements were performed during the tests to characterize cell performance and degradation.

Development of all-solid-state coherent 589 nm light source: toward the realization of sodium lidar and laser guide star adaptive optics

NASA Astrophysics Data System (ADS)

Saito, Norihito; Akagawa, Kazuyuki; Kato, Mayumi; Takazawa, Akira; Hayano, Yutaka; Saito, Yoshihiko; Ito, Meguru; Takami, Hideki; Iye, Masanori; Wada, Satoshi

2006-12-01

We report an all-solid-state coherent 589 nm light source in single-pass sum-frequency generation (SFG) with actively mode-locked Nd:YAG lasers for the realization of sodium lidar and laser guide star adaptive optics. The Nd:YAG lasers are constructed as a LD-side-pumped configuration and are operated at 1064 and 1319 nm for 589 nm light generation in SFG. Output powers of 16.5 and 5.3 W at 1064 and 1319 nm are obtained with two pumping chambers. Each chamber consisted of three 80-W-LD arrays. Single transverse mode TEM 00; M2 ~1.1 is achieved with adjustment of cavity length considering thermal lens effect with increase of input LD power. The cavity length is set to approximately 1 m. Accordingly the mode-locked lasers are operated at a repetition rate of approximately 150 MHz. Synchronization of two pulse trains at 1064 and 1319 nm is accomplished by control of phase difference between two radio frequencies input in acousto-optic mode-lockers. Then temporal delay is controlled with a resolution of 37 ps/degree. Pump beams are mixed in periodically poled stoichiometric lithium tantalate (PPSLT) without an antireflection coating. The effective aperture and length of the crystal are 0.5 × 2 mm2 and 15 mm. When input intensity is set at 5.6 MW/cm , an average output power of 4.6 W is obtained at 589.159 nm. Precise tuning to the sodium D II line is accomplished by thermal control of etalons set in the Nd:YAG lasers. The output power at 589.159 nm is stably maintained within +/-1.2% for 8 hours.

Experimental measurement and numerical analysis of group velocity dispersion in cladding modes of an endlessly single-mode photonic crystal fiber

NASA Astrophysics Data System (ADS)

Baselt, Tobias; Taudt, Christopher; Nelsen, Bryan; Lasagni, Andrés. Fabián.; Hartmann, Peter

2017-06-01

The optical properties of the guided modes in the core of photonic crystal fibers (PCFs) can be easily manipulated by changing the air-hole structure in the cladding. Special properties can be achieved in this case such as endless singlemode operation. Endlessly single-mode fibers, which enable single-mode guidance over a wide spectral range, are indispensable in the field of fiber technology. A two-dimensional photonic crystal with a silica central core and a micrometer-spaced hexagonal array of air holes is an established method to achieve endless single-mode properties. In addition to the guidance of light in the core, different cladding modes occur. The coupling between the core and the cladding modes can affect the endlessly single-mode guides. There are two possible ways to determine the dispersion: measurement and calculation. We calculate the group velocity dispersion (GVD) of different cladding modes based on the measurement of the fiber structure parameters, the hole diameter and the pitch of a presumed homogeneous hexagonal array. Based on the scanning electron image, a calculation was made of the optical guiding properties of the microstructured cladding. We compare the calculation with a method to measure the wavelength-dependent time delay. We measure the time delay of defined cladding modes with a homemade supercontinuum light source in a white light interferometric setup. To measure the dispersion of cladding modes of optical fibers with high accuracy, a time-domain white-light interferometer based on a Mach-Zehnder interferometer is used. The experimental setup allows the determination of the wavelengthdependent differential group delay of light travelling through a thirty centimeter piece of test fiber in the wavelength range from VIS to NIR. The determination of the GVD using different methods enables the evaluation of the individual methods for characterizing the cladding modes of an endlessly single-mode fiber.

Singlemode 1.1 μm InGaAs quantum well microstructured photonic crystal VCSEL

NASA Astrophysics Data System (ADS)

Stevens, Renaud; Gilet, Philippe; Larrue, Alexandre; Grenouillet, Laurent; Olivier, Nicolas; Grosse, Philippe; Gilbert, Karen; Teysseyre, Raphael; Chelnokov, Alexei

2008-02-01

In this article, we present our results on long wavelength (1.1 μm) single-mode micro-structured photonic crystal strained InGaAs quantum wells VCSELs for optical interconnection applications. Single fundamental mode roomtemperature continuous-wave lasing operation was demonstrated for devices designed and processed with a number of different two-dimensional etched patterns. The conventional epitaxial structure was grown by Molecular Beam Epitaxy (MBE) and contains fully doped GaAs/AlGaAs DBRs, one oxidation layer and three strained InGaAs quantum wells. The holes were etched half-way through the top-mirror following various designs (triangular and square lattices) and with varying hole's diameters and pitches. At room temperature and in continuous wave operation, micro-structured 50 µm diameter mesa VCSELs with 10 μm oxidation aperture exhibited more than 1 mW optical power, 2 to 5 mA threshold currents and more than 30 dB side mode suppression ratio at a wavelength of 1090 nm. These structures show slight power reduction but similar electrical performances than unstructured devices. Systematic static electrical, optical and spectral characterization was performed on wafer using an automated probe station. Numerical modeling using the MIT Photonic-Bands (MPB [1]) package of the transverse modal behaviors in the photonic crystal was performed using the plane wave method in order to understand the index-guiding effects of the chosen patterns, and to further optimize the design structures for mode selection at extended wavelength range.

ELECTROSTATIC MEMORY SYSTEM

DOEpatents

Chu, J.C.

1958-09-23

An improved electrostatic memory system is de scribed fer a digital computer wherein a plarality of storage tubes are adapted to operate in either of two possible modes. According to the present irvention, duplicate storage tubes are provided fur each denominational order of the several binary digits. A single discriminator system is provided between corresponding duplicate tubes to determine the character of the infurmation stored in each. If either tube produces the selected type signal, corresponding to binazy "1" in the preferred embodiment, a "1" is regenerated in both tubes. In one mode of operation each bit of information is stored in two corresponding tubes, while in the other mode of operation each bit is stored in only one tube in the conventional manner.

Microstructured optical fibers for terahertz waveguiding regime by using an analytical field model

NASA Astrophysics Data System (ADS)

Sharma, Dinesh Kumar; Sharma, Anurag; Tripathi, Saurabh Mani

2017-12-01

Microstructured optical fibres (MOFs) are seen as novel optical waveguide for the potential applications in the terahertz (THz) band as they provide a flexible route towards THz waveguiding. Using the analytical field model (Sharma et al., 2014) developed for index-guiding MOFs with hexagonal lattice of circular air-holes in the photonic crystal cladding; we aim to study the propagation characteristics such as effective index, near and the far-field radiation patterns and its evolution from near-to-far-field domain, spot size, effective mode area, and the numerical aperture at the THz regime. Further, we present an analytical field expression for the next higher-order mode of the MOF for studying the modal properties at terahertz frequencies. Also, we investigate the mode cut-off conditions for identifying the single-mode operation range at THz frequencies. Emphasis is put on studying the coupling characteristics of MOF geometries for efficient mode coupling. Comparisons with available experimental and numerical simulation results, e.g., those based on the full-vector finite element method (FEM) and the finite-difference frequency-domain (FDFD) method have been included.

Confirmation of filament dissolution behavior by analyzing electrical field effect during reset process in oxide-based RRAM

NASA Astrophysics Data System (ADS)

Pan, Chih-Hung; Chang, Ting-Chang; Tsai, Tsung-Ming; Chang, Kuan-Chang; Chu, Tian-Jian; Lin, Wen-Yan; Chen, Min-Chen; Sze, Simon M.

2016-09-01

In this letter, we demonstrate completely different characteristics with different operating modes and analyze the electrical field effect to confirm the filament dissolution behavior. The device exhibited a larger memory window when using a single voltage sweep method during reset process rather than the traditional double sweep method. The phenomenon was verified by using fast I-V measurement to simulate the two operating methods. A better high resistance state (HRS) will be obtained with a very short rising time pulse, but quite notably, lower power consumption was needed. We proposed the electrical field effect to explain the phenomenon and demonstrate distribution by COMSOL simulation.

Implementation and flight-test of a multi-mode rotorcraft flight-control system for single-pilot use in poor visibility

NASA Technical Reports Server (NTRS)

Hindson, William S.

1987-01-01

A flight investigation was conducted to evaluate a multi-mode flight control system designed according to the most recent recommendations for handling qualities criteria for new military helicopters. The modes and capabilities that were included in the system are those considered necessary to permit divided-attention (single-pilot) lowspeed and hover operations near the ground in poor visibility conditions. Design features included mode-selection and mode-blending logic, the use of an automatic position-hold mode that employed precision measurements of aircraft position, and a hover display which permitted manually-controlled hover flight tasks in simulated instrument conditions. Pilot evaluations of the system were conducted using a multi-segment evaluation task. Pilot comments concerning the use of the system are provided, and flight-test data are presented to show system performance.

Index-antiguided planar waveguide lasers with large mode area

NASA Astrophysics Data System (ADS)

Liu, Yuanye

The on-going research and application interests with high power large-mode-area (LMA) waveguide lasers, especially in fiber geometry, at the beginning of this century drive the development of many novel waveguide designs. Index antiguiding, proposed by Siegman in 2003, is among one of them. The goal for index antiguiding is to introduce transversal modal loss with the relative simple waveguide design while maintain single transverse mode operation for good beam quality. The idea which is selectively support of fundamental mode is facilitated by involving certain level of signal regeneration inside the waveguide core. Since the modal loss is closed associated with waveguide design parameters such as core size and refractive index, the amount of gain inside the core provides active control of transverse modes inside index-antiguiding waveguide. For example, fundamental transverse mode inside such waveguide can be excited and propagate lossless when sufficient optical gain is provided. This often requires doped waveguide core and optical pumping at corresponding absorption band. However, the involvement of optical pumping also has its consequences. Phenomena such as thermal-optic effect and gain spatial hole-burning which are commonly found in bulk lasers request attention when scaling up output power with LMA index-antiguided waveguide amplifiers and resonators. In response, three key challenges of index-antiguided planar waveguide lasers, namely, guiding mechanism, power efficiency and transverse mode discrimination, are analyzed theoretically and experimentally in this dissertation. Experiments are based on two index-antiguided planar waveguide chips, whose core thickness are 220 microm and 400 microm respectively. The material of waveguide core is 1% Neodymium-doped Yttrium Aluminium garnet, or Nd:YAG while the cladding is made from Terbium Gallium garnet, or TGG. Due to the face pumping and limited pump power, it is found, with 220 microm-thick-core chip, that the guidance of the fundamental transverse mode along two orthogonal directions in a transverse plane is different. Along the bounded direction, index antiguiding prevails with negligible thermal refractive focusing while along the unbounded direction, the lasing mode is guided by thermal refractive focusing with negligible quadratic gain focusing. It is also founded that the quadratic thermal focusing will dominate the mode guidance in 220 microm chip with the help of additional pump. All these discovery calls for an active thermal control. The modal discriminative loss, though beneficial for transverse mode control, yet reduces the lasing efficiency. To model it, a 3-D lasing output power calculation model is developed based on spatial rate equations. The simulation results show good agreement with experiment data where slope efficiency curve are measured using multiple output couplers. The 10% slope efficiency with respect to incident pump power is the highest slope efficiency recorded in index-antiguided waveguide continuous-wave lasers. The model indicates more efficient pump absorption can facilitate further power scaling. The role of the modal discriminative loss in transverse mode competition is discussed. A theoretical model based on Rigrod analysis and spatial hole-burning is developed. The simulation shows reasonable agreement with experiment results in both chips. The single fundamental mode operation up to 10 times above the lasing threshold for 220 microm chip is achieved, which is limited by the incident pump power. However, as the core size increases, the modal distributed loss due to the index antiguiding is found to be less effective in transverse mode control. Other modal loss is needed to facilitate the suppression of higher-order modes. Based on the model, a strategy is proposed aiming to maximize the single mode output. It is also noted that the transverse mode competition model is also suitable for other lasers system with well-defined modal loss. Based on the models and experiment data, the index-antiguided planar waveguide lasers are proved to be capable of maintaining large-mode-area single transverse mode operation with the potential of power scaling. However, it is also shown that proper waveguide design is essential. The remaining challenges are the material choices for waveguide fabrication, especially for high power applications.

AlGaAs heterojunction lasers

NASA Technical Reports Server (NTRS)

Goldstein, B.; Pultz, G. N.; Carlin, D. B.; Slavin, S. E.; Ettenberg, M.

1988-01-01

The characterization of 8300 A lasers was broadened, especially in the area of beam quality. Modulation rates up to 2 Gbit/sec at output powers of 20 mW were observed, waveform fidelity was fully adequate for low BER data transmission, and wavefront measurements showed that phase aberrations were less than lamda/50. Also, individually addressable arrays of up to ten contiguous diode lasers were fabricated and tested. Each laser operates at powers up to 30 mW CW in single spatial mode. Shifting the operating wavelength of the basic CSP laser from 8300 A to 8650 A was accomplished by the addition of Si to the active region. Output power has reached 100 mW single mode, with excellent far field wave front properties. Operating life is currently approx. 1000 hrs at 35 mW CW. In addition, laser reliability, for operation at both 8300 A and 8650 A, has profited significantly from several developments in the processing procedures.

Theoretical study on mode competition between fundamental and second harmonic modes in a 0.42 THz gyrotron with gradually tapered complex cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Qixiang, E-mail: zxqi1105@gmail.com; Yu, Sheng; Zhang, Tianzhong

2015-10-15

In this paper, the nonlinear dynamics of mode competition in the complex cavity gyrotron are studied by using multi-frequency, time-dependent theory with the cold-cavity longitudinal profile approximation. Based on the theory, a code is written to simulate the mode competition in the gradually tapered complex cavity gyrotron operating at second harmonic oscillation. The simulations tracking seven competition modes show that single mode oscillation of the desired mode TE{sub 17.4} at 150 kW level can be expected with proper choice of operating parameters. Through studying on mode competition, it is proved that the complex cavity has a good capability for suppressing themore » mode competition. Meanwhile, it is found that TE{sub 17.3} could be excited in the first cavity as a competition mode when the gyrotron operating at large beam current, which leads to that TE{sub 17.3} and TE{sub 17.4} with different frequencies can coexist stably in the complex cavity gyrotron with very close amplitudes. Thus, the complex cavity might be used for multi-frequency output gyrotron.« less

Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers.

PubMed

Jain, Deepak; Jung, Yongmin; Barua, Pranabesh; Alam, Shaiful; Sahu, Jayanta K

2015-03-23

In this paper, we report the mode area scaling of a rare-earth doped step index fiber by using low numerical aperture. Numerical simulations show the possibility of achieving an effective area of ~700 um² (including bend induced effective area reduction) at a bend diameter of 32 cm from a 35 μm core fiber with a numerical aperture of 0.038. An effective single mode operation is ensured following the criterion of the fundamental mode loss to be lower than 0.1 dB/m while ensuring the higher order modes loss to be higher than 10 dB/m at a wavelength of 1060 nm. Our optimized modified chemical vapor deposition process in conjunction with solution doping process allows fabrication of an Yb-doped step index fiber having an ultra-low numerical aperture of ~0.038. Experimental results confirm a Gaussian output beam from a 35 μm core fiber validating our simulation results. Fiber shows an excellent laser efficiency of ~81%and aM² less than 1.1.

Independent Orbiter Assessment (IOA): Analysis of the remote manipulator system

NASA Technical Reports Server (NTRS)

Tangorra, F.; Grasmeder, R. F.; Montgomery, A. D.

1987-01-01

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items (PCIs). To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The independent analysis results for the Orbiter Remote Manipulator System (RMS) are documented. The RMS hardware and software are primarily required for deploying and/or retrieving up to five payloads during a single mission, capture and retrieve free-flying payloads, and for performing Manipulator Foot Restraint operations. Specifically, the RMS hardware consists of the following components: end effector; displays and controls; manipulator controller interface unit; arm based electronics; and the arm. The IOA analysis process utilized available RMS hardware drawings, schematics and documents for defining hardware assemblies, components and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Of the 574 failure modes analyzed, 413 were determined to be PCIs.

Acceleration of high-pressure-ratio single-spool turbojet engine as determined from component performance characteristics I : effect of air bleed at compressor outlet

NASA Technical Reports Server (NTRS)

Rebeske, John J , Jr; Rohlik, Harold E

1953-01-01

An analytical investigation was made to determine from component performance characteristics the effect of air bleed at the compressor outlet on the acceleration characteristics of a typical high-pressure-ratio single-spool turbojet engine. Consideration of several operating lines on the compressor performance map with two turbine-inlet temperatures showed that for a minimum acceleration time the turbine-inlet temperature should be the maximum allowable, and the operating line on the compressor map should be as close to the surge region as possible throughout the speed range. Operation along such a line would require a continuously varying bleed area. A relatively simple two-step area bleed gives only a small increase in acceleration time over a corresponding variable-area bleed. For the modes of operation considered, over 84 percent of the total acceleration time was required to accelerate through the low-speed range ; therefore, better low-speed compressor performance (higher pressure ratios and efficiencies) would give a significant reduction in acceleration time.

Fiber-based laser MOPA transmitter packaging for space environment

NASA Astrophysics Data System (ADS)

Stephen, Mark; Yu, Anthony; Chen, Jeffrey; Numata, Kenji; Wu, Stewart; Gonzales, Brayler; Han, Lawrence; Fahey, Molly; Plants, Michael; Rodriguez, Michael; Allan, Graham; Abshire, James; Nicholson, Jeffrey; Hariharan, Anand; Mamakos, William; Bean, Brian

2018-02-01

NASA's Goddard Space Flight Center has been developing lidar to remotely measure CO2 and CH4 in the Earth's atmosphere. The ultimate goal is to make space-based satellite measurements with global coverage. We are working on maturing the technology readiness of a fiber-based, 1.57-micron wavelength laser transmitter designed for use in atmospheric CO2 remote-sensing. To this end, we are building a ruggedized prototype to demonstrate the required power and performance and survive the required environment. We are building a fiber-based master oscillator power amplifier (MOPA) laser transmitter architecture. The laser is a wavelength-locked, single frequency, externally modulated DBR operating at 1.57-micron followed by erbium-doped fiber amplifiers. The last amplifier stage is a polarization-maintaining, very-large-mode-area fiber with 1000 μm2 effective area pumped by a Raman fiber laser. The optical output is single-frequency, one microsecond pulses with >450 μJ pulse energy, 7.5 KHz repetition rate, single spatial mode, and < 20 dB polarization extinction.

Clock and carrier recovery in high-speed coherent optical communication systems

NASA Astrophysics Data System (ADS)

Amado, Sofia B.; Ferreira, Ricardo; Costa, Pedro S.; Guiomar, Fernando P.; Ziaie, Somayeh; Teixeira, António L.; Muga, Nelson J.; Pinto, Armando N.

2014-08-01

In this paper, the implementations of clock and carrier recovery in digital domain are analyzed. Hardware implementation details, resources estimation and real-time results are presented. Analog-to-Digital Converters (ADC), operating at 1.25Gsa/s, and a Virtex-6 Field-Programmable Gate Array (FPGA), have been used, allowing the implementation of a real-time Quadrature Phase Shift Keying (QPSK) system operating at 1.25Gb/s. The real-time mode operation is successfully demonstrated over 80 km of Standard Single Mode Fiber (SSMF).

240 GHz pedestal-free colliding-pulse mode-locked laser with a wide operation range

NASA Astrophysics Data System (ADS)

Hou, L.; Haji, M.; Marsh, J. H.

2014-11-01

A 240 GHz, sixth-harmonic monolithic ~1.55 μm colliding-pulse mode-locked laser is reported using a three-quantum-well active layer design and a passive far-field reduction layer. The device emits 0.88 ps pulses with a peak power of 65 mW and intermediate longitudinal modes suppressed by >30 dB. The device demonstrates a wide operation range compared to the conventional five-quantum-well design as well as having a low divergence angle (12.7° × 26.3°), granting a twofold improvement in butt-coupling efficiency into a flat cleaved single-mode fibre.

Design and fabrication of N x N optical couplers based on organic polymer optical waveguides

NASA Astrophysics Data System (ADS)

Krchnavek, Robert R.; Rode, Daniel L.

1994-08-01

In this report, we examine the design and fabrication of a planar, 10x10 optical coupler utilizing photopolymerizable organic polymers. Background information on the theory of operation of the coupler culminating in a set of design equations is presented. The details of the material processing are described, including the preparation of monomer mixtures that result in single-mode polymer waveguides (lambda = 1300 nm) that have core dimensions approximately equal to those of single-mode fiber. This is necessary to insure high coupling efficiency between the planar device and optical fiber. A unique method of aligning and attaching optical fibers to the coupler is demonstrated. This method relies on patterned alignment ways, a transcision cut, and single-mode D-fiber. A theoretical analysis of the in situ monitoring technique used to fabricate the single-mode D-fiber is presented and compared favorably with the experimental results. Finally, the 10x10 coupler is characterized. We have measured an excess loss of approximately 8 dB.

Multi-angle VECSEL cavities for dispersion control and multi-color operation

NASA Astrophysics Data System (ADS)

Baker, Caleb; Scheller, Maik; Laurain, Alexandre; Yang, Hwang-Jye; Ruiz Perez, Antje; Stolz, Wolfgang; Addamane, Sadhvikas J.; Balakrishnan, Ganesh; Jones, R. Jason; Moloney, Jerome V.

2017-02-01

We present a novel Vertical External Cavity Surface Emitting Laser (VECSEL) cavity design which makes use of multiple interactions with the gain region under different angles of incidence in a single round trip. This design allows for optimization of the net, round-trip Group Delay Dispersion (GDD) by shifting the GDD of the gain via cavity fold angle while still maintaining the high gain of resonant structures. The effectiveness of this scheme is demonstrated with femtosecond-regime pulses from a resonant structure and record pulse energies for the VECSEL gain medium. In addition, we show that the interference pattern of the intracavity mode within the active region, resulting from the double-angle multifold, is advantageous for operating the laser in CW on multiple wavelengths simultaneously. Power, noise, and mode competition characterization is presented.

Using multi-ring structure for suppression of mode competition in stable single-longitudinal-mode erbium fiber laser

NASA Astrophysics Data System (ADS)

Yeh, Chien-Hung; Huang, Tzu-Jung; Yang, Zi-Qing; Chow, Chi-Wai

2017-12-01

In this demonstration, a stable and tunable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser with multiple-ring configuration is proposed and investigated. The proposed compound-ring structure can create different free spectrum ranges (FSRs) to result in the mode-filter effect based on the Vernier effect for suppressing the other modes. Additionally, the output stabilization of power and wavelength in the proposed EDF multiple-ring laser are also discussed.

Coupled ridge waveguide distributed feedback quantum cascade laser arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ying-Hui; Zhang, Jin-Chuan, E-mail: zhangjinchuan@semi.ac.cn; Yan, Fang-Liang

2015-04-06

A coupled ridge waveguide quantum cascade laser (QCL) array consisting of fifteen elements with parallel integration was presented. In-phase fundamental mode operation in each element is secured by both the index-guided nature of the ridge and delicate loss management by properly designed geometries of the ridges and interspaces. Single-lobe lateral far-field with a nearly diffraction limited beam pattern was obtained. By incorporating a one-dimensional buried distributed feedback grating, the in-phase-operating coupled ridge waveguide QCL design provides an efficient solution to obtaining high output power and stable single longitudinal mode emission. The simplicity of this structure and fabrication process makes thismore » approach attractive to many practical applications.« less

Distillation and purification of symmetric entangled Gaussian states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fiurasek, Jaromir

2010-10-15

We propose an entanglement distillation and purification scheme for symmetric two-mode entangled Gaussian states that allows to asymptotically extract a pure entangled Gaussian state from any input entangled symmetric Gaussian state. The proposed scheme is a modified and extended version of the entanglement distillation protocol originally developed by Browne et al. [Phys. Rev. A 67, 062320 (2003)]. A key feature of the present protocol is that it utilizes a two-copy degaussification procedure that involves a Mach-Zehnder interferometer with single-mode non-Gaussian filters inserted in its two arms. The required non-Gaussian filtering operations can be implemented by coherently combining two sequences ofmore » single-photon addition and subtraction operations.« less

Low-bending loss and single-mode operation in few-mode optical fiber

NASA Astrophysics Data System (ADS)

Yin, Ping; Wang, Hua; Chen, Ming-Yang; Wei, Jin; Cai, Zhi-Min; Li, Lu-Ming; Yang, Ji-Hai; Zhu, Yuan-Feng

2016-10-01

The technique of eliminating the higher-order modes in a few-mode optical fiber is proposed. The fiber is designed with a group of defect modes in the cladding. The higher-order modes in the fiber can be eliminated by bending the fiber to induce strong coupling between the defect modes and the higher-order modes. Numerical simulation shows the bending losses of the LP01 mode are lower than 1.5×10-4 dB/turn for the wavelength shorter than 1.625 μm. The proposed fiber can be bent multiple turns at small bending radius which are preferable for FTTH related applications.

Inline microring reflector for photonic applications

NASA Astrophysics Data System (ADS)

Kang, Young Mo

The microring is a compact resonator that is used as a versatile building block in photonic circuits ranging from filters, modulators, logic gates, sensors, switches, multiplexers, and laser cavities. The Bragg grating is a periodic structure that allows the selection of a narrow bandwidth of spectrum for stable lasing operation. In this dissertation, we study analysis and simulations of a compact microring based reflector assembled by forming a Bragg grating into a loop. With the appropriate design, the microring resonance can precisely align with the reflection peak of the grating while all other peaks are suppressed by reflection nulls of the grating. The field buildup at the resonance effectively amplifies small reflection of the grating, thereby producing significant overall reflection from the ring, and it is possible to achieve a stable narrow linewidth compact laser by forming a single mode laser cavity. The device operation principle is studied from two distinct perspectives; the first looks at coupling of two contra-directional traveling waves within the ring whereas the second aspect investigates relative excitation of the two competing microring resonant modes. In the former method, we relate the steady state amplitudes of the two traveling waves to the reflection spectrum of the grating and solve for the reflection and transmission response for each wavelength of interest. In the latter approach, we expand the field in terms of the resonant modes of the ring cavity and derive transfer functions for reflection and transmission from the nearby mode frequencies. The angular periodicity of the reflective microring geometry allows us to effectively simulate the resonant modes from a computational domain of a single period grating when the continuity boundary condition is applied. We successfully predict the reflection and transmission response of a Si3N 4/SiO2 microring reflector using this method---otherwise too large to carry out full-wave simulation---and show that the prediction agrees very well with the measurement result.

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber laser based on one polarization-maintaining fiber Bragg grating incorporating saturable absorber

NASA Astrophysics Data System (ADS)

Feng, Suchun; Xu, Ou; Lu, Shaohua; Chen, Ming; Jian, Shuisheng

2009-08-01

Switchable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber laser at room temperature is demonstrated. One fiber Bragg grating (FBG) directly written in a polarization-maintaining and photosensitive erbiumdoped fiber (PMPEDF) as the wavelength-selective component is used in a linear laser cavity. Due to the polarization hole burning (PHB) enhanced by the polarization-maintaining fiber Bragg grating (PMFBG), the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.202 nm by adjusting a polarization controller (PC). The stable SLM operation is guaranteed by a saturable absorber (SA). The optical signal-tonoise ratio (OSNR) of the laser is over 40 dB. The amplitude variation in nearly one and half an hour is less than 0.5 dB for both wavelengths.

Highly versatile in-reflection photonic crystal fibre interferometer

NASA Astrophysics Data System (ADS)

Jha, Rajan; Villatoro, Joel; Kreuzer, Mark; Finazzi, Vittoria; Pruneri, Valerio

2009-10-01

We report a simple and highly versatile photonic crystal fiber (PCF) interferometer that operates in reflection mode. The device consists of a short section of PCF fusion spliced at the distal end of a standard single mode fiber. The air-holes of the PCF are intentionally collapsed over a microscopic region around the splice. The collapsed region broadens the propagating mode because of diffraction. This allows the coupling and recombination of two PCF modes. Depending on the PCF structure two core modes or a core and a cladding mode can be excited. In either case the devices exhibit sinusoidal interference patterns with fringe spacing depending on the PCF length. The interferometers are highly stable over time and can operate at high temperatures with minimal degradation. The interferometers are suitable for highresolution sensing of strain, refractive index (biosensing), gases, volatile organic compounds, etc.

Model 0A wind turbine generator FMEA

NASA Technical Reports Server (NTRS)

Klein, William E.; Lalli, Vincent R.

1989-01-01

The results of Failure Modes and Effects Analysis (FMEA) conducted for the Wind Turbine Generators are presented. The FMEA was performed for the functional modes of each system, subsystem, or component. The single-point failures were eliminated for most of the systems. The blade system was the only exception. The qualitative probability of a blade separating was estimated at level D-remote. Many changes were made to the hardware as a result of this analysis. The most significant change was the addition of the safety system. Operational experience and need to improve machine availability have resulted in subsequent changes to the various systems which are also reflected in this FMEA.

Thermal neutron detector and gamma-ray spectrometer utilizing a single material

DOEpatents

Stowe, Ashley; Burger, Arnold; Lukosi, Eric

2017-05-02

A combined thermal neutron detector and gamma-ray spectrometer system, including: a detection medium including a lithium chalcopyrite crystal operable for detecting thermal neutrons in a semiconductor mode and gamma-rays in a scintillator mode; and a photodetector coupled to the detection medium also operable for detecting the gamma rays. Optionally, the detection medium includes a .sup.6LiInSe.sub.2 crystal. Optionally, the detection medium comprises a compound formed by the process of: melting a Group III element; adding a Group I element to the melted Group III element at a rate that allows the Group I and Group III elements to react thereby providing a single phase I-III compound; and adding a Group VI element to the single phase I-III compound and heating; wherein the Group I element includes lithium.

An expert system shell for inferring vegetation characteristics: Implementation of additional techniques (task E)

NASA Technical Reports Server (NTRS)

Harrison, P. Ann

1992-01-01

The NASA VEGetation Workbench (VEG) is a knowledge based system that infers vegetation characteristics from reflectance data. The VEG subgoal PROPORTION.GROUND.COVER has been completed and a number of additional techniques that infer the proportion ground cover of a sample have been implemented. Some techniques operate on sample data at a single wavelength. The techniques previously incorporated in VEG for other subgoals operated on data at a single wavelength so implementing the additional single wavelength techniques required no changes to the structure of VEG. Two techniques which use data at multiple wavelengths to infer proportion ground cover were also implemented. This work involved modifying the structure of VEG so that multiple wavelength techniques could be incorporated. All the new techniques were tested using both the VEG 'Research Mode' and the 'Automatic Mode.'

Theory of some laser noise effects.

NASA Technical Reports Server (NTRS)

Wang, Y. K.; Lamb, W. E., Jr.

1973-01-01

A simple version of the semiclassical theory is applied to the shot effect. Considerations of thermal noise reported by Lamb (1965) are extended to take into account amplitude fluctuations. The laser is considered to be a lossy cavity of the Fabry-Perot type in single-mode operation with a circular frequency driven by an inverted population of active atoms. The electric field is taken to be transverse to the cavity axis. The amplitude and phase are assumed to be slowly varying functions which satisfy two self-consistency equations.

Feasibility study of generating ultra-high harmonic radiation with a single stage echo-enabled harmonic generation scheme

NASA Astrophysics Data System (ADS)

Zhou, Kaishang; Feng, Chao; Wang, Dong

2016-10-01

The echo enabled harmonic generation (EEHG) scheme holds the ability for the generation of fully coherent soft x-ray free-electron laser (FEL) pulses directly from external UV seeding sources. In this paper, we study the feasibility of using a single stage EEHG to generate coherent radiation in the "water window" and beyond. Using the high-order operating modes of the EEHG scheme, intensive numerical simulations have been performed considering various three-dimensional effects. The simulation results demonstrated that coherent soft x-ray radiation at 150th harmonic (1.77 nm) of the seed can be produced by a single stage EEHG. The decreasing of the final bunching factor at the desired harmonic caused by intra beam scattering (IBS) effect has also been analyzed.

Intermodal Parametric Frequency Conversion in Optical Fibers

NASA Astrophysics Data System (ADS)

Demas, Jeffrey D.

Lasers are an essential technology enabling countless fields of optics, however, their operation wavelengths are limited to isolated regions across the optical spectrum due to the need for suitable gain media. Parametric frequency conversion (PFC) is an attractive means to convert existing lasers to new colors using nonlinear optical interactions rather than the material properties of the host medium, allowing for the development of high power laser sources across the entire optical spectrum. PFC in bulk chi(2) crystals has led to the development of the optical parametric oscillator, which is currently the standard source for high power light at non-traditional wavelengths in the laboratory setting. Ideally, however, one could implement PFC in an optical fiber, thus leveraging the crucial benefits of a guided-wave geometry: alignment-free, compact, and robust operation. Four-wave mixing (FWM) is a nonlinear effect in optical fibers that can be used to convert frequencies, the major challenge being conservation of momentum, or phase matching, between the interacting light waves. Phase matching can be satisfied through the interaction of different spatial modes in a multi-mode fiber, however, previous demonstrations have been limited by mode stability and narrow-band FWM gain. Alternatively, phase matching within the fundamental mode can be realized in high-confinement waveguides (such as photonic crystal fibers), but achieving the anomalous waveguide dispersion necessary for phase matching at pump wavelengths near ˜1 mum (where the highest power fiber lasers emit) comes at the cost of reducing the effective area of the mode, thus limiting power-handling. Here, we specifically consider the class of Bessel-like LP0,m modes in step-index fibers. It has been shown that these modes can be selectively excited and guided stably for long lengths of fiber, and mode stability increases with mode order 'm'. The effective area of modes in these fibers can be very large (>6000 mum2 demonstrated) and is decoupled from dispersion, allowing for phase matching within a single mode in a power-scalable platform. Furthermore, step-index fibers can guide many different LP0,m modes, allowing access to a highly multi-moded basis set with which to study FWM interactions between different modes. In this thesis we develop techniques to excite, propagate, and characterize LP0,m modes in order to demonstrate FWM in two regimes: monomode interactions comprising waves all belonging to the same mode, and intermodal interactions between different modes. In the monomode regime we demonstrate parametric sources which operate at near-infrared wavelengths under-served by conventional fiber lasers, including 880, 974, 1173, and 1347 nm. The output pulses for these systems are ˜300 ps in duration and reach peak powers of ˜10 kW, representing, to the best our knowledge, the highest peak power fiber laser sources demonstrated at these wavelengths to date. In the intermodal regime, we demonstrate a cascade of FWM processes between different modes that lead to a series of discrete peaks in the visible portion of the spectrum, increasing monotonically in mode order from LP0,7 at 678 nm to LP0,16 at 443 nm. This cascade underscores the huge number of potential FWM interactions between different LP0,m modes available in a highly multi-mode fiber, which scale as N4 for N guided modes. Finally, we demonstrate a novel intermodal FWM process pumped between the LP0,4 and LP0,5 modes of a step-index fiber, which provides broadband FWM gain (63 nm at 1550 nm) while maintaining wavelength separations of nearly an octave (762 nm) - a result that cannot be replicated in the single-mode regime. We seed this process to generate a ˜10 kW, ˜300-ps pulsed fiber laser wavelength-tunable from 786-795 nm; representing a fiber analogue of the ubiquitous Ti:Sapphire laser.

The effect of macro-bending on power confinement factor in single mode fibers

NASA Astrophysics Data System (ADS)

Waluyo, T. B.; Bayuwati, D.; Mulyanto, I.

2018-03-01

One of the methods to determine the macro-bending effect in a single mode fiber is by calculating its power loss coefficient. We describe an alternative method by using the equation of fractional power in the fiber core. Knowing the fiber parameters such as its core radius, refractive indexes, and operating wavelength; we can calculate the V-number and the fractional power in the core. Because the value of the fiber refractive indexes and the propagation constant are affected by bending, we can calculate the value of the fractional power in the core as a function of the bending radius. We calculate the fractional power in the core of an SMF28 and SM600 fiber and, to verify our calculation, we measure its transmission loss using an optical spectrum analyzer. Our calculations and experimental results showed that for SMF28 fiber, there is about 4% power loss due to bending at 633 nm, about 8% at 1310 nm, about 20% at 1550 nm, and about 60% at 1064 nm. For SM600 fiber, there is about 6% power loss due to bending at 633 nm, about 11% at 850 nm, and this fiber is not suitable for operating wavelength beyond 1000 nm.

Advanced development of Pb-salt semiconductor lasers for the 8.0 to 15.0 micrometer spectral region

NASA Technical Reports Server (NTRS)

Linden, K. J.; Butler, J. F.; Nill, K. W.

1977-01-01

The technology was studied for producing Pb-salt diode lasers for the 8-51 micron spectral region suitable for use as local oscillators in a passive Laser Heterodyne Spectrometer (LHS). Consideration was given to long range NASA plans for the utilization of the passive LHS in a space shuttle environment. The general approach was to further develop the method of compositional interdiffusion (CID) recently reported, and used successfully at shorter wavelength. This technology was shown to provide an effective and reproducible method of producing a single-heterostructure (SH) diode of either the heterojunction or single-sided configuration. Performance specifications were exceeded in several devices, with single-ended CW power outputs as high as 0.88 milliwatts in a mode being achieved. The majority of the CID lasers fabricated had CW operating temperatures of over 60K; 30% of them operated CW above the boiling temperature of liquid nitrogen. CW operation above liquid nitrogen temperature was possible for wavelengths as long as 10.3 microns. Operation at 77K is significant with respect to space shuttle operations since its allows considerable simplification of cooling method.

Dual comb generation from a mode-locked fiber laser with orthogonally polarized interlaced pulses.

PubMed

Akosman, Ahmet E; Sander, Michelle Y

2017-08-07

Ultra-high precision dual-comb spectroscopy traditionally requires two mode-locked, fully stabilized lasers with complex feedback electronics. We present a novel mode-locked operation regime in a thulium-holmium co-doped fiber laser, a frequency-halved state with orthogonally polarized interlaced pulses, for dual comb generation from a single source. In a linear fiber laser cavity, an ultrafast pulse train composed of co-generated, equal intensity and orthogonally polarized consecutive pulses at half of the fundamental repetition rate is demonstrated based on vector solitons. Upon optical interference of the orthogonally polarized pulse trains, two stable microwave RF beat combs are formed, effectively down-converting the optical properties into the microwave regime. These co-generated, dual polarization interlaced pulse trains, from one all-fiber laser configuration with common mode suppression, thus provide an attractive compact source for dual-comb spectroscopy, optical metrology and polarization entanglement measurements.

Extended Testability Analysis Tool

NASA Technical Reports Server (NTRS)

Melcher, Kevin; Maul, William A.; Fulton, Christopher

2012-01-01

The Extended Testability Analysis (ETA) Tool is a software application that supports fault management (FM) by performing testability analyses on the fault propagation model of a given system. Fault management includes the prevention of faults through robust design margins and quality assurance methods, or the mitigation of system failures. Fault management requires an understanding of the system design and operation, potential failure mechanisms within the system, and the propagation of those potential failures through the system. The purpose of the ETA Tool software is to process the testability analysis results from a commercial software program called TEAMS Designer in order to provide a detailed set of diagnostic assessment reports. The ETA Tool is a command-line process with several user-selectable report output options. The ETA Tool also extends the COTS testability analysis and enables variation studies with sensor sensitivity impacts on system diagnostics and component isolation using a single testability output. The ETA Tool can also provide extended analyses from a single set of testability output files. The following analysis reports are available to the user: (1) the Detectability Report provides a breakdown of how each tested failure mode was detected, (2) the Test Utilization Report identifies all the failure modes that each test detects, (3) the Failure Mode Isolation Report demonstrates the system s ability to discriminate between failure modes, (4) the Component Isolation Report demonstrates the system s ability to discriminate between failure modes relative to the components containing the failure modes, (5) the Sensor Sensor Sensitivity Analysis Report shows the diagnostic impact due to loss of sensor information, and (6) the Effect Mapping Report identifies failure modes that result in specified system-level effects.

Investigation of single lateral mode for 852nm diode lasers with ridge waveguide design

NASA Astrophysics Data System (ADS)

Liu, Chu; Guan, Baolu; Mi, Guoxin; Liao, Yiru; Liu, Zhenyang; Li, Jianjun; Xu, Chen

2016-11-01

852nm Narrow linewidth lasers can be widely used in the field of ultra-fine spectrum measurement, Cs atomic clock control, satellite and optical fiber communication and so on. Furthermore, the stability of the single lateral mode is a very important condition to guarantee the narrow linewidth lasers. Here we investigate experimentally the influence of the narrow ridge structure and asymmetrical waveguide design on the stability single lateral mode of an 852nm diode laser. According to the waveguide theoretical analysis, ridge mesa etch depth (Δη , related to the refractive index difference of parallel to the junction) and ridge mesa width (the narrower the more control force to low order mode) are the main elements for lateral modes. In this paper, we designed different structures to investigate and verify major factors for lateral mode by experiment, and to confirm our thought. Finally, the 5μm mesa ridge laser, 800nm etch depth, with groove structure obtains excellent steady single lateral mode output by 150mA operating current and 30°C temperature. The optical spectrum FWHM is 0.5nm and side mode suppression ratio is 27dBm with uncoated. The laser with 1mm cavity length showed the threshold current of 50mA, a lasing wavelength of λ = 852.6nm, slope efficiency of above 0.7mW/mA. We accomplished single lateral mode of ridge waveguide edge-emitting lasers which can also be used as a laser source in the ultra-narrow linewidth external cavity laser system.

Flexibility and adaptability in binding of E. coli cytidine repressor to different operators suggests a role in differential gene regulation.

PubMed

Tretyachenko-Ladokhina, Vira; Cocco, Melanie J; Senear, Donald F

2006-09-15

Interactions between DNA-bound transcription factors CytR and CRP regulate the promoters of the Escherichia coli CytR regulon. A distinctive feature of the palindromic CytR operators is highly variable length central spacers (0-9 bp). Previously we demonstrated distinct modes of CytR binding to operators that differ in spacer length. These different modes are characterized by opposite enthalpic and entropic contributions at 25 degrees C. Of particular note were radically different negative DeltaCp values suggesting variable contribution from coupled protein folding and/or DNA structural transitions. We proposed that the CytR DNA binding-domain adopts either a more rigid or flexible DNA-bound conformation in response to the different spacer lengths. More recently, similar effects were shown to contribute to discrimination between operator and non-specific DNA binding by LacR, a CytR homolog. Here we have extended the thermodynamic analysis to the remaining natural CytR operators plus a set of synthetic operators designed to isolate spacing as the single variable. The thermodynamic results show a broad and monotonic range of effects that are primarily dependent on spacer length. The magnitude of effects suggests participation by more than the DNA-binding domain. 15N HSQC NMR and CD spectral analyses were employed to characterize the structural basis for these effects. The results indicate that while CytR forms a well-ordered structure in solution, it is highly dynamic. We propose a model in which a large ensemble of native state conformations narrows upon binding, to an extent governed by operator spacing. This in turn is expected to constrain intermolecular interactions in the CytR-CRP-DNA complex, thus generating operator-specific effects on repression and induction of transcription.

Low loss depressed cladding waveguide inscribed in YAG:Nd single crystal by femtosecond laser pulses.

PubMed

Okhrimchuk, Andrey; Mezentsev, Vladimir; Shestakov, Alexander; Bennion, Ian

2012-02-13

A depressed cladding waveguide with record low loss of 0.12 dB/cm is inscribed in YAG:Nd(0.3at.%) crystal by femtosecond laser pulses with an elliptical beam waist. The waveguide is formed by a set of parallel tracks which constitute the depressed cladding. It is a key element for compact and efficient CW waveguide laser operating at 1064 nm and pumped by a multimode laser diode. Special attention is paid to mechanical stress resulting from the inscription process. Numerical calculation of mode distribution and propagation loss with the elasto-optical effect taken into account leads to the conclusion that the depressed cladding is a dominating factor in waveguide mode formation, while the mechanical stress only slightly distorts waveguide modes.

Going through a quantum phase

NASA Technical Reports Server (NTRS)

Shapiro, Jeffrey H.

1992-01-01

Phase measurements on a single-mode radiation field are examined from a system-theoretic viewpoint. Quantum estimation theory is used to establish the primacy of the Susskind-Glogower (SG) phase operator; its phase eigenkets generate the probability operator measure (POM) for maximum likelihood phase estimation. A commuting observables description for the SG-POM on a signal x apparatus state space is derived. It is analogous to the signal-band x image-band formulation for optical heterodyne detection. Because heterodyning realizes the annihilation operator POM, this analogy may help realize the SG-POM. The wave function representation associated with the SG POM is then used to prove the duality between the phase measurement and the number operator measurement, from which a number-phase uncertainty principle is obtained, via Fourier theory, without recourse to linearization. Fourier theory is also employed to establish the principle of number-ket causality, leading to a Paley-Wiener condition that must be satisfied by the phase-measurement probability density function (PDF) for a single-mode field in an arbitrary quantum state. Finally, a two-mode phase measurement is shown to afford phase-conjugate quantum communication at zero error probability with finite average photon number. Application of this construct to interferometric precision measurements is briefly discussed.

Design of Dual-Mode Local Oscillators Using CMOS Technology for Motion Detection Sensors.

PubMed

Ha, Keum-Won; Lee, Jeong-Yun; Kim, Jeong-Geun; Baek, Donghyun

2018-04-01

Recently, studies have been actively carried out to implement motion detecting sensors by applying radar techniques. Doppler radar or frequency-modulated continuous wave (FMCW) radar are mainly used, but each type has drawbacks. In Doppler radar, no signal is detected when the movement is stopped. Also, FMCW radar cannot function when the detection object is near the sensor. Therefore, by implementing a single continuous wave (CW) radar for operating in dual-mode, the disadvantages in each mode can be compensated for. In this paper, a dual mode local oscillator (LO) is proposed that makes a CW radar operate as a Doppler or FMCW radar. To make the dual-mode LO, a method that controls the division ratio of the phase locked loop (PLL) is used. To support both radar mode easily, the proposed LO is implemented by adding a frequency sweep generator (FSG) block to a fractional-N PLL. The operation mode of the LO is determined by according to whether this block is operating or not. Since most radar sensors are used in conjunction with microcontroller units (MCUs), the proposed architecture is capable of dual-mode operation by changing only the input control code. In addition, all components such as VCO, LDO, and loop filter are integrated into the chip, so complexity and interface issues can be solved when implementing radar sensors. Thus, the proposed dual-mode LO is suitable as a radar sensor.

Design of Dual-Mode Local Oscillators Using CMOS Technology for Motion Detection Sensors

PubMed Central

Lee, Jeong-Yun; Kim, Jeong-Geun

2018-01-01

Recently, studies have been actively carried out to implement motion detecting sensors by applying radar techniques. Doppler radar or frequency-modulated continuous wave (FMCW) radar are mainly used, but each type has drawbacks. In Doppler radar, no signal is detected when the movement is stopped. Also, FMCW radar cannot function when the detection object is near the sensor. Therefore, by implementing a single continuous wave (CW) radar for operating in dual-mode, the disadvantages in each mode can be compensated for. In this paper, a dual mode local oscillator (LO) is proposed that makes a CW radar operate as a Doppler or FMCW radar. To make the dual-mode LO, a method that controls the division ratio of the phase locked loop (PLL) is used. To support both radar mode easily, the proposed LO is implemented by adding a frequency sweep generator (FSG) block to a fractional-N PLL. The operation mode of the LO is determined by according to whether this block is operating or not. Since most radar sensors are used in conjunction with microcontroller units (MCUs), the proposed architecture is capable of dual-mode operation by changing only the input control code. In addition, all components such as VCO, LDO, and loop filter are integrated into the chip, so complexity and interface issues can be solved when implementing radar sensors. Thus, the proposed dual-mode LO is suitable as a radar sensor. PMID:29614777

Adaptable Single Active Loop Thermal Control System (TCS) for Future Space Missions

NASA Technical Reports Server (NTRS)

Mudawar, Issam; Lee, Seunghyun; Hasan, Mohammad

2015-01-01

This presentation will examine the development of a thermal control system (TCS) for future space missions utilizing a single active cooling loop. The system architecture enables the TCS to be reconfigured during the various mission phases to respond, not only to varying heat load, but to heat rejection temperature as well. The system will consist of an accumulator, pump, cold plates (evaporators), condenser radiator, and compressor, in addition to control, bypass and throttling valves. For cold environments, the heat will be rejected by radiation, during which the compressor will be bypassed, reducing the system to a simple pumped loop that, depending on heat load, can operate in either a single-phase liquid mode or two-phase mode. For warmer environments, the pump will be bypassed, enabling the TCS to operate as a heat pump. This presentation will focus on recent findings concerning two-phase flow regimes, pressure drop, and heat transfer coefficient trends in the cabin and avionics micro-channel heat exchangers when using the heat pump mode. Also discussed will be practical implications of using micro-channel evaporators for the heat pump.

On-chip beamsplitter operation on single photons from quasi-resonantly excited quantum dots embedded in GaAs rib waveguides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rengstl, U.; Schwartz, M.; Herzog, T.

2015-07-13

We present an on-chip beamsplitter operating on a single-photon level by means of a quasi-resonantly driven InGaAs/GaAs quantum dot. The single photons are guided by rib waveguides and split into two arms by an evanescent field coupler. Although the waveguides themselves support the fundamental TE and TM modes, the measured degree of polarization (∼90%) reveals the main excitation and propagation of the TE mode. We observe the preserved single-photon nature of a quasi-resonantly excited quantum dot by performing a cross-correlation measurement on the two output arms of the beamsplitter. Additionally, the same quantum dot is investigated under resonant excitation, wheremore » the same splitting ratio is observed. An autocorrelation measurement with an off-chip beamsplitter on a single output arm reveal the single-photon nature after evanescent coupling inside the on-chip splitter. Due to their robustness, adjustable splitting ratio, and their easy implementation, rib waveguide beamsplitters with embedded quantum dots provide a promising step towards fully integrated quantum circuits.« less

InGaAsP/InP optical waveguide switch operated by a carrier-induced change in the refractive index

NASA Astrophysics Data System (ADS)

Mikami, O.; Nakagome, H.

1985-11-01

Waveguided semiconductor optical switches operated by a carrier-induced change in the refractive-index associated with the plasma dispersion are proposed. InGaAsP/InP four-port switches having two intersecting single-mode channel waveguides are fabricated by selective liquid-phase epitaxy and investigated at 1.5 microns wavelength. Optical switching is observed as a result of mode interference in the waveguide intersection region.

All-fiber radially/azimuthally polarized lasers based on mode coupling of tapered fibers.

PubMed

Mao, Dong; He, Zhiwen; Lu, Hua; Li, Mingkun; Zhang, Wending; Cui, Xiaoqi; Jiang, Biqiang; Zhao, Jianlin

2018-04-01

We demonstrate a mode converter with an insertion loss of 0.36 dB based on mode coupling of tapered single-mode and two-mode fibers, and realize all-fiber flexible cylindrical vector lasers at 1550 nm. Attributing to the continuous distribution of a tangential electric field at taper boundaries, the laser is switchable between the radially and azimuthally polarized states by adjusting the input polarization. In the temporal domain, the operation is controllable among continuous-wave, Q-switched, and mode-locked statuses by changing the saturable absorber or pump strength. The duration of Q-switched radially/azimuthally polarized laser spans from 10.4/10.8 to 6/6.4 μs at the pump range of 38 to 58 mW, while that of the mode-locked pulse varies from 39.2/31.9 to 5.6/5.2 ps by controlling the laser bandwidth. The proposed laser combines the features of a cylindrical vector beam, a fiber laser, and an ultrafast pulse, providing a special and cost-effective source for practical applications.

H-mode achievement and edge features in RFX-mod tokamak operation

NASA Astrophysics Data System (ADS)

Spolaore, M.; Cavazzana, R.; Marrelli, L.; Carraro, L.; Franz, P.; Spagnolo, S.; Zaniol, B.; Zuin, M.; Cordaro, L.; Dal Bello, S.; De Masi, G.; Ferro, A.; Finotti, C.; Grando, L.; Grenfell, G.; Innocente, P.; Kudlacek, O.; Marchiori, G.; Martines, E.; Momo, B.; Paccagnella, R.; Piovesan, P.; Piron, C.; Puiatti, M. E.; Recchia, M.; Scarin, P.; Taliercio, C.; Vianello, N.; Zanotto, L.

2017-11-01

The RFX-mod experiment is a fusion device designed to operate as a reversed field pinch (RFP), with a major radius R = 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating it also as an ohmic tokamak, allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system providing a magnetic boundary effective control, by applying resonant or non-resonant magnetic perturbations (MP), both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool to limit the impact of plasma filaments and ELMs (edge localized modes) on plasma facing components. An important new research line is the exploitation of the RFX-mod active control system for ELM mitigation studies. As a first step in this direction, this paper presents the most recent achievements in term of RFX-mod tokamak explored scenarios, which allowed the first investigation of the ohmic and edge biasing induced H-mode. The production of D-shaped tokamak discharges and the design and deployment of an insertable polarized electrode were accomplished. Reproducible H-mode phases were obtained with insertable electrode negative biasing in single null discharges, representing an unexplored scenario with this technique. Important modifications of the edge plasma density and flow properties are observed. During the achieved H-mode ELM-like electromagnetic composite filamentary structures are observed. They are characterized by clear vorticity and parallel current density patterns.

1.9 THz Quantum-cascade Lasers with One-well Injector

NASA Technical Reports Server (NTRS)

Kumar, Sushil; Williams, Benjamin S.; Hu, Qing; Reno, John L.

2006-01-01

We report terahertz quantum-cascade lasers operating predominantly at 1.90 THz with side modes as low as 1.86 THz (lambda approx. equal to 161 micrometers, planck's constant omega approx. equal to 7.7 meV). This is the longest wavelength to date of any solid-state laser that operates without assistance of a magnetic field. Carriers are injected into the upper radiative state by using a single quantum-well injector, which resulted in a significant reduction of free-carrier losses. The laser operated up to a heat-sink temperature of 110 K in pulsed mode, 95 K in continuous wave (cw) mode, and the threshold current density at 5 K was approx. 140 A per square centimeters.

Stinger Post Hybrid Simulation: Design Description and Users’ Manual

DTIC Science & Technology

1983-04-01

function of three variables. Table 4 MVFG Modes £ ?*" Mode Function Number Argument Number Trunking Station Address Output Hole Argument...between JA and J7. This permits the signal to control a normally-open, single-throw minature relay. It closes the remote operate line when a logic...logic functions are also performed on the card. A normally- open, single-throw minature relay (U5) and an AND gate (1/4 of Ul) are used to perform the

Apparatus And Methods For Launching And Receiving A Broad Wavelength Range Source

DOEpatents

Von Drasek, William A.; Sonnenfroh, David; Allen, Mark G.; Stafford-Evans, Joy

2006-02-28

An apparatus and method for simultaneous detection of N gas species through laser radiation attenuation techniques is disclosed. Each of the N species has a spectral absorption band. N laser sources operate at a wavelength ?N in a spectral absorption band separated by the cutoff wavelength for single-mode transmission. Each laser source corresponds to a gas species and transmits radiation through an optical fiber constructed and arranged to provide single-mode transmission with minimal power loss.

Multi-species detection using multi-mode absorption spectroscopy (MUMAS)

NASA Astrophysics Data System (ADS)

Northern, J. H.; Thompson, A. W. J.; Hamilton, M. L.; Ewart, P.

2013-06-01

The detection of multiple species using a single laser and single detector employing multi-mode absorption spectroscopy (MUMAS) is reported. An in-house constructed, diode-pumped, Er:Yb:glass micro-laser operating at 1,565 nm with 10 modes separated by 18 GHz was used to record MUMAS signals in a gas mixture containing C2H2, N2O and CO. The components of the mixture were detected simultaneously by identifying multiple transitions in each of the species. By using temperature- and pressure-dependent modelled spectral fits to the data, partial pressures of each species in the mixture were determined with an uncertainty of ±2 %.

Fiber laser refractometer based on tunable bandpass filter tailored FBG reflection

NASA Astrophysics Data System (ADS)

Zhao, Junfa; Wang, Juan; Zhang, Cheng; Xu, Wei; Sun, Xiaodong; Bai, Hua; Chen, Liying

2018-02-01

A fiber laser refractometer based on single-mode-no-core-single-mode (SNS) structure cascaded with a FBG is proposed and experimentally demonstrated. The output wavelength of the fiber laser keeps constant because the oscillating wavelength is only determined by the central wavelength of the FBG which is insensitive to the surrounding refractive index (SRI). However, the output power is sensitive to the SRI because the intracavity loss of the fiber laser varies with the SRI. A cost-effective power detection refractometer with reflective operation can be realized through measuring the variation of the fiber laser's output power. The refractometer has a sensitivity of 195.52 dB/RIU and 365.52 dB/RIU in the RI range of 1.3330-1.3687 and 1.3687-1.4135, respectively. Moreover, the refractometer can also be used for temperature measurement through discriminating the output wavelength of the fiber laser.

Linear entropy and collapse–revival phenomenon for a general formalism N-type four-level atom interacting with a single-mode field

NASA Astrophysics Data System (ADS)

Eied, A. A.

2018-05-01

In this paper, the linear entropy and collapse-revival phenomenon through the relation (< {\\hat{a}}+{\\hat{a}} > -{\\bar{n}}) in a system of N-configuration four-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling functional are investigated. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent states and the atom initially in its most upper excited state. The dynamical behavior of the linear entropy and the time evolution of (< {\\hat{a}}+ {\\hat{a}} > -{\\bar{n}}) are analyzed. In particular, the effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy and the evolution of (< {\\hat{a}}+ {\\hat{a}} > -{\\bar{n}}) are examined.

Scanning ultrafast electron microscopy.

PubMed

Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

2010-08-24

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

High efficiency H6 single-phase transformerless grid-tied PV inverter with proposed modulation for reactive power generation

NASA Astrophysics Data System (ADS)

Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad

2017-08-01

Implementation of transformerless inverters in PV grid-tied system offer great benefits such as high efficiency, light weight, low cost, etc. Most of the proposed transformerless inverters in literature are verified for only real power application. Currently, international standards such as VDE-AR-N 4105 has demanded that PV grid-tied inverters should have the ability of controlling a specific amount of reactive power. Generation of reactive power cannot be accomplished in single phase transformerless inverter topologies because the existing modulation techniques are not adopted for a freewheeling path in the negative power region. This paper enhances a previous high efficiency proposed H6 trnasformerless inverter with SiC MOSFETs and demonstrates new operating modes for the generation of reactive power. A proposed pulse width modulation (PWM) technique is applied to achieve bidirectional current flow through freewheeling state. A comparison of the proposed H6 transformerless inverter using SiC MOSFETs and Si MOSFTEs is presented in terms of power losses and efficiency. The results show that reactive power control is attained without adding any additional active devices or modification to the inverter structure. Also, the proposed modulation maintains a constant common mode voltage (CM) during every operating mode and has low leakage current. The performance of the proposed system verifies its effectiveness in the next generation PV system.

Two-View versus Single-View Shear-Wave Elastography: Comparison of Observer Performance in Differentiating Benign from Malignant Breast Masses.

PubMed

Lee, Su Hyun; Cho, Nariya; Chang, Jung Min; Koo, Hye Ryoung; Kim, Jin You; Kim, Won Hwa; Bae, Min Sun; Yi, Ann; Moon, Woo Kyung

2013-10-28

Purpose To determine whether two-view shear-wave elastography (SWE) improves the performance of radiologists in differentiating benign from malignant breast masses compared with single-view SWE. Materials and Methods This prospective study was conducted with institutional review board approval, and written informed consent was obtained. B-mode ultrasonographic (US) and orthogonal SWE images were obtained for 219 breast masses (136 benign and 83 malignant; mean size, 14.8 mm) in 219 consecutive women (mean age, 47.9 years; range, 20-78 years). Five blinded radiologists independently assessed the likelihood of malignancy for three data sets: B-mode US alone, B-mode US and single-view SWE, and B-mode US and two-view SWE. Interobserver agreement regarding Breast Imaging Reporting and Data System (BI-RADS) category and the area under the receiver operating characteristic curve (AUC) of each data set were compared. Results Interobserver agreement was moderate (κ = 0.560 ± 0.015 [standard error of the mean]) for BI-RADS category assessment with B-mode US alone. When SWE was added to B-mode US, five readers showed substantial interobserver agreement (κ = 0.629 ± 0.017 for single-view SWE; κ = 0.651 ± 0.014 for two-view SWE). The mean AUC of B-mode US was 0.870 (range, 0.855-0.884). The AUC of B-mode US and two-view SWE (average, 0.928; range, 0.904-0.941) was higher than that of B-mode US and single-view SWE (average, 0.900; range, 0.890-0.920), with statistically significant differences for three readers (P ≤ .003). Conclusion The performance of radiologists in differentiating benign from malignant breast masses was improved when B-mode US was combined with two-view SWE compared with that when B-mode US was combined with single-view SWE. © RSNA, 2013 Supplemental material: S1.

Two-view versus single-view shear-wave elastography: comparison of observer performance in differentiating benign from malignant breast masses.

PubMed

Lee, Su Hyun; Cho, Nariya; Chang, Jung Min; Koo, Hye Ryoung; Kim, Jin You; Kim, Won Hwa; Bae, Min Sun; Yi, Ann; Moon, Woo Kyung

2014-02-01

To determine whether two-view shear-wave elastography (SWE) improves the performance of radiologists in differentiating benign from malignant breast masses compared with single-view SWE. This prospective study was conducted with institutional review board approval, and written informed consent was obtained. B-mode ultrasonographic (US) and orthogonal SWE images were obtained for 219 breast masses (136 benign and 83 malignant; mean size, 14.8 mm) in 219 consecutive women (mean age, 47.9 years; range, 20-78 years). Five blinded radiologists independently assessed the likelihood of malignancy for three data sets: B-mode US alone, B-mode US and single-view SWE, and B-mode US and two-view SWE. Interobserver agreement regarding Breast Imaging Reporting and Data System (BI-RADS) category and the area under the receiver operating characteristic curve (AUC) of each data set were compared. Interobserver agreement was moderate (κ = 0.560 ± 0.015 [standard error of the mean]) for BI-RADS category assessment with B-mode US alone. When SWE was added to B-mode US, five readers showed substantial interobserver agreement (κ = 0.629 ± 0.017 for single-view SWE; κ = 0.651 ± 0.014 for two-view SWE). The mean AUC of B-mode US was 0.870 (range, 0.855-0.884). The AUC of B-mode US and two-view SWE (average, 0.928; range, 0.904-0.941) was higher than that of B-mode US and single-view SWE (average, 0.900; range, 0.890-0.920), with statistically significant differences for three readers (P ≤ .003). The performance of radiologists in differentiating benign from malignant breast masses was improved when B-mode US was combined with two-view SWE compared with that when B-mode US was combined with single-view SWE. © RSNA, 2013

High power operation of cladding pumped holmium-doped silica fibre lasers.

PubMed

Hemming, Alexander; Bennetts, Shayne; Simakov, Nikita; Davidson, Alan; Haub, John; Carter, Adrian

2013-02-25

We report the highest power operation of a resonantly cladding-pumped, holmium-doped silica fibre laser. The cladding pumped all-glass fibre utilises a fluorine doped glass layer to provide low loss cladding guidance of the 1.95 µm pump radiation. The operation of both single mode and large-mode area fibre lasers was demonstrated, with up to 140 W of output power achieved. A slope efficiency of 59% versus launched pump power was demonstrated. The free running emission was measured to be 2.12-2.15 µm demonstrating the potential of this architecture to address the long wavelength operation of silica based fibre lasers with high efficiency.

Design and analysis for a bend-resistant and large-mode-area photonic crystal fiber with hybrid cladding.

PubMed

Qin, Yan; Yang, Huajun; Jiang, Ping; Gui, Fengji; Caiyang, Weinan; Cao, Biao

2018-05-10

In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at a smaller bending radius is designed. The finite-element method with a perfectly matched layer boundary is used to analyze the performance of the PCF. To achieve LMA-PCF with low bending loss, the air holes with double lattice constants and different sizes at the core are designed. Numerical results show that this structure can achieve low bending loss and LMA with a smaller bending radius at the wavelength of 1.55 μm. The effective mode area of the fundamental mode is larger than 1000  μm 2 when the bending radius is ≥10  cm. The bending loss of the fundamental mode is just 0.0113 dB/m, and the difference between the fundamental and high-order modes of the bending loss is larger than 10 3 when the bending radius is 10 cm. Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

NASA Astrophysics Data System (ADS)

Becnel, Andrew C.

This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.

Multimode and single-mode fibers for data center and high-performance computing applications

NASA Astrophysics Data System (ADS)

Bickham, Scott R.

2016-03-01

Data center (DC) and high performance computing (HPC) applications have traditionally used a combination of copper, multimode fiber and single-mode fiber interconnects with relative percentages that depend on factors such as the line rate, reach and connectivity costs. The balance between these transmission media has increasingly shifted towards optical fiber due to the reach constraints of copper at data rates of 10 Gb/s and higher. The percentage of single-mode fiber deployed in the DC has also grown slightly since 2014, coinciding with the emergence of mega DCs with extended distance needs beyond 100 m. This trend will likely continue in the next few years as DCs expand their capacity from 100G to 400G, increase the physical size of their facilities and begin to utilize silicon-photonics transceiver technology. However there is a still a need for the low-cost and high-density connectivity, and this is sustaining the deployment of multimode fiber for links <= 100 m. In this paper, we discuss options for single-mode and multimode fibers in DCs and HPCs and introduce a reduced diameter multimode fiber concept which provides intra-and inter-rack connectivity as well as compatibility with silicon-photonic transceivers operating at 1310 nm. We also discuss the trade-offs between single-mode fiber attributes such as bend-insensitivity, attenuation and mode field diameter and their roles in capacity and connectivity in data centers.

Ring laser having an output at a single frequency

DOEpatents

Hackell, Lloyd A.

1991-01-01

A ring laser is disclosed that produces a single frequency of laser radiation in either the pulsed mode of operation or the continuous waveform (cw) mode of operation. The laser comprises a ring laser in a bowtie configuration, a birefringent gain material such as Nd:YLF, an improved optical diode that supports laser oscillation having a desired direction of travel and linear polarization, and a Q-switch. An output coupler (mirror) having a high reflectivity, such as 94%, is disclosed. Also disclosed is a self-seeded method of operation in which the laser can provide a pulse or a series of pulses of high power laser radiation at a consistent single frequency with a high degree of amplitude stability and temporal stability. In operation, the laser is operated in continuous waveform (cw) at a low power output with the Q-switch introducing a loss into the resonating cavity. Pumping is continued at a high level, causing the gain material to store energy. When a pulse is desired, the Q-switch is actuated to substantially reduce the losses so that a pulse can build up based on the low level cw oscillation. The pulse quickly builds, using the stored energy in the gain medium to provide a high power output pulse. The process may be repeated to provide a series of high power pulses of a consistent single frequency.

Single-mode fiber, velocity interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krauter, K. G.; Jacobson, G. F.; Patterson, J. R.

2011-04-15

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, wemore » demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats--this interference occurs between the ''recently'' shifted and ''formerly unshifted'' paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber.« less

Single-mode fiber, velocity interferometry.

PubMed

Krauter, K G; Jacobson, G F; Patterson, J R; Nguyen, J H; Ambrose, W P

2011-04-01

In this paper, we describe a velocity interferometer system based entirely on single-mode fiber optics. This paper includes a description of principles used in developing the single-mode velocity interferometry system (SMV). The SMV design is based on polarization-insensitive components. Polarization adjusters are included to eliminate the effects of residual birefringence and polarization dependent losses in the interferometers. Characterization measurements and calibration methods needed for data analysis and a method of data analysis are described. Calibration is performed directly using tunable lasers. During development, we demonstrated its operation using exploding-foil bridge-wire fliers up to 200 m/s. In a final test, we demonstrated the SMV in a gas gun experiment up to 1.2 km/sec. As a basis for comparison in the gas gun experiment, we used another velocimetry technique that is also based on single-mode fiber optics: photonic Doppler velocimetry (PDV). For the gas gun experiment, we split the light returned from a single target spot and performed a direct comparison of the homodyne (SMV) and heterodyne (PDV) techniques concurrently. The two techniques had a negligible mean difference and a 1.5% standard deviation in the one-dimensional shock zone. Within one interferometer delay time after a sudden Doppler shift, a SMV unencumbered by multimode-fiber dispersion exhibits two color beats. These beats have the same period as PDV beats-this interference occurs between the "recently" shifted and "formerly unshifted" paths within the interferometer. We believe that recognizing this identity between homodyne and heterodyne beats is novel in the shock-physics field. SMV includes the conveniences of optical fiber, while removing the time resolution limitations associated with the multimode delivery fiber. © 2011 American Institute of Physics

Self-mode-locked AlGaInP-VECSEL

NASA Astrophysics Data System (ADS)

Bek, R.; Großmann, M.; Kahle, H.; Koch, M.; Rahimi-Iman, A.; Jetter, M.; Michler, P.

2017-10-01

We report the mode-locked operation of an AlGaInP-based semiconductor disk laser without a saturable absorber. The active region containing 20 GaInP quantum wells is used in a linear cavity with a curved outcoupling mirror. The gain chip is optically pumped by a 532 nm laser, and mode-locking is achieved by carefully adjusting the pump spot size. For a pump power of 6.8 W, an average output power of up to 30 mW is reached at a laser wavelength of 666 nm. The pulsed emission is characterized using a fast oscilloscope and a spectrum analyzer, demonstrating stable single-pulse operation at a repetition rate of 3.5 GHz. Intensity autocorrelation measurements reveal a FWHM pulse duration of 22 ps with an additional coherence peak on top, indicating noise-like pulses. The frequency spectrum, as well as the Gaussian beam profile and the measured beam propagation factor below 1.1, shows no influence of higher order transverse modes contributing to the mode-locked operation.

Mode-locking evolution in ring fiber lasers with tunable repetition rate.

PubMed

Korobko, D A; Fotiadi, A A; Zolotovskii, I O

2017-09-04

We have applied a simple approach to analyze behavior of the harmonically mode-locked fiber laser incorporating an adjustable Mach-Zehnder interferometer (MZI). Our model is able to describe key features of the laser outputs and explore limitations of physical mechanisms responsible for laser operation at different pulse repetition rates tuned over a whole GHz range. At low repetition rates the laser operates as a harmonically mode-locked soliton laser triggered by a fast saturable absorber. At high repetition rates the laser mode-locking occurs due to dissipative four-wave mixing seeded by MZI and gain spectrum filtering. However, the laser stability in this regime is rather low due to poor mode selectivity provided by MZI that is able to support the desired laser operation just near the lasing threshold. The use of a double MZI instead of a single MZI could improve the laser stability and extends the range of the laser tunability. The model predicts a gap between two repetitive rate ranges where pulse train generation is not supported.

Low-loss single-mode hollow-core fiber with anisotropic anti-resonant elements.

PubMed

Habib, Md Selim; Bang, Ole; Bache, Morten

2016-04-18

A hollow-core fiber using anisotropic anti-resonant tubes in the cladding is proposed for low loss and effectively single-mode guidance. We show that the loss performance and higher-order mode suppression is significantly improved by using symmetrically distributed anisotropic anti-resonant tubes in the cladding, elongated in the radial direction, when compared to using isotropic, i.e. circular, anti-resonant tubes. The effective single-mode guidance of the proposed fiber is achieved by enhancing the coupling between the cladding modes and higher-order-core modes by suitably engineering the anisotropic anti-resonant elements. With a silica-based fiber design aimed at 1.06 µm, we show that the loss extinction ratio between the higher-order core modes and the fundamental core mode can be more than 1000 in the range 1.0-1.65 µm, while the leakage loss of the fundamental core mode is below 15 dB/km in the same range.

"Crypto-Display" in Dual-Mode Metasurfaces by Simultaneous Control of Phase and Spectral Responses.

PubMed

Yoon, Gwanho; Lee, Dasol; Nam, Ki Tae; Rho, Junsuk

2018-06-26

Although conventional metasurfaces have demonstrated many promising functionalities in light control by tailoring either phase or spectral responses of subwavelength structures, simultaneous control of both responses has not been explored yet. Here, we propose a concept of dual-mode metasurfaces that enables simultaneous control of phase and spectral responses for two kinds of operation modes of transmission and reflection, respectively. In the transmission mode, the dual-mode metasurface acts as conventional metasurfaces by tailoring phase distribution of incident light. In the reflection mode, a reflected colored image is produced under white light illumination. We also experimentally demonstrate a crypto-display as one application of the dual-mode metasurface. The crypto-display looks a normal reflective display under white light illumination but generates a hologram that reveals the encrypted phase information under single-wavelength coherent light illumination. Because two operation modes do not affect each other, the crypto-display can have applications in security techniques.

Automatic Rejection Of Multimode Laser Pulses

NASA Technical Reports Server (NTRS)

Tratt, David M.; Menzies, Robert T.; Esproles, Carlos

1991-01-01

Characteristic modulation detected, enabling rejection of multimode signals. Monitoring circuit senses multiple longitudinal mode oscillation of transversely excited, atmospheric-pressure (TEA) CO2 laser. Facility developed for inclusion into coherent detection laser radar (LIDAR) system. However, circuit described of use in any experiment where desireable to record data only when laser operates in single longitudinal mode.

Single photon detection using Geiger mode CMOS avalanche photodiodes

NASA Astrophysics Data System (ADS)

Lawrence, William G.; Stapels, Christopher; Augustine, Frank L.; Christian, James F.

2005-10-01

Geiger mode Avalanche Photodiodes fabricated using complementary metal-oxide-semiconductor (CMOS) fabrication technology combine high sensitivity detectors with pixel-level auxiliary circuitry. Radiation Monitoring Devices has successfully implemented CMOS manufacturing techniques to develop prototype detectors with active diameters ranging from 5 to 60 microns and measured detection efficiencies of up to 60%. CMOS active quenching circuits are included in the pixel layout. The actively quenched pixels have a quenching time less than 30 ns and a maximum count rate greater than 10 MHz. The actively quenched Geiger mode avalanche photodiode (GPD) has linear response at room temperature over six orders of magnitude. When operating in Geiger mode, these GPDs act as single photon-counting detectors that produce a digital output pulse for each photon with no associated read noise. Thermoelectrically cooled detectors have less than 1 Hz dark counts. The detection efficiency, dark count rate, and after-pulsing of two different pixel designs are measured and demonstrate the differences in the device operation. Additional applications for these devices include nuclear imaging and replacement of photomultiplier tubes in dosimeters.

Time reversal of arbitrary photonic temporal modes via nonlinear optical frequency conversion

NASA Astrophysics Data System (ADS)

Raymer, Michael G.; Reddy, Dileep V.; van Enk, Steven J.; McKinstrie, Colin J.

2018-05-01

Single-photon wave packets can carry quantum information between nodes of a quantum network. An important general operation in photon-based quantum information systems is ‘blind’ reversal of a photon’s temporal wave packet envelope, that is, the ability to reverse an envelope without knowing the temporal state of the photon. We present an all-optical means for doing so, using nonlinear-optical frequency conversion driven by a short pump pulse. The process used may be sum-frequency generation or four-wave Bragg scattering. This scheme allows for quantum operations such as a temporal-mode parity sorter. We also verify that the scheme works for arbitrary states (not only single-photon ones) of an unknown wave packet.

Development of long wavelength semiconductor diode lasers near 28 microns for use in infrared heterodyne spectrometers

NASA Technical Reports Server (NTRS)

Linden, K. J.

1984-01-01

The development of tunable diode lasers operating in the 28 micrometers spectral region for use in infrared heterodyne spectrometers is reported. A process capable of yielding lasers emitting 500 micron W of multimode power, 112 micron W in a true single mode and true single mode operation at laser currents of up to 35% above threshold was developed. Results were obtained from narrow mesastripe (20 micrometer wide) short cavity (120 micrometer length) laser configurations. Six stripe geometry lasers, with a variety of cavity widths and lengths were delivered. The techniques to fabricate such devices was obtained and the long term reliability of such lasers by reproducible electrical and optical output characteristics fabrication from lasers are demonstrated.

Printing 2-dimentional droplet array for single-cell reverse transcription quantitative PCR assay with a microfluidic robot.

PubMed

Zhu, Ying; Zhang, Yun-Xia; Liu, Wen-Wen; Ma, Yan; Fang, Qun; Yao, Bo

2015-04-01

This paper describes a nanoliter droplet array-based single-cell reverse transcription quantitative PCR (RT-qPCR) assay method for quantifying gene expression in individual cells. By sequentially printing nanoliter-scale droplets on microchip using a microfluidic robot, all liquid-handling operations including cell encapsulation, lysis, reverse transcription, and quantitative PCR with real-time fluorescence detection, can be automatically achieved. The inhibition effect of cell suspension buffer on RT-PCR assay was comprehensively studied to achieve high-sensitivity gene quantification. The present system was applied in the quantitative measurement of expression level of mir-122 in single Huh-7 cells. A wide distribution of mir-122 expression in single cells from 3061 copies/cell to 79998 copies/cell was observed, showing a high level of cell heterogeneity. With the advantages of full-automation in liquid-handling, simple system structure, and flexibility in achieving multi-step operations, the present method provides a novel liquid-handling mode for single cell gene expression analysis, and has significant potentials in transcriptional identification and rare cell analysis.

Printing 2-Dimentional Droplet Array for Single-Cell Reverse Transcription Quantitative PCR Assay with a Microfluidic Robot

PubMed Central

Zhu, Ying; Zhang, Yun-Xia; Liu, Wen-Wen; Ma, Yan; Fang, Qun; Yao, Bo

2015-01-01

This paper describes a nanoliter droplet array-based single-cell reverse transcription quantitative PCR (RT-qPCR) assay method for quantifying gene expression in individual cells. By sequentially printing nanoliter-scale droplets on microchip using a microfluidic robot, all liquid-handling operations including cell encapsulation, lysis, reverse transcription, and quantitative PCR with real-time fluorescence detection, can be automatically achieved. The inhibition effect of cell suspension buffer on RT-PCR assay was comprehensively studied to achieve high-sensitivity gene quantification. The present system was applied in the quantitative measurement of expression level of mir-122 in single Huh-7 cells. A wide distribution of mir-122 expression in single cells from 3061 copies/cell to 79998 copies/cell was observed, showing a high level of cell heterogeneity. With the advantages of full-automation in liquid-handling, simple system structure, and flexibility in achieving multi-step operations, the present method provides a novel liquid-handling mode for single cell gene expression analysis, and has significant potentials in transcriptional identification and rare cell analysis. PMID:25828383

Single chip camera device having double sampling operation

NASA Technical Reports Server (NTRS)

Fossum, Eric R. (Inventor); Nixon, Robert (Inventor)

2002-01-01

A single chip camera device is formed on a single substrate including an image acquisition portion for control portion and the timing circuit formed on the substrate. The timing circuit also controls the photoreceptors in a double sampling mode in which are reset level is first read and then after an integration time a charged level is read.

Analysis of multi-mode to single-mode conversion at 635 nm and 1550 nm

NASA Astrophysics Data System (ADS)

Zamora, Vanessa; Bogatzki, Angelina; Arndt-Staufenbiel, Norbert; Hofmann, Jens; Schröder, Henning

2016-03-01

We propose two low-cost and robust optical fiber systems based on the photonic lantern (PL) technology for operating at 635 nm and 1550 nm. The PL is an emerging technology that couples light from a multi-mode (MM) fiber to several single-mode (SM) fibers via a low-loss adiabatic transition. This bundle of SM fibers is observed as a MM fiber system whose spatial modes are the degenerate supermodes of the bundle. The adiabatic transition allows that those supermodes evolve into the modes of the MM fiber. Simulations of the MM fiber end structure and its taper transition have been performed via functional mode solver tools in order to understand the modal evolution in PLs. The modelled design consists of 7 SM fibers inserted into a low-index capillary. The material and geometry of the PLs are chosen such that the supermodes match to the spatial modes of the desired step-index MM fiber in a moderate loss transmission. The dispersion of materials is also considered. These parameters are studied in two PL systems in order to reach a spectral transmission from 450 nm to 1600 nm. Additionally, an analysis of the geometry and losses due to the mismatching of modes is presented. PLs are typically used in the fields of astrophotonics and space photonics. Recently, they are demonstrated as mode converters in telecommunications, especially focusing on spatial division multiplexing. In this study, we show the use of PLs as a promising interconnecting tool for the development of miniaturized spectrometers operating in a broad wavelength range.

Electromagnetic interference and shielding: An introduction (revised version of 1991-23)

NASA Astrophysics Data System (ADS)

Dehoop, A. T.; Quak, D.

The basic equations of the electromagnetic field are summarized as far as they are needed in the theory of electromagnetic interference and shielding. Through the analysis of the planar electric current emitter, the propagation coefficient, attenuation coefficient, phase coefficient, wave-speed, wavelength, wave impedance, wave admittance, and power flow density of a wave are introduced. Next, the shielding effectiveness of a shielding plate and the shielding effectiveness of a shielding parallel-plate box are determined. In the latter, particular attention is given to the occurrence of internal resonance effects, which may degrade the shielding effectiveness. Further, a survey of some fundamental properties of a system of low frequency, multiconductor transmission lines is given. For a three conductor system with a plane of symmetry, the decomposition into the common mode and the differential mode of operation is discussed. Finally, expressions for the voltages and electric currents induced by external sources along a single transmission line are derived.

A single-frequency double-pulse Ho:YLF laser for CO2-lidar

NASA Astrophysics Data System (ADS)

Kucirek, P.; Meissner, A.; Eiselt, P.; Höfer, M.; Hoffmann, D.

2016-03-01

A single-frequency q-switched Ho:YLF laser oscillator with a bow-tie ring resonator, specifically designed for highspectral stability, is reported. It is pumped with a dedicated Tm:YLF laser at 1.9 μm. The ramp-and-fire method with a DFB-diode laser as a reference is employed for generating single-frequency emission at 2051 nm. The laser is tested with different operating modes, including cw-pumping at different pulse repetition frequencies and gain-switched pumping. The standard deviation of the emission wavelength of the laser pulses is measured with the heterodyne technique at the different operating modes. Its dependence on the single-pass gain in the crystal and on the cavity finesse is investigated. At specific operating points the spectral stability of the laser pulses is 1.5 MHz (rms over 10 s). Under gain-switched pumping with 20% duty cycle and 2 W of average pump power, stable single-frequency pulse pairs with a temporal separation of 580 μs are produced at a repetition rate of 50 Hz. The measured pulse energy is 2 mJ (<2 % rms error on the pulse energy over 10 s) and the measured pulse duration is approx. 20 ns for each of the two pulses in the burst.

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing.

PubMed

Yang, Qingbo; Wang, Hanzheng; Lan, Xinwei; Cheng, Baokai; Chen, Sisi; Shi, Honglan; Xiao, Hai; Ma, Yinfa

2015-02-01

pH sensing at the single-cell level without negatively affecting living cells is very important but still a remaining issue in the biomedical studies. A 70 μm reflection-mode fiber-optic micro-pH sensor was designed and fabricated by dip-coating thin layer of organically modified aerogel onto a tapered spherical probe head. A pH sensitive fluorescent dye 2', 7'-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF) was employed and covalently bonded within the aerogel networks. By tuning the alkoxide mixing ratio and adjusting hexamethyldisilazane (HMDS) priming procedure, the sensor can be optimized to have high stability and pH sensing ability. The in vitro real-time sensing capability was then demonstrated in a simple spectroscopic way, and showed linear measurement responses with a pH resolution up to an average of 0.049 pH unit within a narrow, but biological meaningful pH range of 6.12-7.81. Its novel characterizations of high spatial resolution, reflection mode operation, fast response and high stability, great linear response within biological meaningful pH range and high pH resolutions, make this novel pH probe a very cost-effective tool for chemical/biological sensing, especially within the single cell level research field.

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing

PubMed Central

Yang, Qingbo; Wang, Hanzheng; Lan, Xinwei; Cheng, Baokai; Chen, Sisi; Shi, Honglan; Xiao, Hai; Ma, Yinfa

2014-01-01

pH sensing at the single-cell level without negatively affecting living cells is very important but still a remaining issue in the biomedical studies. A 70 μm reflection-mode fiber-optic micro-pH sensor was designed and fabricated by dip-coating thin layer of organically modified aerogel onto a tapered spherical probe head. A pH sensitive fluorescent dye 2′, 7′-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF) was employed and covalently bonded within the aerogel networks. By tuning the alkoxide mixing ratio and adjusting hexamethyldisilazane (HMDS) priming procedure, the sensor can be optimized to have high stability and pH sensing ability. The in vitro real-time sensing capability was then demonstrated in a simple spectroscopic way, and showed linear measurement responses with a pH resolution up to an average of 0.049 pH unit within a narrow, but biological meaningful pH range of 6.12–7.81. Its novel characterizations of high spatial resolution, reflection mode operation, fast response and high stability, great linear response within biological meaningful pH range and high pH resolutions, make this novel pH probe a very cost-effective tool for chemical/biological sensing, especially within the single cell level research field. PMID:25530670

Geometric characterization of separability and entanglement in pure Gaussian states by single-mode unitary operations

NASA Astrophysics Data System (ADS)

Adesso, Gerardo; Giampaolo, Salvatore M.; Illuminati, Fabrizio

2007-10-01

We present a geometric approach to the characterization of separability and entanglement in pure Gaussian states of an arbitrary number of modes. The analysis is performed adapting to continuous variables a formalism based on single subsystem unitary transformations that has been recently introduced to characterize separability and entanglement in pure states of qubits and qutrits [S. M. Giampaolo and F. Illuminati, Phys. Rev. A 76, 042301 (2007)]. In analogy with the finite-dimensional case, we demonstrate that the 1×M bipartite entanglement of a multimode pure Gaussian state can be quantified by the minimum squared Euclidean distance between the state itself and the set of states obtained by transforming it via suitable local symplectic (unitary) operations. This minimum distance, corresponding to a , uniquely determined, extremal local operation, defines an entanglement monotone equivalent to the entropy of entanglement, and amenable to direct experimental measurement with linear optical schemes.

Selective Sensing of Gas Mixture via a Temperature Modulation Approach: New Strategy for Potentiometric Gas Sensor Obtaining Satisfactory Discriminating Features.

PubMed

Li, Fu-An; Jin, Han; Wang, Jinxia; Zou, Jie; Jian, Jiawen

2017-03-12

A new strategy to discriminate four types of hazardous gases is proposed in this research. Through modulating the operating temperature and the processing response signal with a pattern recognition algorithm, a gas sensor consisting of a single sensing electrode, i.e., ZnO/In₂O₃ composite, is designed to differentiate NO₂, NH₃, C₃H₆, CO within the level of 50-400 ppm. Results indicate that with adding 15 wt.% ZnO to In₂O₃, the sensor fabricated at 900 °C shows optimal sensing characteristics in detecting all the studied gases. Moreover, with the aid of the principle component analysis (PCA) algorithm, the sensor operating in the temperature modulation mode demonstrates acceptable discrimination features. The satisfactory discrimination features disclose the future that it is possible to differentiate gas mixture efficiently through operating a single electrode sensor at temperature modulation mode.

Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings

NASA Astrophysics Data System (ADS)

Wang, Dong-Bo; Zhang, Jin-Chuan; Cheng, Feng-Min; Zhao, Yue; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

2018-02-01

In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al2O3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.

Integrated fiber-coupled launcher for slow plasmon-polariton waves.

PubMed

Della Valle, Giuseppe; Longhi, Stefano

2012-01-30

We propose and numerically demonstrate an integrated fiber-coupled launcher for slow surface plasmon-polaritons. The device is based on a novel plasmonic mode-converter providing efficient power transfer from the fast to the slow modes of a metallic nanostripe. Total coupling efficiency with standard single-mode fiber approaching 30% (including ohmic losses) has been numerically predicted for a 25-µm long gold-based device operating at 1.55 µm telecom wavelength.

Simultaneous dual mode combustion engine operating on spark ignition and homogenous charge compression ignition

DOEpatents

Fiveland, Scott B.; Wiggers, Timothy E.

2004-06-22

An engine particularly suited to single speed operation environments, such as stationary power generators. The engine includes a plurality of combustion cylinders operable under homogenous charge compression ignition, and at least one combustion cylinder operable on spark ignition concepts. The cylinder operable on spark ignition concepts can be convertible to operate under homogenous charge compression ignition. The engine is started using the cylinders operable under spark ignition concepts.

Compact single mode tunable laser using a digital micromirror device.

PubMed

Havermeyer, Frank; Ho, Lawrence; Moser, Christophe

2011-07-18

The wavelength tuning properties of a tunable external cavity laser based on multiplexed volume holographic gratings and a commercial micromirror device are reported. The 3x3x3 cm(3) laser exhibits single mode operation in single or multi colors between 776 nm and 783 nm with less than 7.5 MHz linewidth, 37 mW output power, 50 μs rise/fall time constant and a maximum switching rate of 0.66 KHz per wavelength. The unique discrete-wavelength-switching features of this laser are also well suited as a source for continuous wave Terahertz generation and three-dimensional metrology.

Surface-plasmon distributed-feedback quantum cascade lasers operating pulsed, room temperature

NASA Astrophysics Data System (ADS)

Bousseksou, A.; Chassagneux, Y.; Coudevylle, J. R.; Colombelli, R.; Sirtori, C.; Patriarche, G.; Beaudoin, G.; Sagnes, I.

2009-08-01

We report distributed-feedback surface-plasmon quantum cascade lasers operating at λ ≈7.6μm. The distributed feedback is obtained by the sole patterning of the top metal contact on a surface plasmon waveguide. Single mode operation with more than 30dB side mode suppression ratio is obtained in pulsed mode and at room temperature. A careful experimental study confirms that by varying the grating duty cycle, one can reduce the waveguide losses with respect to standard, unpatterned surface-plasmon devices. This allows one to reduce the laser threshold current of more than a factor of 2 in the 200-300K temperature range. This approach may lead to a fabrication technology for midinfrared distributed-feedback lasers based on a very simple processing.

[The P300 based brain-computer interface: effect of stimulus position in a stimulus train].

PubMed

Ganin, I P; Shishkin, S L; Kochetova, A G; Kaplan, A Ia

2012-01-01

The P300 brain-computer interface (BCI) is currently the most efficient BCI. This interface is based on detection of the P300 wave of the brain potentials evoked when a symbol related to the intended input is highlighted. To increase operation speed of the P300 BCI, reduction of the number of stimuli repetitions is needed. This reduction leads to increase of the relative contribution to the input symbol detection from the reaction to the first target stimulus. It is known that the event-related potentials (ERP) to the first stimulus presentations can be different from the ERP to stimuli presented latter. In particular, the amplitude of responses to the first stimulus presentations is often increased, which is beneficial for their recognition by the BCI. However, this effect was not studied within the BCI framework. The current study examined the ERP obtained from healthy participants (n = 14) in the standard P300 BCI paradigm using 10 trials, as well as in the modified P300 BCI with stimuli presented on moving objects in triple-trial (n = 6) and single-trial (n = 6) stimulation modes. Increased ERP amplitude was observed in response to the first target stimuli in both conditions, as well as in the single-trial mode comparing to triple-trial. We discuss the prospects of using the specific features of the ERP to first stimuli and the single-trial ERP for optimizing the high-speed modes in the P300 BCIs.

On the possibility of observing bound soliton pairs in a wave-breaking-free mode-locked fiber laser

NASA Astrophysics Data System (ADS)

Martel, G.; Chédot, C.; Réglier, V.; Hideur, A.; Ortaç, B.; Grelu, Ph.

2007-02-01

On the basis of numerical simulations, we explain the formation of the stable bound soliton pairs that were experimentally reported in a high-power mode-locked ytterbium fiber laser [Opt. Express 14, 6075 (2006)], in a regime where wave-breaking-free operation is expected. A fully vectorial model allows one to rigorously reproduce the nonmonotonic nature for the nonlinear polarization effect that generally limits the power scalability of a single-pulse self-similar regime. Simulations show that a self-similar regime is not fully obtained, although positive linear chirps and parabolic spectra are always reported. As a consequence, nonvanishing pulse tails allow distant stable binding of highly-chirped pulses.

Microcomputer-based Peltier thermostat for precision optical radiation measurements

NASA Astrophysics Data System (ADS)

Zhu, Xiaosong; Krochmann, Eike; Chen, Jiashu

1992-03-01

We have developed a microcomputer-based thermostat for a light measuring head in precision optical radiation measurements. This thermostat consists of a single-chip microcomputer, a digital-to-analog converter, a liquid crystal display, a power operational amplifier, and a Peltier element (thermoelectric cooler). The Peltier element keeps the temperature of the photometer head at 20±0.1 °C in the ambient temperature range from -20 to 60 °C. A control algorithm which combines the ``Bang-Bang'' mode and proportional-plus-integral-plus-derivative mode is used to achieve fast and smooth thermostatic performance. This thermostat is effective, inexpensive, and easy to adjust. Several applications of the Peltier thermostat are mentioned.

Giant amplification in degenerate band edge slow-wave structures interacting with an electron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Othman, Mohamed A. K.; Veysi, Mehdi; Capolino, Filippo

2016-03-15

We propose a new amplification regime based on a synchronous operation of four degenerate electromagnetic (EM) modes in a slow-wave structure and the electron beam, referred to as super synchronization. These four EM modes arise in a Fabry-Pérot cavity when degenerate band edge (DBE) condition is satisfied. The modes interact constructively with the electron beam resulting in superior amplification. In particular, much larger gains are achieved for smaller beam currents compared to conventional structures based on synchronization with only a single EM mode. We demonstrate giant gain scaling with respect to the length of the slow-wave structure compared to conventionalmore » Pierce type single mode traveling wave tube amplifiers. We construct a coupled transmission line model for a loaded waveguide slow-wave structure exhibiting a DBE, and investigate the phenomenon of giant gain via super synchronization using the Pierce model generalized to multimode interaction.« less

Open nonradiative cavities as millimeter wave single-mode resonators

NASA Astrophysics Data System (ADS)

Annino, G.; Cassettari, M.; Martinelli, M.

2005-06-01

Open single-mode metallic cavities operating in nonradiative configurations are proposed and demonstrated. Starting from well-known dielectric resonators, possible nonradiative cavities have been established; their behavior on the fundamental TE011 mode has been predicted on the basis of general considerations. As a result, very efficient confinement properties are expected for a wide variety of open structures having rotational invariance. Test cavities realized having in mind practical millimeter wave constraints have been characterized at microwave frequencies. The obtained results confirm the expected high performances on widely open configurations. A possible excitation of the proposed resonators exploiting their nonradiative character is discussed, and the resulting overall ease of realization enlightened in view of millimeter wave employments.

Start-Up Scenario in Gyrotrons with a Nonstationary Microwave-Field Structure

NASA Astrophysics Data System (ADS)

Nusinovich, G. S.; Yeddulla, M.; Antonsen, T. M., Jr.; Vlasov, A. N.

2006-03-01

Megawatt class gyrotrons operate in very high-order modes. Therefore, control of a gyrotron oscillator’s start-up is important for excitation of the desired mode in the presence of the many undesired modes. Analysis of such scenario using the self-consistent code MAGY [M. Botton , IEEE Trans. Plasma Sci. 26,ITPSBD0093-3813 882 (1998)10.1109/27.700860] reveals that during start-up not only mode amplitudes vary in time, but also their axial structure can be time dependent. Simulations done for a 1.5 MW gyrotron show that the excitation of a single operating TE22,6 mode can exhibit a sort of intermittency when, first, it is excited as a mode whose axial structure extends outside the interaction cavity, then it ceases and then reappears as a mode mostly localized in the cavity. This phenomenon makes it necessary to analyze start-up scenarios in such gyrotrons with the use of codes that account for the possible evolution of field profiles.

On the passive probing of fiber optic quantum communication channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korol'kov, A. V., E-mail: sergei.kulik@gmail.co; Katamadze, K. G.; Kulik, S. P.

2010-04-15

Avalanche photodetectors based on InGaAs:P are the most sensitive and only detectors operating in the telecommunication wavelength range 1.30-1.55 {mu}m in the fiber optic quantum cryptography systems that can operate in the single photon count mode. In contrast to the widely used silicon photodetectors for wavelengths up to 1 {mu}m operating in a waiting mode, these detectors always operate in a gated mode. The production of an electron-hole pair in the process of the absorption of a photon and the subsequent appearance of an avalanche of carriers can be accompanied by the inverse processes of the recombination and emission ofmore » photons. Such a backward emission can present a potential serious problem for the stability of fiber optic quantum cryptography systems against passive probing. The results of analyzing the detection of backscattered radiation are reported. The probability of such an emission has been estimated.« less

Single-mode interband cascade laser multiemitter structure for two-wavelength absorption spectroscopy

NASA Astrophysics Data System (ADS)

Scheuermann, Julian; Weih, Robert; Becker, Steffen; Fischer, Marc; Koeth, Johannes; Höfling, Sven

2018-01-01

An interband cascade laser multiemitter with single-mode distributed feedback (DFB) emission at two wavelengths is presented. Continuous-wave laser operation is measured from 0°C to 40°C with threshold currents of around 25 mA and output powers of around 9 mW at 20°C. The ridge waveguide DFB structures are monolithically integrated with a spacing of 70 μm and each is provided with an individual metal DFB grating to select specific single-mode wavelengths of interest for absorption spectroscopy. The emission windows at 3.92 and 4.01 μm are targeting hydrogen sulfide and sulfur dioxide, which are of importance for industrial applications since both gases are reagents of the Claus process in sulfur recovery units, recovering elemental sulfur from gaseous hydrogen sulfide.

An Orbital Angular Momentum (OAM) Mode Reconfigurable Antenna for Channel Capacity Improvement and Digital Data Encoding.

PubMed

Liu, Baiyang; Lin, Guoying; Cui, Yuehui; Li, RongLin

2017-08-29

For purpose of utilizing orbital angular momentum (OAM) mode diversity, multiple OAM beams should be generated preferably by a single antenna. In this paper, an OAM mode reconfigurable antenna is proposed. Different from the existed OAM antennas with multiple ports for multiple OAM modes transmitting, the proposed antenna with only a single port, but it can be used to transmit mode 1 or mode -1 OAM beams arbitrary by controlling the PIN diodes on the feeding network through a programmable microcontroller which control by a remote controller. Simulation and measurement results such as return loss, near-field and far-field radiation patterns of two operating states for mode 1 and mode -1, and OAM mode orthogonality are given. The proposed antenna can serve as a candidate for utilizing OAM diversity, namely phase diversity to increase channel capacity at 2.4 GHz. Moreover, an OAM-mode based encoding method is experimentally carried out by the proposed OAM mode reconfigurable antenna, the digital data are encoded and decoded by different OAM modes. At the transmitter, the proposed OAM mode reconfigurable antenna is used to encode the digital data, data symbol 0 and 1 are mapped to OAM mode 1 and mode -1, respectively. At the receiver, the data symbols are decoded by phase gradient method.

Algebra of Majorana doubling.

PubMed

Lee, Jaehoon; Wilczek, Frank

2013-11-27

Motivated by the problem of identifying Majorana mode operators at junctions, we analyze a basic algebraic structure leading to a doubled spectrum. For general (nonlinear) interactions the emergent mode creation operator is highly nonlinear in the original effective mode operators, and therefore also in the underlying electron creation and destruction operators. This phenomenon could open up new possibilities for controlled dynamical manipulation of the modes. We briefly compare and contrast related issues in the Pfaffian quantum Hall state.

Preventing Raman Lasing in High-Q WGM Resonators

NASA Technical Reports Server (NTRS)

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute

2007-01-01

A generic design has been conceived to suppress the Raman effect in whispering- gallery-mode (WGM) optical resonators that have high values of the resonance quality factor (Q). Although it is possible to exploit the Raman effect (even striving to maximize the Raman gain to obtain Raman lasing), the present innovation is intended to satisfy a need that arises in applications in which the Raman effect inhibits the realization of the full potential of WGM resonators as frequency-selection components. Heretofore, in such applications, it has been necessary to operate high-Q WGM resonators at unattractively low power levels to prevent Raman lasing. (The Raman-lasing thresholds of WGM optical resonators are very low and are approximately proportional to Q(sup -2)). Heretofore, two ways of preventing Raman lasting at high power levels have been known, but both entail significant disadvantages: A resonator can be designed so that the optical field is spread over a relatively large mode volume to bring the power density below the threshold. For any given combination of Q and power level, there is certain mode volume wherein Raman lasing does not start. Unfortunately, a resonator that has a large mode volume also has a high spectral density, which is undesirable in a typical photonic application. A resonator can be cooled to the temperature of liquid helium, where the Raman spectrum is narrower and, therefore, the Raman gain is lower. However, liquid-helium cooling is inconvenient. The present design overcomes these disadvantages, making it possible to operate a low-spectral-density (even a single-mode) WGM resonator at a relatively high power level at room temperature, without risk of Raman lasing.

Power blue and green laser diodes and their applications

NASA Astrophysics Data System (ADS)

Hager, Thomas; Strauß, Uwe; Eichler, Christoph; Vierheilig, Clemens; Tautz, Sönke; Brüderl, Georg; Stojetz, Bernhard; Wurm, Teresa; Avramescu, Adrian; Somers, André; Ristic, Jelena; Gerhard, Sven; Lell, Alfred; Morgott, Stefan; Mehl, Oliver

2013-03-01

InGaN based green laser diodes with output powers up to 50mW are now well established for variety of applications ranging from leveling to special lighting effects and mobile projection of 12lm brightness. In future the highest market potential for visible single mode profile lasers might be laser projection of 20lm. Therefore direct green single-mode laser diodes with higher power are required. We found that self heating was the limiting factor for higher current operation. We present power-current characteristics of improved R and D samples with up to 200mW in cw-operation. An optical output power of 100mW is reached at 215mA, a current level which is suitable for long term operation. Blue InGaN laser diodes are also the ideal source for phosphor based generation of green light sources of high luminance. We present a light engine based on LARP (Laser Activated Remote Phosphor) which can be used in business projectors of several thousand lumens on screen. We discuss the advantages of a laser based systems in comparison with LED light engines. LARP requires highly efficient blue power laser diodes with output power above 1W. Future market penetration of LARP will require lower costs. Therefore we studied new designs for higher powers levels. R and D chips with power-current characteristics up to 4W in continuous wave operation on C-mount at 25°C are presented.

A single-cell scraper based on an atomic force microscope for detaching a living cell from a substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwata, Futoshi, E-mail: iwata.futoshi@shizuoka.ac.jp; Research Institute of Electronics, Shizuoka University, Johoku, Naka-ku, Hamamatsu 432-8011; Adachi, Makoto

We describe an atomic force microscope (AFM) manipulator that can detach a single, living adhesion cell from its substrate without compromising the cell's viability. The micrometer-scale cell scraper designed for this purpose was fabricated from an AFM micro cantilever using focused ion beam milling. The homemade AFM equipped with the scraper was compact and standalone and could be mounted on a sample stage of an inverted optical microscope. It was possible to move the scraper using selectable modes of operation, either a manual mode with a haptic device or a computer-controlled mode. The viability of the scraped single cells wasmore » evaluated using a fluorescence dye of calcein-acetoxymethl ester. Single cells detached from the substrate were collected by aspiration into a micropipette capillary glass using an electro-osmotic pump. As a demonstration, single HeLa cells were selectively detached from the substrate and collected by the micropipette. It was possible to recultivate HeLa cells from the single cells collected using the system.« less

An SMS (single mode - multi mode - single mode) fiber structure for vibration sensing

NASA Astrophysics Data System (ADS)

Waluyo, T. B.; Bayuwati, D.

2017-04-01

We describe an SMS (single mode - multi mode - single mode) fiber structure to be used in a vibration sensing system. The fiber structure was fabricated by splicing a section (about 300 mm in length) of a step index multi mode fiber between two single mode fibers obtained from a communication grade fiber patchcord. Interference between higher order modes occurs while light from a narrow band light source travels along the multi mode fiber. When the multi mode fiber vibrates, the refractive index profile is changed because of the photo-elastics effect and the amplitude of the interference pattern is changed accordingly. To simulate a vibrating structure we used a loudspeaker to vibrate a wooden table. By using a digital oscilloscope, we recorded and analysed the vibrating signals obtained from the SMS fiber structure as well as from a GS-32CT geophone for referencing. We observed that this SMS fiber structure was potential to be used in a vibration sensing system with a measurement range from 30 to 180 Hz with inherent optical fiber sensor advantages such as light weight, immune to electromagnetic interference, and no electricity in the sensing part.

High performance, low dissipation quantum cascade lasers across the mid-IR range.

PubMed

Bismuto, Alfredo; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Muller, Antoine

2015-03-09

In this work, we present the development of low consumption quantum cascade lasers across the mid-IR range. In particular, short cavity single-mode lasers with optimised facet reflectivities have been fabricated from 4.5 to 9.2 μm. Threshold dissipated powers as low as 0.5 W were obtained in continuous wave operation at room temperature. In addition, the beneficial impact of reducing chip length on laser mounting yield is discussed. High power single-mode lasers from the same processed wafers are also presented.

Diagnostics and control of wavenumber stability and purity of tunable diode lasers relevant to their use as local oscillators in heterodyne systems

NASA Technical Reports Server (NTRS)

Poultney, S.; Chen, D.; Steinberg, G.; Wu, F.; Pires, A.; Miller, M. D.; Mcnally, M.

1980-01-01

Initial operation of the tunable diode lasers (TDL) showed that it was not possible to adjust the wavenumber to one selected a priori in the TDL tuning range. During operation, the operating point would change by 0.1/cm over the longer term with even larger changes occurring during some thermal cycles. Most changes during thermal cycling required using lower temperatures and higher currents to reach the former wavenumber (when it could be reached). In many cases, an operating point could be selected by changing TDL current and temperature to give both the desired wavenumber and most of the power in a single mode. The selection procedure had to be used after each thermal cycling. Wavenumber nonlinearities of about 10% over a 0.5 cm tuning range were observed. Diagnostics of the single mode selected by a grating monochromator showed wavenumber fine structure under certain operating conditions. The characteristics due to the TDL environment included short term wavenumber stability, the instrument lineshape function, and intermediate term wavenumber stability.

Parameter space for the collective laser coupling in the laser fusion driver based on the concept of fiber amplification network.

PubMed

Huang, Zhihua; Lin, Honghuan; Xu, Dangpeng; Li, Mingzhong; Wang, Jianjun; Deng, Ying; Zhang, Rui; Zhang, Yongliang; Tian, Xiaocheng; Wei, Xiaofeng

2013-07-15

Collective laser coupling of the fiber array in the inertial confinement fusion (ICF) laser driver based on the concept of fiber amplification network (FAN) is researched. The feasible parameter space is given for laser coupling of the fundamental, second and third harmonic waves by neglecting the influence of the frequency conversion on the beam quality under the assumption of beam quality factor conservation. Third harmonic laser coupling is preferred due to its lower output energy requirement from a single fiber amplifier. For coplanar fiber array, the energy requirement is around 0.4 J with an effective mode field diameter of around 500 μm while maintaining the fundamental mode operation which is more than one order of magnitude higher than what can be achieved with state-of-the-art technology. Novel waveguide structure needs to be developed to enlarge the fundamental mode size while mitigating the catastrophic self-focusing effect.

Open-cavity fiber laser with distributed feedback based on externally or self-induced dynamic gratings.

PubMed

Lobach, Ivan A; Drobyshev, Roman V; Fotiadi, Andrei A; Podivilov, Evgeniy V; Kablukov, Sergey I; Babin, Sergey A

2017-10-15

Dynamic population inversion gratings induced in an active medium by counter-propagating optical fields may have a reverse effect on writing laser radiation via feedback they provide. In this Letter we report, to the best of our knowledge, on the first demonstration of an open-cavity fiber laser in which the distributed feedback is provided by a dynamic grating "written" in a Yb-doped active fiber, either by an external source or self-induced via a weak (∼0.1%) reflection from an angle-cleaved fiber end. It has been shown that meters-long dynamic grating is formed with a narrow bandwidth (<50  MHz) and a relatively high-reflection coefficient (>7%) securing single-frequency operation, but the subsequent hole-burning effects accompanied by new grating formation lead to the switching from one longitudinal mode to another. providing a regular pulse-mode dynamics. As a result, periodically generated pulse trains cover a spectrum range of several terahertz delivering millions of cavity modes in sequent pulses.

A phase space approach to wave propagation with dispersion.

PubMed

Ben-Benjamin, Jonathan S; Cohen, Leon; Loughlin, Patrick J

2015-08-01

A phase space approximation method for linear dispersive wave propagation with arbitrary initial conditions is developed. The results expand on a previous approximation in terms of the Wigner distribution of a single mode. In contrast to this previously considered single-mode case, the approximation presented here is for the full wave and is obtained by a different approach. This solution requires one to obtain (i) the initial modal functions from the given initial wave, and (ii) the initial cross-Wigner distribution between different modal functions. The full wave is the sum of modal functions. The approximation is obtained for general linear wave equations by transforming the equations to phase space, and then solving in the new domain. It is shown that each modal function of the wave satisfies a Schrödinger-type equation where the equivalent "Hamiltonian" operator is the dispersion relation corresponding to the mode and where the wavenumber is replaced by the wavenumber operator. Application to the beam equation is considered to illustrate the approach.

Multipartite entanglement in fermionic systems via a geometric measure

NASA Astrophysics Data System (ADS)

Lari, Behzad; Durganandini, P.; Joag, Pramod S.

2010-12-01

We study multipartite entanglement in a system consisting of indistinguishable fermions. Specifically, we have proposed a geometric entanglement measure for N spin-(1)/(2) fermions distributed over 2L modes (single-particle states). The measure is defined on the 2L qubit space isomorphic to the Fock space for 2L single-particle states. This entanglement measure is defined for a given partition of 2L modes containing m⩾2 subsets. Thus this measure applies to m⩽2L partite fermionic systems where L is any finite number, giving the number of sites. The Hilbert spaces associated with these subsets may have different dimensions. Further, we have defined the local quantum operations with respect to a given partition of modes. This definition is generic and unifies different ways of dividing a fermionic system into subsystems. We have shown, using a representative case, that the geometric measure is invariant under local unitary operators corresponding to a given partition. We explicitly demonstrate the use of the measure to calculate multipartite entanglement in some correlated electron systems.

Synchronizable Q-switched, mode-locked, and cavity-dumped ruby laser for plasma diagnostics

NASA Astrophysics Data System (ADS)

Houtman, H.; Meyer, J.

1985-06-01

We report on the design and operation of an optimized version of a Q-switched, mode-locked, and cavity-dumped ruby-laser oscillator. The modulator window is much narrower than that assumed in conventional active mode-lock theory, and is shown to yield much shorter pulses than the latter in cases where the number of round trips is restricted. To allow a high-power pulse (≊1 GW) to evolve in the oscillator, and to allow simple synchronization to a (˜100 ns fixed delay) CO2 laser, a limit of 23 round trips was chosen, but similar limits may be imposed by lasers having short-gain duration as in an excimer laser. Details are given on the single spark gap switching element and Pockels cells, with an analysis of their expected switching speeds, in order to establish the effectiveness of the modulator, as compared to conventional sinusoidally driven active mode lockers. Single pulses of 50-70 mJ are reliably cavity-dumped after only 100-ns delay (23 round trips) with pulse length adjustable from 50-100 ps with ±5-ps stability. Relative timing between the main (CO2) and probe (ruby) pulses allows a measurement accuracy of ±50 ps to be attained.

Synchronizable Q-switched, mode-locked, and cavity-dumped ruby laser for plasma diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Houtman, H.; Meyer, J.

We report on the design and operation of an optimized version of a Q-switched, mode-locked, and cavity-dumped ruby-laser oscillator. The modulator window is much narrower than that assumed in conventional active mode-lock theory, and is shown to yield much shorter pulses than the latter in cases where the number of round trips is restricted. To allow a high-power pulse (roughly-equal1 GW) to evolve in the oscillator, and to allow simple synchronization to a (approx.100 ns fixed delay) CO/sub 2/ laser, a limit of 23 round trips was chosen, but similar limits may be imposed by lasers having short-gain duration asmore » in an excimer laser. Details are given on the single spark gap switching element and Pockels cells, with an analysis of their expected switching speeds, in order to establish the effectiveness of the modulator, as compared to conventional sinusoidally driven active mode lockers. Single pulses of 50--70 mJ are reliably cavity-dumped after only 100-ns delay (23 round trips) with pulse length adjustable from 50--100 ps with +- 5-ps stability. Relative timing between the main (CO/sub 2/) and probe (ruby) pulses allows a measurement accuracy of +- 50 ps to be attained.« less

On-chip photonic transistor based on the spike synchronization in circuit QED

NASA Astrophysics Data System (ADS)

Gül, Yusuf

2018-03-01

We consider the single photon transistor in coupled cavity system of resonators interacting with multilevel superconducting artificial atom simultaneously. Effective single mode transformation is used for the diagonalization of the Hamiltonian and impedance matching in terms of the normal modes. Storage and transmission of the incident field are described by the interactions between the cavities controlling the atomic transitions of lowest lying states. Rabi splitting of vacuum-induced multiphoton transitions is considered in input/output relations by the quadrature operators in the absence of the input field. Second-order coherence functions are employed to investigate the photon blockade and delocalization-localization transitions of cavity fields. Spontaneous virtual photon conversion into real photons is investigated in localized and oscillating regimes. Reflection and transmission of cavity output fields are investigated in the presence of the multilevel transitions. Accumulation and firing of the reflected and transmitted fields are used to investigate the synchronization of the bunching spike train of transmitted field and population imbalance of cavity fields. In the presence of single photon gate field, gain enhancement is explained for transmitted regime.

Overview of EAST experiments on the development of high-performance steady-state scenario

NASA Astrophysics Data System (ADS)

Wan, B. N.; Liang, Y. F.; Gong, X. Z.; Li, J. G.; Xiang, N.; Xu, G. S.; Sun, Y. W.; Wang, L.; Qian, J. P.; Liu, H. Q.; Zhang, X. D.; Hu, L. Q.; Hu, J. S.; Liu, F. K.; Hu, C. D.; Zhao, Y. P.; Zeng, L.; Wang, M.; Xu, H. D.; Luo, G. N.; Garofalo, A. M.; Ekedahl, A.; Zhang, L.; Zhang, X. J.; Huang, J.; Ding, B. J.; Zang, Q.; Li, M. H.; Ding, F.; Ding, S. Y.; Lyu, B.; Yu, Y. W.; Zhang, T.; Zhang, Y.; Li, G. Q.; Xia, T. Y.; the EAST Team; Collaborators

2017-10-01

The EAST research program aims to demonstrate steady-state long-pulse advanced high-performance H-mode operations with ITER-like poloidal configuration and RF-dominated heating schemes. Since the 2014 IAEA FEC, EAST has been upgraded with all ITER-relevant auxiliary heating and current drive systems, enabling the investigation of plasma profile control by the coupling/integration of various auxiliary heating combinations. Fully non-inductive steady-state H-mode plasma (H 98,y2  >  1.1) was extended over 60 s for the first time with sole RF heating plus good power coupling and impurity and particle control. By means of the 4.6 GHz and 2.45 GHz LHCD systems, H-mode can be obtained and maintained at relatively high density, even up to n e ~ 4.5  ×  1019 m-3, where a current drive effect is still observed. Significant progress has been achieved on EAST, including: (i) demonstration of a steady-state scenario (fully non-inductive with V loop ~ 0.0 V at high β P ~ 1.8 and high-performance in upper single-null (ɛ ~ 1.6) configuration with the tungsten divertor; (ii) discovery of a stationary H-mode regime with no/small ELM using 4.6 GHz LHCD, and; (iii) achievement of ELM suppression in slowly rotating H-mode plasma with n  =  1 and 2 RMP compatible with long-pulse operations. The new advances in scenario development provide an integrated solution in achieving long-pulse steady-state operations on EAST.

Compact piezoelectric micromotor with a single bulk lead zirconate titanate stator

NASA Astrophysics Data System (ADS)

Yan, Liang; Lan, Hua; Jiao, Zongxia; Chen, Chin-Yin; Chen, I.-Ming

2013-04-01

The advance of micro/nanotechnology promotes the development of micromotors in recent years. In this article, a compact piezoelectric ultrasonic micromotor with a single bulk lead zirconate titanate stator is proposed. A traveling wave is generated by superposition of bending modes with 90° phase difference excited by d15 inverse piezoelectric effects. The operating principle simplifies the system structure significantly, and provides a miniaturization solution. A research prototype with the size of 0.75× 0.75×1.55 mm is developed. It can produce start-up torque of 0.27μNmand maximum speed of 2760 r/min at 14RMS.

Terahertz plasmonic laser radiating in an ultra-narrow beam

DOE PAGES

Wu, Chongzhao; Khanal, Sudeep; Reno, John L.; ...

2016-07-07

Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) thatmore » is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity irrespective of its operating wavelength and could bring plasmonic lasers closer to practical applications.« less

Evaluating the Effect of Minimizing Screws on Stabilization of Symphysis Mandibular Fracture by 3D Finite Element Analysis.

PubMed

Kharmanda, Ghias; Kharma, Mohamed-Yaser

2017-06-01

The objective of this work is to integrate structural optimization and reliability concepts into mini-plate fixation strategy used in symphysis mandibular fractures. The structural reliability levels are next estimated when considering a single failure mode and multiple failure modes. A 3-dimensional finite element model is developed in order to evaluate the ability of reducing the negative effect due to the stabilization of the fracture. Topology optimization process is considered in the conceptual design stage to predict possible fixation layouts. In the detailed design stage, suitable mini-plates are selected taking into account the resulting topology and different anatomical considerations. Several muscle forces are considered in order to obtain realistic predictions. Since some muscles can be cut or harmed during the surgery and cannot operate at its maximum capacity, there is a strong motivation to introduce the loading uncertainties in order to obtain reliable designs. The structural reliability is carried out for a single failure mode and multiple failure modes. The different results are validated with a clinical case of a male patient with symphysis fracture. In this case while use of the upper plate fixation with four holes, only two screws were applied to protect adjacent vital structure. This behavior does not affect the stability of the fracture. The proposed strategy to optimize bone plates leads to fewer complications and second surgeries, less patient discomfort, and shorter time of healing.

10th order laterally coupled GaN-based DFB laser diodes with V-shaped surface gratings

NASA Astrophysics Data System (ADS)

Kang, J. H.; Wenzel, H.; Hoffmann, V.; Freier, E.; Sulmoni, L.; Unger, R.-S.; Einfeldt, S.; Wernicke, T.; Kneissl, M.

2018-02-01

Single longitudinal mode operation of laterally coupled distributed feedback (DFB) laser diodes (LDs) based on GaN containing 10th-order surface Bragg gratings with V-shaped grooves is demonstrated using i-line stepper lithography and inductively coupled plasma etching. A threshold current of 82 mA, a slope efficiency of 1.7 W/A, a single peak emission at 404.5 nm with a full width at half maximum of 0.04 nm and a side mode suppression ratio of > 23 dB at an output power of about 46 mW were achieved under pulsed operation. The shift of the lasing wavelength of DFB LDs with temperature was around three times smaller than that of conventional ridge waveguide LDs.

A square-plate piezoelectric linear motor operating in two orthogonal and isomorphic face-diagonal-bending modes.

PubMed

Ci, Penghong; Chen, Zhijiang; Liu, Guoxi; Dong, Shuxiang

2014-01-01

We report a piezoelectric linear motor made of a single Pb(Zr,Ti)O3 square-plate, which operates in two orthogonal and isomorphic face-diagonal-bending modes to produce precision linear motion. A 15 × 15 × 2 mm prototype was fabricated, and the motor generated a driving force of up to 1.8 N and a speed of 170 mm/s under an applied voltage of 100 Vpp at the resonance frequency of 136.5 kHz. The motor shows such advantages as large driving force under relatively low driving voltage, simple structure, and stable motion because of its isomorphic face-diagonal-bending mode.

ToF-SIMS Depth Profiling Of Insulating Samples, Interlaced Mode Or Non-interlaced Mode?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhaoying; Jin, Ke; Zhang, Yanwen

2014-11-01

Dual beam depth profiling strategy has been widely adopted in ToF-SIMS depth profiling, in which two basic operation modes, interlaced mode and non-interlaced mode, are commonly used. Generally, interlaced mode is recommended for conductive or semi-conductive samples, whereas non-interlaced mode is recommended for insulating samples, where charge compensation can be an issue. Recent publications, however, show that the interlaced mode can be used effectively for glass depth profiling, despite the fact that glass is an insulator. In this study, we provide a simple guide for choosing between interlaced mode and non-interlaced mode for insulator depth profiling. Two representative cases aremore » presented: (1) depth profiling of a leached glass sample, and (2) depth profiling of a single crystal MgO sample. In brief, the interlaced mode should be attempted first, because (1) it may provide reasonable-quality data, and (2) it is time-saving for most cases, and (3) it introduces low H/C/O background. If data quality is the top priority and measurement time is flexible, non-interlaced mode is recommended because interlaced mode may suffer from low signal intensity and poor mass resolution. A big challenge is tracking trace H/C/O in a highly insulating sample (e.g., MgO), because non-interlaced mode may introduce strong H/C/O background but interlaced mode may suffer from low signal intensity. Meanwhile, a C or Au coating is found to be very effective to improve the signal intensity. Surprisingly, the best analyzing location is not on the C or Au coating, but at the edge (outside) of the coating.« less

A reconfigurable frequency-selective surface for dual-mode multi-band filtering applications

NASA Astrophysics Data System (ADS)

Majidzadeh, Maryam; Ghobadi, Changiz; Nourinia, Javad

2017-03-01

A reconfigurable single-layer frequency-selective surface (FSS) with dual-mode multi-band modes of operation is presented. The proposed structure is printed on a compact 10 × 10 mm2 FR4 substrate with the thickness of 1.6 mm. A simple square loop is printed on the front side while another one along with two defected vertical arms is deployed on the backside. To realise the reconfiguration, two pin diodes are embedded on the backside square loop. Suitable insertion of conductive elements along with pin diodes yields in dual-mode multi-band rejection of applicable in service frequency ranges. The first operating mode due to diodes' 'ON' state provides rejection of 2.4 GHz WLAN in 2-3 GHz, 5.2/5.8 GHz WLAN and X band in 5-12 GHz, and a part of Ku band in 13.9-16 GHz. In diodes 'OFF' state, the FSS blocks WLAN in 4-7.3 GHz, X band in 8-12.7 GHz as well as part of Ku band in 13.7-16.7 GHz. As well, high attenuation of incident waves is observed by a high shielding effectiveness (SE) in the blocked frequency bands. Also, a stable behaviour against different polarisations and angles of incidence is obtained. Comprehensive studies are conducted on a fabricated prototype to assess its performance from which encouraging results are obtained.

A femtosecond Yb-doped fiber laser with generalized vector vortex beams output (Conference Presentation)

NASA Astrophysics Data System (ADS)

Huo, Tiancheng; Qi, Li; Zhang, Buyun; Chen, Zhongping

2017-03-01

Light carries both spin and orbital angular momentum (OAM) and the superpositions of these two dynamical properties have found many applications. Many techniques exist to create such light sources but none allow their creation at the femtosecond fiber laser. Here we report on a novel mode-locked Ytterbium-doped fiber laser that generates femtosecond pulses with generalized vector vortex states. The controlled generation of such pulses such as azimuthally and radially polarized light with definite orbital angular momentum modes are demonstrated. A unidirectional ring cavity constructed with the Yb-doped fiber placed at the end of the fiber section to reduces unnecessary nonlinear effects is employed for self-starting operation. Pairs of diffraction gratings are used for compensating the normal group velocity dispersion of the fiber and other elements. Mode-locked operation is achieved based on nonlinear polarization evolution, which is mainly implemented with the single mode fiber, the bulk wave plates and the variable spiral plates (q-plate with topological charge q=0.5). The conversion from spin angular momentum to the OAM and reverse inside the laser cavity are realized by means of a quarter-wave plate and a q-plate so that the polarization control was mapped to OAM mode control. The fiber laser is diode pumped by a wavelength-division multiplexing coupler, which leads to excellent stability and portability.

“Synthesis-on” and “synthesis-off” modes of carbon arc operation during synthesis of carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yatom, Shurik; Selinsky, Rachel S.; Koel, Bruce E.

Arc discharge synthesis of single-walled carbon nanotubes (SWCNTs) remains largely uncontrollable, due to incomplete understanding of the synthetic process itself. Here, we show that synthesis of SWCNTs by a carbon arc may not constitute a single continuous process, but may instead consist of two distinct modes. One of these, a “synthesis-on” mode, produces the majority of the nanomaterials. During the synthesis-on mode, proportionally more carbon nanotubes are collected than in another mode, a “synthesis-off” mode. Both synthesis-on and synthesis-off modes for a typical arc configuration, employing a hollow anode filled with a mixture of powdered metal catalyst and graphite, weremore » characterized by using in situ electrical, imaging, and spectroscopic diagnostics, along with ex situ imaging and spectroscopy. The synthesis-on mode duration is rare compared to the total arc run-time, helping to explain the poor selectivity found in the final collected products, a known inadequacy of arc synthesis. Finally, the rarity of the synthesis on mode occurence may be due to the synthesis off mode being more favorable energetically.« less

“Synthesis-on” and “synthesis-off” modes of carbon arc operation during synthesis of carbon nanotubes

DOE PAGES

Yatom, Shurik; Selinsky, Rachel S.; Koel, Bruce E.; ...

2017-09-09

Arc discharge synthesis of single-walled carbon nanotubes (SWCNTs) remains largely uncontrollable, due to incomplete understanding of the synthetic process itself. Here, we show that synthesis of SWCNTs by a carbon arc may not constitute a single continuous process, but may instead consist of two distinct modes. One of these, a “synthesis-on” mode, produces the majority of the nanomaterials. During the synthesis-on mode, proportionally more carbon nanotubes are collected than in another mode, a “synthesis-off” mode. Both synthesis-on and synthesis-off modes for a typical arc configuration, employing a hollow anode filled with a mixture of powdered metal catalyst and graphite, weremore » characterized by using in situ electrical, imaging, and spectroscopic diagnostics, along with ex situ imaging and spectroscopy. The synthesis-on mode duration is rare compared to the total arc run-time, helping to explain the poor selectivity found in the final collected products, a known inadequacy of arc synthesis. Finally, the rarity of the synthesis on mode occurence may be due to the synthesis off mode being more favorable energetically.« less

Rapid turn-around mapping of wildfires and disasters with airborne infrared imagery fro the new FireMapper® 2.0 and Oilmapper systems

Treesearch

James W. Hoffman; Lloyd L. Coulter; Philip J Riggan

2005-01-01

The new FireMapper® 2.0 and OilMapper airborne, infrared imaging systems operate in a "snapshot" mode. Both systems feature the real time display of single image frames, in any selected spectral band, on a daylight readable tablet PC. These single frames are displayed to the operator with full temperature calibration in color or grayscale renditions. A rapid...

Transition of lasing modes in polymeric opal photonic crystal resonating cavity.

PubMed

Shi, Lan-Ting; Zheng, Mei-Ling; Jin, Feng; Dong, Xian-Zi; Chen, Wei-Qiang; Zhao, Zhen-Sheng; Duan, Xuan-Ming

2016-06-10

We demonstrate the transition of lasing modes in the resonating cavity constructed by polystyrene opal photonic crystals and 7 wt. % tert-butyl Rhodamine B doped polymer film. Both single mode and multiple mode lasing emission are observed from the resonating cavity. The lasing threshold is determined to be 0.81  μJ/pulse for single mode lasing emission and 2.25  μJ/pulse for multiple mode lasing emission. The single mode lasing emission is attributed to photonic lasing resulting from the photonic bandgap effect of the opal photonic crystals, while the multiple mode lasing emission is assigned to random lasing due to the defects in the photonic crystals. The result would benefit the development of low threshold polymeric solid state photonic crystal lasers.

Versatile tunable current-mode universal biquadratic filter using MO-DVCCs and MOSFET-based electronic resistors.

PubMed

Chen, Hua-Pin

2014-01-01

This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design.

Versatile Tunable Current-Mode Universal Biquadratic Filter Using MO-DVCCs and MOSFET-Based Electronic Resistors

PubMed Central

2014-01-01

This paper presents a versatile tunable current-mode universal biquadratic filter with four-input and three-output employing only two multioutput differential voltage current conveyors (MO-DVCCs), two grounded capacitors, and a well-known method for replacement of three grounded resistors by MOSFET-based electronic resistors. The proposed configuration exhibits high-output impedance which is important for easy cascading in the current-mode operations. The proposed circuit can be used as either a two-input three-output circuit or a three-input single-output circuit. In the operation of two-input three-output circuit, the bandpass, highpass, and bandreject filtering responses can be realized simultaneously while the allpass filtering response can be easily obtained by connecting appropriated output current directly without using additional stages. In the operation of three-input single-output circuit, all five generic filtering functions can be easily realized by selecting different three-input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no inverting-type input current signals are imposed. All the passive and active sensitivities are low. Postlayout simulations were carried out to verify the functionality of the design. PMID:24982963

Experimental study on combustion modes and thrust performance of a staged-combustor of the scramjet with dual-strut

NASA Astrophysics Data System (ADS)

Yang, Qingchun; Chetehouna, Khaled; Gascoin, Nicolas; Bao, Wen

2016-05-01

To enable the scramjet operate in a wider flight Mach number, a staged-combustor with dual-strut is introduced to hold more heat release at low flight Mach conditions. The behavior of mode transition was examined using a direct-connect model scramjet experiment along with pressure measurements. The typical operating modes of the staged-combustor are analyzed. Fuel injection scheme has a significant effect on the combustor operating modes, particularly for the supersonic combustion mode. Thrust performances of the combustor with different combustion modes and fuel distributions are reported in this paper. The first-staged strut injection has a better engine performance in the operation of subsonic combustion mode. On the contrast, the second-staged strut injection has a better engine performance in the operation of supersonic combustion mode.

Load variation effects on the pressure fluctuations exerted on a Kaplan turbine runner

NASA Astrophysics Data System (ADS)

Amiri, K.; Mulu, B.; Raisee, M.; Cervantes, M. J.

2014-03-01

Introduction of intermittent electricity production systems like wind power and solar systems to electricity market together with the consumption-based electricity production resulted in numerous start/stops, load variations and off-design operation of water turbines. The hydropower systems suffer from the varying loads exerted on the stationary and rotating parts of the turbines during load variations which they are not designed for. On the other hand, investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of rotating vortex rope (RVR) in the draft tube. The RVR induces oscillating flow both in plunging and rotating modes which results in oscillating force with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. The purpose of this study is to investigate the effect of transient operations on the pressure fluctuations on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors. The model was run in off-cam mode during different load variation conditions to check the runner performance under unsteady condition. The results showed that the transients between the best efficiency point and the high load happens in a smooth way while transitions to/from the part load, where rotating vortex rope (RVR) forms in the draft tube induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode of the RVR.

Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings.

PubMed

Wang, Dong-Bo; Zhang, Jin-Chuan; Cheng, Feng-Min; Zhao, Yue; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

2018-02-02

In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at ~ 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al 2 O 3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.

Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

DOEpatents

Petrini, Richard R.; Van Lue, Dorin F.

1983-01-01

A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment (12) with a probe coil (11), and associated coaxial coil cable (13), coil energizing means (21), and circuit means (21, 12) responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube 17 of fiberoptic scope 10. The scope 10 is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means (19, 20) for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

DOEpatents

Petrini, R.R.; Van Lue, D.F.

1983-10-25

A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, coil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signaling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level. 5 figs.

Effect of crosstalk on QBER in QKD in urban telecommunication fiber lines

NASA Astrophysics Data System (ADS)

Kurochkin, Vladimir L.; Kurochkin, Yuriy V.; Miller, Alexander V.; Sokolov, Alexander S.; Kanapin, Alan A.

2016-12-01

Quantum key distribution (QKD) as a technology is being actively implemented into existing urban telecommunication networks. QKD devices are commercially available products. While sending single photons through optical fiber, adjacent fibers, which are used to transfer classical information, might influence the amount of registrations of single photon detectors. This influence is registered, since it directly introduces a higher quantum bit error rate (QBER) into the final key [1-3]. Our report presents the results of the first tests of the QKD device, developed in the Russian Quantum Center. These tests were conducted in Moscow, and are the first of such a device in Russia in urban optical fiber telecommunication networks. The device in question is based on a two-pass auto-compensating optical scheme, which provides stable single photon transfer through urban optical fiber telecommunication networks [4,5]. The single photon detectors ID230 by ID Quantique were used. They operate in free-running mode, and with a quantum effectiveness of 10 % have a dark count 10 Hz. The background signal level in the dedicated fiber was no less than 5.6•10-14 W, which corresponds to 4.4•104 detector clicks per second. The single mode fiber length in Moscow was 30.6 km, the total attenuation equal to 11.7 dB. The sifted quantum key bit rate reached values of 1.9 kbit/s with the QBER level equal to 5.1 %. Methods of lowering the influence of crosstalk on the QBER are considered.

Lattice dynamics of A Sb2O6 (A =Cu , Co) with trirutile structure

NASA Astrophysics Data System (ADS)

Maimone, D. T.; Christian, A. B.; Neumeier, J. J.; Granado, E.

2018-03-01

Raman spectroscopy experiments on single crystals of CuSb2O6 and CoSb2O6 quasi-one-dimensional antiferromagnets with trirutile crystal structure were performed, with a focus on the first material. The observed Raman-active phonon modes and previously reported infrared-active modes were identified with the aid of ab initio lattice dynamics calculations. The structural transition between monoclinic β -CuSb2O6 and tetragonal α -CuSb2O6 phases at Ts=400 K is manifested in our spectra by a "repulsion" of two accidentally quasidegenerate symmetric modes below Ts, caused by a phonon mixing effect that is only operative in the monoclinic β -CuSb2O6 phase due to symmetry restrictions. Also, two specific phonons, associated with CuO6 octahedra rotation and with a Jahn-Teller elongation mode, soften and broaden appreciably as T →Ts . A crossover from a displacive to an order-disorder transition at Ts is inferred.

Pulse intensity characterization of the LCLS nanosecond double-bunch mode of operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yanwen; Decker, Franz-Josef; Turner, James

The recent demonstration of the 'nanosecond double-bunch' operation mode,i.e.two X-ray pulses separated in time between 0.35 and hundreds of nanoseconds and by increments of 0.35 ns, offers new opportunities to investigate ultrafast dynamics in diverse systems of interest. However, in order to reach its full potential, this mode of operation requires the precise characterization of the intensity of each X-ray pulse within each pulse pair for any time separation. Here, a transmissive single-shot diagnostic that achieves this goal for time separations larger than 0.7 ns with a precision better than 5% is presented. Lastly, it also provides real-time monitoring feedbackmore » to help tune the accelerator parameters to deliver double pulse intensity distributions optimized for specific experimental goals.« less

Pulse intensity characterization of the LCLS nanosecond double-bunch mode of operation

DOE PAGES

Sun, Yanwen; Decker, Franz-Josef; Turner, James; ...

2018-03-27

The recent demonstration of the 'nanosecond double-bunch' operation mode,i.e.two X-ray pulses separated in time between 0.35 and hundreds of nanoseconds and by increments of 0.35 ns, offers new opportunities to investigate ultrafast dynamics in diverse systems of interest. However, in order to reach its full potential, this mode of operation requires the precise characterization of the intensity of each X-ray pulse within each pulse pair for any time separation. Here, a transmissive single-shot diagnostic that achieves this goal for time separations larger than 0.7 ns with a precision better than 5% is presented. Lastly, it also provides real-time monitoring feedbackmore » to help tune the accelerator parameters to deliver double pulse intensity distributions optimized for specific experimental goals.« less

Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

DOEpatents

Hohimer, John P.

1994-01-01

A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission beam of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure.

Semiconductor diode laser having an intracavity spatial phase controller for beam control and switching

DOEpatents

Hohimer, J.P.

1994-06-07

A high-power broad-area semiconductor laser having a intracavity spatial phase controller is disclosed. The integrated intracavity spatial phase controller is easily formed by patterning an electrical contact metallization layer when fabricating the semiconductor laser. This spatial phase controller changes the normally broad far-field emission beam of such a laser into a single-lobed near-diffraction-limited beam at pulsed output powers of over 400 mW. Two operating modes, a thermal and a gain operating mode, exist for the phase controller, allowing for steering and switching the beam as the modes of operation are switched, and the emission beam may be scanned, for example, over a range of 1.4 degrees or switched by 8 degrees. More than one spatial phase controller may be integrated into the laser structure. 6 figs.

Controlled quantum secure communication protocol with single photons in both polarization and spatial-mode degrees of freedom

NASA Astrophysics Data System (ADS)

Wang, Lili; Ma, Wenping

2016-02-01

In this paper, we propose a new controlled quantum secure direct communication (CQSDC) protocol with single photons in both polarization and spatial-mode degrees of freedom. Based on the defined local collective unitary operations, the sender’s secret messages can be transmitted directly to the receiver through encoding secret messages on the particles. Only with the help of the third side, the receiver can reconstruct the secret messages. Each single photon in two degrees of freedom can carry two bits of information, so the cost of our protocol is less than others using entangled qubits. Moreover, the security of our QSDC network protocol is discussed comprehensively. It is shown that our new CQSDC protocol cannot only defend the outsider eavesdroppers’ several sorts of attacks but also the inside attacks. Besides, our protocol is feasible since the preparation and the measurement of single photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques.

Diffraction-limited, 300-kW peak-power pulses from a coiled multimode fiber amplifier

NASA Astrophysics Data System (ADS)

di Teodoro, Fabio; Koplow, Jeffrey P.; Moore, Sean W.; Kliner, Dahv A. V.

2002-04-01

We report a multimode, double-clad, Yb-doped fiber amplifier that produces diffraction-limited, 0.8-ns pulses with energies of 255 μJ and peak powers in excess of 300 kW at a repetition rate of ~8 kHz. Single-transverse-mode operation was obtained by bend-loss-induced mode filtering of the gain fiber.

Few-mode fiber based distributed curvature sensor through quasi-single-mode Brillouin frequency shift.

PubMed

Wu, Hao; Wang, Ruoxu; Liu, Deming; Fu, Songnian; Zhao, Can; Wei, Huifeng; Tong, Weijun; Shum, Perry Ping; Tang, Ming

2016-04-01

We proposed and demonstrated a few-mode fiber (FMF) based optical-fiber sensor for distributed curvature measurement through quasi-single-mode Brillouin frequency shift (BFS). By central-alignment splicing FMF and single-mode fiber (SMF) with a fusion taper, a SMF-components-compatible distributed curvature sensor based on FMF is realized using the conventional Brillouin optical time-domain analysis system. The distributed BFS change induced by bending in FMF has been theoretically and experimentally investigated. The precise BFS response to the curvature along the fiber link has been calibrated. A proof-of-concept experiment is implemented to validate its effectiveness in distributed curvature measurement.

49.6 Gb/s direct detection DMT transmission over 40 km single mode fibre using an electrically packaged silicon photonic modulator.

PubMed

Lacava, C; Cardea, I; Demirtzioglou, I; Khoja, A E; Ke, Li; Thomson, D J; Ruan, X; Zhang, F; Reed, G T; Richardson, D J; Petropoulos, P

2017-11-27

We present the characterization of a silicon Mach-Zehnder modulator with electrical packaging and show that it exhibits a large third-order intermodulation spurious-free dynamic range (> 100 dB Hz 2/3 ). This characteristic renders the modulator particularly suitable for the generation of high spectral efficiency discrete multi-tone signals and we experimentally demonstrate a single-channel, direct detection transmission system operating at 49.6 Gb/s, exhibiting a baseband spectral efficiency of 5 b/s/Hz. Successful transmission is demonstrated over various lengths of single mode fibre up to 40 km, without the need of any amplification or dispersion compensation.

Subsonic flight test evaluation of a performance seeking control algorithm on an F-15 airplane

NASA Technical Reports Server (NTRS)

Gilyard, Glenn B.; Orme, John S.

1992-01-01

The subsonic flight test evaluation phase of the NASA F-15 (powered by F 100 engines) performance seeking control program was completed for single-engine operation at part- and military-power settings. The subsonic performance seeking control algorithm optimizes the quasi-steady-state performance of the propulsion system for three modes of operation. The minimum fuel flow mode minimizes fuel consumption. The minimum thrust mode maximizes thrust at military power. Decreases in thrust-specific fuel consumption of 1 to 2 percent were measured in the minimum fuel flow mode; these fuel savings are significant, especially for supersonic cruise aircraft. Decreases of up to approximately 100 degree R in fan turbine inlet temperature were measured in the minimum temperature mode. Temperature reductions of this magnitude would more than double turbine life if inlet temperature was the only life factor. Measured thrust increases of up to approximately 15 percent in the maximum thrust mode cause substantial increases in aircraft acceleration. The system dynamics of the closed-loop algorithm operation were good. The subsonic flight phase has validated the performance seeking control technology, which can significantly benefit the next generation of fighter and transport aircraft.

Optimization of passively mode-locked quasi-continuously diode-pumped Nd:GdVO4 laser in bounce geometry

NASA Astrophysics Data System (ADS)

Frank, Milan; Jelínek, Michal; Kubeček, Václav

2015-01-01

In this paper the operation of pulsed diode-pumped Nd:GdVO4 laser oscillator in bounce geometry passively modelocked using semiconductor saturable absorber mirror (SAM), generating microjoule level picosecond pulses at wavelength of 1063 nm, is reported. Optimization of the output coupling for generation either Q-switched mode locked pulse trains or cavity dumped single pulses with maximum energy was performed, which resulted in extraction of single pulses as short as 10 ps and energy of 20 uJ. In comparison with the previous results obtained with this Nd:GdVO4 oscillator and saturable absorber in transmission mode, the achieved pulse duration is five times shorter. Using different absorbers and parameters of single pulse extraction enables generation of the pulses with duration up to 100 ps with the energy in the range from 10 to 20 μJ.

MW peak power Er/Yb-doped fiber femtosecond laser amplifier at 1.5 µm center wavelength

NASA Astrophysics Data System (ADS)

Han, Seongheum; Jang, Heesuk; Kim, Seungman; Kim, Young-Jin; Kim, Seung-Woo

2017-08-01

An erbium (Er)/ytterbium (Yb) co-doped double-clad fiber is configured to amplify single-mode pulses with a high average power of 10 W at a 1.5 µm center wavelength. The pulse duration at the exit of the Er/Yb fiber amplifier is measured to be ~440 fs after grating-based compression. The whole single-mode operation of the amplifier system permits the M 2-value of the output beam quality to be evaluated better than 1.05. By tuning the repetition rate from 100 MHz down to 600 kHz, the pulse peak power is scaled up to 19.1 MW to be the highest ever reported using an Er/Yb single-mode fiber. The proposed amplifier system is well suited for strong-power applications such as free-space LIDAR, non-thermal machining and medical surgery.

Low-Loss Coupling of Quantum Cascade Lasers into Hollow-Core Waveguides with Single-Mode Output in the 3.7-7.6 μm Spectral Range.

PubMed

Patimisco, Pietro; Sampaolo, Angelo; Mihai, Laura; Giglio, Marilena; Kriesel, Jason; Sporea, Dan; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

2016-04-13

We demonstrated low-loss and single-mode laser beam delivery through hollow-core waveguides (HCWs) operating in the 3.7-7.6 μm spectral range. The employed HCWs have a circular cross section with a bore diameter of 200 μm and metallic/dielectric internal coatings deposited inside a glass capillary tube. The internal coatings have been produced to enhance the spectral response of the HCWs in the range 3.5-12 µm. We demonstrated Gaussian-like outputs throughout the 4.5-7.6 µm spectral range. A quasi single-mode output beam with only small beam distortions was achieved when the wavelength was reduced to 3.7 μm. With a 15-cm-long HCW and optimized coupling conditions, we measured coupling efficiencies of >88% and transmission losses of <1 dB in the investigated infrared spectral range.

Guidelines on ergonomic aspects of control rooms

NASA Technical Reports Server (NTRS)

Mitchell, C. M.; Bocast, A. K.; Stewart, L. J.

1983-01-01

The anthropometry, workstation design, and environmental design of control rooms are outlined. The automated interface and VDTs and displays and various modes of communication between the system and the human operator using VDTs are discussed. The man in the loop is examined, the single controller single task framework and multiple controller multiple tasks issues are considered.

Single-Arm Double-Mode Double-Order Planar Waveguide Interferometric Sensor

NASA Technical Reports Server (NTRS)

Sarkisov, Sergey S.

2000-01-01

We have met the goals stated in section one for the project. We have demonstrated the feasibility of a single-arm double-mode double-order waveguide interferometer as a cost efficient alternative to an optical chemical sensor. Experimental prototype was built as a dye-doped polymer waveguide with propagating modes of orders <<0>> and <<1>> of the same TM polarization. The prototype demonstrated sensitivity to ammonia of the order of 200 ppm per one full oscillation of the signal. Sensor based on polyimide doped with BCP can operate at elevated temperature up to 150 C. Upon the future funding, we are planning to optimize the light source, material and the design in order to achieve sensitivity of the order of 1 ppm per full oscillations.

Diffusion-cooled high-power single-mode waveguide CO2 laser for transmyocardial revascularization

NASA Astrophysics Data System (ADS)

Berishvili, I. I.; Bockeria, L. A.; Egorov, E. N.; Golubev, Vladimir S.; Galushkin, Michail G.; Kheliminsky, A. A.; Panchenko, Vladislav Y.; Roshin, A. P.; Sigaev, I. Y.; Vachromeeva, M. N.; Vasiltsov, Victor V.; Yoshina, V. I.; Zabelin, Alexandre M.; Zelenov, Evgenii V.

1999-01-01

The paper presents the results on investigations and development of multichannel waveguide CO2 laser with diffusion cooling of active medium excited by discharge of audio-frequency alternating current. The description of high-power single-mode CO2 laser with average beam power up to 1 kW is presented. The result of measurement of the laser basic parameters are offered, as well as the outcomes of performances of the laser head with long active zone, operating in waveguide mode. As an example of application of these laser, various capabilities a description of the developed medical system 'Genom' used in the transmyocardial laser revascularization (TMLR) procedure and clinical results of the possibilities of the TMLR in the surgical treatment are presented.

The effect of realistic heavy particle induced secondary electron emission coefficients on the electron power absorption dynamics in single- and dual-frequency capacitively coupled plasmas

NASA Astrophysics Data System (ADS)

Daksha, M.; Derzsi, A.; Wilczek, S.; Trieschmann, J.; Mussenbrock, T.; Awakowicz, P.; Donkó, Z.; Schulze, J.

2017-08-01

In particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations of capacitively coupled plasmas (CCPs), the plasma-surface interaction is generally described by a simple model in which a constant secondary electron emission coefficient (SEEC) is assumed for ions bombarding the electrodes. In most PIC/MCC studies of CCPs, this coefficient is set to γ = 0.1, independent of the energy of the incident particle, the electrode material, and the surface conditions. Here, the effects of implementing energy-dependent secondary electron yields for ions, fast neutrals, and taking surface conditions into account in PIC/MCC simulations is investigated. Simulations are performed using self-consistently calculated effective SEECs, {γ }* , for ‘clean’ (e.g., heavily sputtered) and ‘dirty’ (e.g., oxidized) metal surfaces in single- and dual-frequency discharges in argon and the results are compared to those obtained by assuming a constant secondary electron yield of γ =0.1 for ions. In single-frequency (13.56 MHz) discharges operated under conditions of low heavy particle energies at the electrodes, the pressure and voltage at which the transition between the α- and γ-mode electron power absorption occurs are found to strongly depend on the surface conditions. For ‘dirty’ surfaces, the discharge operates in α-mode for all conditions investigated due to a low effective SEEC. In classical dual-frequency (1.937 MHz + 27.12 MHz) discharges {γ }* significantly increases with increasing low-frequency voltage amplitude, {V}{LF}, for dirty surfaces. This is due to the effect of {V}{LF} on the heavy particle energies at the electrodes, which negatively influences the quality of the separate control of ion properties at the electrodes. The new results on the separate control of ion properties in such discharges indicate significant differences compared to previous results obtained with different constant values of γ.

Mega-Amp Opening Switch with Nested Electrodes/Pulsed Generator of Ion and Ion Cluster Beams

DTIC Science & Technology

1987-07-30

The use of a plasma focus as a mega-amp opening switch has been demonstrated by two modes of operation: (a) Single shot mode; (b) Repetitive Mode...energy level and under the same voltage and filling-pressure conditions but without field distortion elements. Misfirings of the plasma focus machine...are also virtually eliminated by using FDE at the coaxial electrode breech. The tests (based on about 10000 shots and five plasma focus machines

All-fiber, single-frequency, and single-mode Er3+:Yb3+ fiber amplifier at 1556  nm core-pumped at 1018  nm.

PubMed

Varona, Omar de; Steinke, Michael; Neumann, Jörg; Kracht, Dietmar

2018-06-01

Emerging applications, such as gravitational wave astronomy, demand single-frequency lasers with diffraction-limited emission at 1.5 μm. Fiber amplifiers have greatly evolved to fulfill these requirements. Hundreds of watts are feasible using large-mode-area and specialty fibers. However, their application in a few watts to tens of watts in monolithic systems is unnecessarily complex due to the poor commercial availability of fiber components and standard integration procedures. In this Letter we propose and experimentally demonstrate a novel and simple method to amplify single-frequency signals at 1.5 μm up to tens of watts by core-pumping single-mode Er 3+ :Yb 3+ fiber amplifiers at 1018 nm. The proof-of-principle system is tested with different active fibers, lengths, and seed power levels. Over 11 W with an efficiency of more than 48% versus launched power is achieved. Additionally, performance degradation during operation was observed for which photodarkening due to P1 defects might be an explanation.

Single Null Negative Triangularity Tokamak for Power Handling

NASA Astrophysics Data System (ADS)

Kikuchi, Mitsuru; Medvedev, S.; Takizuka, T.; Sauter, O.; Merle, A.; Coda, S.; Chen, D.; Li, J. X.

2017-10-01

Power and particle control in fusion reactor is challenge and we proposed the negative triangularity tokamak (NTT) to eliminate ELM by operating L-mode edge with improved core confinement. The SN configuration has more flexibility in shaping by adopting rectangular-shaped TF coils. The limiting normalized beta is 3.56 with wall stabilization and 3.14 without wall. The vertical stability is assured under a reasonable control system. The wetted area on the divertor plates becomes wider in proportion to the larger major radius at the divertor strike points due to the NT configuration. In addition to the major-radius effect, the ``Flux Tune Expansion (FTE)'' is adopted to further reduce the heat load on the divertor plate by factor of 2.6 with a coil current 3 MA. L-mode edge also allows further increase in wetted area. The fusion power of 3 GW is deliverable only at normalized beta 2.1. Therefore this reactor may be operable stably against the serious MHD activities. The CD power for SS operation is 175 MW at Q = 17. AC operation is also possible option. A required HH factor is relatively modest H = 1.12.

Task Analytic Models to Guide Analysis and Design: Use of the Operator Function Model to Represent Pilot-Autoflight System Mode Problems

NASA Technical Reports Server (NTRS)

Degani, Asaf; Mitchell, Christine M.; Chappell, Alan R.; Shafto, Mike (Technical Monitor)

1995-01-01

Task-analytic models structure essential information about operator interaction with complex systems, in this case pilot interaction with the autoflight system. Such models serve two purposes: (1) they allow researchers and practitioners to understand pilots' actions; and (2) they provide a compact, computational representation needed to design 'intelligent' aids, e.g., displays, assistants, and training systems. This paper demonstrates the use of the operator function model to trace the process of mode engagements while a pilot is controlling an aircraft via the, autoflight system. The operator function model is a normative and nondeterministic model of how a well-trained, well-motivated operator manages multiple concurrent activities for effective real-time control. For each function, the model links the pilot's actions with the required information. Using the operator function model, this paper describes several mode engagement scenarios. These scenarios were observed and documented during a field study that focused on mode engagements and mode transitions during normal line operations. Data including time, ATC clearances, altitude, system states, and active modes and sub-modes, engagement of modes, were recorded during sixty-six flights. Using these data, seven prototypical mode engagement scenarios were extracted. One scenario details the decision of the crew to disengage a fully automatic mode in favor of a semi-automatic mode, and the consequences of this action. Another describes a mode error involving updating aircraft speed following the engagement of a speed submode. Other scenarios detail mode confusion at various phases of the flight. This analysis uses the operator function model to identify three aspects of mode engagement: (1) the progress of pilot-aircraft-autoflight system interaction; (2) control/display information required to perform mode management activities; and (3) the potential cause(s) of mode confusion. The goal of this paper is twofold: (1) to demonstrate the use of the operator functio model methodology to describe pilot-system interaction while engaging modes And monitoring the system, and (2) to initiate a discussion of how task-analytic models might inform design processes. While the operator function model is only one type of task-analytic representation, the hypothesis of this paper is that some type of task analytic structure is a prerequisite for the design of effective human-automation interaction.

Ion Beam Characterization of a NEXT Multi-Thruster Array Plume

NASA Technical Reports Server (NTRS)

Pencil, Eric J.; Foster, John E.; Patterson, Michael J.; Diaz, Esther M.; Van Noord, Jonathan L.; McEwen, Heather K.

2006-01-01

Three operational, engineering model, 7-kW ion thrusters and one instrumented, dormant thruster were installed in a cluster array in a large vacuum facility at NASA Glenn Research Center. A series of engineering demonstration tests were performed to evaluate the system performance impacts of operating various multiple-thruster configurations in an array. A suite of diagnostics was installed to investigate multiple-thruster operation impact on thruster performance and life, thermal interactions, and alternative system modes and architectures. The ion beam characterization included measuring ion current density profiles and ion energy distribution with Faraday probes and retarding potential analyzers, respectively. This report focuses on the ion beam characterization during single thruster operation, multiple thruster operation, various neutralizer configurations, and thruster gimbal articulation. Comparison of beam profiles collected during single and multiple thruster operation demonstrated the utility of superimposing single engine beam profiles to predict multi-thruster beam profiles. High energy ions were detected in the region 45 off the thruster axis, independent of thruster power, number of operating thrusters, and facility background pressure, which indicated that the most probable ion energy was not effected by multiple-thruster operation. There were no significant changes to the beam profiles collected during alternate thruster-neutralizer configurations, therefore supporting the viability of alternative system configuration options. Articulation of one thruster shifted its beam profile, whereas the beam profile of a stationary thruster nearby did not change, indicating there were no beam interactions which was consistent with the behavior of a collisionless beam expansion.

High-resolution investigation of longitudinal modes of a GaN-based blue laser diode

NASA Astrophysics Data System (ADS)

Al-Basheer, Watheq; Aljalal, Abdulaziz; Gasmi, Khaled; Adigun, Taofeek O.

2017-05-01

Typical emission spectra of GaN-based blue laser diodes are known to have irregular shapes. Hence, well-resolved study of their spectra may help in understanding the origin of their spectral shapes irregularity. In this paper, the spectra of a commercial GaN-based blue laser diode are studied as a function of injection current and temperature using a spectrometer with highresolution of 0.003-nm over the spectral region 440 - 450 nm. The obtained laser spectra are used to track the longitudinal modes evolution as a function of operating currents and temperatures as well as to precisely map single mode operation. In addition, yielded laser spectra will be utilized to evaluate few parameters related to the laser diode, such as mode spacing, optical gain, slope efficiency and threshold current at certain temperature.

Advances in tunable diode laser technology

NASA Technical Reports Server (NTRS)

Lo, W.

1980-01-01

The improvement of long-term reliability, the purification of mode properties, and the achievement of higher-temperature operation were examined. In reliability studies a slow increase in contact resistance during room temperature storage for lasers fabricated with In-Au or In-Pt contacts was observed. This increase is actually caused by the diffusion of In into the surface layer of laser crystals. By using a three layered structure of In-Au-Pt or In-Pt-Au, this mode of degradation was reduced. In characterizing the mode properties, it was found that the lasers emit in a highly localized, filamentary manner. For widestripe lasers the emission occurs near the corners of the junction. In order to achieve single-mode operation, stripe widths on the order of 8-10 micrometers are needed. Also, it was found that room temperature electroluminescence is possible near 4.6 micrometers.

High-power diode-pumped solid-state lasers for optical space communications

NASA Technical Reports Server (NTRS)

Koechner, Walter; Burnham, Ralph; Kasinski, Jeff; Bournes, Pat; Dibiase, Don; Le, Khoa; Marshall, Larry; Hays, Alan

1991-01-01

The design and performance of a large diode-pumped multi-stage Nd:YAG laser system for space and airborne applications will be described. The laser operates at a repetition rate of 40 Hz and produces an output either at 1.064 micron or 532 nm with an average power in the Q-switched mode of 30 W at the fundamental and 20 W at the second harmonic wavelength. The output beam is diffraction limited (TEM 00 mode) and can optionally also be operated in a single longitudinal mode. The output energy ranges from 1.25 Joule/pulse in the free lasing mode, 0.75 Joule in a 17 nsec Q-switched pulse, to 0.5 Joules/pulse at 532 nm. The overall electrical efficiency for the Q-switched second harmonic output is 4.

Majorana modes in solid state systems and its dynamics

NASA Astrophysics Data System (ADS)

Zhang, Qi; Wu, Biao

2018-04-01

We review the properties of Majorana fermions in particle physics and point out that Majorana modes in solid state systems are significantly different. The key reason is the concept of anti-particle in solid state systems is different from its counterpart in particle physics. We define Majorana modes as the eigenstates of Majorana operators and find that they can exist both at edges and in the bulk. According to our definition, only one single Majorana mode can exist in a system no matter at edges or in the bulk. Kitaev's spinless p-wave superconductor is used to illustrate our results and the dynamical behavior of the Majorana modes.

Mode switching in a multi-wavelength distributed feedback quantum cascade laser using an external micro-cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sidler, Meinrad; Institute for Quantum Electronics, ETH Zurich, Wolfgang-Pauli-Strasse 16, 8093 Zurich; Rauter, Patrick

2014-02-03

We demonstrate a multi-wavelength distributed feedback (DFB) quantum cascade laser (QCL) operating in a lensless external micro-cavity and achieve switchable single-mode emission at three distinct wavelengths selected by the DFB grating, each with a side-mode suppression ratio larger than 30 dB. Discrete wavelength tuning is achieved by modulating the feedback experienced by each mode of the multi-wavelength DFB QCL, resulting from a variation of the external cavity length. This method also provides a post-fabrication control of the lasing modes to correct for fabrication inhomogeneities, in particular, related to the cleaved facets position.

Apparatus and method for fusion of compute and switching functions of exascale system into a single component by using configurable network-on-chip fabric with distributed dual mode input-output ports and programmable network interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khare, Surhud; Somasekhar, Dinesh; More, Ankit

Described is an apparatus which comprises: a Network-On-Chip fabric using crossbar switches, having distributed ingress and egress ports; and a dual-mode network interface coupled to at least one crossbar switch, the dual-mode network interface is to include: a dual-mode circuitry; a controller operable to: configure the dual-mode circuitry to transmit and receive differential signals via the egress and ingress ports, respectively, and configure the dual-mode circuitry to transmit and receive signal-ended signals via the egress and ingress ports, respectively.

Aerosols emitted in underground mine air by diesel engine fueled with biodiesel.

PubMed

Bugarski, Aleksandar D; Cauda, Emanuele G; Janisko, Samuel J; Hummer, Jon A; Patts, Larry D

2010-02-01

Using biodiesel in place of petroleum diesel is considered by several underground metal and nonmetal mine operators to be a viable strategy for reducing the exposure of miners to diesel particulate matter. This study was conducted in an underground experimental mine to evaluate the effects of soy methyl ester biodiesel on the concentrations and size distributions of diesel aerosols and nitric oxides in mine air. The objective was to compare the effects of neat and blended biodiesel fuels with those of ultralow sulfur petroleum diesel. The evaluation was performed using a mechanically controlled, naturally aspirated diesel engine equipped with a muffler and a diesel oxidation catalyst. The effects of biodiesel fuels on size distributions and number and total aerosol mass concentrations were found to be strongly dependent on engine operating conditions. When fueled with biodiesel fuels, the engine contributed less to elemental carbon concentrations for all engine operating modes and exhaust configurations. The substantial increases in number concentrations and fraction of organic carbon (OC) in total carbon over the baseline were observed when the engine was fueled with biodiesel fuels and operated at light-load operating conditions. Size distributions for all test conditions were found to be single modal and strongly affected by engine operating conditions, fuel type, and exhaust configuration. The peak and total number concentrations as well as median diameter decreased with an increase in the fraction of biodiesel in the fuels, particularly for high-load operating conditions. The effects of the diesel oxidation catalyst, commonly deployed to counteract the potential increase in OC emissions due to use of biodiesel, were found to vary depending upon fuel formulation and engine operating conditions. The catalyst was relatively effective in reducing aerosol number and mass concentrations, particularly at light-load conditions, but also showed the potential for an increase in nitrogen dioxide concentrations at high-load modes.

Yb-doped large mode area tapered fiber with depressed cladding and dopant confinement

NASA Astrophysics Data System (ADS)

Roy, V.; Paré, C.; Labranche, B.; Laperle, P.; Desbiens, L.; Boivin, M.; Taillon, Y.

2017-02-01

A polarization-maintaining Yb-doped large mode area fiber with depressed-index inner cladding layer and confinement of rare-earth dopants has been drawn as a long tapered fiber. The larger end features a core/clad diameter of 56/400 μm and core NA 0.07, thus leading to an effective mode area over 1000 μm2. The fiber was tested up to 100 W average power, with near diffraction-limited output as the beam quality M2 was measured < 1.2. As effective single-mode guidance is enforced in the first section due to enhanced bending loss, subsequent adiabatic transition of the mode field in the taper section preserves single-mode amplification towards the larger end of the fiber.

On functional determinants of matrix differential operators with multiple zero modes

NASA Astrophysics Data System (ADS)

Falco, G. M.; Fedorenko, Andrei A.; Gruzberg, Ilya A.

2017-12-01

We generalize the method of computing functional determinants with a single excluded zero eigenvalue developed by McKane and Tarlie to differential operators with multiple zero eigenvalues. We derive general formulas for such functional determinants of r× r matrix second order differential operators O with 0 < n ≤slant 2r linearly independent zero modes. We separately discuss the cases of the homogeneous Dirichlet boundary conditions, when the number of zero modes cannot exceed r, and the case of twisted boundary conditions, including the periodic and anti-periodic ones, when the number of zero modes is bounded above by 2r. In all cases the determinants with excluded zero eigenvalues can be expressed only in terms of the n zero modes and other r-n or 2r-n (depending on the boundary conditions) solutions of the homogeneous equation O h=0 , in the spirit of Gel’fand-Yaglom approach. In instanton calculations, the contribution of the zero modes is taken into account by introducing the so-called collective coordinates. We show that there is a remarkable cancellation of a factor (involving scalar products of zero modes) between the Jacobian of the transformation to the collective coordinates and the functional fluctuation determinant with excluded zero eigenvalues. This cancellation drastically simplifies instanton calculations when one uses our formulas.

Scanning ultrafast electron microscopy

PubMed Central

Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

2010-01-01

Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

Effect of double-layer application on bond quality of adhesive systems.

PubMed

Fujiwara, Satoshi; Takamizawa, Toshiki; Barkmeier, Wayne W; Tsujimoto, Akimasa; Imai, Arisa; Watanabe, Hidehiko; Erickson, Robert L; Latta, Mark A; Nakatsuka, Toshiyuki; Miyazaki, Masashi

2018-01-01

The aim of this study was to determine the effect of double-layer application of universal adhesives on the bond quality and compare to other adhesive systems. Two universal adhesives used were in this study: Scotchbond Universal (SU), [3M ESPE] and Prime & Bond elect (PE), [Dentsply Caulk]. The conventional single-step self-etch adhesives G-ӕnial Bond (GB), [GC Corporation.] and BeautiBond (BB), [Shofu Inc.], and a two-step self-etch adhesive, Optibond XTR (OX), [Kerr Corporation], were used as comparison adhesives. Shear bond strengths (SBS) and shear fatigue strengths (SFS) to human enamel and dentin were measured in single application mode and double application mode. For each test condition, 15 specimens were prepared for SBS testing and 30 specimens for SFS testing. Enamel and dentin SBS of the universal adhesives in the double application mode were significantly higher than those of the single application mode. In addition, the universal adhesives in the double application mode had significantly higher dentin SFS values than those of the single application mode. The two-step self-etch adhesive OX tended to have lower bond strengths in the double application mode, regardless of the test method or adherent substrate. The double application mode is effective in enhancing SBS and SFS of universal adhesives, but not conventional two-step self-etch adhesives. These results suggest that, although the double application mode may enhance the bonding quality of a universal adhesive, it may be counter-productive for two-step self-etch adhesives in clinical use. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improved Numerical Calculation of the Single-Mode-No-Core-Single-Mode Fiber Structure Using the Fields Far from Cutoff Approximation

PubMed Central

Yang, Xianchao; Xu, Degang; Rong, Feng; Zhao, Junfa; Yao, Jianquan

2017-01-01

Multimode interferometers based on the single-mode-no-core-single-mode fiber (SNCS) structure have been widely investigated as functional devices and sensors. However, the theoretical support for the sensing mechanism is still imperfect, especially for the cladding refractive index response. In this paper, a modified model of no-core fiber (NCF) based on far from cut-off approximation is proposed to investigate the spectrum characteristic and sensing mechanism of the SNCS structure. Guided-mode propagation analysis (MPA) is used to analyze the self-image effect and spectrum response to the cladding refractive index and temperature. Verified by experiments, the performance of the SNCS structure can be estimated specifically and easily by the proposed method. PMID:28961174

Fiber laser with combined feedback of core and cladding modes assisted by an intracavity long-period grating.

PubMed

Sáez-Rodriguez, D; Cruz, J L; Díez, A; Andrés, M V

2011-05-15

We present a fiber laser made in a single piece of conventional doped-core fiber that operates by combined feedback of the fundamental core mode LP((0,1)) and the high-order cladding mode LP((0,10)). The laser is an all-fiber structure that uses two fiber Bragg gratings and a long-period grating to select the modes circulating in the cavity; the laser emits at the coupling wavelength between the core mode LP((0,1)) and the counterpropagating cladding mode LP((0,10)) in the Bragg gratings. This work demonstrates the feasibility of high-order mode fiber lasers assisted by long-period gratings. © 2011 Optical Society of America

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Tran, H. N.; Blancon, J.-C.; Arenal, R.; Parret, R.; Zahab, A. A.; Ayari, A.; Vallée, F.; Del Fatti, N.; Sauvajol, J.-L.; Paillet, M.

2017-05-01

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett. 108, 117404 (2012), 10.1103/PhysRevLett.108.117404]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modes permits us to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.

Low chemical concentrating steam generating cycle

DOEpatents

Mangus, James D.

1983-01-01

A steam cycle for a nuclear power plant having two optional modes of operation. A once-through mode of operation uses direct feed of coolant water to an evaporator avoiding excessive chemical concentration buildup. A recirculation mode of operation uses a recirculation loop to direct a portion of flow from the evaporator back through the evaporator to effectively increase evaporator flow.

High Energy, Single-Mode, All-Solid-State Nd:YAG Laser

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Hovis, Floyd

2006-01-01

In this paper, recent progress made in the design and development of an all-solid-state, single longitudinal mode, conductively cooled Nd:YAG laser operating at 1064 nm wavelength for UV lidar for ozone sensing applications is presented. Currently, this pump laser provides an output pulse energy of greater than 1.1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns. The spatial profile of the output beam is a rectangular super Gaussian. Electrical-to-optical system efficiency of greater than 7% and a minimum M(sup 2) value of less than 2 have been achieved.

Resonantly pumped single-mode channel waveguide Er:YAG laser with nearly quantum defect limited efficiency.

PubMed

Ter-Gabrielyan, N; Fromzel, V; Mu, X; Meissner, H; Dubinskii, M

2013-07-15

We demonstrated the continuous-wave operation of a resonantly pumped Er:YAG single-mode channel waveguide laser with diffraction-limited output and nearly quantum defect limited efficiency. Using a longitudinally core-pumped, nearly square (61.2 μm×61.6 μm) Er3+:YAG waveguide embedded in an undoped YAG cladding, an output power of 9.1 W with a slope efficiency of 92.8% (versus absorbed pump power) has been obtained. To the best of our knowledge, this optical-to-optical efficiency is the highest ever demonstrated for a channel waveguide laser.

Splicing Efficiently Couples Optical Fibers

NASA Technical Reports Server (NTRS)

Lutes, G. F.

1985-01-01

Method of splicing single-mode optical fibers results in very low transmission losses through joined fiber ends. Coupling losses between joined optical-fiber ends only 0.1 dB. Method needs no special operator training.

Operation of a quantum dot in the finite-state machine mode: Single-electron dynamic memory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klymenko, M. V.; Klein, M.; Levine, R. D.

2016-07-14

A single electron dynamic memory is designed based on the non-equilibrium dynamics of charge states in electrostatically defined metallic quantum dots. Using the orthodox theory for computing the transfer rates and a master equation, we model the dynamical response of devices consisting of a charge sensor coupled to either a single and or a double quantum dot subjected to a pulsed gate voltage. We show that transition rates between charge states in metallic quantum dots are characterized by an asymmetry that can be controlled by the gate voltage. This effect is more pronounced when the switching between charge states correspondsmore » to a Markovian process involving electron transport through a chain of several quantum dots. By simulating the dynamics of electron transport we demonstrate that the quantum box operates as a finite-state machine that can be addressed by choosing suitable shapes and switching rates of the gate pulses. We further show that writing times in the ns range and retention memory times six orders of magnitude longer, in the ms range, can be achieved on the double quantum dot system using experimentally feasible parameters, thereby demonstrating that the device can operate as a dynamic single electron memory.« less

Design of automatic curtain controlled by wireless based on single chip 51 microcomputer

NASA Astrophysics Data System (ADS)

Han, Dafeng; Chen, Xiaoning

2017-08-01

In order to realize the wireless control of the domestic intelligent curtains, a set of wireless intelligent curtain control system based on 51 single chip microcomputer have been designed in this paper. The intelligent curtain can work in the manual mode, automatic mode and sleep mode and can be carried out by the button and mobile phone APP mode loop switch. Through the photosensitive resistance module and human pyroelectric infrared sensor to collect the indoor light value and the data whether there is the person in the room, and then after single chip processing, the motor drive module is controlled to realize the positive inversion of the asynchronous motor, the intelligent opening and closing of the curtain have been realized. The operation of the motor can be stopped under the action of the switch and the curtain opening and closing and timing switch can be controlled through the keys and mobile phone APP. The optical fiber intensity, working mode, curtain state and system time are displayed by LCD1602. The system has a high reliability and security under practical testing and with the popularity and development of smart home, the design has broad market prospects.

Single-shot spectroscopy of broadband Yb fiber laser

NASA Astrophysics Data System (ADS)

Suzuki, Masayuki; Yoneya, Shin; Kuroda, Hiroto

2017-02-01

We have experimentally reported on a real-time single-shot spectroscopy of a broadband Yb-doped fiber (YDF) laser which based on a nonlinear polarization evolution by using a time-stretched dispersive Fourier transformation technique. We have measured an 8000 consecutive single-shot spectra of mode locking and noise-like pulse (NLP), because our developed broadband YDF oscillator can individually operate the mode locking and NLP by controlling a pump LD power and angle of waveplates. A shot-to-shot spectral fluctuation was observed in NLP. For the investigation of pulse formation dynamics, we have measured the spectral evolution in an initial fluctuations of mode locked broadband YDF laser at an intracavity dispersion of 1500 and 6200 fs2 for the first time. In both case, a build-up time between cw and steady-state mode locking was estimated to be 50 us, the dynamics of spectral evolution between cw and mode locking, however, was completely different. A shot-to-shot strong spectral fluctuation, as can be seen in NLP spectra, was observed in the initial timescale of 20 us at the intracavity dispersion of 1500 fs2. These new findings would impact on understanding the birth of the broadband spectral formation in fiber laser oscillator.

Mode-locked Tm,Ho:KLu(WO(4))(2) laser at 2060 nm using InGaSb-based SESAMs.

PubMed

Aleksandrov, Veselin; Gluth, Alexander; Petrov, Valentin; Buchvarov, Ivan; Steinmeyer, Günter; Paajaste, Jonna; Suomalainen, Soile; Härkönen, Antti; Guina, Mircea; Mateos, Xavier; Díaz, Francesc; Griebner, Uwe

2015-02-23

Passive mode-locking of a Tm,Ho:KLu(WO(4))(2) laser operating at 2060 nm using different designs of InGaAsSb quantum-well based semiconductor saturable absorber mirrors (SESAMs) is demonstrated. The self-starting mode-locked laser delivers pulse durations between 4 and 8 ps at a repetition rate of 93 MHz with maximum average output power of 155 mW. Mode-locking performance of a Tm,Ho:KLu(WO(4))(2) laser is compared for usage of a SESAM to a single-walled carbon nanotube saturable absorber.

ATE-TM mode splitter on lithium niobate using Ti, Ni, and MgO diffusions

NASA Astrophysics Data System (ADS)

Wei, Pei-Kuen; Wang, Way-Seen

1994-02-01

A new TE-TM mode splitter with an asymmetric Y-junction structure fabricated by diffusing different materials into y-cut lithium niobate is presented. Randomly polarized light launched into a titanium indiffused waveguide is split into TE and TM modes by two different single-polarization waveguides. The ordinary-polarized waveguide is made by nickel indiffusion and the extraordinary-polarized waveguide by magnesium-oxide induced lithium outdiffusion. The measured extinction ratios are greater than 20 dB for both TE and TM modes. The devices operate over a wide wavelength range and have a large fabrication tolerance.

New PbSnTe heterojunction laser diode structures with improved performance

NASA Technical Reports Server (NTRS)

Fonstad, C. G.; Kasemset, D.; Hsieh, H. H.; Rotter, S.

1980-01-01

Several recent advances in the state-of-the-art of lead tin telluride double heterojunction laser diodes are summarized. Continuous Wave operation to 120 K and pulsed operation to 166 K with single, lowest order transverse mode emission to in excess of four times threshold at 80 K were achieved in buried stripe lasers fabricated by liquid phase epitaxy in the lattice-matched system, lead-tin telluride-lead telluride selenide. At the same time, liquid phase epitaxy was used to produce PbSnTe distributed feedback lasers with much broader continuous single mode tuning ranges than are available from Fabry-Perot lasers. The physics and philosophy behind these advances is as important as the structures and performance of the specific devices embodying the advances, particularly since structures are continually being evolved and the performance continues to be improved.

Photo-excited charge carriers suppress sub-terahertz phonon mode in silicon at room temperature

DOE PAGES

Liao, Bolin; Maznev, A. A.; Nelson, Keith A.; ...

2016-10-12

There is a growing interest in the mode-by-mode understanding of electron and phonon transport for improving energy conversion technologies, such as thermoelectrics and photovoltaics. Whereas remarkable progress has been made in probing phonon–phonon interactions, it has been a challenge to directly measure electron–phonon interactions at the single-mode level, especially their effect on phonon transport above cryogenic temperatures. Here in this paper, we use three-pulse photoacoustic spectroscopy to investigate the damping of a single sub-terahertz coherent phonon mode by free charge carriers in silicon at room temperature. Building on conventional pump–probe photoacoustic spectroscopy, we introduce an additional laser pulse to opticallymore » generate charge carriers, and carefully design temporal sequence of the three pulses to unambiguously quantify the scattering rate of a single-phonon mode due to the electron–phonon interaction. Our results confirm predictions from first-principles simulations and indicate the importance of the often-neglected effect of electron–phonon interaction on phonon transport in doped semiconductors.« less

Geometric characterization of separability and entanglement in pure Gaussian states by single-mode unitary operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adesso, Gerardo; CNR-INFM Coherentia, Naples; CNISM, Unita di Salerno, Salerno

2007-10-15

We present a geometric approach to the characterization of separability and entanglement in pure Gaussian states of an arbitrary number of modes. The analysis is performed adapting to continuous variables a formalism based on single subsystem unitary transformations that has been recently introduced to characterize separability and entanglement in pure states of qubits and qutrits [S. M. Giampaolo and F. Illuminati, Phys. Rev. A 76, 042301 (2007)]. In analogy with the finite-dimensional case, we demonstrate that the 1xM bipartite entanglement of a multimode pure Gaussian state can be quantified by the minimum squared Euclidean distance between the state itself andmore » the set of states obtained by transforming it via suitable local symplectic (unitary) operations. This minimum distance, corresponding to a, uniquely determined, extremal local operation, defines an entanglement monotone equivalent to the entropy of entanglement, and amenable to direct experimental measurement with linear optical schemes.« less

Selective Sensing of Gas Mixture via a Temperature Modulation Approach: New Strategy for Potentiometric Gas Sensor Obtaining Satisfactory Discriminating Features

PubMed Central

Li, Fu-an; Jin, Han; Wang, Jinxia; Zou, Jie; Jian, Jiawen

2017-01-01

A new strategy to discriminate four types of hazardous gases is proposed in this research. Through modulating the operating temperature and the processing response signal with a pattern recognition algorithm, a gas sensor consisting of a single sensing electrode, i.e., ZnO/In2O3 composite, is designed to differentiate NO2, NH3, C3H6, CO within the level of 50–400 ppm. Results indicate that with adding 15 wt.% ZnO to In2O3, the sensor fabricated at 900 °C shows optimal sensing characteristics in detecting all the studied gases. Moreover, with the aid of the principle component analysis (PCA) algorithm, the sensor operating in the temperature modulation mode demonstrates acceptable discrimination features. The satisfactory discrimination features disclose the future that it is possible to differentiate gas mixture efficiently through operating a single electrode sensor at temperature modulation mode. PMID:28287492

Non-equilibrium many-body influence on mode-locked Vertical External-cavity Surface-emitting Lasers

NASA Astrophysics Data System (ADS)

Kilen, Isak Ragnvald

Vertical external-cavity surface-emitting lasers are ideal testbeds for studying the influence of the non-equilibrium many-body dynamics on mode locking. As we will show in this thesis, ultra short pulse generation involves a marked departure from Fermi carrier distributions assumed in prior theoretical studies. A quantitative model of the mode locking dynamics is presented, where the semiconductor Bloch equations with Maxwell's equation are coupled, in order to study the influences of quantum well carrier scattering on mode locking dynamics. This is the first work where the full model is solved without adiabatically eliminating the microscopic polarizations. In many instances we find that higher order correlation contributions (e.g. polarization dephasing, carrier scattering, and screening) can be represented by rate models, with the effective rates extracted at the level of second Born-Markov approximations. In other circumstances, such as continuous wave multi-wavelength lasing, we are forced to fully include these higher correlation terms. In this thesis we identify the key contributors that control mode locking dynamics, the stability of single pulse mode-locking, and the influence of higher order correlation in sustaining multi-wavelength continuous wave operation.

Heavily Yb-doped phosphate large-mode area all-solid photonic crystal fiber operating at 990 nm

NASA Astrophysics Data System (ADS)

Wang, Longfei; He, Dongbing; Feng, Suya; Yu, Chunlei; Hu, Lili; Qiu, Jianrong; Chen, Danping

2015-07-01

We demonstrate, for the first time to our knowledge, a 16 wt.% Yb-doped phosphate large-mode area all-solid photonic crystal fiber (AS-PCF) laser operating at 990 nm. By carefully tailoring the absorption and emission properties of the active glass and designing the structure of AS-PCF, the excitation of the 990 nm laser and the depression of the laser above 1 µm can be easily realized even without any wavelength-selective optics. The single-mode behavior of PCF with a 35 µm doped core, the largest core diameter of approximately 1 µm in phosphate fiber, is theoretically investigated by finite-difference time-domain method and experimentally confirmed.

Near-field analysis of metallic DFB lasers at telecom wavelengths.

PubMed

Greusard, L; Costantini, D; Bousseksou, A; Decobert, J; Lelarge, F; Duan, G-H; De Wilde, Y; Colombelli, R

2013-05-06

We image in near-field the transverse modes of semiconductor distributed feedback (DFB) lasers operating at λ ≈ 1.3 μm and employing metallic gratings. The active region is based on tensile-strained InGaAlAs quantum wells emitting transverse magnetic polarized light and is coupled via an extremely thin cladding to a nano-patterned gold grating integrated on the device surface. Single mode emission is achieved, which tunes with the grating periodicity. The near-field measurements confirm laser operation on the fundamental transverse mode. Furthermore--together with a laser threshold reduction observed in the DFB lasers--it suggests that the patterning of the top metal contact can be a strategy to reduce the high plasmonic losses in this kind of systems.

60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

PubMed Central

Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

2016-01-01

A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, −85 dBm and −110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10−3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications. PMID:27297267

Measurement of distributed strain and temperature based on higher order and higher mode Bragg conditions

NASA Technical Reports Server (NTRS)

Sirkis, James S. (Inventor); Sivanesan, Ponniah (Inventor); Venkat, Venki S. (Inventor)

2001-01-01

A Bragg grating sensor for measuring distributed strain and temperature at the same time comprises an optical fiber having a single mode operating wavelength region and below a cutoff wavelength of the fiber having a multimode operating wavelength region. A saturated, higher order Bragg grating having first and second order Bragg conditions is fabricated in the optical fiber. The first order of Bragg resonance wavelength of the Bragg grating is within the single mode operating wavelength region of the optical fiber and the second order of Bragg resonance wavelength is below the cutoff wavelength of the fiber within the multimode operating wavelength region. The reflectivities of the saturated Bragg grating at the first and second order Bragg conditions are less than two orders of magnitude of one another. In use, the first and second order Bragg conditions are simultaneously created in the sensor at the respective wavelengths and a signal from the sensor is demodulated with respect to each of the wavelengths corresponding to the first and second order Bragg conditions. Two Bragg conditions have different responsivities to strain and temperature, thus allowing two equations for axial strain and temperature to be found in terms of the measure shifts in the primary and second order Bragg wavelengths. This system of equations can be solved for strain and temperature.

Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

NASA Astrophysics Data System (ADS)

Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

2018-04-01

The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.

A braided monoidal category for free super-bosons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Runkel, Ingo, E-mail: ingo.runkel@uni-hamburg.de

The chiral conformal field theory of free super-bosons is generated by weight one currents whose mode algebra is the affinisation of an abelian Lie super-algebra h with non-degenerate super-symmetric pairing. The mode algebras of a single free boson and of a single pair of symplectic fermions arise for even|odd dimension 1|0 and 0|2 of h, respectively. In this paper, the representations of the untwisted mode algebra of free super-bosons are equipped with a tensor product, a braiding, and an associator. In the symplectic fermion case, i.e., if h is purely odd, the braided monoidal structure is extended to representations ofmore » the Z/2Z-twisted mode algebra. The tensor product is obtained by computing spaces of vertex operators. The braiding and associator are determined by explicit calculations from three- and four-point conformal blocks.« less

Monolithic single mode interband cascade lasers with wide wavelength tunability

NASA Astrophysics Data System (ADS)

von Edlinger, M.; Weih, R.; Scheuermann, J.; Nähle, L.; Fischer, M.; Koeth, J.; Kamp, M.; Höfling, S.

2016-11-01

Monolithic two-section interband cascade lasers offering a wide wavelength tunability in the wavelength range around 3.7 μm are presented. Stable single mode emission in several wavelength channels was realized using the concept of binary superimposed gratings and two-segment Vernier-tuning. The wavelength selective elements in the two segments were based on specially designed lateral metal grating structures defined by electron beam lithography. A dual-step dry etch process provided electrical separation between the segments. Individual current control of the segments allowed wavelength channel selection as well as continuous wavelength tuning within channels. A discontinuous tuning range extending over 158 nm in up to six discrete wavelength channels was achieved. Mode hop free wavelength tuning up to 14 nm was observed within one channel. The devices can be operated in continuous wave mode up to 30 °C with the output powers of 3.5 mW around room temperature.

Putting ROSE to Work: A Proposed Application of a Request-Oriented Scheduling Engine for Space Station Operations

NASA Technical Reports Server (NTRS)

Jaap, John; Muery, Kim

2000-01-01

Scheduling engines are found at the core of software systems that plan and schedule activities and resources. A Request-Oriented Scheduling Engine (ROSE) is one that processes a single request (adding a task to a timeline) and then waits for another request. For the International Space Station, a robust ROSE-based system would support multiple, simultaneous users, each formulating requests (defining scheduling requirements), submitting these requests via the internet to a single scheduling engine operating on a single timeline, and immediately viewing the resulting timeline. ROSE is significantly different from the engine currently used to schedule Space Station operations. The current engine supports essentially one person at a time, with a pre-defined set of requirements from many payloads, working in either a "batch" scheduling mode or an interactive/manual scheduling mode. A planning and scheduling process that takes advantage of the features of ROSE could produce greater customer satisfaction at reduced cost and reduced flow time. This paper describes a possible ROSE-based scheduling process and identifies the additional software component required to support it. Resulting changes to the management and control of the process are also discussed.

A novel L-shaped linear ultrasonic motor operating in a single resonance mode

NASA Astrophysics Data System (ADS)

Zhang, Bailiang; Yao, Zhiyuan; Liu, Zhen; Li, Xiaoniu

2018-01-01

In this study, a large thrust linear ultrasonic motor using an L-shaped stator is described. The stator is constructed by two mutually perpendicular rectangular plate vibrators, one of which is mounted in parallel with the slider to make the motor structure to be more compact. The symmetric and antisymmetric modes of the stator based on the first order bending vibration of two vibrators are adopted, in which each resonance mode is assigned to drive the slider in one direction. The placement of piezoelectric ceramics in a stator could be determined by finite element analysis, and the influence of slots in the head block on the vibration amplitudes of driving foot was studied as well. Three types of prototypes (non-slotted, dual-slot, and single-slot) were fabricated and experimentally investigated. Experimental results demonstrated that the prototype with one slot exhibited the best mechanical output performance. The maximum loads under the excitation of symmetric mode and antisymmetric mode were 65 and 90 N, respectively.

A novel L-shaped linear ultrasonic motor operating in a single resonance mode.

PubMed

Zhang, Bailiang; Yao, Zhiyuan; Liu, Zhen; Li, Xiaoniu

2018-01-01

In this study, a large thrust linear ultrasonic motor using an L-shaped stator is described. The stator is constructed by two mutually perpendicular rectangular plate vibrators, one of which is mounted in parallel with the slider to make the motor structure to be more compact. The symmetric and antisymmetric modes of the stator based on the first order bending vibration of two vibrators are adopted, in which each resonance mode is assigned to drive the slider in one direction. The placement of piezoelectric ceramics in a stator could be determined by finite element analysis, and the influence of slots in the head block on the vibration amplitudes of driving foot was studied as well. Three types of prototypes (non-slotted, dual-slot, and single-slot) were fabricated and experimentally investigated. Experimental results demonstrated that the prototype with one slot exhibited the best mechanical output performance. The maximum loads under the excitation of symmetric mode and antisymmetric mode were 65 and 90 N, respectively.

Electromagnetic Considerations for Planar Bolometer Arrays in the Single Mode Limit

NASA Technical Reports Server (NTRS)

Wollack, Edward J.; Chuss, David T.; Moseley, Samuel

2006-01-01

Filled arrays of planar bolometers are finding astronomical applications at wavelengths as long as several millimeters. In an effort to keep focal planes to a reasonable size while maintaining large numbers of detectors, a common strategy is to push these arrays to operate close to or at the single mode limit. Doing so introduces several new challenges that are not experienced in the multi-mode case of far-infrared detectors having similar pixel sizes. First, diffractive effects of the pixels themselves are no longer insignificant and will ultimately contribute to the resolution limit of the optical system in which they reside. We use the method of Withlngton et al. (2003) to model the polarized diffraction in this limit. Second, it is necessary to re-examine the coupling between the radiation and the absorbing element that is thermally connected to the bolometers. The small f-numbers that are often employed to make use of large focal planes makes backshort construction problematic. We introduce a new strategy to increase detector efficiency that uses an antireflective layer on the front side of the detector array. In addition, typical methods for stray light control that rely on multiple reflections in a lossy medium fail due to physical size constraints. For this application, we find that resonant absorbers are a more effective strategy that can be implemented in the space available.

Broadband arrayed waveguide grating multiplexers on indium phosphide

NASA Astrophysics Data System (ADS)

Rausch, Kameron

2005-11-01

Coarse Wavelength Division Multiplexing (CWDM) is becoming a popular way to increase the optical throughput of fibers for short to medium haul networks at a reduced cost. The International Telecommunications Union (ITU) has defined the CWDM network to consist of eighteen channels with channel spacings of 20 nm starting at 1270 nm and ending at 1610 nm. Four and eight channel AWGs suitable for CWDM were fabricated using a versatile S-shape design novel to InP. The standard horseshoe layout will not work on semiconductor for AWGs with a free spectral range (FSR) larger than 30 nm. The AWG design provides operation insensitive to thermal and polarization fluctuations; which is key for low cost operation and packaging. It will be shown that, refractive index changes over the large operating wavelength band produced negligible effects in the transmission spectrum. Standard AWG design assumes refractive index is a constant over the operating wavelength band. As a result, the output waveguide separations are held constant on the second star coupler. As the channel number increases, secondary focal dispersion caused from a changing refractive index can have detrimental effects on performance. A new design method will be introduced which includes refractive index dispersion by allowing the output waveguide separations to vary. The new design is consistent with standard design but is applicable in materials with a linear index dispersion over an arbitrarily large wavelength band. Lastly, a method for increasing the transmission using multimode waveguides is discussed. Traditionally, single mode waveguides are required in order to prevent higher order waveguide modes creating ghost images in the output spectrum. Using bend loss and waveguide junction offsets, higher order modes can be filtered from the output, thereby eliminating ghost images and at the same time, increase transmission.

Retrieval of Aerosol Microphysical Properties from AERONET Photo-Polarimetric Measurements. 2: A New Research Algorithm and Case Demonstration

NASA Technical Reports Server (NTRS)

Xu, Xiaoguang; Wang, Jun; Zeng, Jing; Spurr, Robert; Liu, Xiong; Dubovik, Oleg; Li, Li; Li, Zhengqiang; Mishchenko, Michael I.; Siniuk, Aliaksandr;

Simultaneous chiral discrimination of multiple profens by cyclodextrin-modified capillary electrophoresis in normal and reversed polarity modes.

PubMed

La, Sookie; Kim, Jiyung; Kim, Jung-Han; Goto, Junichi; Kim, Kyoung-Rae

2003-08-01

Simultaneous enantioseparations of nine profens for their accurate chiral discrimination were achieved by capillary electrophoresis (CE) in the normal polarity (NP) mode with a single cyclodextrin (CD) system and in the reversed polarity (RP) mode with a dual CD system. The single CD system in the NP mode employed heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMbetaCD) added at 75 mM-100 mM 2-(N-morpholino)ethanesulfonic acid buffer (pH 6.0) as the optimum run buffer. The dual CD system operated in the RP mode used 30 mM TMbetaCD and 1.0% anionic carboxymethyl-beta-cyclodextrin dissolved in pH 3.0, 100 mM phosphoric acid-triethanolamine buffer containing 0.01% hexadimethrine bromide added to reverse the electroosmotic flow. Fairly good enantiomeric resolutions and the opposite enantiomer migration orders were achieved in the two modes. Relative migration times to internal standard under respective optimum conditions were characteristic of each enantiomer with good precision (< 2% relative standard deviation, RSD), thereby enabling to crosscheck the chemical identification of profens and also their accurate chiralities. The method linearity in the two modes was found to be adequate (r > or = 0.9991) for the chiral assay of the profens investigated. Simultaneous enantiomeric purity test of ibuprofen, ketoprofen and flurbiprofen in a mixture was feasible in a single analysis by the present method.

Development and Measurements of a Mid-Infrared Multi-Gas Sensor System for CO, CO₂ and CH₄ Detection.

PubMed

Dong, Ming; Zheng, Chuantao; Miao, Shuzhuo; Zhang, Yu; Du, Qiaoling; Wang, Yiding; Tittel, Frank K

2017-09-27

A multi-gas sensor system was developed that uses a single broadband light source and multiple carbon monoxide (CO), carbon dioxide (CO₂) and methane (CH₄) pyroelectric detectors by use of the time division multiplexing (TDM) technique. A stepper motor-based rotating system and a single-reflection spherical optical mirror were designed and adopted to realize and enhance multi-gas detection. Detailed measurements under static detection mode (without rotation) and dynamic mode (with rotation) were performed to study the performance of the sensor system for the three gas species. Effects of the motor rotating period on sensor performances were also investigated and a rotation speed of 0.4π rad/s was required to obtain a stable sensing performance, corresponding to a detection period of ~10 s to realize one round of detection. Based on an Allan deviation analysis, the 1 σ detection limits under static operation are 2.96, 4.54 and 2.84 parts per million in volume (ppmv) for CO, CO₂ and CH₄, respectively and the 1 σ detection limits under dynamic operations are 8.83, 8.69 and 10.29 ppmv for the three gas species, respectively. The reported sensor has potential applications in various fields requiring CO, CO₂ and CH₄ detection such as in coal mines.

Optical interconnects based on VCSELs and low-loss silicon photonics

NASA Astrophysics Data System (ADS)

Aalto, Timo; Harjanne, Mikko; Karppinen, Mikko; Cherchi, Matteo; Sitomaniemi, Aila; Ollila, Jyrki; Malacarne, Antonio; Neumeyr, Christian

2018-02-01

Silicon photonics with micron-scale Si waveguides offers most of the benefits of submicron SOI technology while avoiding most of its limitations. In particular, thick silicon-on-insulator (SOI) waveguides offer 0.1 dB/cm propagation loss, polarization independency, broadband single-mode (SM) operation from 1.2 to >4 µm wavelength and ability to transmit high optical powers (>1 W). Here we describe the feasibility of Thick-SOI technology for advanced optical interconnects. With 12 μm SOI waveguides we demonstrate efficient coupling between standard single-mode fibers, vertical-cavity surface-emitting lasers (VCSELs) and photodetectors (PDs), as well as wavelength multiplexing in small footprint. Discrete VCSELs and PDs already support 28 Gb/s on-off keying (OOK), which shows a path towards 50-100 Gb/s bandwidth per wavelength by using more advanced modulation formats like PAM4. Directly modulated VCSELs enable very power-efficient optical interconnects for up to 40 km distance. Furthermore, with 3 μm SOI waveguides we demonstrate extremely dense and low-loss integration of numerous optical functions, such as multiplexers, filters, switches and delay lines. Also polarization independent and athermal operation is demonstrated. The latter is achieved by using short polymer waveguides to compensate for the thermo-optic effect in silicon. New concepts for isolator integration and polarization rotation are also explained.

Heat transfer analysis of underground U-type heat exchanger of ground source heat pump system.

PubMed

Pei, Guihong; Zhang, Liyin

2016-01-01

Ground source heat pumps is a building energy conservation technique. The underground buried pipe heat exchanging system of a ground source heat pump (GSHP) is the basis for the normal operation of an entire heat pump system. Computational-fluid-dynamics (CFD) numerical simulation software, ANSYS-FLUENT17.0 have been performed the calculations under the working conditions of a continuous and intermittent operation over 7 days on a GSHP with a single-well, single-U and double-U heat exchanger and the impact of single-U and double-U buried heat pipes on the surrounding rock-soil temperature field and the impact of intermittent operation and continuous operation on the outlet water temperature. The influence on the rock-soil temperature is approximately 13 % higher for the double-U heat exchanger than that of the single-U heat exchanger. The extracted energy of the intermittent operation is 36.44 kw·h higher than that of the continuous mode, although the running time is lower than that of continuous mode, over the course of 7 days. The thermal interference loss and quantity of heat exchanged for unit well depths at steady-state condition of 2.5 De, 3 De, 4 De, 4.5 De, 5 De, 5.5 De and 6 De of sidetube spacing are detailed in this work. The simulation results of seven working conditions are compared. It is recommended that the side-tube spacing of double-U underground pipes shall be greater than or equal to five times of outer diameter (borehole diameter: 180 mm).

Investigation of 2.1-micron lasing properties of Ho:Tm:Cr:YAG crystals under flash-lamp pumping at various operating conditions

NASA Technical Reports Server (NTRS)

Kim, Kyong H.; Choi, Young S.; Barnes, Norman P.; Hess, Robert V.; Bair, Clayton H.; Brockman, Philip

1993-01-01

Flash-lamp-pumped normal-mode and Q-switched 2.1-micron laser operations of Ho:Tm:Cr:YAG crystals have been evaluated under a wide variety of experimental conditions in order to determine an optimum lasing condition and to characterize the laser outputs. Q-switched laser-output energies equal to, or in some cases exceeding the normal-mode laser energies, were obtained in the form of a strong single spike through an optimization of the opening time of a lithium niobate Q switch. The increase of the normal-mode laser slope efficiency was observed with the increase of the Tm concentration from 2.5 to 4.5 at. pct at operating temperatures from 120 K to near room temperature. Laser transitions were observed only at 2.098 and 2.091 microns under various conditions. The 2.091-micron laser transition appeared to be dominant at high-temperature operations with low-reflective-output couplers.

Investigation of sulfonated polysulfone membranes as electrolyte in a passive-mode direct methanol fuel cell mini-stack

NASA Astrophysics Data System (ADS)

Lufrano, F.; Baglio, V.; Staiti, P.; Stassi, A.; Aricò, A. S.; Antonucci, V.

This paper reports on the development of polymer electrolyte membranes (PEMs) based on sulfonated polysulfone for application in a DMFC mini-stack operating at room temperature in passive mode. The sulfonated polysulfone (SPSf) with two degrees of sulfonation (57 and 66%) was synthesized by a well-known sulfonation process. SPSf membranes with different thicknesses were prepared and investigated. These membranes were characterized in terms of methanol/water uptake, proton conductivity, and fuel cell performance in a DMFC single cell and mini-stack operating at room temperature. The study addressed (a) control of the synthesis of sulfonated polysulfone, (b) optimization of the assembling procedure, (c) a short lifetime investigation and (d) a comparison of DMFC performance in active-mode operation vs. passive-mode operation. The best passive DMFC performance was 220 mW (average cell power density of about 19 mW cm -2), obtained with a thin SPSf membrane (70 μm) at room temperature, whereas the performance of the same membrane-based DMFC in active mode was 38 mW cm -2. The conductivity of this membrane, SPSf (IEC = 1.34 mequiv. g -1) was 2.8 × 10 -2 S cm -1. A preliminary short-term test (200 min) showed good stability during chrono-amperometry measurements.

Relativistic backward wave oscillator operating in TM02 with cutoff-type resonant reflector

NASA Astrophysics Data System (ADS)

Teng, Yan; Shi, Yanchao; Yang, Dewen; Cao, Yibing; Zhang, Zhijun

2017-04-01

This paper proposes an overmoded relativistic backward wave oscillator (RBWO) operating in the TM02 mode with the cutoff-type resonant reflector characterized by the advantages of the cutoff neck and the single resonant cavity. In order to protect the explosive emission of the annular cathode from the disturbance of the microwave leakage, the cutoff-type resonant reflector can effectively prevent the microwave consisting of several modes from propagating into the diode region. Attributed to the strong reflections caused by the cutoff-type resonant reflector at the front end of the overmoded slow-wave structure (SWS), the overmoded RBWO works in the state of the strong resonance, which enhances the beam-to-microwave power conversion efficiency. TM02 is selected as the operation mode so as to increase the power handling capability. The nonuniform SWS depresses the cross-excitation of the unwanted longitudinal modes of TM02 and improves the synchronous interaction between the electron beam and the structure wave. It is found that when we make the peak values of the longitudinal electric field and the modulated current appear nearly at the same position in the overmoded SWS by optimizing the electrodynamic structure, the conversion efficiency will be enhanced significantly. In the numerical simulation, the microwave generation with power 2.99 GW and efficiency 0.45 is obtained under the diode voltage 851 kV and current 7.8 kA with the guide magnetic field of 4.3 T. The microwave generation with the pure frequency spectrum of 10.083 GHz radiates in the TM01 mode. The conversion efficiency keeps above 0.40 over the diode voltage range of 220 kV.

Continuous-wave optical stimulation of the rat prostate nerves using an all-single-mode 1455 nm diode laser and fiber system

NASA Astrophysics Data System (ADS)

Tozburun, Serhat; Lagoda, Gwen A.; Burnett, Arthur L.; Fried, Nathaniel M.

2011-03-01

Optical nerve stimulation (ONS) has recently been reported as a potential alternative to electrical nerve stimulation. Continuous-wave (CW) laser stimulation of the prostate cavernous nerves (CN) in a rat model, in vivo, has also been demonstrated in our previous studies. The objective of this study is to present a new all-single-mode-fiber configuration for ONS with the laser operating in CW mode for potential diagnostic applications. An infrared pigtailed single-mode diode laser (λ = 1455 nm) was used in this study for noncontact ONS. This new all-fiber approach introduces several advantages including: (1) a less expensive and more compact ONS system, (2) elimination of alignment of optical components, and (3) an improved spatial beam profile. Successful optical stimulation of the rat CN using this new design was observed after the CN reached a threshold temperature of ~ 41 °C with response times as short as 3 s. Upon further study, this configuration may be useful for identification and preservation of the cavernous nerves during prostate cancer surgery.

Remarkable influence of slack on the vibration of a single-walled carbon nanotube resonator

NASA Astrophysics Data System (ADS)

Ning, Zhiyuan; Fu, Mengqi; Wu, Gongtao; Qiu, Chenguang; Shu, Jiapei; Guo, Yao; Wei, Xianlong; Gao, Song; Chen, Qing

2016-04-01

We for the first time quantitatively investigate experimentally the remarkable influence of slack on the vibration of a single-walled carbon nanotube (SWCNT) resonator with a changeable channel length fabricated in situ inside a scanning electron microscope, compare the experimental results with the theoretical predictions calculated from the measured geometric and mechanical parameters of the same SWCNT, and find the following novel points. We demonstrate experimentally that as the slack s is increased from about zero to 1.8%, the detected vibration transforms from single-mode to multimode vibration, and the gate-tuning ability gradually attenuates for all the vibration modes. The quadratic tuning coefficient α decreases linearly with when the gate voltage Vdcg is small and the nanotube resonator operates in the beam regime. The linear tuning coefficient γ decreases linearly with when Vdcg has an intermediate value and the nanotube resonator operates in the catenary regime. The calculated α and γ fit the experimental values of the even in-plane mode reasonably well. As the slack is increased, the quality factor Q of the resonator linearly goes up, but the increase is far less steep than that predicted by the previous theoretical study. Our results are important to understand and design resonators based on CNT and other nanomaterials.

Characterization of wastewater treatment by two microbial fuel cells in continuous flow operation.

PubMed

Kubota, Keiichi; Watanabe, Tomohide; Yamaguchi, Takashi; Syutsubo, Kazuaki

2016-01-01

A two serially connected single-chamber microbial fuel cell (MFC) was applied to the treatment of diluted molasses wastewater in a continuous operation mode. In addition, the effect of series and parallel connection between the anodes and the cathode on power generation was investigated experimentally. The two serially connected MFC process achieved 79.8% of chemical oxygen demand removal and 11.6% of Coulombic efficiency when the hydraulic retention time of the whole process was 26 h. The power densities were 0.54, 0.34 and 0.40 W m(-3) when electrodes were in individual connection, serial connection and parallel connection modes, respectively. A high open circuit voltage was obtained in the serial connection. Power density decreased at low organic loading rates (OLR) due to the shortage of organic matter. Power generation efficiency tended to decrease as a result of enhancement of methane fermentation at high OLRs. Therefore, high power density and efficiency can be achieved by using a suitable OLR range.

Generation of dual-wavelength square pulse in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion.

PubMed

Shao, Zhihua; Qiao, Xueguang; Rong, Qiangzhou; Su, Dan

2015-08-01

A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.

Low-noise two-wired buffer electrodes for bioelectric amplifiers.

PubMed

Degen, Thomas; Torrent, Simon; Jäckel, Heinz

2007-07-01

Active buffer electrodes are known to improve the immunity of bioelectric recordings against power line interferences. A survey of published work reveals that buffer electrodes are almost exclusively designed using operational amplifiers (opamps). In this paper, we discuss the advantage of utilizing a single transistor instead. This allows for a simple electrode, which is small and requires only two wires. In addition, a single transistor adds considerably less noise when compared to an opamp with the same power consumption. We then discuss output resistance and gain as well as their respective effect on the common mode rejection ratio (CMRR). Finally, we demonstrate the use of two-wired buffer electrodes for a bioelectric amplifier.

Single transverse mode protein laser

NASA Astrophysics Data System (ADS)

Dogru, Itir Bakis; Min, Kyungtaek; Umar, Muhammad; Bahmani Jalali, Houman; Begar, Efe; Conkar, Deniz; Firat Karalar, Elif Nur; Kim, Sunghwan; Nizamoglu, Sedat

2017-12-01

Here, we report a single transverse mode distributed feedback (DFB) protein laser. The gain medium that is composed of enhanced green fluorescent protein in a silk fibroin matrix yields a waveguiding gain layer on a DFB resonator. The thin TiO2 layer on the quartz grating improves optical feedback due to the increased effective refractive index. The protein laser shows a single transverse mode lasing at the wavelength of 520 nm with the threshold level of 92.1 μJ/ mm2.

Influence of high power 405 nm multi-mode and single-mode diode laser light on the long-term stability of fused silica fibers

NASA Astrophysics Data System (ADS)

Gonschior, C. P.; Klein, K.-F.; Sun, T.; Grattan, K. T. V.

2012-04-01

As the demand for high power fiber-coupled violet laser systems increases existing problems remain. The typical power of commercially available diode lasers around 400 nm is in the order of 100 to 300 mW, depending on the type of laser. But in combination with the small core of single-mode fibers reduced spot sizes are needed for good coupling efficiencies, leading to power densities in the MW/cm2 range. We investigated the influence of 405 nm laser light irradiation on different fused silica fibers and differently treated end-faces. The effect of glued-and-polished, cleaved-and-clamped and of cleaved-and-fusion-arc-treated fiber end-faces on the damage rate and behavior are presented. In addition, effects in the deep ultra-violet were determined spectrally using newest spectrometer technology, allowing the measurement of color centers around 200 nm in small core fibers. Periodic surface structures were found on the proximal end-faces and were investigated concerning generation control parameters and composition. The used fiber types range from low-mode fiber to single-mode and polarization-maintaining fiber. For this investigation 405 nm single-mode or multi-mode diode lasers with 150 mW or 300 mW, respectively, were employed.

Towards a 1 MW, 170 GHz gyrotron design for fusion application

NASA Astrophysics Data System (ADS)

Kumar, Anil; Kumar, Nitin; Singh, Udaybir; Bhattacharya, Ranajoy; Yadav, Vivek; Sinha, A. K.

2013-03-01

The electrical design of different components of 1 MW, 170 GHz gyrotron such as, magnetron injection gun, cylindrical interaction cavity and collector and RF window is presented in this article. Recently, a new project related to the development of 170 GHz, 1 MW gyrotron has been started for the Indian Tokamak. TE34,10 mode is selected as the operating mode after studied the problem of mode competition. The triode type geometry is selected for the design of magnetron injection gun (MIG) to achieve the required beam parameters. The maximum transverse velocity spread of 3.28% at the velocity ratio of 1.34 is obtained in simulations for a 40 A, 80 kV electron beam. The RF output power of more than 1 MW with 36.5% interaction efficiency without depressed collector is predicted by simulation in single-mode operation at 170 GHz frequency. The simulated single-stage depressed collector of the gyrotron predicted the overall device efficiencies >55%. Due to the very good thermal conductivity and very weak dependency of the dielectric parameters on temperature, PACVD diamond is selected for window design for the transmission of RF power. The in-house developed code MIGSYN and GCOMS are used for initial geometry design of MIG and mode selection respectively. Commercially available simulation tools MAGIC and ANSYS are used for beam-wave interaction and mechanical analysis respectively.

Adiabatically tapered splice for selective excitation of the fundamental mode in a multimode fiber.

PubMed

Jung, Yongmin; Jeong, Yoonchan; Brambilla, Gilberto; Richardson, David J

2009-08-01

We propose a simple and effective method to selectively excite the fundamental mode of a multimode fiber by adiabatically tapering a fusion splice to a single-mode fiber. We experimentally demonstrate the method by adiabatically tapering splice (taper waist=15 microm, uniform length=40 mm) between single-mode and multimode fiber and show that it provides a successful mode conversion/connection and allows for almost perfect fundamental mode excitation in the multimode fiber. Excellent beam quality (M(2) approximately 1.08) was achieved with low loss and high environmental stability.

Negative Avalanche Feedback Detectors for Photon-Counting Optical Communications

NASA Technical Reports Server (NTRS)

Farr, William H.

2009-01-01

Negative Avalanche Feedback photon counting detectors with near-infrared spectral sensitivity offer an alternative to conventional Geiger mode avalanche photodiode or phototube detectors for free space communications links at 1 and 1.55 microns. These devices demonstrate linear mode photon counting without requiring any external reset circuitry and may even be operated at room temperature. We have now characterized the detection efficiency, dark count rate, after-pulsing, and single photon jitter for three variants of this new detector class, as well as operated these uniquely simple to use devices in actual photon starved free space optical communications links.

A method to identify the main mode of machine tool under operating conditions

NASA Astrophysics Data System (ADS)

Wang, Daming; Pan, Yabing

2017-04-01

The identification of the modal parameters under experimental conditions is the most common procedure when solving the problem of machine tool structure vibration. However, the influence of each mode on the machine tool vibration in real working conditions remains unknown. In fact, the contributions each mode makes to the machine tool vibration during machining process are different. In this article, an active excitation modal analysis is applied to identify the modal parameters in operational condition, and the Operating Deflection Shapes (ODS) in frequencies of high level vibration that affect the quality of machining in real working conditions are obtained. Then, the ODS is decomposed by the mode shapes which are identified in operational conditions. So, the contributions each mode makes to machine tool vibration during machining process are got by decomposition coefficients. From the previous steps, we can find out the main modes which effect the machine tool more significantly in working conditions. This method was also verified to be effective by experiments.

Mode Selection for a Single-Frequency Fiber Laser

NASA Technical Reports Server (NTRS)

Liu, Jian

2010-01-01

A superstructured fiber-grating-based mode selection filter for a single-frequency fiber laser eliminates all free-space components, and makes the laser truly all-fiber. A ring cavity provides for stable operations in both frequency and power. There is no alignment or realignment required. After the fibers and components are spliced together and packaged, there is no need for specially trained technicians for operation or maintenance. It can be integrated with other modules, such as telescope systems, without extra optical alignment due to the flexibility of the optical fiber. The filter features a narrow line width of 1 kHz and side mode suppression ratio of 65 dB. It provides a high-quality laser for lidar in terms of coherence length and signal-to-noise ratio, which is 20 dB higher than solid-state or microchip lasers. This concept is useful in material processing, medical equipment, biomedical instrumentation, and optical communications. The pulse-shaping fiber laser can be directly used in space, airborne, and satellite applications including lidar, remote sensing, illuminators, and phase-array antenna systems.

Theory of CW lidar aerosol backscatter measurements and development of a 2.1 microns solid-state pulsed laser radar for aerosol backscatter profiling

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Henderson, Sammy W.; Frehlich, R. G.

1991-01-01

The performance and calibration of a focused, continuous wave, coherent detection CO2 lidar operated for the measurement of atmospheric backscatter coefficient, B(m), was examined. This instrument functions by transmitting infrared (10 micron) light into the atmosphere and collecting the light which is scattered in the rearward direction. Two distinct modes of operation were considered. In volume mode, the scattered light energy from many aerosols is detected simultaneously, whereas in the single particle mode (SPM), the scattered light energy from a single aerosol is detected. The analysis considered possible sources of error for each of these two cases, and also considered the conditions where each technique would have superior performance. The analysis showed that, within reasonable assumptions, the value of B(m) could be accurately measured by either the VM or the SPM method. The understanding of the theory developed during the analysis was also applied to a pulsed CO2 lidar. Preliminary results of field testing of a solid state 2 micron lidar using a CW oscillator is included.

Influence of mode-beating pulse on laser-induced plasma

NASA Astrophysics Data System (ADS)

Nishihara, M.; Freund, J. B.; Glumac, N. G.; Elliott, G. S.

2018-04-01

This paper addresses the influence of mode-beating pulse on laser-induced plasma. The second harmonic of a Nd:YAG laser, operated either with the single mode or multimode, was used for non-resonant optical breakdown, and subsequent plasma development was visualized using a streak imaging system. The single mode lasing leads to a stable breakdown location and smooth envelopment of the plasma boundary, while the multimode lasing, with the dominant mode-beating frequency of 500-800 MHz, leads to fluctuations in the breakdown location, a globally modulated plasma surface, and growth of local microstructures at the plasma boundary. The distribution of the local inhomogeneity was measured from the elastic scattering signals on the streak image. The distance between the local structures agreed with the expected wavelength of hydrodynamic instability development due to the interference between the surface excited wave and transmitted wave. A numerical simulation, however, indicates that the local microstructure could also be directly generated at the peaks of the higher harmonic components if the multimode pulse contains up to the eighth harmonic of the fundamental cavity mode.

Active control of a flexible structure using a modal positive position feedback controller

NASA Technical Reports Server (NTRS)

Poh, S.; Baz, A.

1990-01-01

The feasibility of a new Modal Positive Position Feedback (MPPF) strategy in controlling the vibration of a complex flexible structure using a single piezo-electric active structural member is demonstrated. The control strategy generates its control forces by manipulating only the modal position signals of the structure to provide a damping action to undamped modes. This is in contrast to conventional modal controllers that rely in their operation on negative feedback of both the modal position and velocity. The proposed strategy is very simple to design and implement as it designs the controller at the uncoupled modal level and utilizes simple first order filters to achieve the Positive Position Feedback effect. The performance of the new strategy is enhanced by augmenting it with a time sharing strategy to share a small number of actuators between larger number of modes. The effectiveness of the new strategy is validated experimentally on a flexible box-type structure that has four bays and its first two bending modes are 2.015 and 6.535 Hz respectively. A single piezo-electric actuator is utilized as an active structural member to control several transverse bending modes of the structure. The performance of the active control system is determined in the time and the frequency domains. The results are compared with those obtained when using the Independent Modal Space Control (IMSC) of Meirovitch. The experimental results suggest the potential of the proposed strategy as a viable means for controlling the vibration of large flexible structures in real time.

The design and development of an automatic control system for the in-duct cancellation of spinning modes of sound. M.S. Thesis

NASA Technical Reports Server (NTRS)

Harrington, W. W.

1973-01-01

The reduction is discussed of the discrete tones generated by jet engines which is essential for jet aircraft to meet present and proposed noise standards. The discrete tones generated by the blades and vanes propagate in the inlet and exhaust duct in the form of spiraling acoustic waves, or spinning modes. The reduction of these spinning modes by the cancellation effect of the combination of two acoustic fields was investigated. The spinning mode synthesizer provided the means for effective study of this noise reduction scheme. Two sets of electrical-acoustical transducers located in an equally-spaced circular array simultaneously generate a specified spinning mode and the cancelling mode. Analysis of the wave equation for the synthesizer established the optimum cancelling array acoustic parameters for maximum sound pressure level reduction. The parameter dependence of the frequency ranges of propagation of single, specified circumferential modes generated by a single array, and of effective cancellation of the modes generated by two arrays, was determined. Substantial sound pressure level reduction was obtained for modes within these limits.

Launch device using endlessly single-mode PCF for ultra-wideband WDM transmission in graded-index multi-mode fiber.

PubMed

Ma, Lin; Hanzawa, Nobutomo; Tsujikawa, Kyozo; Azuma, Yuji

2012-10-22

We demonstrated ultra-wideband wavelength division multiplexing (WDM) transmission from 850 to 1550 nm in graded-index multi-mode fiber (GI-MMF) using endlessly single-mode photonic crystal fiber (ESM-PCF) as a launch device. Effective single-mode guidance is obtained in multi-mode fiber at all wavelengths by splicing cm-order length ESM-PCF to the transmission fiber. We achieved 3 × 10 Gbit/s WDM transmission in a 1 km-long 50-μm-core GI-MMF. We also realized penalty free 10 Gbit/s data transmission at a wavelength of 850 nm by optimizing the PCF structure. This method has the potential to achieve greater total transmission capacity for MMF systems by the addition of more wavelength channels.

Single-mode 140 nm swept light source realized by using SSG-DBR lasers

NASA Astrophysics Data System (ADS)

Fujiwara, N.; Yoshimura, R.; Kato, K.; Ishii, H.; Kano, F.; Kawaguchi, Y.; Kondo, Y.; Ohbayashi, K.; Oohashi, H.

2008-02-01

We demonstrate a single-mode and fast wavelength swept light source by using Superestrucuture grating distributed Bragg reflector (SSG-DBR) lasers for use in optical frequency-domain reflectometry optical coherence tomography. The SSG-DBR lasers provide single-mode operation resulting in high coherency. Response of the wavelength tuning is very fast; several nanoseconds, but there was an unintentional wavelength drift resulting from a thermal drift due to injecting tuning current. The dri1ft unfortunately requires long time to converge; more than a few milliseconds. For suppressing the wavelength drift, we introduced Thermal Drift Compensation mesa (TDC) parallel to the laser mesa with the spacing of 20 μm. By controlling TDC current to satisfy the total electric power injected into both the laser mesa and the TDC mesa, the thermal drift can be suppressed. In the present work, we fabricated 4 wavelength's kinds of SSG-DBR laser, which covers respective wavelength band; S-band (1496-1529 nm), C-band (1529-1564 nm), L --band (1564-1601 nm), and L +-band (1601-1639). We set the frequency channel of each laser with the spacing 6.25 GHz and 700 channels. The total frequency channel number is 2800 channels (700 ch × 4 lasers). We simultaneously operated the 4 lasers with a time interval of 500 ns/channel. A wavelength tuning range of more than 140 nm was achieved within 350 μs. The output power was controlled to be 10 mW for all channels. A single-mode, accurate, wide, and fast wavelength sweep was demonstrated with the SSG-DBR lasers having TDC mesa structure for the first time.

Ultra low-loss hybrid core porous fiber for broadband applications.

PubMed

Islam, Md Saiful; Sultana, Jakeya; Atai, Javid; Abbott, Derek; Rana, Sohel; Islam, Mohammad Rakibul

2017-02-01

In this paper, we present the design and analysis of a novel hybrid porous core octagonal lattice photonic crystal fiber for terahertz (THz) wave guidance. The numerical analysis is performed using a full-vector finite element method (FEM) that shows that 80% of bulk absorption material loss of cyclic olefin copolymer (COC), commercially known as TOPAS can be reduced at a core diameter of 350 μm. The obtained effective material loss (EML) is as low as 0.04  cm^-1 at an operating frequency of 1 THz with a core porosity of 81%. Moreover, the proposed photonic crystal fiber also exhibits comparatively higher core power fraction, lower confinement loss, higher effective mode area, and an ultra-flattened dispersion profile with single mode propagation. This fiber can be readily fabricated using capillary stacking and sol-gel techniques, and it can be used for broadband terahertz applications.

Q-switched and mode-locked Er{sup 3+}-doped fibre laser using a single-multi-single fibre filter and piezoelectric

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji Wang; Yunjun Zhang; Aotuo Dong

2014-04-28

The active Q-switched and passive mode-locked Er{sup 3+}-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energymore » is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 μs, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 μJ, and the energy of every mode-locked pulse is about 64–68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses. (lasers)« less

Versatile current-mode universal biquadratic filter using DO-CCIIs

NASA Astrophysics Data System (ADS)

Chen, Hua-Pin

2013-07-01

In this article, a new three-input and three-output versatile current-mode universal biquadratic filter is proposed. The circuit employs three dual-output current conveyors (DO-CCIIs) as active elements together with three grounded resistors and two grounded capacitors. The proposed configuration exhibits low-input impedance and high-output impedance which is important for easy cascading in the current-mode operations. It can be used as either a single-input and three-output or three-input and two-output circuit. In the operation of single-input and three-output circuit, the lowpass, bandpass and bandreject can be realised simultaneously, while the highpass filtering response can be easily obtained by connecting appropriated output current directly without using addition stages. In the operation of three-input and two-output circuit, all five generic filtering functions can be easily realised by selecting different three input current signals. The filter permits orthogonal controllability of the quality factor and resonance angular frequency, and no component matching conditions or inverting-type input current signals are imposed. All the passive and active sensitivities are low. HSPICE simulation results based on using TSMC 0.18 µm 1P6M CMOS process technology and supply voltages ±0.9 V to verify the theoretical analysis.

Three dimensional chiral plasmon rulers based on silver nanorod trimers.

PubMed

Han, Chunrui; Yang, Lechen; Ye, Piao; Parrott, Edward P J; Pickwell-Macpherson, Emma; Tam, Wing Yim

2018-04-16

The symmetry dependences of plasmon excitation modes are studied in 3D silver nanorod trimers. The degenerate plasmon modes split into chiral modes by breaking the inversion and mirror symmetry of the nanorod trimer through translation and/or rotation of the middle rod. With a translation operation, successive evolution of the circular dichroism (CD) spectrum can be achieved through gradual breaking of the inversion symmetry. An additional rotation operation produces even dramatic spectral changes due to breaking a quasi-mirror symmetry resulted from the same angular distance of the middle rod to the top and bottom rods. Especially, pairs of new chiral modes can be excited due to the contact of the middle rod with the top-bottom rod pair. The spectral changes in the simulations, which are also demonstrated experimentally, envision the 3D chiral nanorod trimer system as plasmon ruler for spatial configuration retrieval and dynamic bio-process analysis at the single molecule level.

A square-plate ultrasonic linear motor operating in two orthogonal first bending modes.

PubMed

Chen, Zhijiang; Li, Xiaotian; Chen, Jianguo; Dong, Shuxiang

2013-01-01

A novel square-plate piezoelectric ultrasonic linear motor operated in two orthogonal first bending vibration modes (B₁) is proposed. The piezoelectric vibrator of the linear motor is simply made of a single PZT ceramic plate (sizes: 15 x 15 x 2 mm) and poled in its thickness direction. The top surface electrode of the square ceramic plate was divided into four active areas along its two diagonal lines for exciting two orthogonal B₁ modes. The achieved driving force and speed from the linear motor are 1.8 N and 230 mm/s, respectively, under one pair orthogonal voltage drive of 150 V(p-p) at the resonance frequency of 92 kHz. The proposed linear motor has advantages over conventional ultrasonic linear motors, such as relatively larger driving force, very simple working mode and structure, and low fabrication cost.

Linear aerospike engine study. [for reusable launch vehicles

NASA Technical Reports Server (NTRS)

Diem, H. G.; Kirby, F. M.

1977-01-01

Parametric data on split-combustor linear engine propulsion systems are presented for use in mixed-mode single-stage-to-orbit (SSTO) vehicle studies. Preliminary design data for two selected engine systems are included. The split combustor was investigated for mixed-mode operations with oxygen/hydrogen propellants used in the inner combustor in Mode 2, and in conjunction with either oxygen/RP-1, oxygen/RJ-5, O2/CH4, or O2/H2 propellants in the outer combustor for Mode 1. Both gas generator and staged combustion power cycles were analyzed for providing power to the turbopumps of the inner and outer combustors. Numerous cooling circuits and cooling fluids (propellants) were analyzed and hydrogen was selected as the preferred coolant for both combustors and the linear aerospike nozzle. The maximum operating chamber pressure was determined to be limited by the availability of hydrogen coolant pressure drop in the coolant circuit.

Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

NASA Technical Reports Server (NTRS)

Hallock, A. K.; Martin, A. K.; Polzin, K. A.; Kimberlin, A. C.; Eskridge, R. H.

2013-01-01

Impulse bits produced by conical theta-pinch inductive pulsed plasma thrusters possessing cone angles of 20deg, 38deg, and 60deg, were quantified for 500J/pulse operation by direct measurement using a hanging-pendulum thrust stand. All three cone angles were tested in single-pulse mode, with the 38deg model producing the highest impulse bits at roughly 1 mN-s operating on both argon and xenon propellants. A capacitor charging system, assembled to support repetitively-pulsed thruster operation, permitted testing of the 38deg thruster at a repetition-rate of 5 Hz at power levels of 0.9, 1.6, and 2.5 kW. The average thrust measured during multiple-pulse operation exceeded the value obtained when the single-pulse impulse bit is multiplied by the repetition rate.

Stable CW Single-Frequency Operation of Fabry-Perot Laser Diodes by Self-Injection Phase Locking

NASA Technical Reports Server (NTRS)

Duerksen, Gary L.; Krainak, Michael A.

1999-01-01

Previously, single-frequency semiconductor laser operation using fiber Bragg gratings has been achieved by two methods: 1) use of the FBG as the output coupler for an anti-reflection-coated semiconductor gain element'; 2) pulsed operation of a gain-switched Fabry-Perot laser diode with FBG-optical and RF-electrical feedback. Here, we demonstrate CW single frequency operation from a non-AR coated Fabry-Perot laser diode using only FBG optical feedback. We coupled a nominal 935 run-wavelength Fabry-Perot laser diode to an ultra narrow band (18 pm) FBG. When tuned by varying its temperature, the laser wavelength is pulled toward the centerline of the Bragg grating, and the spectrum of the laser output is seen to fall into three discrete stability regimes as measured by the side-mode suppression ratio.

Design, fabrication, and optimization of quantum cascade laser cavities and spectroscopy of the intersubband gain

NASA Astrophysics Data System (ADS)

Dirisu, Afusat Olayinka

Quantum Cascade (QC) lasers are intersubband light sources operating in the wavelength range of ˜ 3 to 300 mum and are used in applications such as sensing (environmental, biological, and hazardous chemical), infrared countermeasures, and free-space infrared communications. The mid-infrared range (i.e. lambda ˜ 3-30 mum) is of particular importance in sensing because of the strong interaction of laser radiation with various chemical species, while in free space communications the atmospheric windows of 3-5 mum and 8-12 mum are highly desirable for low loss transmission. Some of the requirements of these applications include, (1) high output power for improved sensitivity; (2) high operating temperatures for compact and cost-effective systems; (3) wide tunability; (4) single mode operation for high selectivity. In the past, available mid-infrared sources, such as the lead-salt and solid-state lasers, were bulky, expensive, or emit low output power. In recent years, QC lasers have been explored as cost-effective and compact sources because of their potential to satisfy and exceed all the above requirements. Also, the ultrafast carrier lifetimes of intersubband transitions in QC lasers are promising for high bandwidth free-space infrared communication. This thesis was focused on the improvement of QC lasers through the design and optimization of the laser cavity and characterization of the laser gain medium. The optimization of the laser cavity included, (1) the design and fabrication of high reflection Bragg gratings and subwavelength antireflection gratings, by focused ion beam milling, to achieve tunable, single mode and high power QC lasers, and (2) modeling of slab-coupled optical waveguide QC lasers for high brightness output beams. The characterization of the QC laser gain medium was carried out using the single-pass transmission experiment, a sensitive measurement technique, for probing the intersubband transitions and the electron distribution of QC lasers under different temperatures and applied bias conditions, unlike typical infrared measurement techniques that are restricted to non-functional devices. With the single-pass technique, basic understanding of the physics behind the workings of the QC laser gain can be achieved, which is invaluable in the design of QC lasers with high output power and high operating temperatures.

Dynamic Response during PEM Fuel Cell Loading-up

PubMed Central

Pei, Pucheng; Yuan, Xing; Gou, Jun; Li, Pengcheng

2009-01-01

A study on the effects of controlling and operating parameters for a Proton Exchange Membrane (PEM) fuel cell on the dynamic phenomena during the loading-up process is presented. The effect of the four parameters of load-up amplitudes and rates, operating pressures and current levels on gas supply or even starvation in the flow field is analyzed based accordingly on the transient characteristics of current output and voltage. Experiments are carried out in a single fuel cell with an active area of 285 cm2. The results show that increasing the loading-up amplitude can inevitably increase the possibility of gas starvation in channels when a constant flow rate has been set for the cathode; With a higher operating pressure, the dynamic performance will be improved and gas starvations can be relieved. The transient gas supply in the flow channel during two loading-up mode has also been discussed. The experimental results will be helpful for optimizing the control and operation strategies for PEM fuel cells in vehicles.

Demonstration of reconfigurable joint orbital angular momentum mode and space switching

PubMed Central

Liu, Jun; Wang, Jian

2016-01-01

We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications. PMID:27869133

Demonstration of reconfigurable joint orbital angular momentum mode and space switching

NASA Astrophysics Data System (ADS)

Liu, Jun; Wang, Jian

2016-11-01

We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications.

Demonstration of reconfigurable joint orbital angular momentum mode and space switching.

PubMed

Liu, Jun; Wang, Jian

2016-11-21

We propose and demonstrate space-selective switch functions employing orbital angular momentum (OAM) modes in the space domain for switching network. One is the switching among different OAM modes having different spatial phase structures, called OAM mode switching. The other is the switching among different space locations, called space switching. The switching operation mechanism relies on linear optics. Reconfigurable 4 × 4 OAM mode switching, space switching, and joint OAM mode and space switching fabric using a single spatial light modulator (SLM) are all demonstrated in the experiment. In addition, the presented OAM-incorporated space-selective switch might be further extended to N × N joint OAM mode and space switching with fast response, scalability, cascading ability and compability to facilitate robust switching applications.

Fiber-chip edge coupler with large mode size for silicon photonic wire waveguides.

PubMed

Papes, Martin; Cheben, Pavel; Benedikovic, Daniel; Schmid, Jens H; Pond, James; Halir, Robert; Ortega-Moñux, Alejandro; Wangüemert-Pérez, Gonzalo; Ye, Winnie N; Xu, Dan-Xia; Janz, Siegfried; Dado, Milan; Vašinek, Vladimír

2016-03-07

Fiber-chip edge couplers are extensively used in integrated optics for coupling of light between planar waveguide circuits and optical fibers. In this work, we report on a new fiber-chip edge coupler concept with large mode size for silicon photonic wire waveguides. The coupler allows direct coupling with conventional cleaved optical fibers with large mode size while circumventing the need for lensed fibers. The coupler is designed for 220 nm silicon-on-insulator (SOI) platform. It exhibits an overall coupling efficiency exceeding 90%, as independently confirmed by 3D Finite-Difference Time-Domain (FDTD) and fully vectorial 3D Eigenmode Expansion (EME) calculations. We present two specific coupler designs, namely for a high numerical aperture single mode optical fiber with 6 µm mode field diameter (MFD) and a standard SMF-28 fiber with 10.4 µm MFD. An important advantage of our coupler concept is the ability to expand the mode at the chip edge without leading to high substrate leakage losses through buried oxide (BOX), which in our design is set to 3 µm. This remarkable feature is achieved by implementing in the SiO 2 upper cladding thin high-index Si 3 N 4 layers. The Si 3 N 4 layers increase the effective refractive index of the upper cladding near the facet. The index is controlled along the taper by subwavelength refractive index engineering to facilitate adiabatic mode transformation to the silicon wire waveguide while the Si-wire waveguide is inversely tapered along the coupler. The mode overlap optimization at the chip facet is carried out with a full vectorial mode solver. The mode transformation along the coupler is studied using 3D-FDTD simulations and with fully-vectorial 3D-EME calculations. The couplers are optimized for operating with transverse electric (TE) polarization and the operating wavelength is centered at 1.55 µm.

Ada 9X Project Revision Request Report. Supplement 1

DTIC Science & Technology

1990-01-01

Non-portable use of operating system primitives or of Ada run time system internals. POSSIBLE SOLUTIONS: Mandate that compilers recognize tasks that...complex than a simple operating system file, the compiler vendor must provide routines to manipulate it (create, copy, move etc .) as a single entity... system , to support fault tolerance, load sharing, change of system operating mode etc . It is highly desirable that such important software be written in

High-power 0.87-micron channel substrate planar lasers for spaceborne communications

NASA Technical Reports Server (NTRS)

Connolly, J. C.; Stewart, T. R.; Gilbert, D. B.; Slavin, S. E.; Carlin, D. B.

1988-01-01

High-power single-mode channeled-substrate planar AlGaAs diode lasers are being developed for reliable high-power operation for use as sources in spaceborne optical communication systems. The CSP laser structure has been optimized for operation at an emission wavelength of 870 nm. Such devices have exhibited output powers in excess of 80 mW CW at an operating temperature of 80 C.

Single laser beam of spatial coherence from an array of GaAs lasers - Free-running mode

NASA Technical Reports Server (NTRS)

Philipp-Rutz, E. M.

1975-01-01

Spatially coherent radiation from a monolithic array of three GaAs lasers in a free-running mode is reported. The lasers, with their mirror faces antireflection coated, are operated in an external optical cavity built of spherical lenses and plane mirrors. The spatially coherent-beam formation makes use of the Fourier-transformation property of the internal lenses. Transverse mode control is accomplished by a spatial filter. The optical cavity is similar to that used for the phase-controlled mode of spatially coherent-beam formation; only the spatial filters are different. In the far field (when restored by an external lens), the intensities of the lasers in the array are concentrated in a single laser beam of spatial coherence, without any grating lobes. The far-field distribution of the laser array in the free-running mode differs significantly from the interference pattern of the phase-controlled mode. The modulation characteristics of the optical waveforms of the two modes are also quite different because modulation is related to the interaction of the spatial filter with the longitudinal modes of the laser array within the optical cavity. The modulation of the optical waveform of the free-running mode is nonperiodic, confirming that the fluctuations of the optical fields of the lasers are random.

Impurity bound states in mesoscopic topological superconducting loops

NASA Astrophysics Data System (ADS)

Jin, Yan-Yan; Zha, Guo-Qiao; Zhou, Shi-Ping

2018-06-01

We study numerically the effect induced by magnetic impurities in topological s-wave superconducting loops with spin-orbit interaction based on spin-generalized Bogoliubov-de Gennes equations. In the case of a single magnetic impurity, it is found that the midgap bound states can cross the Fermi level at an appropriate impurity strength and the circulating spin current jumps at the crossing point. The evolution of the zero-energy mode can be effectively tuned by the located site of a single magnetic impurity. For the effect of many magnetic impurities, two independent midway or edge impurities cannot lead to the overlap of zero modes. The multiple zero-energy modes can be effectively realized by embedding a single Josephson junction with impurity scattering into the system, and the spin current displays oscillatory feature with increasing the layer thickness.

Carbon nanotube mode-locked vertical external-cavity surface-emitting laser

NASA Astrophysics Data System (ADS)

Seger, K.; Meiser, N.; Choi, S. Y.; Jung, B. H.; Yeom, D.-I.; Rotermund, F.; Okhotnikov, O.; Laurell, F.; Pasiskevicius, V.

2014-03-01

Mode-locking an optically pumped semiconductor disk laser has been demonstrated using low-loss saturable absorption containing a mixture of single-walled carbon nanotubes in PMM polymer. The modulator was fabricated by a simple spin-coating technique on fused silica substrate and was operating in transmission. Stable passive fundamental modelocking was obtained at a repetition rate of 613 MHz with a pulse length of 1.23 ps. The mode-locked semiconductor disk laser in a compact geometry delivered a maximum average output power of 136 mW at 1074 nm.

Magnetic-Field Control Of Tunnel-Coupling In Strongly Confined One-Dimensional Electron Systems

NASA Astrophysics Data System (ADS)

Fischer, S. F.; Apetrii, G.; Kunze, U.; Schuh, D.; Abstreiter, G.

2007-04-01

One-dimensional (1D) ballistic electron transport is studied through stacked 1D quantum conductors separated by a thin tunneling barrier. The 1D electron systems of large 1D subband spacings (more than 10 meV) allow single mode operation. Degeneracies of 1D subbands of equal lateral mode index are lifted by the formation of symmetric and antisymmetric states and are depicted by anti-crossings of transconductance maxima. We observe a mode-dependent turnover from level anti-crossings to crossings in longitudinal magnetic fields.

Ultrafast Narrow Band Modulation of VCSELs

NASA Technical Reports Server (NTRS)

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

2002-01-01

Multimode beating was greatly enhanced by taking output from part (e.g., half) of the output facet. Simpler sources of microwaves and millimeter waves of various frequencies were generated by varying the VCSEL diameter in a single multimode VCSEL our coupling of a few VCSELs. Breathing frequency in multi-mode operations affects modulation response and bandwidth. Optimizing RO frequency and mode beating frequency could potentially expand bandwidths suitable for wide band digital communications.

Self-mixing detection of backscattered radiation in a single-mode erbium fibre laser for Doppler spectroscopy and velocity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmitriev, A K; Konovalov, A N; Ul'yanov, V A

2014-04-28

We report an experimental study of the self-mixing effect in a single-mode multifrequency erbium fibre laser when radiation backscattered from an external moving object arrives at its cavity. To eliminate resulting chaotic pulsations in the laser, we have proposed a technique for suppressing backscattered radiation through the use of multimode fibre for radiation delivery. The multifrequency operation of the laser has been shown to lead to strong fluctuations of the amplitude of the Doppler signal and a nonmonotonic variation of the amplitude with distance to the scattering object. In spite of these features, the self-mixing signal was detected with amore » high signal-to-noise ratio (above 10{sup 2}) when the radiation was scattered by a rotating disc, and the Doppler frequency shift, evaluated as the centroid of its spectrum, had high stability (0.15%) and linearity relative to the rotation rate. We conclude that the self-mixing effect in this type of fibre laser can be used for measuring the velocity of scattering objects and in Doppler spectroscopy for monitoring the laser evaporation of materials and biological tissues. (control of laser radiation parameters)« less

Performance of the Dual BAK-12 Aircraft Arresting System with Modular Hardware with Deadloads and Aircraft

DTIC Science & Technology

1976-04-15

System, Dual-System, Single-Mode, and Dual-Mode configurations. Tests were conducted to determine the feasibility of incorporating modular hardware on a...and 11-1/2 feet OFF-CENTER with the BAK-12 configured in the Single and Dual Mode to determine the effect of engaging the aircraft arresting-hook...cable OFF-CENTER. 90,000- pound deadload arrestments were conducted ON-CENTER in the Dual Mode to determine system performance with high-energy

Quantum entanglement for systems of identical bosons: II. Spin squeezing and other entanglement tests

NASA Astrophysics Data System (ADS)

Dalton, B. J.; Goold, J.; Garraway, B. M.; Reid, M. D.

2017-02-01

These two accompanying papers are concerned with entanglement for systems of identical massive bosons and the relationship to spin squeezing and other quantum correlation effects. The main focus is on two mode entanglement, but multi-mode entanglement is also considered. The bosons may be atoms or molecules as in cold quantum gases. The previous paper I dealt with the general features of quantum entanglement and its specific definition in the case of systems of identical bosons. Entanglement is a property shared between two (or more) quantum sub-systems. In defining entanglement for systems of identical massive particles, it was concluded that the single particle states or modes are the most appropriate choice for sub-systems that are distinguishable, that the general quantum states must comply both with the symmetrization principle and the super-selection rules (SSR) that forbid quantum superpositions of states with differing total particle number (global SSR compliance). Further, it was concluded that (in the separable states) quantum superpositions of sub-system states with differing sub-system particle number (local SSR compliance) also do not occur. The present paper II determines possible tests for entanglement based on the treatment of entanglement set out in paper I. Several inequalities involving variances and mean values of operators have been previously proposed as tests for entanglement between two sub-systems. These inequalities generally involve mode annihilation and creation operators and include the inequalities that define spin squeezing. In this paper, spin squeezing criteria for two mode systems are examined, and spin squeezing is also considered for principle spin operator components where the covariance matrix is diagonal. The proof, which is based on our SSR compliant approach shows that the presence of spin squeezing in any one of the spin components requires entanglement of the relevant pair of modes. A simple Bloch vector test for entanglement is also derived. Thus we show that spin squeezing becomes a rigorous test for entanglement in a system of massive bosons, when viewed as a test for entanglement between two modes. In addition, other previously proposed tests for entanglement involving spin operators are considered, including those based on the sum of the variances for two spin components. All of the tests are still valid when the present concept of entanglement based on the symmetrization and SSR criteria is applied. These tests also apply in cases of multi-mode entanglement, though with restrictions in the case of sub-systems each consisting of pairs of modes. Tests involving quantum correlation functions are also considered and for global SSR compliant states these are shown to be equivalent to tests involving spin operators. A new weak correlation test is derived for entanglement based on local SSR compliance for separable states, complementing the stronger correlation test obtained previously when this is ignored. The Bloch vector test is equivalent to one case of this weak correlation test. Quadrature squeezing for single modes is also examined but not found to yield a useful entanglement test, whereas two mode quadrature squeezing proves to be a valid entanglement test, though not as useful as the Bloch vector test. The various entanglement tests are considered for well-known entangled states, such as binomial states, relative phase eigenstates and NOON states—sometimes the new tests are satisfied while than those obtained in other papers are not. The present paper II then outlines the theory for a simple two mode interferometer showing that such an interferometer can be used to measure the mean values and covariance matrix for the spin operators involved in entanglement tests for the two mode bosonic system. The treatment is also generalized to cover multi-mode interferometry. The interferometer involves a pulsed classical field characterized by a phase variable and an area variable defined by the time integral of the field amplitude, and leads to a coupling between the two modes. For simplicity the center frequency was chosen to be resonant with the inter-mode transition frequency. Measuring the mean and variance of the population difference between the two modes for the output state of the interferometer for various choices of interferometer variables is shown to enable the mean values and covariance matrix for the spin operators for the input quantum state of the two mode system to be determined. The paper concludes with a discussion of several key experimental papers on spin squeezing.

Opto-Electronic Oscillator and its Applications

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1996-01-01

We present the theoretical and experimental results of a new class of microwave oscillators called opto-electronic oscillators (OEO). We discuss techniques of achieving high stability single mode operation and demonstrate the applications of OEO in photonic communication systems.

The design of radiation-hardened ICs for space - A compendium of approaches

NASA Technical Reports Server (NTRS)

Kerns, Sherra E.; Shafer, B. D; Rockett, L. R., Jr.; Pridmore, J. S.; Berndt, D. F.

1988-01-01

Several technologies, including bulk and epi CMOS, CMOS/SOI-SOS (silicon-on-insulator-silicon-on-sapphire), CML (current-mode logic), ECL (emitter-coupled logic), analog bipolar (JI, single-poly DI, and SOI) and GaAs E/D (enhancement/depletion) heterojunction MESFET, are discussed. The discussion includes the direct effects of space radiation on microelectronic materials and devices, how these effects are evidenced in circuit and device design parameter variations, the particular effects of most significance to each functional class of circuit, specific techniques for hardening high-speed circuits, design examples for integrated systems, including operational amplifiers and A/D (analog/digital) converters, and the computer simulation of radiation effects on microelectronic ISs.

Effects of underwater turbulence on laser beam propagation and coupling into single-mode optical fiber.

PubMed

Hanson, Frank; Lasher, Mark

2010-06-01

We characterize and compare the effects of turbulence on underwater laser propagation with theory. Measurements of the coupling efficiency of the focused beam into a single-mode fiber are reported. A simple tip-tilt control system, based on the position of the image centroid in the focal plane, was shown to maintain good coupling efficiency for a beam radius equal to the transverse coherence length, r(0). These results are relevant to high bandwidth communication technology that requires good spatial mode quality.

Failure modes of vacuum plasma spray tungsten coating created on carbon fibre composites under thermal loads

NASA Astrophysics Data System (ADS)

Hirai, T.; Bekris, N.; Coad, J. P.; Grisolia, C.; Linke, J.; Maier, H.; Matthews, G. F.; Philipps, V.; Wessel, E.

2009-07-01

Vacuum plasma spray tungsten (VPS-W) coating created on a carbon fibre reinforced composite (CFC) was tested under two thermal load schemes in the electron beam facility to examine the operation limits and failure modes. In cyclic ELM-like short transient thermal loads, the VPS-W coating was destroyed sub-layer by sub-layer at 0.33 GW/m 2 for 1 ms pulse duration. At longer single pulses, simulating steady-state thermal loads, the coating was destroyed at surface temperatures above 2700 °C by melting of the rhenium containing multilayer at the interface between VPS-W and CFC. The operation limits and failure modes of the VPS-W coating in the thermal load schemes are discussed in detail.

Design and performance of single photon APD focal plane arrays for 3-D LADAR imaging

NASA Astrophysics Data System (ADS)

Itzler, Mark A.; Entwistle, Mark; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir; Zalud, Peter F.; Senko, Tom; Tower, John; Ferraro, Joseph

2010-08-01

×We describe the design, fabrication, and performance of focal plane arrays (FPAs) for use in 3-D LADAR imaging applications requiring single photon sensitivity. These 32 × 32 FPAs provide high-efficiency single photon sensitivity for three-dimensional LADAR imaging applications at 1064 nm. Our GmAPD arrays are designed using a planarpassivated avalanche photodiode device platform with buried p-n junctions that has demonstrated excellent performance uniformity, operational stability, and long-term reliability. The core of the FPA is a chip stack formed by hybridizing the GmAPD photodiode array to a custom CMOS read-out integrated circuit (ROIC) and attaching a precision-aligned GaP microlens array (MLA) to the back-illuminated detector array. Each ROIC pixel includes an active quenching circuit governing Geiger-mode operation of the corresponding avalanche photodiode pixel as well as a pseudo-random counter to capture per-pixel time-of-flight timestamps in each frame. The FPA has been designed to operate at frame rates as high as 186 kHz for 2 μs range gates. Effective single photon detection efficiencies as high as 40% (including all optical transmission and MLA losses) are achieved for dark count rates below 20 kHz. For these planar-geometry diffused-junction GmAPDs, isolation trenches are used to reduce crosstalk due to hot carrier luminescence effects during avalanche events, and we present details of the crosstalk performance for different operating conditions. Direct measurement of temporal probability distribution functions due to cumulative timing uncertainties of the GmAPDs and ROIC circuitry has demonstrated a FWHM timing jitter as low as 265 ps (standard deviation is ~100 ps).

20 Gbit/s error free transmission with ~850 nm GaAs-based vertical cavity surface emitting lasers (VCSELs) containing InAs-GaAs submonolayer quantum dot insertions

NASA Astrophysics Data System (ADS)

Lott, J. A.; Shchukin, V. A.; Ledentsov, N. N.; Stinz, A.; Hopfer, F.; Mutig, A.; Fiol, G.; Bimberg, D.; Blokhin, S. A.; Karachinsky, L. Y.; Novikov, I. I.; Maximov, M. V.; Zakharov, N. D.; Werner, P.

2009-02-01

We report on the modeling, epitaxial growth, fabrication, and characterization of 830-845 nm vertical cavity surface emitting lasers (VCSELs) that employ InAs-GaAs quantum dot (QD) gain elements. The GaAs-based VCSELs are essentially conventional in design, grown by solid-source molecular beam epitaxy, and include top and bottom gradedheterointerface AlGaAs distributed Bragg reflectors, a single selectively-oxidized AlAs waveguiding/current funneling aperture layer, and a quasi-antiwaveguiding microcavity. The active region consists of three sheets of InAs-GaAs submonolayer insertions separated by AlGaAs matrix layers. Compared to QWs the InAs-GaAs insertions are expected to offer higher exciton-dominated modal gain and improved carrier capture and retention, thus resulting in superior temperature stability and resilience to degradation caused by operating at the larger switching currents commonly employed to increase the data rates of modern optical communication systems. We investigate the robustness and temperature performance of our QD VCSEL design by fabricating prototype devices in a high-frequency ground-sourceground contact pad configuration suitable for on-wafer probing. Arrays of VCSELs are produced with precise variations in top mesa diameter from 24 to 36 μm and oxide aperture diameter from 1 to 12 μm resulting in VCSELs that operate in full single-mode, single-mode to multi-mode, and full multi-mode regimes. The single-mode QD VCSELs have room temperature threshold currents below 0.5 mA and peak output powers near 1 mW, whereas the corresponding values for full multi-mode devices range from about 0.5 to 1.5 mA and 2.5 to 5 mW. At 20°C we observe optical transmission at 20 Gb/s through 150 m of OM3 fiber with a bit error ratio better than 10-12, thus demonstrating the great potential of our QD VCSELs for applications in next-generation short-distance optical data communications and interconnect systems.

Optical fiber tip interferometer gas pressure sensor based on anti-resonant reflecting guidance mechanism

NASA Astrophysics Data System (ADS)

Yang, Y. B.; Wang, D. N.; Xu, Ben; Wang, Z. K.

2018-05-01

We propose and demonstrate a gas pressure sensor based on an anti-resonant reflecting guidance (ARRG) mechanism in quartz capillary tube with an open cavity. The device is simple in fabrication by only fusion splicing a segment of capillary tube with single mode fiber. It has compact size, robust structure, convenient mode of operation, and high sensitivity of 4.278 nm/MPa. Moreover, as two Faby-Perot cavities exist in the device, which create the interference spectrum with several distinct resonance dips, a simultaneous gas pressure and temperature detection can be readily achieved by tracing two dip wavelengths. The error in the measurement due to the choice of different resonant dips can be effectively reduced by using the Fourier band pass filtering method.

Numerical Simulation of Single-anode and Double-anode Magnetron Injection Guns for 127.5 GHz 1 MW Gyrotron

NASA Astrophysics Data System (ADS)

Singh, Udaybir; Kumar, Nitin; Kumar, Anil; Purohit, Laxmi Prasad; Sinha, Ashok Kumar

2011-07-01

This paper presents the design of two types of magnetron injection guns (MIG's) for 1 MW, 127.5 GHz gyrotron. TE24,8 mode has been chosen as the operating mode. In-house developed code MIGSYN has been used to estimate the initial gun parameters. The electron trajectory tracing program EGUN and in-house developed code MIGANS have been used to optimize the single-anode and the double-anode design for 80 kV, 40 A MIG. The parametric analysis of MIG has also been presented. The advantages and the disadvantages of each kind of configuration have been critically examined.

High-power, single-longitudinal-mode terahertz-wave generation pumped by a microchip Nd:YAG laser [Invited].

PubMed

Hayashi, Shin'ichiro; Nawata, Koji; Sakai, Hiroshi; Taira, Takunori; Minamide, Hiroaki; Kawase, Kodo

2012-01-30

We report on the development of a high-peak-power, single-longitudinal-mode and tunable injection-seeded terahertz-wave parametric generator using MgO:LiNbO3, which operates at room temperature. The high peak power (> 120 W) is enough to allow easy detection by commercial and calibrated pyroelectric detectors, and the spectral resolution (< 10 GHz) is the Fourier transform limit of the sub-nanosecond terahertz-wave pulse. The tunability (1.2-2.8 THz) and the small footprint size (A3 paper, 29.7 × 42 cm) are suitable for a variety of applications.

Spectrally tailored supercontinuum generation from single-mode-fiber amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hao, Qiang; Guo, Zhengru; Zhang, Qingshan

Spectral filtering of an all-normal-dispersion Yb-doped fiber laser was demonstrated effective for broadband supercontinuum generation in the picosecond time region. The picosecond pump pulses were tailored in spectrum with 1 nm band-pass filter installed between two single-mode fiber amplifiers. By tuning the spectral filter around 1028 nm, four-wave mixing was initiated in a photonic crystal fiber spliced with single-mode fiber, as manifested by the simultaneous generation of Stokes wave at 1076 nm and anti-Stokes wave at 984 nm. Four-wave mixing took place in cascade with the influence of stimulated Raman scattering and eventually extended the output spectrum more than 900 nm of 10 dB bandwidth.more » This technique allows smooth octave supercontinuum generation by using simple single-mode fiber amplifiers rather than complicated multistage large-mode-area fiber amplifiers.« less

Low-Loss Coupling of Quantum Cascade Lasers into Hollow-Core Waveguides with Single-Mode Output in the 3.7–7.6 μm Spectral Range

PubMed Central

Patimisco, Pietro; Sampaolo, Angelo; Mihai, Laura; Giglio, Marilena; Kriesel, Jason; Sporea, Dan; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

2016-01-01

We demonstrated low-loss and single-mode laser beam delivery through hollow-core waveguides (HCWs) operating in the 3.7–7.6 μm spectral range. The employed HCWs have a circular cross section with a bore diameter of 200 μm and metallic/dielectric internal coatings deposited inside a glass capillary tube. The internal coatings have been produced to enhance the spectral response of the HCWs in the range 3.5–12 µm. We demonstrated Gaussian-like outputs throughout the 4.5–7.6 µm spectral range. A quasi single-mode output beam with only small beam distortions was achieved when the wavelength was reduced to 3.7 μm. With a 15-cm-long HCW and optimized coupling conditions, we measured coupling efficiencies of >88% and transmission losses of <1 dB in the investigated infrared spectral range. PMID:27089343

New Circuit QED system based on Triple-leg Stripline Resonator.

NASA Astrophysics Data System (ADS)

Kim, Dongmin; Moon, Kyungsun

Conventional circuit QED system consists of a qubit located inside a linear stripline resonator, which has successfully demonstrated a strong coupling between a single photon and a qubit. Here we present a new circuit QED system, where the qubit is coupled to triple-leg stripline resonator (TSR). We have shown that TSR supports two-fold degenerate photon modes among others. By coupling them to a single qubit, we have obtained the dressed states of a coupled system of a single qubit and two-fold degenerate photon modes. By locating two qubits at two legs of TSR, we have studied a potential two-bit gate operation (e.g., CNOT gate) of the system. We will discuss the main advantage of utilizing two-fold degenerate photon modes This work is partially supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2016R1D1A1B01013756).

Computer simulation of a single pilot flying a modern high-performance helicopter

NASA Technical Reports Server (NTRS)

Zipf, Mark E.; Vogt, William G.; Mickle, Marlin H.; Hoelzeman, Ronald G.; Kai, Fei; Mihaloew, James R.

1988-01-01

Presented is a computer simulation of a human response pilot model able to execute operational flight maneuvers and vehicle stabilization of a modern high-performance helicopter. Low-order, single-variable, human response mechanisms, integrated to form a multivariable pilot structure, provide a comprehensive operational control over the vehicle. Evaluations of the integrated pilot were performed by direct insertion into a nonlinear, total-force simulation environment provided by NASA Lewis. Comparisons between the integrated pilot structure and single-variable pilot mechanisms are presented. Static and dynamically alterable configurations of the pilot structure are introduced to simulate pilot activities during vehicle maneuvers. These configurations, in conjunction with higher level, decision-making processes, are considered for use where guidance and navigational procedures, operational mode transfers, and resource sharing are required.

1.6 μm dissipative soliton fiber laser mode-locked by cesium lead halide perovskite quantum dots.

PubMed

Liu, Bang; Gao, Lei; Cheng, Wei Wei; Tang, Xiao Sheng; Gao, Chao; Cao, Yu Long; Li, Yu Jia; Zhu, Tao

2018-03-19

We demonstrate a stable, picosecond fiber laser mode-locked by cesium lead halide perovskite quantum dots (CsPbBr 3 -QDs). The saturable absorber is produced by depositing the CsPbBr3-QDs nanocrystals onto the endface of a fiber ferrule through light pressure. A balanced two-detector measurement shows that it has a modulation depth of 2.5% and a saturation power of 17.29 MW/cm 2 . After incorporating the fabricated device into an Er 3+ -doped fiber ring cavity with a net normal dispersion of 0.238 ps 2 , we obtain stable dissipative soliton with a pulse duration of 14.4 ps and a center wavelength at 1600 nm together with an edge-to-dege bandwidth of 4.5 nm. The linear chirped phase can be compensated by 25 m single mode fiber, resulting into a compressed pulse duration of 1.046 ps. This experimental works proves that such CsPbBr3-QDs materials are effective choice for ultrafast laser operating with devious mode-locking states.

Measurement of curvature and temperature using multimode interference devices

NASA Astrophysics Data System (ADS)

Guzman-Sepulveda, J. R.; Aguilar-Soto, J. G.; Torres-Cisneros, M.; Ibarra-Manzano, O. G.; May-Arrioja, D. A.

2011-09-01

In this paper we propose the fabrication, implementation, and testing of a novel fiber optic sensor based on Multimode Interference (MMI) effects for independent measurement of curvature and temperature. The development of fiber based MMI devices is relatively new and since they exhibit a band-pass filter response they can be used in different applications. The operating mechanism of our sensor is based on the self-imaging phenomena that occur in multimode fibers (MMF), which is related to the interference of the propagating modes and their accumulated phase. We demonstrate that the peak wavelength shifts with temperature variations as a result of changes in the accumulated phase through thermo-optics effects, while the intensity of the peak wavelength is reduced as the curvature increases since we start to loss higher order modes. In this way both measurements are obtained independently with a single fiber device. Compared to other fiber-optic sensors, our sensor features an extremely simple structure and fabrication process, and hence cost effectiveness.

Electromechanical quantum simulators

NASA Astrophysics Data System (ADS)

Tacchino, F.; Chiesa, A.; LaHaye, M. D.; Carretta, S.; Gerace, D.

2018-06-01

Digital quantum simulators are among the most appealing applications of a quantum computer. Here we propose a universal, scalable, and integrated quantum computing platform based on tunable nonlinear electromechanical nano-oscillators. It is shown that very high operational fidelities for single- and two-qubits gates can be achieved in a minimal architecture, where qubits are encoded in the anharmonic vibrational modes of mechanical nanoresonators, whose effective coupling is mediated by virtual fluctuations of an intermediate superconducting artificial atom. An effective scheme to induce large single-phonon nonlinearities in nanoelectromechanical devices is explicitly discussed, thus opening the route to experimental investigation in this direction. Finally, we explicitly show the very high fidelities that can be reached for the digital quantum simulation of model Hamiltonians, by using realistic experimental parameters in state-of-the-art devices, and considering the transverse field Ising model as a paradigmatic example.

Microcavity morphology optimization

NASA Astrophysics Data System (ADS)

Ferdous, Fahmida; Demchenko, Alena A.; Vyatchanin, Sergey P.; Matsko, Andrey B.; Maleki, Lute

2014-09-01

High spectral mode density of conventional optical cavities is detrimental to the generation of broad optical frequency combs and to other linear and nonlinear applications. In this work we optimize the morphology of high-Q whispering gallery (WG) and Fabry-Perot (FP) cavities and find a set of parameters that allows treating them, essentially, as single-mode structures, thus removing limitations associated with a high density of cavity mode spectra. We show that both single-mode WGs and single-mode FP cavities have similar physical properties, in spite of their different loss mechanisms. The morphology optimization does not lead to a reduction of quality factors of modes belonging to the basic family. We study the parameter space numerically and find the region where the highest possible Q factor of the cavity modes can be realized while just having a single bound state in the cavity. The value of the Q factor is comparable with that achieved in conventional cavities. The proposed cavity structures will be beneficial for generation of octave spanning coherent frequency combs and will prevent undesirable effects of parametric instability in laser gravitational wave detectors.

INTEGRATED AND FIBER OPTICS: Calculation and measurement of waveguide characteristics of single-mode fiber waveguides with a depressed cladding

NASA Astrophysics Data System (ADS)

Belov, A. V.; Kurkov, Andrei S.; Chikolini, A. V.

1989-02-01

A method was developed for calculating the effective cutoff length, the size of a mode spot, and the chromatic dispersion over the profile of the refractive index (measured in the preform stage) of single-mode fiber waveguides with a depressed cladding. The results of such calculations are shown to agree with the results of measurements of these quantities.

Tunable microwave metasurfaces for high-performance operations: dispersion compensation and dynamical switch

PubMed Central

Xu, He-Xiu; Tang, Shiwei; Ma, Shaojie; Luo, Weijie; Cai, Tong; Sun, Shulin; He, Qiong; Zhou, Lei

2016-01-01

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices’ performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves. PMID:27901088

Tunable microwave metasurfaces for high-performance operations: dispersion compensation and dynamical switch.

PubMed

Xu, He-Xiu; Tang, Shiwei; Ma, Shaojie; Luo, Weijie; Cai, Tong; Sun, Shulin; He, Qiong; Zhou, Lei

2016-11-30

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices' performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves.

Tunable microwave metasurfaces for high-performance operations: dispersion compensation and dynamical switch

NASA Astrophysics Data System (ADS)

Xu, He-Xiu; Tang, Shiwei; Ma, Shaojie; Luo, Weijie; Cai, Tong; Sun, Shulin; He, Qiong; Zhou, Lei

2016-11-01

Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices’ performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode. We experimentally demonstrate two effects utilizing our scheme. First, we show that a tunable gradient metasurface exhibits single-mode high-efficiency operation within a wide frequency band, while its passive counterpart only works at a single frequency but exhibits deteriorated performances at other frequencies. Second, we demonstrate that the functionality of our metasurface can be dynamically switched from a specular reflector to a surface-wave convertor. Our approach paves the road to achieve dispersion-corrected and switchable manipulations of electromagnetic waves.

A comparative evaluation of effect of modern-curing lights and curing modes on conventional and novel-resin monomers

PubMed Central

Roy, Konda Karthik; Kumar, Kanumuru Pavan; John, Gijo; Sooraparaju, Sujatha Gopal; Nujella, Surya Kumari; Sowmya, Kyatham

2018-01-01

Aim: The aim of this study is to compare and to evaluate effect of curing light and curing modes on the nanohybrid composite resins with conventional Bis-GMA and novel tricyclodecane (TCD) monomers. Methodology: Two nanohybrid composites, IPS empress direct and charisma diamond were used in this study. Light-emitting diode (LED)-curing unit and quartz-tungsten-halogen (QTH)-curing unit which were operated into two different modes: continuous and soft start. Based on the composite resin, curing lights, and mode of curing used, the samples were divided into 8 groups. After polymerization, the samples were stored for 48 h in complete darkness at 37°C and 100% humidity. The Vickers hardness (VK) of the surface was determined with Vickers indenter by the application of 200 g for 15 s. Three VK readings were recorded for each sample surface both on top and bottom surfaces. For all the specimens, the three hardness values for each surface were averaged and reported as a single value. The mean VK and hardness ratio were calculated. The depth of cure was assessed based on the hardness ratio. Results: Comparison of mean hardness values and hardness ratios was done using ANOVA with post hoc Tukey's test. Conclusion: Both QTH- and LED-curing units had shown the adequate depth of cure. Soft-start-curing mode in both QTH- and LED-curing lights had effectively increased microhardness than the continuous mode of curing. TCD monomer had shown higher hardness values compared with conventional Bis-GMA-containing resin. PMID:29628651

Single-mode large-mode-area laser fiber with ultralow numerical aperture and high beam quality.

PubMed

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

2016-12-10

By using the chelate precursor doping technique, we report on an ytterbium-doped aluminophosphosilicate (APS) large-mode-area fiber with ultralow numerical aperture of 0.036 and effective fundamental mode area of ∼550  μm². With a bend diameter of 600 mm, the bending loss of fundamental mode LP₀₁ was measured to be <10^-3  dB/m, in agreement with the corresponding simulation results, while that of higher order mode LP₁₁ is >100  dB/m at 1080 nm. Measured in an all-fiber oscillator laser cavity, 592 W single-mode laser output was obtained at 1079.64 nm with high-beam quality M² of 1.12. The results indicate that the chelate precursor doping technique is a competitive method for ultralow numerical aperture fiber fabrication, which is very suitable for developing single-mode seed lasers for high power laser systems.

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

DOE PAGES

Tran, Huy Nam; Blancon, Jean-Christophe Robert; Arenal, Raul; ...

2017-05-08

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett.108, 117404 (2012)]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modesmore » permit to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.« less

Quantum interference effects on the intensity of the G modes in double-walled carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tran, Huy Nam; Blancon, Jean-Christophe Robert; Arenal, Raul

The effects of quantum interferences on the excitation dependence of the intensity of G modes have been investigated on single-walled carbon nanotubes [Duque et al., Phys. Rev. Lett.108, 117404 (2012)]. In this work, by combining optical absorption spectroscopy and Raman scattering on individual index identified double-walled carbon nanotubes, we examine the experimental excitation dependence of the intensity of longitudinal optical and transverse optical G modes of the constituent inner and outer single-walled carbon nanotubes. The observed striking dependencies are understood in terms of quantum interference effects. Considering such effects, the excitation dependence of the different components of the G modesmore » permit to unambiguously assign each of them as originating from the longitudinal or transverse G modes of inner and outer tubes.« less

Nd:YAG-laser-Q-switching with a photo-elastic modulator and applications

NASA Astrophysics Data System (ADS)

Bammer, F.; Petkovšek, R.; Dominguez, H.; Liedl, G.

2010-05-01

We present a rod-Nd:YAG-Laser, side-pumped with eight 50W-laser diode bars at 808nm, and Q-switched with a Single Crystal Photo-Elastic Modulator at 95.1 kHz. The latter is made of a z-cut LiNbO3-crystal, which is electrically y-excited on the mechanical resonance frequency of the x-longitudinal oscillation. With a voltage amplitude of 3 V the crystal shows a strong oscillation such that due to the photo-elastic effect a high polarization modulation is achieved, which, together with a polarizer, can be used as a simple optical switch. With this inside the laser resonator the average power is 47.8W in cw-mode and 45.5W in pulsed mode, with pulse peak powers of 4 kW and pulse widths of 100ns. This kind of operation is similar to cw-operation but offers due to the high peak powers different interaction physics with matter. The source is therefore suited for micro-welding of metals, LIDAR, rapid prototyping of plastics, marking/engraving/cutting of plastics, marking of glasses. In cases where high precision and a small heat affected zone are necessary this simple kind of pulsed operation may be advantageous, when compared to cw-operation.

Automated Cryocooler Monitor and Control System

NASA Technical Reports Server (NTRS)

Britcliffe, Michael J.; Hanscon, Theodore R.; Fowler, Larry E.

2011-01-01

A system was designed to automate cryogenically cooled low-noise amplifier systems used in the NASA Deep Space Network. It automates the entire operation of the system including cool-down, warm-up, and performance monitoring. The system is based on a single-board computer with custom software and hardware to monitor and control the cryogenic operation of the system. The system provides local display and control, and can be operated remotely via a Web interface. The system controller is based on a commercial single-board computer with onboard data acquisition capability. The commercial hardware includes a microprocessor, an LCD (liquid crystal display), seven LED (light emitting diode) displays, a seven-key keypad, an Ethernet interface, 40 digital I/O (input/output) ports, 11 A/D (analog to digital) inputs, four D/A (digital to analog) outputs, and an external relay board to control the high-current devices. The temperature sensors used are commercial silicon diode devices that provide a non-linear voltage output proportional to temperature. The devices are excited with a 10-microamp bias current. The system is capable of monitoring and displaying three temperatures. The vacuum sensors are commercial thermistor devices. The output of the sensors is a non-linear voltage proportional to vacuum pressure in the 1-Torr to 1-millitorr range. Two sensors are used. One measures the vacuum pressure in the cryocooler and the other the pressure at the input to the vacuum pump. The helium pressure sensor is a commercial device that provides a linear voltage output from 1 to 5 volts, corresponding to a gas pressure from 0 to 3.5 MPa (approx. = 500 psig). Control of the vacuum process is accomplished with a commercial electrically operated solenoid valve. A commercial motor starter is used to control the input power of the compressor. The warm-up heaters are commercial power resistors sized to provide the appropriate power for the thermal mass of the particular system, and typically provide 50 watts of heat. There are four basic operating modes. "Cool " mode commands the system to cool to normal operating temperature. "Heat " mode is used to warm the device to a set temperature near room temperature. "Pump " mode is a maintenance function that allows the vacuum system to be operated alone to remove accumulated contaminants from the vacuum area. In "Off " mode, no power is applied to the system.