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Sample records for 25-km single mode

  1. High-speed data encryption over 25 km of fiber by two-mode coherent-state quantum cryptography.

    PubMed

    Corndorf, Eric; Barbosa, Geraldo; Liang, Chuang; Yuen, Horace P; Kumar, Prem

    2003-11-01

    We demonstrate high-speed (250 Mbps) data encryption over 25 km of telecommunication fiber by use of coherent states. For the parameter values used in the experiment, the demonstration is secure against individual ciphertext-only eavesdropping attacks near the transmitter with ideal detection equipment. Whereas other quantum-cryptographic schemes require the use of fragile quantum states and ultrasensitive detection equipment, our protocol is loss tolerant, uses off-the-shelf components, and is optically amplifiable.

  2. Single-Mode VCSELs

    NASA Astrophysics Data System (ADS)

    Larsson, Anders; Gustavsson, Johan S.

    The only active transverse mode in a truly single-mode VCSEL is the fundamental mode with a near Gaussian field distribution. A single-mode VCSEL produces a light beam of higher spectral purity, higher degree of coherence and lower divergence than a multimode VCSEL and the beam can be more precisely shaped and focused to a smaller spot. Such beam properties are required in many applications. In this chapter, after discussing applications of single-mode VCSELs, we introduce the basics of fields and modes in VCSELs and review designs implemented for single-mode emission from VCSELs in different materials and at different wavelengths. This includes VCSELs that are inherently single-mode as well as inherently multimode VCSELs where higher-order modes are suppressed by mode selective gain or loss. In each case we present the current state-of-the-art and discuss pros and cons. At the end, a specific example with experimental results is provided and, as a summary, the most promising designs based on current technologies are identified.

  3. Single-Mode VISAR

    SciTech Connect

    Krauter, Kerry

    2007-11-28

    High energy-density physics (HEDP) experiments examine the properties of materials under extreme conditions. These experiments rely on the measurement of one or two velocities. These velocities are used to obtain Hugoniot relationships and thermodynamic equations of state. This methodology is referred to as 'velocimetry' and an instrument used to measure the shock wave is called a 'velocimeter' or a '(velocity) diagnostic'. The two most-widely used existing velocity diagnostics are; photonic Doppler velocimetry (PDV) and velocity interferometer system for any reflector (VISAR). PDV's advantages are a fast rise-time and ease of implementation but PDV has an upper velocity limit. Traditional implementations of VISAR have a rise time 10 times slower than PDV and are not easily implemented but are capable of measuring any velocity produced during HEDP experiments. This thesis describes a novel method of combining the positive attributes of PDV and VISAR into a more cost effective diagnostic called a Single-Mode VISAR (SMV). The new diagnostic will consist of PDV parts in a VISAR configuration. This configuration will enable the measurement of any velocity produced during shock physics experiments while the components used to build the diagnostic will give the diagnostic a fast rise time and make it easy to use. This thesis describes the process of building and testing the first single-mode VISAR. The tests include verifying the performance of the components and the diagnostic as a whole.

  4. Photon-bunching measurement after two 25-km-long optical fibers

    SciTech Connect

    Halder, M.; Tanzilli, S.; Riedmatten, H. de; Beveratos, A.; Zbinden, H.; Gisin, N.

    2005-04-01

    To show the feasibility of a long-distance partial Bell-state measurement, a Hong-Ou-Mandel experiment with coherent photons is reported. Pairs of degenerate photons at telecommunication wavelength are created by parametric down-conversion in a periodically poled lithium niobate waveguide. The photon pairs are separated in a beam splitter and transmitted via two fibers of 25 km. The wave packets are relatively delayed and recombined on a second beam splitter, forming a large Mach-Zehnder interferometer. Coincidence counts between the photons at the two output modes are registered. The main challenge consists in the trade-off between low count rates due to narrow filtering and length fluctuations of the 25-km-long arms during the measurement. For balanced paths a Hong-Ou-Mandel dip with a net visibility of 47.3% is observed, which is close to the maximal theoretical value of 50% developed here. This proves the practicability of a long-distance Bell-state measurement with two independent sources, as, e.g., required in an entanglement swapping configuration in the scale of tens of kilometers.

  5. Coherently wavelength injection-locking a 600-μm long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF.

    PubMed

    Li, Yi-Cheng; Chi, Yu-Chieh; Cheng, Min-Chi; Lu, I-Cheng; Chen, Jason; Lin, Gong-Ru

    2013-07-15

    The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (~1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from -9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6 × 10(-7) when pre-amplifying the OFDM data by 5 dB.

  6. Single mode levitation and translation

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Allen, James L. (Inventor)

    1988-01-01

    A single frequency resonance mode is applied by a transducer to acoustically levitate an object within a chamber. This process allows smooth movement of the object and suppression of unwanted levitation modes that would urge the object to a different levitation position. A plunger forms one end of the chamber, and the frequency changes as the plunger moves. Acoustic energy is applied to opposite sides of the chamber, with the acoustic energy on opposite sides being substantially 180 degrees out of phase.

  7. Single mode glass fiber welding

    NASA Technical Reports Server (NTRS)

    Nelson, M. D.; Fearnehough, H. T.; Goldstein, R.; Goss, W. C.

    1979-01-01

    The electric-arc welding of commercially available single-mode optical fiber has been demonstrated. A mean transmission of 92% and a maximum transmission of 98% are reported for welds of fiber waveguide of 4.5 microns core diameter.

  8. Spatial variability of arsenic in 6000 tube wells in a 25 km2 area of Bangladesh

    NASA Astrophysics Data System (ADS)

    van Geen, A.; Zheng, Y.; Versteeg, R.; Stute, M.; Horneman, A.; Dhar, R.; Steckler, M.; Gelman, A.; Small, C.; Ahsan, H.; Graziano, J. H.; Hussain, I.; Ahmed, K. M.

    2003-05-01

    Arsenic concentrations measured by graphite furnace atomic absorption range from < 5 to 900 μg/L in groundwater pumped from 6000 wells within a 25 km2 area of Bangladesh. The proportion of wells that exceed the Bangladesh standard for drinking water of 50 μg/L arsenic increases with depth from 25% between 8 and 10 m to 75% between 15 and 30 m, then declines gradually to less than 10% at 90 m. Some villages within the study area do not have a single well that meets the standard, while others have wells that are nearly all acceptable. In contrast to the distribution of arsenic in the 8-30 m depth range which does not follow any obvious geological feature, the arsenic content of groundwater associated with relatively oxic Pleistocene sand deposits appears to be consistently low. The depth of drilling necessary to reach these low-As aquifers ranges from 30 to 120 m depth within the study area.

  9. Single mode lasing in coupled nanowires

    NASA Astrophysics Data System (ADS)

    Xiao, Yao; Meng, Chao; Wu, Xiaoqin; Tong, Limin

    2011-07-01

    We demonstrate single mode lasing in coupled CdSe nanowires. By coupling two 420 nm diameter CdSe nanowires to form an X-structure cavity, single-mode lasing emission around 734.3 nm is obtained with line width of 0.11 nm and lasing threshold of about 120 μJ/cm2. Mode selection in the lasing nanowire is realized via Vernier effect in the coupled cavities. Our results suggest a simple approach to single-mode nanowire lasers.

  10. TO-56-can packaged colorless WRC-FPLD for QAM OFDM transmission at 42 Gbit/s over 25-km SMF.

    PubMed

    Cheng, Min-Chi; Chi, Yu-Chieh; Tsai, Cheng-Ting; Lin, Chung-Yu; Lin, Gong-Ru

    2015-08-24

    The weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) with colorless and channelized mode features is a new-class optical transmitter fulfilling the need of next-generation communications. By packaging the colorless WRC-FPLD transmitter with a 10-GHz transistor-outline-56-can (TO-56-can), the premier demonstration on directly modulated 42-Gbit/s/channel quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) transmission is demonstrated via wavelength injection-locking. Enlarging the injection level effectively up-shifts the relaxation oscillation peak and suppresses the relative intensity noise, which facilitates the TO-56-can packaged WRC-FPLD to improve its modulation throughput bandwidth to 9 GHz and enhance its signal-to-noise ratio to 22 dB. By pre-amplifying the directly modulated QAM-OFDM data with a total raw bit rate of 42 Gbit/s, the receiving bit-error-rate (BER) under back-to-back transmission can be reduced below the forward-error-correction (FEC) limited BER of 3.8 × 10(-3). Such a colorless WRC-FPLD enables the QAM-OFDM transmission over a 25-km long single-mode-fiber based metropolitan access network with its BER matching the FEC criterion at a receiving power of -2 dBm.

  11. Single-mode cylindrical graphene plasmon waveguide

    NASA Astrophysics Data System (ADS)

    Yang, Jianfeng; Yang, Jingjing; Huang, Ming

    2016-08-01

    A cylindrical graphene plasmon waveguide (CGPW) which consists of two rolled graphene ribbons, a dielectric core and a dielectric interlayer is proposed. An analytical model for the single-mode condition and cutoff frequency of high-order graphene surface plasmon (GSP) modes is presented and verified by finite element method (FEM) simulations. Single-mode operation region of CGPW is identified in the frequency-radius space. By varying the separation between two graphene sheets and the Fermi level of graphene, a large tunability of the mode behavior is also demonstrated. The proposed structure may provide a new freedom to manipulate GSPs, and would lead to novel applications in optics.

  12. Single mode pulsed dye laser oscillator

    DOEpatents

    Hackel, Richard P.

    1992-01-01

    A single mode pulsed dye laser oscillator is disclosed. The dye laser oscillator provides for improved power efficiency by reducing the physical dimensions of the overall laser cavity, which improves frequency selection capability.

  13. Single mode pulsed dye laser oscillator

    DOEpatents

    Hackel, R.P.

    1992-11-24

    A single mode pulsed dye laser oscillator is disclosed. The dye laser oscillator provides for improved power efficiency by reducing the physical dimensions of the overall laser cavity, which improves frequency selection capability. 6 figs.

  14. Disorder-induced single-mode transmission

    NASA Astrophysics Data System (ADS)

    Ruocco, Giancarlo; Abaie, Behnam; Schirmacher, Walter; Mafi, Arash; Leonetti, Marco

    2017-03-01

    Localized states trap waves propagating in a disordered potential and play a crucial role in Anderson localization, which is the absence of diffusion due to disorder. Some localized states are barely coupled with neighbours because of differences in wavelength or small spatial overlap, thus preventing energy leakage to the surroundings. This is the same degree of isolation found in the homogeneous core of a single-mode optical fibre. Here we show that localized states of a disordered optical fibre are single mode: the transmission channels possess a high degree of resilience to perturbation and invariance with respect to the launch conditions. Our experimental approach allows identification and characterization of the single-mode transmission channels in a disordered matrix, demonstrating low losses and densely packed single modes. These disordered and wavelength-sensitive channels may be exploited to de-multiplex different colours at different locations.

  15. Disorder-induced single-mode transmission

    PubMed Central

    Ruocco, Giancarlo; Abaie, Behnam; Schirmacher, Walter; Mafi, Arash; Leonetti, Marco

    2017-01-01

    Localized states trap waves propagating in a disordered potential and play a crucial role in Anderson localization, which is the absence of diffusion due to disorder. Some localized states are barely coupled with neighbours because of differences in wavelength or small spatial overlap, thus preventing energy leakage to the surroundings. This is the same degree of isolation found in the homogeneous core of a single-mode optical fibre. Here we show that localized states of a disordered optical fibre are single mode: the transmission channels possess a high degree of resilience to perturbation and invariance with respect to the launch conditions. Our experimental approach allows identification and characterization of the single-mode transmission channels in a disordered matrix, demonstrating low losses and densely packed single modes. These disordered and wavelength-sensitive channels may be exploited to de-multiplex different colours at different locations. PMID:28262763

  16. Extending single mode performance of all-solid large-mode-area single trench fiber.

    PubMed

    Jain, D; Jung, Y; Nunez-Velazquez, M; Sahu, J K

    2014-12-15

    We report a novel "single trench fiber" design for mode area scaling of the fundamental mode while offering effective single mode operation for a compact fiber laser device. This fiber design allows very high suppression of the higher order modes by offering high loss and power delocalization. It has the advantages of low cost and easy fabrication thanks to all solid fiber design, cylindrical symmetry, and higher refractive index of core as that of the cladding. A Yb-doped single trench fiber with a 40 µm core diameter has been fabricated from modified chemical vapor deposition process in conjunction with solution-doping offering an effective mode area of as large as ~1,000 µm(2) at 1,060 nm for the bend radius of 20 cm. Detailed characterizations confirm a robust single mode behavior of the fiber. Comparative analysis with other fiber designs shows significant performance enhancement of effective single mode operation suitable for fiber laser applications.

  17. Single Mode Lasing from Hybrid Hemispherical Microresonators

    PubMed Central

    Chen, Rui; Van Duong Ta; Sun, Han Dong

    2012-01-01

    Enormous attention has been paid to optical microresonators which hold a great promise for microlasers as well as fundamental studies in cavity quantum electrodynamics. Here we demonstrate a three-dimensional (3D) hybrid microresonator combining self-assembled hemispherical structure with a planar reflector. By incorporating dye molecules into the hemisphere, optically pumped lasing phenomenon is observed at room temperature. We have studied the lasing behaviors with different cavity sizes, and particularly single longitudinal mode lasing from hemispheres with diameter ∼15 μm is achieved. Detailed characterizations indicate that the lasing modes shift under varying pump densities, which can be well-explained by frequency shift and mode hopping. This work provides a versatile approach for 3D confined microresonators and opens an opportunity to realize tunable single mode microlasers. PMID:22540027

  18. Single Mode Optical Waveguide Design Investigation.

    DTIC Science & Technology

    1981-07-10

    AD-AI04 584 CORNING GLASS WORKS NY F/G 20/6 SINGLE MODE OPTICAL WAVEGUIDE DESIGN INVESTIGATION. (7 N JUL 81 V A BHAGAVATJLA, R A WESTWIG. D B KECK...Contract N00173-8O-C-0563 / V. A./Bhagavatula R. A..Westwig D. B.!Keck Corning Glass Works Corning, New York H> July 1,0, 1981 CL 8m NA Single Mode Optical...Waveguide Design Inve-tigation Progress Report 3 1. Sumpry 1.1 ,A total of six fibers have been fabricated with parameters fitting the design matrix

  19. Geothermal research on the 2.5 km deep COSC-1 drillhole, Central Sweden

    NASA Astrophysics Data System (ADS)

    Pascal, Christophe; Beltrami, Hugo; Daly, Stephen; Juhlin, Christopher; Kukkonen, Ilmo; Long, Mike; Rath, Volker; Renner, Joerg; Schwarz, Gerhard; Sundberg, Jan

    2015-04-01

    The scientific drilling project "Collisional Orogeny in the Scandinavian Caledonides" (COSC), supported by ICDP and the Swedish Research Council, involves the drilling of two boreholes through carefully selected sections of the Paleozoic Caledonian orogen in Central Sweden. COSC-1, the first of the two planned boreholes, was drilled and fully cored down to 2.5 km depth during spring and summer 2014 near the town of Åre. The COSC working group is organised around six thematic teams including us, the geothermal team. The major objectives of the COSC geothermal team are: a) to contribute to basic knowledge about the thermal regime of Palaeozoic orogenic belts, ancient shield areas and high heat-producing plutons; b) to refine knowledge on climate change at high latitudes (i.e. Scandinavia), including historical global changes, recent palaeoclimate development (since last ice age) and expected future trends; c) to determine the vertical variation of the geothermal gradient, heat flow and thermal properties down to 2.5 km, and to determine the required corrections for shallow (< 1 km) heat flow data; d) to explore the geothermal potential of the Åre-Järpen area; e) to explore to what degree the conductive heat transfer is affected by groundwater flow in the uppermost crust and f) to evaluate the heat generation input and impact from the basement and the alum shales. To reach these targets the following tasks were carried out or are planned: 1) heat flow predictions from shallow boreholes; 2) geophysical logging; 3) analyses of logs and well tests; (3) determination of rock thermal properties on core samples; 4) determination of heat generation rates from radiometric and geochemical studies; 5) fracture characterisation for permeability and convective heat flow estimations; 6) analysis of convective signals; 7) analysis of paleoclimatic signals; 8) heat flow modelling and evaluation of geothermal potential and 9) Fennoscandia heat flow map compilation. The purpose of the present contribution is to summarise the tasks completed so far and to present the on-going research by the COSC geothermal team.

  20. Route Recapitulation and Route Loyalty in Homing Pigeons: Pilotage From 25 km?

    NASA Astrophysics Data System (ADS)

    Biro, Dora; Meade, Jessica; Guilford, Tim

    2006-01-01

    We utilised precision Global Positioning System (GPS) tracking to examine the homing paths of pigeons (Columba livia) released 20 times consecutively 25 km from the loft. By the end of the training phase, birds had developed highly stereotyped yet individually distinct routes home, with detailed recapitulation evident at each stage of the journey. Following training, birds also participated in a series of releases from novel sites at perpendicular distances of up to 3 km from their established routes. Results showed that subjects were attracted back to their established routes and recapitulated them from the point of contact. Naïve conspecifics (yoked controls) released from the same off-route sites confirmed that the experienced birds' route choices were not influenced by constraints exerted by terrain features, but that increased experience with the general area conferred a homing advantage in the form of more efficient flight tracks, even from these novel sites. Patterns in the paths taken by experienced birds to rejoin their established routes are discussed with reference to navigational mechanisms employed by homing pigeons in their familiar area.

  1. Large-mode-area single-polarization single-mode photonic crystal fiber: design and analysis.

    PubMed

    Kumar, Ajeet; Saini, Than Singh; Naik, Kishor Dinkar; Sinha, Ravindra Kumar

    2016-07-01

    A rectangular core photonic crystal fiber structure has been presented and analyzed for single-polarization single-mode operation. Single-polarization is obtained with asymmetric design and by introducing different loss for x-polarization and y-polarization of fundamental modes. Single-polarization single-mode operation of the proposed photonic crystal fiber is investigated in detail by using a full vector finite element method with an anisotropic perfectly matched layer. The variations of the confinement loss and effective mode area of x-polarization and y-polarization of fundamental modes have been simulated by varying the structural parameters of the proposed photonic crystal fiber. At the optimized parameters, confinement loss and effective mode area is obtained as 0.94 dB/m and 60.67  μm2 for y-polarization as well as 26.67 dB/m and 67.23  μm2 for x-polarization of fundamental modes, respectively, at 1.55 μm. Therefore simulation results confirmed that, 0.75 m length of fiber will be sufficient to get a y-polarized fundamental mode with an effective mode area as large as 60.67  μm2.

  2. Single-mode fluorotellurite glass fiber

    NASA Astrophysics Data System (ADS)

    Zhan, Huan; Huang, Zhihua; Wen, Jing; Jiang, Lei; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

    2016-03-01

    By multi-stage rod-in-tube fiber drawing process, a single-mode fluorotellurite glass fiber was fabricated and reported for the first time. Benefiting from chemical-physical dehydration process to remove water and OH- groups, the propagation loss was decreased to 1.9 dB/m at 1550 nm and the infrared window is extended from 2.8 μm to 4.2 μm, i.e. a new kind of mid-infrared glass fiber. The fiber is with a small core of 3.52 μm in diameter to meet single-mode condition, and the effective nonlinear parameter γ was estimated to be 236.7 W-1 km-1 at 1550 nm by using continuous-wave self-phase modulation method. © 2015 Elsevier B.V.

  3. Single-mode fiber laser based on core-cladding mode conversion.

    PubMed

    Suzuki, Shigeru; Schülzgen, Axel; Peyghambarian, N

    2008-02-15

    A single-mode fiber laser based on an intracavity core-cladding mode conversion is demonstrated. The fiber laser consists of an Er-doped active fiber and two fiber Bragg gratings. One Bragg grating is a core-cladding mode converter, and the other Bragg grating is a narrowband high reflector that selects the lasing wavelength. Coupling a single core mode and a single cladding mode by the grating mode converter, the laser operates as a hybrid single-mode laser. This approach for designing a laser cavity provides a much larger mode area than conventional large-mode-area step-index fibers.

  4. Single Mode Optical Waveguide Design Study.

    DTIC Science & Technology

    1981-11-23

    AD-I7g62 CORNING GLASS WORKS NY FIG 20/6 ADA0 21 SINGLE MODE OPTICAL WAVEGUIDE DESIGN STUDY.(U) NOV 81 V A BHAGAVATJLA. D B KECK, R A WESTWIG N00173...Ralph A. Westwig Corning Glass Works ’ 1 / Research and Development-Division Sullivan Park Corning, New York Th document ha bern c -yro vd Spubc rlea...Authors: Venkata A. Bhagavatula Donald B. Keck Ralph A. Westwig Corning Glass Works Research and Development Division Sullivan Park Corning, New York 11

  5. Alcohol sensor based on single-mode-multimode-single-mode fiber structure

    NASA Astrophysics Data System (ADS)

    Mefina Yulias, R.; Hatta, A. M.; Sekartedjo, Sekartedjo

    2016-11-01

    Alcohol sensor based on Single-mode -Multimode-Single-mode (SMS) fiber structure is being proposed to sense alcohol concentration in alcohol-water mixtures. This proposed sensor uses refractive index sensing as its sensing principle. Fabricated SMS fiber structure had 40 m of multimode length. With power input -6 dBm and wavelength 1550 nm, the proposed sensor showed good response with sensitivity 1,983 dB per % v/v with measurement range 05 % v/v and measurement span 0,5% v/v.

  6. 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.

  7. Single-mode fiber systems for deep space communication network

    NASA Technical Reports Server (NTRS)

    Lutes, G.

    1982-01-01

    The present investigation is concerned with the development of single-mode optical fiber distribution systems. It is pointed out that single-mode fibers represent potentially a superior medium for the distribution of frequency and timing reference signals and wideband (400 MHz) IF signals. In this connection, single-mode fibers have the potential to improve the capability and precision of NASA's Deep Space Network (DSN). Attention is given to problems related to precise time synchronization throughout the DSN, questions regarding the selection of a transmission medium, and the function of the distribution systems, taking into account specific improvements possible by an employment of single-mode fibers.

  8. Single Mode, Extreme Precision Doppler Spectrographs

    NASA Astrophysics Data System (ADS)

    Schwab, Christian; Leon-Saval, Sergio G.; Betters, Christopher H.; Bland-Hawthorn, Joss; Mahadevan, Suvrath

    2014-04-01

    The `holy grail' of exoplanet research today is the detection of an earth-like planet: a rocky planet in the habitable zone around a main-sequence star. Extremely precise Doppler spectroscopy is an indispensable tool to find and characterize earth-like planets; however, to find these planets around solar-type stars, we need nearly one order of magnitude better radial velocity (RV) precision than the best current spectrographs provide. Recent developments in astrophotonics (Bland-Hawthorn & Horton 2006, Bland-Hawthorn et al. 2010) and adaptive optics (AO) enable single mode fiber (SMF) fed, high resolution spectrographs, which can realize the next step in precision. SMF feeds have intrinsic advantages over multimode fiber or slit coupled spectrographs: The intensity distribution at the fiber exit is extremely stable, and as a result the line spread function of a well-designed spectrograph is fully decoupled from input coupling conditions, like guiding or seeing variations (Ihle et al. 2010). Modal noise, a limiting factor in current multimode fiber fed instruments (Baudrand & Walker 2001), can be eliminated by proper design, and the diffraction limited input to the spectrograph allows for very compact instrument designs, which provide excellent optomechanical stability. A SMF is the ideal interface for new, very precise wavelength calibrators, like laser frequency combs (Steinmetz et al. 2008, Osterman et al. 2012), or SMF based Fabry-Perot Etalons (Halverson et al. 2013). At near infrared wavelengths, these technologies are ready to be implemented in on-sky instruments, or already in use. We discuss a novel concept for such a spectrograph.

  9. Mode coupling in hybrid square-rectangular lasers for single mode operation

    NASA Astrophysics Data System (ADS)

    Ma, Xiu-Wen; Huang, Yong-Zhen; Yang, Yue-De; Xiao, Jin-Long; Weng, Hai-Zhong; Xiao, Zhi-Xiong

    2016-08-01

    Mode coupling between a square microcavity and a Fabry-Pérot (FP) cavity is proposed and demonstrated for realizing single mode lasers. The modulations of the mode Q factor as simulation results are observed and single mode operation is obtained with a side mode suppression ratio of 46 dB and a single mode fiber coupling loss of 3.2 dB for an AlGaInAs/InP hybrid laser as a 300-μm-length and 1.5-μm-wide FP cavity connected to a vertex of a 10-μm-side square microcavity. Furthermore, tunable single mode operation is demonstrated with a continuous wavelength tuning range over 10 nm. The simple hybrid structure may shed light on practical applications of whispering-gallery mode microcavities in large-scale photonic integrated circuits and optical communication and interconnection.

  10. Single mode variable-sensitivity fiber optic sensors

    NASA Technical Reports Server (NTRS)

    Murphy, K. A.; Fogg, B. R.; Gunther, M. F.; Claus, R. O.

    1992-01-01

    We review spatially-weighted optical fiber sensors that filter specific vibration modes from one dimensional beams placed in clamped-free and clamped-clamped configurations. The sensitivity of the sensor is varied along the length of the fiber by tapering circular-core, dual-mode optical fibers. Selective vibration mode suppression on the order of 10 dB was obtained. We describe experimental results and propose future extensions to single mode sensor applications.

  11. The analysis and modeling of the ARDEC 2.5 km/s 20-mm plasma railgun shot

    NASA Astrophysics Data System (ADS)

    Sink, D. A.; Chang, D. I.; Davis, A.; Colombo, G.; Hildenbrand, D. J.

    1993-01-01

    The 20-mm round-bore plasma railgun was successfully fired at the ARDEC electric gun facility. The 4-m gun with copper rails and alumina composite insulators was operated using a light-gas gun injector to start the projectile, already located in the gun, moving prior to the introduction of current. Current from the EMACK homopolar generator (HPG) was commutated into the gun by an explosively-actuated opening switch. The muzzle velocity was recorded by breakwires and flash X-rays at 2.5 km/s. B-dot sensors, rail current Rogowski coils, and breech and muzzle voltage measurements provided data on the in-bore dynamics of the armature. Post-shot analysis using the ARMRAIL (ARMature Physics and RAILgun Performance Model) code successfully provided calculations reproducing all the main features of the data. Models account for the observed secondary arcs present throughout the shot and the basis for the code and physics modeling is given.

  12. Creating optical vortex modes with a single cylinder lens

    NASA Astrophysics Data System (ADS)

    Sridhar, Hamsa; Cohen, Martin G.; Noé, John W.

    2010-02-01

    Optical vortex (Laguerre-Gauss) modes can be created by introducing a π/2 phase shift between orthogonal components of Hermite-Gauss (HG) modes. The well-known astigmatic mode converter design described by M.W. Beijersbergen et al. [Optics Communications 96 pgs. 123 132, 1993] achieves this condition by manipulating the differing Gouy phases along orthogonal axes between a matched pair of cylinder lenses. Apparently not well known is that quite useful mode conversions can easily be achieved with a single cylinder lens. We explain the operating principle of such a single lens mode converter, and describe and illustrate how to match the input HG mode to the required Rayleigh range zΗ = fcyl with one additional spherical lens. Setting up and optimizing such a simplified mode converter is an excellent exercise for undergraduate students, and the resulting optical vortex beams can be used for a variety of instructional experiments.

  13. Design of SMS (Single mode-Multi mode coreless-Single mode) optical fiber as corrosion sensor

    NASA Astrophysics Data System (ADS)

    Aisyah, Putri Yeni; Hatta, Agus M.; Pratama, Detak Yan

    2016-11-01

    Conventional corrosion sensors such as ultrasonic guided waves, eddy current and thermography have been widely applied, however, these sensors have disadvantage of suffering from additional damage, as these sensors are placed in corrosive environment, often hidden and could not be directly observed, therefore corrosion inspection using conventional sensor is much more expensive and time consuming. Usage of optical fiber as corrosion sensor, based on changes in light intensity due to corrosion effect, is an alternative to overcome the disadvantage of conventional sensors. We proposed to use Single mode - Multimode Coreless - Single mode structured optical fiber as sensor. Multimode section of the optical fiber is coated with aluminium as the corrosion object. Experiment result shows that the corrosion process have an effect of decreasing the output sensor power as the corrosion rate increasing. Experimental test is conducted on the sensor, in which time interval of corrosion treatment is 9 hours. It is obtained from the test result that the highest value of output power is 13.19 dBm. Furthermore when the weight loss range of aluminium layer is 0 - 140 mg after corrosion treatment and the length of multimode fiber is 10 mm, the highest sensitivity of the sensor is 0.094 dBm/mg.

  14. The AlGaAs single-mode stability

    NASA Technical Reports Server (NTRS)

    Botez, D.; Ladany, I.

    1983-01-01

    Single-mode spectral behavior with aging in constricted double heterojunction (CDH) lasers was studied. The CDH lasers demonstrated excellent reliability ( or = 1 million years extrapolated room-temperature MTTF) and single-mode operation after 10,000 hours of 70 C aging. The deleterious effects of laser-fiber coupling on the spectra of the diodes were eliminated through the use of wedge-shaped fibers. A novel high-power large optical cavity (LOC)-type laser was developed: the terraced-heterostructure (TH)-LOC laser, which provides the highest power into a single-mode (i.e., 50 mW CW) ever reported.

  15. 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.

  16. Single-trench waveguide TE-TM mode converter.

    PubMed

    Kim, Sang-Hun; Takei, Ryohei; Shoji, Yuya; Mizumoto, Tetsuya

    2009-07-06

    A TE-TM mode converter is proposed in a single trench GaInAsP/InP waveguide, which is fabricated by a single masking and etching process. Use of single-trench structure makes the design and the fabrication much simpler. The design of single-trench mode converter is described together with its fabrication in this article. We investigated the dependence of conversion efficiency on the waveguide width, trench depth, and trench position. Also, the wavelength dependence of mode conversion efficiency was calculated in a wavelength range between 1.5 microm to 1.58 microm. 95% TE-TM mode conversion was measured at a wavelength of 1.55 microm in a fabricated device with a 210-microm half-beat length.

  17. Single Mode Optical Waveguide Design Investigation.

    DTIC Science & Technology

    1981-03-30

    ADA09 979 CORNING GLASS WORKS NY F/6 20/6 SINGLE NOOK OPTICAL WAVEGUIOC DESIGN INVESTIGATION. (U) MA 81 V A BHAGAVAY~l-A, R A WESTWIG. D 6 KECK...Bhagavatula R. A. Westwig D. B. Keck Corning Glass Wqrks Corning, N.Y. March 30, 1981 Approved L r oc e 81 415 021 1i. Summary 1.1 Lateral and angular offset...sensitivity test equipment has been designed and built. 1.2 Measurements of lateral offset sensitivity have been made on several fibers to determine

  18. Performance implications of mode partition fluctuations in nearly single longitudinal mode lasers

    SciTech Connect

    Cartledge, J.C.

    1988-05-01

    A statistical model of mode partition fluctuations is developed for semiconductor laser diodes with a single dominant lasing mode and one vestigial side mode. It is the basis of a rigorous analysis of the influence of partition fluctuations on the performance of digital lightwave transmission systems. A Gauss quadrature rule is used to evaluate the average probability of error in the presence of mode-partition-dependent shot noise, photodetector multiplication noise, circuit noise, and intersymbol interference. This methodology permits the determination of reliable performance estimates enabling the establishment of permissible degrees of mode partition fluctuations. 32 references.

  19. Separating and combining single-mode and multimode optical beams

    SciTech Connect

    Ruggiero, Anthony J; Masquelier, Donald A; Cooke, Jeffery B; Kallman, Jeffery S

    2013-11-12

    Techniques for combining initially separate single mode and multimode optical beams into a single "Dual Mode" fiber optic have been developed. Bi-directional propagation of two beams that are differentiated only by their mode profiles (i.e., wavefront conditions) is provided. The beams can be different wavelengths and or contain different modulation information but still share a common aperture. This method allows the use of conventional micro optics and hybrid photonic packaging techniques to produce small rugged packages suitable for use in industrial or military environments.

  20. Research on high-temperature sensing characteristics based on modular interference of single-mode multimode single-mode fiber

    NASA Astrophysics Data System (ADS)

    Peng, Zhaozhuang; Wang, Li; Yan, Huanhuan

    2016-11-01

    Application of high temperature fiber sensing system is very extensive. It can be mainly used in high temperature test aerospace, such as, materials, chemicals, and energy. In recent years, various on-line optical fiber interferometric sensors based on modular interference of single-mode-multimode-single-mode(SMS) fiber have been largely explored in high temperature fiber sensor. In this paper we use the special fiber of a polyimide coating, its sensor head is composed of a section of multimode fiber spliced in the middle of Single-mode fiber. When the light is launched into the multimode fiber(MMF) through the lead-in single-mode fiber(SMF), the core mode and cladding modes are excited and propagate in the MMF respectively. Then, at the MMF-SMF spliced point, the excited cladding modes coupled back into the core of lead-out SMF interfere with SMF core mode. And the wavelength of the interference dip would shift differently with the variation of the temperature. By this mean, we can achieve the measurement of temperature. The experimental results also show that the fiber sensor based on SMS structure has a highly temperature sensitivity. From 30° to 300°, with the temperature increasing, the interference dip slightly shifts toward longer wavelength and the temperature sensitivity coefficient is 0.0115nm/°. With high sensitivity, simple structure, immunity to electromagnetic interferences and a good linearity of the experimental results, the structure has an excellent application prospect in engineering field.

  1. Temperature insensitive single-mode-multimode-single-mode fiber optic structures with two multimode fibers in series.

    PubMed

    Tripathi, Saurabh Mani; Kumar, Arun; Kumar, Manoj; Bock, Wojtek J

    2014-06-01

    We propose and demonstrate a temperature insensitive single-mode-multimode-single-mode fiber optic structure consisting of two in-series multimode fibers of appropriate lengths and of opposite temperature sensitivities. A simple approximate expression to estimate the required length ratio of the multimode fiber sections has also been derived whose prediction is found in good agreement with the experiment. The study should be useful in realizing various fiber optic devices based on multimode interference with zero temperature cross sensitivity.

  2. Spectrally tailored supercontinuum generation from single-mode-fiber amplifiers

    SciTech Connect

    Hao, Qiang; Guo, Zhengru; Zhang, Qingshan; Liu, Yang; Li, Wenxue; Zeng, Heping

    2014-05-19

    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. This technique allows smooth octave supercontinuum generation by using simple single-mode fiber amplifiers rather than complicated multistage large-mode-area fiber amplifiers.

  3. Linear optical quantum computing in a single spatial mode.

    PubMed

    Humphreys, Peter C; Metcalf, Benjamin J; Spring, Justin B; Moore, Merritt; Jin, Xian-Min; Barbieri, Marco; Kolthammer, W Steven; Walmsley, Ian A

    2013-10-11

    We present a scheme for linear optical quantum computing using time-bin-encoded qubits in a single spatial mode. We show methods for single-qubit operations and heralded controlled-phase (cphase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn [Nature (London) 409, 46 (2001)] scheme. Our protocol is suited to currently available photonic devices and ideally allows arbitrary numbers of qubits to be encoded in the same spatial mode, demonstrating the potential for time-frequency modes to dramatically increase the quantum information capacity of fixed spatial resources. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84±0.07.

  4. Spectrally tailored supercontinuum generation from single-mode-fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Hao, Qiang; Guo, Zhengru; Liu, Yang; Li, Wenxue; Zhang, Qingshan; Zeng, Heping

    2014-05-01

    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. This technique allows smooth octave supercontinuum generation by using simple single-mode fiber amplifiers rather than complicated multistage large-mode-area fiber amplifiers.

  5. Tunable single-mode slot waveguide quantum cascade lasers

    SciTech Connect

    Meng, Bo; Tao, Jin; Quan Zeng, Yong; Wu, Sheng; Jie Wang, Qi

    2014-05-19

    We report experimental demonstration of tunable, monolithic, single-mode quantum cascade lasers (QCLs) at ∼10 μm with a two-section etched slot structure. A single-mode tuning range of 77 cm{sup −1} (785 nm), corresponding to ∼7.8% of the relative tuning range, was realized with a ∼20 dB side mode suppression ratio within the whole tuning range. Compared with integrated distributed feedback QCLs, our devices have the advantages of easy fabrication and a broader tuning range. Further theoretical analyses and numerical simulations show that it is possible to achieve a broad continuous tuning range by optimizing the slot structures. The proposed slot-waveguide design could provide an alternative but simple approach to the existing tuning schemes for realizing broadly continuous tunable single-mode QCLs.

  6. Optical Isolator For Use With Single-Mode Fiber

    NASA Technical Reports Server (NTRS)

    Lutes, George F.

    1988-01-01

    Assembly of commercially available components acts as single-mode fiber-optic isolator with lower forward-transmission loss and higher attenuation of reverse transmission than previously achieved in single unit. New design reduces cost and improves performance of optical gyroscopes, precise time- and frequency-signal-distribution systems, and other systems that include fiber optics and isolators.

  7. Volume production of polarization controlled single-mode VCSELs

    NASA Astrophysics Data System (ADS)

    Grabherr, Martin; King, Roger; Jäger, Roland; Wiedenmann, Dieter; Gerlach, Philipp; Duckeck, Denise; Wimmer, Christian

    2008-02-01

    Over the past 3 years laser based tracking systems for optical PC mice have outnumbered the traditional VCSEL market datacom by far. Whereas VCSEL for datacom in the 850 nm regime emit in multipe transverse modes, all laser based tracking systems demand for single-mode operation which require advanced manufacturing technology. Next generation tracking systems even require single-polarization characteristics in order to avoid unwanted movement of the pointer due to polarization flips. High volume manufacturing and optimized production methods are crucial for achieving the addressed technical and commercial targets of this consumer market. The resulting ideal laser source which emits single-mode and single-polarization at low cost is also a promising platform for further applications like tuneable diode laser absorption spectroscopy (TDLAS) or miniature atomic clocks when adapted to the according wavelengths.

  8. Abiotic and biotic controls on methane formation down to 2.5 km depth within the Precambrian Fennoscandian Shield

    NASA Astrophysics Data System (ADS)

    Kietäväinen, Riikka; Ahonen, Lasse; Niinikoski, Paula; Nykänen, Hannu; Kukkonen, Ilmo T.

    2017-04-01

    Despite a geological history characterised by high temperature and pressure processes and organic carbon deprived crystalline bedrock, large amounts of hydrocarbons are found in deep groundwaters within Precambrian continental shields. In many sites, methane comprises more that 80% of the dissolved gas phase reaching concentrations of tens of mmol l-1. In this study, we used isotopic methods to study the carbon isotope systematics and sources of crustal methane within the Fennoscandian Shield. The main study sites were the Outokumpu Deep Drill Hole and the Pyhäsalmi mine in Finland, both of which allow groundwater sampling down to 2.5 km depth and have been previously studied for their groundwater chemistry and microbiology. We show that the differences in the amount and isotopic composition of methane are related to the availability of carbon sources as well as processes behind the incorporation of hydrogen and carbon via abiotic and biotic pathways into hydrocarbon molecules. Supported by previously reported occurrences and isotopic data of deep groundwater methane in lithologically different locations in Finland and Sweden, we show that methane formation is controlled by microbial methanogenesis and abiotic reactions, as well as lithology with the metasedimentary environments being the most favourable for methane occurrence. Rather than a thermogenic relic, crustal methane within the Fennoscandian Shield is more likely the result of low temperature formation from ancient organic compounds or their inorganic intermediates such as graphite. Such crustal gases are characterised by the lack of major amounts of C2+ hydrocarbons and 13C-rich methane. Further, microbiological and isotopic geochemical evidence suggest that microbial methane is more common at depths shallower than 1.5 km.

  9. 3D reflection seismic imaging at the 2.5 km deep COSC-1 scientific borehole, central Scandinavian Caledonides

    NASA Astrophysics Data System (ADS)

    Hedin, Peter; Almqvist, Bjarne; Berthet, Théo; Juhlin, Christopher; Buske, Stefan; Simon, Helge; Giese, Rüdiger; Krauß, Felix; Rosberg, Jan-Erik; Alm, Per-Gunnar

    2016-10-01

    The 2.5 km deep scientific COSC-1 borehole (ICDP 5054-1-A) was successfully drilled with nearly complete core recovery during spring and summer of 2014. Downhole and on-core measurements through the targeted Lower Seve Nappe provide a comprehensive data set. An observed gradual increase in strain below 1700 m, with mica schists and intermittent mylonites increasing in frequency and thickness, is here interpreted as the basal thrust zone of the Lower Seve Nappe. This high strain zone was not fully penetrated at the total drilled depth and is thus greater than 800 m in thickness. To allow extrapolation of the results from downhole logging, core analysis and other experiments into the surrounding rock and to link these with the regional tectonic setting and evolution, three post-drilling high-resolution seismic experiments were conducted in and around the borehole. One of these, the first 3D seismic reflection land survey to target the nappe structures of the Scandinavian Caledonides, is presented here. It provides new information on the 3D geometry of structures both within the drilled Lower Seve Nappe and underlying rocks down to at least 9 km. The observed reflectivity correlates well with results from the core analysis and downhole logging, despite challenges in processing. Reflections from the uppermost part of the Lower Seve Nappe have limited lateral extent and varying dips, possibly related to mafic lenses or boudins of variable character within felsic rock. Reflections occurring within the high strain zone, however, are laterally continuous over distances of a kilometer or more and dip 10-15° towards the southeast. Reflections from structures beneath the high strain unit and the COSC-1 borehole can be followed through most of the seismic volume down to at least 9 km and have dips of varying degree, mainly in the east-west thrust direction of the orogen.

  10. Design and analysis of large-core single-mode windmill single crystal sapphire optical fiber

    SciTech Connect

    Cheng, Yujie; Hill, Cary; Liu, Bo; Yu, Zhihao; Xuan, Haifeng; Homa, Daniel; Wang, Anbo; Pickrell, Gary

    2016-06-01

    We present a large-core single-mode “windmill” single crystal sapphire optical fiber (SCSF) design, which exhibits single-mode operation by stripping off the higher-order modes (HOMs) while maintaining the fundamental mode. The “windmill” SCSF design was analyzed using the finite element analysis method, in which all the HOMs are leaky. The numerical simulation results show single-mode operation in the spectral range from 0.4 to 2 μm in the windmill SCSF, with an effective core diameter as large as 14 μm. Such fiber is expected to improve the performance of many of the current sapphire fiber optic sensor structures.

  11. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

    Hackel, Richard P.; Paris, Robert D.; Feldman, Mark

    1993-01-01

    A wavelength meter having a single mode fiber optics input is disclosed. The single mode fiber enables a plurality of laser beams to be multiplexed to form a multiplexed input to the wavelength meter. The wavelength meter can provide a determination of the wavelength of any one or all of the plurality of laser beams by suitable processing. Another aspect of the present invention is that one of the laser beams could be a known reference laser having a predetermined wavelength. Hence, the improved wavelength meter can provide an on-line calibration capability with the reference laser input as one of the plurality of laser beams.

  12. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

    Hackel, R.P.; Paris, R.D.; Feldman, M.

    1993-02-23

    A wavelength meter having a single mode fiber optics input is disclosed. The single mode fiber enables a plurality of laser beams to be multiplexed to form a multiplexed input to the wavelength meter. The wavelength meter can provide a determination of the wavelength of any one or all of the plurality of laser beams by suitable processing. Another aspect of the present invention is that one of the laser beams could be a known reference laser having a predetermined wavelength. Hence, the improved wavelength meter can provide an on-line calibration capability with the reference laser input as one of the plurality of laser beams.

  13. Transient Sub-Poissonian Distribution for Single-Mode Lasers

    NASA Technical Reports Server (NTRS)

    Zang, J. Y.; Gu, Q.; Tian, L. K.

    1996-01-01

    In this paper, the transient photon statistics for single-mode lasers is investigated by making use of the theory of quantum electrodynamics. By taking into account of the transitive time l,we obtain the master equation for Jaynes-Cummings model. The relation between the Mandel factor and the time is obtained by directly solving the master equation. The result shows that a transient phenomenon from the transient super-Poissonian distribution to the transient sub-Poissonian distribution occurs for single-mode lasers. In addition, the influences of the thermal light field and the cavity loss on the transient sub-Poissonian distribution are also studied.

  14. Seismic imaging in the eastern Scandinavian Caledonides: siting the 2.5 km deep COSC-2 borehole, central Sweden

    NASA Astrophysics Data System (ADS)

    Juhlin, Christopher; Hedin, Peter; Gee, David G.; Lorenz, Henning; Kalscheuer, Thomas; Yan, Ping

    2016-05-01

    The Collisional Orogeny in the Scandinavian Caledonides (COSC) project, a contribution to the International Continental Scientific Drilling Program (ICDP), aims to provide a deeper understanding of mountain belt dynamics. Scientific investigations include a range of topics, from subduction-related tectonics to the present-day hydrological cycle. COSC investigations and drilling activities are focused in central Scandinavia, where rocks from the middle to lower crust of the orogen are exposed near the Swedish-Norwegian border. Here, rock units of particular interest occur in the Seve Nappe Complex (SNC) of the so-called Middle Allochthon and include granulite facies migmatites (locally with evidence of ultra-high pressures) and amphibolite facies gneisses and mafic rocks. This complex overlies greenschist facies metasedimentary rocks of the dolerite-intruded Sarv Nappes and underlying, lower grade Jamtlandian Nappes (Lower Allochthon). Reflection seismic profiles have been an important component in the activities to image the subsurface structure in the area. Subhorizontal reflections in the upper 1-2 km are underlain and interlayered with strong west- to northwest-dipping reflections, suggesting significant east-vergent thrusting. Two 2.5 km deep fully cored boreholes are a major component of the project, which will improve our understanding of the subsurface structure and tectonic history of the area. Borehole COSC-1 (IGSN: http://hdl.handle.net/10273/ICDP5054EEW1001), drilled in the summer of 2014, targeted the subduction-related Seve Nappe Complex and the contact with the underlying allochthon. The COSC-2 borehole will be located further east and will investigate the lower grade, mainly Cambro-Silurian rocks of the Lower Allochthon, the Jamtlandian decollement, and penetrate into the crystalline basement rocks to identify the source of some of the northwest-dipping reflections. A series of high-resolution seismic profiles have been acquired along a composite ca. 55 km long profile to help locate the COSC drill holes. We present here the results from this COSC-related composite seismic profile (CSP), including new interpretations based on previously unpublished data acquired between 2011 and 2014. These seismic data, along with shallow drill holes in the Caledonian thrust front and previously acquired seismic, magnetotelluric, and magnetic data, are used to identify two potential drill sites for the COSC-2 borehole.

  15. Towards Monitoring Biodiversity in Amazonian Forests: How Regular Samples Capture Meso-Scale Altitudinal Variation in 25 km2 Plots

    PubMed Central

    Norris, Darren; Fortin, Marie-Josée; Magnusson, William E.

    2014-01-01

    Background Ecological monitoring and sampling optima are context and location specific. Novel applications (e.g. biodiversity monitoring for environmental service payments) call for renewed efforts to establish reliable and robust monitoring in biodiversity rich areas. As there is little information on the distribution of biodiversity across the Amazon basin, we used altitude as a proxy for biological variables to test whether meso-scale variation can be adequately represented by different sample sizes in a standardized, regular-coverage sampling arrangement. Methodology/Principal Findings We used Shuttle-Radar-Topography-Mission digital elevation values to evaluate if the regular sampling arrangement in standard RAPELD (rapid assessments (“RAP”) over the long-term (LTER [“PELD” in Portuguese])) grids captured patters in meso-scale spatial variation. The adequacy of different sample sizes (n = 4 to 120) were examined within 32,325 km2/3,232,500 ha (1293×25 km2 sample areas) distributed across the legal Brazilian Amazon. Kolmogorov-Smirnov-tests, correlation and root-mean-square-error were used to measure sample representativeness, similarity and accuracy respectively. Trends and thresholds of these responses in relation to sample size and standard-deviation were modeled using Generalized-Additive-Models and conditional-inference-trees respectively. We found that a regular arrangement of 30 samples captured the distribution of altitude values within these areas. Sample size was more important than sample standard deviation for representativeness and similarity. In contrast, accuracy was more strongly influenced by sample standard deviation. Additionally, analysis of spatially interpolated data showed that spatial patterns in altitude were also recovered within areas using a regular arrangement of 30 samples. Conclusions/Significance Our findings show that the logistically feasible sample used in the RAPELD system successfully recovers meso

  16. 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.

  17. Single-Mode WGM Resonators Fabricated by Diamond Turning

    NASA Technical Reports Server (NTRS)

    Grudinin, Ivan; Maleki, Lute; Savchenkov, Anatoliy; Matsko, Andrewy; Strekalov, Dmitry; Iltchenko, Vladimir

    2008-01-01

    A diamond turning process has made possible a significant advance in the art of whispering-gallery-mode (WGM) optical resonators. By use of this process, it is possible to fashion crystalline materials into WGM resonators that have ultrahigh resonance quality factors (high Q values), are compact (ranging in size from millimeters down to tens of microns), and support single electromagnetic modes. This development combines and extends the developments reported in "Few- Mode Whispering-Gallery-Mode Resonators" (NPO-41256), NASA Tech Briefs, Vol. 30, No. 1 (January 2006), page 16a and "Fabrication of Submillimeter Axisymmetric Optical Components" (NPO-42056), NASA Tech Briefs, Vol. 31, No. 5 (May 2007), page 10a. To recapitulate from the first cited prior article: A WGM resonator of this special type consists of a rod, made of a suitable transparent material, from which protrudes a thin circumferential belt of the same material. The belt is integral with the rest of the rod and acts as a circumferential waveguide. If the depth and width of the belt are made appropriately small, then the belt acts as though it were the core of a single-mode optical fiber: the belt and the rod material adjacent to it support a single, circumferentially propagating mode or family of modes. To recapitulate from the second cited prior article: A major step in the fabrication of a WGM resonator of this special type is diamond turning or computer numerically controlled machining of a rod of a suitable transparent crystalline material on an ultrahigh-precision lathe. During the rotation of a spindle in which the rod is mounted, a diamond tool is used to cut the rod. A computer program is used to control stepping motors that move the diamond tool, thereby controlling the shape cut by the tool. Because the shape can be controlled via software, it is possible to choose a shape designed to optimize a resonator spectrum, including, if desired, to limit the resonator to supporting a single mode

  18. Characteristics of SBS dynamics in single-mode optical fibres

    SciTech Connect

    Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I; Sobolev, V B

    2016-03-31

    The characteristics of the gain of Stokes pulses in single-mode optical fibres by stimulated Brillouin scattering (SBS) of monochromatic and nonmonochromatic pump signals have been investigated by numerical simulation using a spectral approach. Conditions under which 'slow light' (caused by a group delay) can be implemented are found (it is reasonable to apply this term to a process in which a pulse is delayed with conservation of its shape). The plane-wave interaction model is shown to describe adequately the dynamics of this process in single-mode fibres. A number of gain modes are investigated for Stokes pulses with different time structures upon monochromatic and nonmonochromatic excitation. A new data transfer technique is proposed, which is based on the conversion of stepwise phase modulation of the input Stokes signal into amplitude modulation of the output signal. (nonlinear optical phenomena)

  19. Single-mode dispersive waves and soliton microcomb dynamics

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    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.

  20. Transverse Mode Multi-Resonant Single Crystal Transducer

    NASA Technical Reports Server (NTRS)

    Snook, Kevin A. (Inventor); Liang, Yu (Inventor); Luo, Jun (Inventor); Hackenberger, Wesley S. (Inventor); Sahul, Raffi (Inventor)

    2015-01-01

    A transducer is disclosed that includes a multiply resonant composite, the composite having a resonator bar of a piezoelectric single crystal configured in a d(sub 32) transverse length-extensional resonance mode having a crystallographic orientation set such that the thickness axis is in the (110) family and resonance direction is the (001) family.

  1. Single Mode Operation of a Tea CO2 Ring Laser

    NASA Astrophysics Data System (ADS)

    Aram, M.; Jelvani, S.; Nazari, M.; Panahibakhsh, S.; Porhasannejad, Z.

    2013-09-01

    The experimental results of studies on a unidirectional single longitudinal mode (SLM) transversely excited atmospheric pressure (TEA) CO2 ring laser with an intra-cavity saturable absorber are reported. A simple and quick procedure to align an experimental setup is also presented, which makes it possible to reduce light losses.

  2. A design for single-polarization single-mode photonic crystal fiber with rectangular lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Wan; Li, Shu-guang; Bao, Ya-jie; Fan, Zhen-kai; An, Guo-wen

    2016-01-01

    A design for single-polarization single-mode photonic crystal fiber with rectangular lattice is proposed in this paper. The proposed fiber is studied by the full vector finite element method with perfectly matched layers. The single-polarization single-mode operation region of the fiber is achieved in a certain wavelength range with low confinement loss include the wavelength of 1.55 μm. The loss of one polarization is 0.124 dB/km at the wavelength of 1.55 μm and the confinement loss of the other one polarization is very high which can not ensure the transmission in the fiber. The single-polarization single-mode photonic crystal fiber is desirable for some polarization-sensitive applications such as high-power fiber lasers, fiber optic gyroscopes, current sensors and optical coherent communication systems.

  3. Saturation of single toroidal number Alfvén modes

    NASA Astrophysics Data System (ADS)

    Wang, X.; Briguglio, S.

    2016-08-01

    The results of numerical simulations are presented to illustrate the saturation mechanism of a single toroidal number Alfvén mode, driven unstable, in a tokamak plasma, by the resonant interaction with energetic ions. The effects of equilibrium geometry non-uniformities and finite mode radial width on the wave-particle nonlinear dynamics are discussed. Saturation occurs as the fast-ion density flattening produced by the radial flux associated to the resonant particles captured in the potential well of the Alfvén wave extends over the whole region where mode-particle power exchange can take place. The occurrence of two different saturation regimes is shown. In the first regime, dubbed resonance detuning, that region is limited by the resonance radial width (that is, the width of the region where the fast-ion resonance frequency matches the mode frequency). In the second regime, called radial decoupling, the power exchange region is limited by the mode radial width. In the former regime, the mode saturation amplitude scales quadratically with the growth rate; in the latter, it scales linearly. The occurrence of one or the other regime can be predicted on the basis of linear dynamics: in particular, the radial profile of the fast-ion resonance frequency and the mode structure. Here, we discuss how such properties can depend on the considered toroidal number and compare simulation results with the predictions obtained from a simplified nonlinear pendulum model.

  4. Collisional Orogeny in the Scandinavian Caledonides (COSC): Scientific objectives for the planned 2.5 km deep COSC-2 borehole

    NASA Astrophysics Data System (ADS)

    Juhlin, Christopher; Anderson, Mark; Dopson, Mark; Lorenz, Henning; Pascal, Christophe; Piazolo, Sandra; Roberts, Nick; Rosberg, Jan-Erik; Tsang, Chin-Fu

    2016-04-01

    The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project employs two fully cored boreholes for investigating mountain building processes at mid-crustal levels in a deeply eroded Paleozoic collisional orogen of Alpine-Himalayan size. The two COSC boreholes will provide a unique c. 5 km deep composite section from a hot allochthon through the underlying 'colder' nappes, the main décollement and into the basement of the collisional underriding plate. COSC's unprecedented wealth of geophysical field and borehole data combined with the petrology, geochronology and rock physics information obtained from the drill cores will develop into an integrated model for a major collisional mountain belt. This can be utilized as an analogue to better understand similar modern tectonic settings (Himalaya, Izu-Bonin-Mariana, amongst others) and, thus, advance our understanding of such complex systems and how they affect the (human) environment. COSC investigations and drilling activities are focused in the Åre-Mörsil area (Sweden) of central Scandinavia. The first drill hole, COSC-1, was completed in late August 2014 with near 100% core recovery down to 2.5 km. It targeted the high-grade metamorphic Seve Nappe Complex (SNC) and its contact with the underlying allochthon, investigating how this metasedimentary unit, that was initially deeply subducted during orogeny, was exhumed and then, still hot, emplaced as an allochthon onto the foreland of the underriding plate. COSC-2 will investigate the main Caledonian décollement, which is the major detachment that separates the Caledonian allochthons from the autochthonous basement of the Fennoscandian Shield, and the character of the deformation in the basement. Combined seismic, magnetotelluric (MT) and magnetic data provide control on the basement structure and the depth to the main décollement, believed to be hosted in the carbon-rich highly conductive Alum Shale. Key targets are to understand the geometry, stress distribution and rheology of the main décollement and associated fault systems in the foreland of one of the Earth's largest orogens, and to determine the relationship between the basement deformation and the thrust tectonics in the nappes above. COSC-2 will provide insights into the evolution of Baltica near the Ordovician-Silurian boundary by providing a new, distal section from the Early Paleozoic sedimentary basin. High-quality, high-resolution temperature profiles will allow the reconstruction of the ground surface temperature history and its variations for up to 100000 years and gather new knowledge about the Weichselian glaciation and climate evolution in northern Europe during the Holocene, including industrial age trends. Furthermore, research will address the hydrogeological and geothermic characteristics of the mountain belt and investigate the geological energy sources utilized by the deep biosphere. The drilling program and on-site science will build on the experience from drilling COSC-1. Applications for drilling related costs have been made to ICDP and the Swedish Research Council and if funded, drilling can be performed in 2017 at the earliest. Researchers interested in any aspect of the COSC project are invited to join and provide parallel funding for drilling, on-site science, and studies on core and downhole geophysics.

  5. Robust single-mode all-solid multi-trench fiber with large effective mode area.

    PubMed

    Jain, Deepak; Jung, Yongmin; Kim, Jaesun; Sahu, Jayanta K

    2014-09-01

    We experimentally demonstrate all-solid 30 and 90 μm core diameter multi-trench fibers. Measurements ensure an effective single-mode operation over a wide range of bend radius in the case of 30 μm core fiber, making it suitable for applications like beam delivery and compact fiber lasers. On the other hand, a 90 μm core fiber ensures an effective single-mode operation and shows good potential for rod-type fiber laser applications. Both fibers were fabricated by the conventional modified chemical vapor deposition process in conjunction with the rod-in-tube technique, hence making them suitable for mass production.

  6. Mapping vibrational surface and bulk modes in a single nanocube

    NASA Astrophysics Data System (ADS)

    Lagos, Maureen J.; Trügler, Andreas; Hohenester, Ulrich; Batson, Philip E.

    2017-03-01

    Imaging of vibrational excitations in and near nanostructures is essential for developing low-loss infrared nanophotonics, controlling heat transport in thermal nanodevices, inventing new thermoelectric materials and understanding nanoscale energy transport. Spatially resolved electron energy loss spectroscopy has previously been used to image plasmonic behaviour in nanostructures in an electron microscope, but hitherto it has not been possible to map vibrational modes directly in a single nanostructure, limiting our understanding of phonon coupling with photons and plasmons. Here we present spatial mapping of optical and acoustic, bulk and surface vibrational modes in magnesium oxide nanocubes using an atom-wide electron beam. We find that the energy and the symmetry of the surface polariton phonon modes depend on the size of the nanocubes, and that they are localized to the surfaces of the nanocube. We also observe a limiting of bulk phonon scattering in the presence of surface phonon modes. Most phonon spectroscopies are selectively sensitive to either surface or bulk excitations; therefore, by demonstrating the excitation of both bulk and surface vibrational modes using a single probe, our work represents advances in the detection and visualization of spatially confined surface and bulk phonons in nanostructures.

  7. Mapping vibrational surface and bulk modes in a single nanocube.

    PubMed

    Lagos, Maureen J; Trügler, Andreas; Hohenester, Ulrich; Batson, Philip E

    2017-03-22

    Imaging of vibrational excitations in and near nanostructures is essential for developing low-loss infrared nanophotonics, controlling heat transport in thermal nanodevices, inventing new thermoelectric materials and understanding nanoscale energy transport. Spatially resolved electron energy loss spectroscopy has previously been used to image plasmonic behaviour in nanostructures in an electron microscope, but hitherto it has not been possible to map vibrational modes directly in a single nanostructure, limiting our understanding of phonon coupling with photons and plasmons. Here we present spatial mapping of optical and acoustic, bulk and surface vibrational modes in magnesium oxide nanocubes using an atom-wide electron beam. We find that the energy and the symmetry of the surface polariton phonon modes depend on the size of the nanocubes, and that they are localized to the surfaces of the nanocube. We also observe a limiting of bulk phonon scattering in the presence of surface phonon modes. Most phonon spectroscopies are selectively sensitive to either surface or bulk excitations; therefore, by demonstrating the excitation of both bulk and surface vibrational modes using a single probe, our work represents advances in the detection and visualization of spatially confined surface and bulk phonons in nanostructures.

  8. Laser to single-mode-fiber coupling: A laboratory guide

    NASA Astrophysics Data System (ADS)

    Ladany, I.

    1992-07-01

    All the information necessary to achieve reasonably efficient coupling of semiconductor lasers to single mode fibers is collected from the literature, reworked when necessary, and presented in a mostly tabular form. Formulas for determining the laser waist radius and the fiber mode radius are given. Imaging relations connecting these values with the object and image distances are given for three types of lenses: ball, hemisphere, and Gradient Index (GRIN). Sources for these lenses are indicated, and a brief discussion is given about ways of reducing feedback effects.

  9. Feedback stabilization system for pulsed single longitudinal mode tunable lasers

    DOEpatents

    Esherick, Peter; Raymond, Thomas D.

    1991-10-01

    A feedback stabilization system for pulse single longitudinal mode tunable lasers having an excited laser medium contained within an adjustable length cavity and producing a laser beam through the use of an internal dispersive element, including detection of angular deviation in the output laser beam resulting from detuning between the cavity mode frequency and the passband of the internal dispersive element, and generating an error signal based thereon. The error signal can be integrated and amplified and then applied as a correcting signal to a piezoelectric transducer mounted on a mirror of the laser cavity for controlling the cavity length.

  10. Relaxor Ferroelectrics: Back to the Single-Soft-Mode Picture

    NASA Astrophysics Data System (ADS)

    Hehlen, B.; Al-Sabbagh, M.; Al-Zein, A.; Hlinka, J.

    2016-10-01

    The fluctuations of electric polarization in a disordered ferroelectric substance, relaxor crystal PbMg1 /3Nb2 /3O3 (PMN), were studied using a nonlinear inelastic light-scattering technique, hyper-Raman scattering, within a 5 - 100 cm-1 spectral interval and in a broad temperature range from 20 to 900 K. The split ferroelectric mode reveals a local anisotropy of up to about 400 K. Spectral anomalies observed at higher temperatures are explained as due to avoided crossing of the single primary polar soft mode with a temperature-independent, nonpolar spectral feature near 45 cm-1 , known from Raman scattering. The temperature changes of the vibrational modes involved in the measured fluctuation spectra of PMN were captured in a simple model that accounts for the temperature dependence of the dielectric permittivity as well. The observed slowing down of the relaxational dynamics directly correlates with the huge increase of the dielectric permittivity.

  11. 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.

  12. Linear Optical Quantum Computing in a Single Spatial Mode

    NASA Astrophysics Data System (ADS)

    Walmsley, Ian

    2014-05-01

    We present a scheme for linear optical quantum computing using time-bin encoded qubits in a single spatial mode. This scheme allows arbitrary numbers of qubits to be encoded in the same mode, circumventing the requirement for many spatial modes that challenges the scalability of other schemes, and exploiting the inherent stability and robustness of time-frequency optical modes. This approach leverages the architecture of modern telecommunications systems, and opens a door to very high dimensional Hilbert spaces while maintaining compact device designs. Further, temporal encodings benefit from intrinsic robustness to inhomogeneities in transmission mediums. These advantages have been recognized in works exploring the preparation of time-frequency entangled states both for tests of fundamental quantum phenomena, and for quantum communications technologies including key distribution and teleportation. Here we extend this idea to computation. In particular, we present methods for single-qubit operations and heralded controlled phase (CPhase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn scheme. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84 /pm 0.07. An analysis of the performance of current technologies suggests that our scheme offers a promising route for the construction of quantum circuits beyond the few-qubit level. In addition, we foresee that our investigation may motivate further development of the approaches presented into a regime in which time bins are temporally overlapped and frequency based manipulations become necessary, opening up encodings of even higher densities. This work was supported by the Engineering and Physical Sciences Research Council (EP/H03031X/1), the European Commission project Q-ESSENCE (248095) and the Air Force Office of Scientific Research

  13. Single mode continous wave GaAs quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Strasser, Gottfried

    2001-03-01

    Quantum cascade lasers (QCLs) are powerful light emitters in the mid infrared. We fabricated GaAs-based first order and second order distributed feedback lasers to achieve single mode emission. The emission wavelength is continuously tunable according to the temperature dependence of the effective refractive index, which shifts the Bragg wavelength. For the continous-wave operation achieved from first order DFB structures the active material consists of 40 periods of an AlAs/GaAs chirped superlattice, grown by solid source molecular beam epitaxy. A double plasmon enhanced waveguide is used for vertical optical confinement, lateral electrical and optical confinement is achieved by deep etched ridges. The Bragg grating is defined by contact lithography and etched into the surface of the top cladding layer, thus avoiding the need of regrowth. Single mode emission at 11.8 microns is observed for pulsed mode operation and for continuous-wave operation. The emission wavelength depends on the laser current, because of the electrical heating in the active material. We derive the effective temperature in the laser cavity from the emission wavelength. We use the measured dependence of the emission wavelength from the heat sink temperature in pulsed-mode operation, where the effective temperature change within a pulse can be neglected and the average heat load is low. Additionally, single mode emission from electrically pumped QCL micro-cavities (circular and deformed cross sections) and monolithic GaAs/AlGaAs QCLs with self-aligned Focused Ion Beam cut coupled cavities are demonstrated. Deep FIB etched Bragg reflectors can be used to increase the reflectivity. This work is supported by the European Project SUPERSMILE.

  14. Infrared single mode chalcogenide glass fiber for space.

    PubMed

    Houizot, P; Boussard-Plédel, C; Faber, A J; Cheng, L K; Bureau, B; Van Nijnatten, P A; Gielesen, W L M; Pereira do Carmo, J; Lucas, J

    2007-09-17

    An important measuring technique under study for the DARWIN planet finding mission, is nulling interferometry, enabling the detection of the weak infrared emission lines of an orbiting planet. This technique requires a perfect wavefront of the light beams to be combined in the interferometer. By using a single mode waveguide before detection, wavefront errors are filtered and a virtually perfect plane wavefront is obtained. In this paper the results on the development and the optical characterisation of suitable infrared transmitting chalcogenide glasses and mid-IR guiding optical fibers are reported. Two different perform techniques for manufacturing core-cladding chalcogenide fibers are described. Two types of step index fibers, prepared with Te(2)As(3)Se(5) chalcogenide glasses, offer single mode guidance at 10.6 mum.

  15. Injection seeded single mode alexandrite ring laser for lidar applications

    NASA Technical Reports Server (NTRS)

    Lee, H. Sang; Notari, Anthony

    1992-01-01

    Along with many spectroscopic applications, atmospheric lidar measurements require a tunable, narrow band laser with a very high degree of spectral purity. A standing wave pulsed alexandrite laser tuned by injection seeding with an AlGaAs laser diode has demonstrated high stability. The standing wave cavity, however, poses several difficulties in light of the single mode operation and efficient seeding beam into the cavity. In order to overcome these problems and to operate the high power alexandrite laser in a single axial mode with a high spectral purity, a new ring laser system is being developed. The design features of the ring laser and some measurements of the laser characteristics are presented.

  16. Single pulse CARS noise: a comparison between single-mode and multimode pump lasers.

    PubMed

    Snelling, D R; Sawchuk, R A; Mueller, R E

    1985-09-01

    An investigation of single pulse coherent anti-Stokes Raman spectroscopy (CARS) noise, determined by the analysis of broadband nonresonant spectra, is described. It is shown that the use of a single-mode rather than a multimode pump laser leads to a significant reduction of CARS noise (40%), down to the level exhibited by the Stokes spectral profile itself. This reduction in noise is attributed to the minimization of the effects due to random variations in the laser temporal profiles by using temporally smooth single-mode laser pumps. A measurement of detector shot noise is presented and its effect on CARS noise is described. The advantages of using a single-mode pump laser in CARS spectroscopy are discussed.

  17. Holograms for laser diode: Single mode optical fiber coupling

    NASA Technical Reports Server (NTRS)

    Fuhr, P. L.

    1982-01-01

    The low coupling efficiency of semiconductor laser emissions into a single mode optical fibers place a severe restriction on their use. Associated with these conventional optical coupling techniques are stringent alignment sensitivities. Using holographic elements, the coupling efficiency may be increased and the alignment sensitivity greatly reduced. Both conventional and computer methods used in the generation of the holographic couplers are described and diagrammed. The reconstruction geometries used are shown to be somewhat restrictive but substantially less rigid than their conventional optical counterparts. Single and double hologram techniques are examined concerning their respective ease of fabrication and relative merits.

  18. When does single-mode lasing become a condensation phenomenon?

    PubMed

    Fischer, Baruch; Weill, Rafi

    2012-11-19

    We present a generic route to classical light condensation (LC) in linear photonic mode systems, such as cw lasers, with different grounds from regular Bose-Einstein condensation (BEC). LC is based on weighting the modes in a noisy environment (spontaneous emission, etc.) in a loss-gain scale, rather than in photon energy. It is characterized by a sharp transition from a multi- to single-mode oscillation. The study uses a linear multivariate Langevin formulation which gives a mode occupation hierarchy that functions like Bose-Einstein statistics. Condensation occurs when the spectral filtering has near the lowest-loss mode a power law dependence with exponent smaller than 1. We then discuss how condensation can occur in photon systems, its relation to lasing and the difficulties to observe regular photon-BEC in laser cavities. We raise the possibility that experiments on photon condensation in optical cavities fall in a classical LC or lasing category rather than being a thermal-quantum BEC phenomenon.

  19. Liquid level sensor based on fiber ring laser with single-mode-offset coreless-single-mode fiber structure

    NASA Astrophysics Data System (ADS)

    Wang, Zixiao; Tan, Zhongwei; Xing, Rui; Liang, Linjun; Qi, Yanhui; Jian, Shuisheng

    2016-10-01

    A novel reflective liquid level sensor based on single-mode-offset coreless-single-mode (SOCS) fiber structure is proposed and experimentally demonstrated. Theory analyses and experimental results indicate that offset fusion can remarkably enhance the sensitivity of sensor. Ending-reflecting structure makes the sensor compact and easy to deploy. Meanwhile, we propose a laser sensing system, and the SOCS structure is used as sensing head and laser filter simultaneously. Experimental results show that laser spectra with high optical signal-to-noise ratio (-30 dB) and narrow 3-dB bandwidth (<0.15 nm) are achieved. Various liquids with different indices are used for liquid level sensing, besides, the refractive index sensitivity is also investigated. In measurement range, the sensing system presents steady laser output.

  20. Optical fiber magnetic field sensor based on single-mode-multimode-single-mode structure and magnetic fluid.

    PubMed

    Chen, Yaofei; Han, Qun; Liu, Tiegen; Lan, Xinwei; Xiao, Hai

    2013-10-15

    An optical fiber magnetic field sensor based on the single-mode-multimode-single-mode (SMS) structure and magnetic fluid (MF) is proposed and demonstrated. By using a piece of no-core fiber as the multimode waveguide in the SMS structure and MF sealed in a capillary tube as the magnetic sensitive media, which totally immersing the no-core fiber, an all-fiber magnetic sensor was fabricated. Interrogation of the magnetic field strength can be achieved either by measuring the dip wavelength shift of the transmission spectrum or by detecting the transmission loss at a specific wavelength. A demonstration sensor with sensitivities up to 905 pm/mT and 0.748 dB/mT was fabricated and investigated. A theoretical model for the design of the proposed device was developed and numerical simulations were performed.

  1. Arc fusion splicing effects in large-mode-area single-mode ytterbium-doped fibers.

    PubMed

    Feng, Ting; Jenkins, Micah H; Yan, Fengping; Gaylord, Thomas K

    2013-11-10

    For the first time the effects of arc fusion splicing on the residual stress and refractive index of large-mode-area single-mode ytterbium-doped fibers (YDFs) are investigated using a state-of-the-art three-dimensional concurrent stress-index measurement method. The results, based on a commercially available fiber, describe a host of perturbations that decrease the core/cladding refractive index difference by as much as 1.74 × 10(-3) over an axial length of many hundreds of wavelengths. Simulations indicate that these perturbations result in an expansion of the mode-field-diameter by 39.6% and, based on the measured sample, result in an extra splice loss of 20.8%. The results of this investigation will be useful in the design and optimization of high-power all-fiber YDF lasers and amplifiers.

  2. Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales

    SciTech Connect

    Daly, Rebecca A.; Borton, Mikayla A.; Wilkins, Michael J.; Hoyt, David W.; Kountz, Duncan J.; Wolfe, Richard A.; Welch, Susan A.; Marcus, Daniel N.; Trexler, Ryan V.; MacRae, Jean D.; Krzycki, Joseph A.; Cole, David R.; Mouser, Paula J.; Wrighton, Kelly C.

    2016-09-05

    Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that methylamine cycling supports methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while sulfide generation from thiosulfate represents a poorly recognized corrosion mechanism in shales. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.

  3. Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales.

    PubMed

    Daly, Rebecca A; Borton, Mikayla A; Wilkins, Michael J; Hoyt, David W; Kountz, Duncan J; Wolfe, Richard A; Welch, Susan A; Marcus, Daniel N; Trexler, Ryan V; MacRae, Jean D; Krzycki, Joseph A; Cole, David R; Mouser, Paula J; Wrighton, Kelly C

    2016-09-05

    Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here, the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that many of the persisting organisms play roles in methylamine cycling, ultimately supporting methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while thiosulfate reduction could produce sulfide, contributing to reservoir souring and infrastructure corrosion. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.

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

    SciTech Connect

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

    1991-01-01

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

  5. Single crystal plasticity with bend-twist modes

    NASA Astrophysics Data System (ADS)

    Elkhodary, Khalil I.; Bakr, Mohamed A.

    2015-06-01

    In this work a formulation is proposed and computationally implemented for rate dependent single crystal plasticity, which incorporates plastic bend-twist modes that arise from dislocation density based poly-slip mechanisms. The formulation makes use of higher order continuum theory and may be viewed as a generalized micromechanics model. The formulation is then linked to the burgers and Nye tensors, showing how their material rates are derivable from a newly proposed third-rank tensor Λp, which incorporates a crystallographic description of bend-twist plasticity through selectable slip-system level constitutive laws. A simple three-dimensional explicit finite element implementation is outlined and employed in three simulations: (a) bi-crystal bending; (b) tension on a notched single crystal; and (c) the large compression of a microstructure to induce the plastic buckling of secondary phases. All simulation are transient, for computational expediency. The results shed light on the physics resulting from dynamic inhomogeneous plastic deformation.

  6. A single vibration mode tubular piezoelectric ultrasonic motor.

    PubMed

    He, Siyuan; Chiarot, Paul R; Park, Soonho

    2011-05-01

    A novel tubular ultrasonic motor is presented that uses only a single vibration bending mode of a piezoelectric tube to generate rotation. When the piezoelectric tube bends, the diagonal motion of points on selected areas at the ends of the tube generates forces with tangential components along the same circumferential direction, driving the rotors to rotate. Bi-directional motion is achieved by simply switching the direction of bending. Because only one vibration mode is used, the motor requires only one driving signal and no vibration mode coupling is needed, simplifying the design, fabrication, assembly, and operation of the device. Two prototypes [one with cut-in lead zirconate titanate (PZT) teeth and one with added metal teeth] were built and tested using PZT tubes available to the authors. The tubes have an outside diameter of 6.6 mm, inner diameter of 5.0 mm, and length of 25.4 mm. The working frequencies of the two motors are 27.6 and 23.5 kHz. The motors achieved a maximum no-load speed of 400 rpm and a stall torque of 300 μN·m.

  7. Unified Scattering Parameters formalism in terms of Coupled-Mode Theory for investigating hybrid single-mode/two-mode photonic interconnects

    NASA Astrophysics Data System (ADS)

    Boucher, Yann G.; Parini, Alberto; Féron, Patrice

    2017-03-01

    In terms of Linear Algebra, a directional coupler between a single-mode waveguide and a two-mode waveguide can be thought of as formally equivalent to a set of three mutually coupled single-mode waveguides. Its responses, easily derived in the frame of ternary Coupled-Mode Theory, are used to establish analytically the scattering parameters of a hybrid ring-based modal multiplexer.

  8. Single-mode tunable laser emission in the single-exciton regime from colloidal nanocrystals.

    PubMed

    Grivas, Christos; Li, Chunyong; Andreakou, Peristera; Wang, Pengfei; Ding, Ming; Brambilla, Gilberto; Manna, Liberato; Lagoudakis, Pavlos

    2013-01-01

    Whispering-gallery-mode resonators have been extensively used in conjunction with different materials for the development of a variety of photonic devices. Among the latter, hybrid structures, consisting of dielectric microspheres and colloidal core/shell semiconductor nanocrystals as gain media, have attracted interest for the development of microlasers and studies of cavity quantum electrodynamic effects. Here we demonstrate single-exciton, single-mode, spectrally tuned lasing from ensembles of optical antenna-designed, colloidal core/shell CdSe/CdS quantum rods deposited on silica microspheres. We obtain single-exciton emission by capitalizing on the band structure of the specific core/shell architecture that strongly localizes holes in the core, and the two-dimensional quantum confinement of electrons across the elongated shell. This creates a type-II conduction band alignment driven by coulombic repulsion that eliminates non-radiative multi-exciton Auger recombination processes, thereby inducing a large exciton-bi-exciton energy shift. Their ultra-low thresholds and single-mode, single-exciton emission make these hybrid lasers appealing for various applications, including quantum information processing.

  9. Single-mode tunable laser emission in the single-exciton regime from colloidal nanocrystals

    PubMed Central

    Grivas, Christos; Li, Chunyong; Andreakou, Peristera; Wang, Pengfei; Ding, Ming; Brambilla, Gilberto; Manna, Liberato; Lagoudakis, Pavlos

    2013-01-01

    Whispering-gallery-mode resonators have been extensively used in conjunction with different materials for the development of a variety of photonic devices. Among the latter, hybrid structures, consisting of dielectric microspheres and colloidal core/shell semiconductor nanocrystals as gain media, have attracted interest for the development of microlasers and studies of cavity quantum electrodynamic effects. Here we demonstrate single-exciton, single-mode, spectrally tuned lasing from ensembles of optical antenna-designed, colloidal core/shell CdSe/CdS quantum rods deposited on silica microspheres. We obtain single-exciton emission by capitalizing on the band structure of the specific core/shell architecture that strongly localizes holes in the core, and the two-dimensional quantum confinement of electrons across the elongated shell. This creates a type-II conduction band alignment driven by coulombic repulsion that eliminates non-radiative multi-exciton Auger recombination processes, thereby inducing a large exciton–bi-exciton energy shift. Their ultra-low thresholds and single-mode, single-exciton emission make these hybrid lasers appealing for various applications, including quantum information processing. PMID:23974520

  10. Photorefractive spatial mode converter for multimode-to-single-mode fiber-optic coupling.

    PubMed

    Chiou, A; Yeh, P; Yang, C; Gu, C

    1995-05-15

    We report what is to our knowledge the first experimental demonstration of a photorefractive spatial mode converter (based on mutually pumped phase conjugation) that couples light efficiently from a multimode fiber into a singlemode fiber with an extremely large degree of tolerance to misalignment. Using an argon laser (514.5 nm) and a barium titanate crystal, we have demonstrated that the laser light can be coupled from a multimode fiber (core diameter 100 microm, numerical aperture 0.37) into a single-mode fiber (core diameter 2.9 microm, numerical aperture 0.11), with an efficiency of ~15% and an alignment tolerance of ~100 microm. The coupling efficiency is more than 2 orders of magnitude, and the tolerance to misalignments is more than 30 times better than the corresponding values achievable by conventional techniques.

  11. Coupled-Mode Theory derivation of the formal equivalence between a three-mode waveguide and a set of three mutually coupled single-mode waveguides

    NASA Astrophysics Data System (ADS)

    Boucher, Yann G.

    2017-03-01

    The formal identification between a two-mode waveguide and a system of two mutually coupled single-mode waveguides stems from the symmetries of the evolution operator. When the gap tends to zero, the super-modes of the coupled system merge continuously into the modes of the multimode waveguide. For modelling purposes, it is very tempting to extend the analogy to three-mode waveguides (and beyond). But not without some precautions…

  12. Solid state long range surface plasmon polariton single mode lasers

    NASA Astrophysics Data System (ADS)

    Karami Keshmarzi, Elham; Tait, R. Niall; Berini, Pierre

    2013-10-01

    Incorporation of a solid-state gain medium in the cladding of a Long Range Surface Plasmon Polariton (LRSPP) waveguide in order to create a single-mode near-infrared laser source is proposed. LRSPP Bragg gratings based on stepping the width of the metal strip are used to form the laser's cavity. Three laser configurations are presented: The first 2 lasers employ DBRs (Distributed Bragg Reflectors) in ECL (External Cavity Laser) architecture while the third is based on the DFB (Distributed Feedback) configuration. All 3 configurations are thermally tunable by heating the gratings directly by injecting current. The lasers are convenient to fabricate leading to inexpensive sources that could be used in optical integrated circuits or waveguide biosensors.

  13. Single-Mode, Distributed Feedback Interband Cascade Lasers

    NASA Technical Reports Server (NTRS)

    Frez, Clifford F. (Inventor); Borgentun, Carl E. (Inventor); Briggs, Ryan M. (Inventor); Bagheri, Mahmood (Inventor); Forouhar, Siamak (Inventor)

    2016-01-01

    Single-mode, distributed feedback interband cascade lasers (ICLs) using distributed-feedback gratings (e.g., lateral Bragg gratings) and methods of fabricating such ICLs are provided. The ICLs incorporate distributed-feedback gratings that are formed above the laser active region and adjacent the ridge waveguide (RWG) of the ICL. The ICLs may incorporate a double-ridge system comprising an optical confinement structure (e.g., a RWG) disposed above the laser active region that comprises the first ridge of the double ridge system, a DFB grating (e.g., lateral Bragg grating) disposed above the laser active region and adjacent the optical confinement structure, and an electric confinement structure that passes at least partially through the laser active region and that defines the boundary of the second ridge comprises and the termination of the DFB grating.

  14. A face-shear mode single crystal ultrasonic motor

    NASA Astrophysics Data System (ADS)

    Li, Shiyang; Jiang, Wenhua; Zheng, Limei; Cao, Wenwu

    2013-05-01

    We report a face-shear mode ultrasonic motor (USM) made of [011]c poled Zt ± 45° cut 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 single crystal, which takes advantage of the extremely large d36 = 2368 pC/N. This motor has a maximum no-load linear velocity of 182.5 mm/s and a maximum output force of 1.03 N under the drive of Vp = 50 V, f = 72 kHz. Compared with the k31 mode USM made of Pb(Zr,Ti)O3 (PZT), our USM has simpler structure, lower driving frequency, much higher electromechanical coupling factor, and twice power density. This USM can be used for low frequency operation as well as cryogenic actuation with a large torque.

  15. The reachable set of single-mode quadratic Hamiltonians

    NASA Astrophysics Data System (ADS)

    Shackerley-Bennett, Uther; Pitchford, Alexander; Genoni, Marco G.; Serafini, Alessio; Burgarth, Daniel K.

    2017-04-01

    Open-loop controllability in quantum mechanics refers to finding conditions on time-varying Hamiltonians such that a full group of unitary transformations can be enacted with them. For compact groups controllability is well understood and is dealt with using the Lie algebra rank criterion. Gaussian systems, however, evolve under Hamiltonians generating the non-compact symplectic group, rendering the rank criterion necessary but no longer sufficient. In this setting it is possible to satisfy the rank criterion without the ability to enact all symplectic transformations. We refer to such systems as ‘unstable’ and explore the set of symplectic transformations that remain reachable. We provide a partial analytical characterisation for the reachable set of a single-mode unstable system. From this it is proven that no orthogonal-symplectic operations (‘energy-preserving’ or ‘passive’ in the literature) may be reached with such controls. We then apply numerical optimal control algorithms to demonstrate a complete characterisation of the set in specific cases. These results suggest approaches to the long-standing open problem of controllability in n modes.

  16. 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.

  17. Intensity based sensor based on single mode optical fiber patchcords

    NASA Astrophysics Data System (ADS)

    Bayuwati, Dwi; Waluyo, Tomi Budi; Mulyanto, Imam

    2016-11-01

    This paper describes the use of several single mode (SM) fiber patchcords available commercially in the market for intensity based sensor by taking the benefit of bending loss phenomenon. Firtsly, the full transmission spectrum of all fiber patchcords were measured and analyzed to examine its bending properties at a series of wavelength using white light source and optical spectrum analyzer. Bending spectral at various bending diameter using single wavelength light sources were then measured for demonstration.Three good candidates for the intensity based sensor are SM600 fiber patchcord with 970 nm LED, SMF28 fiber patchcord with 1050 nm LED and 780HP fiber patchcord with 1310 nm LED which have noticeable bending sensitive area. Experiments show that the combination of the SMF28with 1050 nm LED has 30 mm measurement range which is the widest; with sensitivity 0.107 dB/mm and resolution 0.5 mm compared with combination of SM600 patchcord and LED 970 nm which has the best sensitivity (0.891 dB/mm) and resolution (0.06 mm) but smaller range measurement (10 mm). Some suitable applications for each fiber patchcord - light source pair have also been discussed.

  18. A partial coupling power of single mode fiber fusion

    NASA Astrophysics Data System (ADS)

    Saktioto, Toto; Ali, Jalil; Rahman, Rosly Abdul; Fadhali, Mohammed; Zainal, Jasman

    2008-01-01

    Coupled fibers are successfully fabricated by injecting hydrogen flow at 1bar and fused slightly by unstable torch flame in the range of 800-1350°C. Optical parameters may vary significantly over wide range physical properties. Coupling coefficient and refractive index are estimated from the experimental result of the coupling ratio distribution from 1% to 75%. The change of structural and geometrical fiber affects the normalized frequency (V) even for single mode fibers. Coupling ratio as a function of coupling coefficient and separation of fiber axis changes with respect to V at coupling region. V is derived from radius, wavelength and refractive index parameters. Parametric variations are performed on the left and right hand side of the coupling region. At the center of the coupling region V is assumed constant. A partial power is modeled and derived using V, normalized lateral phase constant (u), and normalized lateral attenuation constant, (w) through the second kind of modified Bessel function of the l order, which obeys the normal mode, LP 01 and normalized propagation constant (b). Total power is maintained constant in order to comply with the energy conservation law. The power is integrated through V, u and w over the pulling length range of 7500-9500 μm for 1-D where radial and angle directions are ignored. The core radius of fiber significantly affects V and power partially at coupling region rather than wavelength and refractive index of core and cladding. This model has power phenomena in transmission and reflection for industrial application of coupled fibers.

  19. Aligning Arrays of Lenses and Single-Mode Optical Fibers

    NASA Technical Reports Server (NTRS)

    Liu, Duncan

    2004-01-01

    A procedure now under development is intended to enable the precise alignment of sheet arrays of microscopic lenses with the end faces of a coherent bundle of as many as 1,000 single-mode optical fibers packed closely in a regular array (see Figure 1). In the original application that prompted this development, the precise assembly of lenses and optical fibers serves as a single-mode spatial filter for a visible-light nulling interferometer. The precision of alignment must be sufficient to limit any remaining wavefront error to a root-mean-square value of less than 1/10 of a wavelength of light. This wavefront-error limit translates to requirements to (1) ensure uniformity of both the lens and fiber arrays, (2) ensure that the lateral distance from the central axis of each lens and the corresponding optical fiber is no more than a fraction of a micron, (3) angularly align the lens-sheet planes and the fiber-bundle end faces to within a few arc seconds, and (4) axially align the lenses and the fiber-bundle end faces to within tens of microns of the focal distance. Figure 2 depicts the apparatus used in the alignment procedure. The beam of light from a Zygo (or equivalent) interferometer is first compressed by a ratio of 20:1 so that upon its return to the interferometer, the beam will be magnified enough to enable measurement of wavefront quality. The apparatus includes relay lenses that enable imaging of the arrays of microscopic lenses in a charge-coupled-device (CCD) camera that is part of the interferometer. One of the arrays of microscopic lenses is mounted on a 6-axis stage, in proximity to the front face of the bundle of optical fibers. The bundle is mounted on a separate stage. A mirror is attached to the back face of the bundle of optical fibers for retroreflection of light. When a microscopic lens and a fiber are aligned with each other, the affected portion of the light is reflected back by the mirror, recollimated by the microscopic lens, transmitted

  20. Single versus successive pop-in modes in nanoindentation tests of single crystals

    SciTech Connect

    Xia, Yuzhi; Gao, Yanfei; Pharr, George M.; Bei, Hongbin

    2016-05-24

    From recent nanoindentation experiments, two types of pop-in modes have been identified: a single pop-in with a large displacement excursion, or a number of pop-ins with comparable and small displacement excursions. Theoretical analyses are developed here to study the roles played by indenter tip radius, pre-existing defect density, heterogeneous nucleation source type, and lattice resistance on the pop-in modes. The evolution of dislocation structures in earlier pop-ins provides input to modeling a stochastic, heterogeneous mechanism that may be responsible for the subsequent pop-ins. It is found that when the first pop-in occurs near theoretical shear stress, the pop-in mode is determined by the lattice resistance and tip radius. When the first pop-in occurs at low shear stress, whether the successive pop-in mode occurs depends on how the heterogeneous dislocation nucleation source density increases as compared to the increase of the total dislocation density. Lastly, the above transitions are found to correlate well with the ratio of indenter tip radius to the mean spacing of dislocation nucleation sources.

  1. Single versus successive pop-in modes in nanoindentation tests of single crystals

    DOE PAGES

    Xia, Yuzhi; Gao, Yanfei; Pharr, George M.; ...

    2016-05-24

    From recent nanoindentation experiments, two types of pop-in modes have been identified: a single pop-in with a large displacement excursion, or a number of pop-ins with comparable and small displacement excursions. Theoretical analyses are developed here to study the roles played by indenter tip radius, pre-existing defect density, heterogeneous nucleation source type, and lattice resistance on the pop-in modes. The evolution of dislocation structures in earlier pop-ins provides input to modeling a stochastic, heterogeneous mechanism that may be responsible for the subsequent pop-ins. It is found that when the first pop-in occurs near theoretical shear stress, the pop-in mode ismore » determined by the lattice resistance and tip radius. When the first pop-in occurs at low shear stress, whether the successive pop-in mode occurs depends on how the heterogeneous dislocation nucleation source density increases as compared to the increase of the total dislocation density. Lastly, the above transitions are found to correlate well with the ratio of indenter tip radius to the mean spacing of dislocation nucleation sources.« less

  2. Measurements of the ozone vertical distribution (0-25 km): Comparison of various instruments, Gap - Observatoire de Haute-Provence June 1981

    NASA Astrophysics Data System (ADS)

    Megie, G.; Pelon, J.

    1983-07-01

    A tentative comparison is made between the various instruments operated at Gap and at the Observatoire de Haute-Provence to measure the ozone vertical distribution up to 25 km during the Intercomparison Ozone Campaign. This includes comparison of the three ozonosondes carried on the same payload during the stratospheric open air balloon flights on 19 June and 25/26 June 1981, comparison between Brewer Mast sondes and electrochemical concentration cells on 19 and 26 June. A specific comparison has been made between a ground-based lidar and ECC sondes launched at the same location on 20/21 June 1981. Also compared are the ozone distributions as monitored between 12 June and 20 June 1981 by two ground-based instruments : lidar (active sounding) or Dobson spectrometer using the Umkehr method. Analysis of the various data set are performed in terms of relative variations observed and potential causes of discrepancies.

  3. DEEP BIOSPHERE. Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floor.

    PubMed

    Inagaki, F; Hinrichs, K-U; Kubo, Y; Bowles, M W; Heuer, V B; Hong, W-L; Hoshino, T; Ijiri, A; Imachi, H; Ito, M; Kaneko, M; Lever, M A; Lin, Y-S; Methé, B A; Morita, S; Morono, Y; Tanikawa, W; Bihan, M; Bowden, S A; Elvert, M; Glombitza, C; Gross, D; Harrington, G J; Hori, T; Li, K; Limmer, D; Liu, C-H; Murayama, M; Ohkouchi, N; Ono, S; Park, Y-S; Phillips, S C; Prieto-Mollar, X; Purkey, M; Riedinger, N; Sanada, Y; Sauvage, J; Snyder, G; Susilawati, R; Takano, Y; Tasumi, E; Terada, T; Tomaru, H; Trembath-Reichert, E; Wang, D T; Yamada, Y

    2015-07-24

    Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10(4) cells cm(-3). Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed.

  4. Stimulated Brillouin scattering in single mode optical fiber

    NASA Astrophysics Data System (ADS)

    Davis, Michael Andrew

    1997-09-01

    This thesis describes a number of experiments that have been performed to study various effects of stimulated Brillouin scattering (SBS) in single mode optical fibers. We have investigated the scattering process by measuring the power limiting effects and increased noise characteristics under different conditions. Additionally, we show a correlation between the relative intensity noise of the Brillouin scattered signal and its spectral bandwidth, which reinforces the theory that spontaneous Brillouin scattering is 'seeded' by random thermal perturbations in the optical fiber. This initial work demonstrates the potentially detrimental effects SBS can have on optical fiber systems. We have therefore also investigated a technique that will suppress the generation of Brillouin scattering. A phase modulation concept is described and the performance of the scheme is demonstrated with Mach-Zehnder interferometric sensors. In addition to the negative effects of SBS, certain aspects of the scattering process, such as the inherent Brillouin gain, can be used in a beneficial manner. We experiment with using the Brillouin scattering gain to produce a ring resonator laser and the generation of multiple laser signals. Furthermore, we demonstrate the use of the SBS gain to sense external strain and temperature perturbations of the optical fiber.

  5. Single- and two-mode quantumness at a beam splitter

    NASA Astrophysics Data System (ADS)

    Brunelli, Matteo; Benedetti, Claudia; Olivares, Stefano; Ferraro, Alessandro; Paris, Matteo G. A.

    2015-06-01

    In the context of bipartite bosonic systems, two notions of classicality of correlations can be defined: P classicality, based on the properties of the Glauber-Sudarshan P function; and C classicality, based on the entropic quantum discord. It has been shown that these two notions are maximally inequivalent in a static (metric) sense, as they coincide only on a set of states of zero measure. We extend and reinforce quantitatively this inequivalence by addressing the dynamical relation between these types of nonclassicality in a paradigmatic quantum-optical setting: the linear mixing at a beam splitter of a single-mode Gaussian state with a thermal reference state. Specifically, we show that almost all P -classical input states generate outputs that are not C classical. Indeed, for the case of zero thermal reference photons, the more P -classical resources at the input the less C classicality at the output. In addition, we show that the P classicality at the input—as quantified by the nonclassical depth—does instead determine quantitatively the potential of generating output entanglement. This endows the nonclassical depth with a new operational interpretation: it gives the maximum number of thermal reference photons that can be mixed at a beam splitter without destroying the output entanglement.

  6. Optical transmission through a polarization preserving single mode optical fiber at two Ar(+) laser wavelengths

    NASA Technical Reports Server (NTRS)

    Tedjojuwono, Ken K.; Hunter, William W., Jr.

    1989-01-01

    The transmission characteristics of two Ar(+) laser wavelengths through a twenty meter Panda type Polarization Preserving Single Mode Optical Fiber (PPSMOF) were measured. The measurements were done with both single and multi-longitudinal mode radiation. In the single longitudinal mode case, a degrading Stimulated Brillouin Scattering (SBS) is observed as a backward scattering loss. By choosing an optimum coupling system and manipulating the input polarization, the threshold of the SBS onset can be raised and the transmission efficiency can be increased.

  7. Comparison of high power large mode area and single mode 1908nm Tm-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Johnson, Benjamin R.; Creeden, Daniel; Limongelli, Julia; Pretorius, Herman; Blanchard, Jon; Setzler, Scott D.

    2016-03-01

    We compare large mode area (LMA) and single-mode (SM) double-clad fiber geometries for use in high power 1908nm fiber lasers. With a simple end-pumped architecture, we have generated 100W of 1908nm power with LMA fiber at 40% optical efficiency and 117W at 52.2% optical efficiency with single-mode fiber. We show the LMA fiber is capable of generating >200W and the SM fiber is capable of >300W at 1908nm. In all cases, the fiber lasers are monolithic power-oscillators with no free-space coupling.

  8. 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.

  9. Tunable continuous wave single-mode dye laser directly pumped by a diode laser

    NASA Astrophysics Data System (ADS)

    Stefanska, D.; Suski, M.; Furmann, B.

    2017-04-01

    In this work, a tunable continuous wave single-mode ring dye laser (a modified version of Coherent model CR 699-21), directly optically pumped by an economy-class diode laser, has been set up. The laser was operated on Coumarin 498, and its generation profile covered part of the green spectral region not easily accessible in single-mode operation. The performance of the laser in both broad-band and single-mode operation regimes was studied. It was proved that optical pumping by diode lasers allows one to obtain single-mode operation of dye lasers that is sufficiently stable for high-resolution spectroscopy applications.

  10. Detecting mode hopping in single-longitudinal-mode fiber ring lasers based on an unbalanced fiber Michelson interferometer.

    PubMed

    Ma, Mingxiang; Hu, Zhengliang; Xu, Pan; Wang, Wei; Hu, Yongming

    2012-10-20

    A method of detecting mode hopping for single-longitudinal-mode (SLM) fiber ring lasers has been proposed and experimentally demonstrated. The method that is based on an unbalanced Michelson interferometer (MI) utilizing phase generated carrier modulation instantly transforms mode-hopping dynamics into steep phase changes of the interferometer. Multiform mode hops in an SLM erbium-doped fiber ring laser with an 18.6 MHz mode spacing have been detected exactly in real-time domain and discussed in detail. Numerical results show that the MI-based method has a high testing sensitivity for identifying mode hopping, which will play a significant role in evaluating the output stability of SLM fiber lasers.

  11. Broadband robustly single-mode hollow-core PCF by resonant filtering of higher-order modes.

    PubMed

    Uebel, Patrick; Günendi, Mehmet C; Frosz, Michael H; Ahmed, Goran; Edavalath, Nitin N; Ménard, Jean-Michel; Russell, Philip St J

    2016-05-01

    We report a hollow-core photonic crystal fiber that is engineered so as to strongly suppress higher-order modes, i.e., to provide robust LP01 single-mode guidance in all the wavelength ranges where the fiber guides with low loss. Encircling the core is a single ring of nontouching glass elements whose modes are tailored to ensure resonant phase-matched coupling to higher-order core modes. We show that the resulting modal filtering effect depends on only one dimensionless shape parameter, akin to the well-known d/Λ parameter for endlessly single-mode solid-core PCF. Fabricated fibers show higher-order mode losses some ∼100 higher than for the LP01 mode, with LP01 losses <0.2  dB/m in the near-infrared and a spectral flatness ∼1  dB over a >110  THz bandwidth.

  12. 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.

  13. Lasing mode regulation and single-mode realization in ZnO whispering gallery microcavities by the Vernier effect.

    PubMed

    Wang, Y Y; Xu, C X; Jiang, M M; Li, J T; Dai, J; Lu, J F; Li, P L

    2016-10-07

    The wide direct bandgap and strong exciton binding energy of ZnO have inspired examinations of ultraviolet lasing over the previous decades. However, regulation of the lasing mode, especially the realization of single mode lasing, is still a challenge. In this study, a ZnO comb-like structure with an array of microrods was selected to design coupled whispering-gallery-mode cavities, wherein the naturally varied air-gap between the adjacent microrods created a flexible condition for optical field coupling without any complicated micromanipulation. Spectral behaviour of lasing and coupling interaction between coupled ZnO microrods were systematically investigated. By regulating the nano-scale inter-space of dual coupled microrods, stable single-mode lasing with a higher Q factor and lower threshold was obtained successfully based on the Vernier effect. The formation conditions and the mechanism of single-mode lasing derived from the coupled ZnO microrods were discussed in detail. It also demonstrated an approach to construct high quality single-mode lasing by tuning the diameters of the coupled ZnO microrods.

  14. Coupling loss theory of single-mode waveguide resonators

    NASA Astrophysics Data System (ADS)

    Hill, C. A.; Hall, D. R.

    1985-05-01

    In studies of mode coupling losses in circular and rectangular waveguide lasers, it has been frequently assumed that the laser mode is pure EH(11). A flaw is presently noted in the Laguerre-Gaussian mode expansion method as it appeared in Abrams (1972), and its reconciliation with later results is undertaken. Attention is also given to several discrepancies in the published accounts of the manner in which the EH(11) loss behaves in the frequently considered, near-Case I reflector constituted by a plane mirror located within a few widths of the guide aperture.

  15. Gain Filtering for Single-Spatial-Mode Operation of Large-Mode-Area Fiber Amplifiers

    SciTech Connect

    Marciante, J.R.

    2009-02-06

    Gain filtering of higher order modes in large-mode-area fibers is an extremely robust method for providing diffraction-limited performance regardless of core diameter or input beam quality. Analytic calculations demonstrate that reducing the diameter of the gain dopants compared to the waveguide diameter produces differential gain that is higher for the fundamental mode than all other fiber modes at all saturation levels. Matching the gain dopant to the mode profile is not as beneficial as a simple step profile since the primarymechanism of gain filtering is to deny gain toward the edge of the waveguide where most of the higher order mode power is contained. Numerical simulations of multikilowatt fiber amplifiers with up to 100-μm-diameter cores show that gain filtering is extremely robust, providing 99% of the output power in the fundamental mode output with only 90% of the seed power in the fundamental mode. Even with poor seed launch with 50% of the power in the fundamental mode, gain filtering can provide up to 90% of the output power in the fundamental mode.

  16. The observation of comblike transmission spectrum from a tapered single mode fiber tip

    NASA Astrophysics Data System (ADS)

    Li, Y.; Bao, X.

    2008-12-01

    Tapered fiber tips are fabricated by the fast stretching of a heated single mode fiber until it breaks. As the fiber tip diameter decreases, the propagation mode converts from the single core mode to a few cladding modes. The cladding modes are then emitted from the fiber tip and interfere with each other in the near field. Along the propagation direction, the optical field is found to be modulated due to multibeam interferences. Interestingly, broadband transmission spectrums show equidistant comblike peaks. A tunable spatial filter based on a fiber tip is realized to reshape a broadband light source.

  17. Mode Analysis with Autocorrelation Method (Single Time Series) in Tokamak

    NASA Astrophysics Data System (ADS)

    Saadat, Shervin; Salem, Mohammad K.; Goranneviss, Mahmoud; Khorshid, Pejman

    2010-08-01

    In this paper plasma mode analyzed with statistical method that designated Autocorrelation function. Auto correlation function used from one time series, so for this purpose we need one Minov coil. After autocorrelation analysis on mirnov coil data, spectral density diagram is plotted. Spectral density diagram from symmetries and trends can analyzed plasma mode. RHF fields effects with this method ate investigated in IR-T1 tokamak and results corresponded with multichannel methods such as SVD and FFT.

  18. Multichannel mode conversion and multiplexing based on a single spatial light modulator for optical communication

    NASA Astrophysics Data System (ADS)

    Nie, Song; Yu, Song; Cai, Shanyong; Lan, Mingying; Gu, Wanyi

    2016-07-01

    A method is proposed to achieve multichannel mode conversion and multiplexing by dividing a single spatial light modulator into several blocks with the mode conversion pattern and blazed grating loaded on each block. The conversion patterns realize the precise excitation of higher order modes using combined amplitude and phase modulation. The blazed gratings bring together incident beams, so these beams can be coupled into few-mode fiber (FMF). In the experiment, four higher order modes are precisely excited and converge with a tilt angle. Through the simulation method, these beams can be coupled into FMF with small tilt angles (0.0344 deg for LP11 mode).

  19. Efficient coupling of starlight into single mode photonics using Adaptive Injection (AI)

    NASA Astrophysics Data System (ADS)

    Norris, Barnaby; Cvetojevic, Nick; Gross, Simon; Arriola, Alexander; Tuthill, Peter; Lawrence, Jon; Richards, Samuel; Goodwin, Michael; Zheng, Jessica

    2016-08-01

    Using single-mode fibres in astronomy enables revolutionary techniques including single-mode interferometry and spectroscopy. However, injection of seeing-limited starlight into single mode photonics is extremely difficult. One solution is Adaptive Injection (AI). The telescope pupil is segmented into a number of smaller subapertures each with size r0, such that seeing can be approximated as a single tip / tilt / piston term for each subaperture, and then injected into a separate fibre via a facet of a segmented MEMS deformable mirror. The injection problem is then reduced to a set of individual tip tilt loops, resulting in high overall coupling efficiency.

  20. Single-mode glass waveguide technology for optical interchip communication on board level

    NASA Astrophysics Data System (ADS)

    Brusberg, Lars; Neitz, Marcel; Schröder, Henning

    2012-01-01

    The large bandwidth demand in long-distance telecom networks lead to single-mode fiber interconnects as result of low dispersion, low loss and dense wavelength multiplexing possibilities. In contrast, multi-mode interconnects are suitable for much shorter lengths up to 300 meters and are promising for optical links between racks and on board level. Active optical cables based on multi-mode fiber links are at the market and research in multi-mode waveguide integration on board level is still going on. Compared to multi-mode, a single-mode waveguide has much more integration potential because of core diameters of around 20% of a multi-mode waveguide by a much larger bandwidth. But light coupling in single-mode waveguides is much more challenging because of lower coupling tolerances. Together with the silicon photonics technology, a single-mode waveguide technology on board-level will be the straight forward development goal for chip-to-chip optical interconnects integration. Such a hybrid packaging platform providing 3D optical single-mode links bridges the gap between novel photonic integrated circuits and the glass fiber based long-distance telecom networks. Following we introduce our 3D photonic packaging approach based on thin glass substrates with planar integrated optical single-mode waveguides for fiber-to-chip and chip-to-chip interconnects. This novel packaging approach merges micro-system packaging and glass integrated optics. It consists of a thin glass substrate with planar integrated singlemode waveguide circuits, optical mirrors and lenses providing an integration platform for photonic IC assembly and optical fiber interconnect. Thin glass is commercially available in panel and wafer formats and characterizes excellent optical and high-frequency properties. That makes it perfect for microsystem packaging. The paper presents recent results in single-mode waveguide technology on wafer level and waveguide characterization. Furthermore the integration in a

  1. Refractive index sensor based on an abrupt taper Michelson interferometer in a single-mode fiber.

    PubMed

    Tian, Zhaobing; Yam, Scott S-H; Loock, Hans-Peter

    2008-05-15

    A simple refractive index sensor based on a Michelson interferometer in a single-mode fiber is constructed and demonstrated. The sensor consists of a single symmetrically abrupt taper region in a short piece of single-mode fiber that is terminated by approximately 500 nm thick gold coating. The sensitivity of the new sensor is similar to that of a long-period-grating-type sensor, and its ease of fabrication offers a low-cost alternative to current sensing applications.

  2. Surface plasmon induced polarization rotation and optical vorticity in a single mode waveguide.

    PubMed

    Davids, P S; Block, B A; Reshotko, M R; Cadien, K C

    2007-07-23

    The control and manipulation of the mode polarization state in a single mode dielectric waveguide is of considerable significance for optical information processing utilizing the polarization state to store digital information and integrated photonic devices used for high speed signaling. Here we report on an integrated on-chip mode polarization rotation based on short metal Cu electrodes placed in close proximity to the dielectric waveguide core. Polarization mode rotation with specific rotation of 10(4) degrees/mm is observed for offset metallic electrodes placed diagonally along a single mode dielectric waveguide. The mechanism for the polarization rotation is shown to be directional coupling into guided surface plasmon modes at the metal corners and coupling between the guided plasmon modes. This inter-plasmon coupling gives rise to giant polarization rotation and optical vorticity (helical power flow) in the waveguide.

  3. 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.

  4. Phosphate single mode large mode area all-solid photonic crystal fiber with multi-watt output power

    SciTech Connect

    Wang, Longfei; He, Dongbing; Yu, Chunlei; Hu, Lili; Chen, Danping; Liu, Hui; Qiu, Jianrong

    2014-03-31

    An index-depressed active core, single-mode phosphate all-solid large-mode-area photonic crystal fiber (PCF) is theoretically investigated using full-vectorial finite difference approach and experimentally realized. The PCF has a maximum output power of 5.4 W and 31% slope efficiency. Single-mode operation is realized through PCFs with core diameters of 30, 35, and 40 μm, respectively. The beam quality is not degraded even at maximum output power. Our simulations and experiments reveal that the laser performance is significantly affected by the center-to-center distance between the two nearest rods Λ, the rod diameter d, and their ratio d/Λ, implying that much attention should be given in employing optimal parameters to achieve excellent laser performance.

  5. Fourier synthesis with single-mode pulses from a multimode laser.

    PubMed

    Lobach, Ivan A; Kablukov, Sergey I; Podivilov, Evgeniy V; Fotiadi, Andrei A; Babin, Sergey A

    2015-08-01

    Short pulses are generated by mode-locking techniques: amplitude modulation in time domain or frequency modulation in frequency domain. Direct Fourier synthesis of radiation from several single-frequency sources offers an opportunity to generate arbitrary waveforms. Here we report on a new technique of short-pulse synthesis in the Fourier domain. Instead of independent laser sources, we use a single multimode laser with retrieval of its individual cavity modes into a time sequence coherently combined in an external cavity. Combination of 20 consequent single-mode pulses has been performed, demonstrating a new way for arbitrary waveforms synthesis.

  6. Single-mode lasing from dye-doped holographic polymer-dispersed liquid crystal transmission gratings

    NASA Astrophysics Data System (ADS)

    Huang, Wenbin; Liu, Quan; Xuan, Li; Chen, Linsen

    2014-12-01

    We demonstrate single-mode laser operation in dye-doped holographic polymer-dispersed liquid crystal (HPDLC) transmission gratings. The gratings are fabricated in cells made from specifically chosen glass substrates to decrease the refractive index difference between the waveguide core layer and cladding layer. The phase separation degree of liquid crystal after holographic recording is further optimized to confine only the lowest propagation mode in the device. The mode selection mechanism is explained under the framework of the waveguide distributed feedback (DFB) theory. The wavelength of single-mode lasing can be tuned between 620 and 660 nm by varying the grating period. Our results show the HPDLC technique could provide single-mode organic DFB lasers in a tunable, simple, and large-area manner.

  7. Multiplexed single-mode wavelength-to-time mapping of multimode light

    PubMed Central

    Chandrasekharan, Harikumar K; Izdebski, Frauke; Gris-Sánchez, Itandehui; Krstajić, Nikola; Walker, Richard; Bridle, Helen L.; Dalgarno, Paul A.; MacPherson, William N.; Henderson, Robert K.; Birks, Tim A.; Thomson, Robert R.

    2017-01-01

    When an optical pulse propagates along an optical fibre, different wavelengths travel at different group velocities. As a result, wavelength information is converted into arrival-time information, a process known as wavelength-to-time mapping. This phenomenon is most cleanly observed using a single-mode fibre transmission line, where spatial mode dispersion is not present, but the use of such fibres restricts possible applications. Here we demonstrate that photonic lanterns based on tapered single-mode multicore fibres provide an efficient way to couple multimode light to an array of single-photon avalanche detectors, each of which has its own time-to-digital converter for time-correlated single-photon counting. Exploiting this capability, we demonstrate the multiplexed single-mode wavelength-to-time mapping of multimode light using a multicore fibre photonic lantern with 121 single-mode cores, coupled to 121 detectors on a 32 × 32 detector array. This work paves the way to efficient multimode wavelength-to-time mapping systems with the spectral performance of single-mode systems. PMID:28120822

  8. Multiplexed single-mode wavelength-to-time mapping of multimode light

    NASA Astrophysics Data System (ADS)

    Chandrasekharan, Harikumar K.; Izdebski, Frauke; Gris-Sánchez, Itandehui; Krstajić, Nikola; Walker, Richard; Bridle, Helen L.; Dalgarno, Paul A.; MacPherson, William N.; Henderson, Robert K.; Birks, Tim A.; Thomson, Robert R.

    2017-01-01

    When an optical pulse propagates along an optical fibre, different wavelengths travel at different group velocities. As a result, wavelength information is converted into arrival-time information, a process known as wavelength-to-time mapping. This phenomenon is most cleanly observed using a single-mode fibre transmission line, where spatial mode dispersion is not present, but the use of such fibres restricts possible applications. Here we demonstrate that photonic lanterns based on tapered single-mode multicore fibres provide an efficient way to couple multimode light to an array of single-photon avalanche detectors, each of which has its own time-to-digital converter for time-correlated single-photon counting. Exploiting this capability, we demonstrate the multiplexed single-mode wavelength-to-time mapping of multimode light using a multicore fibre photonic lantern with 121 single-mode cores, coupled to 121 detectors on a 32 × 32 detector array. This work paves the way to efficient multimode wavelength-to-time mapping systems with the spectral performance of single-mode systems.

  9. Experimental sliding mode control of a flexible single link manipulator

    NASA Astrophysics Data System (ADS)

    Qian, Timothy Wei Tie

    1993-09-01

    A study was conducted to explore and develop practical controller designs for a flexible manipulator based on the variable structure (VS) system and sliding mode (SM) theory. A new control design method is first proposed based on the continuous time VSSM theory, which can significantly simplify the VS system design process. Moreover, the variables concerned can be assigned separate gains. Direct application of the VSSM control system to the flexible arm, however, has limitations due to the inherent properties of the system. To solve this problem, facilitate digital implementation, and eliminate undesirable chattering in conventional VS system control, the discrete time quasi sliding mode control (DQSMC) is developed. Two control algorithms are derived satisfying the conditions for existence of discrete time sliding hypersurfaces. It is proven that the DQSMC design is equivalent to a full state feedback with its steady state motion constrained to the sliding hypersurfaces, and that DQSMC provides a general structure unifying the three different kinds of discrete time SM control. Experimental testing of the DQSMC controller showed good results, which compared favorably to the linear quadratic Gaussian controller under the same load variations. A novel approach was then devised to realize the proposed new controller designs.

  10. ALPD technology from PCS to single-mode

    NASA Astrophysics Data System (ADS)

    Wurier, B.

    1986-04-01

    We review the historical development of silica deposition methods using an atmospheric pressure plasma torch, from the Verneuil process for optical grade fused silica ingots to the Axial Lateral Plasma Deposition (ALPD) process for single and multimode fiber production. The present status of ALPD is presented, with special emphasis on index profile control, OH reduction and multiple ingot to preform pulling.

  11. Single-mode waveguide optical isolator based on direction-dependent cutoff frequency.

    PubMed

    Tang, Lingling; Drezdzon, Samuel M; Yoshie, Tomoyuki

    2008-09-29

    A single-mode-waveguide optical isolator based on propagation direction dependent cut-off frequency is proposed. The isolation bandwidth is the difference between the cut-off frequencies of the lowest forward and backward propagating modes. Perturbation theory is used for analyzing the correlation between the material distribution and the bandwidth. The mode profile determines an appropriate distribution of non-reciprocal materials.

  12. Large-mode-area single-mode-output Neodymium-doped silicate glass all-solid photonic crystal fiber.

    PubMed

    Li, Wentao; Chen, Danping; Qinling, Zhou; Hu, Lili

    2015-07-24

    We have demonstrated a 45 μm core diameter Neodymium-doped all-solid silicate glass photonic crystal fiber laser with a single mode laser output. The structure parameters and modes information of the fiber are both demonstrated by theoretical calculations using Finite Difference Time Domain (FDTD) method and experimental measurements. Maximum 0.8 W output power limited by launched pump power has been generated in 1064 nm with laser beam quality factor M(2) 1.18.

  13. Large-mode-area single-mode-output Neodymium-doped silicate glass all-solid photonic crystal fiber

    PubMed Central

    Li, Wentao; Chen, Danping; Qinling, Zhou; Hu, Lili

    2015-01-01

    We have demonstrated a 45 μm core diameter Neodymium-doped all-solid silicate glass photonic crystal fiber laser with a single mode laser output. The structure parameters and modes information of the fiber are both demonstrated by theoretical calculations using Finite Difference Time Domain (FDTD) method and experimental measurements. Maximum 0.8 W output power limited by launched pump power has been generated in 1064 nm with laser beam quality factor M2 1.18. PMID:26205850

  14. Inversed Vernier effect based single-mode laser emission in coupled microdisks.

    PubMed

    Li, Meng; Zhang, Nan; Wang, Kaiyang; Li, Jiankai; Xiao, Shumin; Song, Qinghai

    2015-09-02

    Recently, on-chip single-mode laser emissions in coupled microdisks have attracted considerable research attention due to their wide applications. While most of single-mode lasers in coupled microdisks or microrings have been qualitatively explained by either Vernier effect or inversed Vernier effect, none of them have been experimentally confirmed. Here, we studied the mechanism of single-mode laser operation in coupled microdisks. We found that the mode numbers had been significantly reduced to nearly single-mode within a large pumping power range from threshold to gain saturation. The detail laser spectra showed that the largest gain and the first lasing peak were mainly generated by one disk and the laser intensity was proportional to the wavelength detuning of two set of modes. The corresponding theoretical analysis showed that the experimental observations were dominated by internal coupling within one cavity, which was similar to the recently explored inversed Vernier effect in two coupled microrings. We believe our finding will be important for understanding the previous experimental findings and the development of on-chip single-mode laser.

  15. Inversed Vernier effect based single-mode laser emission in coupled microdisks

    NASA Astrophysics Data System (ADS)

    Li, Meng; Zhang, Nan; Wang, Kaiyang; Li, Jiankai; Xiao, Shumin; Song, Qinghai

    2015-09-01

    Recently, on-chip single-mode laser emissions in coupled microdisks have attracted considerable research attention due to their wide applications. While most of single-mode lasers in coupled microdisks or microrings have been qualitatively explained by either Vernier effect or inversed Vernier effect, none of them have been experimentally confirmed. Here, we studied the mechanism of single-mode laser operation in coupled microdisks. We found that the mode numbers had been significantly reduced to nearly single-mode within a large pumping power range from threshold to gain saturation. The detail laser spectra showed that the largest gain and the first lasing peak were mainly generated by one disk and the laser intensity was proportional to the wavelength detuning of two set of modes. The corresponding theoretical analysis showed that the experimental observations were dominated by internal coupling within one cavity, which was similar to the recently explored inversed Vernier effect in two coupled microrings. We believe our finding will be important for understanding the previous experimental findings and the development of on-chip single-mode laser.

  16. Inversed Vernier effect based single-mode laser emission in coupled microdisks

    PubMed Central

    Li, Meng; Zhang, Nan; Wang, Kaiyang; Li, Jiankai; Xiao, Shumin; Song, Qinghai

    2015-01-01

    Recently, on-chip single-mode laser emissions in coupled microdisks have attracted considerable research attention due to their wide applications. While most of single-mode lasers in coupled microdisks or microrings have been qualitatively explained by either Vernier effect or inversed Vernier effect, none of them have been experimentally confirmed. Here, we studied the mechanism of single-mode laser operation in coupled microdisks. We found that the mode numbers had been significantly reduced to nearly single-mode within a large pumping power range from threshold to gain saturation. The detail laser spectra showed that the largest gain and the first lasing peak were mainly generated by one disk and the laser intensity was proportional to the wavelength detuning of two set of modes. The corresponding theoretical analysis showed that the experimental observations were dominated by internal coupling within one cavity, which was similar to the recently explored inversed Vernier effect in two coupled microrings. We believe our finding will be important for understanding the previous experimental findings and the development of on-chip single-mode laser. PMID:26330218

  17. Attenuation coefficient of single-mode periodic waveguides.

    PubMed

    Baron, A; Mazoyer, S; Smigaj, W; Lalanne, P

    2011-10-07

    It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient α=-⟨ln(T)⟩/L. In this Letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result, that contradicts common beliefs and experimental practices aiming at measuring α, is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviors.

  18. Attenuation Coefficient of Single-Mode Periodic Waveguides

    NASA Astrophysics Data System (ADS)

    Baron, A.; Mazoyer, S.; Smigaj, W.; Lalanne, P.

    2011-10-01

    It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient α=-⟨ln⁡(T)⟩/L. In this Letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result, that contradicts common beliefs and experimental practices aiming at measuring α, is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviors.

  19. Inactivation of single cardiac Na+ channels in three different gating modes.

    PubMed Central

    Böhle, T; Steinbis, M; Biskup, C; Koopmann, R; Benndorf, K

    1998-01-01

    In small cell-attached patches containing one and only one Na+ channel, inactivation was studied in three different gating modes, namely, the fast-inactivating F mode and the more slowly inactivating S mode and P mode with similar inactivation kinetics. In each of these modes, ensemble-averaged currents could be fitted with a Hodgkin-Huxley-type model with a single exponential for inactivation (tauh). tauh declined from 1.0 ms at -60 mV to 0.1 ms at 0 mV in the F mode, from 4.6 ms at -40 mV to 1.1 ms at 0 mV in the S mode, and from 4.5 ms at -40 mV to 0.8 ms at +20 mV in the P mode, respectively. The probability of non-empty traces (net), the mean number of openings per non-empty trace (op/tr), and the mean open probability per trace (popen) were evaluated at 4-ms test pulses. net inclined from 30% at -60 mV to 63% at 0 mV in the F mode, from 4% at -90 mV to 90% at 0 mV in the S mode, and from 2% at -60 mV to 79% at +20 mV in the P mode. op/tr declined from 1.4 at -60 mV to 1.1 at 0 mV in the F mode, from 4.0 at -60 mV to 1.2 at 0 mV in the S mode, and from 2.9 at -40 mV to 1.6 at +20 mV in the P mode. popen was bell-shaped with a maximum of 5% at -30 mV in the F mode, 48% at -50 mV in the S mode, and 16% at 0 mV in the P mode. It is concluded that 1) a switch between F and S modes may reflect a functional change of inactivation, 2) a switch between S and P modes may reflect a functional change of activation, 3) tauh is mainly determined by the latency until the first channel opening in the F mode and by the number of reopenings in the S and P modes, 4) at least in the S and P modes, inactivation is independent of pore opening, and 5) in the S mode, mainly open channels inactivate, and in the P mode, mainly closed channels inactivate. PMID:9746515

  20. Single-mode fiber optics in a long-baseline interferometer.

    PubMed

    Shaklan, S B; Roddier, F

    1987-06-01

    We have investigated the potential for using single-mode fiber optics to link two or more telescopes in a large optical to near-IR astronomical interferometer. On an optical bench, we observed the effects of dispersion, temperature, and birefringence on wide-bandwidth interference fringes using up to 30 m of single-mode fiber in each arm of a Twyman-Green interferometer.

  1. Nozzle design yielding interferometrically flat fluid jets for use in single-mode dye lasers

    SciTech Connect

    Haerri, H.; Leutwyler, S.; Schumacher, E.

    1982-12-01

    Fundamentals and design principles are presented for the generation of interferometrically flat jets of viscous fluids. The jet quality is optically analyzed and nozzle performance investigated in cw single-mode dye laser operation. A nozzle providing a dye jet with an optically flat area of 9 mm/sup 2/ is described. It produces a single-mode bandwidth of approx.5 MHz without any active stabilization.

  2. Modeling and analysis of fiber-optic mode transducers - Single fiber with periodic perturbations

    NASA Astrophysics Data System (ADS)

    Huang, Weiping; Xu, Chenglin; Chaudhuri, Sujeet K.

    1991-11-01

    The fiber-optic LP01-LP11 mode transducers are analyzed by a scalar coupled-mode theory with vector correction. The authors deal with fiber-optic mode transducers made of a single fiber with periodic perturbations due to microbends, acoustic waves, or a photoinduced index grating. Both the couplings caused by the index perturbations and by the vector property of the fields (polarization effect) are taken into account in the analysis. Approximate analytical solutions to the coupled-mode equations are obtained. The power exchange among the modes along the fiber and spectral properties of the mode transducers are examined. The functions of the mode transducers used as wavelength filters and polarizers are studied.

  3. Orthogonality breaking induces extraordinary single-mode transparency in an elaborate waveguide with wall corrugations

    PubMed Central

    Tao, Zhi-Yong; Fan, Ya-Xian

    2014-01-01

    Orthogonality plays a fundamental role in various mathematical theorems and in physics. The orthogonal eigenfunctions that represent the intrinsic motions of various physical systems can also be regarded as transverse wave modes in a straight waveguide. Because of their orthogonality, these modes propagate independently, without mutual interference. When the wall separation fluctuates, the former mode orthogonality is destroyed because of the change in the Euclidean space of the system. Here, we experimentally demonstrate the extraordinary single-mode transparency that arises as a result of the intense mode interference induced by orthogonality breaking in a waveguide with a varying cross section. A mode diagram is also introduced to illuminate these mode interactions. In particular, measurements of the transverse field distributions indicate that a three-mode interaction leads to a single high-order mode that penetrates through the lower-mode bandgaps when the wall period is carefully selected. The observation of Bessel-like transverse distributions is promising for applications in wave-control engineering. PMID:25403089

  4. Second-harmonic generation in single-mode integrated waveguides based on mode-shape modulation

    NASA Astrophysics Data System (ADS)

    Rao, Ashutosh; Chiles, Jeff; Khan, Saeed; Toroghi, Seyfollah; Malinowski, Marcin; Camacho-González, Guillermo Fernando; Fathpour, Sasan

    2017-03-01

    Second-harmonic generation is demonstrated using grating-assisted quasi-phase matching, based on waveguide-width modulation or mode-shape modulation. Applicable to any thin-film integrated second-order nonlinear waveguide, the technique is demonstrated in compact lithium niobate ridge waveguides. Fabricated devices are characterized with pulsed-pumping in the near-infrared, showing second-harmonic generation at a signal wavelength of 784 nm and propagation loss of 1 dB/cm.

  5. Production of single-mode fibres with negligible intrinsic birefringence and polarisation mode dispersion

    NASA Astrophysics Data System (ADS)

    Barlow, A. J.; Payne, D. N.; Hadley, M. R.; Mansfield, R. J.

    1981-10-01

    A method is reported whereby fibers can be reproducibly manufactured with negligible intrinsic birefringence or polarization mode dispersion (less than 0.02 ps/km). The fibers are produced by rotating the preform during drawing to impact a permanent twist and are referred to as spun fibers to distinguish them from fibers twisted after drawing. Such fibers will find application in the Faraday current monitor and for high-bandwidth telecommunications.

  6. In-line fiber optic interferometric sensors in single-mode fibers.

    PubMed

    Zhu, Tao; Wu, Di; Liu, Min; Duan, De-Wen

    2012-01-01

    In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented.

  7. 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.

  8. The geometry and frequency content of planetary gear single-mode vibration

    NASA Astrophysics Data System (ADS)

    Cooley, Christopher G.; Parker, Robert G.

    2013-10-01

    The geometry and frequency content of single-mode vibrations of spur planetary gears are investigated in the rotating carrier-fixed and the stationary reference frames. Planetary gears with equally spaced or diametrically opposed planets have exactly three mode types, called planet, rotational, and translational modes. The properties of these vibration modes lead to response with well-defined geometry. The frequency content of the motion differs between the rotating carrier-fixed and stationary bases. The results from this work assist the analysis of experimental planetary gear measurements.

  9. Direct dark mode excitation by symmetry matching of a single-particle-based metasurface

    NASA Astrophysics Data System (ADS)

    Burokur, Shah Nawaz; Lupu, Anatole; de Lustrac, André

    2015-01-01

    This paper provides evidence for a direct dark mode excitation mechanism in a metasurface structure. The dark mode excitation mechanism is entirely determined by structures' symmetry and does not depend on near-field coupling between elements. In our examples, we consider single-element based metasurface composed of two V antennas connected in an antisymmetric arrangement. Both experimental and modeling results show an efficient excitation of magnetic dipolar mode in such structures. The direct dark mode excitation mechanism provides a design that is more robust with respect to technology imperfections. The considered approach opens promising perspectives for new types of nanostructure designs and greatly relaxes fabrication constraints for the optical domain.

  10. Reliability of single-mode and multi-mode high-power semiconductor lasers at eye-safe wavelengths

    NASA Astrophysics Data System (ADS)

    Stakelon, T.; Lucas, J.; Osowski, M.; Lammert, R.; Moon, S.; Panja, C.; Elarde, V.; Gallup, K.; Hu, W.; Ungar, J.

    2009-02-01

    High power semiconductor lasers with wavelengths in the eye-safer region have application to a variety of defense, medical and industrial applications. We report on the reliability of high power multimode and single mode InGaAsP/InP diode lasers with wavelengths in the range 1320 to 1550 nm in a variety of configurations, including single-chip, conduction-cooled arrays, arrays incorporating internal diffraction gratings, master-oscillator power amplifiers, and fiber-coupled modules of the above. In all cases we show very low rates of degradation in optical power and the absence of sudden failure from catastrophic optical damage or from laser-package interactions.

  11. Celiac disease biodetection using lossy-mode resonances generated in tapered single-mode optical fibers

    NASA Astrophysics Data System (ADS)

    Socorro, A. B.; Corres, J. M.; Del Villar, I.; Matias, I. R.; Arregui, F. J.

    2014-05-01

    This work presents the development and test of an anti-gliadin antibodies biosensor based on lossy mode resonances (LMRs) to detect celiac disease. Several polyelectrolites were used to perform layer-by-layer assembly processes in order to generate the LMR and to fabricate a gliadin-embedded thin-film. The LMR shifted 20 nm when immersed in a 5 ppm anti-gliadin antibodies-PBS solution, what makes this bioprobe suitable for detecting celiac disease. This is the first time, to our knowledge, that LMRs are used to detect celiac disease and these results suppose promising prospects on the use of such phenomena as biological detectors.

  12. Quantum correlations of helicity entangled states in non-inertial frames beyond single mode approximation

    SciTech Connect

    Harsij, Zeynab Mirza, Behrouz

    2014-12-15

    A helicity entangled tripartite state is considered in which the degree of entanglement is preserved in non-inertial frames. It is shown that Quantum Entanglement remains observer independent. As another measure of quantum correlation, Quantum Discord has been investigated. It is explicitly shown that acceleration has no effect on the degree of quantum correlation for the bipartite and tripartite helicity entangled states. Geometric Quantum Discord as a Hilbert–Schmidt distance is computed for helicity entangled states. It is shown that living in non-inertial frames does not make any influence on this distance, either. In addition, the analysis has been extended beyond single mode approximation to show that acceleration does not have any impact on the quantum features in the limit beyond the single mode. As an interesting result, while the density matrix depends on the right and left Unruh modes, the Negativity as a measure of Quantum Entanglement remains constant. Also, Quantum Discord does not change beyond single mode approximation. - Highlights: • The helicity entangled states here are observer independent in non-inertial frames. • It is explicitly shown that Quantum Discord for these states is observer independent. • Geometric Quantum Discord is also not affected by acceleration increase. • Extending to beyond single mode does not change the degree of entanglement. • Beyond single mode approximation the degree of Quantum Discord is also preserved.

  13. Theoretical Analysis and Experiment on a Novel Kind of Single Mode Large-Mode Erbium-Doped Fiber

    NASA Astrophysics Data System (ADS)

    Peng, Jian; Liu, Lisong; Wei, Huai; Sun, Jiang; Kang, Zexin; Jian, Shuisheng

    A kind of large-mode-area (LMA) erbium-doped fiber (EDF) is required to get high output power with good beam quality. This new LMA EDF has a multi-layer-core structure which makes the mode area bigger. The key process is deposition of multi-layer-core structure by using modified MCVD to make every layer of the core with different refractive index. Furthermore, the key optical specifications of the fiber are measured. The absorption peak is 10.6 dB/m at 980 nm and 20 dB/m at 1550 nm. The cutoff wavelength is about 1300 nm. The mode field diameter (MFD) is 12.6 μm and 13.2 μm at 1550 nm according to Petermann-2 and Gaussian definitions, respectively. The core diameter is about 12 μm. The MFD of conventional standard EDFs is in a limited range ~5-8 μm, so the experimental result has made a big progress for MFD. Especially, we can improve the parameters of the multi-layer-core structure to get single mode EDF with larger mode area for high power fiber laser.

  14. Refractometric sensors based on multimode interference in a thin-film coated single-mode-multimode-single-mode structure with reflection configuration.

    PubMed

    Del Villar, Ignacio; Socorro, Abian B; Corres, Jesus M; Arregui, Francisco J; Matias, Ignacio R

    2014-06-20

    Thin-film coated single-mode-multimode-single-mode (SMS) structures have been analyzed both theoretically and experimentally with the aim of detecting different refractive indices. By adequate selection of the thickness of the thin film and of the diameter of the multimode segment in the SMS structure, a seven-fold improvement can be obtained in the sensitivity of the device to the surrounding medium refractive index, achieving a maximum sensitivity of 1199.18  nm/refractive index unit for the range of refractive indices from 1.321 to 1.382. Using layer-by-layer self-assembly for deposition, both on the cladding and on the tip of the multimode segment, allows the reflected power to increase, which avoids the application of a mirror on the tip of the multimode segment.

  15. Single-molecule electronics: Cooling individual vibrational modes by the tunneling current

    NASA Astrophysics Data System (ADS)

    Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C.

    2016-03-01

    Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.

  16. Single-molecule electronics: Cooling individual vibrational modes by the tunneling current.

    PubMed

    Lykkebo, Jacob; Romano, Giuseppe; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C

    2016-03-21

    Electronic devices composed of single molecules constitute the ultimate limit in the continued downscaling of electronic components. A key challenge for single-molecule electronics is to control the temperature of these junctions. Controlling heating and cooling effects in individual vibrational modes can, in principle, be utilized to increase stability of single-molecule junctions under bias, to pump energy into particular vibrational modes to perform current-induced reactions, or to increase the resolution in inelastic electron tunneling spectroscopy by controlling the life-times of phonons in a molecule by suppressing absorption and external dissipation processes. Under bias the current and the molecule exchange energy, which typically results in heating of the molecule. However, the opposite process is also possible, where energy is extracted from the molecule by the tunneling current. Designing a molecular "heat sink" where a particular vibrational mode funnels heat out of the molecule and into the leads would be very desirable. It is even possible to imagine how the vibrational energy of the other vibrational modes could be funneled into the "cooling mode," given the right molecular design. Previous efforts to understand heating and cooling mechanisms in single molecule junctions have primarily been concerned with small models, where it is unclear which molecular systems they correspond to. In this paper, our focus is on suppressing heating and obtaining current-induced cooling in certain vibrational modes. Strategies for cooling vibrational modes in single-molecule junctions are presented, together with atomistic calculations based on those strategies. Cooling and reduced heating are observed for two different cooling schemes in calculations of atomistic single-molecule junctions.

  17. Bend-insensitive lasing characteristics of single-mode, large-mode-area ytterbium-doped photonic crystal fiber.

    PubMed

    Iizawa, K; Varshney, S K; Tsuchida, Y; Saitoh, K; Koshiba, M

    2008-01-21

    The bend-insensitive lasing characteristics of a newly designed ytterbium-doped photonic crystal fiber (YPCF) are evaluated numerically. The designed YPCF remains single-mode and possesses large-mode-area of 1400 microm(2) at 1064 nm wavelength with the beam quality factor (M(2)) of 1.15, suggesting a diffraction-limited and continuous-wave lasing operation. The doped-region size is optimized for maximum conversion efficiency and it is found through numerical simulations that the doped radius should be more than 21 microm. The "mode expansion", which is the self-expansion of the fundamental mode within the doped region with wavelength increments on bending the fiber, is the basic physical mechanism to give the bend-insensitive lasing performances of YPCF. It leads to an unusual variation of overlap factor when the wavelength is increased. A 41 cm long piece of YPCF demonstrates more than 83% of slope efficiency with 75% of conversion efficiency when pumped with a 975 nm laser source delivering an input power of 1 W.

  18. Endlessly single-mode photonic crystal fiber as a high resolution probe.

    PubMed

    Valtna-Lukner, Heli; Repän, Jaagup; Valdma, Sandhra-Mirella; Piksarv, Peeter

    2016-11-20

    We sample ultra-broadband light, focused onto a diffraction-limited spot, to an endlessly single-mode photonic crystal fiber (ESM) and detect both the field amplitude and phase using a SEA TADPOLE interferometer. We resolve spatial features up to 2.5 times finer than the fiber mode size while sampling the periodic features of the bipolar oscillating field in the transverse section. The resolution enhancement is expected also in other types of single-mode fibers in intensity measurements and leads to an inexpensive method for characterizing the point-spread function of such optical fields, e.g., diffraction-limited spots from microscope objectives. In addition, we demonstrate the guidance of a high-NA light field in the fine structure of an ESM fiber mode. The results are especially valuable for devices where a fiber tip acts as an input slit and defines the spatial resolution, e.g., fiber-based interferometers, spectrometers, and sensors.

  19. Non-Geiger mode single photon detector with multiple amplification and gain control mechanisms

    SciTech Connect

    Nawar Rahman, Samia Hall, David; Lo, Yu-Hwa

    2014-05-07

    A new type of single photon detector, Multiple Amplification Gain with Internal Control (MAGIC), is proposed and analyzed using Monte Carlo simulations based on a physical model of the device. The MAGIC detector has two coupled amplification mechanisms, avalanche multiplication and bipolar gain, and the net gain is regulated by a built-in feedback mechanism. Compared to conventional Geiger mode single photon avalanche detectors (SPADs), the MAGIC detector produces a much greater single photon detection efficiency of nearly 100%, low bit-error-ratio for single photon signals, and a large dynamic range. All these properties are highly desirable for applications that require single photon sensitivity and are absent for conventional Geiger-mode SPADs.

  20. Analysis of ring-structured Bragg fibres for single TE mode guidance

    NASA Astrophysics Data System (ADS)

    Argyros, Alexander; Bassett, Ian M.; van Eijkelenborg, Martijn A.; Large, Maryanne C. J.

    2004-06-01

    Ring-structured Bragg fibres that support a single TE-polarisation mode are investigated. The fibre designs consist of a hollow core and rings of holes concentric with the core, which form the low-index layers of the Bragg reflector in the cladding. The effects of varying the air fraction in each ring of holes on the transmission properties of the fibres are analysed and an approximate model based on homogenisation is explored. Surface modes and transitions thereof are also discussed.

  1. 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

  2. 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.

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

    SciTech Connect

    Egorova, O N; Semenov, S L; Vel'miskin, V V; Dianov, Evgenii M; Salganskii, M Yu; Yashkov, M V; Gur'yanov, Aleksei N

    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)

  4. Technology and engineering aspects of high power pulsed single longitudinal mode dye lasers

    NASA Astrophysics Data System (ADS)

    Rawat, V. S.; Mukherjee, Jaya; Gantayet, L. M.

    2015-09-01

    Tunable single mode pulsed dye lasers are capable of generating optical radiations in the visible range having very small bandwidths (transform limited), high average power (a few kW) at a high pulse repetition rate (a few tens of kHz), small beam divergence and relatively higher efficiencies. These dye lasers are generally utilized laser dyes dissolved in solvents such as water, heavy water, ethanol, methanol, etc. to provide a rapidly flowing gain medium. The dye laser is a versatile tool, which can lase either in the continuous wave (CW) or in the pulsed mode with pulse duration as small as a few tens of femtoseconds. In this review, we have examined the several cavity designs, various types of gain mediums and numerous types of dye cell geometries for obtaining the single longitudinal mode pulsed dye laser. Different types of cavity configuration, such as very short cavity, short cavity with frequency selective element and relatively longer cavity with multiple frequency selective elements were reviewed. These single mode lasers have been pumped by all kinds of pumping sources such as flash lamps, Excimer, Nitrogen, Ruby, Nd:YAG, Copper Bromide and Copper Vapor Lasers. The single mode dye lasers are either pumped transversely or longitudinally to the resonator axis. The pulse repletion rate of these pump lasers were ranging from a few Hz to a few tens of kHz. Physics technology and engineering aspects of tuning mechanism, mode hop free scanning and dye cell designs are also presented in this review. Tuning of a single mode dye laser with a resolution of a few MHz per step is a technologically challenging task, which is discussed here.

  5. Signal beating elimination using single-mode fiber to multimode fiber coupling.

    PubMed

    Fok, Mable P; Deng, Yanhua; Kravtsov, Konstantin; Prucnal, Paul R

    2011-12-01

    We experimentally demonstrate an all-passive fiber-based approach to prevent undesired beating during signal merging and detection. Beating occurs when optical signals of very close or the same wavelength are combined at a coupler and detected using a photodetector. Our approach is based on signal coupling from several single-mode fibers to a single piece of multimode fiber without interference, such that different signals propagate in different modes with different spatial positions inside the multimode fiber. We have investigated signal beating when the signals are coherent, partially coherent, or incoherent with each other. The measured results for single-mode to multimode coupling show signal beating is substantially reduced, resulting in widely opened eye diagrams and error-free bit error rate performance.

  6. High-sensitivity ultrasound interferometric single-mode polymer optical fiber sensors for biomedical applications.

    PubMed

    Gallego, Daniel; Lamela, Horacio

    2009-06-15

    This work describes the results of ultrasonic wideband sensors based on single-mode polymer optical fibers that may be used for biomedical applications. We have compared the ultrasonic sensitivities of two Mach-Zehnder interferometric intrinsic optical fiber sensors. One is based on a single-mode polymethylmethacrylate optical fiber and the second on single-mode silica optical fiber, both operating at 632.8 nm. At a frequency of 1 MHz these sensitivities are 13.1 and 0.85 mrad/kPa, respectively. The ultrasonic phase sensitivity of the polymer optical fiber is more than 12 times larger than that from the fused silica fiber in the 1-5 MHz range.

  7. Selection of lasing direction in single mode semiconductor square ring cavities

    SciTech Connect

    Lee, Jin-Woong; Kim, Kyoung-Youm; Moon, Hee-Jong; Hyun, Kyung-Sook

    2016-02-07

    We propose and demonstrate a selection scheme of lasing direction by imposing a loss imbalance structure into the single mode square ring cavity. The control of the traveling direction is realized by introducing a taper-step section in one of the straight waveguides of the square ring cavity. It was shown by semi-analytic calculation that the taper-step section in the cavity provides effective loss imbalance between two travelling directions as the round trip repeats. Various kinds of square cavities were fabricated using InGaAsP/InGaAs multiple quantum well semiconductor materials in order to test the direction selectivity while maintaining the single mode. We also measured the pump power dependent lasing spectra to investigate the maintenance property of the lasing direction. The experimental results demonstrated that the proposed scheme is an efficient means for a unidirectional lasing in a single mode laser.

  8. Development of a 10-decade single-mode reactor flux monitoring system

    SciTech Connect

    Valentine, K.H.; Shepard, R.L.; Falter, K.G.; Reese, W.B.

    1988-03-31

    Conventional wide-range neutron channels employ three optional modes to monitor the required flux range from source levels to full power (typically 10 or more decades). Difficult calibrations are necessary to provide a continuous output signal when such a system switches from counting mode in the source range to mean-square voltage mode in the midrange to dc current mode in the power range. In an ORNL proof-of-principle test, a method of extended range counting was implemented with a fission counter and conventional wide-band pulse processing electronics to provide a single-mode, monotonically increasing signal that spanned /approximately 10/ decades of neutron flux. Ongoing work includes design, fabrication, and testing of a comlpete neutron flux monitoring system suitable for advanced liquid metal reactor designs. 6 refs., 4 figs.

  9. Asymptotically single-mode small-core terahertz Bragg fibre with low loss and low dispersion

    NASA Astrophysics Data System (ADS)

    Hong, B.; Swithenbank, M.; Somjit, N.; Cunningham, J.; Robertson, I.

    2017-02-01

    This paper presents a novel design concept, which is verified by analytical and simulation results, of a single-mode small-core terahertz Bragg fibre exhibiting the properties of low loss and low dispersion. Conventionally, a single-TE01-mode Bragg fibre requires a large core and many cladding layer periods to achieve a significant propagation loss discrimination between the desired mode and other unwanted competing modes. The use of a second-order bandgap in this paper completely eliminates this requirement, and enhances propagation loss discrimination using just a small core with a diameter at least 50% smaller than the conventional design and only four cladding layer periods. Furthermore, a generalized half-wavelength condition is proposed, promoting the manipulation of photonic bandgap for Bragg fibre. The TE01 mode has a null point in the electric field close to the boundary interface between the core and the cladding, and this phenomenon has been exploited to minimize the impact of support bridges, which mechanically maintain the air gaps, on the propagation loss of the fibre. Finally, we propose a novel design of a tightly confined single-TE01-mode small-air-core Bragg fibre with propagation loss and group velocity dispersion less than 1.2 dB m-1 and  -0.6 ps/THz/cm, respectively, between frequencies of 0.85 THz and 1.15 THz.

  10. High-power single-transverse-mode holey VCSELs (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Furukawa, Akio; Hoshi, Mitsunari; Sasaki, Satoshi; Matsuzono, Atsushi; Moritoh, Kosuke; Baba, Toshihiko

    2005-04-01

    By introducing triangular holes into oxide confined 850nm monolithic vertical-cavity surface-emitting lasers (VCSELs), single-transverse-mode operation has been obtained for large oxide apertures of 14-15 microns. The two-dimensional triangular holes etched on the device surface were aligned circumferentially along the aperture perimeter, with their tips surrounding the device center. When the holes had a relatively large lateral penetration into the oxide aperture, the holey VCSEL lased with a single spot near field pattern with a high side-mode suppression ratio (SMSR) of 45-50dB, and an output power of 2mW. In this case, it is assumed that the triangular holes are acting as a highly mode selective loss mechanism. On the other hand, when the penetration of the holes was relatively small, an SMSR of 40dB was obtained from a large area "floral" near field pattern, with a record high single-mode output power of 7mW. The lasing spectrum and far field intensity profile of this "floral" type emission indicates that it is a somewhat deformed fundamental mode that is extending over the whole device, and oscillating in-phase. The ability of triangular holes to suppress high order modes in large area oxide confined VCSELs should be effective for systems with wavelengths other than 850nm as well.

  11. Low-nonlinearity single-transverse-mode ytterbium-doped photonic crystal fiber amplifier.

    PubMed

    Limpert, J; Liem, A; Reich, M; Schreiber, T; Nolte, S; Zellmer, H; Tünnermann, A; Broeng, J; Petersson, A; Jakobsen, C

    2004-04-05

    We report on an air-clad large-core single-transverse-mode ytterbium-doped photonic crystal fiber with a mode-field-diameter of 35 microm, corresponding to a mode-field-area of ~1000 microm(2). In a first experiment this fiber is used to amplify 10-ps pulses to a peak power of 60 kW without significant spectral broadening due to self-phase modulation allowing for the frequency up-conversion of these pulses using narrow-bandwidth phase matched nonlinear crystals.

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

    SciTech Connect

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

    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 electrolysis 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.

  13. Single-mode hole-assisted fiber as a bending-loss insensitive fiber

    NASA Astrophysics Data System (ADS)

    Nakajima, Kazuhide; Shimizu, Tomoya; Matsui, Takashi; Fukai, Chisato; Kurashima, Toshio

    2010-12-01

    We investigate the design and characteristics of a single-mode and low bending loss HAF both numerically and experimentally. An air filling fraction S is introduced to enable us to design a HAF with desired characteristics more easily. We show that we can expect to realize a single-mode and low bending loss HAF by considering the S dependence of the bending loss α b and cutoff wavelength λ c as well as their relative index difference Δ dependence. We also show that the mode-field diameter (MFD) and chromatic dispersion characteristics of the single-mode and low bending loss HAF can be tailored by optimizing the distance between the core and the air holes. We also investigate the usefulness of the fabricated HAFs taking the directly modulated transmission and multipath interference (MPI) characteristics into consideration. We show that the designed HAF has sufficient applicability to both analog and digital transmission systems. Our results reveal that the single-mode and low bending loss HAF is beneficial in terms of developing a future fiber to the home (FTTH) network as well as for realizing flexible optical wiring.

  14. Beam Wiggler operating in high frequency and single-pulse modes

    NASA Astrophysics Data System (ADS)

    Goltsov, A. Y.; Kolomiysky, Arkadiy N.; Kovalsky, N. G.; Kryzhko, V. V.; Manes, Kenneth R.; Pergament, Michael I.

    1999-07-01

    The possibility to control an intensity distribution in the far field of a powerful laser system by rapid motion of a focal spot is considered. Quadruple electro optic deflector on the base of LiNgO3 crystal installed in resonance capacity with 1 cm clear aperture has been developed, constructed and tested both in high frequency and single pulse operation modes. The main parameters of the device are as follows: amplitude of the angular deflection +/- 4 dif. limits at 6.5 GHz operation frequency, total angular deflection 12 dif. limits in the single ns-pulse operation mode. Results of the Beam Wiggler dynamic testing are presented and discussed.

  15. Single-longitudinal-mode erbium-doped fiber laser with multiple linear cavity

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Ren, Wenhua; Jian, Shuisheng

    2008-12-01

    An improved stable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser with multiple-linear short cavity is demonstrated. Three fiber Bragg gratings (FBGs) with the same parameters directly written in a homemade photosensitive EDF (PEDF) in a single step are used as the wavelength-selective and mode-selective component in a 14 cm long linear laser cavity. The optical signal-to-noise ratio (OSNR) is over 50 dB. The amplitude variation in nearly one hour is less than 0.3 dB. The proposed laser has the advantages such as simple fabrication and compact all-optical fiber configuration.

  16. Polarised spectroscopy of individual single-wall nanotubes: Radial-breathing mode study

    NASA Astrophysics Data System (ADS)

    Azoulay, J.; Débarre, A.; Richard, A.; Tchénio, P.; Bandow, S.; Iijima, S.

    2001-02-01

    Polarised Raman spectroscopy is performed in a randomly distributed single-wall carbon tube (SWNT) sample at the scale of an individual single-wall nanotube. A detailed analysis in the radial-breathing mode (RBM) domain is presented. Selection of either a single tiny rope of SWNTs or of a single SWNT results from the conjugated high spatial selection of confocal microscopy, surface-enhanced Raman spectroscopy (SERS) and sample dilution. The drastic modifications observed in the low-frequency Raman spectra as a function of the polarisation configuration confirm the theoretical results.

  17. Wigner spectrum and coherent feedback control of continuous-mode single-photon Fock states

    NASA Astrophysics Data System (ADS)

    Dong, Zhiyuan; Cui, Lei; Zhang, Guofeng; Fu, Hongchen

    2016-10-01

    Single photons are very useful resources in quantum information science. In real applications it is often required that the photons have a well-defined spectral (or equivalently temporal) modal structure. For example, a rising exponential pulse is able to fully excite a two-level atom while a Gaussian pulse cannot. This motivates the study of continuous-mode single-photon Fock states. Such states are characterized by a spectral (or temporal) pulse shape. In this paper we investigate the statistical property of continuous-mode single-photon Fock states. Instead of the commonly used normal ordering (Wick order), the tool we proposed is the Wigner spectrum. The Wigner spectrum has two advantages: (1) it allows to study continuous-mode single-photon Fock states in the time domain and frequency domain simultaneously; (2) because it can deal with the Dirac delta function directly, it has the potential to provide more information than the normal ordering where the Dirac delta function is always discarded. We also show how various control methods in particular coherent feedback control can be used to manipulate the pulse shapes of continuous-mode single-photon Fock states.

  18. Single-mode and high power waveguide lasers fabricated by ion-exchange.

    PubMed

    Della Valle, G; Festa, A; Sorbello, G; Ennser, K; Cassagnetes, C; Barbier, D; Taccheo, S

    2008-08-04

    We report on a single-end diode-pumped waveguide laser providing output power in excess of 20 mW with 17% slope efficiency in robust single longitudinal and transverse mode operation at 1533.5 nm. The active medium was an Er:Yb-doped waveguide only 9-mm long fabricated by Ag-Na ion-exchange in a phosphate glass. The overall cavity length including butt-coupled fiber-Bragg-grating mirrors was <60 mm. We also report on high power waveguide lasers providing more than 160 mW output power and 46% slope efficiency in multimode operation. Feasibility of high power single mode waveguide lasers based on ion-exchange technology in phosphate glasses is also experimentally investigated by using a 50-mm long active waveguide specially designed for efficient single-end pumping.

  19. Broad-stripe single longitudinal mode laser based on metal slots

    NASA Astrophysics Data System (ADS)

    Jia, Peng; Qin, Li; Chen, Yongyi; Zhang, Jianwei; Zhang, Jian; Zhang, Xing; Zeng, Yugang; Shan, Xiaonan; Ning, Yongqiang; Wang, Lijun

    2016-04-01

    Single-longitudinal-mode end-emitting laser with 10 periods of metal slots at around 956 nm has been fabricated. 100 μm wide broad-stripe and ten periods of 9.5 μm periodicity metal slots are defined by i-line lithography and dry etching. Experimentally, continuous-wave power of 213 mW has achieved, at a slope efficiency of 520 mW/A, having a 3 dB spectrum width of less than 0.04 nm at 900 mA, and operating in a stable single longitudinal mode with the side-mode suppression ratio (SMSR) of 42 dB. We prove that metal slots introduce sufficient loss into the cavity to filter out the wanted mode, and is more efficient on our chip structure than traditional slot laser. This paper provides a new method for the realizing high power broad-stripe (~100 μm) laser and array with single longitudinal mode operation.

  20. Single mode fiber array for planet detection using a visible nulling interferometer

    NASA Technical Reports Server (NTRS)

    Liu, Duncan; Levine, B. Martin; Shao, Michael; Aguayo, Franciso

    2005-01-01

    We report the design, fabrication, and testing of a coherent large mode field diameter fiber array to be used as a spatial filter in a planet finding visible nulling interferometer. The array is a key component of a space instrument for visible-light detection and spectroscopy of Earth like extrasolar planets. In this concept, a nulling interferometer is synthesized from a pupil image of a single aperture which is then spatially filtered by a coherent array of single mode fibers to suppress the residual scattered star light. The use of the fiber array preserves spatial information between the star and planet. The fiber array uses a custom commercial large mode field or low NA step-index single mode fiber to relax alignment tolerances. A matching custom micro lens array is used to couple light into the fibers, and to recollimate the light out of the fiber array. The use of large mode field diameter fiber makes the fabrication of a large spatial filter array with 300 to 1000 elements feasible.

  1. Acoustic performance of inlet suppressors on an engine generating a single mode

    NASA Technical Reports Server (NTRS)

    Heidelberg, L. J.; Rice, E. J.; Homyak, L.

    1981-01-01

    Three single degree of freedom liners with different open area ratio face sheets were designed for a single spinning mode in order to evaluate an inlet suppressor design method based on mode cutoff ratio. This mode was generated by placing 41 rods in front of the 28 blade fan of a JT15D turbofan engine. At the liner design this near cutoff mode has a theoretical maximum attenuation of nearly 200 dB per L/D. The data show even higher attenuations at the design condition than predicted by the theory for dissipation of a single mode within the liner. This additional attenuation is large for high open area ratios and should be accounted for in the theory. The data show the additional attenuation to be inversely proportional to acoustic resistance. It was thought that the additional attenuation could be caused by reflection and modal scattering at the hard to soft wall interface. A reflection model was developed, and then modified to fit the data. This model was checked against independent (multiple pure tone) data with good agreement.

  2. Optical properties of wide single-mode strip and grating loaded channel waveguides

    SciTech Connect

    Tsarev, Andrei V

    2009-12-31

    New wide single-mode strip and grating loaded (SGL) channel waveguides made of silicon nitride on the oxide buffer layer of a planar silicon-on-insulator waveguide are studied. The central 10-lm-wide strip produces a multi-mode channel waveguide and diffraction gratings with a period 0.6 lm built on the structure edges produce mode-dependent additional losses due to radiation to the surrounding medium. The optical properties of these waveguides are discussed using the results of a three-dimensional numerical simulation by the FDTD and BPM methods. It is shown that a wide SGL waveguide is quasi-single-mode one because it has a small propagation loss ({approx} 0.3 dB cm{sup -1}) for the fundamental mode and a high (up to -20 dB cm{sup -1}) loss for the higher order modes. The new SGL waveguides are CMOS compatible and can become basic for fabricating new photonic elements, including tunable optical filters and multi-plexers based on the multireflector technology. (waveguides)

  3. Coupling of single NV center to adiabatically tapered optical single mode fiber

    NASA Astrophysics Data System (ADS)

    Vorobyov, Vadim V.; Soshenko, Vladimir V.; Bolshedvorskii, Stepan V.; Javadzade, Javid; Lebedev, Nikolay; Smolyaninov, Andrey N.; Sorokin, Vadim N.; Akimov, Alexey V.

    2016-12-01

    We demonstrated a simple and reliable technique of coupling diamond nanocrystal containing NV center to tapered optical fiber. The NV center emission was collected by the fiber via nearfield interaction between NV center and the tapered portion of the fiber. Single photon statistics was demonstrated at the fiber end as well as up to 3 times improvement in collection efficiency with respect to our confocal microscope. Also, we carefully studied fluorescence of the fiber itself and were able to suppress it to the level lower than single photon emission from the NV center.

  4. Polarization maintaining single-mode low-loss hollow-core fibres

    NASA Astrophysics Data System (ADS)

    Fini, John M.; Nicholson, Jeffrey W.; Mangan, Brian; Meng, Linli; Windeler, Robert S.; Monberg, Eric M.; Desantolo, Anthony; Dimarcello, Frank V.; Mukasa, Kazunori

    2014-10-01

    Hollow-core fibre (HCF) is a powerful technology platform offering breakthrough performance improvements in sensing, communications, higher-power pulse delivery and other applications. Free from the usual constraints on what materials can guide light, it promises qualitatively new and ideal operating regimes: precision signals transmitted free of nonlinearities, sensors that guide light directly in the samples they are meant to probe and so on. However, these fibres have not been widely adopted, largely because uncontrolled coupling between transverse and polarization modes overshadows their benefits. To deliver on their promises, HCFs must retain their unique properties while achieving the modal and polarization control that are essential for their most compelling applications. Here we present the first single-moded, polarization-maintaining HCF with large core size needed for loss scaling. Single modedness is achieved using a novel scheme for resonantly coupling out unwanted modes, whereas birefringence is engineered by fabricating an asymmetrical glass web surrounding the core.

  5. Efficient femtosecond Yb:YAG laser pumped by a single-mode laser diode

    NASA Astrophysics Data System (ADS)

    Agnesi, Antonio; Greborio, Alessandro; Pirzio, Federico; Reali, Giancarlo

    2011-08-01

    Single-mode diodes enable a particularly simple, compact and effective pumping of solid-state laser devices for many specialized applications. We investigated a single-mode, 300-mW laser diode for pumping at 935 nm a Yb:YAG laser passively mode-locked by a semiconductor saturable absorber. Relatively short pulse generation (156 fs), tunable across 1033-1059 nm has been demonstrated. An optical-to-optical efficiency of about 28% has been obtained with 320 fs long pulses. Therefore, contrarily to what previously believed, compact diode-pumped ultrafast Yb:YAG oscillators can reliably and efficiently deliver pulses in the range of ≈ 100-200 fs with few tens of mW, which are very appealing for bio-diagnostics and amplifier seeding applications.

  6. In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers

    PubMed Central

    Zhu, Tao; Wu, Di; Liu, Min; Duan, De-Wen

    2012-01-01

    In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. PMID:23112608

  7. Hybrid plasmonic-photonic mode in a subwavelength fiber for enhanced single-nanoparticle detection

    NASA Astrophysics Data System (ADS)

    Chen, You-Ling; Gong, Qihuang

    2015-01-01

    We study a hybrid mode in a composite system consisting of a localized metal nanosphere on a subwavelength fiber. It is found that the hybrid mode resulting from coupling of the fiber propagating mode and the plasmonic resonance is promising for strongly enhanced interaction between light and matter. We then propose a single-nanoparticle detection scheme by monitoring the nanofiber transmission change induced by the plasmonic-enhanced target scattering. The detection limit can be as low as 18 nm in target diameter, showing great potential for sensing single viruses or biomolecules. In the hybrid system, the resonant wavelength is tunable from visible to near-infrared spectral range by employing a metal nanoshell instead of the nanosphere, while the low detection limit of a few tens of nanometers can still remain.

  8. All-silica single-mode optical fiber with photonic crystal cladding

    NASA Astrophysics Data System (ADS)

    Knight, J. C.; Birks, T. A.; Russell, P. St. J.; Atkin, D. M.

    1996-10-01

    We report the fabrication of a new type of consists of a pure silica core surrounded by a silica-air photonic crystal material with a hexagonal symmetry. The fiber supports a single robust low-loss guided mode over a very broad spectral range of at least 458-1550 nm.

  9. Characterization of Single-Mode Chalcogenide Glass Waveguides at 8.35 μm

    SciTech Connect

    Phillips, Mark C.; Qiao, Hong; Bernacki, Bruce E.; Anheier, Norman C.

    2009-05-01

    Laser-written single-mode waveguides in As2Se3/As2S3 films were characterized at 8.35 μm using the Fabry-Perot technique. Waveguide loss and refractive index were measured as a function of writing dose and compared to modeling results.

  10. Optical Field-Strength Polarization of Two-Mode Single-Photon States

    ERIC Educational Resources Information Center

    Linares, J.; Nistal, M. C.; Barral, D.; Moreno, V.

    2010-01-01

    We present a quantum analysis of two-mode single-photon states based on the probability distributions of the optical field strength (or position quadrature) in order to describe their quantum polarization characteristics, where polarization is understood as a significative confinement of the optical field-strength values on determined regions of…

  11. On the single-photon-counting (SPC) modes of imaging using an XFEL source

    SciTech Connect

    Wang, Zhehui

    2015-12-14

    In this study, the requirements to achieve high detection efficiency (above 50%) and gigahertz (GHz) frame rate for the proposed 42-keV X-ray free-electron laser (XFEL) at Los Alamos are summarized. Direct detection scenarios using C (diamond), Si, Ge and GaAs semiconductor sensors are analyzed. Single-photon counting (SPC) mode and weak SPC mode using Si can potentially meet the efficiency and frame rate requirements and be useful to both photoelectric absorption and Compton physics as the photon energy increases. Multilayer three-dimensional (3D) detector architecture, as a possible means to realize SPC modes, is compared with the widely used two-dimensional (2D) hybrid planar electrode structure and 3D deeply entrenched electrode architecture. Demonstration of thin film cameras less than 100-μm thick with onboard thin ASICs could be an initial step to realize multilayer 3D detectors and SPC modes for XFELs.

  12. Characterization of Single-mode Chalcogenide Optical Fiber for Mid-Infrared Applications

    SciTech Connect

    Krishnaswami, Kannan; Qiao, Hong; Bernacki, Bruce E.; Anheier, Norman C.

    2009-04-01

    Chalcogenide fibers display a wide transmission window ranging from 2-10.6 μm, ideally suited to the development of passive and active mid-infrared (MIR) sensors. They are essential building blocks for the integration and miniaturization of laser-based MIR optical systems for terrestrial, airborne and space-based sensing platforms. Single-mode chalcogenide fibers have only recently become commercially available and therefore performance data and standard reproducible processing techniques have not been widely reported. In this paper we present a method for producing high quality facets on commercial single-mode As-Se fibers with core and cladding diameters of 28.1 and 169.9μm respectively. The emitted beam profile from these fibers, using the 9.4μm line of a tunable CO2 laser, showed the presence of leaky cladding modes due to waveguiding conditions created by the protective acrylate jacket. These undesirable cladding modes were easily suppressed by applying a gallium coating on the cladding near both input and output facets. We provide experimental data of efficient mode suppression and the emission of a circular near-perfect Gaussian beam profile from the fiber. A model to determine appropriate placement of gallium coatings to minimize processing while maximizing cladding mode suppression is currently underway. Furthermore, analyses of the beam, acquired by scanning an HgCdTe detector, yielded a 1/e2 numerical aperture of 0.11 with a full width half maximum divergence of 11° for these fibers. The availability of single-mode MIR fibers, in conjunction with recent advances in room temperature quantum cascade lasers (QCL), could provide compact and light-weight transmitter solutions for several critical defense and nuclear non-proliferation needs.

  13. Broad-area laser diode with stable single-mode output and wavelength stabilization

    NASA Astrophysics Data System (ADS)

    Nappez, Thomas; Ghibaudo, Elise; Rondeau, Philippe; Schlotterbeck, Jean-Pierre; Broquin, Jean-Emmanuel

    2012-01-01

    High power single-mode pump laser diodes operating around 980nm are key components for Erbium-doped devices. Much effort is still currently devoted to improve both their wavelength stability and their achievable output power, while maintaining a stable single-mode operation. Usually, the emission wavelength is stabilized by an external Fiber Bragg Grating (FBG). This configuration requires free-space optics between the laser diode output facet and the fiber or a lensed fiber to ensure an efficient coupling efficiency. This constraint increases fabrication costs, dimensions and mechanical instabilities. Moreover, the maximum achievable output power is limited because a high optical power density can damage the laser facets. To increase the achievable output power, a solution consists in using Broad-Area Laser Diodes (BALD), which are multimode emitters that are composed of large active ribbons with width of some hundreds of micrometers. The objective is then to improve the beam quality by locking the BALD emission on its transverse fundamental mode. We propose in this article to insert an integrated adiabatic transition between the multimode laser and a single-mode FBG. This taper, made by ion-exchange in glass, provides a coupling efficiency of -22.0dB from the multimode laser emission to the single-mode fiber. An optical feedback of -34dB demonstrates the stabilization of the BALD spectrum at the Bragg wavelength. The spectrum of the device is characterized by a maximum side-mode suppression ratio of 35dB, a RMS spectral width of (0.16 +/- 0.04) nm and a frequency shift with current of -12GHz/100mA.

  14. Generation of watt-level single-longitudinal-mode output from cladding-pumped short fiber lasers.

    PubMed

    Qiu, T; Suzuki, S; Schülzgen, A; Li, L; Polynkin, A; Temyanko, V; Moloney, J V; Peyghambarian, N

    2005-10-15

    We generate as much as 1.6 W of continuous-wave 1550 nm single-longitudinal-mode output from a cladding pumped Er-Yb codoped phosphate fiber laser. This power is to our knowledge among the highest in single-longitudinal-mode fiber lasers. The narrowband fiber Bragg grating output coupler is demonstrated to be an effective element for providing the single-longitudinal-mode selection.

  15. Characterization of Mid-Infrared Single Mode Fibers as Modal Filters

    NASA Technical Reports Server (NTRS)

    Ksendzov, A.; Lay, O.; Martin, S.; Sanghera, J. S.; Busse, L. E.; Kim, W. H.; Pureza, P. C.; Nguyen, V. Q.; Aggarwal, I. D.

    2007-01-01

    We present a technique for measuring the modal filtering ability of single mode fibers. The ideal modal filter rejects all input field components that have no overlap with the fundamental mode of the filter and does not attenuate the fundamental mode. We define the quality of a nonideal modal filter Q(sub f) as the ratio of transmittance for the fundamental mode to the transmittance for an input field that has no overlap with the fundamental mode. We demonstrate the technique on a 20 cm long mid-infrared fiber that was produced by the U.S. Naval Research Laboratory. The filter quality Q(sub f) for this fiber at 10.5 micron wavelength is 1000 +/- 300. The absorption and scattering losses in the fundamental mode are approximately 8 dB/m. The total transmittance for the fundamental mode, including Fresnel reflections, is 0.428 +/- 0.002. The application of interest is the search for extrasolar Earthlike planets using nulling interferometry. It requires high rejection ratios to suppress the light of a bright star, so that the faint planet becomes visible. The use of modal filters increases the rejection ratio (or, equivalently, relaxes requirements on the wavefront quality) by reducing the sensitivity to small wavefront errors. We show theoretically that, exclusive of coupling losses, the use of a modal filter leads to the improvement of the rejection ratio in a two-beam interferometer by a factor of Q(sub f).

  16. Excitation of Single-Mode Lamb Waves at High-Frequency-Thickness Products.

    PubMed

    Khalili, Pouyan; Cawley, Peter

    2016-02-01

    Guided wave inspection is used extensively in petrochemical plants to check for defects such as corrosion. Long-range low-frequency inspection can be used to detect relatively large defects, while higher frequency inspection provides improved sensitivity to small defects, but the presence of multiple dispersive modes makes it difficult to implement. This paper investigates the possibility of exciting a single-mode Lamb wave with low dispersion at a frequency thickness of around 20 MHz-mm. It is shown by finite element (FE) analysis backed up by experiments that a signal dominated by the A1 mode can be generated, even in a region where many modes have similar phase velocities. The A1 mode has relatively little motion at the plate surface which means that only a small reflection is generated at features such as T-joints; this is verified numerically. It is also expected that it will be relatively unaffected by surface roughness or attenuative coatings. These features are very similar to those of the higher order mode cluster (HOMC) reported by other authors, and it is shown that the A1 mode shape is very similar to the deflected shape reported in HOMC.

  17. Mode division multiplexing technology for single-fiber optical trapping axial-position adjustment.

    PubMed

    Liu, Zhihai; Wang, Lei; Liang, Peibo; Zhang, Yu; Yang, Jun; Yuan, Libo

    2013-07-15

    We demonstrate trapped yeast cell axial-position adjustment without moving the optical fiber in a single-fiber optical trapping system. The dynamic axial-position adjustment is realized by controlling the power ratio of the fundamental mode beam (LP01) and the low-order mode beam (LP11) generated in a normal single-core fiber. In order to separate the trapping positions produced by the two mode beams, we fabricate a special fiber tapered tip with a selective two-step method. A yeast cell of 6 μm diameter is moved along the optical axis direction for a distance of ~3 μm. To the best of our knowledge, this is the first demonstration of the trapping position adjustment without moving the fiber for single-fiber optical tweezers. The excitation and utilization of multimode beams in a single fiber constitutes a new development for single-fiber optical trapping and makes possible more practical applications in biomedical research fields.

  18. Quantum Otto engine of a two-level atom with single-mode fields.

    PubMed

    Wang, Jianhui; Wu, Zhaoqi; He, Jizhou

    2012-04-01

    We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.

  19. Quantum Otto engine of a two-level atom with single-mode fields

    NASA Astrophysics Data System (ADS)

    Wang, Jianhui; Wu, Zhaoqi; He, Jizhou

    2012-04-01

    We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.

  20. Photo-structurable polymer for interlayer single-mode waveguide fabrication by femtosecond laser writing

    NASA Astrophysics Data System (ADS)

    Nguyen, Ho Hoai Duc; Hollenbach, Uwe; Pfirrmann, Stefan; Ostrzinski, Ute; Pfeiffer, Karl; Hengsbach, Stefan; Mohr, Juergen

    2017-04-01

    We present the fabrication and characterization of inter-layer single-mode light-guiding structures in a newly developed photo-structurable polymer via femtosecond laser writing. A host-guest polymer system utilizing external diffusion induces permanent and high refractive index modulation. Analyzing the complete curing and the impact of external diffusion on refractive index profile helps optimize the fabrication process. The fabrications of 4 × 2 array interconnect and 3-waveguide core fan-out device involve only a single layer, and need no stacking or alignment effort. The resulting pitch size and crosstalk between single-mode waveguides are 25 μm and -34 dB, respectively. Adding sensitizer into the photopolymer to increase its sensitivity in two-photon polymerization at a writing wavelength of 390 nm reduces the surface roughness of written structures by a factor of seven.

  1. Laser-direct writing of single mode and multi-mode polymer step index waveguide structures for optical backplanes and interconnection assemblies

    NASA Astrophysics Data System (ADS)

    Kruse, Kevin; Middlebrook, Christopher

    2015-01-01

    A laser direct writing (LDW) method is implemented as a cost efficient polymer waveguide (WG) fabrication method for prototyping large substrates for optical backplanes and optical interconnection assemblies. The LDW setup utilizes a 3-axis air-bearing motion platform to reduce WG fabrication error to within ±0.15 μm. A UV laser diode coupled single mode fiber with a focusing lens module is capable of LDW WGs at both multimode (50 μm) and single mode (6 μm) dimensions. Correlation between LDW parameters and fabricated WG dimensions using Dow Corning® OE-4140 UV-Cured Optical Elastomer (ncore = 1.5142, nclad = 1.5064) is discussed theoretically and confirmed experimentally for both applications. A theoretical model is developed and utilized for producing LDW multi-mode (0.04 dB/cm, λ = 850 nm) and single mode (0.55 dB/cm, λ = 1310 nm) WGs. Measured propagation losses of LDW WGs are comparable to losses of photolithographic multi-mode (0.04 dB/cm @ 850 nm) and single mode (0.59 dB/cm @ 1310 nm) WG builds. LDW multi-mode and single mode WG radial bend and crossing losses are evaluated for advanced optical communication channel routing capabilities and do not exhibit significant deviations from photolithographic-manufactured WG device loss.

  2. Multimode to single-mode converters: new results on 1-to-61 photonic lanterns

    NASA Astrophysics Data System (ADS)

    Olaya, J.-C.; Ehrlich, K.; Haynes, D. M.; Haynes, R.; Leon-Saval, S. G.; Schirdewahn, D.

    2012-09-01

    Photonic Lanterns are a fibre-based component performing the adiabatic conversion from a multimode fibre to a series of single-mode fibres. This conversion is required for combining fibre-based instruments used in astronomy with complex photonic functions. As any fibre-based system, the optical properties of the Photonic Lanterns need to be fully evaluated. In this paper, we present results on the performance of a 1-to-61 Photonic Lantern in terms of spectral transmission and modal noise characteristics. Firstly, we compare the spectra obtained at the output of two photonic lanterns spliced together in multimode-to-multimode configuration with spectra obtained when transmitting light through step-index single-mode and multimode fibres. We then show that the photonic lantern is generating less modal noise than a step-index multimode fibre of same core diameter, when it is submitted to bending and stretching, and we propose an interpretation of this result based on static mode scrambling performance and single-mode behavior.

  3. Comparison of LIDAR system performance for alternative single-mode receiver architectures: modeling and experimental validation

    NASA Astrophysics Data System (ADS)

    Toliver, Paul; Ozdur, Ibrahim; Agarwal, Anjali; Woodward, T. K.

    2013-05-01

    In this paper, we describe a detailed performance comparison of alternative single-pixel, single-mode LIDAR architectures including (i) linear-mode APD-based direct-detection, (ii) optically-preamplified PIN receiver, (iii) PINbased coherent-detection, and (iv) Geiger-mode single-photon-APD counting. Such a comparison is useful when considering next-generation LIDAR on a chip, which would allow one to leverage extensive waveguide-based structures and processing elements developed for telecom and apply them to small form-factor sensing applications. Models of four LIDAR transmit and receive systems are described in detail, which include not only the dominant sources of receiver noise commonly assumed in each of the four detection limits, but also additional noise terms present in realistic implementations. These receiver models are validated through the analysis of detection statistics collected from an experimental LIDAR testbed. The receiver is reconfigurable into four modes of operation, while transmit waveforms and channel characteristics are held constant. The use of a diffuse hard target highlights the importance of including speckle noise terms in the overall system analysis. All measurements are done at 1550 nm, which offers multiple system advantages including less stringent eye safety requirements and compatibility with available telecom components, optical amplification, and photonic integration. Ultimately, the experimentally-validated detection statistics can be used as part of an end-to-end system model for projecting rate, range, and resolution performance limits and tradeoffs of alternative integrated LIDAR architectures.

  4. Influence of the polarization mode dispersion on the propagation of ultrashort optical pulses in single-mode fiber lightguides with very weak linear birefringence and random inhomogeneities

    NASA Astrophysics Data System (ADS)

    Malykin, G. B.; Pozdnyakova, V. I.

    2011-09-01

    We consider the influence of the polarization mode dispersion, which is stipulated by the presence of random inhomogeneities in single-mode fiber lightguides, on the propagation of ultrashort optical pulses in the fiber communication lines with very weak linear birefringence. Evolution of the envelope of ultrashort optical pulses and their spectra as functions of the length of a single-mode fiber lightguide with very weak linear birefringence and random inhomogeneities are obtained by the method of mathematical simulation. An increase in the pulse duration is shown to be proportional to the square root of the length of a single-mode fiber lightguide. The numerical-simulation results are compared with the results of experimental measurements of the polarization mode dispersion.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  6. 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.

  7. Evolution of l-photon excited thermo vacuum state in a single-mode damping channel

    NASA Astrophysics Data System (ADS)

    He, Rui; Fan, Hong-Yi

    2016-01-01

    In this paper, we investigate how a kind of non-Gaussian states (l-photon excited thermo vacuum state Cla†l|0(β)>) evolves in a single-mode damping channel. We find that it evolves into a Laguerre-polynomial-weighted real-fictitious squeezed thermo vacuum state, which exhibits strong decoherence and its original nonclassicality fades. In particular, when l = 0, in this damping process the thermo squeezing effect decreases while the fictitious-mode vacuum becomes chaotic. In overcoming the difficulty of calculation, we employ the summation method within ordered product of operators, a new generating function formula about two-variable Hermite polynomials is derived.

  8. Second-order Bragg gratings in single-mode chalcogenide fibres

    SciTech Connect

    Bernier, M; Asatryan, K E; Vallee, R; Galstian, T M; Vasil'ev, Sergei A; Medvedkov, O I; Plotnichenko, V G; Gnusin, P I; Dianov, Evgenii M

    2011-05-31

    Bragg gratings with a second-order resonance wavelength in the near-IR spectral region have been inscribed into single-mode chalcogenide (As{sub 2}S{sub 3}) glass fibre by a He - Ne laser beam using a configuration typical of Bragg grating fabrication in germanosilicate fibre, with the use of a phase mask that ensures effective diffraction of the writing light into the +1 and -1 orders. The spectra of the inscribed gratings show no resonances due to cladding mode excitation because the cladding material is photosensitive. (fibre optics)

  9. Projective measurement of a single nuclear spin qubit by using two-mode cavity QED.

    PubMed

    Eto, Yujiro; Noguchi, Atsushi; Zhang, Peng; Ueda, Masahito; Kozuma, Mikio

    2011-04-22

    We report the implementation of projective measurement on a single 1/2 nuclear spin of the (171)Yb atom by measuring the polarization of cavity-enhanced fluorescence. To obtain cavity-enhanced fluorescence having a nuclear-spin-dependent polarization, we construct a two-mode cavity QED system, in which two cyclic transitions are independently coupled to each of the orthogonally polarized cavity modes, by manipulating the energy level of (171)Yb. This system can associate the nuclear spin degrees of freedom with the polarization of photons, which will facilitate the development of hybrid quantum systems.

  10. A nonlocal shell model for mode transformation in single-walled carbon nanotubes.

    PubMed

    Shi, M X; Li, Q M; Huang, Y

    2009-11-11

    A second-order strain gradient nonlocal shell model is established to study the mode transformation in single-walled carbon nanotubes (SWCNTs). Nonlocal length is calibrated carefully for SWCNTs in reference to molecular dynamics (MD) simulations through analysis of nonlocal length effects on the frequencies of the radial breathing mode (RBM) and circumferential flexural modes (CFMs) and its effects on mode transformation. All analyses show that only a negative second-order nonlocal shell model is appropriate to SWCNTs. Nonlocal length is evidently related to vibration modes and the radius-to-thickness ratio. It is found that a nonlocal length is approximately 0.1 nm in an average sense when RBM frequency is concerned. A nonlocal length of 0.122-0.259 nm is indicated for the mode transformation in a selected group of armchair SWCNTs. 2:1 and 1:1 internal resonances are found for the same SWCNT based on different models, which implies that the internal resonance mechanism depends on the model employed. Furthermore, it is shown that an effective thickness of approximately 0.1 nm is more appropriate to SWCNTs than 0.066 nm.

  11. Voltage tuning of vibrational mode energies in single-molecule junctions

    PubMed Central

    Li, Yajing; Doak, Peter; Kronik, Leeor; Neaton, Jeffrey B.; Natelson, Douglas

    2014-01-01

    Vibrational modes of molecules are fundamental properties determined by intramolecular bonding, atomic masses, and molecular geometry, and often serve as important channels for dissipation in nanoscale processes. Although single-molecule junctions have been used to manipulate electronic structure and related functional properties of molecules, electrical control of vibrational mode energies has remained elusive. Here we use simultaneous transport and surface-enhanced Raman spectroscopy measurements to demonstrate large, reversible, voltage-driven shifts of vibrational mode energies of C60 molecules in gold junctions. C60 mode energies are found to vary approximately quadratically with bias, but in a manner inconsistent with a simple vibrational Stark effect. Our theoretical model instead suggests that the mode shifts are a signature of bias-driven addition of electronic charge to the molecule. These results imply that voltage-controlled tuning of vibrational modes is a general phenomenon at metal–molecule interfaces and is a means of achieving significant shifts in vibrational energies relative to a pure Stark effect. PMID:24474749

  12. Single-mode planar optics for 4-20um wavelengths astronomical interferometry

    NASA Astrophysics Data System (ADS)

    Laurent, E.; Kern, P.; Schanen, I.; Rousselet-Perraut, K.

    2002-06-01

    Single-mode planar optics for 4-20 micrometers wavelengths astronomical interferometry. Spatial filtering is a critical issue to achieve nulling interferometry in the framework of spatial missions aimed at the detection of exoplanets. Several working interferometric instruments take benefits of guided optics for spatial filtering in the near IR wavelengths and thus provide accurate visibility measurements. Futhermore planar optics would also provides beam combining functions within a single compact and stable device. Existing telecom technology allows beam combiner realizations for 0.8 to 1.6 micrometers wavelengths. Last works allow us to valid these technologies up to 2.4 micrometers for stellar interferometry in the H and K bands. Technological developments are required to meet the scientific domain of the spatial missions like IRSI/DARWIN and TPF dedicated to thermal infrared wavelengths [4-20 micrometers]. We present the most promising materials with their technologies to manufacture single-mode planar optics for this wavelength range. First set of solutions involved chalcogenide glasses. Channel waveguides could be manufactured by photo-exposition method or thin layer etching process. Another solution is using porous silicon obtained from an acid dissolution of a silicon substrate which allows refractive index modulation. The last set of solution is based on thin films etching of semiconductor materials like silicon, germanium, zinc sulfide and zinc selenide.Test benches for the single-mode behavior are also presented. For each solutions, we present some manufactured waveguides with their optical characterizations.

  13. Comparison of two blanket surveys of arsenic in tubewells conducted 12 years apart in a 25 km2 area of Bangladesh

    PubMed Central

    van Geen, Alexander; Sumon, Ershad B. A.; Pitcher, Lynnette; Mey, Jacob L.; Ahsan, Habibul; Graziano, Joseph H.; Ahmed, Kazi Matin

    2014-01-01

    The arsenic (As) content of groundwater pumped from all tubewells within 61 contiguous villages of Araihazar, Bangladesh, was determined a first time in 2000–01 with laboratory measurements and a second time in 2012–13 using the ITS Arsenic Econo-Quick kit. The two surveys indicate that the total number of tubewells within the area almost doubled from 5,560 to 10,879 over 12 years. The evolution of the distribution of well ages between the two surveys is consistent with a simple model that combines an annual increase of 42 wells/year in the rate of installations within the 61 villages starting in 1980 and a 7%/year rate of abandonment of wells as a function of well age. Colored placards were posted on each pumphead in 2012–2013 on the basis of the kit results relative to the WHO guideline for As and the Bangladesh standard for As in drinking water: blue for As ≤10 µg/L, green >10–50 µg/L, and red: >50 µg/L. According to quality-control samples collected from 502 tubewells for comparing the kit results with laboratory measurements, not a single well labeled blue in 2012–13 should have been labeled red and vice-versa. Field-kit testing in 2012–13 did not change the status of wells relative to the Bangladesh standard of 876 (87%) out of 1,007 wells with a placard based on laboratory measurements in 2000–01 still attached to the pumphead. The high proportion of tubewells believed by households to be unsafe (66% out of 2,041) that were still used for drinking and cooking in 2012–13 underlines the need for more widespread testing to identify low-As wells as an alternative source of drinking water. PMID:24438870

  14. Comparison of two blanket surveys of arsenic in tubewells conducted 12 years apart in a 25 km(2) area of Bangladesh.

    PubMed

    van Geen, Alexander; Ahmed, Ershad B; Pitcher, Lynnette; Mey, Jacob L; Ahsan, Habibul; Graziano, Joseph H; Ahmed, Kazi Matin

    2014-08-01

    The arsenic (As) content of groundwater pumped from all tubewells within 61 contiguous villages of Araihazar, Bangladesh, was determined a first time in 2000-01 with laboratory measurements and a second time in 2012-13 using the ITS Arsenic Econo-Quick kit. The two surveys indicate that the total number of tubewells within the area almost doubled from 5560 to 10,879 over 12 years. The evolution of the distribution of well ages between the two surveys is consistent with a simple model that combines an annual increase of 42 wells/year in the rate of installations within the 61 villages starting in 1980 and a 7%/year rate of abandonment of wells as a function of well age. Colored placards were posted on each pumphead in 2012-13 on the basis of the kit results relative to the WHO guideline for As and the Bangladesh standard for As in drinking water: blue for As≤10 μg/L, green>10-50 μg/L, and red: >50 μg/L. According to quality-control samples collected from 502 tubewells for comparing the kit results with laboratory measurements, not a single well labeled blue in 2012-13 should have been labeled red and vice-versa. Field-kit testing in 2012-13 did not change the status of wells relative to the Bangladesh standard of 876 (87%) out of 1007 wells with a placard based on laboratory measurements in 2000-01 still attached to the pumphead. The high proportion of tubewells believed by households to be unsafe (66% out of 2041) that were still used for drinking and cooking in 2012-13 underlines the need for more widespread testing to identify low-As wells as an alternative source of drinking water.

  15. High power single-longitudinal-mode cyan laser at 500.8 nm

    NASA Astrophysics Data System (ADS)

    Hao, E. J.; Li, T.; Wang, Z. D.

    2012-05-01

    An all-solid-state single-longitudinal-mode (SLM) laser at 500.8 nm with 830 mW output power has been demonstrated for the first time. By using a new resonator for doubly resonant, Nd:GdVO4 and Nd:YAG were pumped by two laser diode arrays coupled by optical fiber, respectively. In the two sub-cavities, SLM wavelengths of 1064 and 946 nm were induced by using the twisted-mode technique and then mixed into SLM 500.8 nm laser with sum-frequency technology. The SLM 500.8 nm laser output of 830 mW was obtained at the incident pump power of 20 W for Nd:GdVO4 and 23 W for Nd:YAG. The experimental results showed that the intracavity sum-frequency mixing by twisted-mode technique is an effective method for SLM 500.8 nm laser.

  16. Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon

    NASA Astrophysics Data System (ADS)

    Zhao, Deyin; Liu, Shihchia; Yang, Hongjun; Ma, Zhenqiang; Reuterskiöld-Hedlund, Carl; Hammar, Mattias; Zhou, Weidong

    2016-01-01

    We report here an optically pumped hybrid III-V/Si photoic crystal surface emitting laser (PCSEL), consisting of a heterogeneously integrated III-V InGaAsP quantum well heterostructure gain medium, printed on a patterned defect-free Si photonic crystal (PC) bandedge cavity. Single mode lasing was achieved for a large area laser, with a side-mode suppression ratio of 28 dB, for lasing operation temperature ~200 K. Two types of lasers were demonstrated operating at different temperatures. Detailed modal analysis reveals the lasing mode matches with the estimated lasing gain threshold conditions. Our demonstration promises a hybrid laser sources on Si towards three-dimensional (3D) integrated Si photonics for on-chip wavelength-division multiplex (3D WDM) systems for a wide range of volume photonic/electronic applications in computing, communication, sensing, imaging, etc.

  17. Three-dimensional single-mode nonlinear ablative Rayleigh-Taylor instability

    SciTech Connect

    Yan, R.; Aluie, H.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2016-02-15

    The nonlinear evolution of the single-mode ablative Rayleigh-Taylor instability is studied in three dimensions. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the three-dimensional (3D) terminal bubble velocity greatly exceeds both the two-dimensional (2D) value and the classical 3D bubble velocity. Unlike in 2D, the 3D short-wavelength bubble velocity does not saturate. The growing 3D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes to the ablated plasma filling the bubble volume.

  18. Three-dimensional single-mode nonlinear ablative Rayleigh-Taylor instability

    SciTech Connect

    Yan, R.; Betti, R.; Sanz, J.; Aluie, H.; Liu, B.; Frank, A.

    2016-02-02

    The nonlinear evolution of the single-mode ablative Rayleigh-Taylor instability is studied in three dimensions. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the three-dimensional (3D) terminal bubble velocity greatly exceeds both the two-dimensional (2D) value and the classical 3D bubble velocity. Unlike in 2D, the 3D short-wavelength bubble velocity does not saturate. The growing 3D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. As a result, the vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes to the ablated plasma filling the bubble volume.

  19. Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon

    PubMed Central

    Zhao, Deyin; Liu, Shihchia; Yang, Hongjun; Ma, Zhenqiang; Reuterskiöld-Hedlund, Carl; Hammar, Mattias; Zhou, Weidong

    2016-01-01

    We report here an optically pumped hybrid III-V/Si photoic crystal surface emitting laser (PCSEL), consisting of a heterogeneously integrated III-V InGaAsP quantum well heterostructure gain medium, printed on a patterned defect-free Si photonic crystal (PC) bandedge cavity. Single mode lasing was achieved for a large area laser, with a side-mode suppression ratio of 28 dB, for lasing operation temperature ~200 K. Two types of lasers were demonstrated operating at different temperatures. Detailed modal analysis reveals the lasing mode matches with the estimated lasing gain threshold conditions. Our demonstration promises a hybrid laser sources on Si towards three-dimensional (3D) integrated Si photonics for on-chip wavelength-division multiplex (3D WDM) systems for a wide range of volume photonic/electronic applications in computing, communication, sensing, imaging, etc. PMID:26727551

  20. Printed Large-Area Single-Mode Photonic Crystal Bandedge Surface-Emitting Lasers on Silicon.

    PubMed

    Zhao, Deyin; Liu, Shihchia; Yang, Hongjun; Ma, Zhenqiang; Reuterskiöld-Hedlund, Carl; Hammar, Mattias; Zhou, Weidong

    2016-01-04

    We report here an optically pumped hybrid III-V/Si photoic crystal surface emitting laser (PCSEL), consisting of a heterogeneously integrated III-V InGaAsP quantum well heterostructure gain medium, printed on a patterned defect-free Si photonic crystal (PC) bandedge cavity. Single mode lasing was achieved for a large area laser, with a side-mode suppression ratio of 28 dB, for lasing operation temperature ~ 200 K. Two types of lasers were demonstrated operating at different temperatures. Detailed modal analysis reveals the lasing mode matches with the estimated lasing gain threshold conditions. Our demonstration promises a hybrid laser sources on Si towards three-dimensional (3D) integrated Si photonics for on-chip wavelength-division multiplex (3D WDM) systems for a wide range of volume photonic/electronic applications in computing, communication, sensing, imaging, etc.

  1. Design of photonic band gap fibers with suppressed higher-order modes: Towards the development of effectively single mode large hollow-core fiber platforms

    NASA Astrophysics Data System (ADS)

    Saitoh, Kunimasa; Florous, Nikolaos J.; Murao, Tadashi; Koshiba, Masanori

    2006-08-01

    The objective of the present investigation is to propose and theoretically demonstrate the effective suppression of higher-order modes in large-hollow-core photonic band gap fibers (PBGFs), mainly for low-loss data transmission platforms and/or high power delivery systems. The proposed design strategy is based on the index-matching mechanism of central air-core modes with defected outer core modes. By incorporating several air-cores in the cladding of the PBGF with 6-fold symmetry it is possible to resonantly couple the light corresponding to higher-order modes into the outer core, thus significantly increasing the leakage losses of the higher-order modes in comparison to the fundamental mode, thus making our proposed design to operate in an effectively single mode fashion with polarization independent propagation characteristics. The validation of the procedure is ensured with a detailed PBGF analysis based on an accurate finite element modal solver. Extensive numerical results show that the leakage losses of the higher-order modes can be enhanced in a level of at least 2 orders of magnitude in comparison to those of the fundamental mode. Our investigation is expected to remove an essential obstacle in the development of large-core single-mode hollow-core fibers, thus enabling them to surpass the attenuation of conventional fibers.

  2. Design of photonic band gap fibers with suppressed higher-order modes: towards the development of effectively single mode large hollow-core fiber platforms.

    PubMed

    Saitoh, Kunimasa; Florous, Nikolaos J; Murao, Tadashi; Koshiba, Masanori

    2006-08-07

    The objective of the present investigation is to propose and theoretically demonstrate the effective suppression of higher-order modes in large-hollow-core photonic band gap fibers (PBGFs), mainly for low-loss data transmission platforms and/or high power delivery systems. The proposed design strategy is based on the index-matching mechanism of central air-core modes with defected outer core modes. By incorporating several air-cores in the cladding of the PBGF with 6-fold symmetry it is possible to resonantly couple the light corresponding to higher-order modes into the outer core, thus significantly increasing the leakage losses of the higher-order modes in comparison to the fundamental mode, thus making our proposed design to operate in an effectively single mode fashion with polarization independent propagation characteristics. The validation of the procedure is ensured with a detailed PBGF analysis based on an accurate finite element modal solver. Extensive numerical results show that the leakage losses of the higher-order modes can be enhanced in a level of at least 2 orders of magnitude in comparison to those of the fundamental mode. Our investigation is expected to remove an essential obstacle in the development of large-core single-mode hollow-core fibers, thus enabling them to surpass the attenuation of conventional fibers.

  3. Top hat single-mode polarization maintaining fiber and polarizing numerical design

    NASA Astrophysics Data System (ADS)

    Gouriou, Pierre; Scol, Florent; Sevigny, Benoit; Valentin, Constance; Quiquempois, Yves; Bigot, Laurent; Habert, Rémi; Cassez, Andy; Vanvincq, Olivier; Hugonnot, Emmanuel; Bouwmans, Geraud

    2016-03-01

    Compactness, long term stability and no free-space alignment are important advantages of fiber lasers over bulky systems. These fiber lasers have also demonstrated their capability to deliver high-power pulses and are thus suitable for numerous applications. Nevertheless the intensity profile delivered usually has a Gaussian-like shape, which most of the time is sufficient, but it could be interesting, for many applications (laser-biological tissues interactions, heat treatment, industrial laser processing or for seeding large-scale laser facilities like Laser MegaJoule) to obtain a homogeneous intensity profile at the fiber laser output. Moreover several of these applications required a linearly polarized output beam. In order to achieve all these requirements we have developed and realized a new fiber design. This fiber is the first polarization maintaining single-mode fiber delivering a flat top intensity. A high quality flat mode was obtained at 1.05μm through the use of a well-tailored index profile and single-mode behavior was verified by shifting the injection and using the S² imaging. Moreover, boron Stress Applying Parts (SAPs) including in the cladding led to a birefringence of 0.6x10-4 and a measured PER better than 20dB even for a long fiber length (~20 m). Alongside the fabrication, we developed a simulation code, using Comsol Multiphysics®, to take into account the stress dependency induced by the SAPs. Further modeling allows us to present an effectively single-mode fiber design, delivering a top-hat mode profile and exhibiting a polarizing behavior.

  4. 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

  5. Formation of visible single-mode light sources using quantum dots

    NASA Astrophysics Data System (ADS)

    Baig, Sarfaraz; Xu, Jianfeng; Wu, Pengfei; Chen, Bing; Wang, Michael

    2008-08-01

    The market demands for innovative, efficient, small package and single-mode light sources are always high because of their broad applications in scientific, medical, industrial, and commercial fields. The high photoluminescence quantum yield, photophysical and photochemical stability, and tunable emission wavelength make quantum dots ideal for a new generation of solid state light sources. We report on the realization of various single-mode light sources in the visible spectral band by using semiconductor quantum dots. The effective use of a waveguide structure can help achieve the divergence control of the output light beam. This technique may benefit the development for next generation light emitting diodes, optical communication, intelligent optical sensors, microprocessors, and nanoscale optical imaging systems.

  6. A surface plasmon resonance sensor based on a single mode D-shape polymer optical fiber

    NASA Astrophysics Data System (ADS)

    Gasior, Katarzyna; Martynkien, Tadeusz; Napiorkowski, Maciej; Zolnacz, Kinga; Mergo, Pawel; Urbanczyk, Waclaw

    2017-02-01

    For the first time to our knowledge, we report a successful fabrication of surface plasmon resonance (SPR) sensors in a specially developed single-mode birefringent polymer D-shape fiber with a core made of PMMA/PS copolymer. A small distance between the core and the cladding boundary allows to deposit a gold layer directly onto the flat fiber surface, which significantly simplifies the sensors fabrication process. The developed SPR sensor exhibits a sensitivity of 2765 nm RIU-1 for the refractive index of external medium equal to 1.410, which is similar to the sensitivity of the SPR sensors based on conventional side-polished single-mode silica fibers. Using the finite element method, we also numerically studied the sensor performance. The sensor characteristics obtained in the simulations are in a relatively good agreement with the experimental results.

  7. Scanning single-mode fiber optic catheter-endoscope for optical coherence tomography.

    PubMed

    Tearney, G J; Boppart, S A; Bouma, B E; Brezinski, M E; Weissman, N J; Southern, J F; Fujimoto, J G

    1996-04-01

    We describe a new optical coherence tomography catheter-endoscope for micrometer-scale, cross-sectional imaging in internal organ systems. The catheter-endoscope uses single-mode fiber optics with a novel transverse scanning design. The distal end of the catheter-endoscope uses a gradient-index lens with a microprism to emit and collect a single spatial-mode optical beam with specific focusing characteristics. The beam is scanned in a circumferential pattern and can image transverse cross sections through the structure into which it is inserted. A device with a diameter as small as 1.1 mm has been achieved, and imaging of in vitro human venous morphology is demonstrated.

  8. Stability of short, single-mode erbium-doped fiber lasers.

    PubMed

    Svalgaard, M; Gilbert, S L

    1997-07-20

    We conducted a detailed study of the stability of short, erbium-doped fiber lasers fabricated with two UV-induced Bragg gratings written into the doped fiber. We find that the relative intensity noise of single-longitudinal-mode fiber grating lasers is approximately 3 orders of magnitude lower than that of a single-frequency 1.523-mum helium-neon laser. The frequency noise spectrum contains few resonances, none of which exceeds 0.6 kHz/Hz(1/2) rms; the integrated rms frequency noise from 50 Hz to 63 kHz is 36 kHz. We also demonstrate a simple method for monitoring the laser power and number of oscillating modes during laser fabrication.

  9. 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.

  10. Validation of Nek5000 against low-Atwood, single-mode Rayleigh Taylor experiments

    NASA Astrophysics Data System (ADS)

    Hutchinson, Maxwell

    2015-11-01

    Experiments by Wilkinson and Jacobs demonstrate the stagnation and reacceleration phases of the low-Atwood, single-mode Rayleigh Taylor instability between two water mixtures. We reproduce the experimental conditions of three runs in direct numerical simulations using the spectral element code Nek5000. The simulations required 17 billion grid points on 512 thousand cores of the Mira supercomputer to reach Rayleigh numbers up to 90 million. We extend the vertical dimension to reach higher bubble aspect ratios and demonstrate the limits of wall-bounded single-mode studies. Finally, exploration of the full-field results reveals spanwise secondary flows that enhance mixing at low to moderate Reynolds number. This research used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357.

  11. Bowtie nano-aperture as interface between near-fields and a single-mode fiber.

    PubMed

    Mivelle, M; Ibrahim, I A; Baida, F; Burr, G W; Nedeljkovic, D; Charraut, D; Rauch, J-Y; Salut, R; Grosjean, T

    2010-07-19

    We present the development and study of a single bowtie nano-aperture (BNA) at the end of a monomode optical fiber as an interface between near-fields/nano-optical objects and the fiber mode. To optimize energy conversion between BNA and the single fiber mode, the BNA is opened at the apex of a specially designed polymer fiber tip which acts as an efficient mediator (like a horn optical antenna) between the two systems. As a first application, we propose to use our device as polarizing electric-field nanocollector for scanning near-field optical microscopy (SNOM). However, this BNA-on-fiber probe may also find applications in nanolithography, addressing and telecommunications as well as in situ biological and chemical probing and trapping.

  12. Interferometric coupling of the Keck telescopes with single-mode fibers.

    PubMed

    Perrin, G; Woillez, J; Lai, O; Guérin, J; Kotani, T; Wizinowich, P L; Le Mignant, D; Hrynevych, M; Gathright, J; Léna, P; Chaffee, F; Vergnole, S; Delage, L; Reynaud, F; Adamson, A J; Berthod, C; Brient, B; Collin, C; Crétenet, J; Dauny, F; Deléglise, C; Fédou, P; Goeltzenlichter, T; Guyon, O; Hulin, R; Marlot, C; Marteaud, M; Melse, B-T; Nishikawa, J; Reess, J-M; Ridgway, S T; Rigaut, F; Roth, K; Tokunaga, A T; Ziegler, D

    2006-01-13

    Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.

  13. Heralded generation of single photons entangled in multiple temporal modes with controllable waveforms

    NASA Astrophysics Data System (ADS)

    Gogyan, A.; Sisakyan, N.; Akhmedzhanov, R.; Malakyan, Yu

    2014-11-01

    Time-bin entangled single-photons are highly demanded for long distance quantum communication. We propose a heralded source of tunable narrowband single photons entangled in well-separated multiple temporal modes (time bins) with controllable amplitudes. The detection of a single Stokes photon generated in a cold atomic ensemble via Raman scattering of a weak write pulse heralds the preparation of one spin excitation stored within the atomic medium. A train of read laser pulses deterministically converts the atomic excitation into a single anti-Stokes photon delocalized in multi-time-bins. The waveforms of bins are well-controlled by the read pulse parameters. A scheme to measure the phase coherence across all time bins is suggested.

  14. Bend-insensitive single-mode photonic crystal fiber with ultralarge effective area for dual applications

    NASA Astrophysics Data System (ADS)

    Islam, Md. Asiful; Alam, M. Shah

    2013-05-01

    A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies in the range of 10-3 to 10-4 dB/turn or lower over 1300 to 1700 nm, and 2 × 10-4 dB/turn at the wavelength of 1550 nm for a 30-mm bend radius with a higher order mode (HOM) cut-off frequency below 1200 nm for WDM application. When the whole structure of the PCF is scaled down, a bending loss of 6.78×10-4 dB/turn at 1550 nm for a 4-mm bend radius is obtained, and the loss remains in the order of 10-4 dB/turn over the same range of wavelength with an HOM cut-off frequency below 700 nm, and makes the fiber useful for FTTH applications. Furthermore, this structure is also optimized to show a splice loss near zero for fusion-splicing to a conventional single-mode fiber (SMF).

  15. Unambiguous phonon mode assignment in multiferroic BiFeO3 single crystals

    NASA Astrophysics Data System (ADS)

    Beekman, Christianne; Cheong, Sang-Wook; Burch, Kenneth

    2012-02-01

    In Bismuth ferrite (BiFeO3) antiferromagnetic and ferroelectric order parameters coexist at room temperature, making this material an excellent candidate for new functionalities, such as electrical control of magnetism. Despite extensive reports on Raman scattering experiments on single crystals and thin films, controversy still remains in the observation and assignment of the phonon mode symmetries. We present polarized micro-Raman spectroscopy of single crystals ((1 0 0)cubic surface) with uniform ferroelectric polarization. Careful examination of the Raman spectra upon crystal rotation enables us to unambiguously assign the (A1, Ex and Ey) modes. We will show that ambiguity is easily introduced by slight misalignment of the crystal and that the crystal rotation is necessary to reach unambiguous mode assignment. Our method not only results in proper Raman mode assignment, which is necessary to describe the phonons critical for the multiferroic behavior, it also allows study of symmetry breaking and may provide a way to non-invasively check the ferroelectric polarization direction.

  16. Single-mode interface states in heterostructure waveguides with Bragg and non-Bragg gaps

    PubMed Central

    Fan, Ya-Xian; Sang, Tang-Qing; Liu, Ting; Xu, Lan-Lan; Tao, Zhi-Yong

    2017-01-01

    Interface states can always arise in heterostructures that consist of two or more (artificial) materials with topologically different energy bands. The gapped band structure can be classified by the Chern number (a topological invariant) generally or the Zak phase in one-dimensional periodic systems. Recently, topological properties have been employed to investigate the interface states occurring at the connecting regions of the heterostructures of mechanical isostatic lattices and acoustical waveguides. Here, we study this heterostructure phenomenon by carefully connecting two corrugated stainless steel waveguides with Bragg and non-Bragg gaps at approximately the same frequency. These two waveguide structures can be achieved by continuously varying their geometry parameters when a topological transition exists in the forbidden bands, in which the reflection impedance changes the sign. Furthermore, a localized single high-order mode has been observed at the interface because of the transverse mode interactions, which relate to the non-Bragg gaps created by the different transverse mode resonances. Such a localized acoustic single mode with very large enhanced intensity could find its applications in sound detection, biomedical imaging, and underwater sound control, and could also enrich our means of wave front manipulations in various engineering fields. PMID:28287173

  17. Single-mode interface states in heterostructure waveguides with Bragg and non-Bragg gaps

    NASA Astrophysics Data System (ADS)

    Fan, Ya-Xian; Sang, Tang-Qing; Liu, Ting; Xu, Lan-Lan; Tao, Zhi-Yong

    2017-03-01

    Interface states can always arise in heterostructures that consist of two or more (artificial) materials with topologically different energy bands. The gapped band structure can be classified by the Chern number (a topological invariant) generally or the Zak phase in one-dimensional periodic systems. Recently, topological properties have been employed to investigate the interface states occurring at the connecting regions of the heterostructures of mechanical isostatic lattices and acoustical waveguides. Here, we study this heterostructure phenomenon by carefully connecting two corrugated stainless steel waveguides with Bragg and non-Bragg gaps at approximately the same frequency. These two waveguide structures can be achieved by continuously varying their geometry parameters when a topological transition exists in the forbidden bands, in which the reflection impedance changes the sign. Furthermore, a localized single high-order mode has been observed at the interface because of the transverse mode interactions, which relate to the non-Bragg gaps created by the different transverse mode resonances. Such a localized acoustic single mode with very large enhanced intensity could find its applications in sound detection, biomedical imaging, and underwater sound control, and could also enrich our means of wave front manipulations in various engineering fields.

  18. Investigation on a compact in-line multimode-single-mode-multimode fiber structure

    NASA Astrophysics Data System (ADS)

    Yin, Bin; Li, Yang; Liu, Zhi-bo; Feng, Suchun; Bai, Yunlong; Xu, Yao; Jian, Shuisheng

    2016-06-01

    We carried out a detailed investigation on a compact in-line multimode single-mode multimode (MSM) fiber structure. Both theoretical modal and experimental setup were established to demonstrate the transmission characteristics and the corresponding responses of the applied strain and temperature. The proposed structure simply involves a section of the single-mode fiber (SMF) spliced to two sections of multimode fiber (MMF) and lead-in and lead-out SMFs. The excited environment-sensitive cladding modes together with the fundamental mode in the central SMF form a typical Mach-Zehnder interferometer (MZI). We analyzed the transmission characteristics of the different length of the middle SMF and the MMF in detail. In the experiment, we obtained the extinction ratio of the MSM fiber structure based MZI comb spectrum which was up to 20 dB, and sensitivities of 0.7096 pm/με (0-2000 με) and 44.12 pm/°C (10-70 °C), which proved the potential sensing applications of the proposed fiber structure.

  19. Dynamically Manipulating Topological Physics and Edge Modes in a Single Degenerate Optical Cavity

    NASA Astrophysics Data System (ADS)

    Zhou, Xiang-Fa; Luo, Xi-Wang; Wang, Su; Guo, Guang-Can; Zhou, Xingxiang; Pu, Han; Zhou, Zheng-Wei

    2017-02-01

    We propose a scheme to simulate topological physics within a single degenerate cavity, whose modes are mapped to lattice sites. A crucial ingredient of the scheme is to construct a sharp boundary so that the open boundary condition can be implemented for this effective lattice system. In doing so, the topological properties of the system can manifest themselves on the edge states, which can be probed from the spectrum of an output cavity field. We demonstrate this with two examples: a static Su-Schrieffer-Heeger chain and a periodically driven Floquet topological insulator. Our work opens up new avenues to explore exotic photonic topological phases inside a single optical cavity.

  20. Self-aligned deterministic coupling of single quantum emitter to nanofocused plasmonic modes

    PubMed Central

    Gong, Su-Hyun; Kim, Je-Hyung; Ko, Young-Ho; Rodriguez, Christophe; Shin, Jonghwa; Lee, Yong-Hee; Dang, Le Si; Zhang, Xiang; Cho, Yong-Hoon

    2015-01-01

    The quantum plasmonics field has emerged and been growing increasingly, including study of single emitter–light coupling using plasmonic system and scalable quantum plasmonic circuit. This offers opportunity for the quantum control of light with compact device footprint. However, coupling of a single emitter to highly localized plasmonic mode with nanoscale precision remains an important challenge. Today, the spatial overlap between metallic structure and single emitter mostly relies either on chance or on advanced nanopositioning control. Here, we demonstrate deterministic coupling between three-dimensionally nanofocused plasmonic modes and single quantum dots (QDs) without any positioning for single QDs. By depositing a thin silver layer on a site-controlled pyramid QD wafer, three-dimensional plasmonic nanofocusing on each QD at the pyramid apex is geometrically achieved through the silver-coated pyramid facets. Enhancement of the QD spontaneous emission rate as high as 22 ± 16 is measured for all processed QDs emitting over ∼150-meV spectral range. This approach could apply to high fabrication yield on-chip devices for wide application fields, e.g., high-efficiency light-emitting devices and quantum information processing. PMID:25870303

  1. Single-nanoparticle detection with slot-mode photonic crystal cavities

    SciTech Connect

    Wang, Cheng; Kita, Shota; Lončar, Marko; Quan, Qimin; Li, Yihang

    2015-06-29

    Optical cavities that are capable for detecting single nanoparticles could lead to great progress in early stage disease diagnostics and the study of biological interactions on the single-molecule level. In particular, photonic crystal (PhC) cavities are excellent platforms for label-free single-nanoparticle detection, owing to their high quality (Q) factors and wavelength-scale modal volumes. Here, we demonstrate the design and fabrication of a high-Q (>10{sup 4}) slot-mode PhC nanobeam cavity, which is able to strongly confine light in the slotted regions. The enhanced light-matter interaction results in an order of magnitude improvement in both refractive index sensitivity (439 nm/RIU) and single-nanoparticle sensitivity compared with conventional dielectric-mode PhC cavities. Detection of single polystyrene nanoparticles with radii of 20 nm and 30 nm is demonstrated in aqueous environments (D{sub 2}O), without additional laser and temperature stabilization techniques.

  2. Bridging visible and telecom wavelengths with a single-mode broadband photon pair source

    SciTech Connect

    Soeller, C.; Brecht, B.; Mosley, P. J.; Zang, L. Y.; Podlipensky, A.; Joly, N. Y.; Russell, P. St. J.; Silberhorn, C.

    2010-03-15

    We present a spectrally decorrelated photon pair source bridging the visible and telecom wavelength regions. Tailored design and fabrication of a solid-core photonic crystal fiber (PCF) lead to the emission of signal and idler photons into only a single spectral and spatial mode. Thus no narrowband filtering is necessary and the heralded generation of pure photon number states in ultrafast wave packets at telecom wavelengths becomes possible.

  3. Low-Bending-Loss Single-Mode Fibers for Fiber-to-the-Home

    NASA Astrophysics Data System (ADS)

    Himeno, Kuniharu; Matsuo, Shoichiro; Guan, Ning; Wada, Akira

    2005-11-01

    Recent progress on low-bending-loss single-mode optical fibers for fiber-to-the-home (FTTH) is reviewed. Designing and manufacturing for three types of fibers-a step-index-profile fiber, a trench-index-profile fiber, and a holey fiber-are discussed. The trench-index-profile fibers and the holey fibers are confirmed to be candidates for indoor wiring because of their low bending losses, as well as splice losses.

  4. Electro-optical circuit board with single-mode glass waveguide optical interconnects

    NASA Astrophysics Data System (ADS)

    Brusberg, Lars; Neitz, Marcel; Pernthaler, Dominik; Weber, Daniel; Sirbu, Bogdan; Herbst, Christian; Frey, Christopher; Queisser, Marco; Wöhrmann, Markus; Manessis, Dionysios; Schild, Beatrice; Oppermann, Hermann; Eichhammer, Yann; Schröder, Henning; Hâkansson, Andreas; Tekin, Tolga

    2016-03-01

    A glass optical waveguide process has been developed for fabrication of electro-optical circuit boards (EOCB). Very thin glass panels with planar integrated single-mode waveguides can be embedded as a core layer in printed circuit boards for high-speed board-level chip-to-chip and board-to-board optical interconnects over an optical backplane. Such singlemode EOCBs will be needed in upcoming high performance computers and data storage network environments in case single-mode operating silicon photonic ICs generate high-bandwidth signals [1]. The paper will describe some project results of the ongoing PhoxTroT project, in which a development of glass based single-mode on-board and board-to-board interconnection platform is successfully in progress. The optical design comprises a 500 μm thin glass panel (Schott D263Teco) with purely optical layers for single-mode glass waveguides. The board size is accommodated to the mask size limitations of the fabrication (200 mm wafer level process, being later transferred also to larger panel size). Our concept consists of directly assembling of silicon photonic ICs on cut-out areas in glass-based optical waveguide panels. A part of the electrical wiring is patterned by thin film technology directly on the glass wafer surface. A coupling element will be assembled on bottom side of the glass-based waveguide panel for 3D coupling between board-level glass waveguides and chip-level silicon waveguides. The laminate has a defined window for direct glass access for assembling of the photonic integrated circuit chip and optical coupling element. The paper describes the design, fabrication and characterization of glass-based electro-optical circuit board with format of (228 x 305) mm2.

  5. 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.

  6. 7-W single-mode thulium-doped fibre laser pumped at 1230 nm

    SciTech Connect

    Kravtsov, K S; Bufetov, Igor' A; Medvedkov, O I; Dianov, Evgenii M; Yashkov, M V; Gur'yanov, A N

    2005-07-31

    An efficient thulium-doped fibre laser emitting at {approx}2 {mu}m upon pumping into the long-wavelength {sup 3}H{sub 6} {yields} {sup 3}H{sub 5} absorption band of Tm{sup 3+} ions is developed. The maximum output power of the single-mode thulium laser pumped at 1230 nm was 7 W at 1956 nm for a pump conversion efficiency of 35%. (lasers)

  7. Optical fiber waveguide sagnac interferometer. Phase 1: Multiturn one meter diameter, single mode. [optical gyroscopes

    NASA Technical Reports Server (NTRS)

    Vali, V.

    1977-01-01

    A rotating ring interferometer was constructed using a 100 meters of single mode optical fiber wound on a crystal cylinder. A 20 inch diameter fiber interferometer gyroscope was built and its sensitivity was evaluated. Major noise sources were identified and improvements for the next phase of development were determined. The accuracy of .01 of a fringe can be improved to .0001 by the removal of the noise source.

  8. Design and fabrication of 1.55 μm broad area slotted single-mode Fabry-Perot lasers

    NASA Astrophysics Data System (ADS)

    Mengke, Li; Lijun, Yuan; Hongyan, Yu; Qiang, Kan; Shiyan, Li; Junping, Mi; Jiaoqing, Pan

    2016-03-01

    We present a single-mode laser on a p-InP substrate suitable for bonding on silicon-on-insulator (SOI) wafer. The laser can realize single mode lasing with etching perturbing slots by standard photolithography and an inductively coupled-plasma (ICP) etching technique without any regrowth steps. The parameters were designed using the simulation tool “cavity modeling framework” (CAMFR). The single mode of 1539 nm wavelength at the threshold current of 130 mA with the maximum output power of 3.9 mW was obtained at 10 °C in continuous-wave operation. The simple technology, low cost and the single-mode characteristics make the broad area slotted single-mode FP laser a promising light source on the silicon-based optical interconnection applications.

  9. Dynamic deformation and fracture of single crystal silicon: Fracture modes, damage laws, and anisotropy

    SciTech Connect

    Huang, J. Y.; E, J. C.; Huang, J. W.; Sun, T.; Fezzaa, K.; Xu, S. L.; Luo, S. N.

    2016-05-25

    Impact fracture of single-crystal Si is critical to long-term reliability of electronic devices and solar cells for its wide use as components or substrates in semiconductor industry. Single-crystal Si is loaded along two different crystallographic directions with a split Hopkinson pressure bar integrated with an in situ x-ray imaging and diffraction system. Bulk stress histories are measured, simultaneously with x-ray phase contrast imaging (XPCI) and Laue diffraction. Damage evolution is quantified with grayscale maps from XPCI. Single-crystal Si exhibits pronounced anisotropy in fracture modes, and thus fracture strengths and damage evolution. For loading along [11¯ 0] and viewing along [001], (1¯1¯0)[11¯ 0] cleavage is activated and induces horizontal primary cracks followed by perpendicular wing cracks. However, for loading along [011¯] and viewing along [111], random nucleation and growth of shear and tensile-splitting crack networks lead to catastrophic failure of materials with no cleavage. The primary-wing crack mode leads to a lower characteristic fracture strength due to predamage, but a more concentrated strength distribution, i.e., a higher Weibull modulus, compared to the second loading case. Furthermore, the sequential primary cracking, wing cracking and wing-crack coalescence processes result in a gradual increase of damage with time, deviating from theoretical predictions. Particle size and aspect ratios of fragments are discussed with postmortem fragment analysis, which verifies fracture modes observed in XPCI.

  10. Precision single mode fibre integral field spectroscopy with the RHEA spectrograph

    NASA Astrophysics Data System (ADS)

    Rains, Adam D.; Ireland, Michael J.; Jovanovic, Nemanja; Feger, Tobias; Bento, Joao; Schwab, Christian; Coutts, David W.; Guyon, Olivier; Arriola, Alexander; Gross, Simon

    2016-08-01

    The RHEA Spectrograph is a single-mode echelle spectrograph designed to be a replicable and cost effective method of undertaking precision radial velocity measurements. Two versions of RHEA currently exist, one located at the Australian National University in Canberra, Australia (450 - 600nm wavelength range), and another located at the Subaru Telescope in Hawaii, USA (600 - 800 nm wavelength range). Both instruments have a novel fibre feed consisting of an integral field unit injecting light into a 2D grid of single mode fibres. This grid of fibres is then reformatted into a 1D array at the input of the spectrograph (consisting of the science fibres and a reference fibre capable of receiving a white-light or xenon reference source for simultaneous calibration). The use of single mode fibres frees RHEA from the issue of modal noise and significantly reduces the size of the optics used. In addition to increasing the overall light throughput of the system, the integral field unit allows for cutting edge science goals to be achieved when operating behind the 8.2m Subaru Telescope and the SCExAO adaptive optics system. These include, but are not limited to: resolved stellar photospheres; resolved protoplanetary disk structures; resolved Mira shocks, dust and winds; and sub-arcsecond companions. We present details and results of early tests of RHEA@Subaru and progress towards the stated science goals.

  11. Dynamic deformation and fracture of single crystal silicon: Fracture modes, damage laws, and anisotropy

    DOE PAGES

    Huang, J. Y.; E, J. C.; Huang, J. W.; ...

    2016-05-25

    Impact fracture of single-crystal Si is critical to long-term reliability of electronic devices and solar cells for its wide use as components or substrates in semiconductor industry. Single-crystal Si is loaded along two different crystallographic directions with a split Hopkinson pressure bar integrated with an in situ x-ray imaging and diffraction system. Bulk stress histories are measured, simultaneously with x-ray phase contrast imaging (XPCI) and Laue diffraction. Damage evolution is quantified with grayscale maps from XPCI. Single-crystal Si exhibits pronounced anisotropy in fracture modes, and thus fracture strengths and damage evolution. For loading along [11¯ 0] and viewing along [001],more » (1¯1¯0)[11¯ 0] cleavage is activated and induces horizontal primary cracks followed by perpendicular wing cracks. However, for loading along [011¯] and viewing along [111], random nucleation and growth of shear and tensile-splitting crack networks lead to catastrophic failure of materials with no cleavage. The primary-wing crack mode leads to a lower characteristic fracture strength due to predamage, but a more concentrated strength distribution, i.e., a higher Weibull modulus, compared to the second loading case. Furthermore, the sequential primary cracking, wing cracking and wing-crack coalescence processes result in a gradual increase of damage with time, deviating from theoretical predictions. Particle size and aspect ratios of fragments are discussed with postmortem fragment analysis, which verifies fracture modes observed in XPCI.« less

  12. Using short helically wrapped single-mode fibers as illuminated fiducials

    NASA Astrophysics Data System (ADS)

    Ishikawa, Yuzo; Edelstein, Jerry; Silber, Joseph H.; Poppett, Claire

    2016-09-01

    The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment to map the large-scale structure of the universe and to probe the nature of dark energy. DESI is a massively multiplexed fiber-fed spectrograph, using a 5000-ffber-positioner focal plane assembly to image millions of galaxies. Since these fiber positioners must be positioned to 10-um accuracy, the focal plane must be mapped to micron level precision. We intend to use illuminated fiducials as point sources to accurately calibrate the focal plane surface. In this study we explored using short single-mode fibers as illuminated fiducials. However, despite the advantages of using single-mode fibers, as a near point source, optical fibers have length-dependence behavior: as shorter tend to guide core light into the cladding, which is not ideal for fiducial centroid-measurements. In this paper, we demonstrate that adding tight helical bends to the fibers eliminates unwanted flux in the cladding, improving centroid measurements by more than 50%. This technique has proven with fibers as short as 2-inches, obtaining centroid with at least 0.5-micron precision. This experiment eliminates fiber-length dependence, thus proving the viability of using short single-mode fibers as illuminated fiducials or similar applications

  13. Sensitive sandwich immunoassay based on single particle mode inductively coupled plasma mass spectrometry detection.

    PubMed

    Liu, Rui; Xing, Zhi; Lv, Yi; Zhang, Sichun; Zhang, Xinrong

    2010-11-15

    A sensitive sandwich type immunoassay has been proposed with the detection by inductively coupled plasma mass spectrometry (ICP-MS) in a single particle mode (time resolved analysis). The signal induced by the flash of ions ((197)Au(+)) due to the ionization of single Au-nanoparticle (Au-NP) label in the plasma torch can be measured by the mass spectrometer. The frequency of the transient signals is proportional to the concentration of Au-NPs labels. Characteristics of the signals obtained from Au-NPs of 20, 45 and 80 nm in diameters were discussed. The analytical figures for the determination of Au-labeled IgG using ICP-MS in conventional integral mode and single particle mode were compared in detail. Rabbit-anti-human IgG was used as a model analyte in the sandwich immunoassay. A detection limit (3 σ) of 0.1 ng mL(-1) was obtained for rabbit-anti-human IgG after immunoreactions, with a linear range of 0.3-10 ng mL(-1) and a RSD of 8.1% (2.0 ng mL(-1)). Finally, the proposed method was successfully applied to spiked rabbit-anti-human IgG samples and rabbit-anti-human serum samples. The method resulted to be a highly sensitive ICP-MS based sandwich type immunoassay.

  14. Design and experiments of a linear piezoelectric motor driven by a single mode

    NASA Astrophysics Data System (ADS)

    Liu, Zhen; Yao, Zhiyuan; Li, Xiang; Fu, Qianwei

    2016-11-01

    In this contribution, we propose a novel linear piezoelectric motor with a compact stator that is driven by a single mode. The linear piezoelectric motor can realize bidirectional motion by changing the vibration modes of the stator. Finite element analysis is performed to determine the required vibration mode of the stator and obtain the optimal stator structure and dimensions. Furthermore, the trajectories of the driving foot are analyzed with and without consideration of the mechanical contact with the slider. It is shown that the trajectory of the driving foot is an oblique line when disregarding the contact, and the trajectory becomes an oblique ellipse while taking into account the contact. Finally, a prototype of the motor is fabricated based on the results of finite element analysis. The optimization results show that the motor reaches its maximum thrust force of 4.0 kg, maximum thrust-weight ratio of 33.3, maximum unloaded velocity of 385 mm/s under the excitation of Mode-B, and maximum unloaded velocity of 315 mm/s under the excitation of Mode-L.

  15. Defect modes properties in self-similar fractal multilayer structures containing lossless single negative metamaterials

    NASA Astrophysics Data System (ADS)

    Rahimi, H.; Rezaei, M.

    2013-08-01

    Transfer matrix method is used to investigate the electromagnetic transmission spectra of a one-dimensional photonic fractal multilayer structure composed of single-negative metamaterial when common positive dielectric defect layers of are introduced. It is found that the frequency of the resonance defect modes can be tuned independently by varying the defect layer thicknesses. It is also found that by increasing the value of refractive index of defect layers and the number of periods, the full width half maximum of defect modes will be narrowed and shifted to lower frequencies. Also, our investigations show that for both TE and TM polarizations moving away from normal incidence to oblique incidence shows that the defect modes shift to upper frequencies. In other words, the defect modes inside the band gap depend on the incident angle and polarization. More interesting, for angles of incidence greater than 55° the defect modes for TE polarization (unlike to TM polarization) are eliminated. Moreover, the electromagnetic fields in the defect layers are strongly localized, and they can be excite independently. We believe that the proposed fractal structures can be useful in designing tunable independently high-Q filters with specific channels by adjusting their structural parameters.

  16. Design and experiments of a linear piezoelectric motor driven by a single mode.

    PubMed

    Liu, Zhen; Yao, Zhiyuan; Li, Xiang; Fu, Qianwei

    2016-11-01

    In this contribution, we propose a novel linear piezoelectric motor with a compact stator that is driven by a single mode. The linear piezoelectric motor can realize bidirectional motion by changing the vibration modes of the stator. Finite element analysis is performed to determine the required vibration mode of the stator and obtain the optimal stator structure and dimensions. Furthermore, the trajectories of the driving foot are analyzed with and without consideration of the mechanical contact with the slider. It is shown that the trajectory of the driving foot is an oblique line when disregarding the contact, and the trajectory becomes an oblique ellipse while taking into account the contact. Finally, a prototype of the motor is fabricated based on the results of finite element analysis. The optimization results show that the motor reaches its maximum thrust force of 4.0 kg, maximum thrust-weight ratio of 33.3, maximum unloaded velocity of 385 mm/s under the excitation of Mode-B, and maximum unloaded velocity of 315 mm/s under the excitation of Mode-L.

  17. 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.

  18. Dual-mode sorption model for single- and multisolute sorption onto organoclays

    SciTech Connect

    Huh, J.K.; Song, D.I.; Jeon, Y.W.

    1999-02-01

    The dual-mode sorption model (DSM) was applied to the single-solute sorption of 2-chlorophenol, 3-cyanophenol, and 4-nitrophenol from water onto organoclays. The three parameters contained in the DSM were determined for each solute by fitting to the single-solute isotherm data and subsequently utilized in competitive multisolute sorptions. A systematic method to determine the parameters for each solute was also suggested. The ideal adsorbed solution theory (IAST) coupled with the single-solute DSM and the competitive dual-mode sorption model (CDSM) extended to describe multisolute sorption were used to predict multisolute sorption onto organoclays and compared with the data to determine the predictive capabilities. The DSM was found to describe well single-solute sorption from water onto organoclays. The predictions from the CDSM and the IAST based on the DSM, though rather poor for some solutes, were generally in agreement with the multisolute sorption data. However,the authors could not tell at this stage which of the two competitive models is better.

  19. Identification of immobile single molecules using polarization-modulated asynchronous TDI-mode scanning

    PubMed Central

    Jacak, Jaroslaw; Hesch, Clemens; Hesse, Jan; Schütz, Gerhard J.

    2015-01-01

    We report the development of a data acquisition method for identifying single molecules on large surfaces with simultaneous characterization of their absorption dipole. The method is based on a previously described device for microarray readout at single molecule sensitivity1. Here, we introduced asynchronous time delay and integration- (TDI-) mode imaging to record also the time course of fluorescence signals: the images thus contain both spatial and temporal information. We demonstrate the principle by modulating the signals via rotating excitation polarization, which allows for discriminating static absorption dipoles against multiple or freely rotating single absorption dipoles. Experiments on BSA carrying different numbers of fluorophores demonstrate the feasibility of the method. Protein species with average labeling degree of 0.55 and 2.89 fluorophores per protein can be readily distinguished. PMID:20380382

  20. 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.

  1. Experimental investigation of thermally induced core laser leakage in large mode area single trench fiber

    NASA Astrophysics Data System (ADS)

    Kong, Lingchao; Huang, Liangjin; Gu, Shaoyi; Leng, Jinyong; Guo, Shaofeng; Zhou, Pu; Xu, Xiaojun; Jiang, Zongfu

    2016-11-01

    We demonstrated a new phenomenon, namely, thermally induced core laser leakage in single trench fiber (STF), for the first time. The STF provides very high loss and power delocalization of higher order mode (HOM) and maintain the effective single mode operation. However these properties are chartered only under low power situations. In this paper we established a 976nm directly pumped high power co-pumping fiber amplifier based on the STF. The maximum output power was 1022W with a slope efficiency of 76%. Further increase the pump power will leads to the output power decrease. Meanwhile a micro second Level noise like power fluctuation was observed. No resonance frequency was observed in frequency domain indicating the mode instability is not triggered. We believe that it is the thermally induced waveguide index profile change due to the excessively heat load in the front section of STF that leads to the failure of HOM suppression and the power of FM was coupled into the HOM. However the heat load in the rear section of STF was relatively low and the HOM leaked into the cladding due to the bending loss. We provide a mitigating method by pumping with pump light of smaller absorption. A maximum power of 1330W was achieved without power decrease via pumping the STF with 905nm and 976nm pump light (same amplifier). To our best knowledge, this is the first demonstration of thermally induced core laser leakage in STF and the pertinent results can provide significant reference for future optimization.

  2. On the single-photon-counting (SPC) modes of imaging using an XFEL source

    DOE PAGES

    Wang, Zhehui

    2015-12-14

    In this study, the requirements to achieve high detection efficiency (above 50%) and gigahertz (GHz) frame rate for the proposed 42-keV X-ray free-electron laser (XFEL) at Los Alamos are summarized. Direct detection scenarios using C (diamond), Si, Ge and GaAs semiconductor sensors are analyzed. Single-photon counting (SPC) mode and weak SPC mode using Si can potentially meet the efficiency and frame rate requirements and be useful to both photoelectric absorption and Compton physics as the photon energy increases. Multilayer three-dimensional (3D) detector architecture, as a possible means to realize SPC modes, is compared with the widely used two-dimensional (2D) hybridmore » planar electrode structure and 3D deeply entrenched electrode architecture. Demonstration of thin film cameras less than 100-μm thick with onboard thin ASICs could be an initial step to realize multilayer 3D detectors and SPC modes for XFELs.« less

  3. Selective coherent phonon-mode generation in single-wall carbon nanotubes.

    PubMed

    Nugraha, Ahmad R T; Hasdeo, Eddwi H; Saito, Riichiro

    2017-02-08

    The pulse-train technique within ultrafast pump-probe spectroscopy is theoretically investigated to excite a specific coherent phonon mode while suppressing the other phonon modes generated in single-wall carbon nanotubes (SWNTs). In particular, we focus on the selectivity of the radial breathing mode (RBM) and the G-band for a given SWNT. We find that if the repetition period of the pulse train matches with the integer multiple of the RBM phonon period, the RBM amplitude can be maintained while the amplitudes of the other modes are suppressed. As for the G-band, when we apply a repetition period of a half-integer multiple of the RBM period, the RBM can be suppressed because of destructive interference, while the G-band still survives. It is also possible to keep the G-band and suppress the RBM by applying a repetition period that matches with the integer multiple of the G-band phonon period. However, in this case we have to use a large number of laser pulses having a property of "magic ratio" of the G-band and RBM periods.

  4. Selective coherent phonon-mode generation in single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Nugraha, Ahmad R. T.; Hasdeo, Eddwi H.; Saito, Riichiro

    2017-02-01

    The pulse-train technique within ultrafast pump-probe spectroscopy is theoretically investigated to excite a specific coherent phonon mode while suppressing the other phonon modes generated in single-wall carbon nanotubes (SWNTs). In particular, we focus on the selectivity of the radial breathing mode (RBM) and the G-band for a given SWNT. We find that if the repetition period of the pulse train matches with the integer multiple of the RBM phonon period, the RBM amplitude can be maintained while the amplitudes of the other modes are suppressed. As for the G-band, when we apply a repetition period of a half-integer multiple of the RBM period, the RBM can be suppressed because of destructive interference, while the G-band still survives. It is also possible to keep the G-band and suppress the RBM by applying a repetition period that matches with the integer multiple of the G-band phonon period. However, in this case we have to use a large number of laser pulses having a property of “magic ratio” of the G-band and RBM periods.

  5. Observation of mode instability and coherence collapse in a single-frequency polarization-maintaining fiber ring laser

    NASA Astrophysics Data System (ADS)

    Ma, Mingxiang; Hu, Zhengliang; Xu, Pan; Hu, Yongming

    2014-06-01

    Mode instability acts as a common feature in single-frequency fiber ring lasers. The mechanism of coherence collapse by mode instability is theoretically analyzed and demonstrated with an unbalanced fiber Michelson interferometer utilizing phase modulation, which is illuminated by a single-frequency erbium-doped fiber ring laser. Multiform mode instability phenomena accompanied with coherence collapse are observed and discussed in detail by tracing the dynamics of the interference fringe visibility. The results show that mode instability would introduce extra phase noises like a false alarm to interferometric fiber optic sensing systems.

  6. Coupling between flexural modes in free vibration of single-walled carbon nanotubes

    SciTech Connect

    Liu, Rumeng; Wang, Lifeng

    2015-12-15

    The nonlinear thermal vibration behavior of a single-walled carbon nanotube (SWCNT) is investigated by molecular dynamics simulation and a nonlinear, nonplanar beam model. Whirling motion with energy transfer between flexural motions is found in the free vibration of the SWCNT excited by the thermal motion of atoms where the geometric nonlinearity is significant. A nonlinear, nonplanar beam model considering the coupling in two vertical vibrational directions is presented to explain the whirling motion of the SWCNT. Energy in different vibrational modes is not equal even over a time scale of tens of nanoseconds, which is much larger than the period of fundamental natural vibration of the SWCNT at equilibrium state. The energy of different modes becomes equal when the time scale increases to the microsecond range.

  7. 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.

  8. Microwave measurements of energy lost to longitudinal modes by single electron bunches traversing periodic structures

    SciTech Connect

    Wang, J.W.; Loew, G.A.; Weaver, J.N.; Wilson, P.B.

    1981-10-01

    In the design of future linear colliders, it will be important to minimize the loss of beam energy due to the excitation of higher-order modes in the accelerator structure by single bunches of electrons or positrons. This loss is not only detrimental in itself but also gives rise to energy spectrum widening and transverse emittance growth. Microwave measurements made on disk-loaded and alternating-spoke structures to determine the loss to the longitudinal modes are described. In these measurements the Gaussian bunch is simulated by a current pulse of the same shape transmitted through the structure on an axial center conductor. Results to date are presented for the total longitudinal loss parameter per period K in volts per picocoulomb.

  9. Evaluation of single photon and Geiger mode Lidar for the 3D Elevation Program

    USGS Publications Warehouse

    Stoker, Jason M.; Abdullah, Qassim; Nayegandhi, Amar; Winehouse, Jayna

    2016-01-01

    Data acquired by Harris Corporation’s (Melbourne, FL, USA) Geiger-mode IntelliEarth™ sensor and Sigma Space Corporation’s (Lanham-Seabrook, MD, USA) Single Photon HRQLS sensor were evaluated and compared to accepted 3D Elevation Program (3DEP) data and survey ground control to assess the suitability of these new technologies for the 3DEP. While not able to collect data currently to meet USGS lidar base specification, this is partially due to the fact that the specification was written for linear-mode systems specifically. With little effort on part of the manufacturers of the new lidar systems and the USGS Lidar specifications team, data from these systems could soon serve the 3DEP program and its users. Many of the shortcomings noted in this study have been reported to have been corrected or improved upon in the next generation sensors.

  10. Report on first masing and single mode locking in a prebunched beam FEM oscillator

    SciTech Connect

    Cohen, M.; Eichenbaum, A.; Kleinman, H.

    1995-12-31

    Radiation characteristics of a table-top free electron maser (FEM) are described in this paper. The FEM employs a prebunched electron beam and is operated as an oscillator in the low-gain collective (Raman) regime. Using electron beam prebunching single mode locking at any one of the possible oscillation modes was obtained. The electron beam is prebunched by a microwave tube section before it is injected into the wiggler. By tuning the electron beam bunching frequency, the FEM oscillation frequency can be locked to any eigen frequency of the resonant waveguide cavity which is within the frequency band of net gain of the FEM. The oscillation build up process is sped up, when the FEM operates with a prebunched electron beam, and the build-up time of radiation is shortened significantly. First measurements of masing with and without prebunching and characterization of the emitted radiation are reported.

  11. Single-mode tapered optical fiber loop immunosensor II: assay of anti-cholera toxin immunoglobulins

    NASA Astrophysics Data System (ADS)

    Marks, Robert S.; Hale, Zoe M.; Levine, Myron M.; Lowe, C. R.; Payne, Frank P.

    1994-07-01

    An evanescent wave immunoassay for cholera antitoxin immunoglobulins was performed using a single mode tapered optical fiber loop sensor. The transducer was silanized with 3- glycidoxypropyltrimethoxysilane and chemically modified to link covalently either cholera toxin B subunit or a synthetic peptide derived from it, CTP3. The sensor was exposed to seral fluids, obtained from human volunteers having been exposed to live virulent Vibrio cholerae 01 and shown to produce rice-water stools. Other toxins of interest, such as Clostridium botulinum toxin A, have been tested on similar systems. The bound unlabelled immunoglobulins were then exposed to a mixture of FITC-anti-IgG and TRITC-anti-IgA, without requirement for a separation step. The emanating fluorescent emissions of fluorescein and rhodamine, excited by the input laser light, were coupled back into the guided mode of the tapered fiber, and used to determine the concentrations of the complementary antigens.

  12. Single-Mode Projection Filters for Modal Parameter Identification for Flexible Structures

    NASA Technical Reports Server (NTRS)

    Huang, Jen-Kuang; Chen, Chung-Wen

    1988-01-01

    Single-mode projection filters are developed for eigensystem parameter identification from both analytical results and test data. Explicit formulations of these projection filters are derived using the orthogonal matrices of the controllability and observability matrices in the general sense. A global minimum optimization algorithm is applied to update the filter parameters by using the interval analysis method. The updated modal parameters represent the characteristics of the test data. For illustration of this new approach, a numerical simulation for the MAST beam structure is shown by using a one-dimensional global optimization algorithm to identify modal frequencies and damping. Another numerical simulation of a ten-mode structure is also presented by using a two-dimensional global optimization algorithm to illustrate the feasibility of the new method. The projection filters are practical for parallel processing implementation.

  13. Space-efficient fiber ribbon composed of reduced-cladding single-mode fibers

    NASA Astrophysics Data System (ADS)

    Chang, J. H.; Bae, S. H.; Kim, Hoon; Ouh, C. H.; Jung, C. H.; Cho, H. S.; Chung, Y. C.

    2016-09-01

    We develop a space-efficient single-mode fiber (SMF) having a cladding diameter of only 82 μm. This SMF has the depressed-cladding index profile and its mode-field diameter, cutoff wavelength, and macro bending loss are designed to be similar to those of the conventional step-index SMF. We fabricate this reduced-cladding SMF and measure its optical and mechanical characteristics. The results show that this fiber satisfies major specifications of the ITU-T G.654 recommendations. We also fabricate a fiber ribbon by using twelve of these reduced-cladding SMFs. Compared to a commercial fiber ribbon made of twelve standard SMFs having 125-μm cladding diameter, this fiber ribbon can improve the spatial efficiency by ∼75%.

  14. Nonlinear anisotropic description for shocked single crystals: Thermoelastic response and pure mode wave propagation

    NASA Astrophysics Data System (ADS)

    Winey, J. M.; Gupta, Y. M.

    2004-08-01

    An anisotropic continuum framework for describing the nonlinear thermoelastic response of shocked single crystals has been developed. Using this framework, the propagation of large amplitude stress waves along arbitrary directions in crystals of any symmetry can be examined. We developed an incremental approach, where the reference state for the dynamical variables and the material properties is updated throughout the calculation. Results from our incremental approach are in excellent agreement with the results from a finite strain formulation. Using a finite-difference wave propagation code, we performed numerical simulations of large amplitude elastic wave propagation in single crystals. Results of impact loading simulations for quartz and sapphire single crystals are presented. The framework developed was also useful for examining the propagation of pure mode nonlinear waves for various crystal symmetries. Our calculations showed that pure longitudinal waves resulted from impact loading along any rotational symmetry axis for all crystal symmetry classes. Differences between pure mode wave propagation for linear and nonlinear elastic deformation are discussed.

  15. Interaction of High Frequency Acoustic Waves and Optical Waves Propagating in Single Mode Fibers.

    NASA Astrophysics Data System (ADS)

    de Paula, Ramon Perez

    This paper develops a frequency dependent model for the acousto-optic interaction with a single mode fiber of acoustic waves having wavelengths comparable to the fiber diameter. This paper also presents optical techniques for experimental observation and measurement of such effects. The acoustic waves are both normally and obliquelly incident on the fiber. The solutions to the elastic problem studied here are constructed using scalar and vector potentials. The principal strains induced by a plane wave propagating in a fluid is calculated through the solution of the wave equation and the associated boundary condition. The optical beam propagation is analyzed starting with Maxwell's, equations and the required solution for single mode (degenerate double mode) propagation is presented. For the perturbed fiber the anisotropic solution is discussed. The optical indicatrix is derived from the electric energy density, with the major axis parallel to the induced principal strains obtained from the solution of the elastic problem. The solution of the optical indicatrix equation (index ellipsoid) yields two independent propagation modes that are linear polarized plane waves with two different propagation velocities. The induced phase shift and birefringence are calculated from the index ellipsoid. The birefringence and phase shift are also measured experimentally using a fiber optic interferometer and a fiber optic polariscope. The experimental apparatus is discussed in detail and the techniques used to make the measurements are presented. The results are separated into two parts: first, the results for ultrasonic waves of normal incidence are presented, theoretical and experimental results are discussed, and the two compared; second, the results for angular incidence are presented in the same format as above, and compared with the results for perpendicular incidence.

  16. Self-mode-locked single-section Fabry-Perot semiconductor lasers at 1.56 microm.

    PubMed

    Yang, Weiguo; Sauer, Nicholas J; Bernasconi, Pietro G; Zhang, Liming

    2007-01-01

    The mode-locking mechanism of a single-section multi-spatial-mode Fabry-Perot semiconductor laser is analyzed by the additive pulse mode-locking (APM) master equation model. Critical parameters of the equivalent saturable absorber as well as the self-phase modulation are estimated. The mode-locking operation regime in terms of pulse chirp and output power is predicted by the APM model and the prediction is shown to be in good agreement with the experimental results of a 40 GHz, 6.7 ps pulse width mode-locked operation at 1.56 microm.

  17. Passively Q-switched Single-longitudinal-mode c-cut Nd:GdVO4 laser with a twisted-mode cavity.

    PubMed

    Pan, Haifeng; Xu, Shixiang; Zeng, Heping

    2005-04-04

    Single-longitudinal-mode operation is achieved in a twisted-mode-cavity c-cut Nd:GdVO4 laser. With a semiconductor saturable absorption mirror as an intracavity saturable absorber to launch passive Q-switching, no mode-locked spikes are observed on the temporal envelopes of the Q-switched output pulses due to the complete elimination of spatial hole burning in the gain medium to suppress longitudinal multi-modes. The maximal average output power is 1.24 W with the repetition rate of 76.3 kHz, and the single pulse energy is 16.0 microJ. The pulse width and polarization ratio of the output laser beam are measured about 150 ns and 53:1, respectively.

  18. 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.

  19. A high-performance single-mode fiber-optic isolator assembly

    NASA Technical Reports Server (NTRS)

    Lutes, G.

    1987-01-01

    A high-isolation single-mode fiber optic isolator assembly was designed and fabricated. The measured forward loss is 2.6 dB and the reverse loss (isolation) is greater than 70 dB. This is a 30-dB higher isolation than the isolation of the best fiber optic isolator previously reported. This isolator provides isolation between the semiconductor laser diode and the optical fiber in a precise reference frequency transmission system. The isolation of the laser greatly reduces the system's sensitivity to microphonics.

  20. In-line single-mode fiber variable optical attenuator based on electrically addressable microdroplets

    NASA Astrophysics Data System (ADS)

    Duduś, A.; Blue, R.; Zagnoni, M.; Stewart, G.; Uttamchandani, D.

    2014-07-01

    We report an in-line, fiber optic, broadband variable optical attenuator employing a side-polished, single-mode optical fiber integrated on a digital microfluidics platform. The system is designed to electrically translate a liquid droplet along the polished surface of an optical fiber using electrowetting forces. This fiber optic device has the advantage of no moving mechanical parts and lends itself to miniaturization. A maximum attenuation of 25 dB has been obtained in the wavelength range between 1520 nm and 1560 nm.

  1. 322 W single-mode Yb-doped all-fiber laser operated at 1120 nm

    NASA Astrophysics Data System (ADS)

    Zhang, Hanwei; Xiao, Hu; Zhou, Pu; Zhang, Kun; Wang, Xiaolin; Xu, Xiaojun

    2014-05-01

    An all-fiber, high-power, spectrally clean, single-mode Yb-doped fiber oscillator at 1120 nm wavelength is demonstrated. By optimizing the reflectivity of the output coupler and the length of the gain fiber, an output power of 322 W and an optical efficiency of 71% have been achieved. The output power, spectra, and bandwidth broadening are presented and briefly discussed. The power scaling capability of the cavity is analyzed on the basis of the thermal effect, and a maximal thermal-damage-free output power of 450 W could be expected.

  2. Supercontinuum generation by noise-like pulses transmitted through normally dispersive standard single-mode fibers.

    PubMed

    Zaytsev, Alexey; Lin, Chih-Hsuan; You, Yi-Jing; Chung, Chia-Chun; Wang, Chi-Luen; Pan, Ci-Ling

    2013-07-01

    We report generation of broadband supercontinuum (SC) by noise-like pulses (NLPs) with a central wavelength of 1070 nm propagating through a long piece of standard single-mode fibers (~100 meters) in normal dispersion region far from the zero-dispersion point. Theoretical simulations indicate that the physical mechanism of SC generation is due to nonlinear effects in fibers. The cascaded Raman scattering is responsible for significant spectral broadening in the longer wavelength regions whereas the Kerr effect results in smoothing of SC generated spectrum. The SC exhibits low threshold (43 nJ) and a flat spectrum over 1050-1250 nm.

  3. Single-longitudinal-mode BEFL incorporating a Bragg grating written in EDF

    NASA Astrophysics Data System (ADS)

    Gao, Ya; Sun, Junqiang; Chen, Guodong; Xie, Heng

    2015-06-01

    A stable and tunable single-longitudinal-mode (SLM) Brillouin/Erbium fiber laser (BEFL) with narrow linewidth is proposed and experimentally demonstrated. A uniform Bragg grating written in a segment of unpumped Erbium-doped fiber (EDF) is incorporated as an auto-tracking filter to achieve SLM operation. A length of 5 m pumped EDF is used to provide both Brillouin and linear gain in the cavity. The linewidth is measured to be 18 kHz and the lasing peak power fluctuation and wavelength shift are monitored less than 0.027 dB and 2 pm respectively.

  4. Highly damped quasinormal modes of generic single-horizon black holes

    NASA Astrophysics Data System (ADS)

    Daghigh, Ramin G.; Kunstatter, Gabor

    2005-10-01

    We calculate analytically the highly damped quasinormal mode spectra of generic single-horizon black holes using the rigorous WKB techniques of Andersson and Howls (2004 Class. Quantum Grav. 21 1623). We thereby provide a firm foundation for previous analysis, and point out some of their possible limitations. The numerical coefficient in the real part of the highly damped frequency is generically determined by the behaviour of coupling of the perturbation to the gravitational field near the origin, as expressed in tortoise coordinates. This fact makes it difficult to understand how the famous ln(3) could be related to the quantum gravitational microstates near the horizon.

  5. Single-mode fiber variable optical attenuator based on a ferrofluid shutter.

    PubMed

    Duduś, Anna; Blue, Robert; Uttamchandani, Deepak

    2015-03-10

    We report on the fabrication and characterization of a single-mode fiber variable optical attenuator (VOA) based on a ferrofluid shutter actuated by a magnetic field created by a low voltage electromagnet. We compare the performance of a VOA using oil-based ferrofluid, with one VOA using water-based 12 ferrofluid, and demonstrate broadband optical attenuation of up to 28 dB with polarization dependent 13 loss of 0.85 dB. Our optofluidic VOA has advantages over MEMS-based VOAs such as simple construction and the absence of mechanical moving parts.

  6. Observation of Single-Mode, Kelvin-Helmholtz Instability in a Supersonic Flow.

    PubMed

    Wan, W C; Malamud, G; Shimony, A; Di Stefano, C A; Trantham, M R; Klein, S R; Shvarts, D; Kuranz, C C; Drake, R P

    2015-10-02

    We report the first observation, in a supersonic flow, of the evolution of the Kelvin-Helmholtz instability from a single-mode initial condition. To obtain these data, we used a novel experimental system to produce a steady shock wave of unprecedented duration in a laser-driven experiment. The shocked, flowing material creates a shear layer between two plasmas at high energy density. We measured the resulting interface structure using radiography. Hydrodynamic simulations reproduce the large-scale structures very well and the medium-scale structures fairly well, and imply that we observed the expected reduction in growth rate for supersonic shear flow.

  7. Cladding waveguide gratings in standard single-mode fiber for 3D shape sensing.

    PubMed

    Waltermann, Christian; Doering, Alexander; Köhring, Michael; Angelmahr, Martin; Schade, Wolfgang

    2015-07-01

    Femtosecond laser pulses were used for the direct point-by-point inscription of waveguides into the cladding of standard single-mode fibers. Homogeneous S-shaped waveguides have been processed as a bundle of overlapping lines without damaging the surrounding material. Within these structures, FBGs have been successfully inscribed and characterized. A sensor device to measure the bending direction of a fiber was created by two perpendicular inscribed cladding waveguides with FBG. Finally, a complete 3D shape sensor consisting of several bending sensor planes, capable of detecting bending radii even below 2.5 cm is demonstrated.

  8. Low-loss single-mode integrated waveguides in soda-lime glass

    NASA Astrophysics Data System (ADS)

    Dyakonov, I. V.; Kalinkin, A. A.; Saygin, M. Yu.; Abroskin, A. G.; Radchenko, I. V.; Straupe, S. S.; Kulik, S. P.

    2016-09-01

    Low-loss single-mode optical waveguide fabrication process in extra-white soda-lime glass is demonstrated. Waveguiding structures are formed in bulk substrates employing femtosecond laser writing technology. The combination of a slit beam shaping method and a multiscan fabrication process enables writing of waveguides with a well-defined symmetric cross-sectional profile. Fabricated waveguides exhibit 0.86 dB/cm propagation loss for 800-nm wavelength. Bending loss in the waveguides is addressed experimentally and compared with a model for radiation loss.

  9. Frequency noise suppression of a single mode laser with an unbalanced fiber interferometer for subnanometer interferometry.

    PubMed

    Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Číp, Ondřej

    2015-01-12

    We present a method of noise suppression of laser diodes by an unbalanced Michelson fiber interferometer. The unstabilized laser source is represented by compact planar waveguide external cavity laser module, ORIONTM (Redfern Integrated Optics, Inc.), working at 1540.57 nm with a 1.5-kHz linewidth. We built up the unbalanced Michelson interferometer with a 2.09 km-long arm based on the standard telecommunication single-mode fiber (SMF-28) spool to suppress the frequency noise by the servo-loop control by 20 dB to 40 dB within the Fourier frequency range, remaining the tuning range of the laser frequency.

  10. Narrow linewidth single-mode semiconductor laser development for coherent detection lidar

    NASA Technical Reports Server (NTRS)

    Mansour, Kamjou; Ksendzov, Alexander; Menzies, Robert T.; Maker, Paul D.; Muller, Richard E.; Manfra, M. J.; Turner, George W.

    2003-01-01

    High power, tunable, single mode, narrow linewidth semiconductor lasers in the 2.05-(micro)m wavelength region are needed to develop semiconductor laser reference oscillators for optical remote sensing from Earth orbit. 2.05-I1/4m narrow linewidth monolithic distributed feedback (DFB) and distributed Bragg reflector (DBR) with the external grating ridge waveguide lasers fabricated from epitaxially grown InGaAs/InGaAsP/InP and in InGaAsSb/AlGaAsSb/GaSb heterostructures are reported.

  11. 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.

  12. Deep nulling of laser light with a single-mode-fiber beam combiner.

    PubMed

    Haguenauer, Pierre; Serabyn, Eugene

    2006-04-20

    The detection of faint companions to bright stars requires the development of very-high-contrast-ratio detection techniques such as nulling interferometry. Here we present, to our knowledge, the first experimental test of a novel beam-combination method, which is based on coupling the light at the center of a dual-aperture interference pattern into a single-mode fiber. Using such a "fiber nuller" approach, a visible He-Ne laser has been stably nulled to as low as 1.3x10(-6), thus validating the approach.

  13. Fast random number generation with spontaneous emission noise of a single-mode semiconductor laser

    NASA Astrophysics Data System (ADS)

    Zhang, Jianzhong; Zhang, Mingjiang; Liu, Yi; Li, Pu; Yi, Xiaogang; Zhang, Mingtao; Wang, Yuncai

    2016-11-01

    We experimentally demonstrate a 12.5 Gb s-1 random number generator based on measuring the spontaneous emission noise of a single-mode semiconductor laser. The spontaneous emission of light is quantum mechanical in nature and is an inborn physical entropy source of true randomness. By combining a high-speed analog-to-digital converter and off-line processing, random numbers are extracted from the spontaneous emission with the verified randomness. The generator is simple, robust, and with no need of accurately tuning the comparison threshold. The use of semiconductor lasers makes it particularly compatible with the delivery of random numbers in optical networks.

  14. Preliminary results on the simultaneous excitation of the TM_010 and TE_011 MODES in a single cell niobium cavity

    SciTech Connect

    G. Ciovati; P. Kneisel

    2005-05-01

    Simultaneous excitation of both modes has been carried out on a CEBAF single cell cavity. The cavity has two beam pipe side-ports for each mode for input and pick-up couplers. Coupling to the TE011 mode is done by magnetic loop couplers while for the TM010 mode coaxial antennas are used. Simultaneous excitation of both TM and TE modes has been proposed recently for superconducting photoinjector applications to take advantage of the accelerating electric field of the TM mode, combined with the focusing magnetic field of the TE mode. The TE011 mode has the property of having zero surface electric field, surface magnetic field orthogonal to the one in the TM010 mode and concentrated in the iris/wall regions of the cavity. The presence of both modes in the cavity at the same time can also be used to investigate the so-called high field Q-drop in the TM010 mode. This paper will present some preliminary result on the test of the single cell cavity at 2 K.

  15. Entanglement Involved in Time Evolution of Two-Mode Squeezed State in Single-Mode Diffusion Channel

    NASA Astrophysics Data System (ADS)

    Xu, Xue-Fen; Fan, Hong-Yi

    2017-02-01

    We derive the evolution law of an initial two-mode squeezed vacuum state sech2λ e^{a^{dag }b^{dagger }tanh λ }\\vert 00rangle < 00\\vert e^{ab tanh λ } (a pure state) passing through an a-mode diffusion channel described by the master equation dρ ( t) /dt=-κ [ a^{dagger}aρ ( t) -a^{dagger}ρ ( t) a-aρ ( t) a^{dagger}+ρ ( t) aa^{dagger}] , since the two-mode squeezed state is simultaneously an entangled state, the final state which emerges from this channel is a two-mode mixed state. Performing partial trace over the b-mode of ρ(t) yields a new chaotic field, ρ a(t) = {sech2λ}/{1+κt sech2λ}:exp [ {-sech2λ}/{1+κt sech2λ }a^{dagger }a ] :, which exhibits higher temperature and more photon numbers, showing the diffusion effect. Besides, measuring a-mode of ρ(t) to find n photons will result in the collapse of the two-mode system to a new Laguerre polynomial-weighted chaotic state in b-mode, which also exhibits entanglement.

  16. A Comparison of Single-Molecule Emission in Aluminum and Gold Zero-Mode Waveguides

    SciTech Connect

    Martin, William Elliott; Srijanto, Bernadeta R.; Collier, C. Patrick; Vosch, Tom; Richards, Christopher I.

    2016-08-06

    We characterized the effect of gold and aluminum zero-mode waveguides (ZMWs) on the brightness of immobilized single emitters by probing fluorophores that absorb in the green and red regions of the visible spectrum. Aluminum ZMWs enhance the emission of Atto565 fluorophores upon green excitation, but they do not enhance the emission of Atto647N fluorophores upon red excitation. Gold ZMWs increase emission of both fluorophores with Atto647N showing enhancement that is threefold higher than that observed for Atto565. Our work indicates that 200 nm gold ZMWs are better suited for single-molecule fluorescence studies in the red region of the visible spectrum, while aluminum appears more suited for the green region of the visible spectrum.

  17. A Comparison of Single-Molecule Emission in Aluminum and Gold Zero-Mode Waveguides

    DOE PAGES

    Martin, William Elliott; Srijanto, Bernadeta R.; Collier, C. Patrick; ...

    2016-08-06

    We characterized the effect of gold and aluminum zero-mode waveguides (ZMWs) on the brightness of immobilized single emitters by probing fluorophores that absorb in the green and red regions of the visible spectrum. Aluminum ZMWs enhance the emission of Atto565 fluorophores upon green excitation, but they do not enhance the emission of Atto647N fluorophores upon red excitation. Gold ZMWs increase emission of both fluorophores with Atto647N showing enhancement that is threefold higher than that observed for Atto565. Our work indicates that 200 nm gold ZMWs are better suited for single-molecule fluorescence studies in the red region of the visible spectrum,more » while aluminum appears more suited for the green region of the visible spectrum.« less

  18. The whispering gallery mode biosensor: label-free detection from virus to single protein

    NASA Astrophysics Data System (ADS)

    Holler, S.; Dantham, V. R.; Keng, D.; Kolchenko, V.; Arnold, S.; Mulroe, Brigid; Paspaley-Grbavac, M.

    2014-08-01

    The whispering gallery mode (WGM) biosensor is a micro-optical platform capable of sensitive label-free detection of biological particles. Described by the reactive sensing principle (RSP), this analytic formulation quantifies the response of the system to the adsorption of bioparticles. Guided by the RSP, the WGM biosensor enabling from detection of virus (e.g., Human Papillomavirus, HPV) to the ultimate goal of single protein detection. The latter was derived from insights into the RSP, which resulted in the development of a hybrid plasmonic WGM biosensor, which has recently demonstrated detection of individual protein cancer markers. Enhancements from bound gold nanoparticles provide the sensitivity to detect single protein molecules (66 kDa) with good signal-to-noise (S/N > 10), and project that detection of proteins as small as 5 kDa.

  19. Hamiltonian of photons in a single-mode optical fiber for quantum communications protocols

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, G. P.

    2012-05-01

    A phenomenological Hamiltonian of photons in a single-mode stochastic inhomogeneous optical fiber (OF) is derived. Quantization of radiation is performed in the basis of an ideal OF with proper calibration that ensures transversality of the electric-field-displacement vector. Stochastic parameters of the Hamiltonian are determined by using the reciprocal tensor of the dielectric permittivity averaged over the OF segment volume. The Hamiltonian is parametrized by three phenomenological parameters and preserves the number of photons. It is assumed that the segment of the OF is divided into random subsegments with optical parameters defined by the Wiener process with respect to the longitudinal coordinate. The temporal dynamics of the single-photon density matrix is analyzed in the basis of states with orthogonal polarizations. The relative quantum beat error rate in the sifted quantum key distributed according to the BB84 protocol with polarization coding of information averaged over the scatter of the OF parameters is calculated.

  20. Imaging single photons in non-separable states of polarization and spatial-mode

    NASA Astrophysics Data System (ADS)

    Cheng, Xinru; Galvez, Enrique J.

    2014-10-01

    Non-separable superpositions of polarization and spatial mode of a single photon produce a state that has a polarization that depends on the transverse position, and contains all states of polarization represented on the Poincaré sphere. We have done measurements of the space-dependent state of polarization of single photons prepared in distinct 2×2 (qubit-qubit) and 2×3 (qubit-qutrit) non-separable superpositions of Laguerre-Gauss spatial and polarization states. Detection was done by polarimetry of the light projected at distinct locations in the transverse plane. The polarization patterns had a C-point polarization singularity (lemon, star or monstar) at the center of the transverse wavefunction.

  1. Sequential elution of multiply and singly phosphorylated peptides with polar-copolymerized mixed-mode RP18/SCX material.

    PubMed

    Li, Xiuling; Guo, Zhimou; Sheng, Qianying; Xue, Xingya; Liang, Xinmiao

    2012-06-21

    Novel polar-copolymerized mixed-mode RP18/SCX material was developed for feasible phosphopeptide enrichment, in which multiply and singly phosphorylated peptides could be sequentially eluted and separated with high selectivity.

  2. Feasibility of Coupling Between a Single-Mode Elliptical-Core Fiber and a Single Mode Rib Waveguide Over Temperature. Ph.D. Thesis - Akron Univ., Aug. 1995

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret L.

    1995-01-01

    To determine the feasibility of coupling the output of an optical fiber to a rib waveguide in a temperature environment ranging from 20 C to 300 C, a theoretical calculation of the coupling efficiency between the two was investigated. This is a significant problem which needs to be addressed to determine whether an integrated optic device can function in a harsh temperature environment. Because the behavior of the integrated-optic device is polarization sensitive, a polarization-preserving optic fiber, via its elliptical core, was used to couple light with a known polarization into the device. To couple light energy efficiently from an optical fiber into a channel waveguide, the design of both components should provide for well-matched electric field profiles. The rib waveguide analyzed was the light input channel of an integrated-optic pressure sensor. Due to the complex geometry of the rib waveguide, there is no analytical solution to the wave equation for the guided modes. Approximation or numerical techniques must be utilized to determine the propagation constants and field patterns of the guide. In this study, three solution methods were used to determine the field profiles of both the fiber and guide: the effective-index method (EIM), Marcatili's approximation, and a Fourier method. These methods were utilized independently to calculate the electric field profile of a rib channel waveguide and elliptical fiber at two temperatures, 20 C and 300 C. These temperatures were chosen to represent a nominal and a high temperature that the device would experience. Using the electric field profile calculated from each method, the theoretical coupling efficiency between the single-mode optical fiber and rib waveguide was calculated using the overlap integral and results of the techniques compared. Initially, perfect alignment was assumed and the coupling efficiency calculated. Then, the coupling efficiency calculation was repeated for a range of transverse offsets at

  3. Optimizing single mode robustness of the distributed modal filtering rod fiber amplifier.

    PubMed

    Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Laurila, Marko; Lægsgaard, Jesper; Alkeskjold, Thomas Tanggaard

    2012-03-26

    High-power fiber amplifiers for pulsed applications require large mode area (LMA) fibers having high pump absorption and near diffraction limited output. Photonic crystal fibers allow realization of short LMA fiber amplifiers having high pump absorption through a pump cladding that is decoupled from the outer fiber diameter. However, achieving ultra low NA for single mode (SM) guidance is challenging, thus different design strategies must be applied. The distributed modal filtering (DMF) design enables SM guidance in ultra low NA fibers with very large cores, where large preform tolerances can be compensated during the fiber draw. Design optimization of the SM bandwidth of the DMF rod fiber is presented. Analysis of band gap properties results in a fourfold increase of the SM bandwidth compared to previous results, achieved by utilizing the first band of cladding modes, which can cover a large fraction of the Yb emission band including wavelengths of 1030 nm and 1064 nm. Design parameters tolerating refractive index fabrication uncertainties of ± 10⁻⁴ are targeted to yield stable SM bandwidths.

  4. Vibrational modes and thermal transformation of purified single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kim, Un Jeong

    Vibrational modes of single-walled carbon nanotubes (SWNTs) and graphitic nanoribbons (GNRs) were studied using Raman scattering and/or Fourier Transform Infrared Spectroscopies, Variations in a three-step purification scheme to remove amorphous carbon and residual catalyst were studied: (step 1) Oxidation, (step 2) Acid Reflux, and (step 3) Thermal Annealing were found to remove most amorphous carbon (oxidation step) and residual metal catalyst (acid reflux step) which were the major impurity phases. By combining IR and Raman, we found considerable wall damage and functional groups (e.g.-COOH and-OH) could be introduced via H2O2 and HNO3 reflux. Surprisingly, vacuum annealing at ˜1100°C for a few hours was found to remove most wall damage and functional groups. Methods to break up large (purified) bundles of single-walled carbon nanotubes (SWNTs) to individual tubes were also investigated. Amide solvents with ultrasound were found to be very effective in debundling; initial purification treatment strongly impacted the outcome. SWNT material decorated with functional groups (e.g., -COOH) tended to produce higher yields of single tubes. Length and diameter distributions of individual tubes were measured using Atomic Force Microscopy. Aggressive chemical debundling processes were found to lead to more functionalization, higher degree of debundling and shorter tubes. The IR-active modes of SWNTs was observed for the first time by transmission method, some ten years after the discovery of the Raman-active modes. In concert with theoretical calculations, we were able to assign much of the sharp structure in the IR with anticipated one- and two-phonon lattice mode bands. Thermal evolution of bundled SWNT materials produced in the electric arc (ARC) and by CVD in CO gas (HiPCO) was also investigated. Although both ARC and HiPCO evolved thermally to multi-walled tubes (MWNTs), we found using electron microscopy that for T>2000°C ARC SWNTs (with significantly narrower

  5. High Energy, Single-Mode, All-Solid-State and Tunable UV Laser Transmitter

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Singh, Upendra N.; Hovis, FLoyd

    2007-01-01

    A high energy, single mode, all solid-state Nd:YAG laser primarily for pumping an UV converter is developed. Greater than 1 J/pulse at 50 HZ PRF and pulse widths around 22 ns have been demonstrated. Higher energy, greater efficiency may be possible. Refinements are known and practical to implement. Technology Demonstration of a highly efficient, high-pulse-energy, single mode UV wavelength generation using flash lamp pumped laser has been achieved. Greater than 90% pump depletion is observed. 190 mJ extra-cavity SFG; IR to UV efficiency > 21% (> 27% for 1 mJ seed). 160 mJ intra-cavity SFG; IR to UV efficiency up to 24% Fluence < 1 J/sq cm for most beams. The pump beam quality of the Nd:YAG pump laser is being refined to match or exceed the above UV converter results. Currently the Nd:YAG pump laser development is a technology demonstration. System can be engineered for compact packaging.

  6. Power-scalable system of phase-locked single-mode diode lasers.

    PubMed

    Bartelt-Berger, L; Brauch, U; Giesen, A; Huegel, H; Opower, H

    1999-09-20

    The direct use of diode lasers for high-power applications in material processing is limited to applications with relatively low beam quality and power density requirements. To achieve high beam quality one must use single-mode diode lasers, however with the drawback of relatively low optical output powers from these components. To realize a high-power system while conserving the high beam quality of the individual emitters requires coherent coupling of the emitters. Such a power-scalable system consisting of 19 slave lasers that are injection locked by one master laser has been built and investigated, with low-power diode lasers used for system demonstration. The optical power of the 19 injection-locked lasers is coupled into polarization-maintaining single-mode fibers and geometrically superimposed by a lens array and a focusing lens. The phase of each emitter is controlled by a simple electronic phase-control loop. The coherence of each slave laser is stabilized by computer control of the laser current and guarantees a stable degree of coherence of the whole system of 0.7. An enhancement factor of 13.2 in peak power density compared with that which was achievable with the incoherent superposition of the diode lasers was observed.

  7. Experimental verification of a model describing the intensity distribution from a single mode optical fiber

    SciTech Connect

    Moro, Erik A; Puckett, Anthony D; Todd, Michael D

    2011-01-24

    The intensity distribution of a transmission from a single mode optical fiber is often approximated using a Gaussian-shaped curve. While this approximation is useful for some applications such as fiber alignment, it does not accurately describe transmission behavior off the axis of propagation. In this paper, another model is presented, which describes the intensity distribution of the transmission from a single mode optical fiber. A simple experimental setup is used to verify the model's accuracy, and agreement between model and experiment is established both on and off the axis of propagation. Displacement sensor designs based on the extrinsic optical lever architecture are presented. The behavior of the transmission off the axis of propagation dictates the performance of sensor architectures where large lateral offsets (25-1500 {micro}m) exist between transmitting and receiving fibers. The practical implications of modeling accuracy over this lateral offset region are discussed as they relate to the development of high-performance intensity modulated optical displacement sensors. In particular, the sensitivity, linearity, resolution, and displacement range of a sensor are functions of the relative positioning of the sensor's transmitting and receiving fibers. Sensor architectures with high combinations of sensitivity and displacement range are discussed. It is concluded that the utility of the accurate model is in its predicative capability and that this research could lead to an improved methodology for high-performance sensor design.

  8. Lithographic VCSEL array multimode and single mode sources for sensing and 3D imaging

    NASA Astrophysics Data System (ADS)

    Leshin, J.; Li, M.; Beadsworth, J.; Yang, X.; Zhang, Y.; Tucker, F.; Eifert, L.; Deppe, D. G.

    2016-05-01

    Sensing applications along with free space data links can benefit from advanced laser sources that produce novel radiation patterns and tight spectral control for optical filtering. Vertical-cavity surface-emitting lasers (VCSELs) are being developed for these applications. While oxide VCSELs are being produced by most companies, a new type of oxide-free VCSEL is demonstrating many advantages in beam pattern, spectral control, and reliability. These lithographic VCSELs offer increased power density from a given aperture size, and enable dense integration of high efficiency and single mode elements that improve beam pattern. In this paper we present results for lithographic VCSELs and describes integration into military systems for very low cost pulsed applications, as well as continuouswave applications in novel sensing applications. The VCSELs are being developed for U.S. Army for soldier weapon engagement simulation training to improve beam pattern and spectral control. Wavelengths in the 904 nm to 990 nm ranges are being developed with the spectral control designed to eliminate unwanted water absorption bands from the data links. Multiple beams and radiation patterns based on highly compact packages are being investigated for improved target sensing and transmission fidelity in free space data links. These novel features based on the new VCSEL sources are also expected to find applications in 3-D imaging, proximity sensing and motion control, as well as single mode sensors such as atomic clocks and high speed data transmission.

  9. 2.1 kW single mode continuous wave monolithic fiber laser

    NASA Astrophysics Data System (ADS)

    Rosales-Garcia, Andrea; Tobioka, Hideaki; Abedin, Kazi; Dong, Hao; Várallyay, Zoltán.; Szabó, Áron; Taunay, Thierry; Sullivan, Sean; Headley, Clifford

    2015-03-01

    A robust, alignment-free monolithic 2.1 kW single-mode continuous wave fiber laser, operating at 1083 nm is demonstrated. The laser is pumped with commercial fiber pigtailed multimode diodes through all-fiber pump-signal power combiners in a MOPA architecture. The oscillator was formed with high reflector and output coupler fiber Bragg gratings written in 11/200 μm (mode field/cladding diameter) single-mode fiber. The gain medium was a 19m OFS commercial 11/200 μm double clad Yb-doped fiber (DCY). Pump light was coupled to the oscillator using two 11/200 μm pump-signal power combiners (PSC). A total of 20 commercially available 58W pump diodes at 915 nm were used to generate 800W of signal, as measured before the amplifier. The Raman power after the oscillator was more than 60 dB below the signal power. The amplifier was built using 13 m of 14/200 µm DCY and two (18+1)x1 PSC combiners with more than 95% pump and signal light transmission. A total of 2 kW of power was used to bi-directionally pump the amplifier. The output was measured after 3 m 14/200 μm fiber, and 10 m 100/360 μm delivery cable. Total signal output power was 2.1 kW, corresponding to an amplifier slope efficiency of 77%. The Raman power is more than 30 dB below the signal power. At maximum power, no modal instabilities, thermal effects, nor power rollover were observed. With higher power pumps, it is predicted that a power level of 2.6 kW can be achieved with the Raman level below 20 dB.

  10. Anisotropy, phonon modes, and free charge carrier parameters in monoclinic β -gallium oxide single crystals

    NASA Astrophysics Data System (ADS)

    Schubert, M.; Korlacki, R.; Knight, S.; Hofmann, T.; Schöche, S.; Darakchieva, V.; Janzén, E.; Monemar, B.; Gogova, D.; Thieu, Q.-T.; Togashi, R.; Murakami, H.; Kumagai, Y.; Goto, K.; Kuramata, A.; Yamakoshi, S.; Higashiwaki, M.

    2016-03-01

    We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared and far-infrared active modes. We apply our model approach to monoclinic β -Ga2O3 single-crystal samples. Surfaces cut under different angles from a bulk crystal, (010) and (2 ¯01 ), are investigated by generalized spectroscopic ellipsometry within infrared and far-infrared spectral regions. We determine the frequency dependence of 4 independent β -Ga2O3 Cartesian dielectric function tensor elements by matching large sets of experimental data using a point-by-point data inversion approach. From matching our monoclinic model to the obtained 4 dielectric function tensor components, we determine all infrared and far-infrared active transverse optic phonon modes with Au and Bu symmetry, and their eigenvectors within the monoclinic lattice. We find excellent agreement between our model results and results of density functional theory calculations. We derive and discuss the frequencies of longitudinal optical phonons in β -Ga2O3 . We derive and report density and anisotropic mobility parameters of the free charge carriers within the tin-doped crystals. We discuss the occurrence of longitudinal phonon plasmon coupled modes in β -Ga2O3 and provide their frequencies and eigenvectors. We also discuss and present monoclinic dielectric constants for static electric fields and frequencies above the reststrahlen range, and we provide a generalization of the Lyddane-Sachs-Teller relation for monoclinic lattices with infrared and far-infrared active modes. We find that the generalized Lyddane-Sachs-Teller relation is fulfilled excellently for β -Ga2O3 .

  11. Tunable S-band erbium-doped triple-ring laser with single-longitudinal-mode operation.

    PubMed

    Yeh, C-H; Huang, T T; Chien, H-C; Ko, C-H; Chi, S

    2007-01-22

    We propose and demonstrate a tunable and stable single-longitudinal-mode (SLM) erbium fiber laser with a passive triple-ring cavity structure in S-band operation. The proposed laser is fundamentally structured by using three different lengths of ring cavities, which serve as the mode filters. When a mode-restricting intracavity fiber Fabry-Perot tunable filter (FFP-TF) is combined, the proposed resonator can guarantee a tunable and stable SLM laser oscillation. Moreover, the performances of the output power, wavelength stability, tuning range, and side-mode suppression ratio (SMSR) are studied.

  12. Synthesis of the Einstein-Podolsky-Rosen entanglement in a sequence of two single-mode squeezers.

    PubMed

    Fedorov, Ilya A; Ulanov, Alexander E; Kurochkin, Yury V; Lvovsky, A I

    2017-01-01

    We propose and implement a new scheme of generating the optical Einstein-Podolsky-Rosen entangled state. Parametric down-conversion in two nonlinear crystals, positioned back-to-back in the waist of a pump beam, produces single-mode squeezed vacuum states in orthogonal polarization modes; a subsequent beam splitting entangles them and generates the Einstein-Podolsky-Rosen state. The technique takes advantage of the strong nonlinearity associated with type-0 phase-matching configuration while, at the same time, eliminating the need for actively stabilizing the optical phase between the two single-mode squeezers. We demonstrate our method, preparing a 1.4 dB two-mode squeezed state and characterizing it via two-mode homodyne tomography.

  13. Improved performance of tunable single-mode laser array based on high-order slotted surface grating.

    PubMed

    Abdullaev, Azat; Lu, Qiaoyin; Guo, Weihua; Wallace, Michael J; Nawrocka, Marta; Bello, Frank; Benson, Aaron; O'Callaghan, James; Donegan, John F

    2015-05-04

    We present an improved design of a wavelength-tunable single-mode laser array based on a high order surface grating with non-uniformly spaced slots. The laser array consists of 12 slotted single-mode lasers. The fabricated device exhibits a quasi-continuous tuning range of more than 36 nm over the temperature range from 10°C - 45°C covering the full C-band. All lasers in the array have stable single-mode operation with side mode suppression ratio of 50 dB due to the modified slot design. A spectral linewidth of less than 500 kHz was obtained for all channels in the array.

  14. Pseudo-single-bunch with adjustable frequency: a new operation mode for synchrotron light sources.

    PubMed

    Sun, C; Portmann, G; Hertlein, M; Kirz, J; Robin, D S

    2012-12-28

    We present the concept and results of pseudo-single-bunch (PSB) operation--a new operational mode at the advanced light source--that can greatly expand the capabilities of synchrotron light sources to carry out dynamics and time-of-flight experiments. In PSB operation, a single electron bunch is displaced transversely from the other electron bunches using a short-pulse, high-repetition-rate kicker magnet. Experiments that require light emitted only from a single bunch can stop the light emitted from the other bunches using a collimator. Other beam lines will only see a small reduction in flux due to the displaced bunch. As a result, PSB eliminates the need to schedule multibunch and timing experiments during different running periods. Furthermore, the time spacing of PSB pulses can be adjusted from milliseconds to microseconds with a novel "kick-and-cancel" scheme, which can significantly alleviate complications of using high-power choppers and substantially reduce the rate of sample damage.

  15. Pseudo-Single-Bunch with Adjustable Frequency: A New Operation Mode for Synchrotron Light Sources

    NASA Astrophysics Data System (ADS)

    Sun, C.; Portmann, G.; Hertlein, M.; Kirz, J.; Robin, D. S.

    2012-12-01

    We present the concept and results of pseudo-single-bunch (PSB) operation—a new operational mode at the advanced light source—that can greatly expand the capabilities of synchrotron light sources to carry out dynamics and time-of-flight experiments. In PSB operation, a single electron bunch is displaced transversely from the other electron bunches using a short-pulse, high-repetition-rate kicker magnet. Experiments that require light emitted only from a single bunch can stop the light emitted from the other bunches using a collimator. Other beam lines will only see a small reduction in flux due to the displaced bunch. As a result, PSB eliminates the need to schedule multibunch and timing experiments during different running periods. Furthermore, the time spacing of PSB pulses can be adjusted from milliseconds to microseconds with a novel “kick-and-cancel” scheme, which can significantly alleviate complications of using high-power choppers and substantially reduce the rate of sample damage.

  16. Plasmonic crystal cavity on single-mode optical fiber end facet for label-free biosensing

    NASA Astrophysics Data System (ADS)

    He, Xiaolong; Yi, Hui; Long, Jing; Zhou, Xin; Yang, Jie; Yang, Tian

    2016-06-01

    Surface plasmon resonance (SPR) devices on single-mode optical fiber (SMF) end facets are desired for label-free biosensing, due to flexible light delivery, in vivo inspection capability, and seamless integration with fiber-optic communication techniques. We report a plasmonic crystal cavity structure that has a steep resonance near the plasmonic bandedge, a fabrication process to efficiently transfer and align the structure onto a bare SMF end facet, and characterization of its sensing performance. With a sensitivity of 571 nm RIU-1, a figure of merit of 68 RIU-1 and a real-time refractive index detection limit of 3.5 × 10-6 RIU, our sensors can be readily applied in common SPR biosensing experiments. They are over an order of magnitude more sensitive than reported modified-end multimode fiber SPR devices, while there are no reports on previous SMF end facet devices' detection limits which have very low figures of merit.

  17. Versatile chromatic dispersion measurement of a single mode fiber using spectral white light interferometry.

    PubMed

    Lee, Ji Yong; Kim, Dug Young

    2006-11-27

    We present a versatile and accurate chromatic dispersion measurement method for single mode optical fibers over a wide spectral range (200 nm) using a spectral domain white light interferometer. This technique is based on spectral interferometry with a Mach-Zehnder interferometer setup and a broad band light source. It takes less than a second to obtain a spectral interferogram for a few tens of centimeter length fiber sample. We have demonstrated that the relative group velocity, the chromatic dispersion and the dispersion slope of a sample fiber can be obtained very accurately regardless of the zero-dispersion wavelength (ZDW) of a sample after frequency dependent optical phase was directly retrieved from a spectral interferogram. The measured results with our proposed method were compared with those obtained with a conventional time-domain dispersion measurement method. A good agreement between those results indicates that our proposed method can measure the chromatic dispersion of a short length optical fiber with very high accuracy.

  18. Signal-to-noise ratio of Geiger-mode avalanche photodiode single-photon counting detectors

    NASA Astrophysics Data System (ADS)

    Kolb, Kimberly

    2014-08-01

    Geiger-mode avalanche photodiodes (GM-APDs) use the avalanche mechanism of semiconductors to amplify signals in individual pixels. With proper thresholding, a pixel will be either "on" (avalanching) or "off." This discrete detection scheme eliminates read noise, which makes these devices capable of counting single photons. Using these detectors for imaging applications requires a well-developed and comprehensive expression for the expected signal-to-noise ratio (SNR). This paper derives the expected SNR of a GM-APD detector in gated operation based on gate length, number of samples, signal flux, dark count rate, photon detection efficiency, and afterpulsing probability. To verify the theoretical results, carrier-level Monte Carlo simulation results are compared to the derived equations and found to be in good agreement.

  19. Experimental study into single-longitudinal-mode Tm,Ho:YVO4 lasers

    NASA Astrophysics Data System (ADS)

    Dai, Tong-Yu; Han, Liu; Yao, Bao-Quan; Ju, You-Lun; Yu, Kuai-Kuai; Wang, Yue-Zhu

    2015-11-01

    The single-longitudinal-mode (SLM) Tm,Ho:YVO4 lasers were achieved by microchip configuration and double Fabry-Perot structure at room temperature. In the case of the microchip configuration laser, the maximum SLM power up to 17 mW was obtained on 2052.4 nm at 15 °C. In order to improve the output power of the SLM laser, it was implemented that the configuration of double Fabry-Perot etalons was used into the study of Tm,Ho:YVO4 lasers. Utilizing such configuration, the laser generated up to 95 mW output power in SLM at the wavelength of 2051.3 nm. With the angle of the Fabry-Perot etalons varied, the wavelength of the SLM laser could be turned from 2050.4 nm to 2051.3 nm, corresponding to a turning frequency of -64 GHz.

  20. Linear conjugate phase-locking of independent single-mode emitters

    SciTech Connect

    Gryaznov, N A; Kiselev, V M

    2000-05-31

    The problems of the construction of laser systems based on the methods of linear adaptive optics and designed for energy transport over large distances in outer space are analysed. New approaches are proposed to the organisation of the linear phase conjugation of output and beacon-signal radiations. For definite ratios of the beacon-signal ({omega}{sub b}), heterodyne ({omega}{sub h}), and power ({omega}{sub p}) radiations ({omega}{sub b} > {omega}{sub h} > {omega}{sub p} or {omega}{sub b} < {omega}{sub h} < {omega}{sub p}), the phase conjugation loop may play simultaneously the role of a precision frequency matching loop. This feature permits the phase locking of independent single-mode laser emitters, including phase locking in the far-field zone, to achieve the modular principle of system design and to generate the wavefront of radiation with a large cross section. (control of laser radiation parameters)

  1. 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.

  2. Note: Improving distributed strain sensing sensitivity in OFDR by reduced-cladding single mode fiber

    NASA Astrophysics Data System (ADS)

    Ding, Zhenyang; Yang, Di; Du, Yang; Zhou, Yonghan; Xu, Zhexi; Liu, Kun; Jiang, Junfeng; Liu, Tiegen

    2016-12-01

    We present a method to improve distributed strain sensing sensitivity by a reduced-cladding single mode fiber (RC SMF) using a Rayleigh backscattering spectra shift in optical frequency domain reflectometry. Comparing with a standard SMF with 250 μm diameter, a commercial low attenuation RC SMF with 165 μm diameter is shown to enhance the strain sensing sensitivity by about four-fold. Using this property, the system using the RC SMF can achieve smaller minimal measurable strain (MMS) in the same sensing spatial resolution (SSR) or smaller SSR in the same MMS than using the standard SMF. In our experiment, the system using RC SMF can achieve the MMS of 15 μstrain with a SSR of 4.5 cm or the MMS of 3 μstrain with a SSR of 18 cm.

  3. Investigation of single-mode fiber output damage by 405nm CW laser light

    NASA Astrophysics Data System (ADS)

    Gonschior, C. P.; Landrock-Bill, E.; Klein, K.-F.; Sun, T.; Grattan, K. T. V.

    2013-11-01

    In the past, the degradation of 405 nm fiber-coupled diode laser systems was investigated in detail with focus on the input end. The coupling and transmission loss of the laser light was associated to the growth of a periodic structure on the input surface. To reduce this damage, a short launch-fiber with a good surface quality was used on the input end surface. Thereby the power transmission was stabilized for at least one month. However, damage structures appeared on the output surface of the single-mode fiber. To investigate this effect, damaged samples were taken after different periods of time and examined with a scanning electron microscope (SEM). Bulges with a submicron periodic structure were found in the core region, too. Additionally, measurements of spectral loss were performed, showing the formation of color centers in the deep UV along the length of the fiber.

  4. Phase transformation as the single-mode mechanical deformation of silicon

    SciTech Connect

    Wong, S. Williams, J. S.; Bradby, J. E.; Haberl, B.

    2015-06-22

    The metastable body-centered cubic (bc8) and rhombohedral (r8) phases of silicon that are formed after the nanoindentation of diamond cubic silicon exhibit properties that are of both scientific and technological interest. This letter demonstrates that large regions of these phases can be readily formed from crystalline silicon via nanoindentation with minimal damage to the surrounding crystal. Cross-sectional transmission electron microscopy is used to show that volumes of these phases 6 μm wide and up to 650 nm deep can be generated using a symmetrical spherical tip of ∼21.5 μm diameter. This result indicates that the use of large symmetrical spherical tips result in highly hydrostatic conditions that can favor the single phase transformation mode without extensive damage to the surrounding crystalline regions that are observed in previous studies.

  5. Applications of a single-longitudinal-mode alexandrite laser for diagnostics of parameters of combustion interest

    NASA Astrophysics Data System (ADS)

    Li, Z. S.; Afzelius, M.; Zetterberg, J.; Aldén, M.

    2004-10-01

    We report on the applications of a single-longitudinal-mode (SLM) pulsed alexandrite laser system for diagnostics of parameters of flow/combustion interest. The laser system is characterized by its narrow linewidth, high peak power, and broad tunablity. The absolute frequency of the laser output was monitored by a wavelength diagnostic system, which included a high-resolution confocal etalon and a molecular iodine laser-induced fluorescence (LIF) detection system. Different nonlinear frequency conversion schemes were used to cover a large frequency range from the infrared to the deep UV. The versatility of the laser system for flow/combustion diagnostics is demonstrated in three applications, namely filtered Rayleigh scattering, high-resolution Doppler-free two-photon LIF of CO, and infrared LIF and polarization spectroscopy of CO2. The potential impacts of using this SLM laser system in laser flow/combustion diagnostic applications are discussed.

  6. Microwave processing and diagnosis of chemically reacting materials in a single-mode cavity applicator

    NASA Astrophysics Data System (ADS)

    Jow, Jinder; Hawley, Martin C.; Finzel, Mark; Asmussen, Jes, Jr.; Lin, Haw-Hwa

    1987-12-01

    Online microwave processing and dielectric diagnosis of chemically reacting materials (epoxy/amine) have been successfully performed using a TM012-mode cylindrical cavity at a frequency of 2.45 GHz in conjunction with fluoroptic temperature measurement. Complex permittivity measurements by this single-frequency technique are repeatable and consistent with those obtained by conventional swept-frequency methods. The accuracy of complex permittivity measurements for both methods is within + or - 5 percent for permittivity and + or - 15 percent for loss. Both techniques are based on material-cavity perturbation theory. Perturbation equations for cylindrical shapes of the cavity and loaded material were derived to account for volume variation of the sample due to thermal expansion. Complex permittivity of epoxy/amine as a function of the extent of cure and temperature was determined in order to monitor the chemical reaction progress during microwave processing.

  7. Comparison of higher order modes damping techniques for 800 MHz single cell superconducting cavities

    NASA Astrophysics Data System (ADS)

    Shashkov, Ya. V.; Sobenin, N. P.; Petrushina, I. I.; Zobov, M. M.

    2014-12-01

    At present, applications of 800 MHz harmonic cavities in both bunch lengthening and shortening regimes are under consideration and discussion in the framework of the High Luminosity LHC project. In this paper we study electromagnetic characteristics of high order modes (HOMs) for a single cell 800 MHz superconducting cavity and arrays of such cavities connected by drifts tubes. Different techniques for the HOMs damping such as beam pipe grooves, coaxial-notch loads, fluted beam pipes etc. are investigated and compared. The influence of the sizes and geometry of the drift tubes on the HOMs damping is analyzed. The problems of a multipacting discharge in the considered structures are discussed and the operating frequency detuning due to the Lorentz force is evaluated.

  8. Frequency Noise Suppression of a Single Mode Laser with an Unbalanced Fiber Interferometer for Subnanometer Interferometry

    PubMed Central

    Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Číp, Ondřej

    2015-01-01

    We present a method of noise suppression of laser diodes by an unbalanced Michelson fiber interferometer. The unstabilized laser source is represented by compact planar waveguide external cavity laser module, ORIONTM (Redfern Integrated Optics, Inc.), working at 1540.57 nm with a 1.5-kHz linewidth. We built up the unbalanced Michelson interferometer with a 2.09 km-long arm based on the standard telecommunication single-mode fiber (SMF-28) spool to suppress the frequency noise by the servo-loop control by 20 dB to 40 dB within the Fourier frequency range, remaining the tuning range of the laser frequency. PMID:25587980

  9. An integrated photoluminescence sensing platform using a single-multi-mode fiber coupler-based probe.

    PubMed

    Long, Feng; Zhu, Anna; Shi, Hanchang

    2014-03-21

    We demonstrate an integrated fiber optic photoluminescence sensing platform using a novel single-multi-mode fiber coupler (SMFC)-based probe with high collection efficiency for fluorescence signals. The SMFC, prepared using fused biconical taper technology, not only transmits excitation light, but also collects and transmits fluorescence. The entire system does not use complex optical components and rarely requires optical alignment. The simple structure of the SMFC considerably improves the light transmission efficiency, signal-to-noise ratio, and sensitivity of the system. Theoretical and experimental results show that the proposed probe increases the collection efficiency by more than eight-fold compared with a bifurcated fiber probe. The performance of the proposed probe was experimentally evaluated by measuring the fluorescence spectra of well-known targets and a fresh Tall Fescue leaf.

  10. Note: Improving distributed strain sensing sensitivity in OFDR by reduced-cladding single mode fiber.

    PubMed

    Ding, Zhenyang; Yang, Di; Du, Yang; Zhou, Yonghan; Xu, Zhexi; Liu, Kun; Jiang, Junfeng; Liu, Tiegen

    2016-12-01

    We present a method to improve distributed strain sensing sensitivity by a reduced-cladding single mode fiber (RC SMF) using a Rayleigh backscattering spectra shift in optical frequency domain reflectometry. Comparing with a standard SMF with 250 μm diameter, a commercial low attenuation RC SMF with 165 μm diameter is shown to enhance the strain sensing sensitivity by about four-fold. Using this property, the system using the RC SMF can achieve smaller minimal measurable strain (MMS) in the same sensing spatial resolution (SSR) or smaller SSR in the same MMS than using the standard SMF. In our experiment, the system using RC SMF can achieve the MMS of 15 μstrain with a SSR of 4.5 cm or the MMS of 3 μstrain with a SSR of 18 cm.

  11. Knudsen-number dependence of two-dimensional single-mode Rayleigh-Taylor fluid instabilities.

    PubMed

    Sagert, Irina; Howell, Jim; Staber, Alec; Strother, Terrance; Colbry, Dirk; Bauer, Wolfgang

    2015-07-01

    We present a study of single-mode Rayleigh-Taylor instabilities with a modified direct simulation Monte Carlo (MDSMC) code in two dimensions. The MDSMC code is aimed to capture the dynamics of matter for a large range of Knudsen numbers within one approach. Our method combines the traditional Monte Carlo technique to efficiently propagate particles and the point-of-closest-approach method for high spatial resolution. Simulations are performed using different particle mean free paths and we compare the results to linear theory predictions for the growth rate including diffusion and viscosity. We find good agreement between theoretical predictions and simulations and, at late times, observe the development of secondary instabilities, similar to hydrodynamic simulations and experiments. Large mean free paths favor particle diffusion, reduce the occurrence of secondary instabilities, and approach the noninteracting gas limit.

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

    SciTech Connect

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

    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 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.

  13. Superlinear growth of Rayleigh scattering-induced intensity noise in single-mode fibers.

    PubMed

    Cahill, James P; Okusaga, Olukayode; Zhou, Weimin; Menyuk, Curtis R; Carter, Gary M

    2015-03-09

    Rayleigh scattering generates intensity noise close to an optical carrier that propagates in a single-mode optical fiber. This noise degrades the performance of optoelectronic oscillators and RF-photonic links. When using a broad linewidth laser, we previously found that the intensity noise power scales linearly with optical power and fiber length, which is consistent with guided entropy mode Rayleigh scattering (GEMRS), a third order nonlinear scattering process, in the spontaneous limit. In this work, we show that this behavior changes significantly with the use of a narrow linewidth laser. Using a narrow linewidth laser, we measured the bandwidth of the intensity noise plateau to be 10 kHz. We found that the scattered noise power scales superlinearly with fiber length up to lengths of 10 km in the frequency range of 500 Hz to 10 kHz, while it scales linearly in the frequency range of 10 Hz to 100 Hz. These results suggest that the Rayleigh-scattering-induced intensity noise cannot be explained by third-order nonlinear scattering in the spontaneous limit, as previously hypothesized.

  14. 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.

  15. Pigtailed single-mode diode lasers. Final report, 20 September 1988-30 April 1989

    SciTech Connect

    Kwong, N.

    1989-04-30

    In choosing a scheme for single-mode fiber coupling, the final evaluation should of course be based on an experimental comparison between the alternative. However, such an evaluation will generally not reveal the essential limitations of any scheme. While the possible sources of less-than-ideal performance are well known, their relative significance is not so obvious. It is clear that in order to make significant improvements in the state of fiber-coupling technology, the relevant limitations must be clarified in order to guide further efforts in fruitful directions. As such, we have conducted an analysis of several aspects of the fiber-coupling problem which is presented here. Preliminary to the consideration of any particular system, the importance of the zeroth- and first-order properties of the coupling system are briefly discussed. To go beyond this, the higher-order aberrations of the optical coupling system must be included in the analysis. To do this, an algorithm to calculate the mode coupling performance of any optical system was developed using the ray-tracing features of an optical design program. This algorithm is described along with the results of an analysis of coupling with graded index lenses which have been found to work well experimentally.

  16. High efficiency single transverse mode photonic band crystal lasers with low vertical divergence

    NASA Astrophysics Data System (ADS)

    Zhao, Shaoyu; Qu, Hongwei; Liu, Yun; Li, Lunhua; Chen, Yang; Zhou, Xuyan; Lin, Yuzhe; Liu, Anjin; Qi, Aiyi; Zheng, Wanhua

    2016-10-01

    High efficiency 980 nm longitudinal photonic band crystal (PBC) edge emitting laser diodes are designed and fabricated. The calculated results show that eight periods of Al0.1Ga0.9As and Al0.25Ga0.75As layer pairs can reduce the vertical far field divergence to 10.6° full width at half maximum (FWHM). The broad area (BA) lasers show a very high internal quantum efficiency ηi of 98% and low internal loss αi of 1.92 cm-1. Ridge waveguide (RW) lasers with 3 mm cavity length and 5um strip width provide 430 mW stable single transverse mode output at 500 mA injection current with power conversion efficiency (PCE) of 47% under continuous wave (CW) mode. A maximum PCE of 50% is obtained at the 300 mA injection current. A very low vertical far field divergence of 9.4° is obtained at 100 mA injection. At 500 mA injection, the vertical far field divergence increases to 11°, the beam quality factors M2 values are 1.707 in vertical direction and 1.769 in lateral direction.

  17. A double-mode piezoelectric single-crystal ultrasonic micro-actuator.

    PubMed

    Guo, Mingsen; Dong, Shuxiang; Ren, Bo; Luo, Haosu

    2010-11-01

    Ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) single crystals with higher coercive field (E(C) ~9 kV/cm) and higher ferroelectric-transition temperature (T(R-T) = 108°C) were grown, and correspondingly, a double-mode piezoelectric ultrasonic micro-actuator made of PIN-PMN-PT crystal brick (5 x 1.5 x 1.32 mm) and operated in the first longitudinal and the second bending modes was developed. The ferroelectric, dielectric, electromechanical, and resonance displacement properties of the micro-actuator were characterized for miniature linear piezo-motor applications. The longitudinal displacement of the actuator is ~0.11 μm (with an applied voltage of 5 V), which is comparable to that of a multilayer piezoelectric-ceramic actuator of the same size. This crystal micro-actuator was successfully used to drive a slider moving linearly.

  18. Von Neumann entropy and phase distribution of two mode parametric amplifier interacting with a single atom

    SciTech Connect

    Sebawe Abdalla, M. . E-mail: m.sebawe@physics.org; Obada, A.-S.F.; Abdel-Aty, M.

    2005-08-01

    In the present article, we introduce a Hamiltonian model that consists of two modes of the field in a perfect cavity to interact with a single two-level atom. The interaction between the fields has been taken into account and considered to be in the parametric amplifier form. The model in one hand can be regarded as a generalization of the Jaynes-Cummings model (JCM), however, in the other hand it can be considered as a generalization of the parametric amplifier model. Under a certain condition the exact solution to the Schroedinger equation is obtained. Employing this solution and for chosen values of different parameters we discuss numerically the atomic occupation probabilities as well as the degree of entanglement through the entropy of the field. The system shows superstructure phenomenon similar to that appeared from the effect of the Kerr-like medium on the Jaynes-Cummings model. The von Neumann entropy and phase distribution for both two-mode correlated and uncorrelated coherent states cases are also considered.

  19. Multiple Beam Correlation Using Single-Mode Fiber Optics with Application to Interferometric Imaging

    NASA Astrophysics Data System (ADS)

    Shaklan, Stuart Bruce

    A study of the application of single-mode fiber optics to the multiple-beam interferometric recombination problem is presented. In the laboratory, the fibers have been used in wide bandwidth, two-arm, Mach-Zehnder test interferometers as well as a 5-telescope imaging interferometer connected to an all-fiber beam combiner. Based upon these experiments and some theoretical studies it is shown that fiber optics and fiber optic components such as directional couplers provide an excellent alternative to conventional optics such as mirrors, beamsplitters, and relay lenses. The equations describing the measurement of the complex degree of coherence in an interferometer with a single-mode fiber in each arm are derived. The equations reveal an important feature of the fibers: they filter phase fluctuations due to aberrations and turbulence at the input and convert them to intensity fluctuations at the output. This leads to a simplification of the calibration of measured visibilities. The coupling efficiency of light which has passed through a turbulent atmosphere is also studied as a function of fiber parameters and turbulence conditions for both image motion stabilized and non-stabilized cases. For the former case, coupling efficiency remains greater than 50% as long as telescope diameter is no larger than the turbulence coherence length. Beam combination architectures using arrays of directional couplers are fully discussed. Arrays accommodating up to 20 input beams are presented. The arrays require only N detector pixels for N input beams. A scheme of temporal multiplexing of the phase of each beam is used to identify individual fringe pairs. One possible scheme allows wide bandwidths even for large numbers of beams. A 5-telescope interferometer has been constructed and connected to an all-fiber beam combiner. Two extended objects were observed and reconstructed using standard radio astronomy VLBI software. The interferometer and beam combiner had good thermal and

  20. High energy, single-polarized, single-transverse-mode, nanosecond pulses generated by a multi-stage Yb-doped photonic crystal fiber amplifier

    NASA Astrophysics Data System (ADS)

    Shen, Xinglai; Zhang, Haitao; Hao, He; Li, Dan; Li, Qinghua; Yan, Ping; Gong, Mali

    2015-06-01

    We report the construction of a cascaded fiber amplifier where a 40-μm-core-diameter photonic crystal fiber is utilized in the main amplifier stage. Single-transverse-mode, linearly-polarized, 7.5 ns pulses with 1.5 mJ energy, 123 kW peak power and 10 nm spectral bandwidth centered at 1062 nm are generated. To our knowledge, the pulse energy we obtain is the highest from 40-μm-core-diameter photonic crystal fibers, and also the highest for long pulses (>1 ns) with linear polarization and single transverse mode.

  1. Single-mode, All-Solid-State Nd:YAG Laser Pumped UV Converter

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Armstrong, Darrell, J.; Edwards, William C.; Singh, Upendra N.

    2008-01-01

    In this paper, the status of a high-energy, all solid-state Nd:YAG laser pumped nonlinear optics based UV converter development is discussed. The high-energy UV transmitter technology is being developed for ozone sensing applications from space based platforms using differential lidar technique. The goal is to generate greater than 200 mJ/pulse with 10-50 Hz PRF at wavelengths of 308 nm and 320 nm. A diode-pumped, all-solid-state and single longitudinal mode Nd:YAG laser designed to provide conductively cooled operation at 1064 nm has been built and tested. Currently, this pump laser provides an output pulse energy of >1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of <2. The single frequency UV converter arrangement basically consists of an IR Optical Parametric Oscillator (OPO) and a Sum Frequency Generator (SFG) setups that are pumped by 532 nm wavelength obtained via Second Harmonic Generation (SHG). In this paper, the operation of an inter cavity SFG with CW laser seeding scheme generating 320 nm wavelength is presented. Efforts are underway to improve conversion efficiency of this mJ class UV converter by modifying the spatial beam profile of the pump laser.

  2. Steady-state crack growth in single crystals under Mode I loading

    NASA Astrophysics Data System (ADS)

    Juul, K. J.; Nielsen, K. L.; Niordson, C. F.

    The active plastic zone that surrounds the tip of a sharp crack growing under plane strain Mode I loading conditions at a constant velocity in a single crystal is studied. Both the characteristics of the plastic zone and its effect on the macroscopic toughness is investigated in terms of crack tip shielding due to plasticity (quantified by employing the Suo, Shih, and Varias set-up). Three single crystals (FCC, BCC, HCP) are modelled in a steady-state elastic visco-plastic framework, with emphasis on the influence of rate-sensitivity and crystal structures. Distinct velocity discontinuities at the crack tip predicted by Rice [Rice J.R., 1987. Tensile crack tip fields in elastic-ideally plastic crystals. Mech. Mater. 6, pp. 317-335] for quasi-static crack growth are confirmed through the numerical simulations and highly refined details are revealed. Through a detailed study, it is demonstrated that the largest shielding effect develops in HCP crystals, while the lowest shielding exists for FCC crystals. Rate-sensitivity is found to affect the plastic zone size, but the characteristics overall remain similar for each individual crystal structure. An increasing rate-sensitivity at low crack velocities monotonically increases the crack tip shielding, whereas the opposite behaviour is observed at high velocities. This observation leads to the existence of a characteristic velocity at which the crack tip shielding becomes independent of the rate-sensitivity.

  3. Coupling single giant nanocrystal quantum dots to the fundamental mode of patch nanoantennas through fringe field

    DOE PAGES

    Wang, Feng; Karan, Niladri S.; Minh Nguyen, Hue; ...

    2015-09-23

    Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results andmore » further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. Finally, this provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap.« less

  4. Coupling single giant nanocrystal quantum dots to the fundamental mode of patch nanoantennas through fringe field

    SciTech Connect

    Wang, Feng; Karan, Niladri S.; Minh Nguyen, Hue; Ghosh, Yagnaseni; Hollingsworth, Jennifer A.; Htoon, Han

    2015-09-23

    Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results and further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. Finally, this provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap.

  5. Dual-mode optical microscope based on single-pixel imaging

    NASA Astrophysics Data System (ADS)

    Rodríguez, A. D.; Clemente, P.; Tajahuerce, E.; Lancis, J.

    2016-07-01

    We demonstrate an inverted microscope that can image specimens in both reflection and transmission modes simultaneously with a single light source. The microscope utilizes a digital micromirror device (DMD) for patterned illumination altogether with two single-pixel photosensors for efficient light detection. The system, a scan-less device with no moving parts, works by sequential projection of a set of binary intensity patterns onto the sample that are codified onto a modified commercial DMD. Data to be displayed are geometrically transformed before written into a memory cell to cancel optical artifacts coming from the diamond-like shaped structure of the micromirror array. The 24-bit color depth of the display is fully exploited to increase the frame rate by a factor of 24, which makes the technique practicable for real samples. Our commercial DMD-based LED-illumination is cost effective and can be easily coupled as an add-on module for already existing inverted microscopes. The reflection and transmission information provided by our dual microscope complement each other and can be useful for imaging non-uniform samples and to prevent self-shadowing effects.

  6. Performance of Single Electrode-Supported Cells Operating in the Electrolysis Mode

    SciTech Connect

    J. E. O'Brien; G. K. Housley; D. G. Milobar

    2009-11-01

    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 over a temperature range of 800 to 900ºC. 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. The experiments were performed over a range of steam inlet mole fractions (0.1 – 0.6), gas flow rates, and current densities (0 to 0.6 A/cm2). Steam consumption rates associated with electrolysis were measured directly using inlet and outlet dewpoint instrumentation. On a molar basis, the steam consumption rate is equal to the hydrogen production rate. Cell performance was evaluated by performing DC potential sweeps at 800, 850, and 900°C. The voltage-current characteristics are presented, along with values of area-specific resistance as a function of current density. Long-term cell performance is also assessed to evaluate cell degradation. Details of the custom single-cell test apparatus developed for these experiments are also presented.

  7. New method for path-length equalization of long single-mode fibers for interferometry

    NASA Astrophysics Data System (ADS)

    Anderson, M.; Monnier, J. D.; Ozdowy, K.; Woillez, J.; Perrin, G.

    2014-07-01

    The ability to use single mode (SM) fibers for beam transport in optical interferometry offers practical advantages over conventional long vacuum pipes. One challenge facing fiber transport is maintaining constant differential path length in an environment where environmental thermal variations can lead to cm-level variations from day to night. We have fabricated three composite cables of length 470 m, each containing 4 copper wires and 3 SM fibers that operate at the astronomical H band (1500-1800 nm). Multiple fibers allow us to test performance of a circular core fiber (SMF28), a panda-style polarization-maintaining (PM) fiber, and a lastly a specialty dispersion-compensated PM fiber. We will present experimental results using precision electrical resistance measurements of the of a composite cable beam transport system. We find that the application of 1200 W over a 470 m cable causes the optical path difference in air to change by 75 mm (+/- 2 mm) and the resistance to change from 5.36 to 5.50Ω. Additionally, we show control of the dispersion of 470 m of fiber in a single polarization using white light interference fringes (λc=1575 nm, Δλ=75 nm) using our method.

  8. A comparison of the updated very high resolution model RegCM3_10km with the previous version RegCM3_25km over the complex terrain of Greece: present and future projections

    NASA Astrophysics Data System (ADS)

    Tolika, Konstantia; Anagnostopoulou, Christina; Velikou, Kondylia; Vagenas, Christos

    2016-11-01

    The ability of a fine resolution regional climate model (10 × 10 km) in simulating efficiently the climate characteristics (temperature, precipitation, and wind) over Greece, in comparison to the previous version of the model with a 25 × 25 km resolution, is examined and analyzed in the present study. Overall, the results showed that the finer resolution model presented a better skill in generating low winter temperatures at high altitudinal areas, the temperature difference between the islands and the surrounding sea, high rainfall totals over the mountainous areas, the thermal storms during summer, and the wind maxima over the Aegean Sea. Regarding the future projections, even though the two models agree on the climatic signal, differences are found mainly to the magnitude of change of the selected parameters. Finally, it was found that at higher pressure levels, the present day projections of the two models do not show significant differences since the topography and terrain does not play such an important role as the general atmospheric circulation.

  9. Geiger-mode APD camera system for single-photon 3D LADAR imaging

    NASA Astrophysics Data System (ADS)

    Entwistle, Mark; Itzler, Mark A.; Chen, Jim; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir

    2012-06-01

    The unparalleled sensitivity of 3D LADAR imaging sensors based on single photon detection provides substantial benefits for imaging at long stand-off distances and minimizing laser pulse energy requirements. To obtain 3D LADAR images with single photon sensitivity, we have demonstrated focal plane arrays (FPAs) based on InGaAsP Geiger-mode avalanche photodiodes (GmAPDs) optimized for use at either 1.06 μm or 1.55 μm. These state-of-the-art FPAs exhibit excellent pixel-level performance and the capability for 100% pixel yield on a 32 x 32 format. To realize the full potential of these FPAs, we have recently developed an integrated camera system providing turnkey operation based on FPGA control. This system implementation enables the extremely high frame-rate capability of the GmAPD FPA, and frame rates in excess of 250 kHz (for 0.4 μs range gates) can be accommodated using an industry-standard CameraLink interface in full configuration. Real-time data streaming for continuous acquisition of 2 μs range gate point cloud data with 13-bit time-stamp resolution at 186 kHz frame rates has been established using multiple solid-state storage drives. Range gate durations spanning 4 ns to 10 μs provide broad operational flexibility. The camera also provides real-time signal processing in the form of multi-frame gray-scale contrast images and single-frame time-stamp histograms, and automated bias control has been implemented to maintain a constant photon detection efficiency in the presence of ambient temperature changes. A comprehensive graphical user interface has been developed to provide complete camera control using a simple serial command set, and this command set supports highly flexible end-user customization.

  10. Fluorescence measurement by a streak camera in a single-photon-counting mode.

    PubMed

    Komura, Masayuki; Itoh, Shigeru

    2009-01-01

    We describe here a recently developed fluorescence measurement system that uses a streak camera to detect fluorescence decay in a single photon-counting mode. This system allows for easy measurements of various samples and provides 2D images of fluorescence in the wavelength and time domains. The great advantage of the system is that the data can be handled with ease; furthermore, the data are amenable to detailed analysis. We describe the picosecond kinetics of fluorescence in spinach Photosystem (PS) II particles at 4-77 K as a typical experimental example. Through the global analysis of the data, we have identified a new fluorescence band (F689) in addition to the already established F680, F685, and F695 emission bands. The blue shift of the steady-state fluorescence spectrum upon cooling below 77 K can be interpreted as an increase of the shorter-wavelength fluorescence, especially F689, due to the slowdown of the excitation energy transfer process. The F685 and F695 bands seem to be thermally equilibrated at 77 K but not at 4 K. The simple and efficient photon accumulation feature of the system allows us to measure fluorescence from leaves, solutions, single colonies, and even single cells. The 2D fluorescence images obtained by this system are presented for isolated spinach PS II particles, intact leaves of Arabidopsis thaliana, the PS I super-complex of a marine centric diatom, Chaetoceros gracilis, isolated membranes of a purple photosynthetic bacterium, Acidiphilium rubrum, which contains Zn-BChl a, and a coral that contains a green fluorescent protein and an algal endosymbiont, Zooxanthella.

  11. Time-resolved particle image velocimetry measurements of the 3D single-mode Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    Xu, Qian; Krivets, Vitaliy V.; Sewell, Everest G.; Jacobs, Jeffrey W.

    2016-11-01

    A vertical shock tube is used to perform experiments on the single-mode three-dimensional Richtmyer-Meshkov Instability (RMI). The light gas (Air) and the heavy gas (SF6) enter from the top and the bottom of the shock tube driven section to form the interface. The initial perturbation is then generated by oscillating the gases vertically. Both gases are seeded with particles generated through vaporizing propylene glycol. An incident shock wave (M 1.2) impacts the interface to create an impulsive acceleration. The seeded particles are illuminated by a dual cavity 75W, Nd: YLF laser. Three high-speed CMOS cameras record time sequences of image pairs at a rate of 2 kHz. The initial perturbation used is that of a single, square-mode perturbation with either a single spike or a single bubble positioned at the center of the shock tube. The full time dependent velocity field is obtained allowing the determination of the circulation versus time. In addition, the evolution of time dependent amplitude is also determined. The results are compared with PIV measurements from previous two-dimensional single mode experiments along with PLIF measurements from previous three-dimensional single mode experiments.

  12. Buckling mode localization in a multi-span periodic structure with a disorder in a single span

    NASA Technical Reports Server (NTRS)

    Li, Y. W.; Elishakoff, Isaac; Starnes, J. H., Jr.

    1998-01-01

    This paper investigates the buckling mode localization in the periodic multi-span beam with disorder occurring in an arbitrary single span. The analytical finite difference calculus is used in conjunction with the conventional displacement method to derive the transcendental equations from which buckling load is calculated. The underlying treatment is general and the solution thus obtained is exact. Numerical results show that the buckling mode is highly localized in the vicinity of the disordered span of the beam.

  13. High-power single spatial mode AlGaAs channeled-substrate-planar semiconductor diode lasers for spaceborne communications

    NASA Technical Reports Server (NTRS)

    Connolly, J. C.; Carlin, D. B.; Ettenberg, M.

    1989-01-01

    A high power single spatial mode channeled substrate planar AlGaAs semiconductor diode laser was developed. The emission wavelength was optimized at 860 to 880 nm. The operating characteristics (power current, single spatial mode behavior, far field radiation patterns, and spectral behavior) and results of computer modeling studies on the performance of the laser are discussed. Reliability assessment at high output levels is included. Performance results on a new type of channeled substrate planar diode laser incorporating current blocking layers, grown by metalorganic chemical vapor deposition, to more effectively focus the operational current to the lasing region was demonstrated. The optoelectronic behavior and fabrication procedures for this new diode laser are discussed. The highlights include single spatial mode devices with up to 160 mW output at 8600 A, and quantum efficiencies of 70 percent (1 W/amp) with demonstrated operating lifetimes of 10,000 h at 50 mW.

  14. Toward single-mode random lasing within a submicrometre-sized spherical ZnO particle film

    NASA Astrophysics Data System (ADS)

    Niyuki, Ryo; Fujiwara, Hideki; Ishikawa, Yoshie; Koshizaki, Naoto; Tsuji, Takeshi; Sasaki, Keiji

    2016-03-01

    We had recently reported unique random laser action such as quasi-single-mode and low-threshold lasing from a submicrometre-sized spherical ZnO nanoparticle film with polymer particles as defects. The present study demonstrates a novel approach to realize single-mode random lasing by adjusting the sizes of the defect particles. From the dependence of random lasing properties on defect size, we find that the average number of lasing peaks can be modified by the defect size, while other lasing properties such as lasing wavelengths and thresholds remain unchanged. These results suggest that lasing wavelengths and thresholds are determined by the resonant properties of the surrounding scatterers, while the defect size stochastically determines the number of lasing peaks. Therefore, if we optimize the sizes of the defects and scatterers, we can intentionally induce single-mode lasing even in a random structure (Fujiwara et al 2013 Appl. Phys. Lett. 102 061110).

  15. 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.

  16. 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.

  17. Design, fabrication and characterisation of nano-imprinted single mode waveguide structures for intra-chip optical communications

    NASA Astrophysics Data System (ADS)

    Justice, John; Khan, Umar; Korhonen, Tia; Boersma, Arjen; Wiegersma, Sjoukje; Karppinen, Mikko; Corbett, Brian

    2015-03-01

    In the Information and Communications Technology (ICT) sector, the demands on bandwidth continually grow due to increased microprocessor performance and the need to access ever increasing amounts of stored data. The introduction of optical data transmission (e.g. glass fiber) to replace electronic transmission (e.g. copper wire) has alleviated the bandwidth issue for communications over distances greater than 10 meters, however, the need has arisen for optical data transfer over shorter distances such as those found inside computers. A possible solution for this is the use of low-cost single mode polymer based optical waveguides fabricated by direct patterning Nanoimprint Lithography (NIL). NIL has emerged as a scalable manufacturing technology capable of producing features down to the hundred nanometer scale with the potential for large scale (roll-to-roll) manufacturing. In this paper, we present results on the modeling, fabrication and characterization of single mode waveguides and optical components in low-loss ORMOCER™ materials. Single mode waveguides with a mode field diameter of 7 μm and passive structures such as bends, directional couplers and multi-mode interferometers (MMIs) suitable for use in 1550 nm optical interconnects were fabricated using wafer scale NIL processes. Process issues arising from the nano-imprint technique such as residual layers and angled sidewalls are modeled and investigated for excess loss and higher order mode excitation. Conclusions are drawn on the applicability of nano-imprinting to the fabrication of circuits for intrachip/ board-level optical interconnect.

  18. Electro-opto-mechanical radio-frequency oscillator driven by guided acoustic waves in standard single-mode fiber

    NASA Astrophysics Data System (ADS)

    London, Yosef; Diamandi, Hilel Hagai; Zadok, Avi

    2017-04-01

    An opto-electronic radio-frequency oscillator that is based on forward scattering by the guided acoustic modes of a standard single-mode optical fiber is proposed and demonstrated. An optical pump wave is used to stimulate narrowband, resonant guided acoustic modes, which introduce phase modulation to a co-propagating optical probe wave. The phase modulation is converted to an intensity signal at the output of a Sagnac interferometer loop. The intensity waveform is detected, amplified, and driven back to modulate the optical pump. Oscillations are achieved at a frequency of 319 MHz, which matches the resonance of the acoustic mode that provides the largest phase modulation of the probe wave. Oscillations at the frequencies of competing acoustic modes are suppressed by at least 40 dB. The linewidth of the acoustic resonance is sufficiently narrow to provide oscillations at a single longitudinal mode of the hybrid cavity. Competing longitudinal modes are suppressed by at least 38 dB as well. Unlike other opto-electronic oscillators, no radio-frequency filtering is required within the hybrid cavity. The frequency of oscillations is entirely determined by the fiber opto-mechanics.

  19. Hybrid integration technologies for a single-mode array transceiver, including the use of polymer waveguides of benzocyclobutene

    NASA Astrophysics Data System (ADS)

    Arvidsson, Gunnar; Backlin, Lennart; Olson, Magnus; Scholes, Andrew P.; Haglund, Joacim; Svensson, Magnus; Palmskog, Goran F.; Augustsson, Torsten; Eriksen, Paul; Granberg, Mats; Larsson, Jacob; Lundstrom, Pontus

    2003-03-01

    Access networks represent a bottle neck in the present communication networks. The introduction of optical single mode technology into the access networks (Fiber TO THE HOME, FTTH; Fiber To The Antenna, FTTA etc.), would be highly desirable. In order for this to occur a drastic reduction of the cost for key optoelectronic components such as transceivers is needed. We report on and discuss different key technologies crucial for the production of low cost optical single mode components. In particular a technology demonstrator in the form of an array transceiver module has been designed and fabricated, thereby demonstrating the process compatibility between a number of low-cost technologies.

  20. Coupling Single-Mode Fiber to Uniform and Symmetrically Tapered Thin-Film Waveguide Structures Using Gadolinium Gallium Garnet

    NASA Technical Reports Server (NTRS)

    Gadi, Jagannath; Yalamanchili, Raj; Shahid, Mohammad

    1995-01-01

    The need for high efficiency components has grown significantly due to the expanding role of fiber optic communications for various applications. Integrated optics is in a state of metamorphosis and there are many problems awaiting solutions. One of the main problems being the lack of a simple and efficient method of coupling single-mode fibers to thin-film devices for integrated optics. In this paper, optical coupling between a single-mode fiber and a uniform and tapered thin-film waveguide is theoretically modeled and analyzed. A novel tapered structure presented in this paper is shown to produce perfect match for power transfer.

  1. 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.

  2. Performance and future developments of the RHEA single-mode spectrograph

    NASA Astrophysics Data System (ADS)

    Bento, Joao; Feger, Tobias; Ireland, Michael J.; Rains, Adam; Jovanovic, Nemanja; Coutts, David W.; Schwab, Christian; Arriola, Alexander; Gross, Simon

    2016-08-01

    The Replicable High-resolution Exoplanet and Asteroseismology (RHEA) spectrograph is being developed to serve as a basis for multiple copies across a network of small robotic telescopes. The spectrograph operates at the diffraction-limit by using a single-mode fiber input, resulting in a compact and modal-noise-free unit. The optical design is mainly based on off-the-shelf available components and comprises a near-Littrow configuration with prism cross-disperser. The échelle format covers a wavelength range of 430-650 nm at R=75,000 resolving power. In this paper we briefly summarize the current status of the instrument and present preliminary results from the first on-sky demonstration of the prototype using a fully automated 16" telescope, where we observe stable and semi-variable stars up to V=3.5 magnitude. Future steps to enhance the efficiency and passive stability of RHEA are discussed in detail. For example, we show the concept of using a multi-fiber injection unit, akin to a photonic lantern, which not only enables increased throughput but also offers simultaneous wavelength calibration.

  3. Large-Area High Aspect Ratio Plasmonic Interference Lithography Utilizing a Single High-k Mode.

    PubMed

    Chen, Xi; Yang, Fan; Zhang, Cheng; Zhou, Jing; Guo, L Jay

    2016-04-26

    Plasmonic lithography, which utilizes subwavelength confinement of surface plasmon polartion (SPP) waves, has the capability of breaking the diffraction limit and delivering high resolution. However, all previously reported results suffer from critical issues, such as shallow pattern depth and pattern nonuniformity even over small exposure areas, which limit the application of the technology. In this work, periodic patterns with high aspect ratios and a half-pitch of about 1/6 of the wavelength were achieved with pattern uniformity in square centimeter areas. This was accomplished by designing a special mask and photoresist (PR) system to select a single high spatial frequency mode and incorporating the PR into a waveguide configuration to ensure uniform light exposure over the entire depth of the photoresist layer. In addition to the experimental progress toward large-scale applications of plasmonic interference lithography, the general criteria of designing such an exposure system is also discussed, which can be used for nanoscale fabrication in this fashion for various applications with different requirements for wavelength, pitch, aspect ratio, and structure.

  4. Design and evaluation of improved magnetic stir bars for single-mode microwave reactors.

    PubMed

    Obermayer, David; Damm, Markus; Kappe, C Oliver

    2013-08-14

    Magnetic stirring in sealed cylindrical vessels designed for use in single-mode microwave instruments is typically less than optimal, and is not comparable to the efficient agitation that can be generally obtained in a round-bottomed flask fitted with a suitable magnetic stir bar or using overhead mechanical stirring systems. A new "vertical blade" stir bar design that improves the stirring performance in the very narrow, flow-constricting microwave vessels has been developed and evaluated for several different transformations where stirring and efficient agitation are known to be of importance. The better performance of these novel stirrers compared to the traditional cylindrical stir bar design is not only due to the geometry of the stirrer but also to the utilization of a magnetic material with a stronger magnetic transmission force (Sm2Co17) compared to standard ferrite or AlNiCo alloys. For all three tested cases involving solid/liquid, liquid/liquid and highly viscous reaction systems, the new vertical blade stirrers showed a distinctively improved performance resulting in higher conversions and/or product yields.

  5. High energy, single mode, all-solid-state and tunable UV laser transmitter

    NASA Astrophysics Data System (ADS)

    Prasad, Narasimha S.; Singh, Upendra N.; Hovis, Floyd; Armstrong, Darrell J.

    2006-05-01

    NASA is developing state-of-the-art, all-solid-state, conductively cooled, diode-pumped, single longitudinal mode, tunable, short-pulsed, and high energy UV transmitters for ozone sensing measurements based on the Differential Absorption Lidar (DIAL) technique. The goal is to demonstrate output pulse energies greater than 200 mJ at pulse repetition frequencies of 10 Hz to 50 Hz, and pulsewidths in the range of 10 ns to 25 ns at UV wavelengths of 308 nm to 320 nm. The proposed scheme is to utilize the robust Nd:YAG pump laser technology in combination with nonlinear optics arrangement comprising of a novel optical parametric oscillator (OPO) and a sum frequency generator (SFG) to generate required UV wavelengths. In this paper, recent results of the development of Nd:YAG pump laser and UV converter module are presented. At 1064 nm, an output pulse energy of 1020 mJ at 16 ns pulsewidth and 50 Hz PRF yielding greater than 7% wall plug efficiency has been demonstrated. With improved drive electronics, this pump laser has the potential to generate greater than 1.2 J/pulse. The refined OPO module to aid in the generation of >200 mJ/pulse of UV radiation is also presented. The UV transmitters are being designed for DIAL operation under strong daylight conditions from space based platforms.

  6. Single-mode optical waveguides on native high-refractive-index substrates

    NASA Astrophysics Data System (ADS)

    Grote, Richard R.; Bassett, Lee C.

    2016-10-01

    High-refractive-index semiconductor optical waveguides form the basis for modern photonic integrated circuits (PICs). However, conventional methods for achieving optical confinement require a thick lower-refractive-index support layer that impedes large-scale co-integration with electronics and limits the materials on which PICs can be fabricated. To address this challenge, we present a general architecture for single-mode waveguides that confine light in a high-refractive-index material on a native substrate. The waveguide consists of a high-aspect-ratio fin of the guiding material surrounded by lower-refractive-index dielectrics and is compatible with standard top-down fabrication techniques. This letter describes a physically intuitive, semi-analytical, effective index model for designing fin waveguides, which is confirmed with fully vectorial numerical simulations. Design examples are presented for diamond and silicon at visible and telecommunications wavelengths, respectively, along with calculations of propagation loss due to bending, scattering, and substrate leakage. Potential methods of fabrication are also discussed. The proposed waveguide geometry allows PICs to be fabricated alongside silicon CMOS electronics on the same wafer, removes the need for heteroepitaxy in III-V PICs, and will enable wafer-scale photonic integration on emerging material platforms such as diamond and SiC.

  7. Observation of single-mode, Kelvin-Helmholtz instability in a supersonic flow

    DOE PAGES

    Wan, W. C.; Malamud, Guy; Shimony, A.; ...

    2015-10-01

    This manuscript reports the first observations of the Kelvin-Helmholtz instability evolving from well-characterized seed perturbations in a steady, supersonic flow. The Kelvin-Helmholtz instability occurs when two fluids move parallel to one another at different velocities, and contributes to an intermixing of fluids and transition to turbulence. It is ubiquitous in nature and engineering, including terrestrial systems such as cloud formations, astrophysical systems such as supernovae, and laboratory systems such as fusion experiments. In a supersonic flow, the growth rate of the instability is inhibited due to effects of compressibility. These effects are still not fully understood, and hold the motivationmore » for the current work. The data presented here were obtained by developing a novel experimental platform capable of sustaining a steady shockwave over a precision-machined interface for unprecedented durations. The chosen interface was a well-characterized, single-mode sine wave, allowing us to document the evolution of individual vortices at high resolution. Understanding the behavior of individual vortices is the first of two fundamental steps towards developing a comprehensive model for the Kelvin-Helmholtz instability in a compressible flow. The results of this experiment were well reproduced with 2D hydrodynamic simulations. The platform has been extended to additional experiments, which study the evolution of different hydrodynamic instabilities in steady, supersonic flows.« less

  8. Emission angle dependence of fission fragment spin: Effects of single particle spin and tilting mode

    NASA Astrophysics Data System (ADS)

    Datta, T.; Naik, H.; Dange, S. P.

    1995-06-01

    The high-spin yield fraction (HSF) for the fission product 132Im,g has been measured as a function of fragment emission angle (90° >=Θ>=10°) in the 237Np(α29 MeV,f) system. It was seen that the HSF for 132I or corresponding fragment (~=134I) spin initially decreases as emission angle decreases from 90° to ~=45° and then steadily increases at lower angles (Θ<45°). Contrary to the present observation in odd-Z 241Am fission, earlier we had observed that fragment spin continuously decreases to a limit with decrease in emission angle from 90° to 20° in even-even 242Pu fission. These data have been analyzed in the framework of the collective mode model invoking the effect of single particle spin. It is seen that for an odd-Z or A fissioning nucleus, angular variation of fragment spin could be accounted for on the basis of coupling between the odd nucleon spin (j>=k~=4ħ) projections and spin due to the collective rotational (tilting) degrees. Collective rotational degrees govern fragment spin for even-even fissioning nucleus.

  9. Adsorption effects on radial breathing mode of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chiashi, Shohei; Kono, Kaname; Matsumoto, Daiki; Shitaba, Junpei; Homma, Naoki; Beniya, Atsushi; Yamamoto, Takahiro; Homma, Yoshikazu

    2015-04-01

    For elucidation of the adsorption effects on the vibration properties of single-walled carbon nanotubes (SWNTs), photoluminescence and Raman scattering spectra from SWNTs at different vapor pressure of water were simultaneously measured and a molecular dynamics (MD) simulation was performed. The water vapor pressure dependence and its tube diameter (dtube) dependence of the frequency of the radial breathing mode (RBM) peaks (ωRBM) and the optical transition energy (Ei i) indicate that the physical adsorption is quite important, and both ωRBM and Ei i clearly depend on the number density of adsorption molecules on the SWNT surface. A simple adsorption model, where the vibrational coupling between the surrounding adsorption layer and SWNTs via van der Waals interaction is considered for RBM, reproduces the experimental and MD simulation results of ωRBM in a wide dtube range for various SWNTs, such as isolated SWNTs in vacuum, SWNTs with adsorption water layer, and even bundled SWNTs. On the basis of the model, the variation of the relationship between ωRBM and Ei i in a Kataura plot for various SWNT samples can also be understood generally as the "environmental effects."

  10. Gamma-radiation-induced degradation of actively pumped single-mode ytterbium-doped optical fibers

    NASA Astrophysics Data System (ADS)

    Singleton, B.; Petrosky, J.; Pochet, M.; Usechak, N. G.; Francis, S. A.

    2014-03-01

    The integration of optical components into the digital processing units of satellite subsystems has the potential to remove interconnect bottlenecks inherent to the volume, mass, complexity, reliability and crosstalk issues of copper-based interconnects. Assuming on-board high-bandwidth communications will utilize passive optical fibers as a communication channel, this work investigates the impact of gamma irradiation from a Co-60 source on both passive optical fibers and ytterbium-doped single-mode fibers operated as amplifiers for a 1060-nm light source. Standard optical patch cables were evaluated along with active Yb-doped double-clad fibers. Varied exposure times and signal transmission wavelengths were used to investigate the degradation of the fibers exposed to total doses above 100 krad (Si). The effect on the amplified signal gain was studied for the Yb-doped fibers. The increased attenuation in the fibers across a broad wavelength range in response to multiple levels of gamma radiation exposure along with the effect that the increased attenuation has on the actively pumped Yb-doped fiber amplifier performance, is discussed.

  11. Nonlinear vibrations and energy exchange of single-walled carbon nanotubes. Circumferential flexural modes

    NASA Astrophysics Data System (ADS)

    Strozzi, Matteo; Smirnov, Valeri V.; Manevitch, Leonid I.; Milani, Massimo; Pellicano, Francesco

    2016-10-01

    In this paper, the nonlinear vibrations and energy exchange of single-walled carbon nanotubes (SWNTs) are studied. The Sanders-Koiter theory is applied to model the nonlinear dynamics of the system in the case of finite amplitude of vibration. The SWNT deformation is described in terms of longitudinal, circumferential and radial displacement fields. Simply supported, clamped and free boundary conditions are considered. The circumferential flexural modes (CFMs) are investigated. Two different approaches based on numerical and analytical models are compared. In the numerical model, an energy method based on the Lagrange equations is used to reduce the nonlinear partial differential equations of motion to a set of nonlinear ordinary differential equations, which is solved by using the implicit Runge-Kutta numerical method. In the analytical model, a reduced form of the Sanders-Koiter theory assuming small circumferential and tangential shear deformations is used to get the nonlinear ordinary differential equations of motion, which are solved by using the multiple scales analytical method. The transition from energy beating to energy localization in the nonlinear field is studied. The effect of the aspect ratio on the analytical and numerical values of the nonlinear energy localization threshold for different boundary conditions is investigated. Time evolution of the total energy distribution along the axis of a simply supported SWNT

  12. Initial Single-Mode Rayleigh-Taylor Growth Rates Measured with the OMEGA Laser System

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Meyerhofer, D. D.; Boehly, T. R.; Ofer, D.; Verdon, C. P.; Bradley, D. K.; McKenty, P. W.; Smalyuk, V. A.

    1996-11-01

    A series of single-mode growth measurements done with the OMEGA laser system are reported. These measurements were done to qualify the laser irradiation and diagnostic suite for future experiments that will use the growth of perturbations at the ablation interface to quantify improvements in irradiation uniformity, reduced growth due to increased ablation velocities, and the effect of increased density scale lengths on the growth rate at the ablation interface. This series of measurements used a laser intensity of 2 × 10^14 W/cm^2 over a spot size of 700 μm for both Gaussian and non-Gaussian shaped pulses with an rms irradiation nonuniformity of 7%. Data were collected with a gated x-ray framing camera with a 10-μm spatial resolution and a 40-ps temporal resolution. This work was supported by the U. S. Department of Energy Office of Inertial Confinement Fusion under cooperative Agreement No. DE-FC03-92SF19460.

  13. Experimental demonstration of single-mode fiber coupling over relatively strong turbulence with adaptive optics.

    PubMed

    Chen, Mo; Liu, Chao; Xian, Hao

    2015-10-10

    High-speed free-space optical communication systems using fiber-optic components can greatly improve the stability of the system and simplify the structure. However, propagation through atmospheric turbulence degrades the spatial coherence of the signal beam and limits the single-mode fiber (SMF) coupling efficiency. In this paper, we analyze the influence of the atmospheric turbulence on the SMF coupling efficiency over various turbulences. The results show that the SMF coupling efficiency drops from 81% without phase distortion to 10% when phase root mean square value equals 0.3λ. The simulations of SMF coupling with adaptive optics (AO) indicate that it is inevitable to compensate the high-order aberrations for SMF coupling over relatively strong turbulence. The SMF coupling efficiency experiments, using an AO system with a 137-element deformable mirror and a Hartmann-Shack wavefront sensor, obtain average coupling efficiency increasing from 1.3% in open loop to 46.1% in closed loop under a relatively strong turbulence, D/r0=15.1.

  14. Investigation of single-mode fiber degradation by 405-nm continuous-wave laser light

    NASA Astrophysics Data System (ADS)

    Gonschior, Cornell P.; Klein, Karl-Friedrich; Menzel, Matthias; Sun, Tong; Grattan, Kenneth T. V.

    2014-12-01

    The degradation of 405-nm fiber-coupled diode laser systems with more than 50 mW power was investigated in detail with focus on the effects occurring at the input end. The coupling and transmission loss of the laser light were associated with the growth of a projection and a periodic structure on the input surface. To avoid this degradation, a short launch fiber with a good surface quality was used at the input end. In this way, the power transmission was stabilized for at least one month. However, structural degradation was noticed on the output surface of the single-mode fiber. To investigate this effect, the damaged samples were measured after different periods of time and examined with a scanning electron microscope and with an atomic force microscope. Reproducible spherical projections with a submicron periodic structure were found in the core region. Additionally, the spectral loss of the fiber was measured, showing the formation of color centers in the deep ultraviolet along the length of the fiber. These investigations were accompanied by simulations of the growth of the structure on the output surface. The influence of the structure was mainly on the divergence angle of the emitted laser beam, reducing the beam quality for applications.

  15. Annealing of linear birefringence in single-mode fiber coils - Application to optical fiber current sensors

    NASA Technical Reports Server (NTRS)

    Tang, Dingding; Rose, A. H.; Day, G. W.; Etzel, Shelley M.

    1991-01-01

    Annealing procedures that greatly reduce linear birefringence in single-mode fiber coils are described. These procedures have been successfully applied to coils ranging from 5 mm to 10 cm in diameter and up to 200 or more turns. They involve temperature cycles that last 3-4 days and reach maximum temperatures of about 850 C. The residual birefringence and induced loss are minimized by proper selection of fiber. The primary application of these coils is optical fiber current sensors, where they yield small sensors that are more stable than those achieved by other techniques. A current sensor with a temperature stability of 8.4 x 10 to the -5th/K over the range from -75 to 145 C has been demonstrated. This is approximately 20 percent greater than the temperature dependence of the Verdet constant. Packaging degrades the stability, but a packaged sensor coil with a temperature stability of about 1.6 + 10 to the -4th/K over the range from -20 to 120 C has also been demonstrated.

  16. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    SciTech Connect

    Knauer, J. P.; Verdon, C. P.; Meyerhofer, D. D.; Boehly, T. R.; Bradley, D. K.; Smalyuk, V. A.; Ofer, D.; McKenty, P. W.; Glendinning, S. G.; Kalantar, D. H.; Watt, R. G.; Gobby, P. L.; Willi, O.; Taylor, R. J.

    1997-04-15

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5x10{sup 14} W/cm{sup 2}. Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600-{mu}m-diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-{mu}m and 60-{mu}m wavelength perturbations was found to be in good agreement with ORCHID simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-{mu}m-thick polystyrene foam buffer layer resulted in reduced growth of the 31-{mu}m perturbation and essentially unchanged growth for the 60-{mu}m case when compared to targets without foam.

  17. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Verdon, C. P.; Meyerhofer, D. D.; Boehly, T. R.; Bradley, D. K.; Smalyuk, V. A.; Ofer, D.; McKenty, P. W.; Glendinning, S. G.; Kalantar, D. H.; Watt, R. G.; Gobby, P. L.; Willi, O.; Taylor, R. J.

    1997-04-01

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5×1014W/cm2. Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600-μm-diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-μm and 60-μm wavelength perturbations was found to be in good agreement with ORCHID simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-μm-thick polystyrene foam buffer layer resulted in reduced growth of the 31-μm perturbation and essentially unchanged growth for the 60-μm case when compared to targets without foam.

  18. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    SciTech Connect

    Knauer, J.P.; Verdon, C.P.; Meyerhofer, D.D.; Boehly, T.R.; Bradley, D.K.; Smalyuk, V.A.; Ofer, D.; McKenty, P.W.; Glendinning, S.G.; Kalantar, D.H.; Watt, R.G.; Gobby, P.L.; Willi, O.; Taylor, R.J.

    1997-04-01

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5{times}10{sup 14}W/cm{sup 2}. Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4{percent}{endash}7{percent} over a 600-{mu}m-diam region defined by the 90{percent} intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-{mu}m and 60-{mu}m wavelength perturbations was found to be in good agreement with {ital ORCHID} simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-{mu}m-thick polystyrene foam buffer layer resulted in reduced growth of the 31-{mu}m perturbation and essentially unchanged growth for the 60-{mu}m case when compared to targets without foam. {copyright} {ital 1997 American Institute of Physics.}

  19. Method for calculating and observing microwave absorption by a sphere in a single mode rectangular cavity

    NASA Technical Reports Server (NTRS)

    Jackson, H. W.; Barmatz, M.

    1991-01-01

    A new theory of microwave absorption by a lossy dielectric sphere in a single mode rectangular cavity has been recently developed. The absorption was treated in the framework of an electromagnetic scattering problem. That theory is summarized here and calculated results that bear on optimizing the processing of materials are illustrated. Methods for observing power absorption and other results predicted by the scattering model are discussed. Cavity perturbation theory provides a bridge between theoretical calculations and experimental observations, and a special problem that arises when an established version of cavity perturbation theory is applied to spheres is identified, analyzed, and resolved. The direct problem of predicting shifts in frequency and Q from model calculations is discussed for a sphere in a cavity when the sphere's complex dielectric constant is known. Also, the inverse problem of determining the complex dielectric constants from measured values of those shifts is considered. The small sphere limit, where an electrostatic or quasistatic model is valid, is treated in detail, and planned work on parallel problems for larger spheres is described.

  20. Numerical Experiments with a Turbulent Single-Mode Rayleigh-Taylor Instability

    SciTech Connect

    Cloutman, L.D.

    2000-04-01

    Direct numerical simulation is a powerful tool for studying turbulent flows. Unfortunately, it is also computationally expensive and often beyond the reach of the largest, fastest computers. Consequently, a variety of turbulence models have been devised to allow tractable and affordable simulations of averaged flow fields. Unfortunately, these present a variety of practical difficulties, including the incorporation of varying degrees of empiricism and phenomenology, which leads to a lack of universality. This unsatisfactory state of affairs has led to the speculation that one can avoid the expense and bother of using a turbulence model by relying on the grid and numerical diffusion of the computational fluid dynamics algorithm to introduce a spectral cutoff on the flow field and to provide dissipation at the grid scale, thereby mimicking two main effects of a large eddy simulation model. This paper shows numerical examples of a single-mode Rayleigh-Taylor instability in which this procedure produces questionable results. We then show a dramatic improvement when two simple subgrid-scale models are employed. This study also illustrates the extreme sensitivity to initial conditions that is a common feature of turbulent flows.

  1. Influence of photo- and thermal bleaching on pre-irradiation low water peak single mode fibers

    NASA Astrophysics Data System (ADS)

    Yin, Jianchong; Wen, Jianxiang; Luo, Wenyun; Xiao, Zhongyin; Chen, Zhenyi; Wang, Tingyun

    2011-12-01

    Reducing the radiation-induced transmission loss in low water peak single mode fiber (LWP SMF) has been investigated by using photo-bleaching method with 980nm pump light source and using thermal-bleaching method with temperature control system. The results show that the radiation-induced loss of pre-irradiation optical fiber can be reduced effectively with the help of photo-bleaching or thermal-bleaching. Although the effort of photo-bleaching is not as significant as thermal-bleaching, by using photo-bleaching method, the loss of fiber caused by radiation-induced defects can be reduced best up to 49% at 1310nm and 28% at 1550nm in low pre-irradiation condition, the coating of the fiber are not destroyed, and the rehabilitating time is just several hours, while self-annealing usually costs months' time. What's more, the typical high power LASER for photo-bleaching can be 980nm pump Laser Diode, which is very accessible.

  2. First results from a laboratory hypertelescope using single-mode fibers

    NASA Astrophysics Data System (ADS)

    Patru, F.; Mourard, D.; Clausse, J.-M.; Delage, L.; Reynaud, F.; Dubreuil, M.; Bonneau, D.; Bosio, S.; Bresson, Y.; Hugues, Y.; Lardière, O.; Roussel, A.

    2008-01-01

    Context: In the future, giant optical interferometric arrays will be developed with kilometric baselines and a large number of telescopes. Such arrays could have direct imaging capabilities if optimized beam combiners are used. Aims: This paper aims at studying the performance of an interferometric beam combiner using single mode fibers and in the frame of a hypertelescope. Methods: A laboratory testbed called SIRIUS was developed. We describe the general concept, the technical specifications and the results obtained. These results are analyzed with the help of a numerical simulator. Results: Direct images were obtained at the densified focus of SIRIUS. We show that the fibers greatly ease the pupil rearrangement. They also greatly improve the quality and the stability of the direct image. The computed images allow us to reproduce the effects of differential photometry and the influence of optical path difference variations. Optical path difference errors less than λ/10 and differential photometries less than 60% are required to keep the quality of the direct image. Conclusions: These results demonstrate the great potential of direct imaging interferometric beam combiners for future optical large arrays. The excellent comparison between experience and simulation clearly shows the simplicity of the fibered pupil densifier. It also gives us a great confidence in the extrapolation of these results and specifications for future arrays with a very large number of apertures.

  3. First results from a laboratory hypertelescope with single-mode fibers

    NASA Astrophysics Data System (ADS)

    Patru, F.; Mourard, D.; Clausse, J. M.; Delage, L.; Reynaud, F.; Dubreuil, M.; Bonneau, D.; Bosio, S.; Bresson, Y.; Hugues, Y.; Lardière, O.; Roussel, A.

    2007-07-01

    In the future, giant optical interferometric arrays will be developed with kilometric baselines and a large number of telescopes. Such arrays could have direct imaging capabilities if optimized beam combiners are used. This paper aims at studying the performances of an interferometric beam combiner using single mode fibers and the hypertelescope principle. A laboratory testbed called SIRIUS has been developed. We present here the results obtained and analyzed with the help of a numerical simulator. Direct images have been obtained at the densified focus of SIRIUS. It is shown that the fibers improve the quality and the stability of the direct image. The computed images allow to reproduce the effects of differential photometry and the influence of optical path difference (OPD) variations. OPD's errors less than λ/10 and differential photometries less than 60% are required to keep the quality of the direct image. The excellent comparison between experience and simulation clearly shows the simplicity of the fibered pupil densifier. It also gives us a great confidence in the extrapolation of these results and specifications for future arrays with a very large number of apertures.

  4. On-sky single-mode fiber coupling measurements at the Large Binocular Telescope

    NASA Astrophysics Data System (ADS)

    Bechter, Andrew; Crass, Jonathan; Ketterer, Ryan; Crepp, Justin R.; Reynolds, Robert O.; Bechter, Eric; Hinz, Philip; Pedichini, Fernando; Foley, Michael; Runburg, Elliott; Onuma, Eleanya E.; Gaudi, Scott; Micela, Giuseppina; Pagano, Isabella; Woodward, Charles E.

    2016-07-01

    The demonstration of efficient single-mode fiber (SMF) coupling is a key requirement for the development of a compact, ultra-precise radial velocity (RV) spectrograph. iLocater is a next generation instrument for the Large Binocular Telescope (LBT) that uses adaptive optics (AO) to inject starlight into a SMF. In preparation for commissioning iLocater, a prototype SMF injection system was installed and tested at the LBT in the Y-band (0.970-1.065 μm). This system was designed to verify the capability of the LBT AO system as well as characterize on-sky SMF coupling efficiencies. SMF coupling was measured on stars with variable airmasses, apparent magnitudes, and seeing conditions for six half-nights using the Large Binocular Telescope Interferometer. We present the overall optical and mechanical performance of the SMF injection system, including details of the installation and alignment procedure. A particular emphasis is placed on analyzing the instrument's performance as a function of telescope elevation to inform the final design of the fiber injection system for iLocater.

  5. Single-mode D-shaped optical fiber sensor for the refractive index monitoring of liquid

    NASA Astrophysics Data System (ADS)

    Qazi, Hummad Habib; Mohammad, Abu Bakar bin; Ahmad, Harith; Zamani Zulkifli, Mohd; Wadi Harun, Sulaiman

    2016-04-01

    A new fabrication method is introduced for the production of D-shaped optical fiber. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of single-mode optical fiber in order to obtain a D-shaped cross section. Adjusting specific mechanical parameters allows for control of the volume of the D-shaped zone, while the fiber surface smoothness is governed by selection of polishing film grit size. To meet the accuracy and repeatability requirements, optical power loss is monitored during the entire polishing process in situ and in real time. This proposed technique possesses advantages of rapidity, safety, simplicity, repeatability and stability with high precision in comparison with contemporary methods for production. Sensor performance tests on the fiber reveal a linear response with linearity up to R2 = 0.984 for surrounding refractive index in the range of 1.320-1.342 refractive index, which corresponds to different concentrations of the glucose solution test environment. The produced D-shaped optical fiber has potential sensing and monitoring applications in chemical, environmental, biological and biochemical fields.

  6. Observation of single-mode, Kelvin-Helmholtz instability in a supersonic flow

    SciTech Connect

    Wan, W. C.; Malamud, Guy; Shimony, A.; Di Stefano, C. A.; Trantham, M. R.; Klein, S. R.; Shvarts, D.; Kuranz, C. C.; Drake, R. P.

    2015-10-01

    This manuscript reports the first observations of the Kelvin-Helmholtz instability evolving from well-characterized seed perturbations in a steady, supersonic flow. The Kelvin-Helmholtz instability occurs when two fluids move parallel to one another at different velocities, and contributes to an intermixing of fluids and transition to turbulence. It is ubiquitous in nature and engineering, including terrestrial systems such as cloud formations, astrophysical systems such as supernovae, and laboratory systems such as fusion experiments. In a supersonic flow, the growth rate of the instability is inhibited due to effects of compressibility. These effects are still not fully understood, and hold the motivation for the current work. The data presented here were obtained by developing a novel experimental platform capable of sustaining a steady shockwave over a precision-machined interface for unprecedented durations. The chosen interface was a well-characterized, single-mode sine wave, allowing us to document the evolution of individual vortices at high resolution. Understanding the behavior of individual vortices is the first of two fundamental steps towards developing a comprehensive model for the Kelvin-Helmholtz instability in a compressible flow. The results of this experiment were well reproduced with 2D hydrodynamic simulations. The platform has been extended to additional experiments, which study the evolution of different hydrodynamic instabilities in steady, supersonic flows.

  7. Dispersion-Tolerant Multiple WDM Channel Millimeter-Wave Signal Generation Using a Single Monolithic Mode-Locked Semiconductor Laser

    NASA Astrophysics Data System (ADS)

    Attygalle, M.; Lim, C.; Nirmalathas, A.

    2005-01-01

    This paper presents a scheme by which multiple wavelength-division-multiplexed millimeter-wave (mm-wave) signals in the range of 30 GHz can be generated from a single monolithic semiconductor laser for applications in optically fed mm-wave networks or fiber radio networks. The mm-wave signals are generated using dual optical modes separated by a mm-wave frequency, obtained from spectrum slicing the output from a stable multimode hybrid mode-locked semiconductor laser. In this scheme, self-heterodyne detection at a high-speed photodetector achieves the photonic upconversion of low-data-rate signals to mm-wave frequencies without the need for electronic mixing. Experimental results show the generation of up to 14 WDM channels using a single laser. The phase noise of electrical signals generated by photonic upconversion of these signals is less than -94 dBc/Hz at 100-kHz offset frequency across the wavelengths. Also presented is the transmission of 155-Mb/s binary-phase-shift-keyed data signals at 30-GHz frequency over 10 km of single-mode fiber at different wavelengths using dual-mode signals. The results confirm that a bit-error rate of 10-^9 can be easily achieved. The dispersion tolerance of the dual-mode signals is evaluated using simulation and an analytical model and compared with other mm-wave signal generation techniques.

  8. Synthesis of the Einstein-Podolsky-Rosen entanglement in a sequence of two single-mode squeezers

    NASA Astrophysics Data System (ADS)

    Fedorov, Ilya A.; Ulanov, Alexander E.; Kurochkin, Yury V.; Lvovsky, A. I.

    2017-01-01

    Synthesis of the Einstein-Podolsky-Rosen entangled state --- the primary entangled resource in continuous-variable quantum-optical information processing --- is a technological challenge of great importance. Here we propose and implement a new scheme of generating this state. Two nonlinear optical crystals, positioned back-to-back in the waist of a pump beam, function as single-pass degenerate optical parametric amplifiers and produce single-mode squeezed vacuum states in orthogonal polarization modes, but in the same spatiotemporal mode. A subsequent pair of waveplates acts as a beam splitter, entangling the two polarization modes to generate the Einstein-Podolsky-Rosen state. This technique takes advantage of the strong nonlinearity associated with type-I phase-matching configuration while at the same time eliminating the need for actively stabilizing the optical phase between the two squeezers, which typically arises if these squeezers are spatially separated. We demonstrate our method in an experiment, preparing a 1.4 dB two-mode squeezed state and characterizing it via two-mode homodyne tomography.

  9. Modulating resonance modes and Q value of a CdS nanowire cavity by single Ag nanoparticles.

    PubMed

    Zhang, Qing; Shan, Xin-Yan; Feng, Xiao; Wang, Chun-Xiao; Wang, Qu-Quan; Jia, Jin-Feng; Xue, Qi-Kun

    2011-10-12

    Semiconductor nanowire (NW) cavities with tailorable optical modes have been used to develop nanoscale oscillators and amplifiers in microlasers, sensors, and single photon emitters. The resonance modes of NW could be tuned by different boundary conditions. However, continuously and reversibly adjusting resonance modes and improving Q-factor of the cavity remain a great challenge. We report a method to modulate resonance modes continuously and reversibly and improve Q-factor based on surface plasmon-exciton interaction. By placing single Ag nanoparticle (NP) nearby a CdS NW, we show that the wavelength and relative intensity of the resonance modes in the NW cavity can systematically be tuned by adjusting the relative position of the Ag NP. We further demonstrate that a 56% enhancement of Q-factor and an equivalent π-phase shift of the resonance modes can be achieved when the Ag NP is located near the NW end. This hybrid cavity has potential applications in active plasmonic and photonic nanodevices.

  10. 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.

  11. Single-transverse-mode near-IR superluminescent diodes with cw output power up to 100 mW

    SciTech Connect

    Andreeva, E V; Il'chenko, S N; Kostin, Yu O; Yakubovich, S D

    2014-10-29

    A series of light-emitting modules based on single-mode quantum-well superluminescent diodes with centre emission wavelengths of about 790, 840, 960 and 1060 nm and a cw output power up to 100 mW in free space is developed. A sufficiently long service life of these devices is demonstrated. (lasers)

  12. Dissociation pathways of a single dimethyl disulfide on Cu(111): Reaction induced by simultaneous excitation of two vibrational modes

    SciTech Connect

    Motobayashi, Kenta; Kim, Yousoo; Arafune, Ryuichi; Ohara, Michiaki; Ueba, Hiromu; Kawai, Maki

    2014-05-21

    We present a novel reaction mechanism for a single adsorbed molecule that proceeds via simultaneous excitation of two different vibrational modes excited by inelastic tunneling electrons from a scanning tunneling microscope. Specifically, we analyze the dissociation of a single dimethyl disulfide (DMDS, (CH{sub 3}S){sub 2}) molecule on Cu(111) by using a versatile theoretical method, which permits us to simulate reaction rates as a function of sample bias voltage. The reaction is induced by the excitation of C-H stretch and S-S stretch modes by a two-electron process at low positive bias voltages. However, at increased voltages, the dissociation becomes a single-electron process that excites a combination mode of these stretches, where excitation of the C-H stretch is the energy source and excitation of the S-S stretch mode enhances the anharmonic coupling rate. A much smaller dissociation yield (few orders of magnitude) at negative bias voltages is understood in terms of the projected density of states of a single DMDS on Cu(111), which reflects resonant excitation through the molecular orbitals.

  13. Influence of weather conditions on splicing process and parameters of splicing single-mode telecommunication fibers of different types

    NASA Astrophysics Data System (ADS)

    Ratuszek, Marek; Zakrzewski, Zbigniew; Majewski, Jacek; Strozecki, Stefan; Zalewski, Jozef; Konefal, Tadeusz; Kula, Witold

    1999-05-01

    Results of research on the influence of weather conditions (t equals 10 divided by 27 degree(s)C; H equals 30 divided by 90%) on the process of splicing of standard single mode fibers SM (G.652) and fibers with dispersion shifted DS (G.653) have been presented as well as the results of optimization of splicing SM and DS fibers.

  14. Single-mode lasing of Ho:Tm:YAG at 2.091 microns in a monolithic crystal

    NASA Technical Reports Server (NTRS)

    Storm, Mark E.; Koch, Grady J.; Rohrbach, Wayne W.

    1991-01-01

    This paper demonstrates single-longitudinal-mode lasing of Ho:Tm:YAG at 2.091 microns in a diode-laser-pumped monolithic crystal. Heterodyne detection at 2.1 microns is demonstrated, and energy diffusion effects on spatial hole burning are discussed. Temperature tuning over 4.5 A is demonstrated.

  15. 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.

  16. Extension of the broadband single-mode integrated optical waveguide technique to the ultraviolet spectral region and its applications.

    PubMed

    Wiederkehr, Rodrigo S; Mendes, Sergio B

    2014-03-21

    We report here the fabrication, characterization, and application of a single-mode integrated optical waveguide (IOW) spectrometer capable of acquiring optical absorbance spectra of surface-immobilized molecules in the visible and ultraviolet spectral region down to 315 nm. The UV-extension of the single-mode IOW technique to shorter wavelengths was made possible by our development of a low-loss single-mode dielectric waveguide in the UV region based on an alumina film grown by atomic layer deposition (ALD) over a high quality fused silica substrate, and by our design/fabrication of a broadband waveguide coupler formed by an integrated diffraction grating combined with a highly anamorphic optical beam of large numerical aperture. As an application of the developed technology, we report here the surface adsorption process of bacteriochlorophyll a on different interfaces using its Soret absorption band centred at 370 nm. The effects of different chemical compositions at the solid-liquid interface on the adsorption and spectral properties of bacteriochlorophyll a were determined from the polarized UV-Vis IOW spectra acquired with the developed instrumentation. The spectral extension of the single-mode IOW technique into the ultraviolet region is an important advance as it enables extremely sensitive studies in key characteristics of surface molecular processes (e.g., protein unfolding and solvation of aromatic amino-acid groups under surface binding) whose spectral features are mainly located at wavelengths below the visible spectrum.

  17. Dissociation pathways of a single dimethyl disulfide on Cu(111): reaction induced by simultaneous excitation of two vibrational modes.

    PubMed

    Motobayashi, Kenta; Kim, Yousoo; Arafune, Ryuichi; Ohara, Michiaki; Ueba, Hiromu; Kawai, Maki

    2014-05-21

    We present a novel reaction mechanism for a single adsorbed molecule that proceeds via simultaneous excitation of two different vibrational modes excited by inelastic tunneling electrons from a scanning tunneling microscope. Specifically, we analyze the dissociation of a single dimethyl disulfide (DMDS, (CH3S)2) molecule on Cu(111) by using a versatile theoretical method, which permits us to simulate reaction rates as a function of sample bias voltage. The reaction is induced by the excitation of C-H stretch and S-S stretch modes by a two-electron process at low positive bias voltages. However, at increased voltages, the dissociation becomes a single-electron process that excites a combination mode of these stretches, where excitation of the C-H stretch is the energy source and excitation of the S-S stretch mode enhances the anharmonic coupling rate. A much smaller dissociation yield (few orders of magnitude) at negative bias voltages is understood in terms of the projected density of states of a single DMDS on Cu(111), which reflects resonant excitation through the molecular orbitals.

  18. A simple numerical method for the cutoff frequency of a single-mode fiber with an arbitrary index-profile

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Ghatak, A. K.

    1981-06-01

    A simple numerical method for calculating the cutoff frequency of single-mode operation in optical fibers with an arbitrary index-profile is presented. The method does not involve any approximation other than the scalar approximation and is applicable even to numerical data from index-profile measurements. The calculations are simple and can be carried out even on a programmable calculator.

  19. Analysis of surface plasmon resonance in bent single-mode waveguides with metal-coated cladding by eigenmode expansion method.

    PubMed

    Kulchin, Yu N; Vitrik, O B; Dyshlyuk, A V

    2014-09-08

    A numerical study is presented of surface plasmon waves excitation in a metal film applied to the cladding of a standard bent single-mode optical fiber. It was shown that by adjusting the bend radius and metal film thickness one can achieve effective coupling between the fiber fundamental mode and symmetric surface plasmon mode through the intermediary of whispering gallery modes supported by the cladding of the bent fiber. This effect is demonstrated to allow for refractometric measurement both in the wavelength and intensity-modulated regimes with a resolution of up to 10⁻⁸ RIU. Usage of standard noise reduction techniques for intensity-modulated optical signals promises further increase in accuracy.

  20. Fingerprinting of traditional Chinese medicines on the C18-Diol mixed-mode column in online or offline two-dimensional liquid chromatography on the single column modes.

    PubMed

    Wang, Qing; Tong, Ling; Yao, Lin; Zhang, Peng; Xu, Li

    2016-06-05

    In the present study, a mixed-mode stationary phase, C18-Diol, was applied for fingerprint analysis of traditional Chinese medicines. Hydrophobic, hydrogen bonding and electrostatic interactions were demonstrated to contribute the retention separately or jointly, which endowed the C18-Diol stationary phase with distinct selectivity compared to the bare C18 one. The separation of total alkaloids extracted from Fritillaria hupehensis was compared on the C18-Diol and conventional C18 column with the greater resolving power and better symmetry responses on the former one. Besides, a novel two-dimensional liquid chromatography on the single column (2D-LC-1C) was realized on C18-Diol with the offline mode for the alcohol extract of Fritillaria hupehensis and online mode for Ligusticum chuanxiong Hort. The early co-eluted extracted components with great polarity on the first dimension were reinjected on the same column and well separated on the second dimension. The results exhibited that the two complementary RPLC and HILIC modes on C18-Diol stationary phase enhanced the separation capacity and revealed more abundant chemical information of the sample, which was a powerful tool in analyzing complex herbal medicines.

  1. A new single-mode LMA optical fiber based on an anti-resonance in the cladding

    NASA Astrophysics Data System (ADS)

    Sharabi, Avidan; Sheintop, Uzziel; Goldin, Shlomo

    2016-03-01

    A novel single-mode large-mode-area (LMA) optical fiber is proposed. The primary part of the cladding is a thin layer with high refractive index. The layer possesses a periodic array of holes (or intrusions) which are either drawn in the propagation direction or drilled in the radial direction. When the holes (or intrusions) are drawn in the propagation direction, the periodicity of their array is in the azimuthal direction. The core may be hollow. The light confinement is achieved via a transmission anti-resonance. Namely, the array of holes allows coupling between an optical mode inside the primary cladding layer and the light both in the core and in the outer space. The light then sees two channels to penetrate the cladding: direct transmission and holes-assisted transmission. A distractive interference between these channels is achieved at an appropriate combination of fiber parameters. The fiber can be designed to hold nearly anyone of TE/TMnm modes. Computer simulations of the fiber were performed using COMSOL. The open boundary was simulated using a perfectly matched layer and the attenuation constants of different modes were determined via the imaginary parts of their propagation constants. As an example, a fiber holding a single TE01 mode inside a core of 100 μm diameter for the vacuum wavelength 1.55 μm was designed. The attenuation constant of the TE01 mode was found to be 5.8 ṡ 10-6 [dB/cm] while the other modes had attenuation of at least 4 orders of magnitude larger. Required fabrication tolerances were calculated and the fabrication of fibers of lengths 10 - 1000 m was found to be feasible. The bandwidth of the fiber was found to be in the range of 5 - 35 nm, depending on its length. Possible applications include high-power CW and pulsed lasers and amplifiers, sensors and others.

  2. Reliability, failure modes, and degradation mechanisms in high power single- and multi-mode InGaAs-AlGaAs strained quantum well lasers

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Presser, Nathan; Lingley, Zachary; Brodie, Miles; Foran, Brendan; Moss, Steven C.

    2016-03-01

    High power single-mode (SM) and multi-mode (MM) InGaAs-AlGaAs strained quantum well (QW) lasers are critical components for both telecommunications and potential space satellite communications systems. However, little has been reported on failure modes of state-of-the-art SM InGaAs-AlGaAs strained QW lasers although it is crucial to understand failure modes and underlying degradation mechanisms in developing these lasers that meet lifetime requirements for space satellite systems, where extremely high reliability of these lasers is required. Our present study addresses the aforementioned issues by performing long-term life tests under different test conditions followed by failure mode analysis (FMA) and physics of failure investigation. We performed long-term accelerated life-tests on state-of-the-art SM and MM InGaAs-AlGaAs strained QW lasers under ACC (automatic current control) mode. Our life-tests have accumulated over 25,000 test hours for SM lasers and over 35,000 test hours for MM lasers. FMA was performed on failed SM lasers using electron beam induced current (EBIC). This technique allowed us to identify failure types by observing dark line defects. All the SM failures we studied showed catastrophic and sudden degradation and all of these failures were bulk failures. Our group previously reported that bulk failure or COBD (catastrophic optical bulk damage) is the dominant failure mode of MM InGaAs-AlGaAs strained QW lasers. To the best of our knowledge, this is the first report demonstrating that the dominant failure mode of both SM and MM InGaAs-AlGaAs strained QW lasers is the bulk failure. Since degradation mechanisms responsible for COBD are still not well understood, we also employed other techniques including focused ion beam (FIB) processing and high-resolution TEM to further study dark line defects and dislocations in post-aged SM and MM lasers. Our long-term life test results and FMA results are reported.

  3. The equilibrium concentration of hydrogen atoms ahead of a mixed mode I-mode III crack tip in single crystal iron

    SciTech Connect

    Zhang, T.Y.; Hack, J.E.

    1999-01-01

    Calculations of the equilibrium hydrogen concentration profiles about a mixed ode I-mode III crack in single crystal iron were performed. Both material anisotropy and the tetragonal nature of the distortion induced in the iron crystal structure by interstitial hydrogen were incorporated. Results show that, unlike the case of a spherical distortion, a strong coupling exists between the strain field of the interstitial hydrogen and the stress field of the crack for orientations of the crack plane that are not coincident with the cube axes of the lattice. As a result, the predicated enhancement of hydrogen in the crack tip region increases with increasing levels of mode III loading for those orientations. The results may help reconcile conflicting observations concerning the potential role of shear stresses in hydrogen embrittlement and preferential cracking of grains ahead of loaded crack tips in sustained load cracking experiments.

  4. Physics of reshock and mixing in single-mode Richtmyer-Meshkov instability

    SciTech Connect

    Schilling, O; Latini, M; Don, W

    2006-12-13

    The ninth-order weighted essentially non-oscillatory (WENO) shock-capturing method is used to investigate the physics of reshock and mixing in two-dimensional single-mode Richtmyer-Meshkov instability to late times. The initial conditions and computational domain were adapted from the Mach 1.21 air(acetone)/SF{sub 6} shock tube experiment of Collins and Jacobs [J. Fluid Mech. 464, 113 (2002)]: the growth of the bubble and spike perturbation amplitudes from fifth- and ninth-order WENO simulations of this experiment were compared to the predictions of amplitude growth models, and were shown to be in very good agreement with the experimental data prior to reshock [Latini, Schilling and Don, Phys. Fluids (2007), in press]. In the present investigation, the density, vorticity, baroclinic vorticity production, and simulated density Schlieren fields are first presented to qualitatively describe reshock. The baroclinic circulation deposition on the interface is shown to agree with the predictions of the Samtaney and Zabusky [J. Fluid Mech. 269, 45 (1994)] model and linear instability theory. The time-evolution of the positive and negative circulation on the interface is considered before and after reshock: it is shown that the circulations are equal before, as well as after reshock, until the interaction of the reflected rarefaction with the layer leads to flow symmetry breaking and different evolutions of the positive and negative circulation. The post-reshock mixing layer growth is shown to be in very good agreement with three models predicting linear growth for a short time following reshock. Next, a comprehensive investigation of local and global mixing properties as a function of time is performed. The distribution and amount of mixed fluid along the shock propagation direction is characterized using averaged mole fraction profiles, a fast kinetic reaction model, and molecular mixing fractions. The modal distribution of energy in the mixing layer is quantified using

  5. Regrowth-free single-mode quantum cascade lasers with power consumption below 1 W

    SciTech Connect

    Briggs, Ryan M. Frez, Clifford; Borgentun, Carl E.; Forouhar, Siamak

    2014-10-06

    We report on single-mode distributed-feedback quantum cascade lasers emitting at 4.8 μm with continuous-wave threshold power consumption as low as 0.76 W at 20 °C and 0.98 W at 50 °C. Following growth of the laser active region and semiconductor cladding layers by a single molecular beam epitaxy process, devices with 4-μm-wide ridges and vertical sidewall gratings were fabricated using plasma etching and standard dielectric and metal deposition processes. In terms of mode stability, output power, and efficiency, we show that lasers with 1-mm cavity length and high-reflectivity back-facet coatings can match the performance of buried heterostructure devices, but with the advantage of requiring only a single epitaxial growth step.

  6. Numerical investigation of a single-mode chemically reacting Richtmyer-Meshkov instability

    NASA Astrophysics Data System (ADS)

    Attal, N.; Ramaprabhu, P.

    2015-07-01

    We report on high-resolution, numerical simulations of a single-mode, chemically reacting, Richtmyer-Meshkov (RM) instability, at different interface thicknesses. The gases on either side of the diffuse interface were Hydrogen (H and Oxygen (O, with a pre-shock Atwood number of 0.5. An incident shock with a Mach number of 1.2 is allowed to traverse from the light (H to the heavy (O medium in the 2D numerical shock tube. The simulations were performed using the astrophysical FLASH code developed at the University of Chicago, with extensive modifications implemented by the authors to describe detailed H-O chemistry, temperature-dependent specific heats, and multi-species equation of state. The interface thickness was systematically varied in the simulations to study the effect of the total mass of fuel burnt and heat added on the hydrodynamic instability growth rates. In the absence of an incident shock, burning results in the formation of so-called combustion waves, which spontaneously trigger RM and Rayleigh-Taylor like instability growth of the interface. We are able to obtain the resulting growth rates of an imposed sinusoidal perturbation, and compare them with the predictions of an impulsive model, with simple modifications to account for the finite thickness of the interface, density changes due to heat addition, and compression of the material line due to the combustion wave. When additionally an incident shock is present, we observe complex interactions between the shock and the aforementioned combustion waves, resulting in significant non-planar distortions of each. When the unstable interface is subjected to a reshock, significant mixing enhancement is observed, accompanied by a dramatic increase in combustion product formation, and combustion efficiency.

  7. Model of a single mode energy harvester and properties for optimal power generation

    NASA Astrophysics Data System (ADS)

    Liao, Yabin; Sodano, Henry A.

    2008-12-01

    The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. In the last few years, the field of power harvesting has experienced significant growth due to the ever increasing desire to produce portable and wireless electronics with extended life. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their finite energy supply, which necessitates their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and covert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. The development of energy harvesting systems is greatly facilitated by an accurate model to assist in the design of the system. This paper will describe a theoretical model of a piezoelectric based energy harvesting system that is simple to apply yet provides an accurate prediction of the power generated around a single mode of vibration. Furthermore, this model will allow optimization of system parameters to be studied such that maximal performance can be achieved. Using this model an expression for the optimal resistance and a parameter describing the energy harvesting efficiency will be presented and evaluated through numerical simulations. The second part of this paper will present an experimental validation of the model and optimal parameters.

  8. Toward photostable multiplex analyte detection on a single mode planar optical waveguide

    SciTech Connect

    Mukundan, Harshini; Xei, Hongshi; Anderson, Aaron S; Grace, Wynne K; Martinez, Jennifer S; Swanson, Basil

    2009-01-01

    We have developed a waveguide-based optical biosensor for the sensitive and specific detection of biomarkers associated with disease. Our technology combines the superior optical properties of single-mode planar waveguides, the robust nature of functionalized self-assembled monolayer sensing films and the specificity of fluorescence sandwich immunoassays to detect biomarkers in complex biological samples such as serum, urine and sputum. We have previously reported the adaptation of our technology to the detection of biomarkers associated with breast cancer and anthrax. However, these approaches primarily used phospholipid bilayers as the functional film and organic dyes (ex: AlexaFluors) as the fluorescence reporter. Organic dyes are easily photodegraded and are not amenable to multiplexing because of their narrow Stokes' shift. Here we have developed strategies for conjugation of the detector antibodies with quantum dots for use in a multiplex detection platform. We have previously evaluated dihydroxylipoic acid quantum dots for the detection of a breast cancer biomarker. In this manuscript, we investigate the detection of the Bacillus anthracis protective antigen using antibodies conjugated with polymer-coated quantum dots. Kinetics of binding on the waveguide-based biosensor is reported. We compare the sensitivity of quantum dot labeled antibodies to those labeled with AlexaFluor and demonstrate the photostability of the former in our assay platform. In addition, we compare sulfydryl labeling of the antibody in the hinge region to that of nonspecific amine labeling. This is but the first step in developing a multiplex assay for such biomarkers on our waveguide platform.

  9. Toward photostable multiplex analyte detection on a single mode planar optical waveguide

    NASA Astrophysics Data System (ADS)

    Mukundan, Harshini; Xie, Hongzhi; Anderson, Aaron; Grace, W. Kevin; Martinez, Jennifer S.; Swanson, Basil

    2009-02-01

    We have developed a waveguide-based optical biosensor for the sensitive and specific detection of biomarkers associated with disease. Our technology combines the superior optical properties of single-mode planar waveguides, the robust nature of functionalized self-assembled monolayer sensing films and the specificity of fluorescence sandwich immunoassays to detect biomarkers in complex biological samples such as serum, urine and sputum. We have previously reported the adaptation of our technology to the detection of biomarkers associated with breast cancer and anthrax. However, these approaches primarily used phospholipid bilayers as the functional film and organic dyes (ex: AlexaFluors) as the fluorescence reporter. Organic dyes are easily photodegraded and are not amenable to multiplexing because of their narrow Stokes' shift. Here we have developed strategies for conjugation of the detector antibodies with quantum dots for use in a multiplex detection platform. We have previously evaluated dihydroxylipoic acid quantum dots for the detection of a breast cancer biomarker. In this manuscript, we investigate the detection of the Bacillus anthracis protective antigen using antibodies conjugated with polymer-coated quantum dots. Kinetics of binding on the waveguide-based biosensor is reported. We compare the sensitivity of quantum dot labeled antibodies to those labeled with AlexaFluor and demonstrate the photostability of the former in our assay platform. In addition, we compare sulfydryl labeling of the antibody in the hinge region to that of nonspecific amine labeling. This is but the first step in developing a multiplex assay for such biomarkers on our waveguide platform.

  10. Self-emission glucose monitoring system with single chip guided-mode resonance filters

    NASA Astrophysics Data System (ADS)

    Yeh, Yen-Chun; Yang, Sheng; Schmidt, Dominik

    2016-03-01

    In this study, we designed and simulated an array of bandpass filters as a spectral separator for mid-infrared self-emission noninvasive glucose monitoring, using the human body as the background radiation emitter. The filters were based on the guided-mode resonance (GMR) effect. The human body is a good black body radiator that provides a stable temperature and continuous radiation energy in the mid-infrared range. We can thus use self-emission from the human body to measure certain fingerprint peaks of glucose spectrum between 8 μm to 10 μm, which allows estimation of glucose concentration. The GMR filter set includes at least four filters on one chip fabricated at the same time. By using fixed thicknesses and the same thin-film material for all the filters on the chip, a structure period adjustment alone can theoretically achieve multiple bandpass filters between the glucose fingerprint ranges - and achieve these coplanar filters on a single chip. By using all CMOS-compatible materials, COMSOL simulations show that a series of peaks with transmittances up to 70% and bandwidths of around 200nm can be achieved. This filter set can be fabricated with just a few thin layers that can simplify the typical thin-film deposition process. The proposed GMR filter array can then be combined with a thermometer array to achieve the non-invasive glucose monitoring. We compare the results obtained with the first version of the fabricated filter set with the measurements of Fourier transform infrared (FT-IR) spectroscopy.

  11. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.; Glendinning, S. G.; Kalantar, D. H.; Watt, R. G.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5×1014 W/cm2. Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 μm diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 μm wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile.

  12. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    SciTech Connect

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10{sup 14} W/cm{sup 2}. Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 {mu}m diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 {mu}m wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics.

  13. Narrow line-width single-longitudinal-mode fiber laser using silicon-on-insulator based micro-ring-resonator

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Hsu, Yung; Hsu, Chin-Wei; Yang, Ling-Gang; Chow, Chi-Wai; Yeh, Chien-Hung; Lai, Yin-Chieh; Tsang, Hon-Ki

    2016-02-01

    In this work, we propose and demonstrate a stable single-longitudinal-mode (SLM) fiber laser with narrow line-width by using an integrated silicon-on-insulator micro-ring resonator (SOI MRR) and two subsidiary fiber rings for the first time, to the best of our knowledge. The laser is tunable over the wavelength range from 1546 to 1570 nm, with only step tuning of 2 nm steps. A maximum 49 dB side mode suppression ratio (SMSR) can be achieved. The compact SOI MRR provides a large free-spectral-range (FSR), while the subsidiary rings provide Vernier effect producing a single lasing mode. The FSR of the SOI MRR can be very large and controllable (since it is easy to fabricate small SOI MRR when compared with making small fiber-rings) using the complementary-metal-oxide-semiconductor (CMOS) compactable SOI fabrication processes. In our proposed laser, the measured single sideband (SSB) spectrum shows that the densely spaced longitudinal modes can be significantly suppressed to achieve SLM. The laser linewidth is only 3.5 kHz measured by using the self-heterodyne method. 30 min stability evaluation in terms of lasing wavelength and optical power is performed; showing the optical wavelength and power are both very stable, with fluctuations of only 0.02 nm and 0.8 dB, respectively.

  14. Q-switched and mode-locked Er{sup 3+}-doped fibre laser using a single-multi-single fibre filter and piezoelectric

    SciTech Connect

    Ji Wang; Yunjun Zhang; Aotuo Dong; Xiaoxin Xu; Youlun Ju; Baoquan Yao

    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 energy 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)

  15. Q-switched and mode-locked Er3+-doped fibre laser using a single-multi-single fibre filter and piezoelectric

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Zhang, Yunjun; Dong, Aotuo; Xu, Xiaoxin; Ju, Youlun; Yao, Baoquan

    2014-04-01

    The active Q-switched and passive mode-locked Er3+-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 energy 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.

  16. Catastrophic facet and bulk degradation in high power multi-mode InGaAs strained quantum well single emitters

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Presser, Nathan; Foran, Brendan; Ives, Neil; Moss, Steven C.

    2009-02-01

    Extensive investigations by a number of groups have identified catastrophic sudden degradation as the main failure mode in both single-mode and multi-mode InGaAs-AlGaAs strained quantum well (QW) lasers. Significant progress made in performance characteristics of broad-area InGaAs strained QW single emitters in recent years has led to an optical output power of over 20W and a power conversion efficiency of over 70% under CW operation. However, unlike 980nm single-mode lasers that have shown high reliability operation under a high optical power density of ~50MW/cm2, broad-area lasers have not achieved the same level of reliability even under a much lower optical power density of ~5MW/cm2. This paper investigates possible mechanisms that prevent broad-area lasers from achieving high reliability operation by performing accelerated lifetests of these devices and in-depth failure mode analyses of degraded devices with various destructive and non-destructive techniques including EBIC, FIB, and HR-TEM techniques. The diode lasers that we have investigated are commercial MOCVD-grown broad-area strained InGaAs single QW lasers at ~975nm. Both passivated and unpassivated broad-area lasers were studied that yielded catastrophic failures at the front facet and also in the bulk. To investigate the role that generation and propagation of defects plays in degradation processes via recombination enhanced defect reaction (REDR), EBIC was employed to study dark line defects in degraded lasers, failed under different stress conditions, and the correlation between DLDs and stress levels is reported. FIB was then employed to prepare TEM samples from the DLD areas for cross-sectional HR-TEM analysis.

  17. On-chip waveguide isolator based on bismuth iron garnet operating via nonreciprocal single-mode cutoff.

    PubMed

    Drezdzon, Samuel M; Yoshie, Tomoyuki

    2009-05-25

    We analyze an on-chip optical isolator based on direction dependent single-mode cutoff, which is described in 1D and 2D momentum space. Isolation is shown using 3D finite difference time domain (FDTD) where the magnetization is represented by imaginary off-diagonal permittivity tensor elements. The isolator designs are optimized using perturbation theory, which successfully predicts increased isolation for rib waveguides and structures with non-magnetic dielectric layers. Our isolators are based on bismuth iron garnet and its compatible substrates; an isolation ratio of 10.7 dB/mm is achieved for TM modes.

  18. High spatial resolution mapping of surface plasmon resonance modes in single and aggregated gold nanoparticles assembled on DNA strands

    PubMed Central

    2013-01-01

    Abstract We present the mapping of the full plasmonic mode spectrum for single and aggregated gold nanoparticles linked through DNA strands to a silicon nitride substrate. A comprehensive analysis of the electron energy loss spectroscopy images maps was performed on nanoparticles standing alone, dimers, and clusters of nanoparticles. The experimental results were confirmed by numerical calculations using the Mie theory and Gans-Mie theory for solving Maxwell's equations. Both bright and dark surface plasmon modes have been unveiled. PACS 78.67.Bf; 61.46.Df; 87.64.Ee PMID:23890222

  19. 177 fs erbium-doped fiber laser mode locked with a cellulose polymer film containing single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tausenev, A. V.; Obraztsova, E. D.; Lobach, A. S.; Chernov, A. I.; Konov, V. I.; Kryukov, P. G.; Konyashchenko, A. V.; Dianov, E. M.

    2008-04-01

    A mode-locked soliton erbium-doped fiber laser generating 177fs pulses is demonstrated. The laser pumped by a 85mW, 980nm laser diode emits 7mW at 1.56μm at a pulse repetition rate of 50MHz. Passive mode locking is achieved with a saturable absorber made of a high-optical quality film based on cellulose derivative with dispersed carbon single-wall nanotubes. The film is prepared with the original technique by using carbon nanotubes synthesized by the arc-discharge method.

  20. Orientation-recognized rotation measurement using single polarimetric multi-mode tilted fiber grating

    NASA Astrophysics Data System (ADS)

    Liu, Fu; Guo, Tuan; Shang, Libin; Zhang, Zhaochuan; Du, Fa; Guan, Bai-Ou; Albert, Jacques

    2014-05-01

    The polarimetric sensing characteristics of multi-mode-fiber based tilted fiber Bragg grating (MMF-TFBG) have been analyzed and experimentally demonstrated. The physical "enlarged" fiber core enables the tilted gratings to excite multi high-order core modes with significantly different polarization dependence and well-defined "comb" profiles which are spectrally separated at different wavelength. Orientation-recognized twist/rotation measurement (-90o to 90o) has been achieved with sensitivity of 0.075 dB/deg by using a cost-effective double-path power detection (power monitoring of two orthogonal-polarimetric odd core-modes, i.e. LP11 and LP12).

  1. The late-time dynamics of the single-mode Rayleigh-Taylor instability

    NASA Astrophysics Data System (ADS)

    Ramaprabhu, P.; Dimonte, Guy; Woodward, P.; Fryer, C.; Rockefeller, G.; Muthuraman, K.; Lin, P.-H.; Jayaraj, J.

    2012-07-01

    We report on numerical simulations of the detailed evolution of the single mode Rayleigh-Taylor [Lord Rayleigh, Scientific Papers II (Cambridge University Press, Cambridge, 1900), p. 200; G. I. Taylor, "The instability of liquid surfaces when accelerated in a direction perpendicular to their plane," Proc. R. Soc. London, Ser. A 201, 192 (1950), 10.1098/rspa.1950.0052; S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Oxford University Press, Oxford, 1961)] instability to late times and high aspect ratios. In contrast to established potential flow models that predict a terminal velocity and a constant Froude number at low Atwood numbers, we observe a complex sequence of events that can be summarized in four stages: I. Exponential growth of imposed perturbations, II. Saturation to terminal velocity, III. Reacceleration to a higher Froude number, and IV. Chaotic mixing. The observed reacceleration away from the Froude number predicted by potential flow theory is attributed to the appearance of secondary Kelvin-Helmholtz structures, and described with a modification to the potential flow model proposed by Betti and Sanz [R. Betti and J. Sanz, "Bubble acceleration in the ablative Rayleigh-Taylor instability," Phys. Rev. Lett. 97, 205002 (2006), 10.1103/PhysRevLett.97.205002]. The secondary KH instability is in turn sensitive to several parameters, and can be suppressed at large Atwood numbers, as well as viscosity (physical or numerical), with the bubble/spike velocity in each case reverting to the potential flow value. Our simulations delineate the change in dynamics of the primary and secondary instabilities due to changes in these flow parameters. When the flow is allowed to evolve to late times, further instability is observed, resulting in chaotic mixing which is quantified here. The increased atomic mixing due to small-scale structures results in a dramatic drop in the late-time Froude number. Spike behavior resembles bubbles at low A, while for large A

  2. Design and prototyping of self-centering optical single-mode fiber alignment structures

    NASA Astrophysics Data System (ADS)

    Ebraert, Evert; Gao, Fei; Beri, Stefano; Watté, Jan; Thienpont, Hugo; Van Erps, Jürgen

    2016-06-01

    The European Commission’s goal of providing each European household with at least a 30 Mb s-1 Internet connection by 2020 would be facilitated by a widespread deployment of fibre-to-the-home, which would in turn be sped up by the development of connector essential components, such as high-precision alignment features. Currently, the performance of state-of-the-art physical contact optical fiber connectors is limited by the tolerance on the cladding of standard telecom-grade single-mode fiber (SMF), which is typically smaller than  ±1 μm. We propose to overcome this limit by developing micro-spring-based self-centering alignment structures (SCAS) for SMF-connectors. We design these alignment structures with robustness and low-cost replication in mind, allowing for large-scale deployment. Both theoretical and finite element analysis (FEA) models are used to determine the optimal dimensions of the beams of which the micro-springs of the SCAS are comprised. Two topologies of the SCAS, consisting of three and four micro-springs respectively, are investigated for two materials: polysulfone (PSU) and polyetherimide (PEI). These materials hold great potential for high-performance fiber connectors while being compatible with low-cost production and with the harsh environmental operation conditions of those connectors. The theory and FEA agree well (<3% difference) for a simple micro-spring. When including a pedestal on the micro-spring (to bring it further away from the fiber) and for shorter spring lengths the agreement worsens. This is due to spring compression effects not being taken into account in our theoretical model. Prototypes are successfully fabricated using deep proton writing and subsequently characterized. The controlled insertion of an SMF in the SCAS is investigated and we determine that a force of 0.11 N is required. The fiber insertion also causes an out-of-plane deformation of the micro-springs in the SCAS of about 7 μm, which is no problem for

  3. Mixed-mode I+II fracture characterization of human cortical bone using the Single Leg Bending test.

    PubMed

    Silva, F G A; de Moura, M F S F; Dourado, N; Xavier, J; Pereira, F A M; Morais, J J L; Dias, M I R

    2016-02-01

    Mixed-mode I+II fracture characterization of human cortical bone was analyzed in this work. A miniaturized version of the Single Leg Bending test (SLB) was used owing to its simplicity. A power law criterion was verified to accurately describe the material fracture envelop under mixed-mode I+II loading. The crack tip opening displacements measured by digital image correlation were used in a direct method to determine the cohesive law mimicking fracture behavior of cortical bone. Cohesive zone modeling was used for the sake of validation. Several fracture quantities were compared with the experimental results and the good agreement observed proves the appropriateness of the proposed procedure for fracture characterization of human bone under mixed-mode I+II loading.

  4. Stabilized and tunable single-longitudinal-mode erbium fiber laser employing ytterbium-doped fiber based interference filter

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Tsai, Ning; Zhuang, Yuan-Hong; Chow, Chi-Wai; Chen, Jing-Heng

    2017-02-01

    In this demonstration, to achieve stabilized and wavelength-selectable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser, a short length of ytterbium-doped fiber (YDF) is utilized to serve as a spatial multi-mode interference (MMI) inside a fiber cavity for suppressing multi-longitudinal-mode (MLM) significantly. In the measurement, the output powers and optical signal to noise ratios (OSNRs) of proposed EDF ring laser are measured between -9.85 and -5.71 dBm; and 38.03 and 47.95 dB, respectively, in the tuning range of 1530.0-1560.0 nm. In addition, the output SLM and stability performance are also analyzed and discussed experimentally.

  5. Utilizing ytterbium- and erbium-doped fibers for a selectable and stable single-longitudinal-mode fiber ring laser

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Tsai, Ning; Zhuang, Yuan-Hong

    2016-05-01

    In this paper, a stable and wavelength-tunable C-band erbium-doped fiber (EDF) ring laser is experimentally demonstrated. Here, utilizing an unpumped ytterbium-doped fiber with a length of 0.6 m inside the ring cavity serving as a spatial multi-mode interference is proposed to suppress the multi-longitudinal-mode for single-longitudinal-mode output. Therefore, the output powers and optical signal-to-noise ratios of the proposed EDF ring laser are between  -11.74 and  -4.65 dBm and 34.3 and 26.9 dB, respectively. Moreover, the output performance of stability is also analyzed and discussed.

  6. Efficient single-mode (TEM{sub 00}) Nd : YVO{sub 4} laser with longitudinal 808-nm diode pumping

    SciTech Connect

    Donin, V I; Yakovin, D V; Yakovin, M D

    2013-10-31

    A single-mode Nd : YVO{sub 4} laser with unidirectional longitudinal pumping by laser diodes with λ = 808 nm and a power of 40 W is studied. In the TEM{sub 00} mode, the output laser power is 24 W with the optical efficiency η{sub opt} = 57.1 % (slope efficiency 63.3 %), which, as far as we know, is the best result for Nd{sup 3+} : YVO{sub 4} lasers with longitudinal pumping at λ = 808 nm from one face of the active crystal. Estimates of thermal effects show that, using a Nd : YVO{sub 4} crystal (length 20 mm, diameter 3 mm, dopant concentration 0.27 at%) with two undoped ends and bidirectional diode pumping with a total power of 170 W, one can obtain an output power of ∼100 W in the TEM{sub 00} mode from one active element. (lasers)

  7. Single-mode, narrow-linewidth external cavity quantum cascade laser through optical feedback from a partial-reflector

    SciTech Connect

    Cendejas, Richard A.; Phillips, Mark C.; Myers, Tanya L.; Taubman, Matthew S.

    2010-11-30

    An external-cavity (EC) quantum cascade (QC) laser using optical feedback from a partial-reflector is reported. With this configuration, the otherwise multi-mode emission of a Fabry-Perot QC laser was made single-mode with optical output powers exceeding 40 mW. A mode-hop free tuning range of 2.46 cm-1 was achieved by synchronously tuning the EC length and QC laser current. The linewidth of the partial-reflector EC-QC laser was measured for integration times from 100 μs to 4 s, and compared to a distributed feedback QC laser. Linewidths as small as 480 kHz were recorded for the EC-QC laser

  8. Nonclassical Correlation Dynamics in a System of Mesoscopic Josephson Junction Coupled to Single-mode Optical Cavity

    NASA Astrophysics Data System (ADS)

    Xiang, Shao-Hua; Zhao, Yu-Jing; Zhu, Xi-Xiang; Song, Ke-Hui

    2015-08-01

    We investigate the time evolutions of the continuous-variable entanglement and Gaussian quantum discord in a system consisting of a mesoscopic Josephson junction coupled to a single-mode optical cavity field. We can obtain the time-dependent covariance matrix using known symplectic operation and local canonical transformations. We compare the dynamics of Gaussian quantum discord with that of entanglement. It is shown that the entanglement dynamics of two-mode squeezed thermal state is richer and undergoes three different features: periodical oscillation, sudden death and revival, and no-creation of entanglement, conditioned on the average number of thermal photons in each mode, whereas the Gaussian quantum discord can only exhibit a periodical oscillation behavior during the evolution.

  9. Imprinting single and dual mode initial perturbations in Rayleigh-Taylor instability experiments performed using magnetic levitation

    NASA Astrophysics Data System (ADS)

    Rosenblatt, Charles; Renoult, Marie-Charlotte; Ferjani, Sameh; Chen, Chia-Ling; Carlès, Pierre

    2011-11-01

    We have developed an experimental technique that uses magnetic levitation and paramagnetic fluids to control the initial interface shape of a Rayleigh-Taylor instability. It facilitates not only the stabilization of the static interface of a dense fluid (paramagnetic aqueous solution) above a less dense fluid (hexadecane), but also the modulation of its shape by introducing inhomogeneous magnetic fields. As an illustration of the technique, we will demonstrate our ability to imprint single-mode and dual-mode perturbations as initial conditions in the RT instability and show their development for various wavelengths. Results from experimental measurements of local and global metrics to describe the growing interface versus time (especially in the non-linear regime) will be discussed. This approach paves the way to a more general experimental exploration of multi-mode initial distributions.

  10. Analytical comparison of circular diaphragm based simple, single and double touch mode - MEMS capacitive pressure sensor

    NASA Astrophysics Data System (ADS)

    Jindal, Sumit Kumar; Raghuwanshi, Sanjeev Kumar

    2016-03-01

    In this paper a comparative study is done between normal capacitive pressure sensor, a touch mode capacitive pressure sensor and a double touch mode capacitive pressure sensor. The diaphragm in use is of circular shape. The theory and underlying equations has been described for the said devices and then simulations have been done for different performance parameters to understand the advantage of one over the other.

  11. Room temperature, single mode emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser

    SciTech Connect

    Pierściński, K. Pierścińska, D.; Pluska, M.; Gutowski, P.; Sankowska, I.; Karbownik, P.; Czerwinski, A.; Bugajski, M.

    2015-10-07

    Room temperature, single mode, pulsed emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser fabricated by focused ion beam processing is demonstrated and analyzed. The single mode emission is centered at 1059.4 cm{sup −1} (9.44 μm). A side mode suppression ratio of 43 dB was achieved. The laser exhibits a peak output power of 15 mW per facet at room temperature. The stable, single mode emission is observed within temperature tuning range, exhibiting shift at rate of 0.59 nm/K.

  12. Room temperature, single mode emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Pierściński, K.; Pierścińska, D.; Pluska, M.; Gutowski, P.; Sankowska, I.; Karbownik, P.; Czerwinski, A.; Bugajski, M.

    2015-10-01

    Room temperature, single mode, pulsed emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser fabricated by focused ion beam processing is demonstrated and analyzed. The single mode emission is centered at 1059.4 cm-1 (9.44 μm). A side mode suppression ratio of 43 dB was achieved. The laser exhibits a peak output power of 15 mW per facet at room temperature. The stable, single mode emission is observed within temperature tuning range, exhibiting shift at rate of 0.59 nm/K.

  13. Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres.

    PubMed

    Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

    2016-06-24

    Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices.

  14. Broadband single-mode waveguiding in two- and three-dimensional hybrid photonic crystals based on silicon inverse opals.

    PubMed

    Qiu, Gaoxin; Vynck, Kevin; Cassagne, David; Centeno, Emmanuel

    2007-03-19

    Hybrid 2D-3D heterostructures are a very promising way for waveguiding light in 3D photonic structures. Single-mode waveguiding of light has been demonstrated in heterostructures where a 2D photonic crystal consisting of a triangular lattice of silicon rods in air was intercalated between two silicon inverse opals. In this paper, we show that by using a graphite lattice of rods instead of a triangular one, it is possible to enlarge the maximal single-mode waveguiding bandwidth by more than 70 %, i.e. up to 129 nm centered on 1.55 mum. The sensibility to the 2D layer structure parameters is lower, offering enhanced experimental flexibility in the design of the structure.

  15. Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres

    PubMed Central

    Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

    2016-01-01

    Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices. PMID:27339700

  16. Single-mode oscillation of a diode-pumped Nd:YAG microchip laser at 1835 nm

    NASA Astrophysics Data System (ADS)

    Lan, Jinglong; Cui, Qin; Wang, Yi; Xu, Bin; Xu, Huiying; Cai, Zhiping

    2016-10-01

    Single-mode oscillation of a diode-pumped conventional Nd:YAG laser at 1835 nm is demonstrated, for the first time to our knowledge, in the form of microchip configuration. The achieved maximum output power reaches 189 mW with slope efficiency of about 5.5% with respect to absorbed pump power. The laser spectra are measured with linewidth less than 0.08 nm indicating a single longitudinal mode. The output laser beam is also measured to be near diffraction-limited with M2 factors of about 1.2 and 1.5 in x and y directions. Using a mechanical chopper with 50% duty cycle, the maximum output power is improved to 253 mW with slope efficiency of about 9.7%.

  17. Temperature stability of transit time delay for a single-mode fibre in a loose tube cable

    NASA Technical Reports Server (NTRS)

    Bergman, L. A.; Eng, S. T.; Johnston, A. R.

    1983-01-01

    The effect of temperature on the transit-time delay of a loose-tube-type single-mode optical-fiber cable is investigated experimentally. A 1058-m length of cable was placed loosely coiled in an oven and used to connect a 820-nm single-mode laser diode to a high-speed avalanche-photodiode detector feeding a vector voltmeter; the signal was provided by a high-stability frequency-synthesized generator. Measurements were made every 2 C from -50 to 60 C and compared to those obtained with a 200-m lacquered bare fiber. The phase change of both fibers varied with temperature at a positive slope of 6-7 ppm/C. This value is significantly better than those reported for other cable types, suggesting the application of loose-fiber cables to long-haul gigabit digital transmissions or precision time-base distribution for VLBI.

  18. Tm3+ and Tm(3+)-Ho3+ co-doped tungsten tellurite glass single mode fiber laser.

    PubMed

    Li, Kefeng; Zhang, Guang; Wang, Xin; Hu, Lili; Kuan, Peiwen; Chen, Danping; Wang, Meng

    2012-04-23

    We investigated the ~2 μm spectroscopic and lasing performance of Tm(3+) and Tm(3+)-Ho(3+) co-doped tungsten tellurite glass single mode fibers with a commercial 800 nm laser diode. The double cladding single mode (SM) fibers were fabricated by using rod-in-tube method. The propagation loss of the fiber was ~2.5 dB/m at 1310 nm. The spectroscopic properties of the fibers were analyzed. A 494 mW laser operating at ~1.9 μm was achieved in a Tm(3+) doped 20 cm long fiber, the slope efficiency was 26%, and the laser beam quality factor M(2) was 1.09. A 35 mW ~2.1 μm laser output was also demonstrated in a 7 cm long of Tm(3+)-Ho(3+) co-doped tungsten tellurite SM fiber.

  19. Compact free-space optical terminal for multi-gigabit signal transmissions with a single-mode fiber

    NASA Astrophysics Data System (ADS)

    Arimoto, Yoshinori

    2009-02-01

    This paper shows the design and the performance of a new free-space optical communication terminal including the results of the indoor and outdoor demonstration experiments in a short link distance. To provide flexible and high-speed connectivity to the terrestrial free-space optical communications, a new compact laser communication terminal has been developed at NICT. The terminal has a feature to connect the free-space laser beam directly to single mode fiber by using a special fiber coupler to focus the free-space laser beam and couple it into the single mode fiber, fast and accurate fine tracking system and a small refractive-type telescope with diffraction limited performance. The bandwidth of the fine tracking system is more than 5 kHz using an off-the-shelf miniature Galvano mirror actuator and an analog PID controller.

  20. Single mode step-index polymer optical fiber for humidity insensitive high temperature fiber Bragg grating sensors.

    PubMed

    Woyessa, Getinet; Fasano, Andrea; Stefani, Alessio; Markos, Christos; Nielsen, Kristian; Rasmussen, Henrik K; Bang, Ole

    2016-01-25

    We have fabricated the first single-mode step-index and humidity insensitive polymer optical fiber operating in the 850 nm wavelength ranges. The step-index preform is fabricated using injection molding, which is an efficient method for cost effective, flexible and fast preparation of the fiber preform. The fabricated single-mode step-index (SI) polymer optical fiber (POF) has a 4.8µm core made from TOPAS grade 5013S-04 with a glass transition temperature of 134°C and a 150 µm cladding made from ZEONEX grade 480R with a glass transition temperature of 138°C. The key advantages of the proposed SIPOF are low water absorption, high operating temperature and chemical inertness to acids and bases and many polar solvents as compared to the conventional poly-methyl-methacrylate (PMMA) and polystyrene based POFs. In addition, the fiber Bragg grating writing time is short compared to microstructured POFs.

  1. Single and two-mode mechanical squeezing of an optically levitated nanodiamond via dressed-state coherence

    NASA Astrophysics Data System (ADS)

    Ge, Wenchao; Bhattacharya, M.

    2016-10-01

    Nonclassical states of macroscopic objects are promising for ultrasensitive metrology as well as testing quantum mechanics. In this work, we investigate dissipative mechanical quantum state engineering in an optically levitated nanodiamond. First, we study single-mode mechanical squeezed states by magnetically coupling the mechanical motion to a dressed three-level system provided by a nitrogen-vacancy center in the nanoparticle. Quantum coherence between the dressed levels is created via microwave fields to induce a two-phonon transition, which results in mechanical squeezing. Remarkably, we find that in ultrahigh vacuum quantum squeezing is achievable at room temperature with feedback cooling. For moderate vacuum, quantum squeezing is possible with cryogenic temperature. Second, we present a setup for two mechanical modes coupled to the dressed three levels, which results in two-mode squeezing analogous to the mechanism of the single-mode case. In contrast to previous works, our study provides a deterministic method for engineering macroscopic squeezed states without the requirement for a cavity.

  2. A patch-array antenna single-mode low electrical dissipation continuous wave terahertz quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Bosco, L.; Bonzon, C.; Ohtani, K.; Justen, M.; Beck, M.; Faist, J.

    2016-11-01

    We introduce a double metal terahertz quantum cascade laser meant for astrophysical heterodyne measurements. The laser ridge is embedded in benzocyclobutene, and the device exhibits single mode, continuous wave operation around 4.745 THz with a peak power of almost 1.8 mW at 10 K and a power consumption of ≈1.6 W. Moreover, thanks to the integration of a top metal contact with a patch array antenna for light out-coupling the beam of the emitted light has a low-divergence single-lobe profile and an FWHM of ≈30°.

  3. Empirical modeling of Single-Event Upset (SEU) in NMOS depletion-mode-load static RAM (SRAM) chips

    NASA Technical Reports Server (NTRS)

    Zoutendyk, J. A.; Smith, L. S.; Soli, G. A.; Smith, S. L.; Atwood, G. E.

    1986-01-01

    A detailed experimental investigation of single-event upset (SEU) in static RAM (SRAM) chips fabricated using a family of high-performance NMOS (HMOS) depletion-mode-load process technologies, has been done. Empirical SEU models have been developed with the aid of heavy-ion data obtained with a three-stage tandem van de Graaff accelerator. The results of this work demonstrate a method by which SEU may be empirically modeled in NMOS integrated circuits.

  4. Catastrophic optical degradation of the output facet of high-power single-transverse-mode diode lasers. 1. Physical model

    SciTech Connect

    Miftakhutdinov, D R; Bogatov, Alexandr P; Drakin, A E

    2010-09-10

    The physical model of catastrophic optical degradation (COD) of the output facet of high-power single- transverse-mode diode lasers is developed. The model excels other models both in completeness of the physical analysis of the processes leading to COD and in allowance for design feature of lasers used to increase the COD threshold - protective coating of the output facet and current limitations near it. (lasers)

  5. Single-mode optical fiber design with wide-band ultra low bending-loss for FTTH application.

    PubMed

    Watekar, Pramod R; Ju, Seongmin; Han, Won-Taek

    2008-01-21

    We propose a new design of a single-mode optical fiber (SMF) which exhibits ultra low bend sensitivity over a wide communication band (1.3 microm to 1.65 microm). A five-cladding fiber structure has been proposed to minimize the bending loss, estimated to be as low as 4.4x10(-10) dB/turn for the bend radius of 10 mm.

  6. Laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) by single-mode fiber laser irradiation

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Kawaguchi, Yoshizo; Sato, Tadatake; Narazaki, Aiko; Kurosaki, Ryozo; Muramatsu, Mayu; Harada, Yoshihisa; Anzai, Kenji; Aoyama, Mitsuaki; Matsushita, Masafumi; Furukawa, Koichi; Nishino, Michiteru; Fujisaki, Akira; Miyato, Taizo; Kayahara, Takashi

    2014-03-01

    We report on the laser cutting of carbon fiber reinforced thermo-plastics (CFRTP) with a cw IR fiber laser (single-mode fiber laser, average power: 350 W). CFRTP is a high strength composite material with a lightweight, and is increasingly being used various applications. A well-defined cutting of CFRTP which were free of debris and thermal-damages around the grooves, were performed by the laser irradiation with a fast beam galvanometer scanning on a multiple-scanpass method.

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

    SciTech Connect

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

    2010-11-15

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

  8. Fabrication of low-loss, single-mode-channel waveguide with DNA-CTMA biopolymer by multistep processing technology.

    PubMed

    Zhou, Jun; Wang, Zhen Yong; Yang, Xin; Wong, C-Y; Pun, Edwin Y B

    2010-05-15

    A multistep processing and reactive ion etching technique has been developed to fabricate optical channel waveguides based on deoxyribonucleic acid-cetyltrimethylammonium biopolymer material. The channel waveguides exhibit excellent single-mode output and high confinement of light because of the sharp waveguide profile with very smooth surfaces and vertical sidewalls. The measurement results show that these channel waveguides have low propagation losses and small polarization dependent losses at 633, 1310, and 1550 nm wavelengths.

  9. Supercontinuum and four-wave mixing with Q-switched pulses in endlessly single-mode photonic crystal fibres.

    PubMed

    Wadsworth, W; Joly, N; Knight, J; Birks, T; Biancalana, F; Russell, P

    2004-01-26

    Photonic crystal fibres exhibiting endlessly single-mode operation and dispersion zero in the range 1040 to 1100 nm are demonstrated. A sub-ns pump source at 1064 nm generates a parametric output at 732 nm with an efficiency of 35%, or parametric gain of 55 dB at 1315 nm. A broad, flat supercontinuum extending from 500 nm to beyond 1750 nm is also demonstrated using the same pump source.

  10. Single Mode Theory for Impedance Eduction in Large-Scale Ducts with Grazing Flow

    NASA Technical Reports Server (NTRS)

    Watson, Willie R.; Gerhold, Carl H.; Jones, Michael G.; June, Jason C.

    2014-01-01

    An impedance eduction theory for a rigid wall duct containing an acoustic liner with an unknown impedance and uniform grazing flow is presented. The unique features of the theory are: 1) non-planar waves propagate in the hard wall sections of the duct, 2) input data consist solely of complex acoustic pressures acquired on a wall adjacent to the liner, and 3) multiple higher-order modes may exist in the direction perpendicular to the liner and the opposite rigid wall. The approach is to first measure the axial propagation constant of a dominant higher-order mode in the liner sample section. This axial propagation constant is then used in conjunction with a closed-form solution to a reduced form of the convected Helmholtz equation and the wall impedance boundary condition to educe the liner impedance. The theory is validated on a conventional liner whose impedance spectrum is educed in two flow ducts with different cross sections. For the frequencies and Mach numbers of interest, no higher-order modes propagate in the hard wall sections of the smaller duct. A benchmark method is used to educe the impedance spectrum in this duct. A dominant higher-order vertical mode propagates in the larger duct for similar test conditions, and the current theory is applied to educe the impedance spectrum. Results show that when the theory is applied to data acquired in the larger duct with a dominant higher-order vertical mode, the same impedance spectra is educed as that obtained in the small duct where only the plane wave mode is present and the benchmark method is used. This result holds for each higher-order vertical mode that is considered.

  11. A single source microwave photonic filter using a novel single-mode fiber to multimode fiber coupling technique.

    PubMed

    Chang, John; Fok, Mable P; Meister, James; Prucnal, Paul R

    2013-03-11

    In this paper we present a fully tunable and reconfigurable single-laser multi-tap microwave photonic FIR filter that utilizes a special SM-to-MM combiner to sum the taps. The filter requires only a single laser source for all the taps and a passive component, a SM-to-MM combiner, for incoherent summing of signal. The SM-to-MM combiner does not produce optical interference during signal merging and is phase-insensitive. We experimentally demonstrate an eight-tap filter with both positive and negative programmable coefficients with excellent correspondence between predicted and measured values. The magnitude response shows a clean and accurate function across the entire bandwidth, and proves successful operation of the FIR filter using a SM-to-MM combiner.

  12. On-chip coherent combining of angled-grating diode lasers toward bar-scale single-mode lasers.

    PubMed

    Zhao, Yunsong; Zhu, Lin

    2012-03-12

    Single mode operation of broad-area diode lasers, which is the key to obtain high power, high brightness sources, is difficult due to highly nonlinear materials and strong coupling between gain and index. Conventional broad-area lasers usually operate with multiple modes and have poor beam quality. Laser bars usually consist of incoherently combined broad-area single emitters placed side by side. In this article, we have demonstrated a novel integrated laser architecture in which Bragg diffraction is used to realize simultaneous modal control and coherent combining of broad-area diode lasers. Our experimental results show that two 100 μm wide, 1.3mm long InP broad-area lasers provide near-diffraction-limited output beam and are coherently combined at the same time without any external optical components. Furthermore, our design can be expanded to a coherently combined broad-area laser array that turns a laser bar into a coherent single mode laser with diffraction-limited beam quality.

  13. Ultra-high negative dispersion compensating square lattice based single mode photonic crystal fiber with high nonlinearity

    NASA Astrophysics Data System (ADS)

    Islam, Md. Ibadul; Khatun, Maksuda; Ahmed, Kawsar

    2017-02-01

    This paper presents dispersion tailoring of photonic crystal fibers creating artificial defect along one of the regular square axes. A finite element method (FEM) has been enforced for numerical investigation of several guiding properties of the PCF covering a broad wavelength range about 1340-1640 nm over the telecommunication windows. According to simulation, the proposed PCF has obtained a strictly single-mode fiber, which has an ultra-high negative dispersion of about -584.60 to -2337.60 ps/(nm-km) and also possible to cover the highest nonlinearity order of 131.91 W-1 km-1 under the operating wavelength. Moreover, the proposed PCF structure experimentally focuses on higher nonlinear coefficient, which successfully compensates the chromatic dispersion of standard single mode in entire band of interest and greatly applicable to the optical transmission system. Additionally, the single mode behavior of S-PCF is explicated by employing V parameter. In our dispersion sensitive analysis, this fiber is significantly more robust due to successfully achieve ultra-high negative dispersion, which gains more promiscuous compared to the prior best results.

  14. Highly Tm3+ doped germanate glass and its single mode fiber for 2.0 μm laser

    PubMed Central

    Wen, Xin; Tang, Guowu; Yang, Qi; Chen, Xiaodong; Qian, Qi; Zhang, Qinyuan; Yang, Zhongmin

    2016-01-01

    Highly Tm3+ doped optical fibers are urgently desirable for 2.0 μm compact single-frequency fiber laser and high-repetition-rate mode-locked fiber laser. Here, we systematically investigated the optical parameters, energy transfer processes and thermal properties of Tm3+ doped barium gallo-germanate (BGG) glasses. Highly Tm3+ doped BGG glass single mode (SM) fibers were fabricated by the rod-in-tube technique. The Tm3+ doping concentration reaches 7.6 × 1020 ions/cm3, being the reported highest level in Tm3+ doped BGG SM fibers. Using ultra short (1.6 cm) as-drawn highly Tm3+ doped BGG SM fiber, a single-frequency fiber laser at 1.95 μm has been demonstrated with a maximum output power of 35 mW when in-band pumped by a home-made 1568 nm fiber laser. Additionally, a multilongitudinal-mode fiber laser at 1.95 μm has also been achieved in a 10 cm long as-drawn active fiber, yielding a maximum laser output power of 165 mW and a slope efficiency of 17%. The results confirm that the as-drawn highly Tm3+ doped BGG SM fibers are promising in applications that require high gain and high power from a short piece of active optical fiber. PMID:26828920

  15. Research on respiratory motion correction method based on liver contrast-enhanced ultrasound images of single mode

    NASA Astrophysics Data System (ADS)

    Zhang, Ji; Li, Tao; Zheng, Shiqiang; Li, Yiyong

    2015-03-01

    To reduce the effects of respiratory motion in the quantitative analysis based on liver contrast-enhanced ultrasound (CEUS) image sequencesof single mode. The image gating method and the iterative registration method using model image were adopted to register liver contrast-enhanced ultrasound image sequences of single mode. The feasibility of the proposed respiratory motion correction method was explored preliminarily using 10 hepatocellular carcinomas CEUS cases. The positions of the lesions in the time series of 2D ultrasound images after correction were visually evaluated. Before and after correction, the quality of the weighted sum of transit time (WSTT) parametric images were also compared, in terms of the accuracy and spatial resolution. For the corrected and uncorrected sequences, their mean deviation values (mDVs) of time-intensity curve (TIC) fitting derived from CEUS sequences were measured. After the correction, the positions of the lesions in the time series of 2D ultrasound images were almost invariant. In contrast, the lesions in the uncorrected images all shifted noticeably. The quality of the WSTT parametric maps derived from liver CEUS image sequences were improved more greatly. Moreover, the mDVs of TIC fitting derived from CEUS sequences after the correction decreased by an average of 48.48+/-42.15. The proposed correction method could improve the accuracy of quantitative analysis based on liver CEUS image sequences of single mode, which would help in enhancing the differential diagnosis efficiency of liver tumors.

  16. Highly Tm3+ doped germanate glass and its single mode fiber for 2.0 μm laser

    NASA Astrophysics Data System (ADS)

    Wen, Xin; Tang, Guowu; Yang, Qi; Chen, Xiaodong; Qian, Qi; Zhang, Qinyuan; Yang, Zhongmin

    2016-02-01

    Highly Tm3+ doped optical fibers are urgently desirable for 2.0 μm compact single-frequency fiber laser and high-repetition-rate mode-locked fiber laser. Here, we systematically investigated the optical parameters, energy transfer processes and thermal properties of Tm3+ doped barium gallo-germanate (BGG) glasses. Highly Tm3+ doped BGG glass single mode (SM) fibers were fabricated by the rod-in-tube technique. The Tm3+ doping concentration reaches 7.6 × 1020 ions/cm3, being the reported highest level in Tm3+ doped BGG SM fibers. Using ultra short (1.6 cm) as-drawn highly Tm3+ doped BGG SM fiber, a single-frequency fiber laser at 1.95 μm has been demonstrated with a maximum output power of 35 mW when in-band pumped by a home-made 1568 nm fiber laser. Additionally, a multilongitudinal-mode fiber laser at 1.95 μm has also been achieved in a 10 cm long as-drawn active fiber, yielding a maximum laser output power of 165 mW and a slope efficiency of 17%. The results confirm that the as-drawn highly Tm3+ doped BGG SM fibers are promising in applications that require high gain and high power from a short piece of active optical fiber.

  17. Square-core single-mode-fiber (SC-SMF) with high bending tolerance for data center networks

    NASA Astrophysics Data System (ADS)

    Chow, C. W.; Huang, S. P.; Yeh, C. H.; Sung, J. Y.; Liu, P. F.; Chou, Gary; Pan, C.-L.

    2015-08-01

    Square-core optical fiber has been proposed recently for high optical power delivery in industrial processing tools with core size larger than 400×400 μm2. In this work, we first study the possibility of significantly reducing the core side to single-mode condition (i.e. 9×9 μm2) at optical communication wavelength. In the proposed square-core single-mode-fiber (SC-SMF), high bandwidth-distance product and low bending loss are achieved. We also discuss the fabrication of the SC-SMF. After this, the bending losses of the SC-SMF and standard single mode fiber (SSMF) are analyzed and compared. Finally, 10 Gb/s signal transmission using conventional on-off keying (OOK) and orthogonal frequency division multiplexing (OFDM) passing through 200 m, 500 m and 1 km SC-SMFs are performed. Negligible power penalty is observed. We believe that this can be another choice of high bending tolerance fiber which is simple to manufacture.

  18. “MODAL NOISE” IN SINGLE-MODE FIBERS: A CAUTIONARY NOTE FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

    SciTech Connect

    Halverson, Samuel; Roy, Arpita; Mahadevan, Suvrath; Schwab, Christian

    2015-12-01

    Exploring the use of single-mode fibers (SMFs) in high precision Doppler spectrometers has become increasingly attractive since the advent of diffraction-limited adaptive optics systems on large-aperture telescopes. Spectrometers fed with these fibers can be made significantly smaller than typical “seeing-limited” instruments, greatly reducing cost and overall complexity. Importantly, classical mode interference and speckle issues associated with multi-mode fibers, also known as “modal noise,” are mitigated when using SMFs, which also provide perfect radial and azimuthal image scrambling. However, SMFs do support multiple polarization modes, an issue that is generally ignored for larger-core fibers given the large number of propagation modes. Since diffraction gratings used in most high resolution astronomical instruments have dispersive properties that are sensitive to incident polarization changes, any birefringence variations in the fiber can cause variations in the efficiency profile, degrading illumination stability. Here we present a cautionary note outlining how the polarization properties of SMFs can affect the radial velocity (RV) measurement precision of high resolution spectrographs. This work is immediately relevant to the rapidly expanding field of diffraction-limited, extreme precision RV spectrographs that are currently being designed and built by a number of groups.

  19. Continuous-variable entanglement and two-mode squeezing in a single-atom Raman laser

    NASA Astrophysics Data System (ADS)

    Sete, Eyob A.; Ooi, C. H. Raymond

    2012-06-01

    The quantum statistical properties of light emitted by a two-photon double Raman laser is investigated. Using the master equation derived in the good-cavity limit, we study the squeezing and entanglement properties of the cavity field. It turns out that the cavity radiation exhibits two-mode squeezing and entanglement in the transient as well as steady state regime for realizable parameters. We establish a connection between two-mode squeezing and entanglement that gives insight into the physical origin of these quantum features. We also discuss the interplay between the laser detuning and amplitude in modifying the properties of the cavity field.

  20. High power single-mode fiber laser and its application to metal and non-metal materials

    NASA Astrophysics Data System (ADS)

    Miyato, Taizo; Kayahara, Takashi; Fujisaki, Akira; Furukawa, Koichi; Matsushita, Masafumi; Muramatsu, Mayu; Harada, Yoshihisa; Niino, Hiroyuki

    2014-02-01

    The power level of Yb doped fiber lasers which operate in continuous wave mode has been increasing in recent years and various kinds of applications using high power single-mode fiber lasers that oscillate in 1microns wavelength range were reported. Single-mode fiber laser that has excellent beam quality of less than 1.1 M2 value with kW class average power can be focused to tens of microns diameters and its optical power density at the focus point is more than 1×108 W/cm2. In this power density range, the interaction between 1microns laser light and matter, not only metal materials but non-metal materials, is completely different from that of lower level. The power density initiates laser processing of copper that has relatively high reflectivity at this wavelength range among metals and alumina base plate with over 90% reflectivity. Other interesting material which can be processed by this energy level is carbon fiber reinforced plastics (CFRP). On the other hand, for industrial application and further processing investigation, modulation speed is one of the most important factors because that relates to processing speed and precise control of laser energy input to a material. In this paper, we report on the power dependence of some material processing of copper wafer welding, alumina base plate scribing, and CFRP cutting using single-mode fiber laser which is capable of over 1kW peak power operation and has rapid switching time below 5 micro seconds.

  1. Control Optimization for a Dual-Mode Single-State Nuclear Shuttle,

    DTIC Science & Technology

    1980-01-01

    velocity. Thus a comparison between mixed-mode propulsion and straight hydrogen propulsion is warranted here. Using the same input parameters as in...only slightly improves the performance of a shuttle above pure hydrogen propulsion . This slight improvement would hardly justify the additional cost and

  2. String Pendulum Dynamics. Control in the Single-Axis Azimuth-Free Gyro Mode

    NASA Astrophysics Data System (ADS)

    Sukhoruchkin, D. A.

    2014-03-01

    An implementation of a generalized Foucault pendulum, where the basic mechanical elements are a massive solid ball and two weightless strings, is considered. A two-dimensional electromechanical model of the gyro is constructed. Channels for inertial data acquisition and for vibration control are formed. The stability of the reference manifold for the chosen operation mode is shown.

  3. Three-Dimensional Single-Mode Nonlinear Ablative Rayleigh-Taylor Instability

    NASA Astrophysics Data System (ADS)

    Yan, R.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2015-11-01

    The nonlinear evolution of the ablative Rayleigh-Taylor (ART) instability is studied in three dimensions for conditions relevant to inertial confinement fusion targets. The simulations are performed using our newly developed code ART3D and an astrophysical code AstroBEAR. The laser ablation can suppress the growth of the short-wavelength modes in the linear phase but may enhance their growth in the nonlinear phase because of the vortex-acceleration mechanism. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the bubble velocity grows faster than predicted in the classical 3-D theory. When compared to 2-D results, 3-D short-wavelength bubbles grow faster and do not reach saturation. The unbounded 3-D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes into the ablated plasma filling the bubble volume. A density plateau is observed inside a nonlinear ART bubble and the plateau density is higher for shorter-wavelength modes. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  4. Measurements of the evaporation and hygroscopic response of single fine-mode aerosol particles using a Bessel beam optical trap.

    PubMed

    Cotterell, Michael I; Mason, Bernard J; Carruthers, Antonia E; Walker, Jim S; Orr-Ewing, Andrew J; Reid, Jonathan P

    2014-02-07

    A single horizontally-propagating zeroth order Bessel laser beam with a counter-propagating gas flow was used to confine single fine-mode aerosol particles over extended periods of time, during which process measurements were performed. Particle sizes were measured by the analysis of the angular variation of light scattered at 532 nm by a particle in the Bessel beam, using either a probe beam at 405 nm or 633 nm. The vapour pressures of glycerol and 1,2,6-hexanetriol particles were determined to be 7.5 ± 2.6 mPa and 0.20 ± 0.02 mPa respectively. The lower volatility of hexanetriol allowed better definition of the trapping environment relative humidity profile over the measurement time period, thus higher precision measurements were obtained compared to those for glycerol. The size evolution of a hexanetriol particle, as well as its refractive index at wavelengths 532 nm and 405 nm, were determined by modelling its position along the Bessel beam propagation length while collecting phase functions with the 405 nm probe beam. Measurements of the hygroscopic growth of sodium chloride and ammonium sulfate have been performed on particles as small as 350 nm in radius, with growth curves well described by widely used equilibrium state models. These are the smallest particles for which single-particle hygroscopicity has been measured and represent the first measurements of hygroscopicity on fine mode and near-accumulation mode aerosols, the size regimes bearing the most atmospheric relevance in terms of loading, light extinction and scattering. Finally, the technique is contrasted with other single particle and ensemble methods, and limitations are assessed.

  5. 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.

  6. Transonic single-mode flutter and buffet of a low aspect ratio wing having a subsonic airfoil shape

    NASA Technical Reports Server (NTRS)

    Erickson, L. L.

    1974-01-01

    Transonic flutter and buffet results obtained from wind-tunnel tests of a low aspect ratio semispan wing model are presented. The tests were conducted to investigate potential transonic aeroelastic problems of vehicles having subsonic airfoil sections. The model employed NACA 00XX-64 airfoil sections in the streamwise direction and had a 14 deg leading edge sweep angle. Aspect ratio, and average thickness were 4.0, 0.35, and 8 percent, respectively. The model was tested at Mach numbers from 0.6 to 0.95 at angles of attack from 0 deg to 15 deg. Two zero lift flutter conditions were found that involved essentially single normal mode vibrations. With boundary layer trips on the model, flutter occurred in a narrow Mach number range centered at about Mach 0.90. The frequency and motion of this flutter were like that of the first normal mode vibration. With the trips removed flutter occurred at a slightly high Mach number but in a mode strongly resembling that of the second normal mode.

  7. Design and realization of a side-polished single-mode fiber optic high-sensitive temperature sensor

    NASA Astrophysics Data System (ADS)

    Nagaraju, B.; Varshney, R. K.; Pal, B. P.; Singh, A.; Monnom, G.; Dussardier, B.

    2008-11-01

    A high sensitive temperature sensor based on evanescent field coupling between a side-polished fiber half-coupler (SPFHC) and a thermo-optic multimode overlay waveguide (MMOW) is designed and demonstrated. Such a structure essentially functions as an asymmetric directional coupler with a band-stop characteristic attributable to the wavelengthdependent resonant coupling between the mode of the SPFHC and one or more modes of the MMOW. A slight change in temperature leads to a significant shift in the phase resonance-coupling wavelength ( λr ) between the MMOW and SPFHC λr, which is easily measurable. The wavelength sensitivity of the device is measured to be ~ 5.3 nm/°C within the measurement range of 26-70°C this sensitivity is more than 5 times higher compared to earlier reported temperature sensors of this kind. The SPFHC was fabricated by selective polishing of the cladding from one side of a bent telecommunication standard single-mode fiber and the MMOW was formed on top of the SPFHC through spin coating. A semi- numerical rigorous normal mode analysis was employed at the design stage by including the curvature effect of the fiber lay in the half-coupler block and the resultant z-dependent evanescent coupling mechanism. An excellent agreement between theoretical and experimental results is found.

  8. Enhanced Third Harmonic Generation in Single Germanium Nanodisks Excited at the Anapole Mode.

    PubMed

    Grinblat, Gustavo; Li, Yi; Nielsen, Michael P; Oulton, Rupert F; Maier, Stefan A

    2016-07-13

    We present an all-dielectric germanium nanosystem exhibiting a strong third order nonlinear response and efficient third harmonic generation in the optical regime. A thin germanium nanodisk shows a pronounced valley in its scattering cross section at the dark anapole mode, while the electric field energy inside the disk is maximized due to high confinement within the dielectric. We investigate the dependence of the third harmonic signal on disk size and pump wavelength to reveal the nature of the anapole mode. Each germanium nanodisk generates a high effective third order susceptibility of χ((3)) = 4.3 × 10(-9) esu, corresponding to an associated third harmonic conversion efficiency of 0.0001% at an excitation wavelength of 1650 nm, which is 4 orders of magnitude greater than the case of an unstructured germanium reference film. Furthermore, the nonlinear conversion via the anapole mode outperforms that via the radiative dipolar resonances by about 1 order of magnitude, which is consistent with our numerical simulations. These findings open new possibilities for the optimization of upconversion processes on the nanoscale through the appropriate engineering of suitable dielectric materials.

  9. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    NASA Astrophysics Data System (ADS)

    Kumar, Shailesh; Lausen, Jens L.; Garcia-Ortiz, Cesar E.; Andersen, Sebastian K. H.; Roberts, Alexander S.; Radko, Ilya P.; Smith, Cameron L. C.; Kristensen, Anders; Bozhevolnyi, Sergey I.

    2016-02-01

    Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes.

  10. Label free imaging system for measuring blood flow speeds using a single multi-mode optical fiber (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sigal, Iliya; Caravaca Aguirre, Antonio M.; Gad, Raanan; Piestun, Rafael; Levi, Ofer

    2016-03-01

    We demonstrate a single multi-mode fiber-based micro-endoscope for measuring blood flow speeds. We use the transmission-matrix wavefront shaping approach to calibrate the multi-mode fiber and raster-scan a focal spot across the distal fiber facet, imaging the cross-polarized back-reflected light at the proximal facet using a camera. This setup allows assessment of the backscattered photon statistics: by computing the mean speckle contrast values across the proximal fiber facet we show that spatially-resolved flow speed maps can be inferred by selecting an appropriate camera integration time. The proposed system is promising for minimally-invasive studies of neurovascular coupling in deep brain structures.

  11. Modulational instability and localized modes in Heisenberg ferromagnetic chains with single-ion easy-axis anisotropy

    NASA Astrophysics Data System (ADS)

    Tang, Bing; Li, Guang-Ling; Fu, Mei

    2017-03-01

    A semiclassical theoretical study on the property of the modulational instability of corresponding linear spin-waves and the presence of nonlinear localized excitations in a discrete quantum ferromagnetic spin chain with single-ion easy-axis anisotropy is reported. We consider the Glauber coherent-state representation combined with the Dyson-Maleev transformation for local spin operators as the basic representation of the system, and derive the equation of motion by means of the Ehrenfest theorem. Using a modulational instability analysis of plane waves, we predict the existence regions of bright envelope solitons and intrinsic localized spin-wave modes. Besides, with the help of a semidiscrete multi-scale method, we obtain analytical solutions for the bright envelope soliton and intrinsic localized spin-wave mode. Moreover, we analyze their existence conditions, which agree with the results of modulational instability analysis.

  12. Single-polarization noise-like pulse generation from a hybrid mode-locked thulium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Yan, Feng-Ping; Feng, Ting; Zhang, Lu-Na; Bai, Zhuo-Ya; Zhou, Hong; Hou, Yafei; Zhang, Ning

    2017-04-01

    A hybrid mode-locked thulium-doped fiber laser incorporating a nonlinear optical loop mirror and a nonlinear polarization rotation effect is proposed in the 2 μm band for the first time. By adjusting two polarization controllers, a stable single-polarization noise-like (SPNL) pulse operation is obtained. The SPNL pulse could work steadily for at least 400 min. At a launched pump power of 3.52 W, the hybrid mode-locked SPNL pulse centers at 2007 nm with an optical full width at half maximum of 20 nm, a polarization extinction ratio of 26.3 dB, a coherence spike width of 258 fs and a pulse energy of 42.11 nJ, respectively.

  13. Optical horn antennas for efficiently transferring photons from a quantum emitter to a single-mode optical fiber.

    PubMed

    Grosjean, T; Mivelle, M; Burr, G W; Baida, F I

    2013-01-28

    We theoretically demonstrate highly efficient optical coupling between a single quantum emitter and a monomode optical fiber over remarkably broad spectral ranges by extending the concept of horn antenna to optics. The optical horn antenna directs the radiation from the emitter toward the optical fiber and efficiently phase-matches the photon emission with the fiber mode. Numerical results show that an optical horn antenna can funnel up to 85% of the radiation from a dipolar source within an emission cone semi-angle as small as 7 degrees (antenna directivity of 300). It is also shown that 50% of the emitted power from the dipolar source can be collected and coupled to an SMF-28 fiber mode over spectral ranges larger than 1000 nm, with a maximum energy transfer reaching 70 %. This approach may open new perspectives in quantum optics and sensing.

  14. Dynamic operation of optical fibres beyond the single-mode regime facilitates the orientation of biological cells

    PubMed Central

    Kreysing, Moritz; Ott, Dino; Schmidberger, Michael J.; Otto, Oliver; Schürmann, Mirjam; Martín-Badosa, Estela; Whyte, Graeme; Guck, Jochen

    2014-01-01

    The classical purpose of optical fibres is delivery of either optical power, as for welding, or temporal information, as for telecommunication. Maximum performance in both cases is provided by the use of single-mode optical fibres. However, transmitting spatial information, which necessitates higher-order modes, is difficult because their dispersion relation leads to dephasing and a deterioration of the intensity distribution with propagation distance. Here we consciously exploit the fundamental cause of the beam deterioration—the dispersion relation of the underlying vectorial electromagnetic modes—by their selective excitation using adaptive optics. This allows us to produce output beams of high modal purity, which are well defined in three dimensions. The output beam distribution is even robust against significant bending of the fibre. The utility of this approach is exemplified by the controlled rotational manipulation of live cells in a dual-beam fibre-optical trap integrated into a modular lab-on-chip system. PMID:25410595

  15. Simple dispersion estimate for single-section quantum-dash and quantum-dot mode-locked laser diodes.

    PubMed

    O Duill, Sean P; Murdoch, Stuart G; Watts, Regan T; Rosales, Ricardo; Ramdane, Abderrahim; Landais, Pascal; Barry, Liam P

    2016-12-15

    The optical outputs of single-section quantum-dash and quantum-dot mode-locked lasers (MLLs) are well known to exhibit strong group velocity dispersion. Based on careful measurements of the spectral phase of the pulses from these MLLs, we confirm that the difference in group delay between the modes at either end of the MLL spectrum equals the cavity round-trip time. This observation allows us to deduce an empirical formula relating the accumulated dispersion of the output pulse to the spectral extent and free-spectral range of the MLL. We find excellent agreement with previously reported dispersion measurements of both quantum-dash and quantum-dot MLLs over a wide range of operating conditions.

  16. Dynamic operation of optical fibres beyond the single-mode regime facilitates the orientation of biological cells

    NASA Astrophysics Data System (ADS)

    Kreysing, Moritz; Ott, Dino; Schmidberger, Michael J.; Otto, Oliver; Schürmann, Mirjam; Martín-Badosa, Estela; Whyte, Graeme; Guck, Jochen

    2014-11-01

    The classical purpose of optical fibres is delivery of either optical power, as for welding, or temporal information, as for telecommunication. Maximum performance in both cases is provided by the use of single-mode optical fibres. However, transmitting spatial information, which necessitates higher-order modes, is difficult because their dispersion relation leads to dephasing and a deterioration of the intensity distribution with propagation distance. Here we consciously exploit the fundamental cause of the beam deterioration—the dispersion relation of the underlying vectorial electromagnetic modes—by their selective excitation using adaptive optics. This allows us to produce output beams of high modal purity, which are well defined in three dimensions. The output beam distribution is even robust against significant bending of the fibre. The utility of this approach is exemplified by the controlled rotational manipulation of live cells in a dual-beam fibre-optical trap integrated into a modular lab-on-chip system.

  17. InGaAsP/InP laser development for single-mode, high-data-rate communications

    NASA Technical Reports Server (NTRS)

    Ladany, I.; Levin, E. R.; Magee, C. W.; Smith, R. T.

    1981-01-01

    Materials studies as well as general and specific device development were carried out in the InGaAsP system. A comparison was made of three standard methods of evaluating substrate quality by means of dislocation studies. A cause of reduced yield of good wafers, the pullover of melt from one bin to the next, has been analyzed. Difficulties with reproducible zinc acceptor doping have been traced to segregation of zinc in the In/Zn alloy used for the doping source. Using EBIC measurments, the pn junction was shown to drift in location depending on factors not always under control. An analysis of contact structures by SIMS showed that the depth to which the sintered Au/Zn contact penetrates into the structure is typically 0.13 microns, or well within the cap layer and out of the p-type cladding and thus not deleterious to laser prformance. The problem of single-mode laser development was investigated and it was shown to be related to the growth habit over four different possible substrate configurations. The fabrication of constricted double heterojunctions, mesa stripe buried heterostructures, and buried heterostructures was discussed, and measurements were presented on the device properties of single-mode buried heterostructure lasers. Results include single spectral line emission at 3 mW and a threshold current of 60 mA.

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

    SciTech Connect

    Zheng, Mei C. Gmachl, Claire F.; Liu, Peter Q.; Wang, Xiaojun; Fan, Jen-Yu; Troccoli, Mariano

    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.

  19. Sliding-mode control of single input multiple output DC-DC converter

    NASA Astrophysics Data System (ADS)

    Zhang, Libo; Sun, Yihan; Luo, Tiejian; Wan, Qiyang

    2016-10-01

    Various voltage levels are required in the vehicle mounted power system. A conventional solution is to utilize an independent multiple output DC-DC converter whose cost is high and control scheme is complicated. In this paper, we design a novel SIMO DC-DC converter with sliding mode controller. The proposed converter can boost the voltage of a low-voltage input power source to a controllable high-voltage DC bus and middle-voltage output terminals, which endow the converter with characteristics of simple structure, low cost, and convenient control. In addition, the sliding mode control (SMC) technique applied in our converter can enhance the performances of a certain SIMO DC-DC converter topology. The high-voltage DC bus can be regarded as the main power source to the high-voltage facility of the vehicle mounted power system, and the middle-voltage output terminals can supply power to the low-voltage equipment on an automobile. In the respect of control algorithm, it is the first time to propose the SMC-PID (Proportion Integration Differentiation) control algorithm, in which the SMC algorithm is utilized and the PID control is attended to the conventional SMC algorithm. The PID control increases the dynamic ability of the SMC algorithm by establishing the corresponding SMC surface and introducing the attached integral of voltage error, which endow the sliding-control system with excellent dynamic performance. At last, we established the MATLAB/SIMULINK simulation model, tested performance of the system, and built the hardware prototype based on Digital Signal Processor (DSP). Results show that the sliding mode control is able to track a required trajectory, which has robustness against the uncertainties and disturbances.

  20. Sliding-mode control of single input multiple output DC-DC converter.

    PubMed

    Zhang, Libo; Sun, Yihan; Luo, Tiejian; Wan, Qiyang

    2016-10-01

    Various voltage levels are required in the vehicle mounted power system. A conventional solution is to utilize an independent multiple output DC-DC converter whose cost is high and control scheme is complicated. In this paper, we design a novel SIMO DC-DC converter with sliding mode controller. The proposed converter can boost the voltage of a low-voltage input power source to a controllable high-voltage DC bus and middle-voltage output terminals, which endow the converter with characteristics of simple structure, low cost, and convenient control. In addition, the sliding mode control (SMC) technique applied in our converter can enhance the performances of a certain SIMO DC-DC converter topology. The high-voltage DC bus can be regarded as the main power source to the high-voltage facility of the vehicle mounted power system, and the middle-voltage output terminals can supply power to the low-voltage equipment on an automobile. In the respect of control algorithm, it is the first time to propose the SMC-PID (Proportion Integration Differentiation) control algorithm, in which the SMC algorithm is utilized and the PID control is attended to the conventional SMC algorithm. The PID control increases the dynamic ability of the SMC algorithm by establishing the corresponding SMC surface and introducing the attached integral of voltage error, which endow the sliding-control system with excellent dynamic performance. At last, we established the MATLAB/SIMULINK simulation model, tested performance of the system, and built the hardware prototype based on Digital Signal Processor (DSP). Results show that the sliding mode control is able to track a required trajectory, which has robustness against the uncertainties and disturbances.

  1. Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Alalusi, Mazin; Stolpner, Lew; Margaritis, Georgios; Camp, Jordan B.; Krainak, Michael A.

    2014-01-01

    We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064-nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Especially, using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to104 at 10 mHz. The PW-ECLs compactness and low cost make it a candidate to replace traditional Nd:YAGnon-planar ring oscillators and fiber lasers in applications which require a single longitudinal-mode.

  2. Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Alalusi, Mazin; Stolpner, Lew; Margaritis, Georgios; Camp, Jordan; Krainak, Michael

    2014-01-01

    We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064 nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to 104 at 10 mHz. The PWECL's compactness and low cost make it a candidate to replace traditional Nd:YAG nonplanar ring oscillators and fiber lasers in applications that require a single longitudinal mode.

  3. 90-fs diode-pumped Yb:CLNGG laser mode-locked using single-walled carbon nanotube saturable absorber.

    PubMed

    Zhang, Yuangeng; Petrov, Valentin; Griebner, Uwe; Zhang, Xingyu; Choi, Sun Young; Gwak, Ji Yoon; Rotermund, Fabian; Mateos, Xavier; Yu, Haohai; Zhang, Huaijin; Liu, Junhai

    2014-03-10

    A diode-pumped Yb:CLNGG laser is mode-locked with a single-walled carbon nanotube saturable absorber (SWCNT-SA) for the first time. Pulse durations as short as 90 fs are obtained at ~1049 nm with 0.4% output coupler, the shortest pulses to our knowledge for a diode-pumped 1-µm laser applying SWCNTs as saturable absorber. Using 3% output coupler, the maximum average output power reached 90 mW at a repetition frequency of 83 MHz.

  4. Statistical properties of intensity of partially polarised semiconductor laser light backscattered by a single-mode optical fibre

    SciTech Connect

    Alekseev, A E; Potapov, V T; Gorshkov, B G

    2015-08-31

    We report the results of studying statistical properties of the intensity of partially polarised coherent light backscattered by a single mode optical fibre. An expression is derived for the deviation of the backscattered light intensity depending on the scattering region length, the degree of the light source coherence and the degree of scattered light polarisation. It is shown that the backscattered light in a fibre scattered-light interferometer is partially polarised with the polarisation degree P = 1/3 in the case of external perturbations of the interferometer fibre. (scattering of light)

  5. Diffractionless beam in free space with adiabatic changing refractive index in a single mode tapered slab waveguide.

    PubMed

    Tsai, Chang-Ching; Vinegoni, Claudio; Weissleder, Ralph

    2009-11-23

    We propose a novel design to produce a free space diffractionless beam by adiabatically reducing the difference of the refractive index between the core and the cladding regions of a single mode tapered slab waveguide. To ensure only one propagating eigenmode in the adiabatic transition, the correlation of the waveguide core width and the refractive index is investigated. Under the adiabatic condition, we demonstrate that our waveguide can emit a diffractionless beam in free space up to 500 micrometers maintaining 72% of its original peak intensity. The proposed waveguide could find excellent applications for imaging purposes where an extended depth of field is required.

  6. 75 W 40% efficiency single-mode all-fiber erbium-doped laser cladding pumped at 976 nm.

    PubMed

    Kotov, L V; Likhachev, M E; Bubnov, M M; Medvedkov, O I; Yashkov, M V; Guryanov, A N; Lhermite, J; Février, S; Cormier, E

    2013-07-01

    Optimization of Yb-free Er-doped fiber for lasers and amplifiers cladding pumped at 976 nm was performed in this Letter. The single-mode fiber design includes an increased core diameter of 34 μm and properly chosen erbium and co-dopant concentrations. We demonstrate an all-fiber high power laser and power amplifier based on this fiber with the record slope efficiency of 40%. To the best of our knowledge, the achieved output power of 75 W is the highest power reported for such lasers.

  7. 40 Gb/s 2R Burst Mode Receiver with a single integrated SOA-MZI switch.

    PubMed

    Kanellos, G T; Pleros, N; Petrantonakis, D; Zakynthinos, P; Avramopoulos, H; Maxwell, G; Poustie, A

    2007-04-16

    We demonstrate a novel scheme for 2R burst mode reception capable of operating error-free with 40 Gb/s variable length, asynchronous optical data packets that exhibit up to 9 dB packet-to-packet power variation. It consists of a single, hybrid integrated, SOA-based Mach-Zehnder Interferometer (SOA-MZI) with unequal splitting ratio couplers, configured to operate as a self-switch. We analyze theoretically the power equalization properties of unequal splitting ratio SOA-MZI switches and show good agreement between theory and experiment.

  8. Characteristics of the single-longitudinal-mode planar-waveguide external cavity diode laser at 1064 nm.

    PubMed

    Numata, Kenji; Alalusi, Mazin; Stolpner, Lew; Margaritis, Georgios; Camp, Jordan; Krainak, Michael

    2014-04-01

    We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064 nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to 10(4) at 10 mHz. The PW-ECL's compactness and low cost make it a candidate to replace traditional Nd:YAG nonplanar ring oscillators and fiber lasers in applications that require a single longitudinal mode.

  9. Physical conditions of single-longitudinal-mode operation for high-power all-solid-state lasers.

    PubMed

    Lu, Huadong; Su, Jing; Zheng, Yaohui; Peng, Kunchi

    2014-03-01

    The optimal physical conditions of single-longitudinal-mode (SLM) operation for continuous-wave all-solid-state lasers with high output powers are investigated theoretically and experimentally. The dependence of the operation conditions on the linear and nonlinear intracavity losses of the laser is numerically calculated. The theoretical analysis is demonstrated by the experimental measurements on a home-made Nd:YVO4 laser. The stable SLM output up to 33.7 W with optical-optical conversion efficiency of 44.9% at 1064 nm wavelength is recorded for over 7 h. The experimental results are in good agreement with the theoretical expectation.

  10. 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.

  11. Design of a control system for ultrafast x-ray camera working in a single photon counting mode

    NASA Astrophysics Data System (ADS)

    Zoladz, Miroslaw; Rauza, Jacek; Kasinski, Krzysztof; Maj, Piotr; Grybos, Pawel

    2015-09-01

    Prototype of Ultra-Fast X-Ray Camera Controller working in a single photon counting mode and based on ASIC has been presented in this paper. An ASIC architecture has been discussed with special attention to digital part. We present the Custom Soft Processor as an ASIC control sequences generator. The Processor allows for dynamic program downloading and generating control sequences with up to 80MHz clock rate (preliminary results). Assembler with a very simple syntax has been defined to speed up Processor programs development. Discriminators threshold dispersion correction has been performed to confirm proper Camera Controller operation.

  12. Spectral and Non Radiative Decay Studies of Lead Di Bromide Single Crystals by Mode Matched Thermal Lens Technique.

    PubMed

    Rejeena, I; Lillibai, B; Thomas, V; Nampoori, V P N; Radhakrishnan, P

    2016-07-01

    In the present paper, the investigations on the non radiative decay mechanism, optical band gap determination from absorption spectroscopic studies and fluorescence emission by photo luminescence techniques using different excitation wavelengths on gel derived lead di bromide single crystals are reported. Non radiative decay of the sample is studied using high sensitive dual beam mode matched thermal lens technique. For the thermal lensing experiment the crystal in solution phase is incorporated with rhodamine 6G dye for enhancing the absorption of the crystal sample. The thermal diffusivity of lead di bromide is determined using the probe beam intensity v/s time measurements.

  13. Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier.

    PubMed

    Pan, Shilong; Zhao, Xiaofan; Lou, Caiyun

    2008-04-15

    We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.

  14. Saving entangled photons from sudden death is a single-mode fiber --- Interplay of Decoherence and dynamical decoupling

    NASA Astrophysics Data System (ADS)

    Gupta, Manish Kumar; You, Chenglong; Dowling, Jonathan P.; Lee, Hwang

    2016-05-01

    We study the dynamics of decoherence in an optical fiber for the case of entangled photons. Such a study will allow us to increase the physical length of fiber for transmission of entangled photon from the sources such as SPDC. We analytically derive the model for Decoherence of entangled state photons in a single-mode fiber. We also show that entanglement lifetime can be increased for Bell state and Werner state with open loop control technique called Dynamical decoupling. The authors would like to acknowledge support from the Air Force Office of Scientific Research, the Army Research Office, the National Science Foundation and the Northrop Grumman Corporation.

  15. Plasmonic enhancement of a whispering-gallery-mode biosensor for single nanoparticle detection

    NASA Astrophysics Data System (ADS)

    Shopova, S. I.; Rajmangal, R.; Holler, S.; Arnold, S.

    2011-06-01

    We describe and demonstrate a physical mechanism that substantially enhances the label-free sensitivity of a whispering-gallery-mode biosensor for the detection of individual nanoparticles in aqueous solution. It involves the interaction of dielectric nanoparticle in an equatorial carousel orbit with a plasmonic nanoparticle bound at the microparticle's equator. As the dielectric particle parks to hot spots on the plasmonic particle we observe frequency shifts that are enhanced by a factor of 4, consistent with a simple reactive model. Once optimized the enhancement by this mechanism should exceed several orders of magnitude, putting individual protein within reach.

  16. Pump power stability range of single-mode solid-state lasers with rod thermal lensing

    SciTech Connect

    De Silvestri, S.; La Porta, P.; Magni, V.

    1987-11-01

    The pump power stability range of solid-state laser resonators operating in the TEM/sub 00/ mode has been thoroughly investigated. It has been shown that, for a very general resonator containing intracavity optical systems, rod thermal lensing engenders a pump power stability range which is a characteristic parameter of laser material and pump cavity, but is independent of resonator configuration. Stability ranges have been calculated and critically discussed for Nd:YAG, Nd:Glasses, Nd:Cr:GSGG, and alexandrite. The independence of the pump power stability range from the resonator configuration has been experimentally demonstrated for a CW Nd:YAG laser.

  17. Reliability and performance of 808-nm single emitter multi-mode laser diodes

    NASA Astrophysics Data System (ADS)

    Wang, J.; Bao, L.; Devito, M.; Xu, D.; Wise, D.; Grimshaw, M.; Dong, W.; Zhang, S.; Bai, C.; Leisher, P.; Li, D.; Zhou, H.; Patterson, S.; Martinsen, R.; Haden, J.

    2010-02-01

    Performance, lifetest data, as well as failure modes from two different device structures will be discussed in this paper, with emitting wavelengths from 780nm to 800nm. The first structure, designed for high temperature operation, has demonstrated good reliability on various packages with output power up to 10W from a 200μm emitting area. The device structure can be operated up to 60°C heatsink temperatures under CW conditions. Then a high efficiency structure is shown with further improvement on operation power and reliability, for room temperature operation. With ongoing lifetest at 12A and 50°C heatsink temperature, <1000 FIT has been achieved for 6.5W and 33°C operation, on both designs. MTT10%F at 10W and 25°C operation is estimated to be more than 20,000 hours. Devices retain more than 20W rollover power under CW conditions, when re-tested after several thousand hours of accelerated lifetest. Paths for reliability improvement will also be discussed based on observed lifetest failure modes from these two structures.

  18. Flow cytometer system for single-shot biosensing based on whispering gallery modes of fluorescent microspheres

    NASA Astrophysics Data System (ADS)

    Lessard, Reno; Rousseau-Cyr, Olivier; Charlebois, Maxime; Riviere, Christophe; Mermut, Ozzy; Allen, Claudine Nı.

    2013-02-01

    We report an innovative label-free biosensor based on statistical analysis of several whispering gallery modes spectral shifts in polystyrene fluorescent microspheres using a custom microflow cytometer. Whispering gallery modes analysis enables detection of nanometer-sized analytes showing promising possibilities for virus, bacteria and molecular detection. To demonstrate this, fluorophore-doped microspheres of the appropriate size parameter are mixed in an aqueous solution. Then, a syringe pump pushes the solution through a fiber optic flow cell where a laser beam illuminates the analysis area to excite the microspheres and their fluorescence is collected. This device provides a low-cost and user friendly solution that could enhance spectrum acquisition rates up to 5 spectra per second thanks to the considerable amount of microspheres flowing through the excitation area per unit time. Finally, the fluorescence spectra are statistically investigated using an instantaneous measurement of apparent refractive index algorithm to determine a reliable value for the refractive index of the environment since the exact radius of the microsphere scanned is unknown. This refractive index becomes an effective value for the local perturbation caused by inhomogeneities on the microsphere surface and hence, determines whether or not inhomogeneities, such as bacteria, are adsorbed by comparing to a control sample. Combining a flow cell with our detection algorithm, we reduce the period of a 50 microspheres experiment from 161 minutes to 14 minutes when the flow rate is 2000 µl/h and the microsphere concentration is 5 µsphere/µl.

  19. Simultaneous PIV/PLIF measurements of Richtmyer-Meshkov Instabilities from single- and multi-mode perturbed interfaces

    NASA Astrophysics Data System (ADS)

    Mejia-Alvarez, Ricardo; Wilson, Brandon; Prestridge, Kathy; Extreme Fluids Team

    2013-11-01

    To support validation of RANS and LES codes for single-interface Richtmyer-Meshkov mixing, the Extreme Fluids Team at Los Alamos National Laboratory commissioned a Vertical Shock Tube. This facility has the capability of generating statistically stationary single- and multi-mode spatial perturbations on the fluid interface prior to shock-interface interaction. The present study focuses on comparing the evolution of shock-driven mixing under two different spatial perturbation conditions after interacting with a M = 1.2 shock wave. High resolution simultaneous PIV and PLIF are used for capturing 2D instantaneous realizations of velocity and density at different stages of the evolving interface. Multiple realizations of the flow at each one of these evolution stages are obtained to characterize the flow statistically. Also, a modal analysis via Singular Value Decomposition is performed on the density and velocity fields to elucidate the role of initial flow scales content on the transition to turbulent mixing.

  20. High reliability, high power arrays of 808 nm single mode diode lasers employing various quantum well structures

    NASA Astrophysics Data System (ADS)

    Qiu, B. C.; Kowalski, O.; McDougall, S. D.; Liu, X. F.; Marsh, J. H.

    2008-02-01

    Single mode laser diode arrays operating at 808 nm have been designed and fabricated using several different waveguide and quantum well combinations. In order to operate these devices at 200 mW per element a quantum well intermixing process has been used to render their facets non-absorbing and thus they do not suffer from mirror damage related failure. In this paper we demonstrate extremely high levels of reliability for GaAs and AlGaAs quantum well devices with arrays of 64 elements completing over 6000 hours continuous operation without any single laser element failure and a correspondingly low power degradation rate of <1% k/hr. In contrast we show extremely high power degradation rates for arrays using InGaAs and InAlGaAs 808 nm quantum wells laser arrays.