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Sample records for dispersion compensating photonic

  1. Numerical comparison between conventional dispersion compensating fibers and photonic crystal fibers as lumped Raman amplifiers.

    PubMed

    Castellani, C E S; Cani, S P N; Segatto, M E V; Pontes, M J; Romero, M A

    2009-12-01

    In this paper we discuss the use of photonic crystal fibers (PCFs) as discrete devices for simultaneous wideband dispersion compensation and Raman amplification. The performance of the PCFs in terms of gain, ripple, optical signal-to-noise ratio (OSNR) and required fiber length for complete dispersion compensation is compared with conventional dispersion compensating fibers (DCFs). The main goal is to determine the minimum PCF loss beyond which its performance surpasses a state-of-the-art DCF and justifies practical use in telecommunication systems. PMID:20052245

  2. Computation of Parameters for Dispersion Compensating Photonic Crystal Fiber Using a Novel Approach

    NASA Astrophysics Data System (ADS)

    Ghobadi, Changiz; Ehteshami, Nasrin

    2012-06-01

    In this article, an efficient compact two dimensional finite-difference frequency-domain (2-D FDFD) method has been used to model photonic Crystal fiber (PCF). Different values of dispersion coefficient can be obtained by changing fiber parameters using FDFD method. Since for each one of these parameters there exists a different value for dispersion coefficient, selection of optimal point will be a time consuming process. Here, first of all, we calculate parameter K, which is the key factor to design dispersion compensated fibers, so the design process will be faster and easier. The optimal value for K parameter is around 301.8 nm for transmission line fibers. So, it is enough to sketch both dispersion curve and K parameter versus PCF parameters, in a single coordinate system. Proper parameters will be obtained by analyzing the curves.

  3. Analysis and compensation of dispersion-induced bit loss in a photonic A/D converter using time-wavelength interweaved sampling clock.

    PubMed

    Li, Ming; Wu, Guiling; Guo, Pan; Li, Xinwan; Chen, Jianping

    2009-09-28

    In this paper, the timing jitter induced by the fiber dispersion in photonic A/D converters using time-wavelength interweaved sampling clocks generated by optical time-division-multiplexing (OTDM) with fiber delay lines is analyzed and effective bit loss is calculated. A compensation method is proposed to decrease the dispersion-induced jitter. Simulations are performed and the results show the validity of the proposed compensation method. An experimental demonstration is carried out to verify the theoretical expression derived. PMID:19907563

  4. Dispersion in photonic crystals

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy

    2005-11-01

    Investigations on the dispersive properties of photonic crystals, modified scattering in ring-resonators, monolithic integration of vertical-cavity surface-emitting lasers and advanced data processing techniques for the finite-difference time-domain method are presented. Photonic crystals are periodic mesoscopic arrays of scatterers that modify the propagation properties of electromagnetic waves in a similar way as "natural" crystals modify the properties of electrons in solid-state physics. In this thesis photonic crystals are implemented as planar photonic crystals, i.e., optically thin semiconductor films with periodic arrays of holes etched into them, with a hole-to-hole spacing of the order of the wavelength of light in the dielectric media. Photonic crystals can feature forbidden frequency ranges (the band-gaps) in which light cannot propagate. Even though most work on photonic crystals has focused on these band-gaps for application such as confinement and guiding of light, this thesis focuses on the allowed frequency regions (the photonic bands) and investigates how the propagation of light is modified by the crystal lattice. In particular the guiding of light in bulk photonic crystals in the absence of lattice defects (the self-collimation effect) and the angular steering of light in photonic crystals (the superprism effect) are investigated. The latter is used to design a planar lightwave circuit for frequency domain demultiplexion. Difficulties such as efficient insertion of light into the crystal are resolved and previously predicted limitations on the resolution are circumvented. The demultiplexer is also fabricated and characterized. Monolithic integration of vertical-cavity surface-emitting lasers by means of resonantly enhanced grating couplers is investigated. The grating coupler is designed to bend light through a ninety-degree angle and is characterized with the finite-difference time-domain method. The vertical-cavity surface-emitting lasers are

  5. Novel design of inherently gain-flattened discrete highly nonlinear photonic crystal fiber Raman amplifier and dispersion compensation using a single pump in C-band.

    PubMed

    Varshney, Shailendra; Fujisawa, Takeshi; Saitoh, Kunimasa; Koshiba, Masanori

    2005-11-14

    In this paper, we report, for the first time, an inherently gain-flattened discrete highly nonlinear photonic crystal fiber (HNPCF) Raman amplifier (HNPCF-RA) design which shows 13.7 dB of net gain (with +/-0.85-dB gain ripple) over 28-nm bandwidth. The wavelength dependent leakage loss property of HNPCF is used to flatten the Raman gain of the amplifier module. The PCF structural design is based on W-shaped refractive index profile where the fiber parameters are well optimized by homely developed genetic algorithm optimization tool integrated with an efficient vectorial finite element method (V-FEM). The proposed fiber design has a high Raman gain efficiency of 4.88 W(-1) . km(-1) at a frequency shift of 13.1 THz, which is precisely evaluated through V-FEM. Additionally, the designed module, which shows ultra-wide single mode operation, has a slowly varying negative dispersion coefficient (-107.5 ps/nm/km at 1550 nm) over the operating range of wavelengths. Therefore, our proposed HNPCF-RA module acts as a composite amplifier with dispersion compensator functionality in a single component using a single pump. PMID:19503154

  6. Dispersion compensation for attosecond electron pulses

    SciTech Connect

    Hansen, Peter; Baumgarten, Cory; Batelaan, Herman; Centurion, Martin

    2012-08-20

    We propose a device to compensate for the dispersion of attosecond electron pulses. The device uses only static electric and magnetic fields and therefore does not require synchronization to the pulsed electron source. Analogous to the well-known optical dispersion compensator, an electron dispersion compensator separates paths by energy in space. Magnetic fields are used as the dispersing element, while a Wien filter is used for compensation of the electron arrival times. We analyze a device with a size of centimeters, which can be applied to ultrafast electron diffraction and microscopy, and fundamental studies.

  7. Dispersion-compensated fresnel lens

    DOEpatents

    Johnson, Kenneth C.

    1992-01-01

    A transmission grating is used to reduce chromatic aberration in a Fresnel lens, wherein the lens chromatic dispersion is offset and substantially canceled by the grating's diffraction-induced dispersion. The grating comprises a Fresnel-type pattern of microscopic facets molded directly into the lens surface. The facets would typically have a profile height of around 4.multidot.10.sup.-5 inch and a profile width of at least 10.sup.-3 inch. In its primary intended application, the invention would function to improve the optical performance of a Fresnel lens used to concentrate direct sunlight.

  8. Dispersion-compensated Fresnel lens

    DOEpatents

    Johnson, K.C.

    1992-11-03

    A transmission grating is used to reduce chromatic aberration in a Fresnel lens, wherein the lens chromatic dispersion is offset and substantially canceled by the grating's diffraction-induced dispersion. The grating comprises a Fresnel-type pattern of microscopic facets molded directly into the lens surface. The facets would typically have a profile height of around 4[times]10[sup [minus]5] inch and a profile width of at least 10[sup [minus]3] inch. In its primary intended application, the invention would function to improve the optical performance of a Fresnel lens used to concentrate direct sunlight. 10 figs.

  9. Optimal packaging of dispersion-compensating fibers for matched nonlinear compensation and reduced optical noise.

    PubMed

    Wei, Haiqing; Plant, David V

    2005-09-15

    A method of packaging dispersion-compensating fibers (DCFs) is discussed that achieves optimal nonlinearity compensation and a good signal-to-noise ratio simultaneously. An optimally packaged dispersion-compensating module (DCM) may consist of portions of DCFs with higher and lower loss coefficients. Such optimized DCMs may be paired with transmission fibers to form scaled translation-symmetric lines that could effectively compensate for signal distortions due to dispersion and nonlinearity, with or without optical phase conjugation. PMID:16196322

  10. Dispersion Compensation of Fiber Optic Systems for KSC Applications

    NASA Technical Reports Server (NTRS)

    Kozaitis, Samuel P.; Hand, Larry

    1996-01-01

    Installed fibers such as those at the Kennedy Space Center (KSC) are optimized for use at 1310 nm because they have zero dispersion at that wavelength. An installed fiber system designed to operate at 1310 nm will operate at a much lower data rate when operated at 1550 nm because the dispersion is not zero at 1550 nm. Using dispersion measurements of both installed and dispersion compensating fibers, we compensated a 21.04 km length of installed fiber with 4.25 km of dispersion compensating fiber. Using the compensated fiber-optic link, we reduced the dispersion to 0.494 ps/nm-km, from an uncompensated dispersion of 16.8 ps/nm-km. The main disadvantage of the compensated link using DC fiber was an increase in attenuation. Although the increase was not necessarily severe, it could be significant when insertion losses, connector losses, and fiber attenuation are taken into account.

  11. Dispersion compensation in chirped pulse amplification systems

    SciTech Connect

    Bayramian, Andrew James; Molander, William A.

    2014-07-15

    A chirped pulse amplification system includes a laser source providing an input laser pulse along an optical path. The input laser pulse is characterized by a first temporal duration. The system also includes a multi-pass pulse stretcher disposed along the optical path. The multi-pass pulse stretcher includes a first set of mirrors operable to receive input light in a first plane and output light in a second plane parallel to the first plane and a first diffraction grating. The pulse stretcher also includes a second set of mirrors operable to receive light diffracted from the first diffraction grating and a second diffraction grating. The pulse stretcher further includes a reflective element operable to reflect light diffracted from the second diffraction grating. The system further includes an amplifier, a pulse compressor, and a passive dispersion compensator disposed along the optical path.

  12. Compressive sensing spectral domain optical coherence tomography with dispersion compensation

    NASA Astrophysics Data System (ADS)

    Xu, Daguang; Huang, Yong; Kang, Jin U.

    2014-03-01

    In this paper, we describe a novel CS method that incorporates dispersion compensation into the CS reconstruction of spectral domain OCT (SD OCT) signal. We show that A-scans with dispersion compensation can be obtained by multiplying the dispersion correcting term to the undersampled linear-in-wavenumber spectral data before the CS reconstruction. We also implemented fast CS reconstruction by taking the advantage of fast Fourier transform (FFT). The matrix-vector multiplication commonly used in the CS reconstruction is implemented by a two-step procedure. Compared to the CS reconstruction with matrix multiplication, our method can obtain dispersion compensated A-scan at least 5 times faster. Experimental results show that the proposed method can achieve high quality image with dispersion compensation.

  13. Three dispersion compensation methods for radio-over-fiber system

    NASA Astrophysics Data System (ADS)

    Pu, Tao; Meng, Fanqiu; Zhao, Jiyong; Fang, Tao; Zheng, Jilin; Huang, Long

    2016-03-01

    This paper introduces three different dispersion compensation methods based on superstructure fiber Bragg grating (SSFBG) and an injection distributed feedback (DFB) laser. First, an SSFBG with a nonlinearity group delay spectrum was designed to achieve tunable dispersion compensation. Second, an approach is proposed for realizing single-sideband modulation with an optimum optical carrier to sideband ratio for maximizing the transmission performance of a radio-over-fiber (RoF) system based on a strong optical injection-locked DFB laser. Finally, a broadband chromatic dispersion compensation scheme using an optical phase conjugator based on a DFB semiconductor laser is proposed and experimentally demonstrated in RoF links.

  14. Mode separation of Lamb waves based on dispersion compensation method.

    PubMed

    Xu, Kailiang; Ta, Dean; Moilanen, Petro; Wang, Weiqi

    2012-04-01

    Ultrasonic Lamb modes typically propagate as a combination of multiple dispersive wave packets. Frequency components of each mode distribute widely in time domain due to dispersion and it is very challenging to separate individual modes by traditional signal processing methods. In the present study, a method of dispersion compensation is proposed for the purpose of mode separation. This numerical method compensates, i.e., compresses, the individual dispersive waveforms into temporal pulses, which thereby become nearly un-overlapped in time and frequency and can thus be extracted individually by rectangular time windows. It was further illustrated that the dispersion compensation also provided a method for predicting the plate thickness. Finally, based on reversibility of the numerical compensation method, an artificial dispersion technique was used to restore the original waveform of each mode from the separated compensated pulse. Performances of the compensation separation techniques were evaluated by processing synthetic and experimental signals which consisted of multiple Lamb modes with high dispersion. Individual modes were extracted with good accordance with the original waveforms and theoretical predictions. PMID:22501050

  15. Photon dispersion in a supernova core

    NASA Astrophysics Data System (ADS)

    Kopf, Alexander; Raffelt, Georg

    1998-03-01

    While the photon forward-scattering amplitude on free magnetic dipoles (e.g. free neutrons) vanishes, the nucleon magnetic moments still contribute significantly to the photon dispersion relation in a supernova (SN) core where the nucleon spins are not free due to their interaction. We study the frequency dependence of the relevant spin susceptibility in a toy model with only neutrons which interact by one-pion exchange. Our approach amounts to calculating the photon absorption rate from the inverse bremsstrahlung process γnn-->nn, and then deriving the refractive index nrefr with the help of the Kramers-Kronig relation. In the static limit (ω-->0) the dispersion relation is governed by the Pauli susceptibility χPauli so that n2refr-1~χPauli>0. For ω somewhat above the neutron spin-relaxation rate Γσ we find n2refr-1<0, and for ω>>Γσ the photon dispersion relation acquires the form ω2-k2=m2γ. An exact expression for the ``transverse photon mass'' mγ is given in terms of the f-sum of the neutron spin autocorrelation function; an estimate is m2γ~χPauliTΓσ. The dominant contribution to nrefr in a SN core remains the electron plasma frequency so that the Cherenkov processes γν<-->ν remain forbidden for all photon frequencies.

  16. Chirped-cavity dispersion-compensation filter design

    NASA Astrophysics Data System (ADS)

    Li, Ya-Ping; Chen, Sheng-Hui; Lee, Cheng-Chung

    2006-03-01

    A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

  17. Highly dispersive photonic band-gap prism.

    PubMed

    Lin, S Y; Hietala, V M; Wang, L; Jones, E D

    1996-11-01

    We propose the concept of a photonic band-gap (PBG) prism based on two-dimensional PBG structures and realize it in the millimeter-wave spectral regime. We recognize the highly nonlinear dispersion of PBG materials near Brillouin zone edges and utilize the dispersion to achieve strong prism action. Such a PBG prism is very compact if operated in the optical regime, ~20 mm in size for lambda ~ 700 nm, and can serve as a dispersive element for building ultracompact miniature spectrometers. PMID:19881796

  18. Design optimization of flattop interleaver and its dispersion compensation.

    PubMed

    Wei, L; Lit, J W Y

    2007-05-14

    The objective of this paper is to present a general strategy for design optimization of flattop interleavers, and dispersion compensation for the interleavers, in order to achieve superior optical performance. The interleaver is formed by two multi-cavity Gire-Tournois etalons (MC-GTE) in a Michelson Interferometer (MI). An interleaver that has m cavities in one etalon and n cavities in the other is called an mn-GTE interleaver. Our optimization strategy exploits the general flattop condition and the technique of ripple equalization. Any mn-GTE interleaver may be optimized. The spectral performance can be greatly improved by the optimization process. As an illustration, we present a comprehensive analysis for a 11-GTE and a 21-GTE interleaver. The analytical expressions for flattop conditions, peak and trough positions are derived for optimization. The optimal performance of the interleavers can be controlled by the reflection coefficients and the parameters m and n. To achieve low-dispersion mn-GTE flattop interleavers, we propose to use one additional MC-GTE as a dispersion compensator to compensate for the chromatic dispersion. The analytical expressions of group delays and chromatic dispersions for an MC-GTE interleaver are derived. The optimization strategy of dispersion-ripple equalization is explained. The results show that the dispersion performance can be tailored by changing the reflection coefficients of the MC-GTE, and the dispersion and bandwidth can be enhanced by increasing the number of cavities of the MC-GTE. PMID:19546950

  19. Kerr-lens mode locking without dispersion compensation.

    PubMed

    Gatz, S; Herrmann, J; Müller, M

    1996-10-01

    We propose and theoretically investigate a novel operating regime of femtosecond Kerr-lens mode-locked solidstate lasers that avoids group-velocity dispersion compensation by use of a nonresonant semiconductor plate in the focused resonator section that provides an overall negative nonlinear refractive index per round trip. The saturable loss of the laser resonator with an effective self-defocusing nonlinearity is derived from a generalized ABCD matrix formalism, and the correspondingly calculated steady-state pulse parameters show that a Kerrlens mode-locked laser with an overall negative nonlinear refractive index generates stable femtosecond pulses without any dispersion compensation. PMID:19881729

  20. Optical dispersion compensation in 300-pin MSA transponders

    NASA Astrophysics Data System (ADS)

    Mendlovic, David; Shabtay, Gal

    2005-02-01

    The 300-pin Multi Source Agreement (MSA) and other MSAs provide basic requirements from a transponder or transceiver used in 10Gb/s optical networks. These MSAs typically address a wide range of applications, including: SONET/SDH, 10GbE and 10GFC for Metro, long-haul (LH) and ultra-long-haul (ULH) networks. Nonetheless, being a basic standard, the 300-pin MSA addresses the minimal required specifications set and does not cover the whole set of requirements and applications that system vendors are interested in. For example, widely tunable and extended reach transponders are not included in the 300-pin MSA. Chromatic dispersion is one of the major reach limiting factors in optical networks. In reconfigurable optical networks, chunks of DWDM channels may travel through different routes and therefore require tunable dispersion compensation. In static ULH optical networks, the number of dispersion compensation fibers (DCFs) dictates the amount of residual chromatic dispersion. This residual chromatic dispersion differs from one DWDM channel to the other. Unless it is compensated at the receiver, it further restricts the link length and reduces the distance between one regenerator to the other. This results in shorter links and more O-E-O blocks, which dramatically increases the cost of the network. This paper discusses a specially designed optical dispersion compensation (ODC) device that is packaged in a standard butterfly package and can fit into a 300-pin MSA transponder. A transponder with the proposed ODC can still satisfy all the basic requirements that are described in the 300-pin MSA while providing improved chromatic dispersion tolerance.

  1. Kerr-lens mode locking without dispersion compensation

    SciTech Connect

    Gatz, S.; Herrmann, J.; Mueller, M.

    1996-10-01

    We propose and theoretically investigate a novel operating regime of femtosecond Kerr-lens mode-locked solid-state lasers that avoids group-velocity dispersion compensation by use of a nonresonant semiconductor plate in the focused resonator section that provides an overall negative nonlinear refractive index per round trip. The saturable loss of the laser resonator with an effective self-defocusing nonlinearity is derived from a generalized {ital ABCD} matrix formalism, and the correspondingly calculated steady-state pulse parameters show that a Kerr-lens mode-locked laser with an overall negative nonlinear refractive index generates stable femtosecond pulses without any dispersion compensation. {copyright} {ital 1996 Optical Society of America.}

  2. Dispersion Compensation Requirements for Optical CDMA Using WDM Lasers

    SciTech Connect

    Mendez, A J; Hendandez, V J; Feng, H X C; Heritage, J P; Lennon, W J

    2001-12-10

    Optical code division multiple access (O-CDMA) uses very narrow transmission pulses and is thus susceptible to fiber optic link impairments. When the O-CDMA is implemented as wavelength/time (W/T) matrices which use wavelength division multiplexing (WDM) sources such as multi-frequency laser transmitters, the susceptibility may be higher due to: (a) the large bandwidth utilized and (b) the requirement that the various wavelength components of the codes be synchronized at the point of modulation and encoding as well as after (optical) correlation. A computer simulation based on the nonlinear Schroedinger equation, developed to study optical networking on the National Transparent Optical Network (NTON), was modified to characterize the impairments on the propagation and decoding of W/T matrix codes over a link of the NTON. Three critical link impairments were identified by the simulation: group velocity dispersion (GVD); the flatness of the optical amplifier gain; and the slope of the GVD. Subsequently, experiments were carried out on the NTON link to verify and refine the simulations as well as to suggest improvements in the W/T matrix signal processing design. The NTON link measurements quantified the O-CDMA dispersion compensation requirements. Dispersion compensation management is essential to assure the performance of W/T matrix codes.

  3. Flexible OFDM-based access systems with intrinsic function of chromatic dispersion compensation

    NASA Astrophysics Data System (ADS)

    Konishi, Tsuyoshi; Murakawa, Takuya; Nagashima, Tomotaka; Hasegawa, Makoto; Shimizu, Satoshi; Hattori, Kuninori; Okuno, Masayuki; Mino, Shinji; Himeno, Akira; Uenohara, Hiroyuki; Wada, Naoya; Cincotti, Gabriella

    2015-12-01

    Cost-effective and tunable chromatic dispersion compensation in a fiber link are still an open issue in metro and access networks to cope with increasing costs and power consumption. Intrinsic chromatic dispersion compensation functionality of optical fractional orthogonal frequency division multiplexing is discussed and experimentally demonstrated using dispersion-tunable transmitter and receiver based on wavelength selective switching devices.

  4. Optical pulse compression using the combination of phase modulation and high-order dispersion compensation

    NASA Astrophysics Data System (ADS)

    Deng, Guo; Pan, Wei; Zou, Xihua

    2010-09-01

    Optical pulse compression using high-order dispersion compensation is proposed and theoretically analyzed. Firstly, the required dispersion profile for the high-order dispersion compensation is derived, according to the linear chirp and the nonlinear chirp of a phase-modulated continuous-wave (CW) laser source. With the use of the high-order dispersion compensation, such as the combination compensation of the second order dispersion (SOD) and the fourth order dispersion (FOD), an efficient pulse compression having a less time-bandwidth product and a greater peak power is realized. A sampled fiber Bragg grating (FBG) with both the SOD and the FOD is then designed using the equivalent chirp and the reconstruction algorithm. Finally, in the numerical simulation an optical pulse with a time-bandwidth product of 0.79 is generated via high-order dispersion compensation that is performed by using the sampled FBG.

  5. Highly dispersive photonic band-gap-edge optofluidic biosensors

    NASA Astrophysics Data System (ADS)

    Xiao, S.; Mortensen, N. A.

    2006-11-01

    Highly dispersive photonic band-gap-edge optofluidic biosensors are studied theoretically. We demonstrate that these structures are strongly sensitive to the refractive index of the liquid, which is used to tune dispersion of the photonic crystal. The upper frequency band-gap edge shifts about 1.8 nm for δ n=0.002, which is quite sensitive. Results from transmission spectra agree well with those obtained from the band structure theory.

  6. Dispersion-compensating dual-mode optical fibers desirable for erbium-doped-fiber-amplified systems

    SciTech Connect

    Eguchi, Masashi

    2001-06-01

    A broadband dispersion-compensating dual-mode optical fiber with a double-layer profile core is proposed to compensate for positive dispersion in conventional single-mode optical fibers operating near 1.55 {mu}m. This wavelength band is suitable for erbium-doped-fiber-amplified systems. It is known that the first higher-order mode of dual-mode fibers exhibits large negative waveguide dispersion, and double-layer profile core fibers are dispersion-shifted fibers whose transmission and bending losses are lower than those of simple core-cladding dispersion-shifted fibers. Such advantages are attractive for commercial devices or modules. Here, a dispersion-compensating dual-mode fiber with a double-layer profile core that satisfies both low bending loss and broadband dispersion compensation is proposed. {copyright} 2001 Optical Society of America

  7. Efficient reflection grisms for pulse compression and dispersion compensation of femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Gibson, Emily A.; Gaudiosi, David M.; Kapteyn, Henry C.; Jimenez, Ralph; Kane, Steve; Huff, Rachel; Durfee, Charles; Squier, Jeff

    2006-11-01

    Efficient reflection grisms for pulse-compression and material-dispersion compensation have been designed and demonstrated in a 40 fs, 300 μJ, 5 kHz downchirped pulse amplification system for the first time to our knowledge. A grism design for 800nm femtosecond laser pulse dispersion compensation applications is realized by using standard, commercial diffraction gratings.

  8. A novel method for combating dispersion induced power fading in dispersion compensating fiber.

    PubMed

    Lebedev, Alexander; Olmos, J J Vegas; Iglesias, Miguel; Forchhammer, Søren; Monroy, Idelfonso Tafur

    2013-06-01

    We experimentally investigate the performance of 60 GHz double sideband (DSB) radio over fiber (RoF) links that employ dispersion compensating fiber (DCF). Error free transmission of 3 Gbps signals over 1 m of wireless distance is reported. In order to overcome experimentally observed chromatic dispersion (CD) induced power fading of radio frequency (RF) signal, we propose a method for improvement of RF carrier-to-noise (C/N) ratio through introduction of a degree of RF frequency tunability. Overall results improve important aspects of directly modulated RoF systems and demonstrate the feasibility of high carrier frequency and wide bandwidth RF signals delivery in RoF links including DCF fiber. Error free performance that we obtain for 3 Gbps amplitude shift-keying (ASK) signals enables uncompressed high-definition 1080p video delivery. PMID:23736614

  9. High-energy femtosecond Yb-doped dispersion compensation free fiber laser.

    PubMed

    Ortaç, B; Schmidt, O; Schreiber, T; Limpert, J; Tünnermann, A; Hideur, A

    2007-08-20

    We report on a mode-locked high energy fiber laser operating in the dispersion compensation free regime. The sigma cavity is constructed with a saturable absorber mirror and short-length large-mode-area photonic crystal fiber. The laser generates positively-chirped pulses with an energy of 265 nJ at a repetition rate of 10.18 MHz in a stable and self-starting operation. The pulses are compressible down to 400 fs leading to a peak power of 500 kW. Numerical simulations accurately reflect the experimental results and reveal the mechanisms for self consistent intracavity pulse evolution. With this performance mode-locked fiber lasers can compete with state-of-the-art bulk femtosecond oscillators for the first time and pulse energy scaling beyond the muJ-level appears to be feasible. PMID:19547427

  10. Enhanced dispersion compensation capability of angular elements based on beam expansion.

    PubMed

    Du, Rui; Jiang, Runhua; Fu, Ling

    2009-09-14

    We demonstrate that beam size manipulation plays an important role in dispersion compensation. With expanded beam, the maximal negative group delay dispersion (GDD) provided by angular elements increases by an order of magnitude compared with original beam. Both calculation and experimental results show that a modest 2 x and 4 x expanded beams can improve dispersion compensation capability of prisms or acousto-optical deflectors: the restored minimal pulse width decreases by 50% and the corresponding distance between angular elements is shortened more than 70 cm. These findings will be helpful for designing dispersion compensation schemes for femtosecond pulse laser application systems such as multiphoton microscopy or laser micromachining. PMID:19770855

  11. Cancellation of third-order nonlinear effects in amplified fiber links by dispersion compensation, phase conjugation, and alternating dispersion.

    PubMed

    Marhic, M E; Kagi, N; Chiang, T K; Kazovsky, L G

    1995-04-15

    We show that in principle it is possible to cancel third-order nonlinear effects in optical fiber links. The necessary conditions exist in two-segment links, with dispersion compensation, phase conjugation, and amplification between the two, as well as opposite chromatic dispersion coefficients in the segments. The cancellation is independent of loss, modulation format, and modulation frequency. PMID:19859355

  12. All-channel tunable optical dispersion compensator based on linear translation of a waveguide grating router.

    PubMed

    Sinefeld, David; Ben-Ezra, Shalva; Doerr, Christopher R; Marom, Dan M

    2011-04-15

    We propose and demonstrate a compact tunable optical dispersion compensation (TODC) device with a 100 GHz free spectral range capable of mitigating chromatic dispersion impairments. The TODC is based on longitudinal movement of a waveguide grating router, resulting in chromatic dispersion compensation of ±1000 ps/nm. We employed our TODC device for compensating 42.8 Gbit/sec differential phase-shifting keying signal, transmitted over 50 km fiber with a -2 dB power penalty at 10⁻⁹. PMID:21499373

  13. Design and Fabrication of Efficient Reflection Grisms for Pulse Compression and Dispersion Compensation

    NASA Astrophysics Data System (ADS)

    Kane, Steve; Tortajada, Fred; Dinger, Herb; Touzet, Bruno; Huff, Rachel; Squier, Jeff; Durfee, Charles; Gibson, Emily; Jimenez, Ralph; Gaudiosi, David; Kapteyn, Henry

    Efficient reflection grisms for pulse compression and material-dispersion compensation have been designed and demonstrated in a CPA system. Designs for 800-nm and 1030-nm ultrafast applications are characterized using off-the-shelf diffraction gratings.

  14. Compensation of spatial dispersion of an acousto-optic deflector with a special Keplerian telescope.

    PubMed

    Hu, Qinglei; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2016-01-15

    Compensation of spatial dispersion caused by the acousto-optic deflector (AOD) when using a femtosecond laser is difficult across the whole scanning range of the system, and this is a significant impediment to its use. In conventional methods, the dispersion of the AOD was compensated only when it was at a particular position, while at other positions, the quality of the light beam was reduced. We developed a novel method for compensating the spatial dispersion within the entire scanning range using a special Keplerian telescope. Our experimental results show that the residual dispersion of the AOD is compensated sufficiently, and the focal spots of the laser reach the diffraction limit within a 40-MHz ultrasound bandwidth. PMID:26766675

  15. Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation.

    PubMed

    Zeylikovich, I; Sztul, H I; Kartazaev, V; Le, T; Alfano, R R

    2007-07-15

    Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses. PMID:17632631

  16. Ultrafast optics in dispersion-flattened photonic crystal fiber

    SciTech Connect

    Reeves, W. H.; Knight, J. C.; Russell, P. S. J.; Skryabin, D. V.; Omenetto, F. G.; Efimov, A. V.; Taylor, Antoinette J.,

    2002-01-01

    llOfs pulses at 1550nm wavelength were launched in to various ultra flattened dispersion photonic crystal fibers. For output powers of around 100mW spectral components were generated in a range greater than 350-22OOnm.

  17. Dispersive photonic crystals from the plane wave method

    NASA Astrophysics Data System (ADS)

    Guevara-Cabrera, E.; Palomino-Ovando, M. A.; Flores-Desirena, B.; Gaspar-Armenta, J. A.

    2016-03-01

    Nowadays photonic crystals are widely used in many different applications. One of the most used methods to compute their band structure is the plane wave method (PWM). However, it can only be applied directly to non-dispersive media and be extended to systems with a few model dielectric functions. We explore an extension of the PWM to photonic crystals containing dispersive materials, that solves an eigenvalue equation for the Bloch wave vectors. First we compare our calculation with analytical results for one dimensional photonic crystals containing Si using experimental values of its optical parameters, and obtainig very well agreement, even for the spectrum region with strong absorption. Then, using the same method, we computed the band structure for a two dimensional photonic crystal without absorption, formed by an square array of MgO cylinders in air. The optical parameters for MgO were modeled with the Lorentz dielectric function. Finally, we studied an array of MgO cylinders in a metal, using Drude model without absorption, for the metal dielectric function. For this last case, we study the gap-midgap ratio as a function of the filling fraction for both the square and triangular lattice. The gap-midgap ratio is larger for the triangular lattice, with a maximum value of 10% for a filling fraction of 0.6. Our results show that the method can be applied to dispersive materials, and then to a wide range of applications where photonic crystals can be used.

  18. Compensating for dispersion and the nonlinear Kerr effect without phase conjugation.

    PubMed

    Paré, C; Villeneuve, A; Bélanger, P A; Doran, N J

    1996-04-01

    We propose the use of a dispersive medium with a negative nonlinear refractive-index coefficient as a way to compensate for the dispersion and the nonlinear effects resulting from pulse propagation in an optical fiber. The undoing of pulse interaction might allow for increased bit rates. PMID:19865438

  19. Effective dispersion compensation of variable-linewidth fiber amplifier by single-multilayer dielectric grating

    NASA Astrophysics Data System (ADS)

    Zheng, Ye; Yang, Yifeng; Wang, Jianhua; Hu, Man; Liu, Guangbo; Chen, Xiaolong; Liu, Kai; Zhao, Chun; Gong, Weichao; Bai, Gang; Bai, Yang; He, Bing; Zhou, Jun

    2016-06-01

    We achieve effective dispersion compensation by employing a single-multilayer dielectric diffraction grating and a variable-linewidth fiber amplifier. Both theoretical and experimental studies on the diffracted beam quality have been performed. The experimental results show that when the linewidth reaches 0.41 nm the beam quality in the dispersive plane reduces dramatically from 5.4 for the first-time diffracted beam to 2.08 for the second-time diffracted beam. This dispersion compensation technology relaxes the requirement on the linewidth of the incident beam source, which is beneficial for high-brightness spectral beam combining.

  20. Dual-core chiral planar waveguide-based compact and efficient dispersion compensator

    NASA Astrophysics Data System (ADS)

    Iqbal, N.; Choudhury, P. K.

    2016-01-01

    The paper is devoted to the design of dispersion compensator comprised of dual-core planar chiral waveguide having different refractive indices, and cladded with homogeneous dielectric mediums. It has been found that the supermodes play vital role in tuning the group velocity dispersion (GVD) with the aid of chirality parameters, which is evident from the achieved giant GVD with narrow bandwidth. Apart from the material parameters, the effect of core spacing on the features of GVD is also investigated. It is expected that such dispersion compensators would be trendy and greatly useful in communication systems.

  1. Tailoring of nearly zero flattened dispersion photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Hsu, Jui-Ming

    2016-02-01

    This work theoretically tailored the dispersion in a photonic crystal fiber (PCF), and then designed two types of nearly zero dispersion flattened PCFs (DFPCFs) by rod-doping or liquid-filling some of the cladding holes. The numeric results show that the DFPCF type 1, rod-doped with arbitrary indices, achieves the dispersion values between 0±1 ps/nm km over a bandwidth range of 460 nm. The DFPCF type 2, filled with the available liquids, performs the dispersion values between 0±1.5 ps/nm km over a bandwidth range of 520 nm. Finally, the confinement losses of the two types of DFPCFs are estimated. The numeric results show that the confinement losses of the two types of the proposed DFPCFs are extremely low, in the order of 10-5 or 10-6 dB/km, which even can be disregarded.

  2. Experimental study of solitonic dispersive wave in photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Bose, Surajit; Roy, Samudra; Bhadra, Shyamal K.

    2015-06-01

    We experimentally observed the emission of phase-matched resonant radiation in the form of solitonic dispersive wave in a fabricated photonic crystal fiber by pumping picosecond and femtosecond pulses close to zero-dispersion wavelength in normal dispersion regime. The generation of such phase matched radiation does not require a soliton to be formed and red-shifted in nature. Shock front from the leading edge of the input pump initiates the resonant radiation. The radiation develops in the anomalous dispersion domain and found to be confined both in spectral and temporal domain. The resonance mechanism can be well explained from the numerical simulation governed by generalized nonlinear Schrödinger equation.

  3. Nucleon effects on the photon dispersion relations in matter

    NASA Astrophysics Data System (ADS)

    D'olivo, Juan Carlos; Nieves, José F.

    1998-03-01

    We calculate the nucleon contribution to the photon self-energy in a plasma, including the effect of the anomalous magnetic moment of the nucleons. General formulas for the transverse and longitudinal components of the self-energy are obtained and we give explicit results in various limits of physical interest. The formulas are relevant for the study of the photon dispersion relations and the dynamical susceptibility in a nuclear medium such as the core of a supernova, and has implications with regard to the recent suggestion that the Cherenkov process ν-->νγ can take place in such a system.

  4. Broadband dispersion-compensating fiber for high-bit-rate transmission network use

    NASA Astrophysics Data System (ADS)

    Semenov, V. A.; Belov, A. V.; Dianov, E. M.; Abramov, A. A.; Bubnov, M. M.; Semjonov, S. L.; Shchebunjaev, A. G.; Khopin, V. F.; Guryanov, A. N.; Vechkanov, N. N.

    1995-08-01

    The optimum refractive-index profile and drawing temperature were investigated so as to maximize the figure of merit for multicladding broadband dispersion-compensating fibers. Based on the results of the investigation, the authors have fabricated a highly bend-resistant fiber with a 92.6-ps/(nm dB) figure of merit using the modified chemical-vapor deposition method for dispersion compensation in the 1.5-1.6- mu m wavelength region. The manufactured dispersion compensator does not suffer bend loss at 1.55 mu m for curvatures of radia of 6.3 and 3.3 cm, and it has a 1.1-dB/km bend loss at a curvature of radius of 1.6 cm. Codoping the germanium silicate core with fluorine diminishes the optical loss down to 0.70 dB/km at a 1.55- mu m wavelength.

  5. Broadband dispersion-compensating fiber for high-bit-rate transmission network use.

    PubMed

    Semenov, V A; Belov, A V; Dianov, E M; Abramov, A A; Bubnov, M M; Semjonov, S L; Shchebunjaev, A G; Khopin, V F; Guryanov, A N; Vechkanov, N N

    1995-08-20

    The optimum refractive-index profile and drawing temperature were investigated so as to maximize the figure of merit for multicladding broadband dispersion-compensating fibers. Based on the results of the investigation, the authors have fabricated a highly bend-resistant fiber with a 92.6-ps/(nm dB) figure of merit using the modified chemical-vapor deposition method for dispersion compensation in the 1.5-1.6-µm wavelength region. The manufactured dispersion compensator does not suffer bend loss at 1.55 µm for curvatures of radia of 6.3 and 3.3 cm, and it has a 1.1-dB/km bend loss at a curvature of radius of 1.6 cm. Codoping the germanium silicate core with fluorine diminishes the optical loss down to 0.70 dB/km at a 1.55-µm wavelength. PMID:21060352

  6. Design and performance evaluation of a dispersion compensation unit using several chirping functions in a tanh apodized FBG and comparison with dispersion compensation fiber.

    PubMed

    Mohammed, Nazmi A; Solaiman, Mohammad; Aly, Moustafa H

    2014-10-10

    In this work, various dispersion compensation methods are designed and evaluated to search for a cost-effective technique with remarkable dispersion compensation and a good pulse shape. The techniques consist of different chirp functions applied to a tanh fiber Bragg grating (FBG), a dispersion compensation fiber (DCF), and a DCF merged with an optimized linearly chirped tanh FBG (joint technique). The techniques are evaluated using a standard 10 Gb/s optical link over a 100 km long haul. The linear chirp function is the most appropriate choice of chirping function, with a pulse width reduction percentage (PWRP) of 75.15%, lower price, and poor pulse shape. The DCF yields an enhanced PWRP of 93.34% with a better pulse quality; however, it is the most costly of the evaluated techniques. Finally, the joint technique achieved the optimum PWRP (96.36%) among all the evaluated techniques and exhibited a remarkable pulse shape; it is less costly than the DCF, but more expensive than the chirped tanh FBG. PMID:25322426

  7. Spectral-temporal analysis of dispersive wave generation in photonic crystal fibers of different dispersion slope

    NASA Astrophysics Data System (ADS)

    Yang, Hua; Han, Fang; Hu, Hui; Wang, Weibin; Zeng, Qilin

    2014-03-01

    Based on the generalized nonlinear Schrödinger equation, we present a numerical investigation of dispersive wave generation in photonic crystal fibers pumped with femtosecond pulses in the anomalous dispersion region. Both positive dispersion slope and negative dispersion slope for pump wavelength are studied. It is demonstrated that the wavelength of the dispersive wave can be blue-shifted or red-shifted relative to the center wavelength of the soliton, depending on the dispersion slope of the pump wavelength. The spectral-temporal dynamics of dispersive wave generation is shown using the cross-correlation frequency-resolved optical gating (X-FROG) technique, which is numerically computed with a windowed Fourier transform. Further, we find a phenomenon that the X-FROG spectrogram of the corresponding output signal exhibits a parabolic shape, which is consistent with the wavelength dependence of the group delay. In particular, the phenomenon of soliton trapping of the dispersive wave is observed with an increase of pump power.

  8. Achromatic flat optical components via compensation between structure and material dispersions

    NASA Astrophysics Data System (ADS)

    Li, Yang; Li, Xiong; Pu, Mingbo; Zhao, Zeyu; Ma, Xiaoliang; Wang, Yanqin; Luo, Xiangang

    2016-01-01

    Chromatism causes great quality degradation of the imaging system, especially for diffraction imaging. The most commonly method to overcome chromatism is refractive/diffractive hybrid optical system which, however, sacrifices the light weight and integration property of diffraction elements. A method through compensation between the structure dispersion and material dispersion is proposed to overcome the chromatism in flat integrated optical components. This method is demonstrated by making use of silver nano-slits waveguides to supply structure dispersion of surface plasmon polaritons (SPP) in metal-insulator-metal (MIM) waveguide to compensate the material dispersion of metal. A broadband deflector and lens are designed to prove the achromatic property of this method. The method demonstrated here may serve as a solution of broadband light manipulation in flat integrated optical systems.

  9. High gain Raman amplifier with inherent gain flattening and dispersion compensation

    NASA Astrophysics Data System (ADS)

    Kakkar, Charu; Thyagarajan, K.

    2005-06-01

    We report here an inherently gain-flattened, high-gain discrete Raman fiber amplifier design with 21 dB net gain (±1.4 dB gain ripple) over 25 nm bandwidth. The amplifier design is based on a W-shape highly nonlinear fiber, in which, optimized spectral variation of leakage loss has been used to achieve inherent gain flattening of Raman gain. The proposed fiber has an additional advantage of having a high negative dispersion coefficient (∼-84 ps/km nm) over the operating range of wavelength and thus the designed discrete amplifier module, based on this fiber, is also capable of compensating dispersion accumulated in one span (70 km) of transmission through G.652 fiber. Hence, the designed module is proposed as a composite amplifier and dispersion-compensating unit for 25 nm bandwidth, which is capable of handling both attenuation and dispersion of one span of G. 652 transmission.

  10. Achromatic flat optical components via compensation between structure and material dispersions

    PubMed Central

    Li, Yang; Li, Xiong; Pu, Mingbo; Zhao, Zeyu; Ma, Xiaoliang; Wang, Yanqin; Luo, Xiangang

    2016-01-01

    Chromatism causes great quality degradation of the imaging system, especially for diffraction imaging. The most commonly method to overcome chromatism is refractive/diffractive hybrid optical system which, however, sacrifices the light weight and integration property of diffraction elements. A method through compensation between the structure dispersion and material dispersion is proposed to overcome the chromatism in flat integrated optical components. This method is demonstrated by making use of silver nano-slits waveguides to supply structure dispersion of surface plasmon polaritons (SPP) in metal-insulator-metal (MIM) waveguide to compensate the material dispersion of metal. A broadband deflector and lens are designed to prove the achromatic property of this method. The method demonstrated here may serve as a solution of broadband light manipulation in flat integrated optical systems. PMID:26794855

  11. Achromatic flat optical components via compensation between structure and material dispersions.

    PubMed

    Li, Yang; Li, Xiong; Pu, Mingbo; Zhao, Zeyu; Ma, Xiaoliang; Wang, Yanqin; Luo, Xiangang

    2016-01-01

    Chromatism causes great quality degradation of the imaging system, especially for diffraction imaging. The most commonly method to overcome chromatism is refractive/diffractive hybrid optical system which, however, sacrifices the light weight and integration property of diffraction elements. A method through compensation between the structure dispersion and material dispersion is proposed to overcome the chromatism in flat integrated optical components. This method is demonstrated by making use of silver nano-slits waveguides to supply structure dispersion of surface plasmon polaritons (SPP) in metal-insulator-metal (MIM) waveguide to compensate the material dispersion of metal. A broadband deflector and lens are designed to prove the achromatic property of this method. The method demonstrated here may serve as a solution of broadband light manipulation in flat integrated optical systems. PMID:26794855

  12. Active compensation of large dispersion of femtosecond pulses for precision laser ranging.

    PubMed

    Lee, Sang-Hyun; Lee, Joohyung; Kim, Young-Jin; Lee, Keunwoo; Kim, Seung-Woo

    2011-02-28

    We describe an active way of compensation for large dispersion induced in the femtosecond light pulses travelling in air for laser ranging. The pulse duration is consistently regulated at 250 fs by dispersion control, allowing sub-micrometer resolution in measuring long distances by means of time-of-flight measurement. This method could facilitate more reliable applications of femtosecond pulses for satellite laser ranging, laser altimetry and active LIDAR applications. PMID:21369227

  13. Photon backscattering tissue characterization by energy dispersive spectroscopy evaluations.

    PubMed

    Tartari, A; Casnati, E; Fernandez, J E; Felsteiner, J; Baraldi, C

    1994-02-01

    Techniques for in vivo tissue characterization based on scattered photons have usually been confined to evaluating coherent and Compton peaks. However, information can also be obtained from the energy analysis of the Compton scattered distribution. This paper looks at the extension of a technique validated by the authors for characterizing tissues composed of low-atomic-number elements. To this end, an EDXRS (energy dispersive x-ray spectrometry) computer simulation procedure was performed and applied to test the validity of a figure of merit able to characterize binary compounds. This figure of merit is based on the photon fluence values in a restricted energy interval of the measured distribution of incoherently scattered photons. After careful experimental tests with 59.54 keV incident photons at scattering angles down to 60degrees, the simulation procedure was applied to quasi-monochromatic and polychromatic high-radiance sources. The results show that the characterization by the figure of merit, which operates satisfactorily with monochromatic sources, is unsatisfactory in the latter cases, which seem to favour a different parameter for compound characterization. PMID:15552121

  14. Compensation of nonlinear phase shifts with third-order dispersion in short-pulse fiber amplifiers.

    PubMed

    Zhou, Shian; Kuznetsova, Lyuba; Chong, Andy; Wise, Frank

    2005-06-27

    We show that nonlinear phase shifts and third-order dispersion can compensate each other in short-pulse fiber amplifiers. This compen-sation can be exploited in any implementation of chirped-pulse amplification, with stretching and compression accomplished with diffraction gratings, single-mode fiber, microstructure fiber, fiber Bragg gratings, etc. In particular, we consider chirped-pulse fiber amplifiers at wavelengths for which the fiber dispersion is normal. The nonlinear phase shift accumulated in the amplifier can be compensated by the third-order dispersion of the combination of a fiber stretcher and grating compressor. A numerical model is used to predict the compensation, and experimental results that exhibit the main features of the calculations are presented. In the presence of third-order dispersion, an optimal nonlinear phase shift reduces the pulse duration, and enhances the peak power and pulse contrast compared to the pulse produced in linear propagation. Contrary to common belief, fiber stretchers can perform as well or better than grating stretchers in fiber amplifiers, while offering the major practical advantages of a waveguide medium. PMID:19498473

  15. Correlated few-photon transport in one-dimensional waveguides: Linear and nonlinear dispersions

    SciTech Connect

    Roy, Dibyendu

    2011-04-15

    We address correlated few-photon transport in one-dimensional waveguides coupled to a two-level system (TLS), such as an atom or a quantum dot. We derive exactly the single-photon and two-photon current (transmission) for linear and nonlinear (tight-binding sinusoidal) energy-momentum dispersion relations of photons in the waveguides and compare the results for the different dispersions. A large enhancement of the two-photon current for the sinusoidal dispersion has been seen at a certain transition energy of the TLS away from the single-photon resonances.

  16. Higgs boson decay to two photons and dispersion relations

    NASA Astrophysics Data System (ADS)

    Melnikov, Kirill; Vainshtein, Arkady

    2016-03-01

    We discuss the computation of the Higgs boson decay amplitude to two photons through the W -loop using dispersion relations. The imaginary part of the form factor FW(s ) that parametrizes this decay is unambiguous in four dimensions. When it is used to calculate the unsubtracted dispersion integral, the finite result for the form factor FW(s ) is obtained. However, the FW(s ) obtained in this way differs by a constant term from the result of a diagrammatic computation, based on dimensional regularization. It is easy to accommodate the missing constant by writing a once-subtracted dispersion relation for FW(s ) but it is unclear why the subtraction needs to be done. The goal of this paper is to investigate this question in detail. We show that the correct constant can be recovered within a dispersive approach in a number of ways that, however, either require an introduction of an ultraviolet regulator or unphysical degrees of freedom; unregulated and unsubtracted computations in the unitary gauge are insufficient, in spite of the fact that such computations give a finite result.

  17. An Experiment of GMPLS-Based Dispersion Compensation Control over In-Field Fibers

    NASA Astrophysics Data System (ADS)

    Seno, Shoichiro; Horiuchi, Eiichi; Yoshida, Sota; Sugihara, Takashi; Onohara, Kiyoshi; Kamei, Misato; Baba, Yoshimasa; Kubo, Kazuo; Mizuochi, Takashi

    As ROADMs (Reconfigurable Optical Add/Drop Multiplexers) are becoming widely used in metro/core networks, distributed control of wavelength paths by extended GMPLS (Generalized MultiProtocol Label Switching) protocols has attracted much attention. For the automatic establishment of an arbitrary wavelength path satisfying dynamic traffic demands over a ROADM or WXC (Wavelength Cross Connect)-based network, precise determination of chromatic dispersion over the path and optimized assignment of dispersion compensation capabilities at related nodes are essential. This paper reports an experiment over in-field fibers where GMPLS-based control was applied for the automatic discovery of chromatic dispersion, path computation, and wavelength path establishment with dynamic adjustment of variable dispersion compensation. The GMPLS-based control scheme, which the authors called GMPLS-Plus, extended GMPLS's distributed control architecture with attributes for automatic discovery, advertisement, and signaling of chromatic dispersion. In this experiment, wavelength paths with distances of 24km and 360km were successfully established and error-free data transmission was verified. The experiment also confirmed path restoration with dynamic compensation adjustment upon fiber failure.

  18. Unified dispersive approach to real and virtual photon-photon scattering at low energy

    NASA Astrophysics Data System (ADS)

    Moussallam, B.

    2013-09-01

    Previous representations of pion-pair production amplitudes by two real photons at low energy, which combine dispersion theoretical constraints with elastic unitarity, chiral symmetry and soft-photon constraints are generalised to the case where one photon is virtual. The constructed amplitudes display explicitly the dependence on the ππ phase-shifts, on pion form factors and on pion polarisabilities. They apply both for space-like and time-like virtualities despite the apparent overlap of the left- and right-hand cuts, by implementing a definition of resonance exchange amplitudes complying with analyticity and consistent limiting prescriptions for the energy variables. Applications are made to the pion generalised polarisabilies, to vector-meson radiative decays, and to the σγ electromagnetic form factor. Finally, an evaluation of the contribution of γππ states in the hadronic vacuum polarisation to the muon g-2 is given, which should be less model dependent than previous estimates.

  19. Numerical compensation of system polarization mode dispersion in polarization-sensitive optical coherence tomography

    PubMed Central

    Zhang, Ellen Ziyi; Oh, Wang-Yuhl; Villiger, Martin L.; Chen, Liang; Bouma, Brett E.; Vakoc, Benjamin J.

    2013-01-01

    Polarization mode dispersion (PMD), which can be induced by circulators or even moderate lengths of optical fiber, is known to be a dominant source of instrumentation noise in fiber-based PS-OCT systems. In this paper we propose a novel PMD compensation method that measures system PMD using three fixed calibration signals, numerically corrects for these instrument effects and reconstructs an improved sample image. Using a frequency multiplexed PS-OFDI setup, we validate the proposed method by comparing birefringence noise in images of intralipid, muscle, and tendon with and without PMD compensation. PMID:23389009

  20. Supercontinuum generation at 800 nm in all-normal dispersion photonic crystal fiber.

    PubMed

    Sukhoivanov, Igor A; Iakushev, Sergii O; Shulika, Oleksiy V; AndradeLucio, Jose Amparao; Díez, Antonio; Andrés, Miguel

    2014-12-01

    We have numerically investigated the supercontinuum generation and pulse compression in a specially designed all-normal dispersion photonic crystal fiber with a flat-top dispersion curve, pumped by typical pulses from state of the art Ti:Sapphire lasers at 800 nm. The optimal combination of pump pulse parameters for a given fiber was found, which provides a wide octave-spanning spectrum with superb spectral flatness (a drop in spectral intensity of ~1.7 dB). With regard to the pulse compression for these spectra, multiple-cycle pulses (~8 fs) can be obtained with the use of a simple quadratic compressor and nearly single-cycle pulses (3.3 fs) can be obtained with the application of full phase compensation. The impact of pump pulse wavelength-shifting relative to the top of the dispersion curve on the generated SC and pulse compression was also investigated. The optimal pump pulse wavelength range was found to be 750 nm < λp < 850 nm, where the distortions of pulse shape are quite small (< -3.3 dB). The influences of realistic fiber fabrication errors on the SC generation and pulse compression were investigated systematically. We propose that the spectral shape distortions generated by fiber fabrication errors can be significantly attenuated by properly manipulating the pump. PMID:25606954

  1. Management of residual dispersion of an optical transmission system using octagonal photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Mahmud, Russel Reza; Goffar Khan, Muhammad Abdul; Razzak, S. M. Abdur

    2016-04-01

    An octagonal photonic crystal fiber (O-PCF) for numerical structure design and analysis of some particular properties are presented in this paper. The proposed design is suitable for residual dispersion compensation (RDC) with polarization maintaining (PM) applications as it offers extremely high-negative flattened average chromatic dispersion (DT) and absolute dispersion variation (ΔD) of around -(708±10) ps nm-1 km-1 and average high birefringence (B) of the order 10-2 for the wavelength limits of 1.46 to 1.67 μm (bandwidth of 210 nm that covers S+C+L+U bands in the infrared region of the optical third window). In addition, it exhibits very low confinement loss of 10-3.5 to 10-2.5 dB/m for that bandwidth. Moreover, to evaluate the sensitivity of the fiber properties (DT and B) during fabrication, ±0.02 μm variation in the optimum parameters is also studied.

  2. Investigation of 2D laterally dispersive photonic crystal structures : LDRD 33602 final report.

    SciTech Connect

    Subramania,Ganapathi Subramanian; Vawter, Gregory Allen; Wendt, Joel Robert; Peake, Gregory Merwin; Guo, Junpeng; Peters, David William; Hadley, G. Ronald

    2003-12-01

    Artificially structured photonic lattice materials are commonly investigated for their unique ability to block and guide light. However, an exciting aspect of photonic lattices which has received relatively little attention is the extremely high refractive index dispersion within the range of frequencies capable of propagating within the photonic lattice material. In fact, it has been proposed that a negative refractive index may be realized with the correct photonic lattice configuration. This report summarizes our investigation, both numerically and experimentally, into the design and performance of such photonic lattice materials intended to optimize the dispersion of refractive index in order to realize new classes of photonic devices.

  3. Vector-dispersion compensation and pulse pedestal cancellation in a femtosecond nonlinear amplification fiber laser system.

    PubMed

    Xie, Chen; Liu, Bowen; Niu, Hailiang; Song, Youjian; Li, Yi; Hu, Minglie; Zhang, Yueguang; Shen, Weidong; Liu, Xu; Wang, Chingyue

    2011-11-01

    We report on a femtosecond nonlinear amplification fiber laser system using a vector-dispersion compressor, which consists of a transmission grating pair and multipass cell based Gires-Tournois interferometer mirrors. The mirror is designed with nearly zero group-delay dispersion and large negative third-order dispersion. As a result, the third-order dispersion of the compressor can be adjusted independently to compensate the nonlinear phase shift of amplified pulses to reduce the pulse pedestal. With this scheme, the system outputs 44  fs laser pulses with little wing at 26.6  W output average power and 531  nJ pulse energy, corresponding to 10.8  MW peak power. PMID:22048347

  4. Increased range of ultrasonic guided wave testing of overhead transmission line cables using dispersion compensation.

    PubMed

    Legg, Mathew; Yücel, Mehmet K; Kappatos, Vassilios; Selcuk, Cem; Gan, Tat-Hean

    2015-09-01

    Overhead Transmission Line (OVTL) cables can experience structural defects and are, therefore, inspected using Non-Destructive Testing (NDT) techniques. Ultrasonic Guided Waves (UGW) is one NDT technique that has been investigated for inspection of these cables. For practical use, it is desirable to be able to inspect as long a section of cable as possible from a single location. This paper investigates increasing the UGW inspection range on Aluminium Conductor Steel Reinforced (ACSR) cables by compensating for dispersion using dispersion curve data. For ACSR cables, it was considered to be difficult to obtain accurate dispersion curves using modelling due to the complex geometry and unknown coupling between wire strands. Group velocity dispersion curves were, therefore, measured experimentally on an untensioned, 26.5m long cable and a method of calculating theoretical dispersion curves was obtained. Attenuation and dispersion compensation were then performed for a broadband Maximum Length Sequence (MLS) excitation signal. An increase in the Signal to Noise Ratio (SNR) of about 4-8dB compared to that of the dispersed signal was obtained. However, the main benefit was the increased ability to resolve the individual echoes from the end of the cable and an introduced defect in the form of a cut, which was 7 to at least 13dB greater than that of the dispersed signal. Five echoes were able to be clearly detected using MLS excitation signal, indicating the potential for an inspection range of up to 130m in each direction. To the best of the authors knowledge, this is the longest inspection range for ACSR cables reported in the literature, where typically cables, which were only one or two meter long, have been investigated previously. Narrow band tone burst and Hann windowed tone burst excitation signal also showed increased SNR and ability to resolve closely spaced echoes. PMID:25991388

  5. Pulsed bismuth fibre laser with the intracavity-compensated group velocity dispersion

    SciTech Connect

    Krylov, Aleksandr A; Kryukov, P G; Dianov, Evgenii M; Okhotnikov, O G; Guina, M

    2009-01-31

    Passive mode locking is achieved in a bismuth-doped fibre laser with the help of a SESAM saturable absorber optimised for operation in the spectra range from 1100 to 1200 nm. Pumping was performed by a 2-W cw ytterbium fibre laser at 1075 nm. The oscillation of the laser with an intracavity group-velocity-dispersion compensator based on a pair of diffraction gratings is studied. Laser pulses with the minimum duration of {approx}5 ps are generated. (lasers)

  6. The key to OC-192 deployment dispersion compensation using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Su, C.; Kung, Peter; Loh, W. H.

    1998-12-01

    The effects and characteristics of group delay ripple of chirped fiber gratings on the performance of a 10 Gb/s NRZ transmission system has been experimentally investigated. For the power penalty less than 1 dB at bit-error-rate of 10-9, our experiment results show that the ripple magnitude of dispersion compensating gratings should be less than +/- 20 ps within its pass-band for 10 Gb/s systems.

  7. Electronic dispersion compensation for PMD in 40-GB/s optical links

    NASA Astrophysics Data System (ADS)

    Yang, Kang; Liu, Jianfei; Zeng, Xiangye

    2009-11-01

    In 40-Gb/s optical systems, it is impossible to neglect the electronic dispersion of polarization-mode dispersion (PMD). As the data rate is increased, the maximum useful length of the fiber decreases according to the square of the increase. With the development of VLSI and DSP technologies, the electronic dispersion compensation for optical network has aroused greater world attention. In this paper, the performance of decision feedback equalizer (DFE) in PMD-limited 40-GB/s optical links is analyzed by using Matlab/Simulink. A simple equalizer circuit, in fold-cascade traveling-wave filter topology, is presented and the results based on S-parameter simulations show that a DFE equalizer consisting of a 3-tap feed forward equalizer (FFE) and a 2-tap feed back equalizer (FBE) can mitigate PMD effectively.

  8. Chromatic dispersion and nonlinear phase noise compensation based on KLMS method

    NASA Astrophysics Data System (ADS)

    Nouri, Mahdi; Shayesteh, Mahrokh G.; Farhangian, Nooshin

    2015-09-01

    In this study, kernel least mean square (KLMS) algorithm with fractionally spaced equalizing structure is proposed for electrical compensation of chromatic dispersion (CD) and nonlinear phase noise (NLPN) in a dual polarization optical communications system with coherent detection. We consider single mode fiber channel. At the receiver, the additive optical noise is represented as additive white Gaussian noise. Phase modification is utilized at high signal powers to maintain the validity of Gaussian model of noise. We consider QAM and PSK modulations and evaluate the performance of the proposed method in terms of error rate, phase error, and error vector magnitude (EVM). The results are obtained in both linear and nonlinear regimes. In the linear region, the KLMS algorithm can compensate CD and NLPN effectively and outperforms the existing compensation methods such as LMS, minimum mean square error (MMSE), and time domain FIR filter. In nonlinear regime, where the input power is higher, NLPN is stronger which results in compensation performance degradation. However, KLMS still achieves better results than the above algorithms.

  9. Extending of flat normal dispersion profile in all-solid soft glass nonlinear photonic crystal fibres

    NASA Astrophysics Data System (ADS)

    Siwicki, Bartłomiej; Kasztelanic, Rafał; Klimczak, Mariusz; Cimek, Jarosław; Pysz, Dariusz; Stępień, Ryszard; Buczyński, Ryszard

    2016-06-01

    The bandwidth of coherent supercontinuum generated in optical fibres is strongly determined by the all-normal dispersion characteristic of the fibre. We investigate all-normal dispersion limitations in all-solid oxide-based soft glass photonic crystal fibres with various relative inclusion sizes and lattice constants. The influence of material dispersion on fibre dispersion characteristics for a selected pair of glasses is also examined. A relation between the material dispersion of the glasses and the fibre dispersion has been described. We determined the parameters which limit the maximum range of flattened all-normal dispersion profile achievable for the considered pair of heavy-metal-oxide soft glasses.

  10. A Study of Dispersion Compensation of Polarization Multiplexing-Based OFDM-OCDMA for Radio-over-Fiber Transmissions.

    PubMed

    Yen, Chih-Ta; Chen, Wen-Bin

    2016-01-01

    Chromatic dispersion from optical fiber is the most important problem that produces temporal skews and destroys the rectangular structure of code patterns in the spectra-amplitude-coding-based optical code-division multiple-access (SAC-OCDMA) system. Thus, the balance detection scheme does not work perfectly to cancel multiple access interference (MAI) and the system performance will be degraded. Orthogonal frequency-division multiplexing (OFDM) is the fastest developing technology in the academic and industrial fields of wireless transmission. In this study, the radio-over-fiber system is realized by integrating OFDM and OCDMA via polarization multiplexing scheme. The electronic dispersion compensation (EDC) equalizer element of OFDM integrated with the dispersion compensation fiber (DCF) is used in the proposed radio-over-fiber (RoF) system, which can efficiently suppress the chromatic dispersion influence in long-haul transmitted distance. A set of length differences for 10 km-long single-mode fiber (SMF) and 4 km-long DCF is to verify the compensation scheme by relative equalizer algorithms and constellation diagrams. In the simulation result, the proposed dispersion mechanism successfully compensates the dispersion from SMF and the system performance with dispersion equalizer is highly improved. PMID:27618042

  11. Multi-channel nonlinearity compensation of PDM-QPSK signals in dispersion-managed transmission using dispersion-folded digital backward propagation.

    PubMed

    Xia, Cen; Liu, Xiang; Chandrasekhar, S; Fontaine, N K; Zhu, Likai; Li, G

    2014-03-10

    We demonstrate nonlinearity compensation of 37.5-GHz-spaced 128-Gb/s PDM-QPSK signals using dispersion-folded digital-backward-propagation and a spectrally-sliced receiver that simultaneously receives three WDM signals, showing mitigation of intra-channel and inter-channel nonlinear effects in a 2560-km dispersion-managed TWRS-fiber link. Intra-channel and adjacent inter-channel nonlinear compensation gains when WDM channels are fully populated in the C-band are estimated based on the GN-model. PMID:24663923

  12. Design of a broadband highly dispersive pure silica photonic crystal fiber.

    PubMed

    Subbaraman, Harish; Ling, Tao; Jiang, YongQiang; Chen, Maggie Y; Cao, Peiyan; Chen, Ray T

    2007-06-01

    A highly dispersive dual-concentric-core pure silica photonic crystal fiber is designed with a maximum chromatic dispersion value of about -9500 ps/(nm km) around the 1.56 microm wavelength region and a full width at half-maximum (FWHM) of 55 nm. The change in the dispersion-bandwidth product as a function of period is carefully studied by using the plane wave expansion method. The coupled mode theory matches well with the plane wave expansion method that was used to simulate the chromatic dispersion. This kind of a photonic crystal fiber structure is suitable for high-dispersion application in phased array antenna systems based on photonic crystal fiber arrays. PMID:17514284

  13. Gain dispersion in Visible Light Photon Counters as a function of counting rate

    SciTech Connect

    Bross, A.; Buscher, V.; Estrada, J.; Ginther, G.; Molina, J.; /Rio de Janeiro State U.

    2005-03-01

    We present measurements of light signals using Visible Light Photon Counters (VLPC), that indicate an increase in gain dispersion as the counting rate increases. We show that this dispersion can be understood on the basis of a recent observation of localized field reduction in VLPCs at high input rates.

  14. 1.55- μm supercontinuum based on dispersion-flattened photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Xu, Yong-Zhao; Huang, Yong-Qing; Ren, Xiao-Min

    2007-09-01

    A dispersion-flattened photonic crystal fiber with normal dispersion is designed for generating flat wideband supercontinuum, and the supercontinuum generation in this fiber is numerically analyzed. The results show that by appropriately designing the photonic crystal fiber, it can achieve flattened dispersion in the normal dispersion region. It is found that a fiber characterized by a flattened dispersion with a small normal dispersion is suitable for a flat wideband supercontinuum generation. In the process of spectral broadening, self-phase modulation effect plays a dominant role. By filtering the supercontinuum, pulses with different central wavelength over a wide spectral range can be obtained. The pulse width is determined by the bandwidth of the filter.

  15. Single sub-50-attosecond pulse generation from chirp-compensated harmonic radiation using material dispersion

    SciTech Connect

    Kim, Kyung Taec; Kim, Chul Min; Umesh, G.; Nam, Chang Hee; Baik, Moon-Gu

    2004-05-01

    A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization and hence experience a large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with a duration less than 50 as.

  16. Slow light with low group-velocity dispersion at the edge of photonic graphene

    SciTech Connect

    Ouyang Chunfang; Dong Biqin; Liu Xiaohan; Zi Jian; Xiong Zhiqiang; Zhao Fangyuan; Hu Xinhua

    2011-07-15

    We theoretically study the light propagation at the zigzag edges of a honeycomb photonic crystal (PC), or photonic graphene. It is found that the corresponding edge states have a sinusoidal dispersion similar to those found in PC coupled resonator optical waveguides [CROWs; M. Notomi et al., Nature Photon. 2, 741 (2008)]. The sinusoidal dispersion curve can be made very flat by carefully tuning edge parameters. As a result, low group velocity and small group velocity dispersion can be simultaneously obtained for light propagating at the zigzag edge of photonic graphene. Compared with PC CROWs, our slow-light system exhibits no intrinsic radiation loss and has a larger group velocity bandwidth product. Our results could find applications in on-chip optical buffers and enhanced light-matter interaction.

  17. Slow light and chromatic temporal dispersion in photonic crystal waveguides using femtosecond time of flight.

    PubMed

    Finlayson, C E; Cattaneo, F; Perney, N M B; Baumberg, J J; Netti, M C; Zoorob, M E; Charlton, M D B; Parker, G J

    2006-01-01

    We report time-of-flight experiments on photonic-crystal waveguide structures using optical Kerr gating of a femtosecond white-light supercontinuum. These photonic-crystal structures, based on engineered silicon-nitride slab waveguides, possess broadband low-loss guiding properties, allowing the group velocity dispersion of optical pulses to be directly tracked as a function of wavelength. This dispersion is shown to be radically disrupted by the spectral band gaps associated with the photonic-crystal periodicity. Increased time-of-flight effects, or "slowed light," are clearly observed at the edges of band gaps in agreement with two-dimensional plane-wave theoretical models of group velocity dispersion. A universal model for slow light in such photonic crystals is proposed, which shows that slow light is controlled predominantly by the detuning from, and the size of, the photonic band gaps. Slowed light observed up to time delays of approximately 1 ps, corresponds to anomalous dispersion of approximately 3.5 ps/nm per mm of the photonic crystal structure. From the decreasing intensity of time-gated slow light as a function of time delay, we estimate the characteristic losses of modes which are guided in the spectral proximity of the photonic band gaps. PMID:16486307

  18. An alternative approach to compensators design for photon beams used in radiotherapy

    NASA Astrophysics Data System (ADS)

    Jurković, S.; Žauhar, G.; Bistrović, M.; Faj, D.; Kaliman, Z.; Smilović Radojčić, Đ.

    2007-09-01

    The use of compensators in order to achieve desired dose distribution has a long history and is a well-established technique in radiation therapy planning. There are several different calculation methods for determining a compensator's thickness. An alternative method that is based on the Cunningham's modification of Clarkson's method to calculate scattered radiation in beams with an inhomogeneous cross-section is proposed. It is well known that the total dose distribution of radiotherapy photon beam consists of the contributions of the primary beam, attenuated by the tissue layer, and the scattered radiation generated by the primary radiation in single and multiple photon scatter events. The scattered component can be represented as a function of the primary radiation. The central point of our method is the numerical estimation of the primary distribution required to achieve the desired total distribution. Now using the calculated primary distribution, the shape of the modulator could be determined. In this way the contribution of the scattered component is validated in a more accurate way than using effective attenuation coefficients, which is a common practice. The method is verified in various clinical situations and compared with the standard method. The accuracy, although dependent on geometry, was improved by at least 2%. With more complex geometries there is an even higher gain in accuracy with our method when compared to the standard method.

  19. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals

    PubMed Central

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-01-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals. PMID:26956377

  20. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals.

    PubMed

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-01-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals. PMID:26956377

  1. Full Polarization Conical Dispersion and Zero-Refractive-Index in Two-Dimensional Photonic Hypercrystals

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Rong; Chen, Xiao-Dong; Zhao, Fu-Li; Dong, Jian-Wen

    2016-03-01

    Photonic conical dispersion has been found in either transverse magnetic or transverse electric polarization, and the predominant zero-refractive-index behavior in a two-dimensional photonic crystal is polarization-dependent. Here, we show that two-dimensional photonic hypercrystals can be designed that exhibit polarization independent conical dispersion at the Brillouin zone center, as two sets of triply-degenerate point for each polarization are accidentally at the same Dirac frequency. Such photonic hypercrystals consist of periodic dielectric cylinders embedded in elliptic metamaterials, and can be viewed as full-polarized near zero-refractive-index materials around Dirac frequency by using average eigen-field evaluation. Numerical simulations including directional emissions and invisibility cloak are employed to further demonstrate the double-zero-index characteristics for both polarizations in the photonic hypercrystals.

  2. Brewster-angled chirped mirrors for high-fidelity dispersion compensation and bandwidths exceeding one optical octave

    NASA Astrophysics Data System (ADS)

    Steinmeyer, G.

    2003-09-01

    A novel design approach for dispersion-compensating chirped mirrors with greater-than-octave bandwidth is proposed. The commonly encountered problem of dispersion ripple is overcome by impedance matching via Brewster incidence in respect to the top-layer coating material. This approach totally suppresses undesired reflections off the interface to the ambient medium without any need for complicated matching sections. It is shown that Brewster-angled chirped mirrors can deliver ultrabroadband dispersion compensation over a much wider bandwidth than conventional doublechirped mirrors and without the mechanical complexity of back-deposition approaches. Due to their relatively simple structure, the sensitivity of the dispersion of the Brewster-angled designs towards growth errors is greatly reduced. Therefore, this new generation of chirped mirrors appears ideal for compression of continuum pulses with a potential of pulse durations in the single-cycle regime.

  3. Dispersion compensation in an Yb-doped fiber oscillator for generating transform-limited, wing-free pulses.

    PubMed

    Kurita, Takashi; Yoshida, Hidetsugu; Furuse, Hiroaki; Kawashima, Toshiyuki; Miyanaga, Noriaki

    2011-12-01

    We investigate the effect of dispersion compensation on temporal characteristics in mode-locking by nonlinear polarization rotation in an ytterbium-doped fiber (YDF) oscillator with intracavity and external grating pairs. A short fixed length YDF was spliced with a longer single-mode fiber (SMF). Using experimentally measured dispersion characteristics of the YDF, SMF and cavity optics, we control the group velocity dispersion (GVD) and spectral broadening in a cavity by changing the SMF length. As a result, the oscillator generated 29.4-fs transform-limited wing-free pulses, which are to our knowledge the shortest and cleanest pulses achieved without the use of additional optics like a prism pair for high-order dispersion compensation. The results show that a precise balance of higher order terms of the GVD and self-phase modulation is essential for shortening pulse duration. PMID:22273911

  4. Method based on chirp decomposition for dispersion mismatch compensation in precision absolute distance measurement using swept-wavelength interferometry.

    PubMed

    Lu, Cheng; Liu, Guodong; Liu, Bingguo; Chen, Fengdong; Hu, Tao; Zhuang, Zhitao; Xu, Xinke; Gan, Yu

    2015-12-14

    We establish a theoretical model of dispersion mismatch in absolute distance measurements using swept-wavelength interferometry (SWI) and propose a novel dispersion mismatch compensation method called chirp decomposition. This method separates the dispersion coefficient and distance under test, which ensures dispersion mismatch compensation without introducing additional random errors. In the measurement of a target located at 3.9 m, a measurement resolution of 45.9 μm is obtained, which is close to the theoretical resolution, and a standard deviation of 0.74 μm is obtained, which is better than the traditional method. The measurement results are compared to a single-frequency laser interferometer. The target moves from 1 m to 3.7 m, and the measurement precision using the new method is less than 0.81 μm. PMID:26698959

  5. Single photon energy dispersive x-ray diffraction

    SciTech Connect

    Higginbotham, Andrew; Patel, Shamim; Ciricosta, Orlando; Suggit, Matthew J.; Wark, Justin S.; Hawreliak, James A.; Collins, Gilbert W.; Coppari, Federica; Eggert, Jon H.; Tang, Henry

    2014-03-15

    With the pressure range accessible to laser driven compression experiments on solid material rising rapidly, new challenges in the diagnosis of samples in harsh laser environments are emerging. When driving to TPa pressures (conditions highly relevant to planetary interiors), traditional x-ray diffraction techniques are plagued by increased sources of background and noise, as well as a potential reduction in signal. In this paper we present a new diffraction diagnostic designed to record x-ray diffraction in low signal-to-noise environments. By utilising single photon counting techniques we demonstrate the ability to record diffraction patterns on nanosecond timescales, and subsequently separate, photon-by-photon, signal from background. In doing this, we mitigate many of the issues surrounding the use of high intensity lasers to drive samples to extremes of pressure, allowing for structural information to be obtained in a regime which is currently largely unexplored.

  6. Few-photon scattering in dispersive waveguides with multiple qubits.

    PubMed

    Ekin Kocabaş, Şükrü

    2016-06-01

    We extend the Krylov-subspace-based time-dependent numerical simulation technique for a qubit interacting with photons in a waveguide to the multiple qubit case. We analyze photon scattering from two qubits and derive expressions for the bound states in the continuum (BICs). We show how the BIC can be excited. We use the BIC in a recent Pauli-Z gate proposal involving decoherence free subspaces and obtain the gate fidelity as a function of the gate parameters. The techniques presented in this Letter are useful for investigating the time evolution of quantum gates and other many-body systems with multiple quenches in the Hamiltonian. PMID:27244407

  7. Few-photon scattering in dispersive waveguides with multiple qubits

    NASA Astrophysics Data System (ADS)

    Ekin Kocabaş, Şükrü

    2016-06-01

    We extend the Krylov-subspace based time-dependent numerical simulation technique for a qubit interacting with photons in a waveguide to the multiple qubit case. We analyze photon scattering from two qubits analytically and derive expressions for the bound states in the continuum (BIC). We show how the BIC can be excited. We use the BIC in a recent Pauli-Z gate proposal involving decoherence free subspaces and obtain the gate fidelity as a function of the gate parameters. The techniques presented in the paper are useful for investigating the time evolution of quantum gates and other many-body systems with multiple quenches in the Hamiltonian.

  8. Tunable delay control of entangled photons based on dispersion cancellation.

    PubMed

    Odele, Ogaga D; Lukens, Joseph M; Jaramillo-Villegas, Jose A; Langrock, Carsten; Fejer, Martin M; Leaird, Daniel E; Weiner, Andrew M

    2015-08-24

    We propose and demonstrate a novel approach for controlling the temporal position of the biphoton correlation function using pump frequency tuning and dispersion cancellation; precise waveguide engineering enables biphoton generation at different pump frequencies while the idea of nonlocal dispersion cancellation is used to create the relative signal-idler delay and simultaneously prevents broadening of their correlation. Experimental results for delay shifts up to ±15 times the correlation width are shown along with discussions of the performance metrics of this approach. PMID:26368161

  9. Nonlinear wavelength conversion in photonic crystal fibers with three zero-dispersion points

    SciTech Connect

    Stark, S. P.; Biancalana, F.; Podlipensky, A.; St. J. Russell, P.

    2011-02-15

    In this theoretical study, we show that a simple endlessly single-mode photonic crystal fiber can be designed to yield, not just two, but three zero-dispersion wavelengths. The presence of a third dispersion zero creates a rich phase-matching topology, enabling enhanced control over the spectral locations of the four-wave-mixing and resonant-radiation bands emitted by solitons and short pulses. The greatly enhanced flexibility in the positioning of these bands has applications in wavelength conversion, supercontinuum generation, and pair-photon sources for quantum optics.

  10. Photon-counting CT: modeling and compensating of spectral distortion effects

    NASA Astrophysics Data System (ADS)

    Cammin, Jochen; Kappler, Steffen; Weidinger, Thomas; Taguchi, Katsuyuki

    2015-03-01

    Spectral computed tomography (CT) with photon-counting detectors (PCDs) has the potential to substantially advance diagnostic CT imaging by reducing image noise and dose to the patient, by improving contrast and tissue specificity, and by enabling molecular and functional imaging. However, the current PCD technology is limited by two main factors: imperfect energy measurement (spectral response effects, SR) and count rate non-linearity (pulse pileup effects, PP, due to detector deadtimes) resulting in image artifacts and quantitative inaccuracies for material specification. These limitations can be lifted with image reconstruction algorithms that compensate for both SR and PP. A prerequisite for this approach is an accurate model of the count losses and spectral distortions in the PCD. In earlier work we developed a cascaded SR-PP model and evaluated it using a physical PCD. In this paper we show the robustness of our approach by modifying the cascaded SR-PP model for a faster PCD with smaller pixels and a different pulse shape. We compare paralyzable and non-paralyzable detector models. First, the SR-PP model is evaluated at low and high count rates using two sets of attenuators. Then, the accuracy of the compensation is evaluated by estimating the thicknesses of three basis functions.

  11. Spectral response compensation for photon-counting clinical x-ray CT using sinogram restoration

    NASA Astrophysics Data System (ADS)

    Srivastava, Somesh; Cammin, Jochen; Fung, George S. K.; Tsui, Benjamin M. W.; Taguchi, Katsuyuki

    2012-03-01

    The x-ray spectrum recorded by a photon-counting x-ray detector (PCXD) is distorted due to the following physical effects which are independent of the count rate: finite energy-resolution, Compton scattering, charge-sharing, and Kescape. If left uncompensated, the spectral response (SR) of a PCXD due to the above effects will result in image artifacts and inaccurate material decomposition. We propose a new SR compensation (SRC) algorithm using the sinogram restoration approach. The two main contributions of our proposed algorithm are: (1) our algorithm uses an efficient conjugate gradient method in which the first and second derivatives of the cost functions are directly calculated analytically, whereas a slower optimization method that requires numerous function evaluations was used in other work; (2) our algorithm guarantees convergence by combining the non-linear conjugate gradient method with line searches that satisfy Wolfe conditions, whereas the algorithm in other work is not backed by theorems from optimization theory to guarantee convergence. In this study, we validate the performance of the proposed algorithm using computer simulations. The bias was reduced to zero from 11%, and image artifacts were removed from the reconstructed images. Quantitative K-edge imaging in possible only when SR compensation is done.

  12. Energy dispersive photon counting detectors for breast imaging

    NASA Astrophysics Data System (ADS)

    Barber, William C.; Wessel, Jan C.; Malakhov, Nail; Wawrzyniak, Gregor; Hartsough, Neal E.; Gandhi, Thulasidharan; Nygard, Einar; Iwanczyk, Jan S.

    2013-09-01

    We report on our efforts toward the development of silicon (Si) strip detectors for energy-resolved clinical breast imaging. Typically, x-ray integrating detectors based on scintillating cesium iodide CsI(Tl) or amorphous selenium (a- Se) are used in most commercial systems. Recently, mammography instrumentation has been introduced based on photon counting silicon Si strip detectors. Mammography requires high flux from the x-ray generator, therefore, in order to achieve energy resolved single photon counting, a high output count rate (OCR) for the detector must be achieved at the required spatial resolution and across the required dynamic range for the application. The required performance in terms of the OCR, spatial resolution, and dynamic range must be obtained with sufficient field of view (FOV) for the application thus requiring the tiling of pixel arrays and scanning techniques. Room temperature semiconductors, operating as direct conversion x-ray sensors, can provide the required speed when connected to application specific integrated circuits (ASICs) operating at fast peaking times with multiple fixed thresholds per pixel, provided that the sensors are designed for rapid signal formation across the x-ray energy ranges of the application at the required energy and spatial resolutions. We present our methods and results from the optimization of prototype detectors based on Si strip structures. We describe the detector optimization and the development of ASIC readout electronics that provide the required spatial resolution, low noise, high count rate capabilities and minimal power consumption.

  13. Supercontinuum generated in a dispersion-flattened photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Li, Xingliang; Zhang, Shumin; Han, Mengmeng; Zhang, Huaxing; Yang, Hong; Yuan, Ting

    2014-11-01

    We have experimentally investigated supercontinuum generated by using different pulse dynamics patterns as the pump pulses. These patterns, which include conventional mode-locked single pulse, condensed phase pulses and pulsed bunches, were all directly produced from a mode-locked erbium-doped fiber laser based on a multi-layer graphene saturable absorber. The strong third-order optical nonlinearity of graphene and all fiber cavity configuration led to the multi-pulses operation states at a low pump power. A flat supercontinuum with 20-dB width of 550 nm from 1200 nm to 1750 nm have all been obtained by seeding the amplified conventional mode-locked single pulse and condensed phase pulses into a segment of photonic crystal fiber. On the other hand, experimental results also show that the pulsed bunches was not conducive to form a flat supercontinuum.

  14. Multipole study of dispersion and structural losses of photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Kuhlmey, Boris T.; Renversez, G.; Maystre, Daniel R.; White, T.; McPhedran, Ross C.; Botten, Lindsay C.; de Sterke, Martijn

    2002-04-01

    We describe a multipole theory of photonic crystal or more generally microstructured optical fibers (MOF). We review basic MOF properties such-as losses and number of modes-obtained with our method and expose considerations and results on dispersion management taking into account the losses.

  15. Effects of modal dispersion on few-photon-qubit scattering in one-dimensional waveguides

    NASA Astrophysics Data System (ADS)

    Kocabaş, Şükrü Ekin

    2016-03-01

    We study one- and two-photon scattering from a qubit embedded in a one-dimensional waveguide in the presence of modal dispersion. We use a resolvent based analysis and utilize techniques borrowed from the Lee model studies. Modal dispersion leads to atom-photon bound states which necessitate the use of multichannel scattering theory. We present multichannel scattering matrix elements in terms of the solution of a Fredholm integral equation of the second kind. Through the use of the Lippmann-Schwinger equation, we derive an infinite series of Feynman diagrams that represent the solution to the integral equation. We use the Feynman diagrams as vertex correction terms to come up with closed-form formulas that successfully predict the trapping rate of a photon in the atom-photon bound state. We verify our formalism through Krylov-subspace based numerical studies with pulsed excitations. Our results provide the tools to calculate the complex correlations between scattered photons in a dispersive environment.

  16. Analysis of photonic band gap in dispersive properties of tunable three-dimensional photonic crystals doped by magnetized plasma

    SciTech Connect

    Zhang HaiFeng; Liu Shaobin; Yang Huan; Kong Xiangkun

    2013-03-15

    In this paper, the magnetooptical effects in dispersive properties for two types of three-dimensional magnetized plasma photonic crystals (MPPCs) containing homogeneous dielectric and magnetized plasma with diamond lattices are theoretically investigated for electromagnetic (EM) wave based on plane wave expansion (PWE) method, as incidence EM wave vector is parallel to the external magnetic field. The equations for two types of MPPCs with diamond lattices (dielectric spheres immersed in magnetized plasma background or vice versa) are theoretically deduced. The influences of dielectric constant, plasma collision frequency, filling factor, the external magnetic field, and plasma frequency on the dispersive properties for both types of structures are studied in detail, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that the photonic band gaps (PBGs) for both types of MPPCs can be manipulated by plasma frequency, filling factor, the external magnetic field, and the relative dielectric constant of dielectric, respectively. Especially, the external magnetic field can enlarge the PBG for type-2 structure (plasma spheres immersed in dielectric background). However, the plasma collision frequency has no effect on the dispersive properties of two types of three-dimensional MPPCs. The locations of flatbands regions for both types of structures cannot be tuned by any parameters except for plasma frequency and the external magnetic field. The analytical results may be informative and of technical use to design the MPPCs devices.

  17. High quality sub-two cycle pulses from compression of supercontinuum generated in all-normal dispersion photonic crystal fiber.

    PubMed

    Heidt, Alexander M; Rothhardt, Jan; Hartung, Alexander; Bartelt, Hartmut; Rohwer, Erich G; Limpert, Jens; Tünnermann, Andreas

    2011-07-18

    We demonstrate nonlinear pulse compression based on recently introduced highly coherent broadband supercontinuum (SC) generation in all-normal dispersion photonic crystal fiber (ANDi PCF). The special temporal properties of the octave-spanning SC spectra generated with 15 fs, 1.7 nJ pulses from a Ti:Sapphire oscillator in a 1.7 mm fiber piece allow the compression to 5.0 fs high quality pulses by linear chirp compensation with a compact chirped mirror compressor. This is the shortest pulse duration achieved to date from the external recompression of SC pulses generated in PCF. Numerical simulations in excellent agreement with the experimental results are used to discuss the scalability of the concept to the single-cycle regime employing active phase shaping. We show that previously reported limits to few-cycle pulse generation from compression of SC spectra generated in conventional PCF possessing one or more zero dispersion wavelengths do not apply for ANDi PCF. PMID:21934748

  18. Highly nonlinear dispersion-flattened photonic crystal fibers for supercontinuum generation in a telecommunication window.

    PubMed

    Saitoh, Kunimasa; Koshiba, Masanori

    2004-05-17

    We propose a new structure of highly nonlinear dispersion-flattened (HNDF) photonic crystal fiber (PCF) with nonlinear coefficient as large as 30 W(-1)km(-1) at 1.55 microm designed by varying the diameters of the air-hole rings along the fiber radius. This innovative HNDF-PCF has a unique effective-index profile that can offer not only a large nonlinear coefficient but also flat dispersion slope and low leakage losses. It is shown through numerical results that the novel microstructured optical fiber with small normal group-velocity dispersion and nearly zero dispersion slope offers the possibility of efficient supercontinuum generation in the telecommunication window using a few ps pulses. PMID:19475038

  19. Highly nonlinear dispersion-flattened photonic crystal fibers for supercontinuum generation in a telecommunication window

    NASA Astrophysics Data System (ADS)

    Saitoh, Kunimasa; Koshiba, Masanori

    2004-05-01

    We propose a new structure of highly nonlinear dispersion-flattened (HNDF) photonic crystal fiber (PCF) with nonlinear coefficient as large as 30 W-1km-1 at 1.55 µm designed by varying the diameters of the air-hole rings along the fiber radius. This innovative HNDF-PCF has a unique effective-index profile that can offer not only a large nonlinear coefficient but also flat dispersion slope and low leakage losses. It is shown through numerical results that the novel microstructured optical fiber with small normal group-velocity dispersion and nearly zero dispersion slope offers the possibility of efficient supercontinuum generation in the telecommunication window using a few ps pulses.

  20. REVIEW ARTICLE: Dispersion engineered slow light in photonic crystals: a comparison

    NASA Astrophysics Data System (ADS)

    Schulz, S. A.; O'Faolain, L.; Beggs, D. M.; White, T. P.; Melloni, A.; Krauss, T. F.

    2010-10-01

    We review the different types of dispersion engineered photonic crystal waveguides that have been developed for slow light applications. We introduce the group index bandwidth product (GBP) and the loss per delay in terms of dB ns - 1 as two key figures of merit to describe such structures and compare the different experimental realizations based on these figures. A key outcome of the comparison is that slow light based on photonic crystals performs as well or better than slow light based on coupled ring resonators.

  1. Prospective effect in dispersion properties of photonic crystal fibers by selective water-filling of holes.

    PubMed

    Ghosh, Prasenjit; Sarkar, Somenath

    2016-01-20

    Based on a simple but accurate semivectorial solution of Helmholtz's equation by the finite difference method devised with a mode-field convergence technique, we have shown an interesting and significant effect showing an almost ultraflat zero group velocity dispersion in photonic crystal fiber when the holes of the first ring of the fiber are filled with water. Crosschecking our results with earlier results involving a deeply involved multipole method for the central core of photonic crystal fiber filled with water and fused silica, our observation in the case of filling the first ring holes with water reveals potential information in studies of supercontinuum generation. PMID:26835922

  2. Dispersion properties of a 2D magnetized plasma metallic photonic crystal

    SciTech Connect

    Fu, T.; Yang, Z.; Shi, Z.; Lan, F.; Li, D.; Gao, X.

    2013-02-15

    This is a study on a 2D magnetized plasma-filled metal photonic crystal (PMPC). We analyze the dispersion relation of the magnetized PMPC by using the finite-difference time-domain method. Results show a cutoff frequency for the PMPC, and two flat bands and new forbidden band gaps appear due to the external magnetic field. Adjusting the external magnetic field can control the positions of the flat bands, cutoff frequency, and location and width of the local gap. These results provide theoretical basis for designing tunable photonic crystal devices.

  3. Design of highly nonlinear photonic crystal fibers with flattened chromatic dispersion.

    PubMed

    Li, Xuyou; Xu, Zhenlong; Ling, Weiwei; Liu, Pan

    2014-10-10

    A novel (to our knowledge) type of photonic crystal fiber (PCF) with high nonlinearity and flattened dispersion is proposed. The propagation characteristics of chromatic dispersion, effective area, and nonlinearity are studied numerically by using the full-vector finite element method. Several PCF designs with high nonlinearity and nearly zero flattened dispersion or broadband flattened, and even ultraflattened, dispersion over different wavelength bands are obtained by optimizing the structural parameters. One optimized PCF has a nearly zero ultraflattened dispersion of 2.3  ps/(nm·km) with a dispersion variation of 0.2  ps/(nm·km) over the C+L+U wavelength bands. In addition, the dispersion slope and nonlinear coefficient at 1.55 μm can be up to 2.2×10(-3)  ps/nm(2)·km and 33.2  W(-1)·km(-1), respectively. The designs proposed in this paper have bright prospects for applications in all-optical format conversion, supercontinuum generation, optical wavelength conversion, and many other fields. PMID:25322369

  4. A new design of photonic crystal fiber with ultra-flattened dispersion to simultaneously minimize the dispersion and confinement loss

    NASA Astrophysics Data System (ADS)

    Olyaee, Saeed; Taghipour, Fahimeh

    2011-02-01

    Photonic crystal fibers (PCFs) are highly suitable transmission media for wavelength-division-multiplexing (WDM) systems, in which low and ultra-flattened dispersion of PCFs is extremely desirable. It is also required to concurrently achieve both a low confinement loss as well as a large effective area in a wide range of wavelengths. Relatively low dispersion with negligible variation has become feasible in the wavelength range of 1.1 to 1.8μm through the proposed design in this paper. According to a new structure of PCF presented in this study, the dispersion slope is 6.8×10-4ps/km.nm2 and the confinement loss reaches below 10-6 dB/km in this range, while at the same time an effective area of more than 50μm2 has been attained. For the analysis of this PCF, finite-difference time-domain (FDTD) method with the perfectly matched layers (PML) boundary conditions has been used.

  5. Photonic instantaneous frequency measurement with digital output based on dispersion induced power fading functions

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Yang, Bo; Chi, Hao; Jin, Xiaofeng; Zheng, Shilie; Zhang, Xianmin

    2013-04-01

    A novel photonic approach to realize the instantaneous microwave frequency measurement with digital output is proposed and demonstrated experimentally. Based on the power fading function of a double-sideband modulated microwave signal transmitting in a dispersive fiber channel, the microwave frequency to digital code mapping can be realized in a multi-channel system where each channel is configured with a predetermined amount of dispersion. The coding process involved here is similar to that of the photonic analog-to-digital conversion. The principle of the system is discussed in detail. An experiment is carried out, in which the frequency identification with 4-bit quantization levels in 17.5 GHz measurement range is demonstrated. The measurement range and the resolution are discussed theoretically and numerically.

  6. Dispersion engineering in nonlinear soft glass photonic crystal fibers infiltrated with liquids.

    PubMed

    Pniewski, Jacek; Stefaniuk, Tomasz; Van, Hieu Le; Long, Van Cao; Van, Lanh Chu; Kasztelanic, Rafał; Stępniewski, Grzegorz; Ramaniuk, Aleksandr; Trippenbach, Marek; Buczyński, Ryszard

    2016-07-01

    We present a numerical study of the dispersion characteristic modification of nonlinear photonic crystal fibers infiltrated with liquids. A photonic crystal fiber based on the soft glass PBG-08, infiltrated with 17 different organic solvents, is proposed. The glass has a light transmission window in the visible-mid-IR range of 0.4-5 μm and has a higher refractive index than fused silica, which provides high contrast between the fiber structure and the liquids. A fiber with air holes is designed and then developed in the stack-and-draw process. Analyzing SEM images of the real fiber, we calculate numerically the refractive index, effective mode area, and dispersion of the fundamental mode for the case when the air holes are filled with liquids. The influence of the liquids on the fiber properties is discussed. Numerical simulations of supercontinuum generation for the fiber with air holes only and infiltrated with toluene are presented. PMID:27409187

  7. Dispersion and Mirage of Surface Plasmon Waves in Metallic Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Chau, Cheung Wai; Chan, Yun San; Zheng, Ming Jie; Yu, Kin Wah

    2011-03-01

    We have studied the dispersion and propagation of surface plasmon (SP) waves in a one-dimensional metallic photonic crystal composed of metal-dielectric multilayered films by a transfer matrix method. By virtue of Bloch theorem, we are able to obtain the dispersion (frequency-wavevector) relation for arbitrary oblique propagation of SP waves for various non-zero transverse wavevectors. Model calculations are performed for alternative gold and Mg F2 films to obtain the photonic band-gap structure. For a progressively decreasing gold film thickness, the band (gap) width increases (decreases), rendering a precise and feasible tunability of photonic band gaps. Moreover, by imposing a gradual variation in the thickness of dielectric along the multilayers, it is possible to alter the dispersion relation locally, allowing us to study the bending of SP wave at various incident angles. We use Hamiltonian optics approach to obtain the trajectories of propagation. As the transverse wavevector is a constant of motion for a certain incident angle, we obtain different mirage at various oblique incidence. The results are useful for achieving superbending of SP waves. Supported by the General Research Fund of the HKSAR Government.

  8. Supercontinuum generation at 1.55 m in a dispersion-flattened polarization-maintaining photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Kubota, H.; Kawanishi, S.; Tanaka, M.; Yamaguchi, S.

    2003-06-01

    We demonstrate the generation of symmetrical supercontinuum of over 40 nm in the 1.55 m region (1540 - 1580 nm) by injecting 1562 nm, 2.2 ps, 40 GHz optical pulses into a 200 m-long, dispersion-flattened polarization-maintaining photonic crystal fiber. The chromatic dispersion and dispersion slope of the fiber at 1.55 m are -0.23 ps/km/nm and 0.01 ps/km/nm2, respectively. This is the first report of 1.55 m band supercontinuum generation in a dispersion-flattened and polarization-maintaining photonic crystal fiber.

  9. Supercontinuum generation at 1.55 m in a dispersion-flattened polarization-maintaining photonic crystal fiber.

    PubMed

    Yamamoto, T; Kubota, H; Kawanishi, S; Tanaka, M; Yamaguchi, S

    2003-06-30

    We demonstrate the generation of symmetrical supercontinuum of over 40 nm in the 1.55 m region (1540 - 1580 nm) by injecting 1562 nm, 2.2 ps, 40 GHz optical pulses into a 200 m-long, dispersion-flattened polarization-maintaining photonic crystal fiber. The chromatic dispersion and dispersion slope of the fiber at 1.55 m are -0.23 ps/km/nm and 0.01 ps/km/nm2, respectively. This is the first report of 1.55 m band supercontinuum generation in a dispersion-flattened and polarization-maintaining photonic crystal fiber. PMID:19466027

  10. Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

    SciTech Connect

    Hermannsson, Pétur G.; Vannahme, Christoph; Smith, Cameron L. C.; Sørensen, Kristian T.; Kristensen, Anders

    2015-08-10

    Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only a minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.

  11. Buffering capability and limitations in low dispersion photonic crystal waveguides with elliptical airholes.

    PubMed

    Long, Fang; Tian, Huiping; Ji, Yuefeng

    2010-09-01

    A low dispersion photonic crystal waveguide with triangular lattice elliptical airholes is proposed for compact, high-performance optical buffering applications. In the proposed structure, we obtain a negligible-dispersion bandwidth with constant group velocity ranging from c/41 to c/256, by optimizing the major and minor axes of bulk elliptical holes and adjusting the position and the hole size of the first row adjacent to the defect. In addition, the limitations of buffer performance in a dispersion engineering waveguide are well studied. The maximum buffer capacity and the maximum data rate can reach as high as 262bits and 515 Gbits/s, respectively. The corresponding delay time is about 255.4ps. PMID:20820224

  12. Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

    NASA Astrophysics Data System (ADS)

    Hermannsson, Pétur G.; Vannahme, Christoph; Smith, Cameron L. C.; Sørensen, Kristian T.; Kristensen, Anders

    2015-08-01

    Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only a minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.

  13. Three octave spanning supercontinuum by red-shifted dispersive wave in photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Sharma, Mohit; Konar, S.

    2016-03-01

    This article presents a three-layer index guided lead silicate (SF57) photonic crystal fiber which simultaneously promises to yield large effective optical nonlinear coefficient and low anomalous dispersion that makes it suitable for supercontinuum (SC) generation. At an operating wavelength 1550 nm, the typical optimized value of anomalous dispersion and effective nonlinear coefficient turns out to be ~4 ps/km/nm and ~1078 W-1km-1, respectively. Through numerical simulation, it is realized that the designed fiber promises to exhibit three octave spanning SC from 900 to 7200 nm using 50 fs 'sech' optical pulses of 5 kW peak power. Due to the cross-phase modulation and four-wave mixing processes, a long range of red-shifted dispersive wave generated, which assists to achieve such large broadening. In addition, we have investigated the compatibility of SC generation with input pulse peak power increment and briefly discussed the impact of nonlinear processes on SC generation.

  14. 10.8 kW spectral beam combination of eight all-fiber superfluorescent sources and their dispersion compensation.

    PubMed

    Zheng, Ye; Yang, Yifeng; Wang, Jianhua; Hu, Man; Liu, Guangbo; Zhao, Xiang; Chen, Xiaolong; Liu, Kai; Zhao, Chun; He, Bing; Zhou, Jun

    2016-05-30

    We report an 8-element spectral beam combination of Yb-doped all fiber superfluorescent sources around 1070 nm wavelength. Each source consists of a 60 mW front-end and a 1.5 kW three-stage fiber amplifier chain. The eight output beamlets are spectrally combined using a home-made polarization-independent multilayer dielectric reflective diffraction grating. 10.8 kW output power is achieved with an efficiency of 94%. Besides, both theoretical and experimental studies of dual grating dispersion compensation scheme have been performed, which is proved to be a prospective way for high brightness spectral beam combination. PMID:27410127

  15. Dynamics of dispersive photon-number QND measurements in a micromaser

    SciTech Connect

    Kozlovskii, A. V.

    2007-04-15

    A numerical analysis of dispersive quantum nondemolition measurement of the photon number of a microwave cavity field is presented. Simulations show that a key property of the dispersive atom-field interaction used in Ramsey interferometry is the extremely high sensitivity of the dynamics of atomic and field states to basic parameters of the system. When a monokinetic atomic beam is sent through a microwave cavity, a qualitative change in the field state can be caused by an uncontrollably small deviation of parameters (such as atom path length through the cavity, atom velocity, cavity mode frequency detuning, or atom-field coupling constants). The resulting cavity field can be either in a Fock state or in a super-Poissonian state (characterized by a large photon-number variance). When the atoms have a random velocity spread, the field is squeezed to a Fock state for arbitrary values of the system's parameters. However, this makes detection of Ramsey fringes impossible, because the probability of detecting an atom in the upper or lower electronic state becomes a random quantity almost uniformly distributed over the interval between zero and unity, irrespective of the cavity photon number.

  16. Integrated and dispersed photon echo studies of nitrile stretching vibration of 4-cyanophenol in methanol.

    PubMed

    Ha, Jeong-Hyon; Lee, Kyung-Koo; Park, Kwang-Hee; Choi, Jun-Ho; Jeon, Seung-Joon; Cho, Minhaeng

    2009-05-28

    By means of integrated and dispersed IR photon echo measurement methods, the vibrational dynamics of C-N stretch modes in 4-cyanophenol and 4-cyanophenoxide in methanol is investigated. The vibrational frequency-frequency correlation function (FFCF) is retrieved from the integrated photon echo signals by assuming that the FFCF is described by two exponential functions with about 400 fs and a few picosecond components. The excited state lifetimes of the C-N stretch modes of neutral and anionic 4-cyanophenols are 1.45 and 0.91 ps, respectively, and the overtone anharmonic frequency shifts are 25 and 28 cm(-1). At short waiting times, a notable underdamped oscillation, which is attributed to a low-frequency intramolecular vibration coupled to the CN stretch, in the integrated and dispersed vibrational echo as well as transient grating signals was observed. The spectral bandwidths of IR absorption and dispersed vibrational echo spectra of the 4-cyanophenoxide are significantly larger than those of its neutral form, indicating that the strong interaction between phenoxide and methanol causes large frequency fluctuation and rapid population relaxation. The resonance effects in a paradisubstituted aromatic compound would be of interest in understanding the conjugation effects and their influences on chemical reactivity of various aromatic compounds in organic solvents. PMID:19485459

  17. Alignment of a petawatt-class pulse compressor with the third-order dispersion completely compensated

    NASA Astrophysics Data System (ADS)

    Zuo, Yanlei; Zhou, Kainan; Wu, Zhaohui; Wang, Xiao; Xie, Na; Su, Jingqin; Zeng, Xiaoming

    2016-05-01

    It is necessary to eliminate third-order dispersion to acquire an ultrashort pulse of less than 30 fs. We demonstrate for the first time, to the best of our knowledge, the alignment of a petawatt-class laser compressor using the equiphase lines in the spatial and spectral interference patterns. Third-order dispersion has been completely eliminated and a Fourier-transform-limited pulsewidth of 19.6 fs has been approached.

  18. Numerical calculation of phase-matching properties in photonic crystal fibers with three and four zero-dispersion wavelengths.

    PubMed

    Zhao, Xingtao; Liu, Xiaoxu; Wang, Shutao; Wang, Wei; Han, Ying; Liu, Zhaolun; Li, Shuguang; Hou, Lantian

    2015-10-19

    Photonic crystal fibers with three and four zero-dispersion wavelengths are presented through special design of the structural parameters, in which the closing to zero and ultra-flattened dispersion can be obtained. The unique phase-matching properties of the fibers with three and four zero-dispersion wavelengths are analyzed. Variation of the phase-matching wavelengths with the pump wavelengths, pump powers, dispersion properties, and fiber structural parameters is analyzed. The presence of three and four zero-dispersion wavelengths can realize wavelength conversion of optical soliton between two anomalous dispersion regions, generate six phase-matching sidebands through four-wave mixing and create more new photon pairs, which can be used for the study of supercontinuum generation, optical switches and quantum optics. PMID:26480448

  19. Tests of a Two-Photon Technique for Measuring Polarization Mode Dispersion With Subfemtosecond Precision

    PubMed Central

    Dauler, Eric; Jaeger, Gregg; Muller, Antoine; Migdall, A.; Sergienko, A.

    1999-01-01

    An investigation is made of a recently introduced quantum interferometric method capable of measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual interferometric stability problems associated with such small time scales. The technique makes use of the extreme temporal correlation of orthogonally polarized pairs of photons produced via type-II phase-matched spontaneous parametric down-conversion. When sent into a simple polarization interferometer these photon pairs produce a sharp interference feature seen in the coincidence rate. The PMD of a given sample is determined from the shift of that interference feature as the sample is inserted into the system. The stability and resolution of this technique is shown to be below 0.2 fs. We explore how this precision is improved by reducing the length of the down-conversion crystal and increasing the spectral band pass of the system.

  20. Extremely low-loss, dispersion flattened porous-core photonic crystal fiber for terahertz regime

    NASA Astrophysics Data System (ADS)

    Islam, Saiful; Islam, Mohammad Rakibul; Faisal, Mohammad; Arefin, Abu Sayeed Muhammad Shamsul; Rahman, Hasan; Sultana, Jakeya; Rana, Sohel

    2016-07-01

    A porous-core octagonal photonic crystal fiber (PC-OPCF) with ultralow effective material loss (EML), high core power fraction, and ultra flattened dispersion is proposed for terahertz (THz) wave propagation. At an operating frequency of 1 THz and core diameter of 345 μm, simulation results display an extremely low EML of 0.047 cm-1, 49.1% power transmission through core air holes, decreased confinement loss with the increase of frequency, and dispersion variation of 0.15 ps/THz/cm. In addition, the proposed PCF can successfully operate in single-mode condition. All the simulations are performed with finite-element modeling package, COMSOL v4.2. The design can be fabricated using a stacking and drilling method. Thus, the proposed fiber has the potential of being an effective transmission medium of broadband THz waves.

  1. Dispersion properties of transverse anisotropic liquid crystal core photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Karasawa, Naoki

    2016-04-01

    The dispersion properties of liquid crystal core photonic crystal fibers for different core diameters have been calculated by a full vectorial finite difference method. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica and a central hole is filled with liquid crystal to create a core. In this study, three types of transverse anisotropic configurations, where liquid crystal molecules are oriented in a transverse plane, and a planar configuration, where liquid crystal molecules are oriented in a propagation direction, are considered. The large changes of the dispersion properties are found when the orientation of the liquid crystal molecules is changed from a planar configuration to a uniform configuration, where all molecules are oriented in the same direction in a transverse plane. Since the orientation of liquid crystal molecules may be controlled by applying an electric field, it could be utilized for various applications including the spectral control of supercontinuum generation.

  2. Dispersion engineering in soft glass photonic crystal fibers infiltrated with liquids

    NASA Astrophysics Data System (ADS)

    Stefaniuk, Tomasz; Le Van, Hieu; Pniewski, Jacek; Cao Long, Van; Ramaniuk, Aleksandr; Grajewski, Karol; Chu Van, Lanh; Karpierz, Mirosław; Trippenbach, Marek; Buczynski, Ryszard

    2015-12-01

    We present a numerical study of the dispersion characteristic modification in a nonlinear photonic crystal fibre (PCF) infiltrated with organic solvents. The PCF is made of PBG08 glass and was developed in the stack-and-draw process. The PBG08 glass has a high refractive index (n < 2.0), high nonlinear refractive index (n2 = 4.3×10-19 m2/W) and good rheological properties that allow for thermal processing of the glass without crystallization. In the numerical study 18 different solvents were used. The dispersion, mode area, and losses characteristics were calculated. The zero dispersion wavelength (ZDW) of the fibre can be shifted towards longer wavelengths by approx. 150 nm by using Nitrobenzene as infiltrating liquid and by a smaller value using other liquids. At the same time the mode area of the fundamental mode increases by approx. 5 to 15% depending on the wavelength considered. The confinement losses increase significantly for six analysed liquids by a few orders of magnitude up to 102 dB/m. Our approach allows to combine high nonlinearities of the soft glass with the possibility to tune zero dispersion wavelength to the desired value.

  3. Optical-pulse generation and compression using a comb-driven gain-switched laser diode and chromatic-dispersion compensator

    NASA Astrophysics Data System (ADS)

    Arora, Sumeeta

    both the comb-generator pulses and the non-regular, data-like "1011" pulse pattern, we study the impact of chromatic dispersion on the optical pulse width and pulse performance. Chromatic dispersion has been used in previous studies as a means of compressing the gain-switched pulses. For comb-generated pulses, we find that an increase in the bias current applied to the laser diode results in a decrease in the magnitude of chromatic dispersion required to compress the gain-switched optical pulse. Also the percentage change in the width of the gain-switched pulse on passing through a dispersion source increases with the increase in bias current even though the applied chromatic dispersion is decreased. The optical pulses generated using data pattern are more uniform in terms of peak power of the optical pulses when chromatic dispersion in a particular range is applied. A reduction in jitter is also seen for that range of dispersion while it increases for higher and lower values of dispersion. During the course of my thesis work, I activated a gain-switched optical pulse source in the Photonic Systems Laboratory at RIT for the first time. This source will be used to support future research projects. I also developed a suite of MATLAB code for study of gain-switching and dispersion compensation.

  4. Multiple Bragg diffraction in opal-based photonic crystals: Spectral and spatial dispersion

    NASA Astrophysics Data System (ADS)

    Shishkin, I. I.; Rybin, M. V.; Samusev, K. B.; Golubev, V. G.; Limonov, M. F.

    2014-01-01

    We present an experimental and theoretical study of multiple Bragg diffraction from synthetic opals. An original setup permits us to overcome the problem of the total internal light reflection in an opal film and to investigate the diffraction from both the (111) and (1¯11) systems of planes responsible for the effect. As a result, angle- and frequency-resolved diffraction and transmission measurements create a picture of multiple Bragg diffraction that includes general agreement between dips in the transmission spectra and diffraction peaks for each incident white light angle and a twin-peak structure at frequencies of the photonic stop band edges. Two opposite cases of the interference are discussed: an interference of two narrow Bragg bands that leads to multiple Bragg diffraction with anticrossing regime for dispersion photonic branches and an interference of a narrow Bragg band and broad disorder-induced Mie background that results in a Fano resonance. A good quantitative agreement between the experimental data and calculated photonic band structure has been obtained.

  5. Quantum-rod dispersed photopolymers for multi-dimensional photonic applications.

    PubMed

    Li, Xiangping; Chon, James W M; Evans, Richard A; Gu, Min

    2009-02-16

    Nanocrystal quantum rods (QRs) have been identified as an important potential key to future photonic devices because of their unique two-photon (2P) excitation, large 2P absorption cross section and polarization sensitivity. 2P excitation in a conventional solid photosensitive medium has driven all-optical devices towards three-dimensional (3D) platform architectures such as 3D photonic crystals, optical circuits and optical memory. The development of a QR-sensitized medium should allow for a polarization-dependent change in refractive index. Such a localized polarization control inside the focus can confine the light not only in 3D but also in additional polarization domain. Here we report on the first 2P absorption excitation of QR-dispersed photopolymers and its application to the fabrication of polarization switched waveguides, multi-dimensional optical patterning and optical memory. This fabrication was achieved by a 2P excited energy transfer process between QRs and azo dyes which facilitated 3D localized polarization sensitivity resulting in the control of light in four dimensions. PMID:19219199

  6. Studying the VCSEL to VCSEL injection locking for enhanced chromatic dispersion compensation

    NASA Astrophysics Data System (ADS)

    Li, Linfu

    2010-11-01

    In order to supply a theoretical guide for digital chaotic telecommunication, the technique of Optical injection locking (OIL) of semiconductor lasers on the chaotic communication have been investigated based on the theoretical models used to describe the dynamics of solitary VCSEL subjected to the external optical injection and signal transmission in fiber. The numerical simulation results show that, the frequency chirp and time-resolved chirp are reduced in magnitude, using a VCSEL laser as master and another VCSEL as slave, it leads to a no-penalty transmission over 50 km of uncompensated in SSMF at 10Gb/s, and it could be higher rate and more remote if there were appropriate compensation.

  7. Optimization of highly nonlinear dispersion-flattened photonic crystal fiber for supercontinuum generation

    NASA Astrophysics Data System (ADS)

    Zhang, Ya-Ni

    2013-01-01

    A simple type of photonic crystal fiber (PCF) for supercontinuum generation is proposed for the first time. The proposed PCF is composed of a solid silica core and a cladding with square lattice uniform elliptical air holes, which offers not only a large nonlinear coefficient but also a high birefringence and low leakage losses. The PCF with nonlinear coefficient as large as 46 W-1 · km-1 at the wavelength of 1.55 μm and a total dispersion as low as ±2.5 ps · nm-1 · km-1 over an ultra-broad waveband range of the S—C—L band (wavelength from 1.46 μm to 1.625 μm) is optimized by adjusting its structure parameter, such as the lattice constant Λ, the air-filling fraction f, and the air-hole ellipticity η. The novel PCF with ultra-flattened dispersion, highly nonlinear coefficient, and nearly zero negative dispersion slope will offer a possibility of efficient super-continuum generation in telecommunication windows using a few ps pulses.

  8. Group-velocity dispersion in multimode photonic crystal fibers measured using time-domain white-light interferometry

    NASA Astrophysics Data System (ADS)

    Böswetter, Pascal; Baselt, Tobias; Ebert, Frank; Basan, Fabiola; Hartmann, Peter

    2011-02-01

    Optical fibers are used in various applications, e. g. optical communication, material processing, as a laser medium or to generate efficient supercontinua. For most of these applications the knowledge of the dispersion is an essential prerequisite. The dispersion and modal properties of photonic crystal fibers (PCF) strongly depend on the hole diameter and pitch. Since fabrication tolerances affect the structure of the photonic lattice, the dispersion behavior as well as the number of guided transverse modes can differ from numerical calculations. Dispersion measurement of singlemode photonic crystal fibers has been well described in recent papers. However, the determination of dispersion in the presence of higher-order modes is much more difficult. To measure the dispersion of optical fibers with high accuracy, a time-domain white-light interferometer based on a Mach-Zehnder interferometer is presented. The experimental setup allows to determine the wavelength-dependent differential group delay of light travelling through conventional fibers and PCFs within the wavelength range from VIS to NIR. Interferences appear due to superposition of two laser beams, one propagating through the tested fiber and the other travelling through air. Measuring the different group delays of a step-index fiber shows the sufficient accuracy of the interferometer. This paper demonstrates a simple yet effective way to suppress higher-order modes, making it possible to measure the chromatic dispersion of singlemode as well as multimode fibers.

  9. Dispersion optimization of nonlinear glass photonic crystal fibers and impact of fabrication tolerances on their telecom nonlinear applications performance

    NASA Astrophysics Data System (ADS)

    Kanka, Jiri

    2009-05-01

    For most telecom nonlinear applications a high effective nonlinearity, low group velocity dispersion with a low dispersion slope and a short fibre length are the key parameters. Combining photonic crystal fibre (PCF) technology with highly nonlinear glasses could meet these requirements very well. We have performed dispersion optimization of PCFs made from selected nonlinear glasses with a solid core and small number of hexagonally arrayed air holes. The optimization procedure employs the Nelder-Mead downhill simplex algorithm. For the modal analysis of the photonic crystal fibre structure a fully-vectorial mode solver based on the finite element method is used. We have obtained two types of dispersion optimized nonlinear PCF designs: PCFs of the first type are single-mode and highly nonlinear with a small and flattened dispersion in the 1500-1600 nm range. These PCF structures have air holes hexagonally arrayed in from 3 to 5 rings, however, their dispersion characteristics are very sensitive to variations in structural parameters. PCFs of the second type are two-ring PCFs with larger multi-mode cores. They have fundamental mode's zero dispersion wavelength around 1550 nm with non-zero moderate dispersion slopes which are less sensitive to structural variation. It is supposed that this alternative PCF design will be easier to fabricate. The effects of fabrication imprecision on the dispersion characteristics for both PCF designs are demonstrated numerically and discussed in the context of nonlinear telecom applications.

  10. Towards hybrid pixel detectors for energy-dispersive or soft X-ray photon science.

    PubMed

    Jungmann-Smith, J H; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Greiffenberg, D; Huthwelker, T; Maliakal, D; Mayilyan, D; Medjoubi, K; Mezza, D; Mozzanica, A; Ramilli, M; Ruder, Ch; Schädler, L; Schmitt, B; Shi, X; Tinti, G

    2016-03-01

    JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a two-dimensional hybrid pixel detector for photon science applications at free-electron lasers and synchrotron light sources. The JUNGFRAU 0.4 prototype presented here is specifically geared towards low-noise performance and hence soft X-ray detection. The design, geometry and readout architecture of JUNGFRAU 0.4 correspond to those of other JUNGFRAU pixel detectors, which are charge-integrating detectors with 75 µm × 75 µm pixels. Main characteristics of JUNGFRAU 0.4 are its fixed gain and r.m.s. noise of as low as 27 e(-) electronic noise charge (<100 eV) with no active cooling. The 48 × 48 pixels JUNGFRAU 0.4 prototype can be combined with a charge-sharing suppression mask directly placed on the sensor, which keeps photons from hitting the charge-sharing regions of the pixels. The mask consists of a 150 µm tungsten sheet, in which 28 µm-diameter holes are laser-drilled. The mask is aligned with the pixels. The noise and gain characterization, and single-photon detection as low as 1.2 keV are shown. The performance of JUNGFRAU 0.4 without the mask and also in the charge-sharing suppression configuration (with the mask, with a `software mask' or a `cluster finding' algorithm) is tested, compared and evaluated, in particular with respect to the removal of the charge-sharing contribution in the spectra, the detection efficiency and the photon rate capability. Energy-dispersive and imaging experiments with fluorescence X-ray irradiation from an X-ray tube and a synchrotron light source are successfully demonstrated with an r.m.s. energy resolution of 20% (no mask) and 14% (with the mask) at 1.2 keV and of 5% at 13.3 keV. The performance evaluation of the JUNGFRAU 0.4 prototype suggests that this detection system could be the starting point for a future detector development effort for either applications in the soft X-ray energy regime or for an energy-dispersive

  11. High-speed all-optical pattern recognition of dispersive Fourier images through a photonic reservoir computing subsystem.

    PubMed

    Mesaritakis, Charis; Bogris, Adonis; Kapsalis, Alexandros; Syvridis, Dimitris

    2015-07-15

    In this Letter, we present and fully model a photonic scheme that allows the high-speed identification of images acquired through the dispersive Fourier technique. The proposed setup consists of a photonic reservoir-computing scheme that is based on the nonlinear response of randomly interconnected InGaAsP microring resonators. This approach allowed classification errors of 0.6%, whereas it alleviates the need for complex high-cost optoelectronic sampling and digital processing. PMID:26176483

  12. Polarization maintaining highly nonlinear photonic crystal fiber with closely lying two zero dispersion wavelengths

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Rabiul; Anower, Md. Shamim; Hasan, Md. Imran

    2016-05-01

    A simple hexagonal photonic crystal fiber is proposed to simultaneously achieve ultrahigh birefringence, large nonlinear coefficient, and two zero dispersion wavelengths (ZDWs). The finite element method with circular perfectly matched layer boundary condition is used to simulate the designed structure. Simulation results show that it is possible to achieve two closely lying ZDWs of 1.08 and 1.29 μm for x-polarization with 0.88 and 1.20 μm for y-polarization modes, respectively. In addition, an ultrahigh birefringence of 3.15×10-2 and a high nonlinear coefficient of 58 W-1 km-1 are also obtained at the excitation wavelength of 1.55 μm. The proposed fiber can have important applications in supercontinuum generation, parametric amplification, four-wave mixing, and optical sensors design.

  13. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    SciTech Connect

    Wahle, Markus Kitzerow, Heinz-Siegfried

    2015-11-16

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  14. Analysis of band structure, transmission properties, and dispersion behavior of THz wave in one-dimensional parabolic plasma photonic crystal

    SciTech Connect

    Askari, Nasim; Eslami, Esmaeil; Mirzaie, Reza

    2015-11-15

    The photonic band gap of obliquely incident terahertz electromagnetic waves in a one-dimensional plasma photonic crystal is studied. The periodic structure consists of lossless dielectric and inhomogeneous plasma with a parabolic density profile. The dispersion relation and the THz wave transmittance are analyzed based on the electromagnetic equations and transfer matrix method. The dependence of effective plasma frequency and photonic band gap characteristics on dielectric and plasma thickness, plasma density, and incident angle are discussed in detail. A theoretical calculation for effective plasma frequency is presented and compared with numerical results. Results of these two methods are in good agreement.

  15. Electrically tunable zero dispersion wavelengths in photonic crystal fibers filled with a dual frequency addressable liquid crystal

    NASA Astrophysics Data System (ADS)

    Wahle, Markus; Kitzerow, Heinz-Siegfried

    2015-11-01

    We present a liquid crystal (LC) infiltrated photonic crystal fiber, which enables the electrical tuning of the position of zero dispersion wavelengths (ZDWs). A dual frequency addressable liquid crystal is aligned perpendicular on the inclusion walls of a photonic crystal fiber, which results in an escaped radial director field. The orientation of the LC is controlled by applying an external electric field. Due to the high index of the liquid crystal the fiber guides light by the photonic band gap effect. Multiple ZDWs exist in the visible and near infrared. The positions of the ZDWs can be either blue or red shifted depending on the frequency of the applied voltage.

  16. Nonequilibrium quantum fluctuations of a dispersive medium: Spontaneous emission, photon statistics, entropy generation, and stochastic motion

    NASA Astrophysics Data System (ADS)

    Maghrebi, Mohammad F.; Jaffe, Robert L.; Kardar, Mehran

    2014-07-01

    We study the implications of quantum fluctuations of a dispersive medium, under steady rotation, either in or out of thermal equilibrium with its environment. A rotating object exhibits a quantum instability by dissipating its mechanical motion via spontaneous emission of photons, as well as internal heat generation. Universal relations are derived for the radiated energy and angular momentum as trace formulas involving the object's scattering matrix. We also compute the quantum noise by deriving the full statistics of the radiated photons out of thermal and/or dynamic equilibrium. The (entanglement) entropy generation is quantified and the total entropy is shown to be always increasing. Furthermore, we derive a Fokker-Planck equation governing the stochastic angular motion resulting from the fluctuating backreaction frictional torque. As a result, we find a quantum limit on the uncertainty of the object's angular velocity in steady rotation. Finally, we show in some detail that a rotating object drags nearby objects, making them spin parallel to its axis of rotation. A scalar toy model is introduced to simplify the technicalities and ease the conceptual complexities and then a detailed discussion of quantum electrodynamics is presented.

  17. Inverse dispersion method for calculation of complex photonic band diagram and PT symmetry

    NASA Astrophysics Data System (ADS)

    Rybin, Mikhail V.; Limonov, Mikhail F.

    2016-04-01

    We suggest an inverse dispersion method for calculating a photonic band diagram for materials with arbitrary frequency-dependent dielectric functions. The method is able to calculate the complex wave vector for a given frequency by solving the eigenvalue problem with a non-Hermitian operator. The analogy with PT -symmetric Hamiltonians reveals that the operator corresponds to the momentum as a physical quantity, and the singularities at the band edges are related to the branch points and responses for the features on the band edges. The method is realized using a plane wave expansion technique for a two-dimensional periodic structure in the case of TE and TM polarizations. We illustrate the applicability of the method by the calculation of the photonic band diagrams of an infinite two-dimensional square lattice composed of dielectric cylinders using the measured frequency-dependent dielectric functions of different materials (amorphous hydrogenated carbon, silicon, and chalcogenide glass). We show that the method allows one to distinguish unambiguously between Bragg and Mie gaps in the spectra.

  18. Numerical analysis for a solid-core photonic crystal fiber with tunable zero dispersion wavelengths

    NASA Astrophysics Data System (ADS)

    Barrientos-García, A.; Sukoivanov, Igor A.; Andrade-Lucio, J. A.; Guryev, Igor; Shulika, Oleksiy V.; Hernandez-García, J. C.; Ramos-Ortiz, G.

    2014-09-01

    Here we propose a simple design for a solid-core photonic crystal fiber made of silica by keeping the golden ratio (1.618) between pitch and air hole diameter Λ /d in a subset of six rings of air-holes with hexagonal arrangement. In the case when we have a pitch equal to one micron (Λ =1 μm), we need air-holes diameters d=0.618 μm in order to obtain the golden ratio parameter (Λ/d=1.618), and achieve two zero dispersion wavelength (ZDW) points at 725 nm and 1055 nm; this gives us the possibility to use this fiber in supercontinuum generation using a laser emission close to that points. We analyzed a series of fibers using this relation and show the possibilities of tunable ZDW in a wide range of wavelengths from 725 nm to 2000 nm with low losses and small effective area. In agreement with the ZDW point needed, the geometry of the structure can be modified to the point of having only three rings of air holes that surround the solid core with low losses and good confinement mode. The design proposed here is analyzed using the finite element method (FEM) with perfectly matched layers (PML), including the material dispersion directly into the model applying the Sellmeier's equation.

  19. Linearization of an intensity-modulated analog photonic link using an FBG and a dispersive fiber

    NASA Astrophysics Data System (ADS)

    Gao, Yongsheng; Wen, Aijun; Chen, Yan; Zhang, Huixing; Xiang, Shuiying

    2015-03-01

    An optical linearization technique for an intensity-modulated analog photonic link is proposed and demonstrated. Conventional double-sideband intensity modulation is applied to modulate the radio frequency (RF) signal onto the optical carrier; then a fiber Bragg grating (FBG) is used to suppress part of the optical carrier and a single mode fiber (SMF) is followed to introduce some dispersion. By properly adjusting the dispersion-induced phase shift, the third-order intermodulation distortion can be suppressed. The proposed scheme is simple and low cost. The FBG can be also used to optimize the power ratio of the optical carrier and sidebands, thus improving the link gain, while the SMF can act as a transmission medium to deliver the RF signal. Experimental results show that an improvement of 12.6 dB in the spurious-free dynamic range and 3.8 dB in the link gain is achieved after linearization. The frequency tunability of the linearization technique is also evaluated by the transmission of RF signals with different center frequencies and bandwidths.

  20. Design of highly nonlinear dispersion flattened hexagonal photonic crystal fibers for dental optical coherence tomography applications

    NASA Astrophysics Data System (ADS)

    Namihira, Yoshinori; Hossain, Md. Anwar; Koga, Taito; Islam, Md. Ashraful; Razzak, S. M. Abdur; Kaijage, Shubi F.; Hirako, Yuki; Higa, Hiroki

    2012-03-01

    In this paper, we propose a highly nonlinear dispersion flattened hexagonal photonic crystal fiber (HNDF-HPCF) with nonlinear coefficients as large as 57.5W-1 km-1 at 1.31 μm wavelength for dental optical coherence tomography (OCT) applications. This HNDF-HPCF offers not only large nonlinear coefficient but also very flat dispersion slope and very low confinement losses. Using these characteristics of our proposed PCF, it is shown through simulations by using finite difference method with an anisotropic perfectly matched boundary layer that this PCF offers the efficient supercontinuum (SC) generation for dental OCT applications at 1.31 μm wavelength using a picosecond pulse easily produced by commercially available less expensive laser sources. Coherent length of light source using SC is found 10 μm and the spatial resolutions in the depth direction for dental applications of OCT are found about 6.1 μm for enamel and 6.5 μm for dentin.

  1. Photonic Integrated Circuits Based on Plasmonics and Quantum Dot Materials: Properties, Compensation of Optical Losses and Applications

    NASA Astrophysics Data System (ADS)

    Thylen, Lars

    2010-03-01

    Nanophotonics and plasmonics have received much attention recently, fuelled by a general interest in nanotechnology but also by rapid advances in integrated photonics, mainly brought about by using silicon, with larger refractive index difference than previously employed [L. Thylen et al, J. Zhejiang Univ. SCIENCE 2006 7(12)]. Plasmonics offers a possibility for devices with field sizes much smaller than the wavelength of light in aa host medium. But the tighter the field confinement, the greater are generally the optical losses, determined by the imaginary part of epsilon. This remains a critical issue. Dissipative losses impede the ubiquitous usefulness of nanophotonics light wave circuits. Recently, optical gain in quantum dots for reducing or compensate losses was analyzed [A Bratkovsky et al, Applied Physics Letters 93, 193106 (2008)]. However, the concomitant effects of the high (but not unreachable) gain required for this are high power dissipation and signal to noise ratio degradation. Power dissipation is primarily due to the losses of the metal structures and Auger recombination in the quantum dots. A general and square chip size independent expression for the information capacity of a lossless (by amplification) plasmonic chip is given, using the allowed values for integrated electronics power dissipation. In conclusion, with amplification and with current understanding, it appears possible to sizewise come close to CMOS dimensions for isolated integrated photonic devices, but not in integration density. This is due to power dissipation in currently employed negative epsilon materials.

  2. A Kind of Double-Cladding Photonic Crystal Fiber with High Birefringence and Two Zero-Dispersion Wavelengths

    NASA Astrophysics Data System (ADS)

    Zhou, Hong-Song; Li, Shu-Guang; Fu, Bo; Yao, Yan-Yan; Zhang, Lei

    2010-01-01

    A kind of double-cladding photonic crystal fiber (DC-PCF) with high birefringence and two zero-dispersion wavelengths is proposed. It is found that the birefringence of DC-PCF with inner cladding air holes pitch 1.0 μm and diameter 0.8 μm is 1.001 × 10-2 in the optical communication band at wavelength 1.55 μm by the multipole method. It is demonstrated that two zero dispersion wavelengths can be achieved in the optical communication band between 0.8 μm and 1.7 μm, and the first zero-dispersion wavelength is in the working wave band of the Ti:sapphire oscillator, which contributes to the frequency conversion of the Ti:sapphire femtosecond laser. PCF with two zero-dispersion wavelengths can make strong power supercontinuum spectral in the near infrared band.

  3. Programmable eye-opener lattice filter for multi-channel dispersion compensation using an integrated compact low-loss silicon nitride platform.

    PubMed

    Moreira, Renan; Gundavarapu, Sarat; Blumenthal, Daniel J

    2016-07-25

    A tunable eye-opening lattice filter for dispersion compensation is demonstrated on an ultra low-loss waveguide platform based on a compact high-aspect ratio Si3N4 core. A programmable 10th order lattice filter is demonstrated by cascading a total of 21 Mach-Zehnder interferometers with programmable delay lines of lengths designed at the baseband data rate. The filter has a footprint of 2.23 cm2 with continuously tunable dispersion from -500 ps/nm to 500 ps/nm. The filter shows a periodic transfer function with a measured FSR of 100 GHz capable of compensating multiple WDM channels with a single device. PMID:27464127

  4. Dispersion-compensation-free femtosecond Tm-doped all-fiber laser with a 248  MHz repetition rate.

    PubMed

    Sun, Biao; Luo, Jiaqi; Ng, Boon Ping; Yu, Xia

    2016-09-01

    In this Letter, we report a dispersion-compensation-free ultrafast thulium-doped all-fiber laser based on nonlinear polarization evolution (NPE) mode locking, delivering 330 fs soliton pulses at 1950 nm. A multifunctional hybrid fiberized device was applied in the oscillator to minimize the physical cavity length to ∼80  cm with a total dispersion of -0.045  ps2, enabling a state-of-the-art fundamental mode-locking repetition rate of 248 MHz in an NPE-based oscillator at ∼2  μm. PMID:27607970

  5. Compensation for displacement of the focal point in cone beam single photon emission computed tomography reconstruction.

    PubMed

    Cao, Z; Qian, L

    1997-04-01

    This study examined the effects of focal point displacement on image quality in cone beam single photon emission computed tomography (SPECT). A new image reconstruction algorithm that accounts for the focal point shift was derived and three shift geometries were investigated. The geometries included a lateral shift with a fixed focal length but off-center focusing, a linear axial shift with a variable focal length that depends linearly on the distance between a bin of the detector and the center of the detector, and a random axial shift with a randomly varying focal length. Computer simulation was conducted to evaluate the shift effects with a phantom that was composed of 118 small spherical sources. The results demonstrated that the lateral shift of the focal point was more critical to image quality than was the axial shift. With a 0.64 cm (1 pixel) lateral shift, noticeable artifacts was observed, while an axial shift resulted in minimal changes in image quality until it reached 8 cm (12.5 pixels). The derived reconstruction algorithm eliminated most of the artifacts caused by a fixed lateral shift or a linear axial shift of the focal point, but failed to do so for a random axial shift since the linear distribution assumed in image reconstruction did not match the random shift occurred in acquisition of the data. PMID:9291002

  6. Compensation of spherical aberration influences for two-photon polymerization patterning of large 3D scaffolds

    NASA Astrophysics Data System (ADS)

    Stichel, T.; Hecht, B.; Houbertz, R.; Sextl, G.

    2015-10-01

    Two-photon polymerization using femtosecond laser pulses at a wavelength of 515 nm is used for three-dimensional patterning of photosensitive, biocompatible inorganic-organic hybrid polymers (ORMOCER®s). In order to fabricate millimeter-sized biomedical scaffold structures with interconnected pores, medium numerical aperture air objectives with long working distances are applied which allow voxel lengths of several micrometers and thus the solidification of large scaffolds in an adequate time. It is demonstrated that during processing the refraction of the focused laser beam at the air/material interface leads to strong spherical aberration which decreases the peak intensity of the focal point spread function along with shifting and severely extending the focal region in the direction of the beam propagation. These effects clearly decrease the structure integrity, homogeneity and the structure details and therefore are minimized by applying a positioning and laser power adaptation throughout the fabrication process. The results will be discussed with respect to the resulting structural homogeneity and its application as biomedical scaffold.

  7. Microwave photonic filter with two independently tunable passbands based on paralleled fiber Mach-Zehnder interferometers and dispersive medium

    NASA Astrophysics Data System (ADS)

    Xu, Zuowei; Fu, Hongyan; Chen, Hao; Wu, Congxian; Xu, Huiying; Cai, Zhiping

    2015-09-01

    In this article, we propose and experimentally demonstrate a novel microwave photonics filter (MPF) with two independently tunable passbands. The MPF is based on a sliced broadband optical source and a dispersive medium, and two paralleled fiber Mach-Zehnder interferometers (FMZIs) have been employed as the optical spectrum slicer. A coil of single-mode fiber has been used as a dispersion medium, which introduces time delay for each tap. A stable dual-passband MPF has been obtained, and the experimental results show that each passband of the MPF can be tuned freewill by adjusting the variable optical delay line (VODL) in each of the FMZIs.

  8. Dispersal

    USGS Publications Warehouse

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  9. Measurement of group velocity dispersion in a solid-core photonic crystal fiber filled with a nematic liquid crystal.

    PubMed

    Wahle, Markus; Kitzerow, Heinz

    2014-08-15

    Liquid crystal-filled photonic crystal fibers (PCFs) are promising candidates for electrically tunable integrated photonic devices. In this Letter, we present group velocity measurements on such fibers. A large mode area PCF, LMA8, was infiltrated with the liquid crystal mixture, E7. The measurements were performed with an interferometric setup. The fiber exhibits several spectral transmission windows in the visible wavelength regime that originate from the bandgap guiding mechanism. The dispersion of these windows is very unusual compared to typical fibers. Our measurements show that it can change from -2500 ps km(-1) nm(-1) to +2500 ps km(-1) nm(-1) within a spectral range of only 15 nm. This leads to multiple zero dispersion wavelengths in the visible wavelength range. PMID:25121882

  10. Supercontinuum generation enhancement in all-solid all-normal dispersion soft glass photonic crystal fiber pumped at 1550 nm

    NASA Astrophysics Data System (ADS)

    Siwicki, Bartłomiej; Klimczak, Mariusz; Stępień, Ryszard; Buczyński, Ryszard

    2015-10-01

    We study supercontinuum generation enhancement in an all-normal dispersion, all-glass photonic crystal fiber made of lead-silicate glasses. Dispersion characteristics were optimized through adjustment of regular hexagonal lattice of photonic crystal fiber in case of three different, thermally matched pairs of glasses. Supercontinuum generation was simulated with split-step Fourier method using the model that takes into account frequency-dependent effective mode area and losses, Raman response of the medium and temporal shape of the input pulse. An octave-spanning coherent supercontinuum has been obtained for all-glass fiber with lattice constant Λ = 1.73 μm and filling factor d/Λ = 0.8, made of silicate SF6/F2, spanning 850-2200 nm wavelengths in 10 dB dynamic range and pumped with pulses with energy as low as 3 nJ at 1550 nm.

  11. Broadband supercontinuum generation in normal dispersion all-solid photonic crystal fiber pumped near 1300 nm

    NASA Astrophysics Data System (ADS)

    Stepniewski, G.; Klimczak, M.; Bookey, H.; Siwicki, B.; Pysz, D.; Stepien, R.; Kar, A. K.; Waddie, A. J.; Taghizadeh, M. R.; Buczynski, R.

    2014-05-01

    We report on octave-spanning supercontinuum generation under pumping with 1360 nm, 120 fs pulses, in an all-solid, all-normal dispersion photonic crystal fiber. The fiber was drawn from thermally matched oxide soft glasses with a hexagonal lattice 35 µm in diameter, 2.5 µm solid core and pitch of Λ/d = 0.9. The fiber was designed for normal dispersion broadly flattened in the 1200-2800 nm range. Experimentally recorded supercontinuum spectrum covered a 900-1900 nm bandwidth and was reconstructed with good agreement using numerical modeling. To the best of our knowledge, this is the first report of an experimentally demonstrated octave-spanning supercontinuum bandwidth, reaching as far as 1900 nm in the all-normal dispersion regime.

  12. Design of chirped distributed Bragg reflector for octave-spanning frequency group velocity dispersion compensation in terahertz quantum cascade laser.

    PubMed

    Xu, Chao; Ban, Dayan

    2016-06-13

    The strategies and approaches of designing chirped Distributed Bragg Reflector for group velocity compensation in metal-metal waveguide terahertz quantum cascade laser are investigated through 1D and 3D models. The results show the depth of the corrugation periods plays an important role on achieving broad-band group velocity compensation in terahertz range. However, the deep corrugation also brings distortion to the group delay behavior. A two-section chirped DBR is proposed to provide smoother group delay compensation while still maintain the broad frequency range (octave) operation within 2 THz to 4 THz. PMID:27410366

  13. 0.54 μm resolution two-photon interference with dispersion cancellation for quantum optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Okano, Masayuki; Lim, Hwan Hong; Okamoto, Ryo; Nishizawa, Norihiko; Kurimura, Sunao; Takeuchi, Shigeki

    2015-12-01

    Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted much attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54 μm resolution two-photon interference, which surpasses the current record resolution 0.75 μm of low-coherence interference for OCT. In addition, the resolution for QOCT showed almost no change against the dispersion of a 1 mm thickness of water inserted in the optical path, whereas the resolution for OCT dramatically degrades. For this experiment, a highly-efficient chirped quasi-phase-matched lithium tantalate device was developed using a novel ‘nano-electrode-poling’ technique. The results presented here represent a breakthrough for the realization of quantum protocols, including QOCT, quantum clock synchronization, and more. Our work will open up possibilities for medical and biological applications

  14. 0.54 μm resolution two-photon interference with dispersion cancellation for quantum optical coherence tomography.

    PubMed

    Okano, Masayuki; Lim, Hwan Hong; Okamoto, Ryo; Nishizawa, Norihiko; Kurimura, Sunao; Takeuchi, Shigeki

    2015-01-01

    Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted much attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54 μm resolution two-photon interference, which surpasses the current record resolution 0.75 μm of low-coherence interference for OCT. In addition, the resolution for QOCT showed almost no change against the dispersion of a 1 mm thickness of water inserted in the optical path, whereas the resolution for OCT dramatically degrades. For this experiment, a highly-efficient chirped quasi-phase-matched lithium tantalate device was developed using a novel 'nano-electrode-poling' technique. The results presented here represent a breakthrough for the realization of quantum protocols, including QOCT, quantum clock synchronization, and more. Our work will open up possibilities for medical and biological applications. PMID:26657190

  15. 0.54 μm resolution two-photon interference with dispersion cancellation for quantum optical coherence tomography

    PubMed Central

    Okano, Masayuki; Lim, Hwan Hong; Okamoto, Ryo; Nishizawa, Norihiko; Kurimura, Sunao; Takeuchi, Shigeki

    2015-01-01

    Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted much attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54 μm resolution two-photon interference, which surpasses the current record resolution 0.75 μm of low-coherence interference for OCT. In addition, the resolution for QOCT showed almost no change against the dispersion of a 1 mm thickness of water inserted in the optical path, whereas the resolution for OCT dramatically degrades. For this experiment, a highly-efficient chirped quasi-phase-matched lithium tantalate device was developed using a novel ‘nano-electrode-poling’ technique. The results presented here represent a breakthrough for the realization of quantum protocols, including QOCT, quantum clock synchronization, and more. Our work will open up possibilities for medical and biological applications PMID:26657190

  16. White light for the fast lane: supercontinuum generation in all-normal dispersion fibers for ultrafast photonics

    NASA Astrophysics Data System (ADS)

    Heidt, Alexander M.

    2014-03-01

    This talk will give an overview of the unique properties of supercontinuum generation (SCG) in all-normal dispersion (ANDi) fibers pumped by ultrashort pulses and the possibilities they offer for ultrafast photonics applications. In contrast to their anomalously pumped counterparts, the SCG process in ANDi fibers conserves a single ultrashort pulse in the time domain, completely suppresses soliton formation and decay, and avoids noise-amplifying nonlinear dynamics. The resulting spectra combine the best of both worlds - the broad, more than octave-spanning bandwidths usually associated with anomalous dispersion pumping with the high temporal coherence, pulse-to-pulse stability and well-defined temporal pulse characteristics known from the normal dispersion regime. These characteristics are ideally suited for ultrafast photonics, and I will present application examples including the generation of high quality single-cycle pulses and their amplification, as well as ultrafast spectroscopy. This talk will also explore the exciting new possibilities enabled by extending this approach into the mid-IR spectral region using novel soft glass fiber designs.

  17. Optimal conditions for high-fidelity dispersive readout of a qubit with a photon-number-resolving detector

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrii

    2016-03-01

    We determine the optimal parameters for a simple and efficient scheme of dispersive readout of a qubit. Depending on the qubit state (ground or excited), the resonance of a cavity is shifted either to the red or to the blue side. Qubit state is inferred by detecting the photon number transmitted through the cavity. It turns out that this kind of detection provides better measurement fidelity than the detection of the presence or absence of photons only. We show that radiating the cavity on either of the frequencies it shifts to results in a suboptimal measurement. The optimal frequency of the probe photons is determined, as well as the optimal ratio of the shift to the resonator leakage. It is shown that to maximize the fidelity of a long-lasting measurement, it is sufficient to use the parameters optimizing the signal-to-noise ratio in the photon count. One can reach 99% fidelity for a single-shot measurement in various physical realizations of the scheme.

  18. Effects of polarization mode dispersion on polarization-entangled photons generated via broadband pumped spontaneous parametric down-conversion

    PubMed Central

    Lim, Hyang-Tag; Hong, Kang-Hee; Kim, Yoon-Ho

    2016-01-01

    An inexpensive and compact frequency multi-mode diode laser enables a compact two-photon polarization entanglement source via the continuous wave broadband pumped spontaneous parametric down-conversion (SPDC) process. Entanglement degradation caused by polarization mode dispersion (PMD) is one of the critical issues in optical fiber-based polarization entanglement distribution. We theoretically and experimentally investigate how the initial entanglement is degraded when the two-photon polarization entangled state undergoes PMD. We report an effect of PMD unique to broadband pumped SPDC, equally applicable to pulsed pumping as well as cw broadband pumping, which is that the amount of the entanglement degradation is asymmetrical to the PMD introduced to each quantum channel. We believe that our results have important applications in long-distance distribution of polarization entanglement via optical fiber channels. PMID:27174100

  19. Widely Wavelength-Tunable Blue-Shifted Dispersive Waves for Broadband Visible Wavelength Generation in a Photonic Crystal Fiber Cladding

    NASA Astrophysics Data System (ADS)

    Yuan, Jin-Hui; Sang, Xin-Zhu; Yu, Chong-Xiu; Shen, Xiang-Wei; Wang, Kui-Ru; Yan, Bin-Bin; Han, Ying; Zhou, Gui-Yao; Hou, Lan-Tian

    2012-10-01

    Blue-shifted dispersive waves (DWs) are efficiently generated from the red-shifted solitons by coupling the 120 fs pulses into the fundamental mode of the multi-knots of a photonic crystal fiber cladding. When the femtosecond pulses at the wavelength of 825 nm and the average power of 300 mW are coupled into knots 1-3, the conversion efficiency ηDW of 32% and bandwidth BDW of 50 nm are obtained. The ultrashort pulses generated by the DWs can be tunable over the whole visible wavelength by adjusting the wavelengths of the pump pulses coupled into different knots. It can be believed that this widely wavelength-tunable ultrashort visible pulse source has important applications in ultrafast photonics and resonant Raman scattering.

  20. Effects of polarization mode dispersion on polarization-entangled photons generated via broadband pumped spontaneous parametric down-conversion.

    PubMed

    Lim, Hyang-Tag; Hong, Kang-Hee; Kim, Yoon-Ho

    2016-01-01

    An inexpensive and compact frequency multi-mode diode laser enables a compact two-photon polarization entanglement source via the continuous wave broadband pumped spontaneous parametric down-conversion (SPDC) process. Entanglement degradation caused by polarization mode dispersion (PMD) is one of the critical issues in optical fiber-based polarization entanglement distribution. We theoretically and experimentally investigate how the initial entanglement is degraded when the two-photon polarization entangled state undergoes PMD. We report an effect of PMD unique to broadband pumped SPDC, equally applicable to pulsed pumping as well as cw broadband pumping, which is that the amount of the entanglement degradation is asymmetrical to the PMD introduced to each quantum channel. We believe that our results have important applications in long-distance distribution of polarization entanglement via optical fiber channels. PMID:27174100

  1. Effects of polarization mode dispersion on polarization-entangled photons generated via broadband pumped spontaneous parametric down-conversion

    NASA Astrophysics Data System (ADS)

    Lim, Hyang-Tag; Hong, Kang-Hee; Kim, Yoon-Ho

    2016-05-01

    An inexpensive and compact frequency multi-mode diode laser enables a compact two-photon polarization entanglement source via the continuous wave broadband pumped spontaneous parametric down-conversion (SPDC) process. Entanglement degradation caused by polarization mode dispersion (PMD) is one of the critical issues in optical fiber-based polarization entanglement distribution. We theoretically and experimentally investigate how the initial entanglement is degraded when the two-photon polarization entangled state undergoes PMD. We report an effect of PMD unique to broadband pumped SPDC, equally applicable to pulsed pumping as well as cw broadband pumping, which is that the amount of the entanglement degradation is asymmetrical to the PMD introduced to each quantum channel. We believe that our results have important applications in long-distance distribution of polarization entanglement via optical fiber channels.

  2. Coherent octave spanning near-infrared and visible supercontinuum generation in all-normal dispersion photonic crystal fibers.

    PubMed

    Heidt, Alexander M; Hartung, Alexander; Bosman, Gurthwin W; Krok, Patrizia; Rohwer, Erich G; Schwoerer, Heinrich; Bartelt, Hartmut

    2011-02-14

    We present the first detailed demonstrations of octave-spanning SC generation in all-normal dispersion photonic crystal fibers (ANDi PCF) in the visible and near-infrared spectral regions. The resulting spectral profiles are extremely flat without significant fine structure and with excellent stability and coherence properties. The key benefit of SC generation in ANDi PCF is the conservation of a single ultrashort pulse in the time domain with smooth and recompressible phase distribution. For the first time we confirm the exceptional temporal properties of the generated SC pulses experimentally and demonstrate their applicability in ultrafast transient absorption spectroscopy. The experimental results are in excellent agreement with numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking. To our knowledge, we present the broadest spectra generated in the normal dispersion regime of an optical fiber. PMID:21369202

  3. Design of hybrid photonic crystal fiber with elliptical and circular air holes analyzed for large flattened dispersion and high birefringence

    NASA Astrophysics Data System (ADS)

    Sharma, Varshali; Sharma, Ritu

    2016-04-01

    A design of two-dimensional hybrid photonic crystal fiber (PCF) with elliptical and circular air holes and its analyses for large flattened dispersion and high birefringence is presented. The PCF has hexagonal layout with triangular lattice. There are five rings around the solid core. The inner three rings around the core have elliptical air holes while the outer two rings have circular air holes. Three such layouts are designed, analyzed, and compared with the layout having only circular air hole using full-vector finite difference time domain method. The layout with hybrid structure having combined elliptical and circular air hole gives a large flattened dispersion of the order of 4.88 ps/nm/km for the wavelength range of 1.2 to 1.8 μm and magnitude of modal birefringence is 1.238×10-3 at 1.55-μm wavelength.

  4. Nonlinear dispersion-based incoherent photonic processing for microwave pulse generation with full reconfigurability.

    PubMed

    Bolea, Mario; Mora, José; Ortega, Beatriz; Capmany, José

    2012-03-12

    A novel all-optical technique based on the incoherent processing of optical signals using high-order dispersive elements is analyzed for microwave arbitrary pulse generation. We show an approach which allows a full reconfigurability of a pulse in terms of chirp, envelope and central frequency by the proper control of the second-order dispersion and the incoherent optical source power distribution, achieving large values of time-bandwidth product. PMID:22418557

  5. Low DSP complexity mid-haul mode-division multiplexing links utilizing wideband modal dispersion compensated two-mode fibers

    NASA Astrophysics Data System (ADS)

    Diamantopoulos, N. P.; Nakazawa, M.; Yoshida, Y.; Maruta, A.; Maruyama, R.; Kuwaki, N.; Matsuo, S.; Kitayama, K.

    2015-11-01

    Mode-division multiplexing (MDM) over wavelength division multiplexed (WDM) networks is studied, particularly for the deployment of metro area networks (MAN) using two-mode fibers (TMF). Full C-band differential mode group delay (DMGD)-compensated TMF links are adopted for decreasing the computational complexity of real-time multiple-input multiple-output (MIMO) signal processing. The effect of modal crosstalk to the maximum delay spread of the channel is validated through numerical simulations. Finally, the 2×2 MIMO channel state information (CSI) of a 102.6-km DMGD-compensated TMF link is experimentally estimated for mode path provisioning based upon routing and mode assignment (RMA) in MDM networks. The results confirm close-to-zero total DMGD value over the entire C-band.

  6. Tunable Bragg extraction of light in photonic quasi crystals: dispersed liquid crystalline metamaterials

    NASA Astrophysics Data System (ADS)

    Rippa, Massimo; Bobeico, Eugenia; Umeton, Cesare P.; Petti, Lucia

    2015-09-01

    By exploiting Metamaterials (MTMs) and Photonic Quasi-Crystals (PQCs), it is possible to realize man-made structures characterized by a selective EM response, which can be also controlled by combining the distinctive properties of reconfigurable soft-matter. By finely controlling lattice parameters of a given photonic structure, it is possible to optimize its extraction characteristics at a precise wavelength, or minimize the extraction of undesired modes. In general, however, once a structure is realized, its extraction properties cannot be varied. To cross this problem, it is possible to combine capabilities offered by both MTMs and PQCs with the reconfigurable properties of smart materials, such as Liquid Crystals (LCs); in this way, a completely new class of "reconfigurable metamaterials" (R-MTM) can be realized. We report here on the realization and characterization of a switchable photonic device, working in the visible range, based on nanostructured photonic quasi-crystals, layered with an azodye-doped nematic LC (NLC). The experimental characterization shows that its filtering effect is remarkable with its extraction spectra which can be controlled by applying an external voltage or by means of a laser light. The vertical extraction of the light, by the coupling of the modes guided by the PQC slab to the free radiation via Bragg scattering, consists of an extremely narrow orange emission band at 621 nm with a full width at half-maximum (FWHM) of 8 nm. In our opinion, these results represent a breakthrough in the realization of innovative MTMs based active photonic devices such as tunable MTMs or reconfigurable lasers and active filters.

  7. Heterodyne detection using spectral line pairing for spectral phase encoding optical code division multiple access and dynamic dispersion compensation.

    PubMed

    Yang, Yi; Foster, Mark; Khurgin, Jacob B; Cooper, A Brinton

    2012-07-30

    A novel coherent optical code-division multiple access (OCDMA) scheme is proposed that uses spectral line pairing to generate signals suitable for heterodyne decoding. Both signal and local reference are transmitted via a single optical fiber and a simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). To validate the idea, a 16 user fully loaded phase encoded system is simulated. Effects of fiber dispersion on system performance are studied as well. Both second and third order dispersion management is achieved by using a spectral phase encoder to adjust phase shifts of spectral components at the optical network unit (ONU). PMID:23038313

  8. Numerical simulation of supercontinuum generation in liquid-filled photonic crystal fibers with a normal flat dispersion profile

    NASA Astrophysics Data System (ADS)

    Tian, Liang; Wei, Li; Guoying, Feng

    2015-01-01

    A photonic crystal fiber (PCF) filled with commercial index-matching liquids is designed to control the dispersion properties of PCF. Numerical simulation of supercontinuum (SC) generation in these liquid-filled PCFs is then conducted at a temperature of 25 °C. The definition of spectral flatness measure (SFM) is introduced to quantitatively describe the SC flatness. Numerical simulations are performed to study the propagation of femtosecond pulse in the liquid-filled PCFs. Results show that using the index-matching liquids in PCF, the dispersion properties of the PCF can be easily engineered without changing in the geometry. Simulations also show that 50 fs pulses with a center wavelength of 1060 nm generate relatively flat SC spectra in the 25 cm-long PCF with two Oil2-filled rings. With an applied pump power of 24 kW, a flat (SFM=0.9670) spectral bandwidth of 700 nm (900-1400 nm) is achieved. Results further demonstrate that using index-matching liquids to fill the PCF inner ring can exactly control its dispersion properties and generate a flat SC spectrum in the specified wavelength region.

  9. Supercontinuum generation in square photonic crystal fiber with nearly zero ultra-flattened chromatic dispersion and fabrication tolerance analysis

    NASA Astrophysics Data System (ADS)

    Begum, Feroza; Namihira, Yoshinori; Kinjo, Tatsuya; Kaijage, Shubi

    2011-02-01

    This paper presents a simple index-guiding square photonic crystal fiber (SPCF) where the core is surrounded by air holes with two different diameters. The proposed design is simulated through an efficient full-vector modal solver based on the finite difference method with anisotropic perfectly matched layers absorbing boundary condition. The nearly zero ultra-flattened dispersion SPCF with low confinement loss, small effective area as well as broadband supercontinuum (SC) spectra is targeted. Numerical results show that the designed SPCF has been achieved at a nearly zero ultra-flattened dispersion of 0 ± 0.25 ps/(nm·km) in a wavelength range of 1.38 μm to 1.89 μm (510 nm band) which covers E, S, C, L and U communication bands, a low confinement loss of less than 10 -7 dB/m in a wavelength range of 1.3 μm to 2.0 μm and a wide SC spectrum (FWHM = 450 nm) by using picosecond pulses at a center wavelength of 1.55 μm. We then analyze the sensitivity of chromatic dispersion to small variations from the optimum value of specific structural parameters. The proposed index-guiding SPCF can be applicable in supercontinuum generation (SCG) covering such diverse fields as spectroscopy applications and telecommunication dense wavelength division multiplexing (DWDM) sources.

  10. Four-wave mixing stability in hybrid photonic crystal fibers with two zero-dispersion wavelengths.

    PubMed

    Sévigny, Benoit; Vanvincq, Olivier; Valentin, Constance; Chen, Na; Quiquempois, Yves; Bouwmans, Géraud

    2013-12-16

    The four-wave mixing process in optical fibers is generally sensitive to dispersion uniformity along the fiber length. However, some specific phase matching conditions show increased robustness to longitudinal fluctuations in fiber dimensions, which affect the dispersion, even for signal and idler wavelengths far from the pump. In this paper, we present the method by which this point is found, how the fiber design characteristics impact on the stable point and demonstrate the stability through propagation simulations using the non-linear Schrödinger equation. PMID:24514659

  11. Holographic polymer-dispersed liquid crystal Bragg grating integrated inside a solid core photonic crystal fiber.

    PubMed

    Zito, Gianluigi; Pissadakis, Stavros

    2013-09-01

    A polymer/liquid crystal-based fiber Bragg grating (PLC-FBG) is fabricated with visible two-beam holography by photo-induced modulation of a prepolymer/liquid crystal solution infiltrated into the hollow channels of a solid core photonic crystal fiber (PCF). The fabrication process and effects related to the photonic bandgap guidance into the infiltrated PCF, and characterization of the PLC-FBG, are discussed. Experimental data presented here demonstrate that the liquid crystal inclusions of the PLC-FBG lead to high thermal and bending sensitivities. The microscopic behavior of the polymer/liquid crystal phase separation inside the PCF capillaries is examined using scanning electron microscopy, and is discussed further. PMID:23988927

  12. 10.7 Gb/s electronic predistortion transmitter using commercial FPGAs and D/A converters implementing real-time DSP for chromatic dispersion and SPM compensation.

    PubMed

    Waegemans, Robert; Herbst, Stefan; Holbein, Ludwig; Watts, Philip; Bayvel, Polina; Fürst, Cornelius; Killey, Robert I

    2009-05-11

    We present an experimental demonstration of simultaneous chromatic dispersion and self-phase modulation compensation at 10.7 Gb/s using real-time electronic digital signal processing. This was achieved using a pre-distorting transmitter based on commercially available field programmable gate arrays and 21.4 GS/s, 6-bit resolution digital-to-analog converters. The digital signal processing employed look-up tables stored in RAM. This resulted in the achievement of a BER of 10(-6) at an OSNR of 16 dB after transmission over a 450 km link of uncompensated standard single mode fiber with + 4 dBm launch power. PMID:19434196

  13. Compensation of chromatic-dispersion for full-duplex radio-over-fiber links with vector signal transmission using frequency tripling

    NASA Astrophysics Data System (ADS)

    Gao, Chao; Huang, Shanguo; Xiao, Jinghua; Gao, Xinlu; Wang, Qian; Wei, Yongfeng; Zhai, Wensheng; Xu, Wenjing; Gu, Wanyi

    2014-10-01

    This paper demonstrates the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link, and a symmetry theory for compensation. A 60 GHz full-duplex ROF system with vector signal transmission using frequency-tripling modulation (FTM) is also proposed. The simulations for both 5 Gbps and 200 Mbps 16 QAM signal transmission show that the CD-induced CR can be entirely overcome due to the proposed method, and the proposed ROF schedule still maintains good performance even after 500 km of 200 Mbps vector signal transmission. Meanwhile, the central station is significantly simplified and cost-effective since only one 15 GHz local oscillator is needed for both the generation of an optical millimeter-wave signal and the carrier of the downlink intermediate-frequency (IF) signal.

  14. Temperature and refractive index sensing characteristics of an MZI-based multimode fiber-dispersion compensation fiber-multimode fiber structure

    NASA Astrophysics Data System (ADS)

    Sun, Hao; Yang, Shen; Zhang, Jing; Rong, Qiangzhou; Liang, Lei; Xu, Qinfang; Xiang, Guanghua; Feng, Dingyi; Du, Yanying; Feng, Zhongyao; Qiao, Xueguang; Hu, Manli

    2012-12-01

    We proposed an optical fiber sensor with simple multimode fiber (MMF)-dispersion compensation fiber (DCF)-multimode fiber structure based on Mach-Zehnder Interferometer (MZI) and researched its temperature and refractive index (RI) sensing characteristics. The sensing principle is based on the interference between core and cladding modes of DCF due to the large core diameter mismatch. Spectral analyses demonstrate that the transmission spectrum is mainly formed by the interference between the dominant excited cladding mode and core modes. The experimental results show that the proposed sensor has high temperature sensitivity of 0.118 nm/°C in the range of 20-250 °C and RI sensitivity of 66.32 nm/RIU within the linear sensing range of 1.33-1.39 RIU. Therefore, the characteristics of compact size, low cost, easy fabrication, high sensitivities, and good anti-interference ability make this sensor have extensive application prospects.

  15. Generation of multiple laser lines by sum-frequency mixing of continuous-wave Raman emissions from a dispersion-compensated optical cavity

    NASA Astrophysics Data System (ADS)

    Niigaki, Ryu; Kida, Yuichiro; Imasaka, Totaro

    2016-02-01

    Three color continuous-wave (CW) laser emissions with constant frequency separation are generated in the near-infrared (NIR) region using a dispersion-compensated optical cavity filled with hydrogen gas. By focusing these laser emissions into second-harmonic generation (SHG) crystals, multiple second harmonic signals and sum-frequency signals are generated in the near-ultraviolet (NUV) with a constant frequency spacing. Up to five colors of these NUV CW laser emissions can be generated simultaneously by using SHG crystals with different orientations. The interference between the second-harmonic signal of one NIR laser emission and the sum-frequency signal of the other two NIR emissions was observed experimentally, indicating mutual phase coherence among the NIR laser emissions. The phase coherence allows the synthesis of a train of ultrashort pulses with a THz repetition rate in both the NUV and the NIR by using the CW emission lines.

  16. Slow light in tunable low dispersion wide bandwidth photonic crystal waveguides infiltrated with magnetic fluids

    NASA Astrophysics Data System (ADS)

    Guillan-Lorenzo, Omar; Diaz-Otero, Francisco J.

    2016-01-01

    We analyze the properties of a photonic crystal waveguide as a device capable of producing slow light along a wide bandwidth. The proposed structure consists of a square lattice of hollow silicon cylinders rotated 45° immersed on a colloidal suspension of magnetic nanoparticles; this arrangement produces "U-type" group index-frequency curves. The cylinder inner radius is carefully chosen to maximize the normalized delay bandwidth product (NDBP) and the concentration of the magnetic fluid is changed in order to make the device tunable in frequency.

  17. Oxide-cladding aluminum nitride photonic crystal slab: Design and investigation of material dispersion and fabrication induced disorder

    NASA Astrophysics Data System (ADS)

    Melo, E. G.; Carvalho, D. O.; Ferlauto, A. S.; Alvarado, M. A.; Carreño, M. N. P.; Alayo, M. I.

    2016-01-01

    Photonic crystal slabs with a lower-index material surrounding the core layer are an attractive choice to circumvent the drawbacks in the fabrication of membranes suspended in air. In this work we propose a photonic crystal (PhC) slab structure composed of a triangular pattern of air holes in a multilayer thin film of aluminum nitride embedded in silicon dioxide layers designed for operating around 450 nm wavelengths. We show the design of an ideal structure and analyze the effects of material dispersion based on a first-order correction perturbation theory approach using dielectric functions obtained by experimental measurements of the thin film materials. Numerical methods were used to investigate the effects of fabrication induced disorder of typical nanofabrication processes on the bandgap size and spectral response of the proposed device. Deviation in holes radii and positions were introduced in the proposed PhC slab model with a Gaussian distribution profile. Impacts of slope in holes sidewalls that might result from the dry etching of AlN were also evaluated. The results show that for operation at the midgap frequency, slope in holes sidewalls is more critical than displacements in holes sizes and positions.

  18. Self-stabilized and dispersion-compensated passively mode-locked Yb:Yttrium aluminum garnet laser

    NASA Astrophysics Data System (ADS)

    Agnesi, A.; Guandalini, A.; Reali, G.

    2005-04-01

    Self-stabilized passive mode-locking of a diode-pumped Yb:yttrium aluminum garnet laser with a semiconductor saturable absorber was achieved using an off-phase-matching second-harmonic crystal. According to the numerical model, such a condition is accomplished by self-defocusing in the nonlinear crystal in the presence of positive intracavity dispersion. Robust mode locking with Fourier-limited 1.0-ps pulses was obtained, whereas mode locking, unassisted by the nonlinear crystal, yielded 2.2-ps pulses, with the laser operating near the edge of the stability region in order to minimize the saturation energy of the semiconductor device.

  19. Side mode suppression and dispersion compensation analysis of a 60 GHz radio-over-fibre system based on a gain switched laser

    NASA Astrophysics Data System (ADS)

    Martin, Eamonn; Barry, Liam

    2014-02-01

    The research and technical community have designated a band of 7 GHz between 57 and 64 GHz for short-range wireless communications. This paper utilizes a simple and cost effective technique for generating a 60 GHz millimeter-wave (mm-wave) signal using an optical comb source based on a gain-switched laser (GSL). This research investigates the effects unwanted comb lines have on the overall system performance with 2.5 Gb/s data transmission. To do this, a programmable optical filter is used to suppress the unwanted comb lines to varying levels. Bit-error rate (BER) measurements were carried out against received optical power to demonstrate the detrimental effects the unwanted comb lines have on the modulated mm-wave signal when not sufficiently suppressed. As chromatic dispersion is a limiting factor to the system's transmission distance, this work also investigates pre-compensation for dispersion utilizing the programmable group delay capabilities of the programmable optical filter, demonstrating the ability to extend the transmission distance by 12 km. All experimental results obtained are reinforced through simulation.

  20. Instrumentation for time-resolved dispersive studies at Advanced Photon Source beamline 1-BM

    SciTech Connect

    Brauer, S.; Rodricks, B.

    1996-07-01

    We describe progress in optics and instrumentation at beamline 1-BM, designed in part for time-resolved dispersive x-ray absorption fine structure (XAFS) measurements. The key optical element is a horizontally focusing curved-crystal monochromator that invokes a 4-point bending scheme and a liquid-metal cooling bath. The device has been designed for dispersive studies in the 5-24 keV range, with a horizontal focal spot size of {le}100 micrometers FWHM. To minimize thermal distortions and thermal equilibration time, the 355 {times} 32 {times} 0.8 mm crystal is nearly half submerged in a bath of Ga-In-Sn-Zn alloy, which thermally couples the crystal to the water-cooled Cu frame, while permitting the required crystal bending. Harmonic rejection, focusing schemes and the novel spectrometer positioning system will be described. For microsecond-resolution time-resolved studies, a fast CCD streak camera detector has been developed. Results from commissioning tests of the instrumentation are described. 11 refs., 4 figs.

  1. Tellurite glass defect-core spiral photonic crystal fiber with low loss and large negative flattened dispersion over S + C + L + U wavelength bands.

    PubMed

    Hasan, Md Rabiul; Hasan, Md Imran; Anower, Md Shamim

    2015-11-10

    A defected-core spiral photonic crystal fiber is proposed to achieve very large negative flattened dispersion and small confinement loss. Simulation results reveal that the designed structure exhibits very large flattened dispersion over S+C+L+U wavelength bands and an average dispersion of about -720.7  ps nm(-1) km(-1) with an absolute dispersion variation of 12.7  ps nm(-1)  km(-1) over the wavelength ranging from 1.45 to 1.65 μm. The proposed fiber has five air-hole rings in the cladding leading to very small confinement loss of 0.00111  dB/km at the excitation wavelength of 1.55 μm. The tolerance of the fiber dispersion of ±2% changing in the structural parameters is investigated for practical conditions. PMID:26560773

  2. Common approach for compensation of axial motion artifacts in swept-source OCT and dispersion in Fourier-domain OCT.

    PubMed

    Hillmann, Dierck; Bonin, Tim; Lührs, Christian; Franke, Gesa; Hagen-Eggert, Martin; Koch, Peter; Hüttmann, Gereon

    2012-03-12

    Swept-source optical coherence tomography (SS-OCT) is sensitive to sample motion during the wavelength sweep, which leads to image blurring and image artifacts. In line-field and full-field SS-OCT parallelization is achieved by using a line or area detector, respectively. Thus, approximately 1000 lines or images at different wavenumbers are acquired. The sweep duration is identically with the acquisition time of a complete B-scan or volume, rendering parallel SS-OCT more sensitive to motion artifacts than scanning OCT. The effect of axial motion on the measured spectra is similar to the effect of non-balanced group velocity dispersion (GVD) in the interferometer arms. It causes the apparent optical path lengths in the sample arm to vary with the wavenumber. Here we propose the cross-correlation of sub-bandwidth reconstructions (CCSBR) as a new algorithm that is capable of detecting and correcting the artifacts induced by axial motion in line-field or full-field SS-OCT as well as GVD mismatch in any Fourier-domain OCT (FD-OCT) setup. By cross-correlating images which were reconstructed from a limited spectral range of the interference signal, a phase error is determined which is used to correct the spectral modulation prior to the calculation of the A-scans. Performance of the algorithm is demonstrated on in vivo full-field SS-OCT images of skin and scanning FD-OCT of skin and retina. PMID:22418560

  3. 140-fs duration and 60-W peak power blue-violet optical pulses generated by a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compressor.

    PubMed

    Kono, Shunsuke; Watanabe, Hideki; Koda, Rintaro; Fuutagawa, Noriyuki; Narui, Hironobu

    2015-12-14

    Blue-violet optical pulses of 140-fs duration and 60-W peak power were obtained from a dispersion-compensated GaInN mode-locked semiconductor laser diode using a nonlinear pulse compression technique. Wavelength-dependent group velocity dispersion expressed by third-order phase dispersion was applied to the optical pulses using a pulse compressor with a spatial light modulator. The obtained optical pulses had the shortest duration ever obtained for a mode-locked semiconductor laser diode using edge-emitting type devices. PMID:26698968

  4. An Overview of High-Resolution, Non-Dispersive, Imaging Spectrometers for High-Energy Photons

    NASA Technical Reports Server (NTRS)

    Kilbourne, Caroline

    2010-01-01

    High-resolution x-ray spectroscopy has become a powerful tool for studying the evolving universe. The grating spectrometers on the XMM and Chandra satellites initiated a new era in x-ray astronomy. Despite their successes, there is still need for instrumentation that can provide higher spectral resolution with high throughput in the Fe-K band and for extended sources. What is needed is a non-dispersive imaging spectrometer - essentially a 14-bit x-ray color camera. And a requirement for a nondispersive spectrometer designed to provide eV-scale spectral resolution is a temperature below 0.1 K. The required spectral resolution and the constraints of thermodynamics and engineering dictate the temperature regime nearly independently of the details of the sensor or the read-out technology. Low-temperature spectrometers can be divided into two classes - - equilibrium and non-equilibrium. In the equilibrium devices, or calorimeters, the energy is deposited in an isolated thermal mass and the resulting increase in temperature is measured. In the non-equilibrium devices, the absorbed energy produces quantized excitations that are counted to determine the energy. The two approaches have different strong points, and within each class a variety of optimizations have been pursued. I will present the basic fundamentals of operation and the details of the most successful device designs to date. I will also discuss how the measurement priorities (resolution, energy band, count rate) influence the optimal choice of detector technology.

  5. All-fiber nonlinearity- and dispersion-managed dissipative soliton nanotube mode-locked laser

    SciTech Connect

    Zhang, Z.; Popa, D. Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C.; Ilday, F. Ö.

    2015-12-14

    We report dissipative soliton generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative solitons with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally compressed to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.

  6. Simple and complete formulation to compute propagation constants of photonic crystal fibers and predict their total chromatic dispersion

    NASA Astrophysics Data System (ADS)

    Kundu, Dipankar; Sarkar, Somenath

    2012-06-01

    Within the scalar framework, a simple and complete formulation for the normalized propagation constants of the infinite cladding region of a photonic crystal fiber (PCF) with triangular lattice of air-holes is presented, which is dependent only on the ratio of air-hole diameters and their separation. The accuracy of the proposed formulation is depicted by comparing our results with those obtained by Russell. Then the refractive indices of the fundamental space-filling mode (nFSM) in the cladding region of the PCF from Russell's equation and the proposed relations are evaluated and the two indices are observed to match quite excellently for different values of relative air-hole size and wavelength. An equivalence between the two approaches of Russell and Saitoh is also sought. Finally, in order to check the validity of the formulation in problems of practical interest, the proposed relations are applied to evaluate the total chromatic dispersion in a PCF, treating it as a conventional step index fiber having its core and cladding indices as those of silica and nFSM, respectively. On comparison with the available results of Saitoh, the results match nicely.

  7. Photoionization-Induced Emission of Tunable Few-Cycle Midinfrared Dispersive Waves in Gas-Filled Hollow-Core Photonic Crystal Fibers.

    PubMed

    Novoa, D; Cassataro, M; Travers, J C; Russell, P St J

    2015-07-17

    We propose a scheme for the emission of few-cycle dispersive waves in the midinfrared using hollow-core photonic crystal fibers filled with noble gas. The underlying mechanism is the formation of a plasma cloud by a self-compressed, subcycle pump pulse. The resulting free-electron population modifies the fiber dispersion, allowing phase-matched access to dispersive waves at otherwise inaccessible frequencies, well into the midinfrared. Remarkably, the pulses generated turn out to have durations of the order of two optical cycles. In addition, this ultrafast emission, which occurs even in the absence of a zero dispersion point between pump and midinfrared wavelengths, is tunable over a wide frequency range simply by adjusting the gas pressure. These theoretical results pave the way to a new generation of compact, fiber-based sources of few-cycle midinfrared radiation. PMID:26230794

  8. A photon counting and a squeezing measurement method by the exact absorption and dispersion spectrum of Λ-type Atoms.

    PubMed

    Naeimi, Ghasem; Alipour, Samira; Khademi, Siamak

    2016-01-01

    Recently, the master equations for the interaction of two-mode photons with a three-level Λ-type atom are exactly solved for the coherence terms. In this paper the exact absorption spectrum is applied for the presentation of a non-demolition photon counting method, for a few number of coupling photons, and its benefits are discussed. The exact scheme is also applied where the coupling photons are squeezed and the photon counting method is also developed for the measurement of the squeezing parameter of the coupling photons. PMID:27610321

  9. Supercontinuum generation at 1.55 μm in an all-normal dispersion photonic crystal fiber with high-repetition-rate picosecond pulses

    NASA Astrophysics Data System (ADS)

    Xu, Yong-zhao; Han, Tao; Song, Jian-xun; Ling, Dong-xiong; Li, Hong-tao

    2014-11-01

    We demonstrate the generation of supercontinuum (SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1 552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber (PCF) with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking (WB).

  10. Peculiarities of spectral properties of a one-dimensional photonic crystal with an anisotropic defect layer of the nanocomposite with resonant dispersion

    SciTech Connect

    Vetrov, S Ya; Timofeev, I V; Pankin, P S

    2014-09-30

    We have studied the spectral properties of a one-dimensional photonic crystal with a structure defect that represents an anisotropic nanocomposite layer sandwiched between two multilayer dielectric mirrors. The nanocomposite consists of metallic nanoscale inclusions of orientationally ordered spheroidal shape, dispersed in a transparent matrix, and is characterised by an effective resonant permittivity. Each of the two orthogonal polarisations of probe radiation corresponds to a particular plasmon resonant frequency of the nanocomposite. The problem of calculating the transmittance spectrum of the waves with s- and p-polarisations for such structures is solved. Spectral manifestation of splitting of the defect mode depending on the structure parameters and volumetric fraction of the nanospheroids is studied. The essential dependence of the position of maxima of the defect modes in the bandgap of the photonic crystal and their splitting on the incidence angle, polarisation, and the ratio of lengths of the polar and equatorial semi-axes of the spheroidal nanoparticles is shown. (photonic crystals)

  11. Investigation of x-ray photon counting using a silicon-PIN diode and its application to energy-dispersive computed tomography

    NASA Astrophysics Data System (ADS)

    Kodama, Hajime; Sato, Eiichi; Sagae, Michiaki; Hagiwara, Osahiko; Matsukiyo, Hiroshi; Osawa, Akihiro; Enomoto, Toshiyuki; Watanabe, Manabu; Kusachi, Shinya; Sato, Shigehiro; Ogawa, Akira

    2013-09-01

    X-ray photon counting was performed using a readymade silicon-PIN photodiode (Si-PIN-PD) at tube voltages ranging from 42 to 60 kV, and X-ray photons are directly detected using the 100 MHz Si-PIN-PD without a scintillator. Photocurrent from the diode is amplified using charge-sensitive and shaping amplifiers. Using a multichannel analyzer, X-ray spectra at a tube voltage of 60 kV could easily be measured. The photon-counting computed tomography (PCCT) is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by the linear scan. In the PC-CT, we confirmed the energy-dispersive effect with changes in lower-level voltage of the event pulse using a comparator.

  12. Dispersion optimization of photonic crystal fiber long-period gratings for a high-sensitivity refractive index sensing

    NASA Astrophysics Data System (ADS)

    Kanka, Jiri

    2011-05-01

    Photonic crystal fiber long-period gratings (PCF-LPGs) operating near the phase-matching turning point to achieve high sensitivity to the refractive index of gas and liquid analytes infiltrated into cladding air holes are designed by numerical optimization. The vectorial finite element method is employed for the modal analysis of an index-guiding PCF and the calculation of the phase matching curves. The geometrical parameters of PCF (pitch and diameter of air holes arranged in a periodic triangular array) are optimized by using the down-hill simplex technique to engineer the dispersion of modes coupled by a LPG to obtain the turning point in the phase-matching curve at a desired wavelength for a given analyte refractive index. The resonant wavelength is subsequently extremely sensitive to the analyte refractive index, however, its large shifts can be detected with a substantially reduced resolution because the resonance dip in the LPG transmission spectrum is very broad. On the other hand, the broad resonance provides a broadband operation of a PCF-LPG sensor and its high sensitivity to the refractive index can still be achieved by relying on changes in the coupling strength (and consequently in the transmission loss) rather than in the resonant wavelength of LPG. We consider coupling between the fundamental core mode and the first-order symmetric cladding mode. We also explore an alternative approach based on coupling between the fundamental core mode and the fundamental space-filling mode instead of the individual cladding mode. The PCF-LPG structure optimized for refractive-index sensing is also assessed for label-free biosensing.

  13. Coherent supercontinuum generation up to 2.3 µm in all-solid soft-glass photonic crystal fibers with flat all-normal dispersion.

    PubMed

    Klimczak, Mariusz; Siwicki, Bartłomiej; Skibiński, Piotr; Pysz, Dariusz; Stępień, Ryszard; Heidt, Alexander; Radzewicz, Czesław; Buczyński, Ryszard

    2014-07-28

    Supercontinuum spanning over an octave from 900 - 2300 nm is reported in an all-normal dispersion, soft glass photonic crystal fiber. The all-solid microstructured fiber was engineered to achieve a normal dispersion profile flattened to within -50 to -30 ps/nm/km in the wavelength range of 1100 - 2700 nm. Under pumping with 75 fs pulses centered at 1550 nm, the recorded spectral flatness is 7 dB in the 930 - 2170 nm range, and significantly less if cladding modes present in the uncoated photonic crystal fiber are removed. To the best of our knowledge, this is the first report of an octave-spanning, all-normal dispersion supercontinuum generation in a non-silica microstructured fiber, where the spectrum long-wavelength edge is red-shifted to as far as 2300 nm. This is also an important step in moving the concept of ultrafast coherent supercontinuum generation in all-normal dispersion fibers further towards the mid-infrared spectral region. PMID:25089500

  14. Shifted dispersion-induced radio-frequency fading in microwave photonic filters using a dual-input Mach-Zehnder electro-optic modulator.

    PubMed

    Li, Liwei; Yi, Xiaoke; Huang, Thomas X H; Minasian, Robert A

    2013-04-01

    A simple microwave photonic processor structure with single passband response, and widely tunable capability, is demonstrated. It is based on the principle of shifted dispersion-induced radio-frequency (RF) fading by using a dual-input Mach-Zehnder electro-optic modulator (EOM) that is fed from a broadband optical source with unbalanced input fiber lengths into the upper and lower arms of the EOM, in combination with a dispersive medium. This topology consequently produces a spectral response equivalent to the curve of the dispersion-induced RF fading that is shifted from the conventional baseband location to high frequencies. Therefore, an equivalent single passband is formed without the requirement of the conventional tap coefficients. Experimental results verify the structure and demonstrate a continuously tunable microwave filter exhibiting shape invariance and a single passband. In addition, the filter response sidelobe suppression is also significantly improved by applying a Gaussian windowed profile to the broadband optical source. PMID:23546278

  15. Supercontinuum generation in the vacuum ultraviolet through dispersive-wave and soliton-plasma interaction in a noble-gas-filled hollow-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Ermolov, A.; Mak, K. F.; Frosz, M. H.; Travers, J. C.; Russell, P. St. J.

    2015-09-01

    We report on the generation of a three-octave-wide supercontinuum extending from the vacuum ultraviolet (VUV) to the near infrared, spanning at least 113-1000 nm (i.e., 11 -1.2 eV ), in He-filled hollow-core kagome-style photonic crystal fiber. Numerical simulations confirm that the main mechanism is an interaction between dispersive-wave emission and plasma-induced blue-shifted soliton recompression around the fiber zero dispersion frequency. The VUV part of the supercontinuum, the modeling of which proves to be coherent and possesses a simple phase structure, has sufficient bandwidth to support single-cycle pulses of 500 asec duration. We also demonstrate, in the same system, the generation of narrower-band VUV pulses through dispersive-wave emission, tunable from 120 to 200 nm with efficiencies exceeding 1 % and VUV pulse energies in excess of 50 nJ.

  16. Optimizing single-nanoparticle two-photon microscopy by in situ adaptive control of femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Li, Donghai; Deng, Yongkai; Chu, Saisai; Jiang, Hongbing; Wang, Shufeng; Gong, Qihuang

    2016-07-01

    Single-nanoparticle two-photon microscopy shows great application potential in super-resolution cell imaging. Here, we report in situ adaptive optimization of single-nanoparticle two-photon luminescence signals by phase and polarization modulations of broadband laser pulses. For polarization-independent quantum dots, phase-only optimization was carried out to compensate the phase dispersion at the focus of the objective. Enhancement of the two-photon excitation fluorescence intensity under dispersion-compensated femtosecond pulses was achieved. For polarization-dependent single gold nanorod, in situ polarization optimization resulted in further enhancement of two-photon photoluminescence intensity than phase-only optimization. The application of in situ adaptive control of femtosecond pulse provides a way for object-oriented optimization of single-nanoparticle two-photon microscopy for its future applications.

  17. Nonlinear polarization dynamics in a weakly birefringent all-normal dispersion photonic crystal fiber: toward a practical coherent fiber supercontinuum laser

    PubMed Central

    Tu, Haohua; Liu, Yuan; Liu, Xiaomin; Turchinovich, Dmitry; Lægsgaard, Jesper; Boppart, Stephen A.

    2012-01-01

    Dispersion-flattened dispersion-decreased all-normal dispersion (DFDD-ANDi) photonic crystal fibers have been identified as promising candidates for high-spectral-power coherent supercontinuum (SC) generation. However, the effects of the unintentional birefringence of the fibers on the SC generation have been ignored. This birefringence is widely present in nonlinear non-polarization maintaining fibers with a typical core size of 2 µm, presumably due to the structural symmetry breaks introduced in the fiber drawing process. We find that an intrinsic form-birefringence on the order of 10−5 profoundly affects the SC generation in a DFDD-ANDi photonic crystal fiber. Conventional simulations based on the scalar generalized nonlinear Schrödinger equation (GNLSE) fail to reproduce the prominent observed features of the SC generation in a short piece (9-cm) of this fiber. However, these features can be qualitatively or semi-quantitatively understood by the coupled GNLSE that takes into account the form-birefringence. The nonlinear polarization effects induced by the birefringence significantly distort the otherwise simple spectrotemporal field of the SC pulses. We therefore propose the fabrication of polarization-maintaining DFDD-ANDi fibers to avoid these adverse effects in pursuing a practical coherent fiber SC laser. PMID:22274457

  18. Spatial and electrical switching of defect modes in a photonic bandgap device with a polymer-dispersed liquid crystal defect layer.

    PubMed

    Wu, Po-Chang; Yeh, En-Rong; Zyryanov, Victor Ya; Lee, Wei

    2014-08-25

    This paper investigates the spectral properties of a one-dimensional photonic crystal (PC) containing an inhomogeneous polymer- dispersed liquid crystal (PDLC) as a defect layer. Experimental results indicate that the voltage-induced reorientation of LC molecules between the light-scattering and transparent states in the PDLC enables the electrical tuning of the transmittance of defect-mode peaks in the spectrum of the PC/PDLC cell. Specifically, owing to the unique configuration of the spatial distribution of LC droplet sizes in the defect layer, a concept concerning the spatial switching in the wavelength of defect modes is proposed. As a result, the PC/PDLC hybrid cell is suggested as a potential element for realizing an electrically tunable and spatially switchable photonic bandgap device, which is polarizer-free and requires no alignment layers in the fabrication process. PMID:25321237

  19. All-Optical 1-to-8 Wavelength Multicasting at 20 Gbit/s Exploiting Self-Phase Modulation in Dispersion Flattened Highly Nonlinear Photonic Crystal Fiber

    PubMed Central

    Hui, Zhan-Qiang

    2014-01-01

    All-optical multicasting of performing data routing from single node to multiple destinations in the optical domain is promising for next generation ultrahigh-peed photonic networks. Based on the self-phase modulation in dispersion flattened highly nonlinear photonic crystal fiber and followed spectral filtering, simultaneous 1-to-8 all-optical wavelength multicasting return-to-zero (RZ) signal at 20 Gbit/s with 100 GHz channel spaced is achieved. Wavelength tunable range and dynamic characteristic of proposed wavelength multicasting scheme is further investigated. The results show our designed scheme achieve operation wavelength range of 25 nm, OSNR of 32.01 dB and Q factor of 12.8. Moreover, the scheme has simple structure as well as high tolerance to signal power fluctuation. PMID:24711738

  20. Scalar generalized nonlinear Schrödinger equation-quantified continuum generation in an all-normal dispersion photonic crystal fiber for broadband coherent optical sources.

    PubMed

    Tu, Haohua; Liu, Yuan; Lægsgaard, Jesper; Sharma, Utkarsh; Siegel, Martin; Kopf, Daniel; Boppart, Stephen A

    2010-12-20

    We quantitatively predict the observed continuum-like spectral broadening in a 90-mm weakly birefringent all-normal dispersion-flattened photonic crystal fiber pumped by 1041-nm 229-fs 76-MHz pulses from a solid-state Yb:KYW laser. The well-characterized continuum pulses span a bandwidth of up to 300 nm around the laser wavelength, allowing high spectral power density pulse shaping useful for various coherent control applications. We also identify the nonlinear polarization effect that limits the bandwidth of these continuum pulses, and therefore report the path toward a series of attractive alternative broadband coherent optical sources. PMID:21197060

  1. Scalar generalized nonlinear Schrödinger equation-quantified continuum generation in an all-normal dispersion photonic crystal fiber for broadband coherent optical sources

    PubMed Central

    Tu, Haohua; Liu, Yuan; Lægsgaard, Jesper; Sharma, Utkarsh; Siegel, Martin; Kopf, Daniel; Boppart, Stephen A.

    2010-01-01

    We quantitatively predict the observed continuum-like spectral broadening in a 90-mm weakly birefringent all-normal dispersion-flattened photonic crystal fiber pumped by 1041-nm 229-fs 76-MHz pulses from a solid-state Yb:KYW laser. The well-characterized continuum pulses span a bandwidth of up to 300 nm around the laser wavelength, allowing high spectral power density pulse shaping useful for various coherent control applications. We also identify the nonlinear polarization effect that limits the bandwidth of these continuum pulses, and therefore report the path toward a series of attractive alternative broadband coherent optical sources. PMID:21197060

  2. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    PubMed

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. PMID:27607941

  3. Influence of pump fiber laser conditions at 1550 nm on broadband infrared supercontinuum generation in all-solid all-normal dispersion photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Klimczak, Mariusz; Siwicki, Bartłomiej; Soboń, Grzegorz; Sotor, Jarosław; Pysz, Dariusz; Stepień, Ryszard; Martynkien, Tadeusz; Abramski, Krzysztof; Buczyński, Ryszard

    2014-02-01

    Supercontinuum generation (SG) in photonic crystal fibers (PCFs) usually takes advantage of soliton dynamics, when pump wavelength is located in the anomalous dispersion region near the zero-dispersion wavelength of the fiber. This results in broader bandwidth than pumping in the normal dispersion region (NDR). SG in NDR is of interest, because of its potential for high degree of coherence and low intensity fluctuations. It was experimentally demonstrated in silica fibers and PCFs pumped around 1000 nm, covering the visible and near-infrared. We developed an all-solid PCF with hexagonal lattice made from N-F2 capillaries, with lattice constant Λ=2.275 μm, filling factor d/Λ=0.9, and a solid N-F2 core with 2,5μm diameter. The capillaries were filled with thermally matched borosilicate glass rods with lower refractive index. The PCF has all-normal dispersion, flattened within 1400- 2750 nm (-35 to -29 ps/nm/km) and a local maximum of -29 ps/nm/km at 1550 nm. Measured attenuation in 1500-1600 nm is around 3.2 dB/m. Nonlinear coefficient calculated at 1550 nm is 17/W/m. We numerically investigate the evolution of supercontinuum formation with a maximum bandwidth of 900-2400 nm. Considered pump pulse lengths were between 1 ps and 50 fs, with corresponding peak powers from 20 kW to 200 kW. Measured coupling efficiency using 20× microscope objective was 50%. One-photon-per-mode noise was used to simulate pump noise and multi-shot SG spectra were calculated. Preliminary experimental results are in good agreement with developed model.

  4. The right circular polarized waves in the three-dimensional anisotropic dispersive photonic crystals consisting of the magnetized plasma and uniaxial material as the Faraday effects considered

    SciTech Connect

    Zhang, Hai-Feng E-mail: lsb@nuaa.edu.cn; Liu, Shao-Bin E-mail: lsb@nuaa.edu.cn; Tang, Yi-Jun; Zhen, Jian-Ping

    2014-03-15

    In this paper, the properties of the right circular polarized (RCP) waves in the three-dimensional (3D) dispersive photonic crystals (PCs) consisting of the magnetized plasma and uniaxial material with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, which the homogeneous anisotropic dielectric spheres (the uniaxial material) immersed in the magnetized plasma background, as the Faraday effects of magnetized plasma are considered (the incidence electromagnetic wave vector is parallel to the external magnetic field at any time). The equations for calculating the anisotropic photonic band gaps (PBGs) for the RCP waves in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and a flatbands region can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, anisotropic dielectric filling factor, plasma frequency, and plasma cyclotron frequency (the external magnetic field) on the properties of first two anisotropic PBGs for the RCP waves are investigated in detail, respectively. The numerical results show that the anisotropy can open partial band gaps in fcc lattices at U and W points, and the complete PBGs for the RCP waves can be achieved compared to the conventional 3D dispersive PCs composed of the magnetized plasma and isotropic material. It is also shown that the first two anisotropic PBGs can be tuned by those parameters as mentioned above. Those PBGs can be enlarged by introducing the uniaxial material into such 3D PCs as the Faraday effects are considered.

  5. Trimming the threshold dispersion below 10 e-rms in a large area readout IC working in a single photon counting mode

    NASA Astrophysics Data System (ADS)

    Kmon, P.; Maj, P.; Gryboś, P.; Szczygieł, R.

    2016-01-01

    We present a new method of an in-pixel threshold dispersion correction implemented in a prototype readout integrated circuit (IC) operating in a single photon counting mode. The new threshold correction method was implemented in a readout IC of area 9.6× 14.9 mm2 containing 23552 square pixels with the pitch of 75 μm designed and fabricated in CMOS 130 nm technology. Each pixel of the IC consists of a charge sensitive amplifier, a shaper, two discriminators, two 14-bit counters and a low-area trim DACs for threshold correction. The user can either control the range of the trim DAC globally for all the pixels in the integrated circuit or modify the trim DACs characteristics locally in each pixel independently. Using a simulation tool based on the Monte-Carlo methods, we estimated how much we could improve the offset trimming by increasing the number of bits in the trim DACs or implementing additional bits in a pixel to modify the characteristics of the trim DACs. The measurements of our IC prototype show that it is possible to reduce the effective threshold dispersion in large-area single-photon counting chips below 10 electrons rms.

  6. Parametric down-conversion with optimized spectral properties in nonlinear photonic crystals

    SciTech Connect

    Corona, Maria; U'Ren, Alfred B.

    2007-10-15

    We study the joint spectral properties of photon pairs generated by spontaneous parametric down-conversion in a one-dimensional nonlinear photonic crystal in a collinear, degenerate, type-II geometry. We show that the photonic crystal properties may be exploited to compensate for material dispersion and obtain photon pairs that are nearly factorable, in principle, for arbitrary materials and spectral regions, limited by the ability to fabricate the nonlinear crystal with the required periodic variation in the refractive indices for the ordinary and extraordinary waves.

  7. Cryogenic thermoelectric (QVD) detectors: Emerging technique for fast single-photon counting and non-dispersive energy characterization

    NASA Astrophysics Data System (ADS)

    Gulian, A.; Wood, K.; van Vechten, D.; Fritz, G.

    2004-09-01

    ''QVD'' detectors are based on thermoelectric heat-to-voltage (Q → V) conversion and digital (V → D) readout. We have devised and analyzed the performance of QVD detectors with several different sensor designs that enable use of high thermoelectric figure of merit samples, be they of thin film, bulk crystal, or whisker form. Our first QVD devices had the well-studied material Au-Fe as thin film sensors. More recently, we have confirmed the literature reports of substantially higher Seebeck coefficient at cryogenic temperatures in lanthanum (cerium) hexaborides. We have also investigated the kinetic properties of La(Ce)B6 crystals with different La-Ce ratios. Currently we are exploring prototype devices based on bulk single-crystalline sensors. These include a successfully tested candidate with a sharp-end hexaboride sensor and small-size bismuth absorber - a whisker prototype. In theory, QVD sensors are competitive with superconducting tunnel junction (STJ) and transition edge sensor (TES) devices in energy resolution ability. However, QVD sensors ought to be able to respond at very much faster rates than these competitors; the lanthanum-cerium hexaboride sensors are expected to reach rates of 100 MHz counting rates for UV/optical photons. In addition to traditional astrophysical applications, these detectors can be applied to the tasks of quantum computing and communication.

  8. The ground states of iron(III) porphines: role of entropy-enthalpy compensation, Fermi correlation, dispersion, and zero-point energies.

    PubMed

    Kepp, Kasper P

    2011-10-01

    Porphyrins are much studied due to their biochemical relevance and many applications. The density functional TPSSh has previously accurately described the energy of close-lying electronic states of transition metal systems such as porphyrins. However, a recent study questioned this conclusion based on calculations of five iron(III) porphines. Here, we compute the geometries of 80 different electronic configurations and the free energies of the most stable configurations with the functionals TPSSh, TPSS, and B3LYP. Zero-point energies and entropy favor high-spin by ~4kJ/mol and 0-10kJ/mol, respectively. When these effects are included, and all electronic configurations are evaluated, TPSSh correctly predicts the spin of all the four difficult phenylporphine cases and is within the lower bound of uncertainty of any known theoretical method for the fifth, iron(III) chloroporphine. Dispersion computed with DFT-D3 favors low-spin by 3-53kJ/mol (TPSSh) or 4-15kJ/mol (B3LYP) due to the attractive r(-6) term and the shorter distances in low-spin. The very large and diverse corrections from TPSS and TPSSh seem less consistent with the similarity of the systems than when calculated from B3LYP. If the functional-specific corrections are used, B3LYP and TPSSh are of equal accuracy, and TPSS is much worse, whereas if the physically reasonable B3LYP-computed dispersion effect is used for all functionals, TPSSh is accurate for all systems. B3LYP is significantly more accurate when dispersion is added, confirming previous results. PMID:21855825

  9. Compensation Chemistry

    ERIC Educational Resources Information Center

    Roady, Celia

    2008-01-01

    Congress, the news media, and the Internal Revenue Service (IRS) continue to cast a wary eye on the compensation of nonprofit leaders. Hence, any college or university board that falls short of IRS expectations in its procedures for setting the president's compensation is putting the president, other senior officials, and board members at…

  10. Dramatic Raman Gain Suppression in the Vicinity of the Zero Dispersion Point in a Gas-Filled Hollow-Core Photonic Crystal Fiber

    NASA Astrophysics Data System (ADS)

    Bauerschmidt, S. T.; Novoa, D.; Russell, P. St. J.

    2015-12-01

    In 1964 Bloembergen and Shen predicted that Raman gain could be suppressed if the rates of phonon creation and annihilation (by inelastic scattering) exactly balance. This is only possible if the momentum required for each process is identical, i.e., phonon coherence waves created by pump-to-Stokes scattering are identical to those annihilated in pump-to-anti-Stokes scattering. In bulk gas cells, this can only be achieved over limited interaction lengths at an oblique angle to the pump axis. Here we report a simple system that provides dramatic Raman gain suppression over long collinear path lengths in hydrogen. It consists of a gas-filled hollow-core photonic crystal fiber whose zero dispersion point is pressure adjusted to lie close to the pump laser wavelength. At a certain precise pressure, stimulated generation of Stokes light in the fundamental mode is completely suppressed, allowing other much weaker phenomena such as spontaneous Raman scattering to be explored at high pump powers.

  11. Dramatic Raman Gain Suppression in the Vicinity of the Zero Dispersion Point in a Gas-Filled Hollow-Core Photonic Crystal Fiber.

    PubMed

    Bauerschmidt, S T; Novoa, D; Russell, P St J

    2015-12-11

    In 1964 Bloembergen and Shen predicted that Raman gain could be suppressed if the rates of phonon creation and annihilation (by inelastic scattering) exactly balance. This is only possible if the momentum required for each process is identical, i.e., phonon coherence waves created by pump-to-Stokes scattering are identical to those annihilated in pump-to-anti-Stokes scattering. In bulk gas cells, this can only be achieved over limited interaction lengths at an oblique angle to the pump axis. Here we report a simple system that provides dramatic Raman gain suppression over long collinear path lengths in hydrogen. It consists of a gas-filled hollow-core photonic crystal fiber whose zero dispersion point is pressure adjusted to lie close to the pump laser wavelength. At a certain precise pressure, stimulated generation of Stokes light in the fundamental mode is completely suppressed, allowing other much weaker phenomena such as spontaneous Raman scattering to be explored at high pump powers. PMID:26705636

  12. High-performance transmission in analog photonic links

    NASA Astrophysics Data System (ADS)

    Chen, Zhiyu; Yan, Lianshan; Jiang, Hengyun; Ye, Jia; Pan, Wei; Luo, Bin; Zou, Xihua

    2013-12-01

    Analog photonic link (APL) has been considered to be a promising technique due to the low insertion loss, broad bandwidth and immunity to electromagnetic interference. It is essential for many microwave systems, such as avionics, modern electronic warfare, and wireless communication systems. However, polarization effect, chromatic dispersion (CD), fiber Kerr effect and RF nonlinearity are four main problems in APL. All of them degrade the performance of the link. Therefore, APL needs to be optimized according to the different requirements in various applications. In this paper, we firstly establish a propagation model and provide the general expressions for the analog signal in photonic link based on coupled-mode theory and the small-signal analysis. Such model can describe the interaction of polarization effect, CD and nonlinearity. We also investigate the noise figure (NF) and spurious-free dynamic range (SFDR) in dispersive nonlinear link based on the proposed model. Subsequently, we review and introduce different compensation schemes for these impairments, such as CD compensation based on double sideband (DSB) modulation, and simultaneous compensation for CD and nonlinearity by employing a phase modulator (PM). After compensations, the SFDR of the link can be improved greatly. In addition, recent experimental results show that APL might be a supporting technique for the 4G or higher speed optical-wireless communication systems in near future.

  13. CAN AN ENERGY-COMPENSATED SOLID-STATE X-RAY DETECTOR BE USED FOR RADIATION PROTECTION APPLICATIONS AT HIGHER PHOTON ENERGIES?

    PubMed

    Ören, Ünal; Herrnsdorf, Lars; Gunnarsson, Mikael; Mattsson, Sören; Rääf, Christopher L

    2016-06-01

    The objective of this study was to investigate the characteristics of a solid-state detector commonly available at hospitals for parallel use as a real-time personal radiation monitor following radiation emergency situations. A solid-state detector probe with an inherent filtration (R100, RTI Electronics AB, Mölndal, Sweden) was chosen for evaluation. The energy dependence and the linearity in signal response with kerma in air were examined, and the detector was exposed to both X-ray beams using a conventional X-ray unit with effective photon energies ranging between 28.5 and 48.9 keV and to gamma rays 1.17 and 1.33 MeV from (60)Co. The R100 exhibited ∼1.7 times over-response at the lowest X-ray energy relative to the (60)Co source. The detector demonstrated a linear response (R(2) = 1) when irradiated with (60)Co to air kerma values in the range of 20-200 mGy. The conclusion is that high-energy photons such as those from (60)Co can be detected by the R100 with an energy response within a factor of <2 over the energy range examined and that the detector can provide real-time dose measurements following nuclear or radiological events. PMID:26622043

  14. Idler-free microwave photonic mixer integrated with a widely tunable and highly selective microwave photonic filter.

    PubMed

    Zou, Dan; Zheng, Xiaoping; Li, Shangyuan; Zhang, Hanyi; Zhou, Bingkun

    2014-07-01

    A novel structure consisting of an idler-free microwave photonic mixer integrated with a widely tunable and highly selective microwave photonic filter is presented, which is comprised of a spectrum-sliced broadband optical source, a dual-parallel Mach-Zehnder modulator (DPMZM), and a spatial light amplitude and phase processor (SLAPP). By adjusting the optical phase shift in the DPMZM, the dispersion-induced mixing power fading can be eliminated. By applying a phase processor with the SLAPP, the distortion of the mixing filter brought upon by third-order dispersion is also compensated. Experiments are performed and show that the up/down-conversion signal has a clean spectrum and the mixing filter can be tuned from 12 to 20 GHz without any change to the passband shape. The out-of-band suppression ratio of the mixing filter is more than 40 dB, and the 3 dB bandwidth is 140 MHz. PMID:24978780

  15. Fast wavelength-swept dispersion-tuned fiber laser over 500kHz using a wideband chirped fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Yamashita, Shinji; Takubo, Yuya

    2011-05-01

    We proposed a wide and fast wavelength-swept fiber lasers based on the dispersion tuning for the optical coherence tomography (OCT) applications. So far, we have achieved the sweep rate of ~200kHz at the sweep bandwidth of ~180nm. The sweep rate is only limited by the photon lifetime, which is proportional to the cavity length. Since we used a dispersion compensating fiber (DCF) as the dispersive medium, the long cavity length (~100m) was the limit of the sweep rate. In this paper, we demonstrate faster sweep rate up to ~500kHz by using a wideband chirped fiber Bragg grating (CFBG).

  16. Visualization of high-order dispersion for compression of few-cycle pulses

    NASA Astrophysics Data System (ADS)

    Zheng, Jiaan; Kobayashi, Wataru; Hamann, Thomas; Nürenberg, Daniel; Lührmann, Markus; L'huillier, Johannes A.; Wallenstein, Richard; Zacharias, Helmut

    2014-09-01

    We present a visually intuitive method for higher-order dispersion compensation based on multi-photon interpulse interference pulse scans. The dispersion values obtained from these scans are fed back as a correction to an acousto-optical programmable dispersive filter to compensate residual higher-order dispersions up to fifth order. This method is applied to the dispersion management of a non-collinear optical parametric chirped-pulse amplifier. A grism-pair stretcher is designed based on a global dispersion balance which provides a large stretching factor and supports a spectral bandwidth of up to 320 nm. It is implemented in a two-stage three-pass non-collinear optical parametric chirped-pulse amplifier and stretches 6-fs seed pulses to about 80 ps from 700 to 1,000 nm. The amplified pulses are compressed by material dispersion. Pulses of less than 10-fs duration with a pulse energy of 125 μJ are obtained at 20-kHz repetition rate.

  17. Photonic crystal and photonic wire device structures

    NASA Astrophysics Data System (ADS)

    De La Rue, Richard; Sorel, Marc; Johnson, Nigel; Rahman, Faiz; Ironside, Charles; Cronin, Lee; Watson, Ian; Martin, Robert; Jin, Chongjun; Pottier, Pierre; Chong, Harold; Gnan, Marco; Jugessur, Aju; Camargo, Edilson; Erwin, Grant; Md Zain, Ahmad; Ntakis, Iraklis; Hobbs, Lois; Zhang, Hua; Armenise, Mario; Ciminelli, Caterina; Coquillat, Dominique

    2005-09-01

    Photonic devices that exploit photonic crystal (PhC) principles in a planar environment continue to provide a fertile field of research. 2D PhC based channel waveguides can provide both strong confinement and controlled dispersion behaviour. In conjunction with, for instance, various electro-optic, thermo-optic and other effects, a range of device functionality is accessible in very compact PhC channel-guide devices that offer the potential for high-density integration. Low enough propagation losses are now being obtained with photonic crystal channel-guide structures that their use in real applications has become plausible. Photonic wires (PhWs) can also provide strong confinement and low propagation losses. Bragg-gratings imposed on photonic wires can provide dispersion and frequency selection in device structures that are intrinsically simpler than 2D PhC channel guides--and can compete with them under realistic conditions.

  18. Radially varying dispersion in high-numerical-aperture focusing

    NASA Astrophysics Data System (ADS)

    Mueller, Michiel; Brakenhoff, G. J.; Simon, Ulrich; Squier, Jeffrey A.

    1998-05-01

    Over the last few years a number of microscopical techniques have been developed that take advantage of ultrashort optical pulses. All these techniques rely on temporal pulse integrity at the focal point of a high-numerical aperture (NA) focusing system. We have investigated the dispersion induced broadening for pulses on the optical axis, using the two-photon absorption autocorrelation (TPAA) technique. We demonstrate that the induced broadening can be pre- compensated for by a properly designed dispersion pre- compensation unit for pulses as short as 15 femtosecond. Another source of pulse broadening in high-NA focusing systems is due to radial variations in the dispersion over the pupil of the objective. This may cause differences in the group delay between on-axis and outer ray wave packets, as well as differences in the broadening of the wave packets themselves. In this paper we present experimental results on the measurement of these radial variations in the dispersion characteristics over the aperture of high-NA microscope objectives, using a slightly modified TPAA technique.

  19. Polarization-maintaining fiber pulse compressor by birefringent hollow-core photonic bandgap fiber.

    PubMed

    Shirakawa, Akira; Tanisho, Motoyuki; Ueda, Ken-Ichi

    2006-12-11

    Structural birefringent properties of a hollow-core photonic-bandgap fiber were carefully investigated and applied to all-fiber chirped-pulse amplification as a compressor. The group birefringence of as high as 6.9x10(-4) and the dispersion splitting by as large as 149 ps/nm/km between the two principal polarization modes were observed at 1557 nm. By launching the amplifier output to one of the polarization modes a 17-dB polarization extinction ratio was obtained without any pulse degradation originating from polarization-mode dispersion. A hybrid fiber stretcher effectively compensates the peculiar dispersion of the photonic-bandgap fiber and pedestal-free 440-fs pulses with a 1-W average power and 21-nJ pulse energy were obtained. Polarization-maintaining fiber-pigtail output of high-power femtosecond pulses is useful for various applications. PMID:19529631

  20. Octave-spanning spectral phase control for single-cycle bi-photons

    NASA Astrophysics Data System (ADS)

    Shaked, Yaakov; Yefet, Shai; Geller, Tzahi; Pe'er, Avi

    2015-07-01

    The quantum correlation of octave-spanning time-energy entangled bi-photons can be as short as a single optical cycle. Many experiments designed to explore and exploit this correlation require a uniform spectral phase (transform-limited) with very low loss. So far, transform-limited single-cycle bi-photons have not been demonstrated, primarily due to the lack of precise, broadband control of their spectral phase. Here, we demonstrate the correction of the spectral-phase of near-octave spanning bi-photons to \\varphi \\lt π /20 over an octave in frequency ≈ 1330-2600 nm). Using a prism-pair with an effectively negative separation for shaping the bi-photons’ spectral phase, we obtain a tuned, very low-loss compensation of both the second and fourth dispersion orders. An essential requisite for precise tuning over such a broad bandwidth is a measure of the spectral phase that provides feedback for the tuning even when the overall dispersion is far from compensated. This is achieved by a non-classical bi-photon interference, which enables direct verification of the corrected bi-photon spectral phase.

  1. Design of a circular photonic crystal fiber with flattened chromatic dispersion using a defected core and selectively reduced air holes: Application to supercontinuum generation at 1.55 μm

    NASA Astrophysics Data System (ADS)

    Medjouri, Abdelkader; Simohamed, Lotfy Mokhtar; Ziane, Omar; Boudrioua, Azzedine; Becer, Zoubir

    2015-08-01

    In this paper, we present and numerically investigate a new and simple design of Circular Lattice Photonic Crystal Fiber (CL-PCF) with near zero ultra-flattened chromatic dispersion. The near zero dispersion is obtained by introducing a defect into the solid core and the dispersion flatness is achieved by appropriately reducing the diameter of the core-neighboring air holes ring. Simulations are performed by using the finite-difference frequency-domain (FDFD) method combined with the perfectly matched layer (PML) boundary condition. Results show that an ultra-flattened chromatic dispersion as small as ±0.66 ps/nm km is obtained over a broad band of 400 nm with high nonlinearity and ultra-low confinement loss. Furthermore, the supercontinuum (SC) generation over a short length of the proposed CL-PCF is numerically investigated. Results indicate that flat SC spectrum with a Full Width at Half Maximum (FWHM) of 600 nm is achieved with 25 cm of fiber length.

  2. Frequency-bin entangled comb of photon pairs from a Silicon-on-Insulator micro-resonator.

    PubMed

    Chen, Jun; Levine, Zachary H; Fan, Jingyun; Migdall, Alan L

    2011-01-17

    We present a quantum-mechanical theory to describe narrowband photon-pair generation via four-wave mixing in a Silicon-on-Insulator (SOI) micro-resonator. We also provide design principles for efficient photon-pair generation in an SOI micro-resonator through extensive numerical simulations. Microring cavities are shown to have a much wider dispersion-compensated frequency range than straight cavities. A microring with an inner radius of 8 μm can output an entangled photon comb of 21 pairwise-correlated peaks (42 comb lines) spanning from 1.3 μm to 1.8 μm. Such on-chip quantum photonic devices offer a path toward future integrated quantum photonics and quantum integrated circuits. PMID:21263689

  3. Two-photon spectroscopy of excitons with entangled photons

    SciTech Connect

    Schlawin, Frank; Mukamel, Shaul

    2013-12-28

    The utility of quantum light as a spectroscopic tool is demonstrated for frequency-dispersed pump-probe, integrated pump-probe, and two-photon fluorescence signals which show Ramsey fringes. Simulations of the frequency-dispersed transmission of a broadband pulse of entangled photons interacting with a three-level model of matter reveal how the non-classical time-bandwidth properties of entangled photons can be used to disentangle congested spectra, and reveal otherwise unresolved features. Quantum light effects are most pronounced at weak intensities when entangled photon pairs are well separated, and are gradually diminished at higher intensities when different photon pairs overlap.

  4. X-Chromosome dosage compensation.

    PubMed

    Meyer, Barbara J

    2005-01-01

    In mammals, flies, and worms, sex is determined by distinctive regulatory mechanisms that cause males (XO or XY) and females (XX) to differ in their dose of X chromosomes. In each species, an essential X chromosome-wide process called dosage compensation ensures that somatic cells of either sex express equal levels of X-linked gene products. The strategies used to achieve dosage compensation are diverse, but in all cases, specialized complexes are targeted specifically to the X chromosome(s) of only one sex to regulate transcript levels. In C. elegans, this sex-specific targeting of the dosage compensation complex (DCC) is controlled by the same developmental signal that establishes sex, the ratio of X chromosomes to sets of autosomes (X:A signal). Molecular components of this chromosome counting process have been defined. Following a common step of regulation, sex determination and dosage compensation are controlled by distinct genetic pathways. C. elegans dosage compensation is implemented by a protein complex that binds both X chromosomes of hermaphrodites to reduce transcript levels by one-half. The dosage compensation complex resembles the conserved 13S condensin complex required for both mitotic and meiotic chromosome resolution and condensation, implying the recruitment of ancient proteins to the new task of regulating gene expression. Within each C. elegans somatic cell, one of the DCC components also participates in the separate mitotic/meiotic condensin complex. Other DCC components play pivotal roles in regulating the number and distribution of crossovers during meiosis. The strategy by which C. elegans X chromosomes attract the condensin-like DCC is known. Small, well-dispersed X-recognition elements act as entry sites to recruit the dosage compensation complex and to nucleate spreading of the complex to X regions that lack recruitment sites. In this manner, a repressed chromatin state is spread in cis over short or long distances, thus establishing the

  5. Pulse compression to 14 fs by third-order dispersion control in a hybrid grating-prism compressor.

    PubMed

    Zeytunyan, Aram; Yesayan, Garegin; Mouradian, Levon

    2013-11-10

    A pulse compressor consisting of a fiber and a compact hybrid grating-prism dispersive delay line (DDL) is used to compress readily-available 140-fs pulses from a Ti:sapphire laser. We generate broadband pulses of up to 75 THz FWHM bandwidth in normally-dispersive single-mode conventional and photonic crystal fibers, with a potential of compression to 6 fs. Pulse dechirping in our hybrid DDL through second- and third-order dispersion (TOD) compensation results in 10× compression to 14 fs, limited by the bandwidth of the DDL transfer function and higher-order dispersion. The large tunability of the TOD of the hybrid DDL is shown. PMID:24216734

  6. Reactive power compensating system

    DOEpatents

    Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

    1987-01-01

    The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

  7. Solitonization of a dispersive wave.

    PubMed

    Braud, F; Conforti, M; Cassez, A; Mussot, A; Kudlinski, A

    2016-04-01

    We report the observation of a nonlinear propagation scenario in which a dispersive wave is transformed into a fundamental soliton in an axially varying optical fiber. The dispersive wave is initially emitted in the normal dispersion region and the fiber properties change longitudinally so that the dispersion becomes anomalous at the dispersive wave wavelength, which allows it to be transformed into a soliton. The solitonic nature of the field is demonstrated by solving the direct Zakharov-Shabat scattering problem. Experimental characterization performed in spectral and temporal domains show evidence of the solitonization process in an axially varying photonic crystal fiber. PMID:27192249

  8. Function photonic crystals

    NASA Astrophysics Data System (ADS)

    Wu, Xiang-Yao; Zhang, Bai-Jun; Yang, Jing-Hai; Liu, Xiao-Jing; Ba, Nuo; Wu, Yi-Heng; Wang, Qing-Cai

    2011-07-01

    In this paper, we present a new kind of function photonic crystals (PCs), whose refractive index is a function of space position. Conventional PCs structure grows from two materials, A and B, with different dielectric constants εA and εB. Based on Fermat principle, we give the motion equations of light in one-dimensional, two-dimensional and three-dimensional function photonic crystals. For one-dimensional function photonic crystals, we give the dispersion relation, band gap structure and transmissivity, and compare them with conventional photonic crystals, and we find the following: (1) For the vertical and non-vertical incidence light of function photonic crystals, there are band gap structures, and for only the vertical incidence light, the conventional PCs have band gap structures. (2) By choosing various refractive index distribution functions n( z), we can obtain more wider or more narrower band gap structure than conventional photonic crystals.

  9. Dispersionless gaps and cavity modes in photonic crystals containing hyperbolic metamaterials

    NASA Astrophysics Data System (ADS)

    Xue, Chun-hua; Ding, Yaqiong; Jiang, Hai-tao; Li, Yunhui; Wang, Zhan-shan; Zhang, Ye-wen; Chen, Hong

    2016-03-01

    We theoretically study dispersionless gaps and cavity modes in one-dimensional photonic crystals composed of hyperbolic metamaterials and dielectric. Bragg gaps in conventional all-dielectric photonic crystals are always dispersive because propagating phases in two kinds of dielectrics decrease with incident angle. Here, based on phase variation compensation between a hyperbolic metamaterial layer and an isotropic dielectric layer, the dispersion of the gap can be offset and thus a dispersionless gap can be realized. Moreover, the dispersionless property of such gap has a wide parameter space. The dispersionless gap can be used to realize a dispersionless cavity mode. The dispersionless gaps and cavity modes will possess significant applications for all-angle reflectors, high-Q filters excited with finite-sized sources, and nonlinear wave mixing processes.

  10. Optical tracking telescope compensation

    NASA Technical Reports Server (NTRS)

    Gilbart, J. W.

    1973-01-01

    In order to minimize the effects of parameter variations in the dynamics of an optical tracking telescope, a model referenced parameter adaptive control system is described that - in conjunction with more traditional forms of compensation - achieves a reduction of rms pointing error by more than a factor of six. The adaptive compensation system utilizes open loop compensation, closed loop compensation, and model reference compensation to provide the precise input to force telescope axis velocity to follow the ideal velocity.

  11. X-ray Photon Counting Using 100 MHz Ready-Made Silicon P-Intrinsic-N X-ray Diode and Its Application to Energy-Dispersive Computed Tomography

    NASA Astrophysics Data System (ADS)

    Kodama, Hajime; Watanabe, Manabu; Sato, Eiichi; Oda, Yasuyuki; Hagiwara, Osahiko; Matsukiyo, Hiroshi; Osawa, Akihiro; Enomoto, Toshiyuki; Kusachi, Shinya; Sato, Shigehiro; Ogawa, Akira

    2013-07-01

    X-ray photons are directly detected using a 100 MHz ready-made silicon P-intrinsic-N X-ray diode (Si-PIN-XD). The Si-PIN-XD is shielded using an aluminum case with a 25-µm-thick aluminum window and a BNC connector. The photocurrent from the Si-PIN-XD is amplified by charge sensitive and shaping amplifiers, and the event pulses are sent to a multichannel analyzer (MCA) to measure X-ray spectra. At a tube voltage of 90 kV, we observe K-series characteristic X-rays of tungsten. Photon-counting computed tomography (PC-CT) is accomplished by repeated linear scans and rotations of an object, and projection curves of the object are obtained by linear scanning at a tube current of 2.0 mA. The exposure time for obtaining a tomogram is 10 min with scan steps of 0.5 mm and rotation steps of 1.0°. At a tube voltage of 90 kV, the maximum count rate is 150 kcps. We carry out PC-CT using gadolinium media and confirm the energy-dispersive effect with changes in the lower level voltage of the event pulse using a comparator.

  12. Optimization of pump spectra for gain-flattened photonic crystal fiber Raman amplifiers operating in C-band.

    PubMed

    Sasaki, Kazuya; Varshney, Shailendra K; Wada, Keisuke; Saitoh, Kunimasa; Koshiba, Masanori

    2007-03-01

    This paper focuses on the optimization of pump spectra to achieve low Raman gain ripples over C-band in ultra-low loss photonic crystal fiber (PCF) and dispersion compensating PCFs (DCPCFs). Genetic algorithm (GA), a multivariate stochastic optimization algorithm, is applied to optimize the pump powers and the wavelengths for the aforesaid fiber designs. In addition, the GA integrated with full-vectorial finite element method with curvilinear edge/nodal elements is used to optimize the structural parameters of DCPCF. The optimized DCPCF provides broadband dispersion compensation over C-band with low negative dispersion coefficient of -530 ps/nm/km at 1550 nm, which is five times larger than the conventional dispersion compensating fibers with nearly equal effective mode area (21.7 mum(2)). A peak gain of 8.4 dB with +/-0.21 dB gain ripple is achieved for a 2.73 km long DCPCF module when three optimized pumps are used in the backward direction. The lowest gain ripple of +/-0.36 dB is attained for a 10 km long ultra-low loss PCF with three backward pumps. Sensitivity analysis has been performed and it is found that within the experimental fabrication tolerances of +/-2%, the absolute magnitude of dispersion may vary by +/-16%, while the Raman gain may change by +/-7%. Through tolerance study, it is examined that the ring core's hole-size is more sensitive to the structural deformations. PMID:19532502

  13. Photon-photon collisions

    SciTech Connect

    Burke, D.L.

    1982-10-01

    Studies of photon-photon collisions are reviewed with particular emphasis on new results reported to this conference. These include results on light meson spectroscopy and deep inelastic e..gamma.. scattering. Considerable work has now been accumulated on resonance production by ..gamma gamma.. collisions. Preliminary high statistics studies of the photon structure function F/sub 2//sup ..gamma../(x,Q/sup 2/) are given and comments are made on the problems that remain to be solved.

  14. Compensation Review Analyst

    Energy Science and Technology Software Center (ESTSC)

    2003-06-03

    COMPERA is a decision support system designed to facilitate the compensation review process. With parameters provided by the user(s), the system generates recommendations for base increases and nonbase compensation that strives to align total compensation with performance compensation targets. The user(s) prescribe(s) compensation targets according to performance (or value of contribution) designators. These targets are presented in look-up tables, which are then used by embedded formulas in the worksheet to determine the recommended compensation formore » each individual.« less

  15. Experiments on a compact and robust polarization-entangled photon source

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-Wei; Zhang, Tong-Yi; Yao, Yin-Ping; Wan, Ren-Gang; Zou, Sheng-Wu

    2012-02-01

    We construct a compact polarization-entangled photon source using type-II degenerate spontaneous parametric down-conversion (SPDC) in beta-barium borate (BBO) crystal pumped by a 405 nm violet laser diode. In order to compensate the spatial displacement and the temporal delay due to the birefringence and dispersion effect of signal and idler photons, we make the down-converted photon pairs pass through a half wave plate and an additional BBO crystal with the half thickness of the original one. This improves the visibility of two-photon interference by eliminating the distinguishability of the paired photons. We measure the polarization correlations by two adjustable polarization analyzers in two conjugate bases, H/V and +45°/-45°, respectively. The polarization analyzer consists of a polarization beam splitter cube preceded by a rotatable half wave plate. When rotating one of the half wave plates and keeping the other one at fixed angle, we obtain the expected sin2 dependence of the coincidence counts. The highly visible sinusoidal coincidence indicates the violation of the Bell inequality and demonstrates the high quality of the polarization-entangled photon source. This compact polarization-entangled photon source is easily configurable and robust to demonstrate optical quantum information processing.

  16. Oil dispersants

    SciTech Connect

    Flaherty, L.M.

    1989-01-01

    This book contains papers presented at a symposium of the American Society for Testing and Materials. The topics covered include: The effect of elastomers on the efficiency of oil spill dispersants; planning for dispersant use; field experience with dispersants for oil spills on land; and measurements on natural dispersion.

  17. Photon-photon collisions

    SciTech Connect

    Brodsky, S.J.

    1988-07-01

    Highlights of the VIIIth International Workshop on Photon-Photon Collisions are reviewed. New experimental and theoretical results were reported in virtually every area of ..gamma gamma.. physics, particularly in exotic resonance production and tests of quantum chromodynamics where asymptotic freedom and factorization theorems provide predictions for both inclusive and exclusive ..gamma gamma.. reactions at high momentum transfer. 73 refs., 12 figs.

  18. PMD tolerant nonlinear compensation using in-line phase conjugation.

    PubMed

    McCarthy, M E; Al Kahteeb, M A Z; Ferreira, F M; Ellis, A D

    2016-02-22

    In this paper, we numerically investigate the impact of polarisation mode dispersion on the efficiency of compensation of nonlinear transmission penalties for systems employing one of more inline phase conjugation devices. We will show that reducing the spacing between phase conjugations allows for significantly improved performance in the presence polarisation mode dispersion or a significant relaxation in the acceptable level of polarization mode dispersion. We show that these results are consistent with previously presented full statistical analysis of nonlinear transmission appropriately adjusted for the reduced section length undergoing compensation. PMID:26906997

  19. Robust springback compensation

    NASA Astrophysics Data System (ADS)

    Carleer, Bart; Grimm, Peter

    2013-12-01

    Springback simulation and springback compensation are more and more applied in productive use of die engineering. In order to successfully compensate a tool accurate springback results are needed as well as an effective compensation approach. In this paper a methodology has been introduce in order to effectively compensate tools. First step is the full process simulation meaning that not only the drawing operation will be simulated but also all secondary operations like trimming and flanging. Second will be the verification whether the process is robust meaning that it obtains repeatable results. In order to effectively compensate a minimum clamping concept will be defined. Once these preconditions are fulfilled the tools can be compensated effectively.

  20. Toxic compensation bills.

    PubMed Central

    Anderson, R C

    1985-01-01

    Congress has demonstrated interest in toxic compensation legislation, but not enough agreement to make significant progress. Advocates of reform claim that the legal system is heavily weighed against victims who seek compensation through the courts. Proposed reforms include a compensation fund and a cause of action in federal court. Critics have questioned whether these changes in the law would represent an improvement. Existing income replacement, medical cost reimbursement, and survivor insurance programs largely cover the losses of individuals with chronic disease. Thus, the need for an additional compensation is not clear. Furthermore, experience with compensation funds such as the Black Lung Fund suggests that political rather than scientific criteria may be used to determine eligibility. Finally, under the proposed financing mechanisms the compensation funds that are being debated would not increase incentives for care in the handling of hazardous wastes or toxic substances. PMID:4085440

  1. Photon-photon collisions

    SciTech Connect

    Brodsky, S.J.

    1985-01-01

    The study of photon-photon collisions has progressed enormously, stimulated by new data and new calculational tools for QCD. In the future we can expect precise determinations of ..cap alpha../sub s/ and ..lambda../sup ms/ from the ..gamma..*..gamma.. ..-->.. ..pi../sup 0/ form factor and the photon structure function, as well as detailed checks of QCD, determination of the shape of the hadron distribution amplitudes from ..gamma gamma.. ..-->.. H anti H, reconstruction of sigma/sub ..gamma gamma../ from exclusive channels at low W/sub ..gamma gamma../, definitive studies of high p/sub T/ hadron and jet production, and studies of threshold production of charmed systems. Photon-photon collisions, along with radiative decays of the psi and UPSILON, are ideal for the study of multiquark and gluonic resonances. We have emphasized the potential for resonance formation near threshold in virtually every hadronic exclusive channel, including heavy quark states c anti c c anti c, c anti c u anti u, etc. At higher energies SLC, LEP, ...) parity-violating electroweak effects and Higgs production due to equivalent Z/sup 0/ and W/sup + -/ beams from e ..-->.. eZ/sup 0/ and e ..-->.. nu W will become important. 44 references.

  2. Photonic crystal surface-emitting lasers

    SciTech Connect

    Chua, Song Liang; Lu, Ling; Soljacic, Marin

    2015-06-23

    A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

  3. Accuracy of numerically produced compensators.

    PubMed

    Thompson, H; Evans, M D; Fallone, B G

    1999-01-01

    A feasibility study is performed to assess the utility of a computer numerically controlled (CNC) mill to produce compensating filters for conventional clinical use and for the delivery of intensity-modulated beams. A computer aided machining (CAM) software is used to assist in the design and construction of such filters. Geometric measurements of stepped and wedged surfaces are made to examine the accuracy of surface milling. Molds are milled and filled with molten alloy to produce filters, and both the molds and filters are examined for consistency and accuracy. Results show that the deviation of the filter surfaces from design does not exceed 1.5%. The effective attenuation coefficient is measured for CadFree, a cadmium-free alloy, in a 6 MV photon beam. The effective attenuation coefficients at the depth of maximum dose (1.5 cm) and at 10 cm in solid water phantom are found to be 0.546 cm-1 and 0.522 cm-1, respectively. Further attenuation measurements are made with Cerrobend to assess the variations of the effective attenuation coefficient with field size and source-surface distance. The ability of the CNC mill to accurately produce surfaces is verified with dose profile measurements in a 6 MV photon beam. The test phantom is composed of a 10 degrees polystyrene wedge and a 30 degrees polystyrene wedge, presenting both a sharp discontinuity and sloped surfaces. Dose profiles, measured at the depth of compensation (10 cm) beneath the test phantom and beneath a flat phantom, are compared to those produced by a commercial treatment planning system. Agreement between measured and predicted profiles is within 2%, indicating the viability of the system for filter production. PMID:10100166

  4. Gmti Motion Compensation

    DOEpatents

    Doerry, Armin W.

    2004-07-20

    Movement of a GMTI radar during a coherent processing interval over which a set of radar pulses are processed may cause defocusing of a range-Doppler map in the video signal. This problem may be compensated by varying waveform or sampling parameters of each pulse to compensate for distortions caused by variations in viewing angles from the radar to the target.

  5. High-resolution fiber Bragg grating based transverse load sensor using microwave photonics filtering technique.

    PubMed

    Wang, Yiping; Wang, Ming; Xia, Wei; Ni, Xiaoqi

    2016-08-01

    In this paper, a new fiber Bragg grating (FBG) sensor exploiting microwave photonics filter technique for transverse load sensing is firstly proposed and experimentally demonstrated. A two-tap incoherent notch microwave photonics filter (MPF) based on a transverse loaded FBG, a polarization beam splitter (PBS), a tunable delay line (TDL) and a length of dispersion compensating fiber (DCF) is demonstrated. The frequency response of the filter with respect to the transverse load is studied. By detecting the resonance frequency shifts of the notch MPF, the transverse load can be determined. The theoretical and experimental results show that the proposed FBG sensor has a higher resolution than traditional methods based on optical spectrum analysis. The sensitivity of the sensor is measured to be as high as 2.5 MHz/N for a sensing fiber with a length of 18mm. Moreover, the sensitivity can be easily adjusted. PMID:27505763

  6. Ocular dispersion

    NASA Astrophysics Data System (ADS)

    Hammer, Daniel X.; Noojin, Gary D.; Thomas, Robert J.; Stolarski, David J.; Rockwell, Benjamin A.; Welch, Ashley J.

    1999-06-01

    Spectrally resolved white-light interferometry (SRWLI) was used to measure the wavelength dependence of refractive index (i.e., dispersion) for various ocular components. The accuracy of the technique was assessed by measurement of fused silica and water, the refractive indices of which have been measured at several different wavelengths. The dispersion of bovine and rabbit aqueous and vitreous humor was measured from 400 to 1100 nm. Also, the dispersion was measured from 400 to 700 nm for aqueous and vitreous humor extracted from goat and rhesus monkey eyes. For the humors, the dispersion did not deviate significantly from water. In an additional experiment, the dispersion of aqueous and vitreous humor that had aged up to a month was compared to freshly harvested material. No difference was found between the fresh and aged media. An unsuccessful attempt was also made to use the technique for dispersion measurement of bovine cornea and lens. Future refinement may allow measurement of the dispersion of cornea and lens across the entire visible and near-infrared wavelength band. The principles of white- light interferometry including image analysis, measurement accuracy, and limitations of the technique, are discussed. In addition, alternate techniques and previous measurements of ocular dispersion are reviewed.

  7. Turbulence compensation: an overview

    NASA Astrophysics Data System (ADS)

    van Eekeren, Adam W. M.; Schutte, Klamer; Dijk, Judith; Schwering, Piet B. W.; van Iersel, Miranda; Doelman, Niek J.

    2012-06-01

    In general, long range visual detection, recognition and identification are hampered by turbulence caused by atmospheric conditions. Much research has been devoted to the field of turbulence compensation. One of the main advantages of turbulence compensation is that it enables visual identification over larger distances. In many (military) scenarios this is of crucial importance. In this paper we give an overview of several software and hardware approaches to compensate for the visual artifacts caused by turbulence. These approaches are very diverse and range from the use of dedicated hardware, such as adaptive optics, to the use of software methods, such as deconvolution and lucky imaging. For each approach the pros and cons are given and it is indicated for which scenario this approach is useful. In more detail we describe the turbulence compensation methods TNO has developed in the last years and place them in the context of the different turbulence compensation approaches and TNO's turbulence compensation roadmap. Furthermore we look forward and indicate the upcoming challenges in the field of turbulence compensation.

  8. Reactive Power Compensator.

    DOEpatents

    El-Sharkawi, M.A.; Venkata, S.S.; Chen, M.; Andexler, G.; Huang, T.

    1992-07-28

    A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation. 26 figs.

  9. Reactive power compensator

    DOEpatents

    El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.; Chen, Mingliang; Andexler, George; Huang, Tony

    1992-01-01

    A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line. The switch driver develops triggering signals that are supplied to a plurality of series-connected solid state switches (350), which control charge current in one direction in respect to ground for each compensation capacitor. During each cycle, current flows from ground to charge the capacitors as the voltage on the line begins to go negative from its positive peak value. The triggering signals are applied to gate the solid state switches into a conducting state when the potential on the lines and on the capacitors reaches a negative peak value, thereby minimizing both the potential difference and across the charge current through the switches when they begin to conduct. Any harmonic distortion on the potential and current carried by the lines is filtered out from the current and potential signals used by the reactive power compensator so that it does not affect the determination of the required reactive compensation.

  10. Studies of the modal properties of circularly photonic crystal fiber (C-PCF) for high power applications

    NASA Astrophysics Data System (ADS)

    Maji, Partha Sona; Roy Chaudhuri, Partha

    2016-04-01

    The guiding properties of a new type of photonic crystal fibers where air-holes are arranged in a circular pattern (C-PCF) with a silica matrix have been investigated. The dispersion properties of the fiber with different spacing of circle and air-hole diameter have been studied in detail. It is shown that C-PCFs with smaller values of radius and higher air-filling fraction can be used as dispersion compensating fiber. A comparison between fibers with circular and triangular lattice has also been performed, taking into account the dispersion properties and the effective area in the wavelength range between 1200 nm and 1600 nm. C-PCF can better compensate the inline dispersion for both single wavelength and broadband wavelength applications which is a unique property not observed by regular triangular-lattice or square-lattice PCFs. The fiber provides higher effective area, making it a better candidate for high power accumulations in the core of the fiber. The fiber also shows red-shifting of the first zero dispersion wavelength (ZDW), flatter dispersion slope and lower Group Velocity Dispersion (GVD) in the normal dispersion region thereby making it a better candidate for high power nonlinear applications like super-continuum generation, soliton pulse propagation etc. With the above advantages, we have considered a series study of these circular-lattice structures for various geometrical parameters and temporal pulses in order to explore the characteristics of broadband supercontinuum generation. This design study for high power supercontinuum generation will be very helpful for potential application of new sources in various fields like astronomy, climatology, spectroscopy optical tomography and sensing etc. to name a few.

  11. Phase tracking with differential dispersion

    NASA Astrophysics Data System (ADS)

    Haubois, Xavier; Lacour, Sylvestre; Perrin, Guy S.; Dembet, Roderick; Fedou, Pierre; Eisenhauer, Frank; Rousselet-Perraut, Karine; Straubmeier, Christian; Amorim, Antonio; Brandner, Wolfgang

    2014-07-01

    Differential chromatic dispersion in single-mode optical fibres leads to a loss of contrast of the white light fringe. For the GRAVITY instrument, this aspect is critical since it limits the fringe tracking performance. We present a real-time algorithm that compensates for differential dispersion due to varying fibre lengths using prior calibration of the optical fibres. This correction is limited by the accuracy to which the fibres stretch is known. We show how this affects the SNR on the white light fringe for different scenarios and we estimate how this phenomenon might eventually impact the astrometric accuracy of GRAVITY observations.

  12. Chromatic compensation of broadband light diffraction: ABCD-matrix approach.

    PubMed

    Lancis, Jésus; Mínguez-Vega, Gladys; Tajahuerce, Enrique; Climent, Vicent; Andrés, Pedro; Caraquitena, José

    2004-10-01

    Compensation of chromatic dispersion for the optical implementation of mathematical transformations has proved to be an important tool in the design of new optical methods for full-color signal processing. A novel approach for designing dispersion-compensated, broadband optical transformers, both Fourier and Fresnel, based on the collimated Fresnel number is introduced. In a second stage, the above framework is fully exploited to achieve the optical implementation of the fractional Fourier transform (FRT) of any diffracting screen with broadband illumination. Moreover, we demonstrate that the amount of shift variance of the dispersion-compensated FRT can be tuned continuously from the spatial domain, which is totally space variant, to the spectral domain, which is totally space invariant, with the chromatic correction remaining unaltered. PMID:15497415

  13. The American compensation phenomenon.

    PubMed

    Bale, A

    1990-01-01

    In this article, the author defines the occupational safety and health domain, characterizes the distinct compensation phenomenon in the United States, and briefly reviews important developments in the last decade involving Karen Silkwood, intentional torts, and asbestos litigation. He examines the class conflict over the value and meaning of work-related injuries and illnesses involved in the practical activity of making claims and turning them into money through compensation inquiries. Juries, attributions of fault, and medicolegal discourse play key roles in the compensation phenomenon. This article demonstrates the extensive, probing inquiry through workers' bodies constituted by the American compensation phenomenon into the moral basis of elements of the system of production. PMID:2139638

  14. ACTS Rain Fade Compensation

    NASA Technical Reports Server (NTRS)

    Coney, Thom A.

    1996-01-01

    Performance status of the Adaptive Rain Fade Compensation includes: (1) The rain fade protocol is functional detecting fades, providing an additional 10 dB of margin and seamless transitions to and from coded operation; (2) The stabilization of the link margins and the optimization of rain fade decision thresholds has resulted in improved BER performance; (3) Characterization of the fade compensation algorithm is ongoing.

  15. Error-Compensated Telescope

    NASA Technical Reports Server (NTRS)

    Meinel, Aden B.; Meinel, Marjorie P.; Stacy, John E.

    1989-01-01

    Proposed reflecting telescope includes large, low-precision primary mirror stage and small, precise correcting mirror. Correcting mirror machined under computer control to compensate for error in primary mirror. Correcting mirror machined by diamond cutting tool. Computer analyzes interferometric measurements of primary mirror to determine shape of surface of correcting mirror needed to compensate for errors in wave front reflected from primary mirror and commands position and movement of cutting tool accordingly.

  16. Microwave photonic integrator based on a multichannel fiber Bragg grating.

    PubMed

    Zhang, Jiejun; Yao, Jianping

    2016-01-15

    We propose and experimentally demonstrate a microwave photonic integrator based on a multichannel fiber Bragg grating (FBG) working in conjunction with a dispersion compensating fiber (DCF) to provide a step group delay response with no in-channel dispersion-related distortion. The multichannel FBG is designed based on the spectral Talbot effect, which provides a large group delay dispersion (GDD) within each channel. A step group delay response can then be achieved by cascading the multichannel FBG with a DCF having a GDD opposite the in-channel GDD. An optical comb, with each comb line located at the center of each channel of the FBG, is modulated by a microwave signal to be integrated. At the output of the DCF, multiple time-delayed replicas of the optical signal, with equal time delay spacing are obtained and are detected and summed at a photodetector (PD). The entire operation is equivalent to the integration of the input microwave signal. For a multichannel FBG with an in-channel GDD of 730 ps/nm and a DCF with an opposite GDD, an integrator with a bandwidth of 2.9 GHz and an integration time of 7 ns is demonstrated. PMID:26766692

  17. Intra-channel nonlinearity compensation for PM-16 QAM traffic co-propagating with 28 Gbaud m-ary QAM neighbours.

    PubMed

    Rafique, Danish; Sygletos, Stylianos; Ellis, Andrew D

    2013-02-25

    We quantify the benefits of intra-channel nonlinear compensation in meshed optical networks, in view of network configuration, fibre design aspect, and dispersion management. We report that for a WDM optical transport network employing flexible 28Gbaud PM-mQAM transponders with no in-line dispersion compensation, intra-channel nonlinear compensation, for PM-16QAM through traffic, offers significant improvements of up to 4dB in nonlinear tolerance (Q-factor) irrespective of the co-propagating modulation format, and that this benefit is further enhanced (1.5dB) by increasing local link dispersion. For dispersion managed links, we further report that advantages of intra-channel nonlinear compensation increase with in-line dispersion compensation ratio, with 1.5dB improvements after 95% in-line dispersion compensation, compared to uncompensated transmission. PMID:23481951

  18. Workers' Compensation and Teacher Stress.

    ERIC Educational Resources Information Center

    Nisbet, Michael K.

    1999-01-01

    Examines the Workers' Compensation system and teacher stress to determine if a burned-out teacher should be eligible for Workers' Compensation benefits. Concludes that although most states do not allow Workers' Compensation benefits to burned-out teachers, compensation should be granted because the injuries are real and work-related. (Contains 48…

  19. Distortion-free spectrum sliced microwave photonic signal processor: analysis, design and implementation.

    PubMed

    Li, Liwei; Yi, Xiaoke; Huang, Thomas X H; Minasian, Robert A

    2012-05-01

    A new switchable microwave photonic filter based on a novel spectrum slicing technique is presented. The processor enables programmable multi-tap generation with general transfer function characteristics and offers tunability, reconfigurabiliy, and switchability. It is based on connecting a dispersion controlled spectrum slicing filter after the modulated bipolar broadband light source, which consequently generates multiple spectrum slices with bipolarity, and compensates dispersion induced RF degradation simultaneously within a single device. A detailed theoretical model for this microwave photonic filter design is presented. Experimental results are presented which verify the model, and demonstrate a 33 bipolar-tap microwave filter with significant reduction of passband attenuations at high frequencies. The RF response improvement of the new microwave photonic filter is investigated, for both an ideal linear group delay line and for the experimental fiber delay line that has second order group delay and the results show that this new structure is effective for RF filters with various free spectral range values and spectrum slice bandwidths. Finally, a switchable bipolar filter that has a square-top bandpass filter response with more than 30 dB stopband attenuation that can be switched on/off via software control is demonstrated. PMID:22565771

  20. Optics of globular photonic crystals

    SciTech Connect

    Gorelik, V S

    2007-05-31

    The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter {approx}200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported. (review)

  1. Energy compensated solid state gamma dosimeter

    SciTech Connect

    Sinclair, F.; Clapp, A.; Entine, G.; Kronenberg, S.

    1988-02-01

    Solid state semiconductor detectors using pulse mode detection are attractive candidates for real time dosimetry systems. Their high atomic number relative to that of tissue gives a nonlinear response as a function of the photon energy over the range from 30 keV to 10 MeV. An analytical model of a silicon PIN diode has been developed, including the photoelectric and Compton interactions as well as the ejection of the secondary electrons from the sensitive volume. The authors tested a nonlinear pulse height compensation algorithm using calibrated gamma and x-ray fluxes, and find that this approach improves the dose accuracy.

  2. Dispersion Modeling.

    ERIC Educational Resources Information Center

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  3. Photon absorptiometry

    SciTech Connect

    Velchik, M.G.

    1987-01-01

    Recently, there has been a renewed interest in the detection and treatment of osteoporosis. This paper is a review of the merits and limitations of the various noninvasive modalities currently available for the measurement of bone mineral density with special emphasis placed upon the nuclear medicine techniques of single-photon and dual-photon absorptiometry. The clinicians should come away with an understanding of the relative advantages and disadvantages of photon absorptiometry and its optimal clinical application. 49 references.

  4. Backlash compensator mechanism

    DOEpatents

    Chrislock, Jerry L.

    1979-01-01

    Mechanism which compensates for backlash error in a lead screw position indicator by decoupling the indicator shaft from the lead screw when reversing rotation. The position indicator then displays correct information regardless of the direction of rotation of the lead screw.

  5. Teacher Compensation and Organization.

    ERIC Educational Resources Information Center

    Kelley, Carolyn

    1997-01-01

    Examines changes in the conceptualization of schooling over time from an organizational perspective. Explores how compensation systems might be better designed to match alternative organizational designs, considering scientific management, effective schools, content-driven schooling, and high standards/high involvement schools as organizational…

  6. The Compensation Question

    ERIC Educational Resources Information Center

    Richwine, Jason; Biggs, Andrew; Mishel, Lawrence; Roy, Joydeep

    2012-01-01

    Over the past few years, as cash-strapped states and school districts have faced tough budget decisions, spending on teacher compensation has come under the microscope. The underlying question is whether, when you take everything into account, today's teachers are fairly paid, underpaid, or overpaid. In this forum, two pairs of respected…

  7. Reactive Power Compensating System.

    DOEpatents

    Williams, Timothy J.; El-Sharkawi, Mohamed A.; Venkata, Subrahmanyam S.

    1985-01-04

    The circuit was designed for the specific application of wind-driven induction generators. It has great potential for application in any situation where a varying reactive power load is present, such as with induction motors or generators, or for transmission network compensation.

  8. Photon Molecules in Atomic Gases Trapped Near Photonic Crystal Waveguides

    NASA Astrophysics Data System (ADS)

    Douglas, James S.; Caneva, Tommaso; Chang, Darrick E.

    2016-07-01

    Realizing systems that support robust, controlled interactions between individual photons is an exciting frontier of nonlinear optics. To this end, one approach that has emerged recently is to leverage atomic interactions to create strong and spatially nonlocal interactions between photons. In particular, effective photonic interactions have been successfully created via interactions between atoms excited to Rydberg levels. Here, we investigate an alternative approach, in which atomic interactions arise via their common coupling to photonic crystal waveguides. This technique takes advantage of the ability to separately tailor the strength and range of interactions via the dispersion engineering of the structure itself, which can lead to qualitatively new types of phenomena. For example, much of the work on photon-photon interactions relies on the linear optical effect of electromagnetically induced transparency, in combination with the use of interactions to shift optical pulses into or out of the associated transparency window. Here, we identify a large new class of "correlated transparency windows," in which photonic states of a certain number and shape selectively propagate through the system. Through this technique, we show that molecular bound states of photon pairs can be created.

  9. Absolute Bragg wavelength and dispersion determination in dispersive incoherent OFDR interrogators

    NASA Astrophysics Data System (ADS)

    Clement, J.; Torregrosa, G.; Hervás, J.; Fernández-Pousa, C. R.

    2016-05-01

    We report on an incoherent OFDR interrogator of FBG arrays based on the concept of dispersive wavelength to time delay mapping. The system is specifically designed to show stability to environmental thermal variations by the incorporation of a composite dispersive delay and weak broadband reflectors for delay and dispersion monitoring. Dispersion is imparted by the combination of a fiber coil and an athermally-packaged chirped fiber Bragg grating for dispersion compensation. Using differential measurements over a single acquisition trace, the values of Bragg wavelengths and dispersion are determined from the delays experienced by the FBGs and by additional reference wavelengths reflected in the broadband reflectors. The results show maximum deviations of 20 pm and 0.2 ps/nm with respect to OSA measurements of Bragg wavelengths and nominal dispersion values, respectively.

  10. Fog dispersion

    NASA Technical Reports Server (NTRS)

    Frost, W.; Christensen, L. S.; Collins, F. G.; Camp, D. W.

    1980-01-01

    A study of economically viable techniques for dispersing warm fog at commercial airports is presented. Five fog dispersion techniques are examined: evaporation suppression, downwash, mixing, seeding with hygroscopic material, thermal techniques, and charged particle techniques. Thermal techniques, although effective, were found to be too expensive for routine airport operations, and detrimental to the environment. Seeding or helicopter downwash are practical for small-scale or temporary fog clearing, but are probably not useful for airport operations on a routine basis. Considerable disagreement exists on the capability of charged particle techniques, which stems from the fact that different assumptions and parameter values are used in the analytical models. Recommendations resulting from the review of this technique are listed, and include: experimental measurements of the parameters in question; a study to ascertain possible safety hazards, such as increased electrical activity or fuel ignition during refueling operations which could render charged particle techniques impractical; and a study of a single charged particle generator.

  11. Self-assembled tunable photonic hyper-crystals

    NASA Astrophysics Data System (ADS)

    Smolyaninov, Igor; Smolyaninova, Vera; Yost, Bradley; Lahneman, David; Gresock, Thomas; Narimanov, Evgenii

    2015-03-01

    We demonstrate a novel artificial optical material, the photonic hyper-crystal, which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. This work was supported in part by NSF Grant DMR-1104676, NSF Center for Photonic and Multiscale Nanomaterials, ARO MURI and Gordon and Berry Moore Foundation.

  12. Photon Colliders

    SciTech Connect

    Gronberg, J

    2002-10-07

    A photon collider interaction region has the possibility of expanding the physics reach of a future TeV scale electron-positron collider. A survey of ongoing efforts to design the required lasers and optics to create a photon collider is presented in this paper.

  13. Deferred Compensation Becomes More Common

    ERIC Educational Resources Information Center

    June, Audrey Williams

    2006-01-01

    A key part of the compensation package for some college and university presidents is money that they do not receive in their paychecks. Formally known as deferred compensation, such payments can take many forms, including supplemental retirement pay, severance pay, or even bonuses. With large institutions leading the way, deferred compensation has…

  14. The Federal Employees' Compensation Act.

    ERIC Educational Resources Information Center

    Nordlund, Willis J.

    1991-01-01

    The 1916 Federal Employees' Compensation Act is still the focal point around which the federal workers compensation program works today. The program has gone through many changes on its way to becoming a modern means of compensating workers for job-related injury, disease, and death. (Author)

  15. CGI delay compensation

    NASA Technical Reports Server (NTRS)

    Mcfarland, Richard E.

    1986-01-01

    Computer-generated graphics in real-time helicopter simulation produces objectionable scene-presentation time delays. In the flight simulation laboratory at Ames Research Center, it has been determined that these delays have an adverse influence on pilot performance during aggressive tasks such as nap-of-the-earth (NOE) maneuvers. Using contemporary equipment, computer-generated image (CGI) time delays are an unavoidable consequence of the operations required for scene generation. However, providing that magnitide distortions at higher frequencies are tolerable, delay compensation is possible over a restricted frequency range. This range, assumed to have an upper limit of perhaps 10 or 15 rad/sec, conforms approximately to the bandwidth associated with helicopter handling qualities research. A compensation algorithm is introduced here and evaluated in terms of tradeoffs in frequency responses. The algorithm has a discrete basis and accommodates both a large, constant transport delay interval and a periodic delay interval, as associated with asynchronous operations.

  16. Ground difference compensating system

    DOEpatents

    Johnson, Kris W.; Akasam, Sivaprasad

    2005-10-25

    A method of ground level compensation includes measuring a voltage of at least one signal with respect to a primary ground potential and measuring, with respect to the primary ground potential, a voltage level associated with a secondary ground potential. A difference between the voltage level associated with the secondary ground potential and an expected value is calculated. The measured voltage of the at least one signal is adjusted by an amount corresponding to the calculated difference.

  17. Source-corrected two-photon excited fluorescence measurements between 700 and 880 nm

    SciTech Connect

    Fisher, W.G.; Wachter, E.A.; Lytle, F.E.; Armas, M.; Seaton, C.

    1998-04-01

    Passively mode-locked titanium:sapphire (Ti:S) lasers are capable of generating a high-frequency train of transform-limited subpico-second pulses, producing peak powers near 10{sup 5}thinspW at moderate average powers. The low energy per pulse ({lt}20 nJ) permits low fluence levels to be maintained in tightly focused beams, reducing the possibility of saturating fluorescence transitions. These properties, combined with a wavelength tunability from approximately 700 nm to 1 {mu}m, provide excellent opportunities for studying simultaneous two-photon excitation (TPE). However, pulse formation is very sensitive to a variety of intracavity parameters, including group velocity dispersion compensation, which leads to wavelength-dependent pulse profiles as the wavelength is scanned. This wavelength dependence can seriously distort band shapes and apparent peak heights during collection of two-photon spectral data. Since two-photon excited fluorescence is proportional to the product of the peak and average powers, it is not possible to obtain source-independent spectra by using average power correction schemes alone. Continuous-wave, single-mode lasers can be used to generate source-independent two-photon data, but these sources are four to five orders of magnitude less efficient than the mode-locked Ti:S laser and are not practical for general two-photon measurements. Hence, a continuous-wave, single-mode Ti:S laser has been used to collect a source-independent excitation spectrum for the laser dye Coumarin 480. This spectrum may be used to correct data collected with multimode sources; this possibility is demonstrated by using a simple ratiometric method to collect accurate TPE spectra with the mode-locked Ti:S laser. An approximate value of the two-photon cross section for Coumarin 480 is also given. {copyright} {ital 1998} {ital Society for Applied Spectroscopy}

  18. Ultra-broadband photonic internet

    NASA Astrophysics Data System (ADS)

    Romaniuk, Ryszard S.

    2011-06-01

    In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

  19. Progress in 2D photonic crystal Fano resonance photonics

    NASA Astrophysics Data System (ADS)

    Zhou, Weidong; Zhao, Deyin; Shuai, Yi-Chen; Yang, Hongjun; Chuwongin, Santhad; Chadha, Arvinder; Seo, Jung-Hun; Wang, Ken X.; Liu, Victor; Ma, Zhenqiang; Fan, Shanhui

    2014-01-01

    In contrast to a conventional symmetric Lorentzian resonance, Fano resonance is predominantly used to describe asymmetric-shaped resonances, which arise from the constructive and destructive interference of discrete resonance states with broadband continuum states. This phenomenon and the underlying mechanisms, being common and ubiquitous in many realms of physical sciences, can be found in a wide variety of nanophotonic structures and quantum systems, such as quantum dots, photonic crystals, plasmonics, and metamaterials. The asymmetric and steep dispersion of the Fano resonance profile promises applications for a wide range of photonic devices, such as optical filters, switches, sensors, broadband reflectors, lasers, detectors, slow-light and non-linear devices, etc. With advances in nanotechnology, impressive progress has been made in the emerging field of nanophotonic structures. One of the most attractive nanophotonic structures for integrated photonics is the two-dimensional photonic crystal slab (2D PCS), which can be integrated into a wide range of photonic devices. The objective of this manuscript is to provide an in depth review of the progress made in the general area of Fano resonance photonics, focusing on the photonic devices based on 2D PCS structures. General discussions are provided on the origins and characteristics of Fano resonances in 2D PCSs. A nanomembrane transfer printing fabrication technique is also reviewed, which is critical for the heterogeneous integrated Fano resonance photonics. The majority of the remaining sections review progress made on various photonic devices and structures, such as high quality factor filters, membrane reflectors, membrane lasers, detectors and sensors, as well as structures and phenomena related to Fano resonance slow light effect, nonlinearity, and optical forces in coupled PCSs. It is expected that further advances in the field will lead to more significant advances towards 3D integrated photonics, flat

  20. Optical fiber dispersion characterization study

    NASA Technical Reports Server (NTRS)

    Geeslin, A.; Arriad, A.; Riad, S. M.; Padgett, M. E.

    1979-01-01

    The theory, design, and results of optical fiber pulse dispersion measurements are considered. Both the hardware and software required to perform this type of measurement are described. Hardware includes a thermoelectrically cooled injection laser diode source, an 800 GHz gain bandwidth produce avalanche photodiode and an input mode scrambler. Software for a HP 9825 computer includes fast Fourier transform, inverse Fourier transform, and optimal compensation deconvolution. Test set construction details are also included. Test results include data collected on a 1 Km fiber, a 4 Km fiber, a fused spliced, eight 600 meter length fibers concatenated to form 4.8 Km, and up to nine optical connectors.

  1. Photon generator

    DOEpatents

    Srinivasan-Rao, Triveni

    2002-01-01

    A photon generator includes an electron gun for emitting an electron beam, a laser for emitting a laser beam, and an interaction ring wherein the laser beam repetitively collides with the electron beam for emitting a high energy photon beam therefrom in the exemplary form of x-rays. The interaction ring is a closed loop, sized and configured for circulating the electron beam with a period substantially equal to the period of the laser beam pulses for effecting repetitive collisions.

  2. Self-assembled tunable photonic hyper-crystals

    PubMed Central

    Smolyaninova, Vera N.; Yost, Bradley; Lahneman, David; Narimanov, Evgenii E.; Smolyaninov, Igor I.

    2014-01-01

    We demonstrate a novel artificial optical material, the “photonic hyper-crystal”, which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. PMID:25027947

  3. Self-assembled tunable photonic hyper-crystals.

    PubMed

    Smolyaninova, Vera N; Yost, Bradley; Lahneman, David; Narimanov, Evgenii E; Smolyaninov, Igor I

    2014-01-01

    We demonstrate a novel artificial optical material, the "photonic hyper-crystal", which combines the most interesting features of hyperbolic metamaterials and photonic crystals. Similar to hyperbolic metamaterials, photonic hyper-crystals exhibit broadband divergence in their photonic density of states due to the lack of usual diffraction limit on the photon wave vector. On the other hand, similar to photonic crystals, hyperbolic dispersion law of extraordinary photons is modulated by forbidden gaps near the boundaries of photonic Brillouin zones. Three dimensional self-assembly of photonic hyper-crystals has been achieved by application of external magnetic field to a cobalt nanoparticle-based ferrofluid. Unique spectral properties of photonic hyper-crystals lead to extreme sensitivity of the material to monolayer coatings of cobalt nanoparticles, which should find numerous applications in biological and chemical sensing. PMID:25027947

  4. Laboratory atmospheric compensation experiment

    NASA Astrophysics Data System (ADS)

    Drutman, C.; Moran, James P.; Faria-e-Maia, Francisco; Hyman, Howard; Russell, Jeffrey A.

    1993-06-01

    This paper describes an in-house experiment that was performed at the Avco Research Labs/Textron to test a proprietary atmospheric phase compensation algorithm. Since the laser energies of interest were small enough that thermal blooming was not an issue, it was only necessary to simulate the effect of atmospheric turbulence. This was achieved by fabricating phase screens that mimicked Kolmogorov phase statistics. A simulated atmosphere was constructed from these phase screens and the phase at the simulated ground was measured with a digital heterodyne interferometer. The result of this effort was an initial verification of our proprietary algorithm two years before the field experiment.

  5. Large delay-bandwidth product and tuning of slow light pulse in photonic crystal coupled waveguide.

    PubMed

    Baba, Toshihiko; Kawaaski, Takashi; Sasaki, Hirokazu; Adachi, Jun; Mori, Daisuke

    2008-06-01

    This paper reports two advances in a slow light device consisting of chirped photonic crystal slab coupled waveguide on SOI substrate. One is concerning the delay-bandwidth product, indicating the buffering capacity of the device. We experimentally evaluated a record high value of 57 (a 40 ps delay and a 1.4 THz bandwidth). We also observed ~1 ps wide optical pulse transmission in the cross-correlation measurement. Regarding the pulse as a signal and considering the broadening of the pulse width due to the imperfect dispersion compensation in the device, storage of more than 12 signal bits was confirmed. The other is a wide-range tuning of the pulse delay. We propose a technique for externally controlling the chirping to permit variable delay. We demonstrate tuning of the pulse delay up to 23 ps, corresponding to a ~7 mm extension of the free space length. PMID:18545637

  6. Two-photon microscope for multisite microphotolysis of caged neurotransmitters in acute brain slices

    PubMed Central

    Losavio, Bradley E.; Iyer, Vijay; Saggau, Peter

    2009-01-01

    We developed a two-photon microscope optimized for physiologically manipulating single neurons through their postsynaptic receptors. The optical layout fulfills the stringent design criteria required for high-speed, high-resolution imaging in scattering brain tissue with minimal photodamage. We detail the practical compensation of spectral and temporal dispersion inherent in fast laser beam scanning with acousto-optic deflectors, as well as a set of biological protocols for visualizing nearly diffraction-limited structures and delivering physiological synaptic stimuli. The microscope clearly resolves dendritic spines and evokes electrophysiological transients in single neurons that are similar to endogenous responses. This system enables the study of multisynaptic integration and will assist our understanding of single neuron function and dendritic computation. PMID:20059271

  7. Tunable photonic elements at the surface of an optical fiber with piezoelectric core

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Sumetsky, M.

    2016-05-01

    Tunable photonic elements at the surface of an optical fiber with piezoelectric core are proposed and analyzed theoretically. These elements are based on whispering gallery modes whose propagation along the fiber is fully controlled by nanoscale variation of the effective fiber radius, which can be tuned by means of a piezoelectric actuator embedded into the core. The developed theory allows one to express the introduced effective radius variation through the shape of the actuator and the voltage applied to it. In particular, the design of a miniature tunable optical delay line and a miniature tunable dispersion compensator is presented. The potential application of the suggested model to the design of a miniature optical buffer is discussed.

  8. Two-photon microscope for multisite microphotolysis of caged neurotransmitters in acute brain slices

    NASA Astrophysics Data System (ADS)

    Losavio, Bradley E.; Iyer, Vijay; Saggau, Peter

    2009-11-01

    We developed a two-photon microscope optimized for physiologically manipulating single neurons through their postsynaptic receptors. The optical layout fulfills the stringent design criteria required for high-speed, high-resolution imaging in scattering brain tissue with minimal photodamage. We detail the practical compensation of spectral and temporal dispersion inherent in fast laser beam scanning with acousto-optic deflectors, as well as a set of biological protocols for visualizing nearly diffraction-limited structures and delivering physiological synaptic stimuli. The microscope clearly resolves dendritic spines and evokes electrophysiological transients in single neurons that are similar to endogenous responses. This system enables the study of multisynaptic integration and will assist our understanding of single neuron function and dendritic computation.

  9. Photonic preprocessor for analog-to-digital-converter using a cavity-less pulse source.

    PubMed

    Wiberg, Andreas O J; Liu, Lan; Tong, Zhi; Myslivets, Evgeny; Ataie, Vahid; Kuo, Bill P-P; Alic, Nikola; Radic, Stojan

    2012-12-10

    A photonic preprocessor for analog to digital conversion is demonstrated and characterized using a cavity-less optical pulse source. The pulse source generates high fidelity pulses at 2 GHz repetition rate with temporal width of 3 ps. Chirped pulses are formed by cascaded amplitude and phase modulators, and subsequently compressed in dispersion compensating fiber. Sampling operation is performed with a dual-output Mach-Zehnder modulator, where the complimentary output enables a reduction of noise by 3 dB. Phase noise characterization shows that the phase noise of the generated pulses is fully dictated by the RF source. The high quality of the pulse source used in a sampling preprocessor experiment was verified by measuring 8 effective number of bits at 10 GHz and 7.0 effective number of bits at 40 GHz. PMID:23262883

  10. Tunable photonic elements at the surface of an optical fiber with piezoelectric core.

    PubMed

    Dmitriev, A V; Sumetsky, M

    2016-05-15

    Tunable photonic elements at the surface of an optical fiber with piezoelectric core are proposed and analyzed theoretically. These elements are based on whispering gallery modes whose propagation along the fiber is fully controlled by nanoscale variation of the effective fiber radius, which can be tuned by means of a piezoelectric actuator embedded into the core. The developed theory allows one to express the introduced effective radius variation through the shape of the actuator and the voltage applied to it. In particular, the designs of a miniature tunable optical delay line and a miniature tunable dispersion compensator are presented. The potential application of the suggested model to the design of a miniature optical buffer is also discussed. PMID:27176953

  11. Colloidal Dispersions

    NASA Astrophysics Data System (ADS)

    Russel, W. B.; Saville, D. A.; Schowalter, W. R.

    1992-03-01

    The book covers the physical side of colloid science from the individual forces acting between submicron particles suspended in a liquid through the resulting equilibrium and dynamic properties. The relevant forces include Brownian motion, electrostatic repulsion, dispersion attraction, both attraction and repulsion due to soluble polymer, and viscous forces due to relative motion between the particles and the liquid. The balance among Brownian motion and the interparticle forces decides the questions of stability and phase behavior. Imposition of external fields produces complex effects, i.e. electrokinetic phenomena (electric field), sedimentation (gravitational field), diffusion (concentration/chemical potential gradient), and non-Newtonian rheology (shear field). The treatment aims to impart a sound, quantitative understanding based on fundamental theory and experiments with well-characterized model systems. This broad grasp of the fundamentals lends insight and helps to develop the intuitive sense needed to isolate essential features of technological problems and design critical experiments. Some exposure to fluid mechanics, statistical mechanics, and electricity and magnetism is assumed, but each subject is reintroduced in a self-contained manner.

  12. Extrathermodynamics: Varieties of Compensation Effect.

    PubMed

    Khakhel', Oleg A; Romashko, Tamila P

    2016-03-31

    There are several types of the ΔH compensation. Along with well-known phenomenon of the ΔH - ΔS compensation, two more types of the ΔH - (ΔS + RΔ ln Ω) compensation are observed in some series of systems. The nature of these phenomena is connected with the behavior of phase volume of systems, Ω. The role of other thermodynamic parameters, which describe series in manifestation of this or that types of the ΔH compensation, is shown in light of molecular statistical mechanics. PMID:26949977

  13. Compensations during Unsteady Locomotion.

    PubMed

    Qiao, Mu; Jindrich, Devin L

    2014-12-01

    Locomotion in a complex environment is often not steady, but the mechanisms used by animals to power and control unsteady locomotion (stability and maneuverability) are not well understood. We use behavioral, morphological, and impulsive perturbations to determine the compensations used during unsteady locomotion. At the level both of the whole-body and of joints, quasi-stiffness models are useful for describing adjustments to the functioning of legs and joints during maneuvers. However, alterations to the mechanics of legs and joints often are distinct for different phases of the step cycle or for specific joints. For example, negotiating steps involves independent changes of leg stiffness during compression and thrust phases of stance. Unsteady locomotion also involves parameters that are not part of the simplest reduced-parameter models of locomotion (e.g., the spring-loaded inverted pendulum) such as moments of the hip joint. Extensive coupling among translational and rotational parameters must be taken into account to stabilize locomotion or maneuver. For example, maneuvers with morphological perturbations (increased rotational inertial turns) involve changes to several aspects of movement, including the initial conditions of rotation and ground-reaction forces. Coupled changes to several parameters may be employed to control maneuvers on a trial-by-trial basis. Compensating for increased rotational inertia of the body during turns is facilitated by the opposing effects of several mechanical and behavioral parameters. However, the specific rules used by animals to control translation and rotation of the body to maintain stability or maneuver have not been fully characterized. We initiated direct-perturbation experiments to investigate the strategies used by humans to maintain stability following center-of-mass (COM) perturbations. When walking, humans showed more resistance to medio-lateral perturbations (lower COM displacement). However, when running, humans

  14. Green photonics

    NASA Astrophysics Data System (ADS)

    Quan, Frederic

    2012-02-01

    Photonics, the broad merger of electronics with the optical sciences, encompasses such a wide swath of technology that its impact is almost universal in our everyday lives. This is a broad overview of some aspects of the industry and their contribution to the ‘green’ or environmental movement. The rationale for energy conservation is briefly discussed and the impact of photonics on our everyday lives and certain industries is described. Some opinions from industry are presented along with market estimates. References are provided to some of the most recent research in these areas.

  15. Photons Revisited

    NASA Astrophysics Data System (ADS)

    Batic, Matej; Begalli, Marcia; Han, Min Cheol; Hauf, Steffen; Hoff, Gabriela; Kim, Chan Hyeong; Kim, Han Sung; Grazia Pia, Maria; Saracco, Paolo; Weidenspointner, Georg

    2014-06-01

    A systematic review of methods and data for the Monte Carlo simulation of photon interactions is in progress: it concerns a wide set of theoretical modeling approaches and data libraries available for this purpose. Models and data libraries are assessed quantitatively with respect to an extensive collection of experimental measurements documented in the literature to determine their accuracy; this evaluation exploits rigorous statistical analysis methods. The computational performance of the associated modeling algorithms is evaluated as well. An overview of the assessment of photon interaction models and results of the experimental validation are presented.

  16. Summing pressure compensation control

    SciTech Connect

    Myers, H.A.

    1988-04-26

    This patent describes a summing pressure compensator control for hydraulic loads with at least one of the hydraulic loads being a variable displacement motor having servo means for controlling the displacement thereof, first hydraulic means responsive to the supply of fluid to the variable displacement motor to provide a first pressure signal, second hydraulic means responsive to the supply of fluid to a second hydraulic load to provide a second pressure signal, summing means for receiving the first and second pressure signals and providing a control signal proportional to the sum of the first and second pressure signals, the control signal being applied to the servo means to increase the displacement of the variable displacement motor.

  17. Temperature compensated photovoltaic array

    DOEpatents

    Mosher, Dan Michael

    1997-11-18

    A temperature compensated photovoltaic module (20) comprised of a series of solar cells (22) having a thermally activated switch (24) connected in parallel with several of the cells (22). The photovoltaic module (20) is adapted to charge conventional batteries having a temperature coefficient (TC) differing from the temperature coefficient (TC) of the module (20). The calibration temperatures of the switches (24) are chosen whereby the colder the ambient temperature for the module (20), the more switches that are on and form a closed circuit to short the associated solar cells (22). By shorting some of the solar cells (22) as the ambient temperature decreases, the battery being charged by the module (20) is not excessively overcharged at lower temperatures. PV module (20) is an integrated solution that is reliable and inexpensive.

  18. Temperature compensated photovoltaic array

    DOEpatents

    Mosher, D.M.

    1997-11-18

    A temperature compensated photovoltaic module comprises a series of solar cells having a thermally activated switch connected in parallel with several of the cells. The photovoltaic module is adapted to charge conventional batteries having a temperature coefficient differing from the temperature coefficient of the module. The calibration temperatures of the switches are chosen whereby the colder the ambient temperature for the module, the more switches that are on and form a closed circuit to short the associated solar cells. By shorting some of the solar cells as the ambient temperature decreases, the battery being charged by the module is not excessively overcharged at lower temperatures. PV module is an integrated solution that is reliable and inexpensive. 2 figs.

  19. Photon-phonon anti-stokes upconversion of a photonically, electronically, and thermally isolated opal

    NASA Astrophysics Data System (ADS)

    Stem, Michelle R.

    2016-05-01

    The purpose of the present research was to investigate an intense violet shift displayed by a non-toxic, natural silicate material with a highly ordered nanostructure. The material displayed an unexpected, nonlinear 2:3 photon-phonon anti-Stokes upconversion while photonically, electronically, and thermally isolated. Conducted aphotonically and at ambient temperatures, the specimen upconverted a low-power, 650 nm constant wave red laser to an internally highly dispersed 433 nm violet wavelength. The strong dispersion was largely due to nearly total internal reflection of the laser. The upconversion had an efficiency of about 78 %, based on specimen volume, with no detectable thermal variance. The 2:3 anti-Stokes upconversion displayed by this material is likely the result of a previously unknown photon-phonon evanescence response that amplified the energy of a portion of the incident laser photons. Thus, a portion of the incident laser photons were upconverted, and the material converted another portion into an amplified energy that caused the upconversion. Internal micro-lasing appeared to be a means of photon-phonon evanescent energy redistribution, enabling dispersed photonic upconversion. Additional analyses also found an unexpectedly rhythmic photonic structure in spectrophotometric scans, polariscopic color changing, and previously undocumented ultraviolet responses.

  20. Longitudinal photons in a relativistic magneto-active plasma

    SciTech Connect

    Tsintsadze, N. L.; Rehman, Ayesha; Murtaza, G.; Shah, H. A.

    2007-10-15

    This paper presents some aspects of interaction of superstrong high-frequency electromagnetic waves with strongly magnetized plasmas. The case in which the photon-photon interaction dominates the photon-plasma particle interaction is considered. Strictly speaking, the photon and photon bunch interaction leads to the self-modulation of the photon gas. Assuming that the density of the plasma does not change, the dispersion relation, which includes relativistic self-modulation, is investigated. The existence of longitudinal photons in a strong magnetic field has the well-known Bogoliubov-type energy spectrum. The stability of the photon flow is investigated and an expression for Landau damping of the photons is obtained. Finally, it has been shown that the interaction of even a very strong electromagnetic radiation with a plasma does not always lead to instability, but causes only a change in plasma properties, whereby the plasma remains stable.

  1. One-Dimensional Photonic Crystal Superprisms

    NASA Technical Reports Server (NTRS)

    Ting, David

    2005-01-01

    Theoretical calculations indicate that it should be possible for one-dimensional (1D) photonic crystals (see figure) to exhibit giant dispersions known as the superprism effect. Previously, three-dimensional (3D) photonic crystal superprisms have demonstrated strong wavelength dispersion - about 500 times that of conventional prisms and diffraction gratings. Unlike diffraction gratings, superprisms do not exhibit zero-order transmission or higher-order diffraction, thereby eliminating cross-talk problems. However, the fabrication of these 3D photonic crystals requires complex electron-beam substrate patterning and multilayer thin-film sputtering processes. The proposed 1D superprism is much simpler in structural complexity and, therefore, easier to design and fabricate. Like their 3D counterparts, the 1D superprisms can exhibit giant dispersions over small spectral bands that can be tailored by judicious structure design and tuned by varying incident beam direction. Potential applications include miniature gas-sensing devices.

  2. Fiber transport of spatially entangled photons

    NASA Astrophysics Data System (ADS)

    Löffler, W.; Eliel, E. R.; Woerdman, J. P.; Euser, T. G.; Scharrer, M.; Russell, P.

    2012-03-01

    High-dimensional entangled photons pairs are interesting for quantum information and cryptography: Compared to the well-known 2D polarization case, the stronger non-local quantum correlations could improve noise resistance or security, and the larger amount of information per photon increases the available bandwidth. One implementation is to use entanglement in the spatial degree of freedom of twin photons created by spontaneous parametric down-conversion, which is equivalent to orbital angular momentum entanglement, this has been proven to be an excellent model system. The use of optical fiber technology for distribution of such photons has only very recently been practically demonstrated and is of fundamental and applied interest. It poses a big challenge compared to the established time and frequency domain methods: For spatially entangled photons, fiber transport requires the use of multimode fibers, and mode coupling and intermodal dispersion therein must be minimized not to destroy the spatial quantum correlations. We demonstrate that these shortcomings of conventional multimode fibers can be overcome by using a hollow-core photonic crystal fiber, which follows the paradigm to mimic free-space transport as good as possible, and are able to confirm entanglement of the fiber-transported photons. Fiber transport of spatially entangled photons is largely unexplored yet, therefore we discuss the main complications, the interplay of intermodal dispersion and mode mixing, the influence of external stress and core deformations, and consider the pros and cons of various fiber types.

  3. Processing and error compensation of diffractive optical element

    NASA Astrophysics Data System (ADS)

    Zhang, Yunlong; Wang, Zhibin; Zhang, Feng; Qin, Hui; Li, Junqi; Mai, Yuying

    2014-09-01

    Diffractive optical element (DOE) shows high diffraction efficiency and good dispersion performance, which makes the optical system becoming light-weight and more miniature. In this paper, the design, processing, testing, compensation of DOE are discussed, especially the analyzing of compensation technology which based on the analyzing the DOE measurement date from Taylor Hobson PGI 1250. In this method, the relationship between shadowing effect with diamond tool and processing accuracy are analyzed. According to verification processing on the Taylor Hobson NANOFORM 250 lathe, the results indicate that the PV reaches 0.539 micron, the surface roughness reaches 4nm, the step position error is smaller than λ /10 and the step height error is less than 0.23 micron after compensation processing one time.

  4. Mitigating Photon Jitter in Optical PPM Communication

    NASA Technical Reports Server (NTRS)

    Moision, Bruce

    2008-01-01

    A theoretical analysis of photon-arrival jitter in an optical pulse-position-modulation (PPM) communication channel has been performed, and now constitutes the basis of a methodology for designing receivers to compensate so that errors attributable to photon-arrival jitter would be minimized or nearly minimized. Photon-arrival jitter is an uncertainty in the estimated time of arrival of a photon relative to the boundaries of a PPM time slot. Photon-arrival jitter is attributable to two main causes: (1) receiver synchronization error [error in the receiver operation of partitioning time into PPM slots] and (2) random delay between the time of arrival of a photon at a detector and the generation, by the detector circuitry, of a pulse in response to the photon. For channels with sufficiently long time slots, photon-arrival jitter is negligible. However, as durations of PPM time slots are reduced in efforts to increase throughputs of optical PPM communication channels, photon-arrival jitter becomes a significant source of error, leading to significant degradation of performance if not taken into account in design. For the purpose of the analysis, a receiver was assumed to operate in a photon- starved regime, in which photon counts follow a Poisson distribution. The analysis included derivation of exact equations for symbol likelihoods in the presence of photon-arrival jitter. These equations describe what is well known in the art as a matched filter for a channel containing Gaussian noise. These equations would yield an optimum receiver if they could be implemented in practice. Because the exact equations may be too complex to implement in practice, approximations that would yield suboptimal receivers were also derived.

  5. Optimizing optical pre-dispersion using transmit DSP for mitigation of Kerr nonlinearities in dispersion managed cables

    NASA Astrophysics Data System (ADS)

    Hopkins, James; Gaudette, Jamie; Mehta, Priyanth

    2013-10-01

    With the advent of digital signal processing (DSP) in optical transmitters and receivers, the ability to finely tune the ratio of pre and post dispersion compensation can be exploited to best mitigate the nonlinear penalties caused by the Kerr effect. A portion of the nonlinear penalty in optical communication channels has been explained by an increase in peak to average power ratio (PAPR) inherent in highly dispersed signals. The standard approach for minimizing these impairments applies 50% pre dispersion compensation and 50% post dispersion compensation, thereby decreasing average PAPR along the length of the cable, as compared with either 100% pre or post dispersion compensation. In this paper we demonstrate that simply considering the net accumulated dispersion, and applying 50/50 pre/post dispersion is not necessarily the best way to minimize PAPR and subsequent Kerr nonlinearities. Instead, we consider the cumulative dispersion along the entire length of the cable, and, taking into account this additional information, derive an analytic formula for the minimization of PAPR. Alignment with simulation and experimental measurements is presented using a commercially available 100Gb/s dual-polarization binary phase-shift-keying (DP-BPSK) coherent modem, with transmitter and receiver DSP. Measurements are provided from two different 5000km dispersion managed Submarine test-beds, as well as a 3800km terrestrial test-bed with a mixture of SMF-28 and TWRS optical fiber. This method is shown to deviate significantly from the conventional 50/50 method described above, in dispersion managed communications systems, and more closely aligns with results obtained from simulation and data collected from laboratory test-beds.

  6. Primary-care physician compensation.

    PubMed

    Olson, Arik

    2012-01-01

    This article reviews existing models of physician compensation and presents information about current compensation patterns for primary-care physicians in the United States. Theories of work motivation are reviewed where they have relevance to the desired outcome of satisfied, productive physicians whose skills and expertise are retained in the workforce. Healthcare reforms that purport to bring accountability for healthcare quality and value-rather than simply volume-bring opportunities to redesign primary-care physician compensation and may allow for new compensation methodologies that increase job satisfaction. Physicians are increasingly shunning the responsibility of private practice and choosing to work as employees of a larger organization, often a hospital. Employers of physicians are seeking compensation models that reward both productivity and value. PMID:22786738

  7. 38 CFR 3.4 - Compensation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Compensation. 3.4 Section 3.4 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION Pension, Compensation, and Dependency and Indemnity Compensation General § 3.4 Compensation. (a) Compensation. This term means a monthly payment made by...

  8. Research on the critical parameters initialization of optical PMD compensator in high bit-rate systems

    NASA Astrophysics Data System (ADS)

    Zhao, Wenyu; Zhang, Haiyi; Ji, Yuefeng; Xu, Daxiong

    2004-05-01

    Based on the proposed polarization mode dispersion (PMD) compensation simulation model and statistical analysis method (Monte-Carlo), the critical parameters initialization of two typical optical domain PMD compensators, which include optical PMD method with fixed compensation differential group delay (DGD) and that with variable compensation DGD, are detailedly investigated by numerical method. In the simulation, the line PMD values are chosen as 3ps, 4ps and 5ps and run samples are set to 1000 in order to achieve statistical evaluation for PMD compensated systems, respectively. The simulation results show that for the PMD value pre-known systems, the value of the fixed DGD compensator should be set to 1.5~1.6 times of line PMD value in order to reach the optimum performance, but for the second kind of PMD compensator, the DGD range of lower limit should be 1.5~1.6 times of line PMD provided that of upper limit is set to 3 times of line PMD, if no effective ways are chosen to resolve the problem of local minimum in optimum process. Another conclusion can be drawn from the simulation is that, although the second PMD compensator holds higher PMD compensation performance, it will spend more feedback loops to look up the optimum DGD value in the real PMD compensation realization, and this will bring more requirements on adjustable DGD device, not only wider adjustable range, but rapid adjusting speed for real time PMD equalization.

  9. Fano resonance in anodic aluminum oxide based photonic crystals

    PubMed Central

    Shang, Guo Liang; Fei, Guang Tao; Zhang, Yao; Yan, Peng; Xu, Shao Hui; Ouyang, Hao Miao; De Zhang, Li

    2014-01-01

    Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile. PMID:24398625

  10. Influence of compensator thickness, field size, and off-axis distance on the effective attenuation coefficient of a cerrobend compensator for intensity-modulated radiation therapy

    SciTech Connect

    Haghparast, Abbas; Hashemi, Bijan; Eivazi, Mohammad Taghi

    2013-04-01

    Intensity-modulated radiation therapy (IMRT) can be performed by using compensators. To make a compensator for an IMRT practice, it is required to calculate the effective attenuation coefficient (μ{sub eff}) of its material, which is affected by various factors. We studied the effect of the variation of the most important factors on the calculation of the μ{sub eff} of the cerrobend compensator for 6-MV photon beams, including the field size, compensator thickness, and off-axis distance. Experimental measurements were carried out at 100 cm source-to-surface distance and 10 cm depth for the 6-MV photon beams of an Elekta linac using various field size, compensator thickness, and off-axis settings. The field sizes investigated ranged from 4 × 4 to 25 × 25 cm{sup 2} and the cerrobend compensator thicknesses from 0.5–6 cm. For a fixed compensator thickness, variation of the μ{sub eff} with the field size ranged from 3.7–6.8%, with the highest value attributed to the largest compensator thickness. At the reference field size of 10 × 10 cm{sup 2}, the μ{sub eff} varied by 16.5% when the compensator thickness was increased from 0.5–6 cm. However, the variation of the μ{sub eff} with the off-axis distance was only 0.99% at this field size, whereas for the largest field size, it was more significant. Our results indicated that the compensator thickness and field size have the most significant effect on the calculation of the compensator μ{sub eff} for the 6-MV photon beam. Therefore, it is recommended to consider these parameters when calculating the compensator thickness for an IMRT practice designed for these beams. The off-axis distance had a significant effect on the calculation of the μ{sub eff} only for the largest field size. Hence, it is recommended to consider the effect of this parameter only for field sizes larger than 25 × 25 cm{sup 2}.

  11. [Vestibular compensation studies]. [Vestibular Compensation and Morphological Studies

    NASA Technical Reports Server (NTRS)

    Perachio, Adrian A. (Principal Investigator)

    1996-01-01

    The following topics are reported: neurophysiological studies on MVN neurons during vestibular compensation; effects of spinal cord lesions on VNC neurons during compensation; a closed-loop vestibular compensation model for horizontally canal-related MVN neurons; spatiotemporal convergence in VNC neurons; contributions of irregularly firing vestibular afferents to linear and angular VOR's; application to flight studies; metabolic measures in vestibular neurons; immediate early gene expression following vestibular stimulation; morphological studies on primary afferents, central vestibular pathways, vestibular efferent projection to the vestibular end organs, and three-dimensional morphometry and imaging.

  12. Photon Collider Physics with Real Photon Beams

    SciTech Connect

    Gronberg, J; Asztalos, S

    2005-11-03

    Photon-photon interactions have been an important probe into fundamental particle physics. Until recently, the only way to produce photon-photon collisions was parasitically in the collision of charged particles. Recent advances in short-pulse laser technology have made it possible to consider producing high intensity, tightly focused beams of real photons through Compton scattering. A linear e{sup +}e{sup -} collider could thus be transformed into a photon-photon collider with the addition of high power lasers. In this paper they show that it is possible to make a competitive photon-photon collider experiment using the currently mothballed Stanford Linear Collider. This would produce photon-photon collisions in the GeV energy range which would allow the discovery and study of exotic heavy mesons with spin states of zero and two.

  13. Compensated pulsed alternator

    DOEpatents

    Weldon, William F.; Driga, Mircea D.; Woodson, Herbert H.

    1980-01-01

    This invention relates to an electromechanical energy converter with inertial energy storage. The device, a single phase, two or multi-pole alternator with stationary field coils, and a rotating armature is provided. The rotor itself may be of laminated steel for slower pulses or for faster pulses should be nonmagnetic and electrically nonconductive in order to allow rapid penetration of the field as the armature coil rotates. The armature coil comprises a plurality of power generating conductors mounted on the rotor. The alternator may also include a stationary or counterrotating compensating coil to increase the output voltage thereof and to reduce the internal impedance of the alternator at the moment of peak outout. As the machine voltage rises sinusoidally, an external trigger switch is adapted to be closed at the appropriate time to create the desired output current from said alternator to an external load circuit, and as the output current passes through zero a self-commutating effect is provided to allow the switch to disconnect the generator from the external circuit.

  14. Convection Compensated Electrophoretic NMR

    NASA Astrophysics Data System (ADS)

    He, Qiuhong; Wei, Zhaohui

    2001-06-01

    A novel method of convection compensated ENMR (CC-ENMR) has been developed to detect electrophoretic motion of ionic species in the presence of bulk solution convection. This was accomplished using a gradient moment nulling technique to remove spectral artifacts from heat-induced convection and using the polarity switch of the applied electric field to retain spin phase modulations due to electrophoretic flow. Experiments were carried out with a mixture of 100 mM L-aspartic acid and 100 mM 4,9-dioxa-1,12-dodecanediamine to demonstrate this new method of ENMR. CC-ENMR enhances our previously developed capillary array ENMR (CA-ENMR) in solving the convection problem. The combined CA- and CC-ENMR approach strengthens the potential of multidimensional ENMR in simultaneous structural determination of coexisting proteins and protein conformations in biological buffer solutions of high ionic strength. Structural mapping of interacting proteins during biochemical reactions becomes possible in the future using ENMR techniques, which may have a profound impact on the understanding of biological events, including protein folding, genetic control, and signal transduction in general.

  15. Analytical expressions for group-delay dispersion and third-order dispersion of a reflection grism-pair compressor.

    PubMed

    Su, Juan; Feng, Guoying

    2012-05-10

    We provide a detailed analytical expression of group-delay dispersion (GDD) and third-order dispersion (TOD) for a reflection grism-pair compressor without the first-order approximation of grating diffraction. The analytical expressions can be used to design a grism-pair compressor for compensating the dispersive material without ray tracing. Furthermore, the dispersion performance of the grism pair compressor, depending on compressor parameters, is comprehensively analyzed. Results are shown that we can adjust several parameters to obtain a certain GDD and TOD, such as the incidence angle of the beam, refractive index of the prism, grating constant, and the separation of the grism pair. PMID:22614499

  16. An overview of turbulence compensation

    NASA Astrophysics Data System (ADS)

    Schutte, Klamer; van Eekeren, Adam W. M.; Dijk, Judith; Schwering, Piet B. W.; van Iersel, Miranda; Doelman, Niek J.

    2012-09-01

    In general, long range visual detection, recognition and identification are hampered by turbulence caused by atmospheric conditions. Much research has been devoted to the field of turbulence compensation. One of the main advantages of turbulence compensation is that it enables visual identification over larger distances. In many (military) scenarios this is of crucial importance. In this paper we give an overview of several software and hardware approaches to compensate for the visual artifacts caused by turbulence. These approaches are very diverse and range from the use of dedicated hardware, such as adaptive optics, to the use of software methods, such as deconvolution and lucky imaging. For each approach the pros and cons are given and it is indicated for which type of scenario this approach is useful. In more detail we describe the turbulence compensation methods TNO has developed in the last years and place them in the context of the different turbulence compensation approaches and TNO's turbulence compensation roadmap. Furthermore we look forward and indicate the upcoming challenges in the field of turbulence compensation.

  17. The photon magnetic moment problem revisited

    NASA Astrophysics Data System (ADS)

    Pérez Rojas, H.; Rodríguez Querts, E.

    2014-06-01

    The photon magnetic moment for radiation propagating in magnetized vacuum is defined as a pseudotensor quantity, proportional to the external electromagnetic field tensor. After expanding the eigenvalues of the polarization operator in powers of , we obtain approximate dispersion equations (cubic in ), and analytic solutions for the photon magnetic moment, valid for low momentum and/or large magnetic field. The paramagnetic photon experiences a redshift, with opposite sign to the gravitational one, which differs for parallel and perpendicular polarizations. It is due to the drain of photon transverse momentum and energy by the external field. By defining an effective transverse momentum, the constancy of the speed of light orthogonal to the field is guaranteed. We conclude that the propagation of the photon non-parallel to the magnetic direction behaves as if there is a quantum compression of the vacuum or a warp of space-time in an amount depending on its angle with regard to the field.

  18. New two-dimensional photon camera

    NASA Technical Reports Server (NTRS)

    Papaliolios, C.; Mertz, L.

    1982-01-01

    A photon-sensitive camera, applicable to speckle imaging of astronomical sources, high-resolution spectroscopy of faint galaxies in a crossed-dispersion spectrograph, or narrow-band direct imaging of galaxies, is presented. The camera is shown to supply 8-bit by 8-bit photon positions (256 x 256 pixels) for as many as 10 to the 6th photons/sec with a maximum linear resolution of approximately 10 microns. The sequence of photon positions is recorded digitally with a VHS-format video tape recorder or formed into an immediate image via a microcomputer. The four basic elements of the camera are described in detail: a high-gain image intensifier with fast-decay output phosphor, a glass-prism optical-beam splitter, a set of Gray-coded masks, and a photomultiplier tube for each mask. The characteristics of the camera are compared to those of other photon cameras.

  19. Integrated photonics

    NASA Astrophysics Data System (ADS)

    Gondarenko, Alexander A.

    In 1958 the first integrated circuit was demonstrated to combine transistors, resistors, and capacitors [36]. To this date fabrication technology has been driven by the growing demand for monolithically constructed, densely packed electronic components. The exponentially shrinking device size decreased the feature dimensions from 10 microns to 32 nm and grew transistor count from 2,300 to over 2,000,000,000 in Intel's 4004 and Intel Kentsfield XE microprocessors. The benefits of micro- and nano-fabrication was not limited to just computer chips. MEMs, spintronic, microfluidics, and integrated photonics were all made possible by the ever expanding ability to form complex geometries, on a wide variety of materials, on a micron and submicron scale. This dissertation is part of an effort to design and fabricate novel integrated photonic devices compatible with standard electron beam and photo lithography and utilize a readily available material base. We aim to create devices with a decreased footprint on a chip and operate in the infrared, visible, and UV spectra. We present two general sections, the first is a theoretical effort to find the fundamental design geometries for a variety of optical problems. The second section is an experimental demonstration of techniques and devices for novel optical phenomena in an integrated package. In the theoretical section we develop and apply computational evolutionary algorithms to explore problems of light confinement, coupling, and guiding in two and three dimensional device geometries. Our general aim is to find a global limit to optimal device geometry and performance given a set of constrains. Experimentally, we demonstrate an efficient design and a fabrication process for a short development cycle of photonic devices. For the design part of the workflow, we develop a computational approach to explore device geometries with minimum initial assumptions for a variety of photonic problems. For the fabrication part of the

  20. 33 CFR 136.113 - Other compensation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) MARINE POLLUTION FINANCIAL RESPONSIBILITY AND COMPENSATION OIL SPILL LIABILITY TRUST FUND; CLAIMS... claimant must include an accounting, including the source and value, of all other compensation...

  1. Dispersion interferometer using modulation amplitudes on LHD (invited)

    SciTech Connect

    Akiyama, T. Yasuhara, R.; Kawahata, K.; Okajima, S.; Nakayama, K.

    2014-11-15

    Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup −3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup −3} can be overcome by a sufficient sampling rate of about 100 kHz.

  2. Temperature-compensating dc restorer

    NASA Technical Reports Server (NTRS)

    Thomas, H. M.

    1980-01-01

    Circuit provides stable references restoration in addition to temperature compensation. Possible TV monitor applications include traffic and security surveillance systems, where cameras are subject to environmental extremes, as in unheated warehouses or outdoors.

  3. Development and evaluation of a model-based downscatter compensation method for quantitative I-131 SPECT

    PubMed Central

    Song, Na; Du, Yong; He, Bin; Frey, Eric C.

    2011-01-01

    Purpose: The radionuclide 131I has found widespread use in targeted radionuclide therapy (TRT), partly due to the fact that it emits photons that can be imaged to perform treatment planning or posttherapy dose verification as well as beta rays that are suitable for therapy. In both the treatment planning and dose verification applications, it is necessary to estimate the activity distribution in organs or tumors at several time points. In vivo estimates of the 131I activity distribution at each time point can be obtained from quantitative single-photon emission computed tomography (QSPECT) images and organ activity estimates can be obtained either from QSPECT images or quantification of planar projection data. However, in addition to the photon used for imaging, 131I decay results in emission of a number of other higher-energy photons with significant abundances. These higher-energy photons can scatter in the body, collimator, or detector and be counted in the 364 keV photopeak energy window, resulting in reduced image contrast and degraded quantitative accuracy; these photons are referred to as downscatter. The goal of this study was to develop and evaluate a model-based downscatter compensation method specifically designed for the compensation of high-energy photons emitted by 131I and detected in the imaging energy window. Methods: In the evaluation study, we used a Monte Carlo simulation (MCS) code that had previously been validated for other radionuclides. Thus, in preparation for the evaluation study, we first validated the code for 131I imaging simulation by comparison with experimental data. Next, we assessed the accuracy of the downscatter model by comparing downscatter estimates with MCS results. Finally, we combined the downscatter model with iterative reconstruction-based compensation for attenuation (A) and scatter (S) and the full (D) collimator-detector response of the 364 keV photons to form a comprehensive compensation method. We evaluated this

  4. Economics of static VAR compensation

    SciTech Connect

    Alvarado, F.L.; DeMarco, C.; Jung, T.H. . Dept. of Electrical and Computer Engineering)

    1992-09-01

    This project was initiated in anticipation of widened use of static VAR (volt-ampere-reactive) compensation on US bulk-power transmission systems to increase levels of secure power transfer. Project objectives were to deten-nine power system cost savings and reliability benefits resulting from such use. System operating cost and stability probabilities were compared with and without static VAR compensation, applying simulation techniques. For the particular system model studied, there was a 21.4 percent reduction in operating costs taking into account losses added by the static VAR compensator. A procedure was developed to compare instability probabilities for various loadings and static VAR compensator sizes on a power system. For the particular system model studied, the static VAR compensator provided a significant increase in stability but over a narrow range of loading. Static VAR compensation is one of a number of promising FACTS (Flexible AC Transmission System) technologies for handling the demands of increased power transfers on power systems where transmission lines cannot be built or as a short-term altemative to building additional lines.

  5. Photonic Nanojets

    PubMed Central

    Heifetz, Alexander; Kong, Soon-Cheol; Sahakian, Alan V.; Taflove, Allen; Backman, Vadim

    2009-01-01

    This paper reviews the substantial body of literature emerging since 2004 concerning photonic nanojets. The photonic nanojet is a narrow, high-intensity, non-evanescent light beam that can propagate over a distance longer than the wavelength λ after emerging from the shadow-side surface of an illuminated lossless dielectric microcylinder or microsphere of diameter larger than λ. The nanojet’s minimum beamwidth can be smaller than the classical diffraction limit, in fact as small as ~λ/3 for microspheres. It is a nonresonant phenomenon appearing for a wide range of diameters of the microcylinder or microsphere if the refractive index contrast relative to the background is less than about 2:1. Importantly, inserting within a nanojet a nanoparticle of diameter dν perturbs the far-field backscattered power of the illuminated microsphere by an amount that varies as dν3 for a fixed λ. This perturbation is much slower than the dν6 dependence of Rayleigh scattering for the same nanoparticle, if isolated. This leads to a situation where, for example, the measured far-field backscattered power of a 3-μm diameter microsphere could double if a 30-nm diameter nanoparticle were inserted into the nanojet emerging from the microsphere, despite the nanoparticle having only 1/10,000th the cross-section area of the microsphere. In effect, the nanojet serves to project the presence of the nanoparticle to the far field. These properties combine to afford potentially important applications of photonic nanojets for detecting and manipulating nanoscale objects, subdiffraction-resolution nanopatterning and nanolithography, low-loss waveguiding, and ultrahigh-density optical storage. PMID:19946614

  6. Photon detector configured to employ the Gunn effect and method of use

    SciTech Connect

    Cich, Michael J

    2015-03-17

    Embodiments disclosed herein relate to photon detectors configured to employ the Gunn effect for detecting high-energy photons (e.g., x-rays and gamma rays) and methods of use. In an embodiment, a photon detector for detecting high-energy photons is disclosed. The photon detector includes a p-i-n semiconductor diode having a p-type semiconductor region, an n-type semiconductor region, and a compensated i-region disposed between the p-type semiconductor region and the n-type semiconductor region. The compensated i-region and has a width of about 100 .mu.m to about 400 .mu.m and is configured to exhibit the Gunn effect when the p-i-n semiconductor diode is forward biased a sufficient amount. The compensated i-region is doped to include a free carrier concentration of less than about 10.sup.10 cm.sup.-3.

  7. Photon calorimeter

    DOEpatents

    Chow, Tze-Show

    1988-04-22

    A photon calorimeter is provided that comprises a laminar substrate that is uniform in density and homogeneous in atomic composition. A plasma-sprayed coating, that is generally uniform in density and homogeneous in atomic composition within the proximity of planes that are parallel to the surfaces of the substrate, is applied to either one or both sides of the laminar substrate. The plasma-sprayed coatings may be very efficiently spectrally tailored in atomic number. Thermocouple measuring junctions, are positioned within the plasma-sprayed coatings. The calorimeter is rugged, inexpensive, and equilibrates in temperature very rapidly. 4 figs.

  8. Photon Calorimeter

    DOEpatents

    Chow, Tze-Show

    1989-01-01

    A photon calorimeter (20, 40) is provided that comprises a laminar substrate (10, 22, 42) that is uniform in density and homogeneous in atomic composition. A plasma-sprayed coating (28, 48, 52), that is generally uniform in density and homogeneous in atomic composition within the proximity of planes that are parallel to the surfaces of the substrate, is applied to either one or both sides of the laminar substrate. The plasma-sprayed coatings may be very efficiently spectrally tailored in atomic number. Thermocouple measuring junctions (30, 50, 54) are positioned within the plasma-sprayed coatings. The calorimeter is rugged, inexpensive, and equilibrates in temperature very rapidly.

  9. ICA-based compensation for IQ imbalance in OFDM optical fiber communication

    NASA Astrophysics Data System (ADS)

    Jiang, Shan; Hu, Guijun; Li, Zhaoxi; Mu, Liping; Zhang, Jingdong

    2014-01-01

    A method based on the independent component analysis (ICA) is proposed to compensate the in-phase and quadrature-phase the (IQ) imbalance in orthogonal frequency division multiplexing (OFDM) optical fiber communication systems. The mathematical model of IQ imbalance system has been analyzed. Then, ICA algorithm is applied in the system to combat the mirror interference introduced by IQ imbalance. This algorithm can realize the joint compensation of both transmitter and receiver IQ imbalance with the optical channel that contains noise, attenuation and chromatic dispersion. The simulation shows that the performance degradation caused by IQ imbalance can be compensated by ICA algorithm effectively.

  10. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    SciTech Connect

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  11. Compensated bismuth-loaded plastic scintillators for neutron detection using low-energy pseudo-spectroscopy

    NASA Astrophysics Data System (ADS)

    Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.; Normand, Stéphane; Méchin, Laurence; Hamel, Matthieu

    2016-05-01

    Gadolinium-covered modified plastic scintillators show a high potential for the deployment of cost-effective neutron detectors. Taking advantage of the low-energy photon and electron signature of thermal neutron captures in gadolinium-155 and gadolinium-157 however requires a background correction. In order to display a trustable rate, dual compensation schemes appear as an alternative to Pulse Shape Discrimination. This paper presents the application of such a compensation scheme to a two-bismuth loaded plastic scintillator system. A detection scintillator interacts with incident photon and fast neutron radiations and is covered with a gadolinium converter to become thermal neutron-sensitive as well. In the meantime, an identical compensation scintillator, covered with terbium, solely interacts with the photon and fast neutron part of incident radiations. After the acquisition and the treatment of the counting signals from both sensors, a hypothesis test determines whether the resulting count rate after subtraction falls into statistical fluctuations or provides a robust image of neutron activity. A laboratory prototype is tested under both photon and neutron radiations, allowing us to investigate the performance of the overall compensation system. The study reveals satisfactory results in terms of robustness to a cesium-137 background and in terms of sensitivity in presence of a californium-252 source.

  12. Self-compensation in semiconductors

    NASA Astrophysics Data System (ADS)

    Tsur, Y.; Riess, I.

    1999-09-01

    The problem of self-compensation of charged dopants is analyzed. Special emphasis is given to dopants in binary oxides. It is shown that one can determine the degree of self-compensation from the properties of the host material and dopant concentration alone. It is further shown that for a native p-type semiconductor, donors are compensated, mostly, by native ionic defects. On the other hand, doping with acceptors allows us to increase significantly the hole concentration, i.e., self-compensation is low under high doping levels. For a native n-type semiconductor the opposite is true, namely, extrinsic acceptors are mainly compensated by native ionic defects. It is shown that the changes in concentration of all the charged defects are simply related by a single factor, the doping factor f, or its power fk where k depends solely on the defect's charge. Quantitative calculations of f and defect concentrations are presented for Cu2O, which was used as a model material. It is found that for p-type Cu2O doping with donors results in f within the range of 1-10, depending on the dopant concentration and P(O2). This means that the hole concentration decreases and the electron concentration increases at most by a factor of 10. Therefore one does not expect to obtain a changeover from p- to n-type cuprous oxide by doping, under equilibrium conditions. Most of the donors are compensated by negative ionic defects. Self-compensation in the presence of amphoteric defects and Fermi level stabilization are discussed, using the former formalism.

  13. 29 CFR 525.6 - Compensable time.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...

  14. 29 CFR 525.6 - Compensable time.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...

  15. 48 CFR 752.7007 - Personnel compensation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Personnel compensation... Personnel compensation. The following clause shall be used in all USAID cost-reimbursement contracts. Personnel Compensation (JUL 2007) (a) Direct compensation of the Contractor's personnel will be...

  16. 38 CFR 3.459 - Death compensation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Death compensation. 3.459 Section 3.459 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION Pension, Compensation, and Dependency and Indemnity Compensation Apportionments § 3.459 Death compensation. (a)...

  17. 29 CFR 525.6 - Compensable time.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...

  18. 38 CFR 3.459 - Death compensation.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Death compensation. 3.459 Section 3.459 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION Pension, Compensation, and Dependency and Indemnity Compensation Apportionments § 3.459 Death compensation. (a)...

  19. 38 CFR 3.459 - Death compensation.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Death compensation. 3.459 Section 3.459 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION Pension, Compensation, and Dependency and Indemnity Compensation Apportionments § 3.459 Death compensation. (a)...

  20. 38 CFR 3.459 - Death compensation.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Death compensation. 3.459 Section 3.459 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION Pension, Compensation, and Dependency and Indemnity Compensation Apportionments § 3.459 Death compensation. (a)...

  1. 38 CFR 3.459 - Death compensation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Death compensation. 3.459 Section 3.459 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION Pension, Compensation, and Dependency and Indemnity Compensation Apportionments § 3.459 Death compensation. (a)...

  2. 48 CFR 970.2270 - Unemployment compensation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...

  3. 48 CFR 970.2270 - Unemployment compensation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...

  4. 48 CFR 970.2270 - Unemployment compensation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...

  5. 48 CFR 970.2270 - Unemployment compensation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...

  6. 48 CFR 970.2270 - Unemployment compensation.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Unemployment compensation... Unemployment compensation. (a) Each state has its own unemployment compensation system to provide payments to... unemployment compensation benefits through a payroll tax on employers. Most DOE contractors are subject to...

  7. 29 CFR 525.6 - Compensable time.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...

  8. 29 CFR 525.6 - Compensable time.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 3 2014-07-01 2014-07-01 false Compensable time. 525.6 Section 525.6 Labor Regulations... WITH DISABILITIES UNDER SPECIAL CERTIFICATES § 525.6 Compensable time. Individuals employed subject to this part must be compensated for all hours worked. Compensable time includes not only those...

  9. Strip silicon waveguide for code synchronization in all-optical analog-to-digital conversion based on a lumped time-delay compensation scheme

    NASA Astrophysics Data System (ADS)

    Sha, Li; Zhi-Guo, Shi; Zhe, Kang; Chong-Xiu, Yu; Jian-Ping, Wang

    2016-04-01

    An all-optical analog-to-digital converter (ADC) based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integration. In this paper, a lumped time-delay compensation scheme with 2-bit quantization resolution is proposed. A strip silicon waveguide is designed and used to compensate for the entire time-delays of the optical pulses after a soliton self-frequency shift (SSFS) module within a wavelength range of 1550 nm–1580 nm. A dispersion coefficient as high as –19800 ps/(km·nm) with ±0.5 ps/(km·nm) variation is predicted for the strip waveguide. The simulation results show that the maximum supportable sampling rate (MSSR) is 50.45 GSa/s with full width at half maximum (FWHM) variation less than 2.52 ps, along with the 2-bit effective-number-of-bit and Gray code output. Project supported by the Fundamental Research Funds for the Central Universities, China (Grant No. FRF-TP-15-030A1) and China Postdoctoral Science Foundation (Grant No. 2015M580978).

  10. Photonic water dynamically responsive to external stimuli.

    PubMed

    Sano, Koki; Kim, Youn Soo; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Aida, Takuzo

    2016-01-01

    Fluids that contain ordered nanostructures with periodic distances in the visible-wavelength range, anomalously exhibit structural colours that can be rapidly modulated by external stimuli. Indeed, some fish can dynamically change colour by modulating the periodic distance of crystalline guanine sheets cofacially oriented in their fluid cytoplasm. Here we report that a dilute aqueous colloidal dispersion of negatively charged titanate nanosheets exhibits structural colours. In this 'photonic water', the nanosheets spontaneously adopt a cofacial geometry with an ultralong periodic distance of up to 675 nm due to a strong electrostatic repulsion. Consequently, the photonic water can even reflect near-infrared light up to 1,750 nm. The structural colour becomes more vivid in a magnetic flux that induces monodomain structural ordering of the colloidal dispersion. The reflective colour of the photonic water can be modulated over the entire visible region in response to appropriate physical or chemical stimuli. PMID:27572806

  11. Optimal focusing for maximal collection of entangled narrow-band photon pairs into single-mode fibers

    SciTech Connect

    Ljunggren, Daniel; Tengner, Maria

    2005-12-15

    We present a theoretical and experimental investigation of the emission characteristics and the flux of photon pairs generated by spontaneous parametric downconversion in quasi-phase matched bulk crystals for the use in quantum communication sources. We show that, by careful design, one can attain well defined modes close to the fundamental mode of optical fibers and obtain high coupling efficiencies also for bulk crystals, these being more easily aligned than crystal waveguides. We distinguish between singles coupling, {gamma}{sub s} and {gamma}{sub i}, conditional coincidence, {mu}{sub i|s}, and pair coupling, {gamma}{sub c}, and show how each of these parameters can be maximized by varying the focusing of the pump mode and the fiber-matched modes using standard optical elements. Specifically we analyze a periodically poled KTP-crystal pumped by a 532 nm laser creating photon pairs at 810 nm and 1550 nm. Numerical calculations lead to coupling efficiencies above 93% at optimal focusing, which is found by the geometrical relation L/z{sub R} to be {approx_equal}1 to 2 for the pump mode and {approx_equal}2 to 3 for the fiber-modes, where L is the crystal length and z{sub R} is the Rayleigh-range of the mode-profile. These results are independent on L. By showing that the single-mode bandwidth decreases {proportional_to}1/L, we can therefore design the source to produce and couple narrow bandwidth photon pairs well into the fibers. Smaller bandwidth means both less chromatic dispersion for long propagation distances in fibers, and that telecom Bragg gratings can be utilized to compensate for broadened photon packets--a vital problem for time-multiplexed qubits. Longer crystals also yield an increase in fiber photon flux {proportional_to}{radical}(L), and so, assuming correct focusing, we can only see advantages using long crystals.

  12. Feasibility study of proton-based quality assurance of proton range compensator

    NASA Astrophysics Data System (ADS)

    Park, S.; Jeong, C.; Min, B. J.; Kwak, J.; Lee, J.; Cho, S.; Shin, D.; Lim, Y. K.; Park, S. Y.; Lee, S. B.

    2013-06-01

    All patient specific range compensators (RCs) are customized for achieving distal dose conformity of target volume in passively scattered proton therapy. Compensators are milled precisely using a computerized machine. In proton therapy, precision of the compensator is critical and quality assurance (QA) is required to protect normal tissues and organs from radiation damage. This study aims to evaluate the precision of proton-based quality assurance of range compensator. First, the geometry information of two compensators was extracted from the DICOM Radiotherapy (RT) plan. Next, RCs were irradiated on the EBT film individually by proton beam which is modulated to have a photon-like percent depth dose (PDD). Step phantoms were also irradiated on the EBT film to generate calibration curve which indicates relationship between optical density of irradiated film and perpendicular depth of compensator. Comparisons were made using the mean absolute difference (MAD) between coordinate information from DICOM RT and converted depth information from the EBT film. MAD over the whole region was 1.7, and 2.0 mm. However, MAD over the relatively flat regions on each compensator selected for comparison was within 1 mm. These results shows that proton-based quality assurance of range compensator is feasible and it is expected to achieve MAD over the whole region less than 1 mm with further correction about scattering effect of proton imaging.

  13. An ultra large negative dispersion regular octagonal PCF with liquid infiltration

    NASA Astrophysics Data System (ADS)

    Kong, Xiangmin; Li, Xinlu; Jiang, Xingfang; Tang, Bin

    2015-10-01

    For solving the problem of dispersion in fiber communication, this article designed a ultra large negative dispersion regular octagonal PCF with liquid infiltration. The effects of air-hole diameter (d), layer-to-layer spacing (Λ) and refractive index of the infiltrating liquid (nL) on dispersion have been obtained based on Finite Element Method (FEM) by using COMSOL Multiphysics. The results show that with an increase of nL, the dispersion gets blue-shifted and the negative dispersion will increase. However, with the increase of Λ, the dispersion is red-shifted and the negative dispersion will reduce. Again, with the increase of d, the dispersion is red-shifted but with an augment of negative dispersion. This paper's theoretical study shows a high negative dispersion of -13000ps/(nm·km) around 1550nm when d=1.000μm, Λ=1.500μm and nL=1.374. The Dispersion Compensating Fiber (DCF) can effectively compensate the single mode fiber G. 652, which has been widely used. One meter the DCF can compensate 650 meters G. 652.

  14. Energy response improvement for photon dosimetry using pulse analysis

    NASA Astrophysics Data System (ADS)

    Zaki, Dizaji H.

    2016-02-01

    During the last few years, active personal dosimeters have been developed and have replaced passive personal dosimeters in some external monitoring systems, frequently using silicon diode detectors. Incident photons interact with the constituents of the diode detector and produce electrons. These photon-induced electrons deposit energy in the detector's sensitive region and contribute to the response of diode detectors. To achieve an appropriate photon dosimetry response, the detectors are usually covered by a metallic layer with an optimum thickness. The metallic cover acts as an energy compensating shield. In this paper, a software process is performed for energy compensation. Selective data sampling based on pulse height is used to determine the photon dose equivalent. This method is applied to improve the energy response in photon dosimetry. The detector design is optimized for the response function and determination of the photon dose equivalent. Photon personal dose equivalent is determined in the energy range of 0.3-6 MeV. The error values of the calculated data for this wide energy range and measured data for 133Ba, 137Cs, 60Co and 241Am-Be sources respectively are up to 20% and 15%. Fairly good agreement is seen between simulation and dose values obtained from our process and specifications from several photon sources.

  15. Compensation, radiographic changes, and survival in applicants for asbestosis compensation.

    PubMed Central

    Cookson, W O; Musk, A W; Glancy, J J; de Klerk, N H; Yin, R; Mele, R; Carr, N G; Armstrong, B K; Hobbs, M S

    1985-01-01

    The survival of 354 claimants for compensation for pulmonary asbestosis among former workers of the Wittenoom crocidolite mine and mill in Western Australia has been examined. There were 118 deaths up to December 1982. The median time between start of work and claim for compensation was 17 years. The standardised mortality ratio (SMR) for deaths from all causes was 2.65 (p less than 0.0001). The SMR for pneumoconiosis was 177.2 (p less than 0.0001), bronchitis and emphysema 2.6 (p = 0.04), tuberculosis 44.6 (p less than 0.0001), respiratory cancer (including five deaths from malignant pleural mesothelioma) 6.4 (p less than 0.0001), gastrointestinal cancer 1.6 (p = 0.22), all other cancers 1.6 (p = 0.17), heart disease 1.4 (p = 0.07), and all other causes 2.18 (p = 0.004). Plain chest radiographs taken within two years of claiming compensation were found for 238 subjects and were categorised independently by two observers according to the International Labour Organisation criteria without knowledge of exposure or compensation details. Profusion of radiographic opacities, age at claiming compensation, work in the Wittenoom mill, and degree of disability awarded by the pneumoconiosis medical board were significant predictors of survival, but total estimated exposure to asbestos was not. Radiographic profusion and degree of disability were, however, predictable by total exposure. The median survival from claim for compensation was 17 years in subjects with ILO category 1 pneumoconiosis, 12 years in category 2, and three years in category 3. PMID:2990524

  16. EMITTANCE COMPENSATION FOR MAGNETIZED BEAMS

    SciTech Connect

    KEWISCH,J.; CHANG, X.

    2007-06-25

    Emittance compensation is a well established technique for minimizing the emittance of an electron beam from a RF photo-cathode gun. Longitudinal slices of a bunch have a small emittance, but due to the longitudinal charge distribution of the bunch and time dependent RF fields they are not focused in the same way, so that the direction of their phase ellipses diverges in phase space and the projected emittance is much larger. Emittance compensation reverses the divergence. At the location where the slopes of the phase ellipses coincide the beam is accelerated, so that the space charge forces are reduced. A recipe for emittance compensation is given in. For magnetized beams (where the angular momentum is non-zero) such emittance compensation is not sufficient because variations in the slice radius lead to variations in the angular speed and therefore to an increase of emittance in the rotating game. We describe a method and tools for a compensation that includes the beam magnetization.

  17. Wide-band acousto-optic deflectors for large field of view two-photon microscope.

    PubMed

    Jiang, Runhua; Zhou, Zhenqiao; Lv, Xiaohua; Zeng, Shaoqun

    2012-04-01

    Acousto-optic deflector (AOD) is an attractive scanner for two-photon microscopy because it can provide fast and versatile laser scanning and does not involve any mechanical movements. However, due to the small scan range of available AOD, the field of view (FOV) of the AOD-based microscope is typically smaller than that of the conventional galvanometer-based microscope. Here, we developed a novel wide-band AOD to enlarge the scan angle. Considering the maximum acceptable acoustic attenuation in the acousto-optic crystal, relatively lower operating frequencies and moderate aperture were adopted. The custom AOD was able to provide 60 MHz 3-dB bandwidth and 80% peak diffraction efficiency at 840 nm wavelength. Based on a pair of such AOD, a large FOV two-photon microscope was built with a FOV up to 418.5 μm (40× objective). The spatiotemporal dispersion was compensated simultaneously with a single custom-made prism. By means of dynamic power modulation, the variation of laser intensity within the FOV was reduced below 5%. The lateral and axial resolution of the system were 0.58-2.12 μm and 2.17-3.07 μm, respectively. Pollen grain images acquired by this system were presented to demonstrate the imaging capability at different positions across the entire FOV. PMID:22559541

  18. Photonic-assisted microwave frequency multiplication with a tunable multiplication factor.

    PubMed

    Gao, Liang; Liu, Weilin; Chen, Xiangfei; Yao, Jianping

    2013-11-01

    Photonic-assisted microwave frequency multiplication with a tunable multiplication factor (MF) based on an optical comb generator and an embedded single-passband microwave photonic filter (MPF) is proposed and demonstrated. The optical comb is generated using two cascaded modulators which are driven by a microwave reference signal. By applying the optical comb to a photodetector, a fundamental frequency corresponding to the comb spacing and its harmonics is generated. Thanks to the embedded single-passband MPF, only one harmonic is selected by the single-passband MPF. Thus, a single-frequency frequency-multiplied microwave signal is generated. In the proposed system, the embedded single-passband MPF is formed by using a sliced broadband optical source and a section of dispersion-compensating fiber (DCF). By tuning the central frequency of the passband at a frequency corresponding to that of a specific harmonic, a microwave signal at that specific frequency is generated. The proposed system is experimentally demonstrated. A frequency-multiplied microwave signal with an MF from 1 to 5 is generated. The phase noise and frequency tunability of the generated microwave signal are also investigated. PMID:24177126

  19. A hollow waveguide Bragg reflector: A tunable platform for integrated photonics

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh

    2015-01-01

    Hollow waveguides are promising candidates for applications in sensing and high-power transmission. Flexible design and cost effective fabrication of hollow waveguides make it possible to realize integrated devices with small temperature dependence, tight control on optical confinement and tailorable characteristics. One of the potential applications of hollow waveguide is a tunable Bragg reflector, which can be used as building block for integrated photonics. In this review, integrated tunable Bragg reflector based on hollow-core optical waveguide is reviewed and presented; this Bragg reflector offers variable characteristics and design flexibility for applications in reconfigurable integrated photonic devices and circuits. Variety of tunable optical functions can be realized with on-chip Bragg reflector based on hollow waveguide, few of them are discussed in this review. Ultra-wide tuning in Bragg wavelength and on-chip polarization control can be realized using 3D hollow waveguide. A tapered 3D hollow waveguide Bragg reflector for an adjustable compensation of polarization mode dispersion (PMD) is then discussed. The utilization of a high-index contrast grating in hollow waveguide is demonstrated to reduce the polarization dependence and reflection-bandwidth. The polarization- and bandwidth control may be useful for realizing polarization insensitive devices and semiconductor lasers with ultra-wide tuning.

  20. Tevatron direct photon results.

    SciTech Connect

    Kuhlmann, S.

    1999-09-21

    Tevatron direct photon results since DIS98 are reviewed. Two new CDF measurements are discussed, the Run Ib inclusive photon cross section and the photon + Muon cross section. Comparisons with the latest NLO QCD calculations are presented.

  1. Resonance formation in photon-photon collisions

    SciTech Connect

    Gidal, G.

    1988-08-01

    Recent experimental progress on resonance formation in photon-photon collisions is reviewed with particular emphasis on the pseudoscalar and tensor nonents and on the ..gamma gamma..* production of spin-one resonances. 37 refs., 17 figs., 5 tabs.

  2. Physics at high energy photon photon colliders

    SciTech Connect

    Chanowitz, M.S.

    1994-06-01

    I review the physic prospects for high energy photon photon colliders, emphasizing results presented at the LBL Gamma Gamma Collider Workshop. Advantages and difficulties are reported for studies of QCD, the electroweak gauge sector, supersymmetry, and electroweak symmetry breaking.

  3. Compensation for electrical converter nonlinearities

    SciTech Connect

    Perisic, Milun; Ransom, Ray M; Kajouke, Lateef A

    2013-11-19

    Systems and methods are provided for delivering energy from an input interface to an output interface. An electrical system includes an input interface, an output interface, an energy conversion module between the input interface and the output interface, an inductive element between the input interface and the energy conversion module, and a control module. The control module determines a compensated duty cycle control value for operating the energy conversion module to produce a desired voltage at the output interface and operates the energy conversion module to deliver energy to the output interface with a duty cycle that is influenced by the compensated duty cycle control value. The compensated duty cycle control value is influenced by the current through the inductive element and accounts for voltage across the switching elements of the energy conversion module.

  4. Compensation and Recovery From Injury

    PubMed Central

    Beals, Rodney K.

    1984-01-01

    Workers' compensation laws influence recovery from injury. They affect the “cause” of disease, access to care, diagnostic evaluation, treatment, response to treatment and residual disability. Paradoxically, financial compensation may discourage return to work, the appeal process may increase disability, an open claim may inhibit return to work and recovering patients may be unable to return to work. Physicians may help improve the prospects of returning patients to work by providing care that is medical, caring and independent. It is essential that the treatment of back pain be based on the known natural history and on the understanding that the management of acute pain differs from that of chronic pain. Increased awareness of the factors controlling return to work should motivate legislative bodies, labor and industry to alter those features of the compensation system that interfere with the return to work of injured workers. PMID:6233794

  5. Simulation of selective passive compensation

    SciTech Connect

    Spikings, C.R.; Putley, D. )

    1991-01-01

    Compulsators have attracted a great deal of interest over the last few years as a way of providing repetitive high current millisecond pulses. The compulsator stores energy in a rotational form and works on a similar principle to a conventional alternator except that its internal impedance is reduced through compensating currents allowing greater currents to be drawn. This paper presents the theory behind selective passive compensation and presents some results from the computer simulation of a railgun powered by a selective passive compulsator. These results show that compulsator can be configured to produce flat topped current pulses into a railgun load. A test compulsator with active compensation has previously been designed and built by Culham Laboratory.

  6. Photonic compressive sensing with a micro-ring-resonator-based microwave photonic filter

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Ding, Yunhong; Zhu, Zhijing; Chi, Hao; Zheng, Shilie; Zhang, Xianmin; Jin, Xiaofeng; Galili, Michael; Yu, Xianbin

    2016-08-01

    A novel approach to realize photonic compressive sensing (CS) with a multi-tap microwave photonic filter is proposed and demonstrated. The system takes both advantages of CS and photonics to capture wideband sparse signals with sub-Nyquist sampling rate. The low-pass filtering function required in the CS is realized in a photonic way by using a frequency comb and a dispersive element. The frequency comb is realized by shaping an amplified spontaneous emission (ASE) source with an on-chip micro-ring resonator, which is beneficial to the integration of photonic CS. A proof-of-concept experiment for a two-tone signal acquisition with frequencies of 350 MHz and 1.25 GHz is experimentally demonstrated with a compression factor up to 16.

  7. Hyperentangled photon sources in semiconductor waveguides

    NASA Astrophysics Data System (ADS)

    Kang, Dongpeng; Helt, L. G.; Zhukovsky, Sergei V.; Torres, Juan P.; Sipe, J. E.; Helmy, A. S.

    2014-02-01

    We propose and analyze the performance of a technique to generate mode and polarization hyperentangled photons in monolithic semiconductor waveguides using two concurrent type-II spontaneous parametric down-conversion (SPDC) processes. These two SPDC processes are achieved by waveguide engineering which allows for simultaneous modal phase matching with the pump beam in a higher-order mode. Paired photons generated in each process are cross polarized and guided by different guiding mechanisms, which produces entanglement in both polarization and spatial mode. Theoretical analysis shows that the output quantum state has a high quality of hyperentanglement by spectral filtering with a bandwidth of a few nanometers, while off-chip compensation is not needed. This technique offers a path to realize an electrically pumped hyperentangled photon source.

  8. Network compensation for missing sensors

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert J., Jr.; Mulligan, Jeffrey B.

    1991-01-01

    A network learning translation invariance algorithm to compute interpolation functions is presented. This algorithm with one fixed receptive field can construct a linear transformation compensating for gain changes, sensor position jitter, and sensor loss when there are enough remaining sensors to adequately sample the input images. However, when the images are undersampled and complete compensation is not possible, the algorithm need to be modified. For moderate sensor losses, the algorithm works if the transformation weight adjustment is restricted to the weights to output units affected by the loss.

  9. Polarization compensator for optical communications

    NASA Technical Reports Server (NTRS)

    Fitzmaurice, M. W.; Abshire, J. B. (Inventor)

    1976-01-01

    An optical data communication system is provided whereby two orthogonal polarization states of a light beam carrier correspond to digital states. In such a system, automatic polarization compensation is provided by applying a dither modulating voltage to a cell exhibiting the electro-optic effect. The cell controls the relative phase of electric field components of an input light beam enabling the dither frequency component of the difference of the instantaneous powers in the two polarization states to be coherently detected. A signal derived from the coherent detection process is fed back to the cell via an integrator to form polarization bias compensating servo loop ot Type 1.

  10. Microwave photonic filter with multiple independently tunable passbands based on a broadband optical source.

    PubMed

    Huang, Long; Chen, Dalei; Zhang, Fangzheng; Xiang, Peng; Zhang, Tingting; Wang, Peng; Lu, Linlin; Pu, Tao; Chen, Xiangfei

    2015-10-01

    In this paper, a novel microwave photonic filter (MPF) with multiple independently tunable passbands is proposed. A broadband optical source (BOS) is employed and split by a 1:N coupler into several branches. One branch is directed to a phase modulator which is modulated by a radio frequency signal and the other branches are delayed by optical delay lines (ODLs), respectively. All of these branches are combined by another 1:N coupler and sent to a dispersion compensation fiber which is used to introduce group delay dispersion to the optical signal. At a photodetector, each time-delayed broadband lightwave beating with the sidebands produced by the phase modulator forms a passband of the MPF. By tuning the delay of each broadband lightwave, the center frequency of the passband can be independently tuned. An MPF with two independently tunable passbands is experimentally demonstrated. The two passbands can be tuned from DC to 30 GHz with a 3-dB bandwidth of about 250 MHz. The stability and dynamic range of the MPF are also evaluated. By employing more branches delayed by ODLs, more passbands can be generated. PMID:26480071

  11. An optically tunable wideband optoelectronic oscillator based on a bandpass microwave photonic filter.

    PubMed

    Jiang, Fan; Wong, Jia Haur; Lam, Huy Quoc; Zhou, Junqiang; Aditya, Sheel; Lim, Peng Huei; Lee, Kenneth Eng Kian; Shum, Perry Ping; Zhang, Xinliang

    2013-07-15

    An optoelectronic oscillator (OEO) with wideband frequency tunability and stable output based on a bandpass microwave photonic filter (MPF) has been proposed and experimentally demonstrated. Realized by cascading a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter together, the tunable bandpass MPF successfully replaces the narrowband electrical bandpass filter in a conventional single-loop OEO and serves as the oscillating frequency selector. The FIR filter is based on a tunable multi-wavelength laser and dispersion compensation fiber (DCF) while the IIR filter is simply based on an optical loop. Utilizing a long length of DCF as the dispersion medium for the FIR filter also provides a long delay line for the OEO feedback cavity and as a result, optical tuning over a wide frequency range can be achieved without sacrificing the quality of the generated signal. By tuning the wavelength spacing of the multi-wavelength laser, the oscillation frequency can be tuned from 6.88 GHz to 12.79 GHz with an average step-size of 0.128 GHz. The maximum frequency drift of the generated 10 GHz signal is observed to be 1.923 kHz over 1 hour and its phase noise reaches the -112 dBc/Hz limit of our measuring equipment at 10 kHz offset frequency. PMID:23938489

  12. Attenuation compensation in mesh-domain OSEM SPECT reconstruction

    NASA Astrophysics Data System (ADS)

    Vogelsang, Levon; Lu, Yao; Yu, Bo; Krol, Andrzej; Xu, Yuesheng; Hu, Xiaofei; Feiglin, David; Lipson, Edward

    2009-02-01

    A new method for attenuation compensation (AC) in mesh-domain SPECT OSEM reconstruction using strip-area approximation (SAAC) is introduced and compared to single-ray AC (SRAC). SAAC uses the polygonal area of the intersection of a mesh element (ME) and a tube-of-response (TOR) for defining an effective length of photon transit and an effective attenuation coefficient. This approach to AC is compared to SRAC, which defines the effective length of photon transit as the intersection of a single ray and a ME and the effective attenuation coefficient as the mean along the ray path. Comparative quantitative and qualitative analysis demonstrated that SAAC outperformed SRAC in terms of reconstruction image accuracy and quality.

  13. Lectures on Dispersion Theory

    DOE R&D Accomplishments Database

    Salam, A.

    1956-04-01

    Lectures with mathematical analysis are given on Dispersion Theory and Causality and Dispersion Relations for Pion-nucleon Scattering. The appendix includes the S-matrix in terms of Heisenberg Operators. (F. S.)

  14. Extended-Range Ultrarefractive 1D Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    A proposal has been made to exploit the special wavelength-dispersive characteristics of devices of the type described in One-Dimensional Photonic Crystal Superprisms (NPO-30232) NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 10a. A photonic crystal is an optical component that has a periodic structure comprising two dielectric materials with high dielectric contrast (e.g., a semiconductor and air), with geometrical feature sizes comparable to or smaller than light wavelengths of interest. Experimental superprisms have been realized as photonic crystals having three-dimensional (3D) structures comprising regions of amorphous Si alternating with regions of SiO2, fabricated in a complex process that included sputtering. A photonic crystal of the type to be exploited according to the present proposal is said to be one-dimensional (1D) because its contrasting dielectric materials would be stacked in parallel planar layers; in other words, there would be spatial periodicity in one dimension only. The processes of designing and fabricating 1D photonic crystal superprisms would be simpler and, hence, would cost less than do those for 3D photonic crystal superprisms. As in 3D structures, 1D photonic crystals may be used in applications such as wavelength-division multiplexing. In the extended-range configuration, it is also suitable for spectrometry applications. As an engineered structure or artificially engineered material, a photonic crystal can exhibit optical properties not commonly found in natural substances. Prior research had revealed several classes of photonic crystal structures for which the propagation of electromagnetic radiation is forbidden in certain frequency ranges, denoted photonic bandgaps. It had also been found that in narrow frequency bands just outside the photonic bandgaps, the angular wavelength dispersion of electromagnetic waves propagating in photonic crystal superprisms is much stronger than is the angular wavelength dispersion obtained

  15. Exclusive photon-photon processes

    SciTech Connect

    Brodsky, S.J.

    1997-07-01

    Exclusive gamma gamma right arrow hadron pairs are among the most fundamental processes in QCD, providing a detailed examination of Compton scattering in the crossed channel. In the high momentum transfer domain (s, t, large, Theta cm for t/s fixed), these processes can be computed from first principles in QCD, yielding important information on the nature of the QCD coupling data and the form of hadron distribution amplitudes. Similarly, the transition form factors gamma star gamma, gamma star gamma right arrow pi(o), Eta (0), Eta`, Eta(c)... provide rigorous tests of QCD and definitive determinations of the meson distribution amplitudes Phi H(x,Q). We show that the assumption of a frozen coupling at low momentum transfers can explain the observed scaling of two-photon exclusive processes.

  16. Few-photon transport in low-dimensional systems

    SciTech Connect

    Longo, Paolo; Schmitteckert, Peter; Busch, Kurt

    2011-06-15

    We analyze the role of quantum interference effects induced by an embedded two-level system on the photon transport properties in waveguiding structures that exhibit cutoffs (band edges) in their dispersion relation. In particular, we demonstrate that these systems invariably exhibit single-particle photon-atom bound states and strong effective nonlinear responses on the few-photon level. Based on this, we find that the properties of these photon-atom bound states may be tuned via the underlying dispersion relation and that their occupation can be controlled via multiparticle scattering processes. This opens an interesting route for controlling photon transport properties in a number of solid-state-based quantum optical systems and the realization of corresponding functional elements and devices.

  17. Analysis of measured photon returns from sodium beacons

    SciTech Connect

    Milonni, P.W.; Fugate, R.Q.; Telle, J.M.

    1998-01-01

    We describe an approach to the computation of photon returns from mesospheric sodium beacons excited by laser pulse trains and discuss as specific examples the required numbers of photons for adaptive-optical compensation of atmospheric turbulence. Computed photon return signals are compared with reported measurements for pulses that are long, short, or comparable to the D{sub 2} radiative lifetime (16 ns). Analytical approximations in good agreement with the numerical computations are derived. The results are consistent with experimental data for the different pulse durations. {copyright} 1998 Optical Society of America

  18. Dispersion y dinamica poblacional

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  19. Photon-Photon Interactions via Rydberg Blockade

    SciTech Connect

    Gorshkov, Alexey V.; Otterbach, Johannes; Fleischhauer, Michael; Pohl, Thomas; Lukin, Mikhail D.

    2011-09-23

    We develop the theory of light propagation under the conditions of electromagnetically induced transparency in systems involving strongly interacting Rydberg states. Taking into account the quantum nature and the spatial propagation of light, we analyze interactions involving few-photon pulses. We show that this system can be used for the generation of nonclassical states of light including trains of single photons with an avoided volume between them, for implementing photon-photon gates, as well as for studying many-body phenomena with strongly correlated photons.

  20. Photonic crystal surface-emitting lasers enabled by an accidental Dirac point

    SciTech Connect

    Chua, Song Liang; Lu, Ling; Soljacic, Marin

    2014-12-02

    A photonic-crystal surface-emitting laser (PCSEL) includes a gain medium electromagnetically coupled to a photonic crystal whose energy band structure exhibits a Dirac cone of linear dispersion at the center of the photonic crystal's Brillouin zone. This Dirac cone's vertex is called a Dirac point; because it is at the Brillouin zone center, it is called an accidental Dirac point. Tuning the photonic crystal's band structure (e.g., by changing the photonic crystal's dimensions or refractive index) to exhibit an accidental Dirac point increases the photonic crystal's mode spacing by orders of magnitudes and reduces or eliminates the photonic crystal's distributed in-plane feedback. Thus, the photonic crystal can act as a resonator that supports single-mode output from the PCSEL over a larger area than is possible with conventional PCSELs, which have quadratic band edge dispersion. Because output power generally scales with output area, this increase in output area results in higher possible output powers.

  1. Ultranegative angular dispersion of diffraction in quasiordered biophotonic structures.

    PubMed

    Liu, Feng; Dong, Biqin; Zhao, Fangyuan; Hu, Xinhua; Liu, Xiaohan; Zi, Jian

    2011-04-11

    We report that a three-dimensional quasiordered photonic structure, found in the cuticles of beetle H. sexmaculata, can diffract light in a "wrong" way and its angular dispersion is about one order of magnitude larger than that of a conventional diffraction grating. A new diffraction type of photonic bandgap (from an anticrossing of longitudinal and transverse modes) and additional disorder effect are found to play important roles in this phenomenon. Mimicking the structure could lead to novel optical devices with ultralarge angular dispersion. PMID:21503085

  2. Testing multistage gain and offset trimming in a single photon counting IC with a charge sharing elimination algorithm

    NASA Astrophysics Data System (ADS)

    Krzyżanowska, A.; Gryboś, P.; Szczygieł, R.; Maj, P.

    2015-12-01

    Designing a hybrid pixel detector readout electronics operating in a single photon counting mode is a very challenging process, where many main parameters are optimized in parallel (e.g. gain, noise, and threshold dispersion). Additional requirements for a smaller pixel size with extended functionality push designers to use new deep sub-micron technologies. Minimizing the channel size is possible, however, with a decreased pixel size, the charge sharing effect becomes a more important issue. To overcome this problem, we designed an integrated circuit prototype produced in CMOS 40 nm technology, which has an extended functionality of a single pixel. A C8P1 algorithm for the charge sharing effect compensation was implemented. In the algorithm's first stage the charge is rebuilt in a signal rebuilt hub fed by the CSA (charge sensitive amplifier) outputs from four neighbouring pixels. Then, the pixel with the biggest amount of charge is chosen, after a comparison with all the adjacent ones. In order to process the data in such a complicated way, a certain architecture of a single channel was proposed, which allows for: ṡ processing the signal with the possibility of total charge reconstruction (by connecting with the adjacent pixels), ṡ a comparison of certain pixel amplitude to its 8 neighbours, ṡ the extended testability of each block inside the channel to measure CSA gain dispersion, shaper gain dispersion, threshold dispersion (including the simultaneous generation of different pulse amplitudes from different pixels), ṡ trimming all the necessary blocks for proper operation. We present a solution for multistage gain and offset trimming implemented in the IC prototype. It allows for minimization of the total charge extraction errors, minimization of threshold dispersion in the pixel matrix and minimization of errors of comparison of certain pixel pulse amplitudes with all its neighbours. The detailed architecture of a single channel is presented together

  3. New Ideas in Educational Compensation.

    ERIC Educational Resources Information Center

    Rhodes, Eric; Kaplan, Harold

    This report suggests some possibilities open to school boards for improving compensation methods and presents some new avenues of exploration and study for boards wishing to pursue such possibilities. Subjects covered in the report include (1) the concept of accountability, (2) differentiated staffing, (3) merit pay plans, (4) performance…

  4. Can Education Compensate for Society?

    ERIC Educational Resources Information Center

    Pring, Richard

    2011-01-01

    The extent to which education can compensate for social disadvantage is a matter of political controversy, especially in the context of policies for social mobility. On the one hand, to blame poor achievement on social class or poverty was seen to dodge the professional responsibility of teachers. On the other, the strong correlation between…

  5. Concealing compensation from the IRS.

    PubMed

    Burda, D; Greene, J

    1991-01-28

    Tougher reporting requirements from the Internal Revenue Service are prompting some not-for-profit hospitals to seek ways to hide compensation arrangements from the public and the media. Critics believe those tactics could get hospitals in hot water with the law, especially now that the IRS has launched a new, aggressive auditing offensive. PMID:10108763

  6. Merit Compensation and Higher Education.

    ERIC Educational Resources Information Center

    Counelis, James Steve

    The concept of merit compensation is clarified from both administrative and faculty perspectives, and the conceptual sources of the controversy surrounding "merit" are addressed. Using the lexical tradition of the verb "to merit," four distinct semantic components are identified: to earn, to deserve, to value or give preference, and to obtain…

  7. 78 FR 28441 - Executive Compensation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-14

    ... level or range of compensation. \\11\\ For example, the financial crisis of 2008 caused Congress to enact...-- Interim Final Rule with Request for Comments, 73 FR 53356 (September 16, 2008), with Correcting Amendments at 73 FR 54309 (September 19, 2008) and 73 FR 54673 (September 23, 2008), codified at 12 CFR...

  8. Clarification of Workmen's Compensation Insurance.

    ERIC Educational Resources Information Center

    Shapley, Allen E.

    This document attempts to answer questions resulting from the 1972 Michigan Supreme Court Ruling relative to agricultural employees under the Workmen's Compensation Act (WCA). The sections of this paper outline a history of the WCA; employers covered; definition of "regularly employ"; clarification of "thirteen weeks"; employees (minors, partners,…

  9. CFO compensation reaches record levels.

    PubMed

    2001-06-01

    HFMA's 2001 CFO compensation survey finds that CFOs of hospitals and health systems are receiving higher compensation today than ever before. The current average compensation of $127,00--15.5 percent higher than was reported in a similar survey conducted in 1999--is the highest ever recorded by HFMA. Moreover, comparison of the 2001 findings with results of previous surveys shows that the earnings gains for CFOs over the past two years are stronger than they have been at many times in recent history. Factors that were found to influence CFO compensation in 2001 are location, years of service, number of employees reporting to the CFO, supervisory responsibility at the system versus hospital level, experience, and gender. Significant findings of the survey were that the average earnings of CFOs in urban areas are nearly twice those of CFOs in rural areas and that the average difference between earnings of male and female CFOs narrowed from $45,100 in 1999 to $36,800 in 2001. PMID:11407122

  10. Management Compensation: A Progress Report.

    ERIC Educational Resources Information Center

    Ramstad, Bill; And Others

    This examination of the current status of compensation for community college management and administrative personnel first summarizes the findings of a study conducted by Howard R. Bowen, which determined that, compared to business executives in comparable jobs within organizations of similar sizes, academic administrators were indeed underpaid.…

  11. Synchrony - Cyberknife Respiratory Compensation Technology

    SciTech Connect

    Ozhasoglu, Cihat Saw, Cheng B.; Chen Hungcheng; Burton, Steven; Komanduri, Krishna; Yue, Ning J.; Huq, Saiful M.; Heron, Dwight E.

    2008-07-01

    Studies of organs in the thorax and abdomen have shown that these organs can move as much as 40 mm due to respiratory motion. Without compensation for this motion during the course of external beam radiation therapy, the dose coverage to target may be compromised. On the other hand, if compensation of this motion is by expansion of the margin around the target, a significant volume of normal tissue may be unnecessarily irradiated. In hypofractionated regimens, the issue of respiratory compensation becomes an important factor and is critical in single-fraction extracranial radiosurgery applications. CyberKnife is an image-guided radiosurgery system that consists of a 6-MV LINAC mounted to a robotic arm coupled through a control loop to a digital diagnostic x-ray imaging system. The robotic arm can point the beam anywhere in space with 6 degrees of freedom, without being constrained to a conventional isocenter. The CyberKnife has been recently upgraded with a real-time respiratory tracking and compensation system called Synchrony. Using external markers in conjunction with diagnostic x-ray images, Synchrony helps guide the robotic arm to move the radiation beam in real time such that the beam always remains aligned with the target. With the aid of Synchrony, the tumor motion can be tracked in three-dimensional space, and the motion-induced dosimetric change to target can be minimized with a limited margin. The working principles, advantages, limitations, and our clinical experience with this new technology will be discussed.

  12. Compensation for oil pollution damage

    NASA Astrophysics Data System (ADS)

    Matugina, E. G.; Glyzina, T. S.; Kolbysheva, Yu V.; Klyuchnikov, A. S.; Vusovich, O. V.

    2015-11-01

    The commitment of national industries to traditional energy sources, as well as constantly growing energy demand combined with adverse environmental impact of petroleum production and transportation urge to establish and maintain an appropriate legal and administrative framework for oil pollution damage compensation. The article considers management strategies for petroleum companies that embrace not only production benefits but also environmental issues.

  13. Strategic Design of Teacher Compensation

    ERIC Educational Resources Information Center

    Shields, Regis

    2012-01-01

    Spurred by the national focus on revitalizing the teacher evaluation and support/development process, as well as the current economic downturn, many school districts are reviewing how teachers are compensated. While a few courageous districts have completely upended current structures, most districts are undertaking changes that leave the most…

  14. Annual Pay and Compensation Report.

    ERIC Educational Resources Information Center

    Vocino, Joe

    2003-01-01

    Presents results of the 2002 Human Resource Management Compensation Survey (n=1,084) indicating that salaries for training and development professionals increased only 1.8 percent over 2001. Tables depict salaries at various levels, by geographic area, and by industry. (JOW)

  15. Altitude Compensating Nozzle Concepts Evaluation

    NASA Technical Reports Server (NTRS)

    Soni, Bharat

    2000-01-01

    This report contains the summary of work accomplished during summer of 2000 by Mr. Chad Hammons, undergraduate senior student, Mississippi State University/ERC in support of NASA/MSFC mission pertinent to Altitude compensating nozzle concepts evaluations. In particular, the development of automatic grid generator applicable in conducting sensitivity analysis involving Aerospike engine is described.

  16. How to Treat Compensated Absences.

    ERIC Educational Resources Information Center

    Lewandowski, Raymond J.

    1986-01-01

    Discusses compensated absences such as future vacation, sick leave, and other absences that must be recognized for accounting and financial reporting purposes. Explains Governmental Accounting Standards Board distinctions between governmental and proprietary fund models. School districts and municipalities must now account for compensated…

  17. Theory of dispersive microlenses

    NASA Technical Reports Server (NTRS)

    Herman, B.; Gal, George

    1993-01-01

    A dispersive microlens is a miniature optical element which simultaneously focuses and disperses light. Arrays of dispersive mircolenses have potential applications in multicolor focal planes. They have a 100 percent optical fill factor and can focus light down to detectors of diffraction spot size, freeing up areas on the focal plane for on-chip analog signal processing. Use of dispersive microlenses allows inband color separation within a pixel and perfect scene registration. A dual-color separation has the potential for temperature discrimination. We discuss the design of dispersive microlenses and present sample results for efficient designs.

  18. Impact of fourth-order dispersion in the spectra of polarization-modulational instability in highly nonlinear fibers

    NASA Astrophysics Data System (ADS)

    Zambo Abou'ou, M. N.; Tchofo Dinda, P.; Ngabireng, C. M.; Pitois, S.; Kibler, B.

    2013-03-01

    We examine processes of polarization-modulational instability (PMI) in two categories of weakly birefringent optical fibers, namely, fibers whose nonlinearity is comparable to that of a standard telecom fiber, and high-index glass fibers whose nonlinearity is enhanced by several orders of magnitude as compared to that of a standard fiber. We show that the fourth-order dispersion (FOD) has a strong impact on PMI processes in both types of fibers, both at the qualitative and quantitative levels. At the qualitative level, the FOD enriches the phase diagram with nonconventional processes that generate two pairs of sidebands in certain parameter regions, while in other regions we obtain a single pair of sidebands whose frequency is independent of the pump power. The highly nonlinear birefringent fibers cause a pump depletion of a magnitude such that the frequency of the PMI sidebands becomes unstable and undergoes a continual drift. We demonstrate the existence of conditions in which the PMI process takes place in a manner similar to that of a process coupled with a photon reservoir, which feeds in situ the PMI process by continuously providing photons in compensation for those absorbed by the fiber.

  19. Electronic post-compensation of WDM transmission impairments using coherent detection and digital signal processing.

    PubMed

    Li, Xiaoxu; Chen, Xin; Goldfarb, Gilad; Mateo, Eduardo; Kim, Inwoong; Yaman, Fatih; Li, Guifang

    2008-01-21

    A universal post-compensation scheme for fiber impairments in wavelength-division multiplexing (WDM) systems is proposed based on coherent detection and digital signal processing (DSP). Transmission of 10 x 10 Gbit/s binary-phase-shift-keying (BPSK) signals at a channel spacing of 20 GHz over 800 km dispersion shifted fiber (DSF) has been demonstrated numerically. PMID:18542162

  20. Compensation of the volume charge of ions in a time-of-flight mass analyzer

    NASA Astrophysics Data System (ADS)

    Hashimov, A. M.; Nuruyev, K. Z.; Gurbanov, K. B.; Nurubeyli, Z. K.; Nurubeyli, T. K.

    2007-11-01

    A method of forced compensation of the volume charge of ions leading to considerable deterioration of the dispersion characteristics of a time-of-flight mass analyzer with a sector electrostatic field is described. It is shown that recompensation of the voluem charge also deteriorates the resolution of the instrument.

  1. Optimization of TE-TM mode converters on X-cut, Y-propagation LiNbO3 used for PMD compensation

    NASA Astrophysics Data System (ADS)

    Bhandare, S.; Noé, R.

    2001-10-01

    Two-phase and three-phase TE-TM mode converters for integrated optic polarization mode dispersion compensation are compared, and the latter are found to have a slightly better electro-optic efficiency. If a small differential group delay is needed, compensation performance can be drastically improved by a waveguide tilt in the YZ plane.

  2. Fast wavelength sweep in dispersion-tuned fiber laser using a chirped FBG and a reflective SOA for OCT applications

    NASA Astrophysics Data System (ADS)

    Takubo, Y.; Yamashita, S.

    2013-03-01

    We have demonstrated a wavelength-swept fiber laser based on dispersion tuning method. In this method, the light in a dispersive laser cavity is intensity modulated and actively mode-locked, and the lasing wavelength can be changed by controlling the modulation frequency. As the dispersion-tuned laser does not include any tunable filters, the sweep rate and range are not limited by mechanical moving parts. We have reported the wavelength-swept laser which has the tuning range of over 100nm with the sweep rate of 200kHz, and we have applied the laser to the swept-source optical coherence tomography (SS-OCT) system. Although we have successfully obtained the OCT image of the human finger at 1kHz sweep rate, we could not obtain OCT images at higher sweep rate because of the performance degradation of the laser. As this laser cavity included 100m long dispersion compensating fiber (DCF), the long laser cavity increased the photon lifetime and resulted in the output power decrease and the linewidth broadening at higher sweep rate. In order to solve these problems, we inserted a reflective semiconductor optical amplifier (RSOA) and a chirped fiber Bragg grating (CFBG) into the laser cavity. Use of these devices made it possible to shorten the cavity length drastically and the laser performance at high sweep rate is significantly improved. We could achieve that the sweep range of 60nm and the output power of 8.4mW at 100kHz sweep. We applied the laser to swept-source OCT system and we successfully obtained images of an adhesive tape at up to 250kHz sweep.

  3. Photonic band gaps in one-dimensional magnetized plasma photonic crystals with arbitrary magnetic declination

    SciTech Connect

    Zhang Haifeng; Liu Shaobin; Kong Xiangkun

    2012-12-15

    In this paper, the properties of photonic band gaps and dispersion relations of one-dimensional magnetized plasma photonic crystals composed of dielectric and magnetized plasma layers with arbitrary magnetic declination are theoretically investigated for TM polarized wave based on transfer matrix method. As TM wave propagates in one-dimensional magnetized plasma photonic crystals, the electromagnetic wave can be divided into two modes due to the influence of Lorentz force. The equations for effective dielectric functions of such two modes are theoretically deduced, and the transfer matrix equation and dispersion relations for TM wave are calculated. The influences of relative dielectric constant, plasma collision frequency, incidence angle, plasma filling factor, the angle between external magnetic field and +z axis, external magnetic field and plasma frequency on transmission, and dispersion relation are investigated, respectively, and some corresponding physical explanations are also given. From the numerical results, it has been shown that plasma collision frequency cannot change the locations of photonic band gaps for both modes, and also does not affect the reflection and transmission magnitudes. The characteristics of photonic band gaps for both modes can be obviously tuned by relative dielectric constant, incidence angle, plasma filling factor, the angle between external magnetic field and +z axis, external magnetic field and plasma frequency, respectively. These results would provide theoretical instructions for designing filters, microcavities, and fibers, etc.

  4. Adaptive optics two-photon scanning laser fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Yaopeng; Bifano, Thomas; Lin, Charles

    2011-03-01

    Two-photon fluorescence microscopy provides a powerful tool for deep tissue imaging. However, optical aberrations from illumination beam path limit imaging depth and resolution. Adaptive Optics (AO) is found to be useful to compensate for optical aberrations and improve image resolution and contrast from two-photon excitation. We have developed an AO system relying on a MEMS Deformable Mirror (DM) to compensate the optical aberrations in a two-photon scanning laser fluorescence microscope. The AO system utilized a Zernike polynomial based stochastic parallel gradient descent (SPGD) algorithm to optimize the DM shape for wavefront correction. The developed microscope is applied for subsurface imaging of mouse bone marrow. It was demonstrated that AO allows 80% increase in fluorescence signal intensity from bone cavities 145um below the surface. The AO-enhanced microscope provides cellular level images of mouse bone marrow at depths exceeding those achievable without AO.

  5. Effect of morphology and solvent on two-photon absorption of nano zinc oxide

    SciTech Connect

    Kavitha, M.K.; Haripadmam, P.C.; Gopinath, Pramod; Krishnan, Bindu; John, Honey

    2013-05-15

    Highlights: ► ZnO nanospheres and triangular structures synthesis by novel precipitation technique. ► The effect of precursor concentration on the size and shape of nano ZnO. ► Open aperture Z-scan measurements of the ZnO nanoparticle dispersions. ► Nanospheres exhibit higher two photon absorption coefficient than triangular nanostructures. ► Nanospheres dispersed in water exhibit higher two photon absorption coefficient than its dispersion in 2-propanol. - Abstract: In this paper, we report the effect of morphology and solvent on the two-photon absorption of nano zinc oxide. Zinc oxide nanoparticles in two different morphologies like nanospheres and triangular nanostructures are synthesized by novel precipitation technique and their two-photon absorption coefficient is measured using open aperture Z-scan technique. Experimental results show that the zinc oxide nanospheres exhibit higher two-photon absorption coefficient than the zinc oxide triangular nanostructures. The zinc oxide nanospheres dispersed in water exhibit higher two-photon absorption coefficient than that of its dispersion in 2-propanol. The zinc oxide nanospheres dispersed in water shows a decrease in two-photon absorption coefficient with an increase in on-axis irradiance. The result confirms the dependence of shape and solvent on the two-photon absorption of nano zinc oxide.

  6. The discrete-time compensated Kalman filter

    NASA Technical Reports Server (NTRS)

    Lee, W. H.; Athans, M.

    1978-01-01

    A suboptimal dynamic compensator to be used in conjunction with the ordinary discrete time Kalman filter was derived. The resultant compensated Kalman Filter has the property that steady state bias estimation errors, resulting from modelling errors, were eliminated.

  7. Temperature compensation for miniaturized magnetic sector

    NASA Technical Reports Server (NTRS)

    Sinha, Mahadeva P. (Inventor)

    2002-01-01

    Temperature compensation for a magnetic sector used in mass spectrometry. A high temperature dependant magnetic sector is used. This magnetic sector is compensated by a magnetic shunt that has opposite temperature characteristics to those of the magnet.

  8. 75 FR 22679 - Sound Incentive Compensation Guidance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-29

    ... incentive compensation practices in the banking industry by providing a common prudential foundation for incentive compensation arrangements across banking organizations and promoting the overall movement of the industry towards better practices. Supervisory action could play a critical role in addressing...

  9. 75 FR 76079 - Sound Incentive Compensation Guidance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-07

    ... incentive compensation practices in the banking industry by providing a common prudential foundation for incentive compensation arrangements across banking organizations and promoting the overall movement of the industry towards better practices. Supervisory action could play a critical role in addressing...

  10. 75 FR 53023 - Sound Incentive Compensation Guidance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-30

    ... incentive compensation practices in the banking industry by providing a common prudential foundation for incentive compensation arrangements across banking organizations and promoting the overall movement of the industry towards better practices. Supervisory action could play a critical role in addressing...

  11. Confinement effects on Brillouin scattering in semiconductor nanowire photonic crystal

    NASA Astrophysics Data System (ADS)

    Mante, Pierre-Adrien; Anttu, Nicklas; Zhang, Wei; Wallentin, Jesper; Chen, I.-Ju; Lehmann, Sebastian; Heurlin, Magnus; Borgström, Magnus T.; Pistol, Mats-Erik; Yartsev, Arkady

    2016-07-01

    Scattering of photons by phonons, or Brillouin scattering, enables manipulation and control of light and has led to revolutionary applications, from slow light to saser and cooling of micromechanical resonators. Recently, enhanced light and sound interaction has been demonstrated in waveguides. However, the design of the waveguide geometry tunes and alters the phonon and photon dispersion simultaneously. Here we investigate, through femtosecond pump-probe spectroscopy and theoretical modeling, the light and sound interaction in a bottom-up fabricated vertical nanowire photonic crystal. In such a system, the phonon dispersion can be tuned by varying the geometry of the constituent nanowires. In contrast, the placement of the nanowires in the photonic crystal can be used for tuning optical array modes, without altering the phonon dispersion. We demonstrate the forward and backward scattering, by acoustic phonons in the nanowires, of (1) such optical array modes and (2) guided modes of the constituent nanowires. Furthermore, our results reveal an enhanced interaction of array modes with phonons that we attribute to the specific scattering mechanism. Our results enable the design of a photonic crystal with separately tailored photon and phonon dispersion for Brillouin scattering. We anticipate these advances to be a starting point for enhanced control of light at the nanoscale.

  12. Compensation of dogleg effect in Fermilab Booster

    SciTech Connect

    Xiaobiao Huang; Sho Ohnuma

    2003-10-06

    The edge focusing of dogleg magnets in Fermilab Booster has been causing severe distortion to the horizontal linear optics. The doglegs are vertical rectangular bends, therefore the vertical edge focusing is canceled by body focusing and the overall effect is focusing in the horizontal plane. The maximum horizontal beta function is changed from 33.7m to 46.9m and maximum dispersion from 3.19m to 6.14m. Beam size increases accordingly. This is believed to be one of the major reasons of beam loss. In this technote we demonstrate that this effect can be effectively corrected with Booster's quadrupole correctors in short straight sections (QS). There are 24 QS correctors which can alter horizontal linear optics with negligible perturbation to the vertical plane. The currents of correctors are determined by harmonic compensation, i.e., cancellation of dogleg's harmonics that are responsible for the distortion with that of QS correctors. By considering a few leading harmonics, the ideal lattice can be partly restored. For the current dogleg layout, maximum {beta}{sub x} is reduced to 40.6m and maximum D{sub x} is reduced to 4.19m. This scheme can be useful after the dogleg in section No.3 is repositioned. In this case it can bring {beta}{sub x} from 40.9m down to 37.7m, D{sub x} from 4.57m to 4.01m.

  13. Luminescence properties of a Fibonacci photonic quasicrystal.

    PubMed

    Passias, V; Valappil, N V; Shi, Z; Deych, L; Lisyansky, A A; Menon, V M

    2009-04-13

    An active one-dimensional Fibonacci photonic quasi-crystal is realized via spin coating. Luminescence properties of an organic dye embedded in the quasi-crystal are studied experimentally and compared to theoretical simulations. The luminescence occurs via the pseudo-bandedge mode and follows the dispersion properties of the Fibonacci crystal. Time resolved luminescence measurement of the active structure shows faster spontaneous emission rate, indicating the effect of the large photon densities available at the bandedge due to the presence of critically localized states. The experimental results are in good agreement with the theoretical calculations for steady-state luminescence spectra. PMID:19365490

  14. Nuclear photonics

    SciTech Connect

    Habs, D.; Guenther, M. M.; Jentschel, M.; Thirolf, P. G.

    2012-07-09

    With the planned new {gamma}-beam facilities like MEGa-ray at LLNL (USA) or ELI-NP at Bucharest (Romania) with 10{sup 13}{gamma}/s and a band width of {Delta}E{gamma}/E{gamma} Almost-Equal-To 10{sup -3}, a new era of {gamma} beams with energies up to 20MeV comes into operation, compared to the present world-leading HI{gamma}S facility at Duke University (USA) with 10{sup 8}{gamma}/s and {Delta}E{gamma}/E{gamma} Almost-Equal-To 3 Dot-Operator 10{sup -2}. In the long run even a seeded quantum FEL for {gamma} beams may become possible, with much higher brilliance and spectral flux. At the same time new exciting possibilities open up for focused {gamma} beams. Here we describe a new experiment at the {gamma} beam of the ILL reactor (Grenoble, France), where we observed for the first time that the index of refraction for {gamma} beams is determined by virtual pair creation. Using a combination of refractive and reflective optics, efficient monochromators for {gamma} beams are being developed. Thus, we have to optimize the total system: the {gamma}-beam facility, the {gamma}-beam optics and {gamma} detectors. We can trade {gamma} intensity for band width, going down to {Delta}E{gamma}/E{gamma} Almost-Equal-To 10{sup -6} and address individual nuclear levels. The term 'nuclear photonics' stresses the importance of nuclear applications. We can address with {gamma}-beams individual nuclear isotopes and not just elements like with X-ray beams. Compared to X rays, {gamma} beams can penetrate much deeper into big samples like radioactive waste barrels, motors or batteries. We can perform tomography and microscopy studies by focusing down to {mu}m resolution using Nuclear Resonance Fluorescence (NRF) for detection with eV resolution and high spatial resolution at the same time. We discuss the dominating M1 and E1 excitations like the scissors mode, two-phonon quadrupole octupole excitations, pygmy dipole excitations or giant dipole excitations under the new facet of

  15. 16 CFR 16.16 - Compensation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 1 2013-01-01 2013-01-01 false Compensation. 16.16 Section 16.16 Commercial Practices FEDERAL TRADE COMMISSION ORGANIZATION, PROCEDURES AND RULES OF PRACTICE ADVISORY COMMITTEE MANAGEMENT § 16.16 Compensation. (a) Committee members. Unless otherwise provided by law, the Commission shall not compensate advisory...

  16. 12 CFR 7.2011 - Compensation plans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 1 2010-01-01 2010-01-01 false Compensation plans. 7.2011 Section 7.2011 Banks and Banking COMPTROLLER OF THE CURRENCY, DEPARTMENT OF THE TREASURY BANK ACTIVITIES AND OPERATIONS Corporate Practices § 7.2011 Compensation plans. Consistent with safe and sound banking practices and the compensation provisions of 12 CFR part 30,...

  17. 12 CFR 620.31 - Compensation committees.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Association Audit and Compensation Committees § 620.31 Compensation committees. Each Farm Credit bank and association must establish and maintain a compensation committee by adopting a written charter describing the committee's composition, authorities, and responsibilities in accordance with this section. All...

  18. Incentives, School Organization and Teacher Compensation.

    ERIC Educational Resources Information Center

    Odden, Allan

    In order for teacher compensation to serve as an incentive that reinforces broader organizational goals, the norms of the compensation structure must be aligned with the norms of the school organization. The first section of this paper presents a brief overview of changes in teacher compensation from 1820 to 1950. It describes how such changes…

  19. 14 CFR 158.53 - Collection compensation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Collection compensation. 158.53 Section 158...) AIRPORTS PASSENGER FACILITY CHARGES (PFC'S) Collection, Handling, and Remittance of PFC's § 158.53 Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue,...

  20. 14 CFR 158.53 - Collection compensation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Collection compensation. 158.53 Section 158...) AIRPORTS PASSENGER FACILITY CHARGES (PFC'S) Collection, Handling, and Remittance of PFC's § 158.53 Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue,...

  1. 14 CFR 158.53 - Collection compensation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Collection compensation. 158.53 Section 158...) AIRPORTS PASSENGER FACILITY CHARGES (PFC'S) Collection, Handling, and Remittance of PFC's § 158.53 Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue,...

  2. 14 CFR 158.53 - Collection compensation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Collection compensation. 158.53 Section 158...) AIRPORTS PASSENGER FACILITY CHARGES (PFC'S) Collection, Handling, and Remittance of PFC's § 158.53 Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue,...

  3. 14 CFR 158.53 - Collection compensation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Collection compensation. 158.53 Section 158...) AIRPORTS PASSENGER FACILITY CHARGES (PFC'S) Collection, Handling, and Remittance of PFC's § 158.53 Collection compensation. (a) As compensation for collecting, handling, and remitting the PFC revenue,...

  4. 16 CFR 1105.11 - Compensable costs.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Compensable costs. 1105.11 Section 1105.11... TO COSTS OF PARTICIPANTS IN DEVELOPMENT OF CONSUMER PRODUCT SAFETY STANDARDS § 1105.11 Compensable costs. The Commission may compensate participants for any or all of the following costs: (a)...

  5. 48 CFR 836.577 - Workers' compensation.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Workers' compensation. 836... CATEGORIES OF CONTRACTING CONSTRUCTION AND ARCHITECT-ENGINEER CONTRACTS Contract Clauses 836.577 Workers' compensation. The contracting officer shall insert the clause at 852.236-86, Workers' compensation,...

  6. 48 CFR 836.577 - Workers' compensation.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Workers' compensation. 836... CATEGORIES OF CONTRACTING CONSTRUCTION AND ARCHITECT-ENGINEER CONTRACTS Contract Clauses 836.577 Workers' compensation. The contracting officer shall insert the clause at 852.236-86, Workers' compensation,...

  7. 48 CFR 836.577 - Workers' compensation.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Workers' compensation. 836... CATEGORIES OF CONTRACTING CONSTRUCTION AND ARCHITECT-ENGINEER CONTRACTS Contract Clauses 836.577 Workers' compensation. The contracting officer shall insert the clause at 852.236-86, Workers' compensation,...

  8. 48 CFR 836.577 - Workers' compensation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Workers' compensation. 836... CATEGORIES OF CONTRACTING CONSTRUCTION AND ARCHITECT-ENGINEER CONTRACTS Contract Clauses 836.577 Workers' compensation. The contracting officer shall insert the clause at 852.236-86, Workers' compensation,...

  9. Coal workers' pneumoconiosis and compensation in Kentucky

    SciTech Connect

    Westerfield, B.T.

    1993-04-01

    Coal Workers' Pneumoconiosis has been a compensable disease since the 1960s. In 1987 the Kentucky Workers' Compensation Law was changed to provide reduced benefits for coal miners with radiographic evidence of Black Lung Disease, but little or no respiratory impairment. This paper reports a typical case of Black Lung today and discusses the status of workers' compensation for this disease in Kentucky.

  10. Causal compensated perturbations in cosmology

    NASA Technical Reports Server (NTRS)

    Veeraraghavan, Shoba; Stebbins, Albert

    1990-01-01

    A theoretical framework is developed to calculate linear perturbations in the gravitational and matter fields which arise causally in response to the presence of stiff matter sources in a FRW cosmology. It is shown that, in order to satisfy energy and momentum conservation, the gravitational fields of the source must be compensated by perturbations in the matter and gravitational fields, and the role of such compensation in containing the initial inhomogeneities in their subsequent evolution is discussed. A complete formal solution is derived in terms of Green functions for the perturbations produced by an arbitrary source in a flat universe containing cold dark matter. Approximate Green function solutions are derived for the late-time density perturbations and late-time gravitational waves in a universe containing a radiation fluid. A cosmological energy-momentum pseudotensor is defined to clarify the nature of energy and momentum conservation in the expanding universe.

  11. Compensated High Temperature Strain Gage

    NASA Technical Reports Server (NTRS)

    1994-01-01

    A device for measuring strain in substrates at high temperatures in which the thermally induced apparent strain is nulled is described. Two gages are used, one active gage and one compensating gage. Both gages are placed on the substrate to be gaged; the active gage is attached such that it responds to mechanical and thermally induced apparent strain while the compensating gage is attached such that it does not respond to mechanical strain and and measures only thermally induced apparent strain. A thermal blanket is placed over the two gages to maintain the gages at the same temperature. The two gages are wired as adjacent arms of a wheatstone bridge which nulls the thermally induced apparent strain giving a true reading of the mechanical strain in the substrate.

  12. Focus compensation techniques for reconnaissance

    NASA Technical Reports Server (NTRS)

    Mckeough, J.; Glavich, T.

    1979-01-01

    To maintain optimum resolution under varying environmental conditions, a focusing compensation system has been developed. The system is capable of detecting not only changes in pressure (altitude) and the general lens temperature but also the radial thermal gradients in the lens. Theoretical considerations show that the lens is most affected by these factors. The developed system uses a laser measurement system with environmental sensors to generate a focus correction for environment and range changes.

  13. Temperature compensated well logging tool

    SciTech Connect

    Riedesel, R.G.; Nussbaum, T.W.; Warren, W.F.

    1984-01-24

    A well logging tool adapted for use in a borehole traversing an earth formation includes at least one sensor sensing at least one characteristic of the earth formation. Another sensor senses the ambient temperature and provides a corresponding temperature signal. An output circuit provides a temperature compensated output signal corresponding to the sensed characteristic of the earth formation in accordance with the temperature signal and the characteristic signal.

  14. Is dispersal neutral?

    PubMed

    Lowe, Winsor H; McPeek, Mark A

    2014-08-01

    Dispersal is difficult to quantify and often treated as purely stochastic and extrinsically controlled. Consequently, there remains uncertainty about how individual traits mediate dispersal and its ecological effects. Addressing this uncertainty is crucial for distinguishing neutral versus non-neutral drivers of community assembly. Neutral theory assumes that dispersal is stochastic and equivalent among species. This assumption can be rejected on principle, but common research approaches tacitly support the 'neutral dispersal' assumption. Theory and empirical evidence that dispersal traits are under selection should be broadly integrated in community-level research, stimulating greater scrutiny of this assumption. A tighter empirical connection between the ecological and evolutionary forces that shape dispersal will enable richer understanding of this fundamental process and its role in community assembly. PMID:24962790

  15. 38 CFR 21.3023 - Nonduplication; pension, compensation, and dependency and indemnity compensation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2011-07-01 2011-07-01 false Nonduplication; pension, compensation, and dependency and indemnity compensation. 21.3023 Section 21.3023 Pensions, Bonuses, and... Nonduplication; pension, compensation, and dependency and indemnity compensation. (a) Child; age 18. A child...

  16. Strongly-Refractive One-Dimensional Photonic Crystal Prisms

    NASA Technical Reports Server (NTRS)

    Ting, David Z. (Inventor)

    2004-01-01

    One-dimensional (1D) photonic crystal prisms can separate a beam of polychromatic electromagnetic waves into constituent wavelength components and can utilize unconventional refraction properties for wavelength dispersion over significant portions of an entire photonic band rather than just near the band edges outside the photonic band gaps. Using a ID photonic crystal simplifies the design and fabrication process and allows the use of larger feature sizes. The prism geometry broadens the useful wavelength range, enables better optical transmission, and exhibits angular dependence on wavelength with reduced non-linearity. The properties of the 1 D photonic crystal prism can be tuned by varying design parameters such as incidence angle, exit surface angle, and layer widths. The ID photonic crystal prism can be fabricated in a planar process, and can be used as optical integrated circuit elements.

  17. Compensation Techniques in Accelerator Physics

    SciTech Connect

    Sayed, Hisham Kamal

    2011-05-01

    Accelerator physics is one of the most diverse multidisciplinary fields of physics, wherein the dynamics of particle beams is studied. It takes more than the understanding of basic electromagnetic interactions to be able to predict the beam dynamics, and to be able to develop new techniques to produce, maintain, and deliver high quality beams for different applications. In this work, some basic theory regarding particle beam dynamics in accelerators will be presented. This basic theory, along with applying state of the art techniques in beam dynamics will be used in this dissertation to study and solve accelerator physics problems. Two problems involving compensation are studied in the context of the MEIC (Medium Energy Electron Ion Collider) project at Jefferson Laboratory. Several chromaticity (the energy dependence of the particle tune) compensation methods are evaluated numerically and deployed in a figure eight ring designed for the electrons in the collider. Furthermore, transverse coupling optics have been developed to compensate the coupling introduced by the spin rotators in the MEIC electron ring design.

  18. Compensation of the Kerr effect for transient optomechanically induced transparency in a silica microsphere.

    PubMed

    Shen, Zhen; Dong, Chun-Hua; Chen, Yuan; Xiao, Yun-Feng; Sun, Fang-Wen; Guo, Guang-Can

    2016-03-15

    We have studied the Kerr effect in silica microspheres and demonstrated compensation of the Kerr effect for transient optomechanically induced transparency (OMIT). Due to the Kerr effect of the temporal strong driving pulse, an asymmetric transparency dip is observed during the transient OMIT experiment when the laser frequency is locked at one mechanical frequency, ω(m), below the whispering gallery mode resonance using a weak locking pulse. For compensation of the Kerr effect, we lock the laser at a lower frequency and show the symmetric transparency window. These results are important for studying photon-phonon interconversion, especially in systems with strong driving power. PMID:26977681

  19. Nonlinearity correction and dispersion analysis in FMCW laser radar

    NASA Astrophysics Data System (ADS)

    Zhao, Hao; Liu, Bingguo; Liu, Guodong; Chen, Fengdong; Zhuang, Zhitao; Yu, Yahui; Gan, Yu

    2014-12-01

    Frequency Modulated Continuous Wave laser radar is one of the most important ways to measure the large-size targets , combining the advantages of laser with conventional FMCW radar. Dispersion compensation and non-linear calibration are two key aspects in FMCW laser radar measurement. The paper studies the method of frequency-sampling to correct the Nonlinearity and analyzes the importance of dispersion compensation. We set up experimental verification platform, choose 1550nm band continuously tunable external cavity infrared laser as the light source, use all-fiber optical device structures, choose balanced detectors as photoelectric conversion, and finally acquire data with high speed PCI-E data acquisition card, write a measurement software with Labview. We measured the gage block 1 meter away. The experiment results show that the frequency sampling method correct the Nonlinearity well and there is a significant impact on the accuracy because of the fiber dispersion, dispersion must be compensated to obtain high accuracy. The experiment lays the foundation for further research on FMCW Laser radar.

  20. Dispersal of Disks Around Young Stars

    NASA Technical Reports Server (NTRS)

    Hollenbach, David; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    We review the evidence pertaining to the lifetimes of planet-forming disks and discuss possible disk dispersal mechanisms: 1) viscous accretion of material onto the central source; 2) close stellar encounters; 3) stellar winds; and 4) photoevaporation by ultraviolet radiation. We focus on 3) and 4) and describe the quasi-steady state appearance and the overall evolution of disks under the influence of winds and radiation from the central star and of radiation from external OB stars. Viscous accretion likely dominates disk dispersal in the inner disk (r approx. or less than 10 AU), while photoevaporation is the principal process of disk dispersal outside of r approx. or greater than 10 AU for low mass stars. Disk dispersal timescales are compared and discussed in relation to theoretical estimates for planet formation timescales. Photoevaporation may explain the large differences in the hydrogen content of the giant planets in the solar system. The commonly held belief that our early sun's stellar wind dispersed he solar nebula is called into question. Finally, we model the small bright objects ('proplyds') observed in the Orion Nebula as disks around young, low mass stars which are externally illuminated by the UV (ultraviolet) photons from the nearby massive star Theta(1)C.

  1. Dispersal of Disks Around Young Stars

    NASA Technical Reports Server (NTRS)

    Hollenbach, David

    2001-01-01

    We review the evidence pertaining to the lifetimes of planet-forming disks and discuss possible disk dispersal mechanisms: 1) viscous accretion of material onto the central source, 2) close stellar encounters, 3) stellar winds, and 4) photoevaporation by ultraviolet radiation. We focus on 3) and 4) and describe the quasi-steady state appearance and the overall evolution of disks under the influence of winds and radiation from the central star and of radiation from external OB stars. Viscous accretion likely dominates disk dispersal in the inner disk (r < or approx. equals 10 AU), while photoevaporation is the principal process of disk dispersal outside of r > or approx. equals 10 AU for low mass stars. Disk dispersal timescales are compared and discussed in relation to theoretical estimates for planet formation timescales. Photoevaporation may explain the large differences in the hydrogen content of the giant planets in the solar system. The commonly held belief that our early sun's stellar wind dispersed the solar nebula is called into question. Finally, we model the small bright objects ("proplyds") observed in the Orion Nebula as disks around young, low mass stars which are externally illuminated by the UV photons from the nearby massive star Theta(sup 1)C.

  2. Entanglement-based signature of nonlocal dispersion cancellation

    SciTech Connect

    Wasak, Tomasz; Szankowski, Piotr; Wasilewski, Wojciech; Banaszek, Konrad

    2010-11-15

    We derive an inequality bounding the strength of temporal correlations for a pair of light beams prepared in a separable state and propagating through dispersive media with opposite signs of group-velocity dispersion. The presented inequality can be violated by entangled states of light, such as photon pairs produced in spontaneous parametric down-conversion. Because the class of separable states covers the entire category of classical fields as a particular case, this result provides an unambiguously quantum feature of nonlocal dispersion cancellation that cannot be reproduced within the classical theory of electromagnetic radiation.

  3. Effect of implementation of a Bragg reflector in the photonic band structure of the Suzuki-phase photonic crystal lattice.

    PubMed

    Martinez, Luis Javier; Alija, Alfonso Rodriguez; Postigo, Pablo Aitor; Galisteo-López, J F; Galli, Matteo; Andreani, Lucio Claudio; Seassal, Christian; Viktorovitch, Pierre

    2008-06-01

    We investigate the change of the photonic band structure of the Suzuki-phase photonic crystal lattice when the horizontal mirror symmetry is broken by an underlying Bragg reflector. The structure consists of an InP photonic crystal slab including four InAsP quantum wells, a SiO(2) bonding layer, and a bottom high index contrast Si/SiO(2) Bragg mirror deposited on a Si wafer. Angle- and polarization-resolved photoluminescence spectroscopy has been used for measuring the photonic band structure and for investigating the coupling to a polarized plane wave in the far field. A drastic change in the k-space photonic dispersion between the structure with and without Bragg reflector is measured. An important enhancement on the photoluminescence emission up to seven times has been obtained for a nearly flat photonic band, which is characteristic of the Suzuki-phase lattice. PMID:18545565

  4. Study on Reactive Automatic Compensation System Design

    NASA Astrophysics Data System (ADS)

    Zhe, Sun; Qingyang, Liang; Peiqing, Luo; Chenfei, Zhang

    At present, low-voltage side of transformer is public in urban distribution network, as inductive load of household appliances is increasing, the power factor decreased, this lead to a large loss of public transformer low voltage side, the supply voltage indicators can not meet user's requirements. Therefore, the design of reactive power compensation system has become another popular research. This paper introduces the principle of reactive power compensation, analyzes key technologies of reactive power compensation, design an overall program of reactive power automatic compensation system to conquer various deficiencies of reactive power automatic compensation equipment.

  5. Quantum Computing using Photons

    NASA Astrophysics Data System (ADS)

    Elhalawany, Ahmed; Leuenberger, Michael

    2013-03-01

    In this work, we propose a theoretical model of two-quantum bit gates for quantum computation using the polarization states of two photons in a microcavity. By letting the two photons interact non-resonantly with four quantum dots inside the cavity, we obtain an effective photon-photon interaction which we exploit for the implementation of an universal XOR gate. The two-photon Hamiltonian is written in terms of the photons' total angular momentum operators and their states are written using the Schwinger representation of the total angular momentum.

  6. 78 FR 68867 - Division of Longshore and Harbor Workers' Compensation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-15

    ... of Workers' Compensation Programs Division of Longshore and Harbor Workers' Compensation Proposed... Office of Workers' Compensation (OWCP) is soliciting comments concerning the proposed collection...). SUPPLEMENTARY INFORMATION: I. Background: The Office of Workers' Compensation Programs, (OWCP) administers...

  7. Quantification of microcirculatory parameters by joint analysis of flow-compensated and non-flow-compensated intravoxel incoherent motion (IVIM) data.

    PubMed

    Ahlgren, André; Knutsson, Linda; Wirestam, Ronnie; Nilsson, Markus; Ståhlberg, Freddy; Topgaard, Daniel; Lasič, Samo

    2016-05-01

    The aim of this study was to improve the accuracy and precision of perfusion fraction and blood velocity dispersion estimates in intravoxel incoherent motion (IVIM) imaging, using joint analysis of flow-compensated and non-flow-compensated motion-encoded MRI data. A double diffusion encoding sequence capable of switching between flow-compensated and non-flow-compensated encoding modes was implemented. In vivo brain data were collected in eight healthy volunteers and processed using the joint analysis. Simulations were used to compare the performance of the proposed analysis method with conventional IVIM analysis. With flow compensation, strong rephasing was observed for the in vivo data, approximately cancelling the IVIM effect. The joint analysis yielded physiologically reasonable perfusion fraction maps. Estimated perfusion fractions were 2.43 ± 0.81% in gray matter, 1.81 ± 0.90% in deep gray matter, and 1.64 ± 0.72% in white matter (mean ± SD, n = 8). Simulations showed improved accuracy and precision when using joint analysis of flow-compensated and non-flow-compensated data, compared with conventional IVIM analysis. Double diffusion encoding with flow compensation was feasible for in vivo imaging of the perfusion fraction in the brain. The strong rephasing implied that blood flowing through the cerebral microvascular system was closer to the ballistic limit than the diffusive limit. © 2016 The Authors NMR in Biomedicine published by John Wiley & Sons Ltd. PMID:26952166

  8. Controllable photon source

    NASA Astrophysics Data System (ADS)

    Oszetzky, Dániel; Nagy, Attila; Czitrovszky, Aladár

    2006-10-01

    We have developed our pervious experimental setup using correlated photon pairs (to the calibration of photo detectors) to realize a controllable photon source. For the generation of such photon pairs we use the non-linear process of parametric down conversion. When a photon of the pump beam is incident to a nonlinear crystal with phase matching condition, a pair of photons (signal and idler) is created at the same time with certain probability. We detect the photons in the signal beam with a single photon counting module (SPCM), while delaying those in the idler beam. Recently we have developed a fast electronic unit to control an optical shutter (a Pockels cell) placed to the optical output of the idler beam. When we detect a signal photon with the controlling electronic unit we are also able to open or close the fast optical shutter. Thus we can control which idler photons can propagate through the Pockels cell. So with this photon source we are able to program the number of photons in a certain time window. This controllable photon source that is able to generate a known number of photons with specified wavelength, direction, and polarization could be useful for applications in high-accuracy optical characterisation of photometric devices at the ultra-low intensities. This light source can also serve as a standard in testing of optical image intensifiers, night vision devices, and in the accurate measurement of spectral distribution of transmission and absorption in optical materials.

  9. High energy photon-photon collisions

    SciTech Connect

    Brodsky, S.J.; Zerwas, P.M.

    1994-07-01

    The collisions of high energy photons produced at a electron-positron collider provide a comprehensive laboratory for testing QCD, electroweak interactions and extensions of the standard model. The luminosity and energy of the colliding photons produced by back-scattering laser beams is expected to be comparable to that of the primary e{sup +}e{sup {minus}} collisions. In this overview, we shall focus on tests of electroweak theory in photon-photon annihilation, particularly {gamma}{gamma} {yields} W{sup +}W{sup {minus}}, {gamma}{gamma} {yields} Higgs bosons, and higher-order loop processes, such as {gamma}{gamma} {yields} {gamma}{gamma}, Z{gamma} and ZZ. Since each photon can be resolved into a W{sup +}W{sup minus} pair, high energy photon-photon collisions can also provide a remarkably background-free laboratory for studying WW collisions and annihilation. We also review high energy {gamma}{gamma} tests of quantum chromodynamics, such as the scaling of the photon structure function, t{bar t} production, mini-jet processes, and diffractive reactions.

  10. Visualizing Dispersion Interactions

    ERIC Educational Resources Information Center

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  11. Spores Disperse, Too!

    ERIC Educational Resources Information Center

    Schumann, Donna N.

    1981-01-01

    Suggests the use of spores and spore-producing structures to show adaptations facilitating spore dispersal and dispersal to favorable environments. Describes several activities using horsetails, ferns, and mosses. Lists five safety factors related to use of mold spores in the classroom. (DS)

  12. Dispersion strengthened copper

    DOEpatents

    Sheinberg, H.; Meek, T.T.; Blake, R.D.

    1990-01-09

    A composition of matter is described which is comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide. A method for making this composition of matter is also described. This invention relates to the art of powder metallurgy and, more particularly, it relates to dispersion strengthened metals.

  13. Dispersal of forest insects

    NASA Technical Reports Server (NTRS)

    Mcmanus, M. L.

    1979-01-01

    Dispersal flights of selected species of forest insects which are associated with periodic outbreaks of pests that occur over large contiguous forested areas are discussed. Gypsy moths, spruce budworms, and forest tent caterpillars were studied for their massive migrations in forested areas. Results indicate that large dispersals into forested areas are due to the females, except in the case of the gypsy moth.

  14. A Column Dispersion Experiment.

    ERIC Educational Resources Information Center

    Corapcioglu, M. Y.; Koroglu, F.

    1982-01-01

    Crushed glass and a Rhodamine B solution are used in a one-dimensional optically scanned column experiment to study the dispersion phenomenon in porous media. Results indicate that the described model gave satisfactory results and that the dispersion process in this experiment is basically convective. (DC)

  15. Evolution of velocity dispersion along cold collisionless flows

    SciTech Connect

    Banik, Nilanjan; Sikivie, Pierre

    2015-11-17

    We found that the infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We also discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behaviour of the velocity dispersion near caustics. The results are used to derive an upper limit on the energy dispersion of the Big Flow from the sharpness of its nearby caustic, and a prediction for the dispersions in its velocity components.

  16. Evolution of velocity dispersion along cold collisionless flows

    NASA Astrophysics Data System (ADS)

    Banik, Nilanjan; Sikivie, Pierre

    2016-05-01

    The infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behavior of the velocity dispersion near caustics. The results are used to derive an upper limit on the energy dispersion of the big flow from the sharpness of its nearby caustic and a prediction for the dispersions in its velocity components.

  17. Evolution of velocity dispersion along cold collisionless flows

    DOE PAGESBeta

    Banik, Nilanjan; Sikivie, Pierre

    2016-05-01

    We found that the infall of cold dark matter onto a galaxy produces cold collisionless flows and caustics in its halo. If a signal is found in the cavity detector of dark matter axions, the flows will be readily apparent as peaks in the energy spectrum of photons from axion conversion, allowing the densities, velocity vectors and velocity dispersions of the flows to be determined. We also discuss the evolution of velocity dispersion along cold collisionless flows in one and two dimensions. A technique is presented for obtaining the leading behaviour of the velocity dispersion near caustics. The results aremore » used to derive an upper limit on the energy dispersion of the Big Flow from the sharpness of its nearby caustic, and a prediction for the dispersions in its velocity components.« less

  18. Photonic Design for Photovoltaics

    SciTech Connect

    Kosten, E.; Callahan, D.; Horowitz, K.; Pala, R.; Atwater, H.

    2014-08-28

    We describe photonic design approaches for silicon photovoltaics including i) trapezoidal broadband light trapping structures ii) broadband light trapping with photonic crystal superlattices iii) III-V/Si nanowire arrays designed for broadband light trapping.

  19. Photonic crystal light source

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Bur, James A.

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  20. Dispersion and space charge

    NASA Astrophysics Data System (ADS)

    Venturini, Marco; Kishek, Rami A.; Reiser, Martin

    1998-11-01

    The presence of space charge affects the value of the dispersion function. On the other hand dispersion has a role in shaping the beam distribution and therefore in determining the resulting forces due to space charge. In this paper we present a framework where the interplay between space charge and dispersion for a continuous beam can be simultaneously treated. We revise the derivation of a new set of rms envelope-dispersion equations we have recently proposed in [1]. The new equations generalize the standard rms envelope equations currently used for matching to the case where bends and a longitudinal momentum spread are present. We report a comparison between the solutions of the rms envelope-dispersion equations and the results obtained using WARP, a Particle in Cell (PIC) code, in the modeling of the Maryland Electron Ring.

  1. Compensating For GPS Ephemeris Error

    NASA Technical Reports Server (NTRS)

    Wu, Jiun-Tsong

    1992-01-01

    Method of computing position of user station receiving signals from Global Positioning System (GPS) of navigational satellites compensates for most of GPS ephemeris error. Present method enables user station to reduce error in its computed position substantially. User station must have access to two or more reference stations at precisely known positions several hundred kilometers apart and must be in neighborhood of reference stations. Based on fact that when GPS data used to compute baseline between reference station and user station, vector error in computed baseline is proportional ephemeris error and length of baseline.

  2. DC-Compensated Current Transformer.

    PubMed

    Ripka, Pavel; Draxler, Karel; Styblíková, Renata

    2016-01-01

    Instrument current transformers (CTs) measure AC currents. The DC component in the measured current can saturate the transformer and cause gross error. We use fluxgate detection and digital feedback compensation of the DC flux to suppress the overall error to 0.15%. This concept can be used not only for high-end CTs with a nanocrystalline core, but it also works for low-cost CTs with FeSi cores. The method described here allows simultaneous measurements of the DC current component. PMID:26805830

  3. Charge amplifier with bias compensation

    DOEpatents

    Johnson, Gary W.

    2002-01-01

    An ion beam uniformity monitor for very low beam currents using a high-sensitivity charge amplifier with bias compensation. The ion beam monitor is used to assess the uniformity of a raster-scanned ion beam, such as used in an ion implanter, and utilizes four Faraday cups placed in the geometric corners of the target area. Current from each cup is integrated with respect to time, thus measuring accumulated dose, or charge, in Coulombs. By comparing the dose at each corner, a qualitative assessment of ion beam uniformity is made possible. With knowledge of the relative area of the Faraday cups, the ion flux and areal dose can also be obtained.

  4. Compensation issues tough to navigate

    SciTech Connect

    Madison, Alison L.

    2012-02-12

    Monthly economic diversity column for the Tri-City Herald - excerpt pasted below: Most industries out there are feeling the shift to a more educated, thus more empowered consumer. The legal field is no exception, which is why it's no surprise that lawsuits are on the rise. Today's society is one in which people are more aware than ever of their rights, and often equally convinced of their entitlements in a number of areas. For business owners, employees represent a major source of potential lawsuits. And compensation is an area of particular concern given that many complaints against employers revolve around it in some way.

  5. Driver Compensation: Impairment or Improvement?

    PubMed

    Young, Richard A

    2015-12-01

    Strayer et al.'s conclusion that their "cognitive distraction scale" for auditory-vocal tasks indicates "significant impairments to driving" is not supported by their data. Additional analysis demonstrates that slower brake reaction times during auditory-vocal tasks were fully compensated for by longer following distances to the lead car. Naturalistic driving data demonstrate that cellular conversation decreases crash risk, the opposite of the article's assumption. Hence, the scale's internal and external validities for indicating driving impairment are highly questionable. PMID:26534851

  6. Photon and electron Landau damping in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.; Serbeto, A.

    2016-09-01

    Using a quantum kinetic description, we establish a general expression for the dispersion relation of electron plasma waves in the presence of an arbitrary spectrum of electromagnetic waves. This includes both electron and photon Landau damping. The quantum kinetic description allows us to compare directly these two distinct processes, and to show that they are indeed quite similar. The present work also extends previous results on photon Landau damping onto the quantum domain.

  7. Axion electrodynamics and nonrelativistic photons in nuclear and quark matter

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoki

    2016-04-01

    We argue that the effective theory for electromagnetic fields in spatially varying meson condensations in dense nuclear and quark matter is given by the axion electrodynamics. We show that one of the helicity states of photons there has the nonrelativistic gapless dispersion relation ω ˜k2 at small momentum, while the other is gapped. This "nonrelativistic photon" may also be realized at the interface between topological and trivial insulators in condensed matter systems.

  8. Ecological compensation in Dutch highway planning.

    PubMed

    Cuperus, R; Bakermans, M M; De Haes, H A; Canters, K J

    2001-01-01

    The ecological compensation principle was introduced by the Dutch government in 1993. This principle is designed to enhance the input of nature conservation interests in decision-making on large-scale development projects and to counterbalance the ecological impacts of such developments when implemented. This article evaluates the application of the Dutch compensation principle in highway planning. Six current highway projects reveal consistent implementation of this principle, although provincial policies on compensation and a national method for identifying compensation measures are still under development. As the planning process has not yet been completed for all the projects, no general conclusions can be drawn on the impact of the compensation principle on highway decision-making. Nevertheless, several examples show that the principle stimulates project initiators to develop alternative routes or route sections in order to avoid or reduce ecological impacts and the need for coherent compensation measures. If the compensation principle is to be properly implemented in the context of highway planning, particular attention should be paid to the following aspects: (1) sequential assessment of overall project legitimacy and the necessity of intersecting protected areas and compensation measures. (2) the initiator's attempts to avoid and mitigate ecological impacts in developing alternative routes prior to compensation for impacts, and (3) the role of uncertain ecological impacts in identifying compensation measures, especially those concerning habitat isolation. PMID:11083910

  9. Executive compensation in the multiaffiliate corporation.

    PubMed

    Browdy, J D

    1986-06-01

    Designing compensation programs for the growing number of multiaffiliate health care corporations is a complex task. Compensation structures should be based on responsibility, not organization affiliation, to avoid the perception that corporate-level positions are always worth more than affiliate-level ones. To accomplish this, administrators must identify characteristics shared by key corporate and affiliate positions, including having direct responsibility for implementing board policies and taking actions that directly affect the organization's viability. Position titles and salary structure should reflect similar responsibility levels. When analyzing salary surveys, administrators must determine affiliates' autonomy within the corporation; institutions with direct corporate supervision may have lower compensation levels than free-standing ones. Corporate executive compensation may emphasize fringe benefits rather than base salary; differentials here should also reflect position responsibility. Incentive awards, a growing factor in executive compensation, should be based on predetermined, quantifiable objectives. Awards may vary because corporate, affiliate, and proprietary executives have different goals. The responsibility for the organization's compensation program belongs to the corporate board. It can best discharge this responsibility through an executive compensation committee. The committee's duties include evaluating the CEO, establishing a compensation philosophy, ensuring consistency in program application, and integrating compensation with long-range plans. Committee members must be objective, recognize the organization's need for executive talent, have corporate experience, and view executive compensation in "global" rather than local terms. PMID:10276817

  10. Photonic analog of a van Hove singularity in metamaterials

    NASA Astrophysics Data System (ADS)

    Cortes, Cristian L.; Jacob, Zubin

    2013-07-01

    We introduce the photonic analog of electronic van Hove singularities (VHS) in artificial media (metamaterials) with hyperbolic dispersion. Unlike photonic and electronic crystals, the VHS in metamaterials are unrelated to the underlying periodicity and occur due to slow-light modes in the structure. We show that the VHS characteristics are manifested in the near-field local density of optical states in spite of the losses, dispersion, and finite unit-cell size of the hyperbolic metamaterial. Finally, we show that this work should lead to quantum, thermal, nanolasing, and biosensing applications of van Hove singularities in hyperbolic metamaterials achievable by current fabrication technology.

  11. An Efficient Adaptive Angle-Doppler Compensation Approach for Non-Sidelooking Airborne Radar STAP.

    PubMed

    Shen, Mingwei; Yu, Jia; Wu, Di; Zhu, Daiyin

    2015-01-01

    In this study, the effects of non-sidelooking airborne radar clutter dispersion on space-time adaptive processing (STAP) is considered, and an efficient adaptive angle-Doppler compensation (EAADC) approach is proposed to improve the clutter suppression performance. In order to reduce the computational complexity, the reduced-dimension sparse reconstruction (RDSR) technique is introduced into the angle-Doppler spectrum estimation to extract the required parameters for compensating the clutter spectral center misalignment. Simulation results to demonstrate the effectiveness of the proposed algorithm are presented. PMID:26053755

  12. Temperature sensitivity of photonic crystal fibers infiltrated with ethanol solutions

    NASA Astrophysics Data System (ADS)

    Chu Van, Lanh; Stefaniuk, Tomasz; Kasztelanic, Rafał; Cao Long, Van; Klimczak, Mariusz; Le Van, Hieu; Trippenbach, Marek; Buczyński, Ryszard

    2015-12-01

    In this paper we present a numerical study on the optimization of dispersion of a photonic crystal fiber infiltrated with water-ethanol mixtures. The advantage of such an approach stems from the fact that the dependence of the refractive index on temperature is larger in liquids than in solid materials. Here, we examine photonic crystal fibers with a regular, hexagonal lattice and with various geometrical and material parameters, such as different number of rings of holes, various lattice constants and the size of core and air-holes. Additionally, for the optimized structure with flat dispersion characteristics, we analyze the influence of temperature and concentration of the ethanol solution on the dispersion characteristic and the zero dispersion wavelength shift of the fundamental mode.

  13. Ideal optical backpropagation of scalar NLSE using dispersion-decreasing fibers for WDM transmission.

    PubMed

    Liang, Xiaojun; Kumar, Shiva; Shao, Jing

    2013-11-18

    An ideal optical backpropagation (OBP) scheme to compensate for dispersion and nonlinear effects of the transmission fibers is proposed. The scheme consists of an optical phase conjugator (OPC), N spans of dispersion-decreasing fibers (DDFs) and amplifiers, placed at the end of the fiber optic link. In order to compensate for the nonlinear effects of the transmission fibers exactly, the nonlinear coefficient of the backpropagation fiber has to increase exponentially with distance or equivalently the power in the backpropagation fiber should increase exponentially with distance if the nonlinear coefficient is constant. In this paper, it is shown that a combination of DDFs and amplifiers can compensate for the nonlinear effects exactly. An analytical expression for the dispersion profile of the DDF is derived. Numerical simulation of a long haul wavelength division multiplexing (WDM) fiber optic system with the proposed OBP scheme shows that the system reach can be enhanced by 54% as compared to digital backpropagation (DBP). PMID:24514378

  14. Risk compensation and bicycle helmets.

    PubMed

    Phillips, Ross Owen; Fyhri, Aslak; Sagberg, Fridulv

    2011-08-01

    This study investigated risk compensation by cyclists in response to bicycle helmet wearing by observing changes in cycling behavior, reported experience of risk, and a possible objective measure of experienced risk. The suitability of heart rate variability (HRV) as an objective measure of experienced risk was assessed beforehand by recording HRV measures in nine participants watching a thriller film. We observed a significant decrease in HRV in line with expected increases in psychological challenge presented by the film. HRV was then used along with cycling pace and self-reported risk in a field experiment in which 35 cyclist volunteers cycled 0.4 km downhill, once with and once without a helmet. Routine helmet users reported higher experienced risk and cycled slower when they did not wear their helmet in the experiment than when they did wear their helmet, although there was no corresponding change in HRV. For cyclists not accustomed to helmets, there were no changes in speed, perceived risk, or any other measures when cycling with versus without a helmet. The findings are consistent with the notion that those who use helmets routinely perceive reduced risk when wearing a helmet, and compensate by cycling faster. They thus give some support to those urging caution in the use of helmet laws. PMID:21418079

  15. Features of the long-wavelength impurity photoconductivity spectrum in compensated germanium

    SciTech Connect

    Druzhinin, Y.P.; Chirkova, E.G.

    1995-09-01

    This paper discusses the impurity photoconductivity spectra of compensated Ge: (Cu, Sb) in the photoheating regime, in which the photon energy is comparable to the scale of the random potential well, and the temperature is 4.2 K. Three sections are distinguished in the long-wavelength cutoff region, corresponding to different energy relaxation and charge-carrier transport mechanisms, including a mechanism that involves the participation of optical phonons. 6 refs., 1 fig.

  16. Infectious Diseases Physician Compensation: An Improved Perspective

    PubMed Central

    Ritter, Jethro Trees; Lynch, John B.; MacIntyre, Ann T.; Trotman, Robin

    2016-01-01

    Negotiating physician compensation can be complicated because many factors now influence the ways in which physicians can be compensated. Infectious diseases (ID) specialists typically provide a wide array of services, ranging from patient care to administrative leadership. Compensation surveys from national organizations have produced results based on small samples and often are not congruent with ID physicians’ perceptions. In July of 2015, the Infectious Diseases Society of America (IDSA) conducted a compensation survey to assess current compensation earned by the diverse ID specialists within its membership. Members of IDSA's Clinical Affairs Committee report the results from the 2015 IDSA Physician Compensation survey, with a particular focus on the findings from respondents who indicate “patient care” as their primary responsibility and present a discussion that compares and contrasts results against other survey data. PMID:27419159

  17. Pointing compensation system for spacecraft instruments

    NASA Technical Reports Server (NTRS)

    Plescia, Carl T. (Inventor); Gamble, Donald W. (Inventor)

    1987-01-01

    A closed loop system reduces pointing errors in one or more spacecraft instruments. Associated with each instrument is a electronics package (3) for commanding motion in that instrument and a pointing control system (5) for imparting motion in that instrument in response to a command (4) from the commanding package (3). Spacecraft motion compensation logic (25) compensates for instrument pointing errors caused by instrument-motion-induced spacecraft motion. Any finite number of instruments can be so compensated, by providing each pointing control system (5) and each commanding package (3), for the instruments desired to be compensated, with a link to the spacecraft motion compensation logic (25). The spacecraft motion compensation logic (25) is an electronic manifestation of the algebraic negative of a model of the dynamics of motion of the spacecraft. An example of a suitable model, and computer-simulated results, are presented.

  18. CEO Compensation and Hospital Financial Performance

    PubMed Central

    Reiter, Kristin L.; Sandoval, Guillermo A.; Brown, Adalsteinn D.; Pink, George H.

    2010-01-01

    Growing interest in pay-for-performance and the level of CEO pay raises questions about the link between performance and compensation in the health sector. This study compares the compensation of non-profit hospital Chief Executive Officers (CEOs) in Ontario, Canada to the three longest reported and most used measures of hospital financial performance. Our sample consisted of 132 CEOs from 92 hospitals between 1999 and 2006. Unbalanced panel data were analyzed using fixed effects regression. Results suggest that CEO compensation was largely unrelated to hospital financial performance. Inflation-adjusted salaries appeared to increase over time independent of hospital performance, and hospital size was positively correlated with CEO compensation. The apparent upward trend in salary despite some declines in financial performance challenges the fundamental assumption underlying this paper, that is, financial performance is likely linked to CEO compensation in Ontario. Further research is needed to understand long-term performance related to compensation incentives. PMID:19605619

  19. How to avoid deferred-compensation troubles.

    PubMed

    Freeman, Todd I

    2005-06-01

    Executive compensation packages have long included stock options and deferred compensation plans in order to compete for talent. Last year, Congress passed a law in response to the Enron debacle, in which executives were perceived to be protecting their deferred compensation at the expense of employees, creditors, and investors. The new law is designed to protect companies and their shareholders from being raided by the very executives that guided the company to financial ruin. Physicians who are part owners of medical practices need to know about the changes in the law regarding deferred compensation and how to avoid costly tax penalties. This article discusses how the changes affect medical practices as well as steps physician-owned clinics can take to avoid the risk of penalty, such as freezing deferred compensation and creating a new deferred compensation plan. PMID:16050311

  20. Entangled photon generation using four-wave mixing in azimuthally symmetric microresonators.

    PubMed

    Camacho, Ryan M

    2012-09-24

    A novel quantum mechanical formulation of the bi-photon wavefunction and spectra resulting from four-wave mixing is developed for azimuthally symmetric systems. Numerical calculations are performed verifying the use of the angular group velocity and angular group velocity dispersion in such systems, as opposed their commonly used linear counterparts. The dispersion profile and bi-photon spectra of two illustrative examples are given, emphasizing the physical origin of the effects leading to the conditions for angular momentum and energy conservation. A scheme is proposed in which widely spaced narrowband entangled photons may be produced through a four-wave mixing process in a chip-scale ring resonator. The entangled photon pairs are found to conserve energy and momentum in the four-wave mixing interaction, even though both photon modes lie in spectral regions of steep angular group velocity dispersion. PMID:23037348

  1. Nanostructured materials for photonics

    SciTech Connect

    Kumar, N.D.; Ruland, G.; Yoshida, M.; Lal, M.; Bhawalkar, J.; He, G.S.; Prasad, P.N.

    1996-12-31

    Nanocomposite materials for application in photonics were developed by sol-gel processing and reverse micellar microemulsion techniques. The capability of incorporating many materials with different functional properties in sol-gel processed glass matrices has been explored in making these materials. The large pore volume fraction and the enormous surface area of the sol-gel glasses enables one to introduce many materials in a phase separated fashion, where the phase separation is in the nanometer range. It is possible to introduce an active material on to the pore surface by solution infiltration and subsequent removal of the solvent, then filling the pores with a monomer containing another active material, and polymerizing inside the pores. Using this approach the authors have developed composite materials for optical power limiting applications at different wavelengths and a tunable solid state dye lasing medium. Optically transparent polyimide:TiO{sub 2} composite waveguide materials were prepared by the dispersion of nano-sized TiO{sub 2} particles into a polyimide matrix. The particles were produced through reverse micelles using the sol-gel method, and were incorporated into the fluorinated polyimide solution. A polyimide:TiO{sub 2} (4 wt%) composite waveguide was produced from the solution. Since the particle size is so small, no noticeable scattering loss was observed. The measured optical propagation loss at 633 nm was 1.4 dB/cm, which is equivalent to that of the pure polyimide. The refractive index was increased from 1.550 to 1.560 by the incorporation of TiO{sub 2}.

  2. Controllable photon bunching by atomic superpositions in a driven cavity

    NASA Astrophysics Data System (ADS)

    Guo, Weijie; Wang, Yao; Wei, L. F.

    2016-04-01

    We propose a feasible approach to generate the desired light with controllable photon bunchings by adjusting the atomic superpositions in a driven cavity. Under the large detuning limit, i.e., the cavity is far resonance with the inside atom(s), we show that the photons in the cavity are always bunchings. Typically, when the effective dispersive interaction equals the detuning between the driving and cavity fields, we find that the value of second-order correlation g(2 )(0 ) inverses to the probability of the superposed atomic state. This suggests that such a value could be arbitrarily large, and thus the bunchings of the photons could be significantly enhanced.

  3. Dispersion strengthened copper

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1990-01-01

    A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

  4. Dispersion strengthened copper

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1989-01-01

    A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

  5. Polarization-based compensation of astigmatism

    NASA Astrophysics Data System (ADS)

    Chowdhury, Dola Roy; Bhattacharya, Kallol; Chakraborty, Ajay K.; Ghosh, Raja

    2004-02-01

    One approach to aberration compensation of an imaging system is to introduce a suitable phase mask at the aperture plane of an imaging system. We utilize this principle for the compensation of astigmatism. A suitable polarization mask used on the aperture plane together with a polarizer-retarder combination at the input of the imaging system provides the compensating polarization-induced phase steps at different quadrants of the apertures masked by different polarizers. The aberrant phase can be considerably compensated by the proper choice of a polarization mask and suitable selection of the polarization parameters involved. The results presented here bear out our theoretical expectation.

  6. Undulator with dynamic compensation of magnetic forces

    DOEpatents

    Gluskin, Efim; Trakhtenberg, Emil; Xu, Joseph Z.

    2016-05-31

    A method and apparatus for implementing dynamic compensation of magnetic forces for undulators are provided. An undulator includes a respective set of magnet arrays, each attached to a strongback, and placed on horizontal slides and positioned parallel relative to each other with a predetermined gap. Magnetic forces are compensated by a set of compensation springs placed along the strongback. The compensation springs are conical springs having exponential-force characteristics that substantially match undulator magnetic forces independently of the predetermined gap. The conical springs are positioned along the length of the magnets.

  7. Lithium compensation for full cell operation

    DOEpatents

    Xiao, Jie; Zheng, Jianming; Chen, Xilin; Lu, Dongping; Liu, Jun; Jiguang, Jiguang

    2016-05-17

    Disclosed herein are embodiments of a lithium-ion battery system comprising an anode, an anode current collector, and a layer of lithium metal in contact with the current collector, but not in contact with the anode. The lithium compensation layer dissolves into the electrolyte to compensate for the loss of lithium ions during usage of the full cell. The specific placement of the lithium compensation layer, such that there is no direct physical contact between the lithium compensation layer and the anode, provides certain advantages.

  8. Log amplifier with pole-zero compensation

    DOEpatents

    Brookshier, W.

    1985-02-08

    A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifer circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedstock loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point is offset by a compensating break point or zero.

  9. Log amplifier with pole-zero compensation

    DOEpatents

    Brookshier, William

    1987-01-01

    A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifier circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedback loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point or pole is offset by a compensating break point or zero.

  10. Observation of localized flat-band modes in a quasi-one-dimensional photonic rhombic lattice.

    PubMed

    Mukherjee, Sebabrata; Thomson, Robert R

    2015-12-01

    We experimentally demonstrate the photonic realization of a dispersionless flat band in a quasi-one-dimensional photonic lattice fabricated by ultrafast laser inscription. In the nearest neighbor tight binding approximation, the lattice supports two dispersive and one nondispersive (flat) band. We experimentally excite superpositions of flat-band eigenmodes at the input of the photonic lattice and show the diffractionless propagation of the input states due to their infinite effective mass. In the future, the use of photonic rhombic lattices, together with the successful implementation of a synthetic gauge field, will enable the observation of Aharonov-Bohm photonic caging. PMID:26625021

  11. Tunable one-dimensional plasma photonic crystals in dielectric barrier discharge

    SciTech Connect

    Fan Weili; Dong Lifang

    2010-07-15

    A tunable one-dimensional plasma photonic crystal is obtained by using a dielectric barrier discharge with two liquid electrodes. It is formed by the self-organization of the filaments, rather than that in an artificial array of electrodes. The dispersion relations of the plasma photonic crystals are calculated by solving the Helmholtz equation using a method analogous to Kronig-Penney's problem. The photonic band diagrams of the plasma photonic crystals are studied when changing the filling factor, the lattice constant, and the electron density, based on the experimental results. The critical electron density is given, beyond which the plasma photonic crystal will have a remarkable band structure.

  12. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  13. Fickian dispersion is anomalous

    SciTech Connect

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  14. Fickian dispersion is anomalous

    DOE PAGESBeta

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion wemore » illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.« less

  15. Holonomic quantum computation on microwave photons with all resonant interactions

    NASA Astrophysics Data System (ADS)

    Dong, Ping; Yu, Long-Bao; Zhou, Jian

    2016-08-01

    The intrinsic difficulties of holonomic quantum computation on superconducting circuits are originated from the use of three levels in superconducting transmon qubits and the complicated dispersive interaction between them. Due to the limited anharmonicity of transmon qubits, the experimental realization seems to be very challenging. However, with recent experimental progress, coherent control over microwave photons in superconducting circuit cavities is well achieved, and thus provides a promising platform for quantum information processing with photonic qubits. Here, with all resonant inter-cavity photon–photon interactions, we propose a scheme for implementing scalable holonomic quantum computation on a circuit QED lattice. In our proposal, three cavities, connected by a SQUID, are used to encode a logical qubit. By tuning the inter-cavity photon–photon interaction, we can construct all the holonomies needed for universal quantum computation in a non-adiabatic way. Therefore, our scheme presents a promising alternative for robust quantum computation with microwave photons.

  16. EDITORIAL: Photonic materials on demand Photonic materials on demand

    NASA Astrophysics Data System (ADS)

    Zheludev, Nikolay; Padilla, Willie J.; Brener, Igal

    2012-11-01

    As David Payne famously said, 'we never have a photonic material that we want...'. This has changed with the proliferation of nanotechnology. Metamaterials—artificial media structured on a sub-wavelength scale—offer a radical paradigm for the engineering of optical properties. Some remarkable advances have been possible with metamaterials. These include, for instance, negative-index media that refract light in the opposite direction from that of conventional materials, chiral materials that rotate the polarization state of light hundreds of thousands of times more strongly than natural optical crystals, and structured thin films with remarkably strong dispersion that can slow light in much the same way as resonant atomic systems with electromagnetically induced transparency. The research agenda is now shifting towards achieving tunable and switchable functionalities with metamaterials [1] where the goal is, paraphrasing Dave Payne, 'to have on demand the photonic material that we want'. The papers in this Journal of Optics special issue explore and review the different approaches to both switching and tuning of metamaterial properties through exploiting effects such as phase conjugation, intense photo-excitation and photoconductivity, the use of electro-optical effects in conductive oxides, the exploitation global quantum coherency and resonantly coupled classical resonator and quantum structures, hybridization with gain media and the manipulation with shapes and constitution of the complex metamolecules and metamaterial reliefs by design, or using MEMS actuation. References [1] Zheludev N I and Kivshar Y 2012 From metamaterials to metadevices Nature Mater.11 917

  17. Self-compensating solenoid valve

    NASA Technical Reports Server (NTRS)

    Woeller, Fritz H. (Inventor); Matsumoto, Yutaka (Inventor)

    1987-01-01

    A solenoid valve is described in which both an inlet and an outlet of the valve are sealed when the valve is closed. This double seal compensates for leakage at either the inlet or the outlet by making the other seal more effective in response to the leakage and allows the reversal of the flow direction by simply switching the inlet and outlet connections. The solenoid valve has a valve chamber within the valve body. Inlet and outlet tubes extend through a plate into the chamber. A movable core in the chamber extends into the solenoid coil. The distal end of the core has a silicone rubber plug. Other than when the solenoid is energized, the compressed spring biases the core downward so that the surface of the plug is in sealing engagement with the ends of the tubes. A leak at either end increases the pressure in the chamber, resulting in increased sealing force of the plug.

  18. Compensating for cold war cancers.

    PubMed Central

    Parascandola, Mark J

    2002-01-01

    Although the Cold War has ended, thousands of workers involved in nuclear weapons production are still living with the adverse health effects of working with radioactive materials, beryllium, and silica. After a series of court battles, the U.S. government passed the Energy Employees Occupational Illness Act in October 2000 to financially assist workers whose health has been compromised by these occupational exposures. Now work is underway to set out guidelines for determining which workers will be compensated. The National Institute for Occupational Safety and Health has been assigned the task of developing a model that can scientifically make these determinations, a heavy task considering the controversies that lie in estimating low-level radiation risks and the inadequate worker exposure records kept at many of the plants. PMID:12117658

  19. 38 CFR 3.351 - Special monthly dependency and indemnity compensation, death compensation, pension and spouse's...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Special monthly dependency and indemnity compensation, death compensation, pension and spouse's compensation ratings. 3.351 Section 3.351 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION...

  20. 38 CFR 3.351 - Special monthly dependency and indemnity compensation, death compensation, pension and spouse's...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Special monthly dependency and indemnity compensation, death compensation, pension and spouse's compensation ratings. 3.351 Section 3.351 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS ADJUDICATION...